Aircraft impact on nuclear power plants concrete structures

International Nuclear Information System (INIS)

Coombs, R.F.; Barbosa, L.C.B.; Santos, S.H.C.

1980-01-01

A summary about the procedures for the analysis of aircraft on concrete structures, aiming to emphasize the aspects related to the nuclear power plants safety, is presented. The impact force is determined by the Riera model. The effect of this impact force on the concrete structures is presented, showing the advantages to use nonlinear behaviour in the concrete submitted to short loads. The simplifications used are shown through a verification example of the nuclear reactor concrete shielding. (E.G.) [pt

Finite element analysis of degraded concrete structures - Workshop proceedings

International Nuclear Information System (INIS)

1999-09-01

This workshop is related to the finite element analysis of degraded concrete structures. It is composed of three sessions. The first session (which title is: the use of finite element analysis in safety assessments) comprises six papers which titles are: Historical Development of Concrete Finite Element Modeling for Safety Evaluation of Accident-Challenged and Aging Concrete Structures; Experience with Finite Element Methods for Safety Assessments in Switzerland; Stress State Analysis of the Ignalina NPP Confinement System; Prestressed Containment: Behaviour when Concrete Cracking is Modelled; Application of FEA for Design and Support of NPP Containment in Russia; Verification Problems of Nuclear Installations Safety Software of Strength Analysis (NISS SA). The second session (title: concrete containment structures under accident loads) comprises seven papers which titles are: Two Application Examples of Concrete Containment Structures under Accident Load Conditions Using Finite Element Analysis; What Kind of Prediction for Leak rates for Nuclear Power Plant Containments in Accidental Conditions; Influence of Different Hypotheses Used in Numerical Models for Concrete At Elevated Temperatures on the Predicted Behaviour of NPP Core Catchers Under Severe Accident Conditions; Observations on the Constitutive Modeling of Concrete Under Multi-Axial States at Elevated Temperatures; Analyses of a Reinforced Concrete Containment with Liner Corrosion Damage; Program of Containment Concrete Control During Operation for the Temelin Nuclear Power Plant; Static Limit Load of a Deteriorated Hyperbolic Cooling Tower. The third session (concrete structures under extreme environmental load) comprised five papers which titles are: Shear Transfer Mechanism of RC Plates After Cracking; Seismic Back Calculation of an Auxiliary Building of the Nuclear Power Plant Muehleberg, Switzerland; Seismic Behaviour of Slightly Reinforced Shear Wall Structures; FE Analysis of Degraded Concrete

Report on aging of nuclear power plant reinforced concrete structures

International Nuclear Information System (INIS)

Naus, D.J.; Oland, C.B.; Ellingwood, B.R.

1996-03-01

The Structural Aging Program provides the US Nuclear Regulatory Commission with potential structural safety issues and acceptance criteria for use in continued service assessments of nuclear power plant safety-related concrete structures. The program was organized under four task areas: Program Management, Materials Property Data Base, Structural Component Assessment/Repair Technology, and Quantitative Methodology for Continued Service Determinations. Under these tasks, over 90 papers and reports were prepared addressing pertinent aspects associated with aging management of nuclear power plant reinforced concrete structures. Contained in this report is a summary of program results in the form of information related to longevity of nuclear power plant reinforced concrete structures, a Structural Materials Information Center presenting data and information on the time variation of concrete materials under the influence of environmental stressors and aging factors, in-service inspection and condition assessments techniques, repair materials and methods, evaluation of nuclear power plant reinforced concrete structures, and a reliability-based methodology for current and future condition assessments. Recommendations for future activities are also provided. 308 refs., 61 figs., 50 tabs

Report on aging of nuclear power plant reinforced concrete structures

Energy Technology Data Exchange (ETDEWEB)

Naus, D.J.; Oland, C.B. [Oak Ridge National Lab., TN (United States); Ellingwood, B.R. [Johns Hopkins Univ., Baltimore, MD (United States). Dept. of Civil Engineering

1996-03-01

The Structural Aging Program provides the US Nuclear Regulatory Commission with potential structural safety issues and acceptance criteria for use in continued service assessments of nuclear power plant safety-related concrete structures. The program was organized under four task areas: Program Management, Materials Property Data Base, Structural Component Assessment/Repair Technology, and Quantitative Methodology for Continued Service Determinations. Under these tasks, over 90 papers and reports were prepared addressing pertinent aspects associated with aging management of nuclear power plant reinforced concrete structures. Contained in this report is a summary of program results in the form of information related to longevity of nuclear power plant reinforced concrete structures, a Structural Materials Information Center presenting data and information on the time variation of concrete materials under the influence of environmental stressors and aging factors, in-service inspection and condition assessments techniques, repair materials and methods, evaluation of nuclear power plant reinforced concrete structures, and a reliability-based methodology for current and future condition assessments. Recommendations for future activities are also provided. 308 refs., 61 figs., 50 tabs.

Assessment and management of aging of nuclear power plant safety-related structures

International Nuclear Information System (INIS)

Naus, D.J.; Graves, H.L. III; Ellingwood, B.R.

2003-01-01

Background information and data have been developed for improving existing and developing new methods to assist in quantifying the effects of age-related degradation on the performance of nuclear power plant (NPP) safety-related structures. Factors that can lead to age-related degradation of safety-related structures are identified and their manifestations described. Current regulatory testing and inspection requirements are reviewed and a summary of degradation experience presented. Techniques commonly used to inspect NPP concrete structures to assess and quantify age-related degradation are summarized. An approach for conduct of condition assessments of structures in NPPs is presented. Criteria, based primarily on visual indications, are provided for use in classification and assessment of concrete degradation. Materials and techniques for repair of degraded structures are noted and guidance provided on repair options available for various forms of degradation. A probabilistic methodology for condition assessment and reliability-based life prediction has been developed and applied to structures subject to combinations of structural load processes and to structural systems. The methodology has also been used to investigate optimization of in-service inspection and maintenance strategies to maintain failure probability below a specified target value as well as to minimize costs. Fragility assessments involving analytical solutions and finite-element methods have been utilized to predict the effect of aging degradation on structural component performance. (author)

High-strength concrete and the design of power plant structures

International Nuclear Information System (INIS)

Puttonen, J.

1991-01-01

Based on the literature, the design of high-strength concrete structures and the suitability of high-strength concrete for the power plant structures have been studied. Concerning the behavior of structures, a basic difference between the high-strength concrete and the traditional one is that the ductility of the high-strength concrete is smaller. In the design, the non-linear stress-strain relationship of the high-strength concrete has to be taken into account. The use of the high-strength concrete is economical if the strength of the material can be utilized. In the long term, the good durability and wear resistance of the high-strength concrete increases the economy of the material. Because of the low permeability of the high-strength concrete, it is a potential material in the safety-related structures of nuclear power plants. The study discovered no particular power plant structure which would always be economical to design of high-strength concrete. However, the high-strength concrete was found to be a competitive material in general

Activities at ORNL in support of continuing the service of nuclear power plant concrete structures

International Nuclear Information System (INIS)

Naus, D.J.

2012-01-01

In general, nuclear power plant concrete structure's performance has been very good; however, aging of concrete structures occurs with the passage of time that can potentially result in degradation if its effects are not controlled. Safety-related nuclear power plant concrete structures are described. In-service inspection and testing requirements in the U.S. are summarized. The interaction of the license renewal process and concrete structures is noted. A summary of operating experience related to aging of nuclear power plant concrete structures is provided. Several candidate areas are identified where additional research would be beneficial for aging management of nuclear power plant concrete structures. Finally, an update on recent activities at Oak Ridge National Laboratory related to aging management of nuclear power plant concrete structures is provided. (author)

Aging of concrete containment structures in nuclear power plants

International Nuclear Information System (INIS)

Naus, D.J.; Oland, C.B.; Ellingwood, B.; Mori, Yasuhiro; Arndt, E.G.

1992-01-01

Concrete structures play a vital role in the safe operation of all light-water reactor plants in the US Pertinent concrete structures are described in terms of their importance design, considerations, and materials of construction. Degradation factors which can potentially impact the ability of these structures to meet their functional and performance requirements are identified. Current inservice inspection requirements for concrete containments are summarized. A review of the performance history of the concrete components in nuclear power plants is provided. A summary is presented. A summary is presented of the Structural Aging (SAG) Program being conducted at the Oak Ridge National Laboratory for the US Nuclear Regulatory Commission. The SAG Program is addressing the aging management of safety-related concrete structures in nuclear power plants for the purpose of providing improved bases for their continued service. The program consists of a management task and three technical tasks: materials property data base, structural component assessment/repair technologies, and quantitiative methodology for continued service conditions. Objectives and a summary of accomplishments under each of these tasks are presented

Concrete structures for nuclear facilities

International Nuclear Information System (INIS)

1996-01-01

The detailed requirements for the design and fabrication of the concrete structures for nuclear facilities and for the documents to be submitted to the Finnish Centre for Radiation and Nuclear Safety (STUK) are given in the guide. It also sets the requirements for the inspection of concrete structures during the construction and operation of facilities. The requirements of the guide primarily apply to new construction. As regards the repair and modification of nuclear facilities built before its publication, the guide is followed to the extent appropriate. The regulatory activities of the Finnish Centre for Radiation and Nuclear Safety during a nuclear facility's licence application review and during the construction and operation of the facility are summarised in the guide YVL 1.1

Dam safety investigations of the concrete structures of Hugh Keenleyside dam

International Nuclear Information System (INIS)

Hanna, A.W.; Nunn, J.O.H.; Cornish, L.; Northcott, P.

1993-01-01

The Hugh Keenleyside dam is located on the Columbia River in southeastern British Columbia, and impounds Arrow Lakes Reservoir which has a live storage of 8.8 km 3 and drains an area of 36,000 km 2 . It consists of a number of concrete structures, with a total length of 360 m and a maximum height of 58 m, and an earthfill embankment which spans across the original river channel. The 450 m long zoned earthfill dam is founded on pervious alluvium over 150 m deep. It has a sloping impervious core constructed from glacial till which extends 670 m upstream of the dam. This impervious blanket extends over the full width of the reservoir and is connected to the upstream face of the concrete structures. The results of a dam safety study, which was carried out due to the presence of high uplift pressures at some parts of the foundation, and stability concerns, are presented. The investigation concluded that the high uplift pressures were due to a localized defect in the upstream blanket and did not indicate any general deterioration of the blanket. Techniques that were found to be of particular use in the study for defining the source and nature of the foundation defects were: temperature surveys of flows from piezometers, cells and drains; air injection tests; and pressure response testing of cells, piezometers and drains to establish foundation interconnections. The concrete structures met the stability criteria for all load cases considered except for the navigation lock and the low level outlets. 3 refs., 6 figs

Reliability-based service life assessment of concrete structures in nuclear power plants: optimum inspection and repair

International Nuclear Information System (INIS)

Ellingwood, B.R.; Mori, Y.

1995-01-01

Research is being conducted to address aging management of safety-related reinforced concrete structures in nuclear power plants (NPPs). Documentation is being prepared to identify potential structural safety issues and to recommend criteria for use in evaluating reinforced concrete structures for continued service. Time-dependent reliability analysis provides the framework and quantitative tools for the condition assessment. The role of in-service inspection and repair in ensuring continued reliability in-service is examined. (author). 19 refs., 4 figs

Probabilistic methods for condition assessment and life prediction of concrete structures in nuclear power plants

International Nuclear Information System (INIS)

Ellingwood, B.R.; Mori, Yasuhiro

1993-01-01

A probability-based methodology is being developed in support of the NRC Structural Aging Program to assist in evaluating the reliability of existing concrete structures in nuclear power plants under potential future operating loads and extreme evironmental and accidental events. The methodology includes models to predict structural deterioration due to environmental stressors, a database to support the use of these models, and methods for analyzing time-dependent reliability of concrete structural components subjected to stochastic loads. The methodology can be used to support a plant license extension application by providing evidence that safety-related concrete structures in their current (service) condition are able to withstand future extreme events with a level of reliability sufficient for public health and safety. (orig.)

Durability and safety of concrete structures in the nuclear context. The case of the containment vessel

Energy Technology Data Exchange (ETDEWEB)

Torrenti, J.M. [Universite Paris Est, LCPC (France); Nahas, G. [IRSN/DSR (France)

2011-07-01

The durability of structures, because of its economic and environmental implications, is one of the actual hot topics in civil engineering. In the field of nuclear energy, we are facing very challenging problems like: how could we prolong the service life of actual nuclear containments and how can we assure the durability of a radioactive storage on the very long term (several centuries)? These already difficult questions in a classical civil engineering view are even more complicated in the field of nuclear energy where the structures are massive and the safety of the installations has to be considered. For the containment of nuclear power plants, these stakes will be lit with some examples of research concerning the mechanical behaviour of concrete and concrete structures (at early age, in service on long scales of time and in the event of an accident), the durability of the concrete structures (leaching, swelling due to delayed ettringite formation - DEF -) and the couplings between mechanics and durability. Finally, the importance of probabilistic aspects and the inherent difficulties will be shown. (authors)

Durability and safety of concrete structures in the nuclear context. The case of the containment vessel

International Nuclear Information System (INIS)

Torrenti, J.M.; Nahas, G.

2011-01-01

The durability of structures, because of its economic and environmental implications, is one of the actual hot topics in civil engineering. In the field of nuclear energy, we are facing very challenging problems like: how could we prolong the service life of actual nuclear containments and how can we assure the durability of a radioactive storage on the very long term (several centuries)? These already difficult questions in a classical civil engineering view are even more complicated in the field of nuclear energy where the structures are massive and the safety of the installations has to be considered. For the containment of nuclear power plants, these stakes will be lit with some examples of research concerning the mechanical behaviour of concrete and concrete structures (at early age, in service on long scales of time and in the event of an accident), the durability of the concrete structures (leaching, swelling due to delayed ettringite formation - DEF -) and the couplings between mechanics and durability. Finally, the importance of probabilistic aspects and the inherent difficulties will be shown. (authors)

76 FR 34890 - Track Safety Standards; Concrete Crossties

Science.gov (United States)

2011-06-15

...-0007, Notice No. 3] RIN 2130-AC01 Track Safety Standards; Concrete Crossties AGENCY: Federal Railroad... effective concrete crossties, for rail fastening systems connected to concrete crossties, and for automated inspections of track constructed with concrete crossties. The Track Safety Standards were amended via final...

Assessing the performance of reinforced concrete structures under impact loads

International Nuclear Information System (INIS)

Sharma, Akanshu; Reddy, G.R.; Vaze, K.K.; Ozbolt, Josko; Hofmann, J.

2011-01-01

Reinforced concrete (RC) structures housing nuclear facilities must qualify against much stringent requirements of operating and accidental loads than conventional structures. One such accidental load that must be considered while assessing the performance of safety related RC structures is impact load. It is known that the behavior of concrete/reinforced concrete structures is strongly influenced by the loading rate. The RC structural members subjected to impact loads behave quite differently as compared to the same subjected to quasi-static loading due to the strain-rate influence on strength, stiffness, and ductility as well as to the activation of inertia forces. Moreover, for concrete structures, which exhibit damage and fracture phenomena, the failure mode and cracking pattern depend significantly on loading rate. In general, there is a tendency that with the increase of loading rate the failure mode changes from mode-I to mixed mode. In order to assess the performance of existing structures against impact loads that may be generated mainly due to man-made accidental conditions, it is important to have models that can realistically predict the impact behavior of concrete structures. The present paper focuses on a relatively new approach for 3D finite element analysis of RC structures under impact loads. The approach uses rate sensitive micro-plane model as constitutive law for concrete, while the strain-rate influence is captured by the activation energy. Inertia forces are implicitly accounted for through dynamic finite element analysis. It is shown with the help of different examples that the approach can very well simulate the behavior of RC structural elements under high rate loading. (author)

Technical bulletin : structural considerations for dam safety

Energy Technology Data Exchange (ETDEWEB)

NONE

2007-07-01

This technical bulletin discussed issues related to the safety assessment of concrete water-retaining structures and timber dams. Structures reviewed in the paper included gravity dams; buttress dams; arch dams; spillway structures; intake structures; power plants; roller compacted concrete dams; and timber dams. A variety of issues related to the loss of cohesive bond and discontinuities in bedrock foundations were reviewed with reference to issues related to compressive strength, tensile strength, and shear strength. Static failure modes and failure mechanisms related to dam failures were also described. Visual indicators for potential failures include abutment and foundation movement, seepage, and structure movements. Loading combinations were discussed, and performance indicators for gravity dams were provided. Methods of analysis for considering load characteristics, structure types and geological conditions were also discussed. Modelling techniques for finite element analysis were also included. 16 refs., 3 tabs., 5 figs.

Quality Control of Concrete Structure For APR1400 Construction

International Nuclear Information System (INIS)

Seo, Inseop; Song, Changhak; Kim, Duill

2012-01-01

Nuclear structure shall be constructed to protect internal facilities in the normal operation against external accidents such as the radiation shielding, earthquakes and to be leak-proof of radioactive substances to the external environment in case of loss of coolants. containment and auxiliary building of nuclear power plants are built in reinforced concrete structures to maintain these protection functions. Nuclear structures shall be designed to ensure soundness in operation since they are located on the waterfront where is easy do drain the cooling water and so deterioration and damage of concrete structures caused by seawater can occur. Durability is ensured for concrete structures of APR1400, a Korea standard NPP, in compliance with all safety requirements. In particular, owners perform quality control directly on the production and pouring of cast in place concrete for the concrete structure construction to make sure concrete structures established with quality homogeneity and durability. This report is to look into the quality control standard and management status of cast in place concrete for APR1400 construction

Constitutive relation of concrete containing meso-structural characteristics

Directory of Open Access Journals (Sweden)

Li Guo

Full Text Available A constitutive model of concrete is proposed based on the mixture theory of porous media within thermodynamic framework. By treating concrete as a multi-phase multi-component mixture, we constructed the constitutive functions for elastic, interfacial, and plastic strain energy respectively. A constitutive law of concrete accommodating internal micro-cracks and interfacial boundaries was established. The peak stress predicted with the developed model depends primarily on the volume ratio of aggregate, and the results explain very well reported experimental phenomena. The strain-stress curve under uniaxial loading was found in a good agreement with experimental data for concrete with three different mixing proportions. Keywords: Constitutive model of concrete, Mixture theory of porous media, Meso-structure, Interfacial energy

Advanced concrete structures for thermal power plants

International Nuclear Information System (INIS)

Zerna, W.

1982-01-01

The author begins with an overview on the various types of power plants depending on the fuel used in them and then in particular deals with the reinforced concrete structures. Especially for reactor buildings and prestressed concrete pressure vessels concrete is the appropriate material. The methods of construction are described as a function of load and operation. Safety requirements brought new load types for such structures as e.g. airplane crash, internal pressure caused by pipe rupture. Dimensioning is done by means of nonlinear dynamical methods of calculation accounting for plasticizing. These methods are explained. Further the constructional principles of high natural-draft cooling towers are mentioned. (orig.) [de

Concrete structures protection, repair and rehabilitation

CERN Document Server

Woodson, R Dodge

2009-01-01

The success of a repair or rehabilitation project depends on the specific plans designed for it. Concrete Structures: Protection, Repair and Rehabilitation provides guidance on evaluating the condition of the concrete in a structure, relating the condition of the concrete to the underlying cause or causes of that condition, selecting an appropriate repair material and method for any deficiency found, and using the selected materials and methods to repair or rehabilitate the structure. Guidance is also provided for engineers focused on maintaining concrete and preparing concrete investigation r

Development priorities for non-destructive examination of concrete structures in nuclear plant

International Nuclear Information System (INIS)

1998-01-01

The objective of this report is to provide a basis for assessing development priorities for NDE of safety related concrete structures in nuclear plants, taking account of both the benefit and the cost of potential developments in NDE techniques. An OECD/NEA Workshop which considered the requirements for NDE of safety related concrete structures was held in the UK on 12 November 97. NDE techniques have the potential to satisfy at least some of the needs of the nuclear industry. NDE techniques have been used successfully on a variety of reinforced and post-tensioned concrete structures, notably highway and reservoir structures. However, there is limited experience of their use to evaluate typical nuclear safety related structures having thick sections, steel liners or access to one side only. There is a general lack of confidence in the techniques because there is very little independent advice on their applicability, capability, accuracy and reliability. The information obtained by techniques such as RADAR, ultrasonics, stress wave and radiography appears qualitative rather than quantitative and there is concern that NDE procedures lack the necessary qualification to permit their use on safety critical structures. There is no authoritative international guidance or standard for NDE of concrete structures. NDE of concrete structures is often based upon equipment developed for other materials and technologies, eg. examination of steel, evaluation of ground conditions. Other industries are developing equipment specifically for civil engineering applications and at the recent OECD workshop a number of relevant national and European programmes were identified. The nuclear industry maintain its awareness of developments and should seek to influence the development of equipment. The quantification of the capabilities of NDE techniques is seen as a priority area for development. The provision of authoritative documentation in the form of reports and Standards is desirable

The structural aging assessment program: ranking methodology for CANDU nuclear generating station concrete components

International Nuclear Information System (INIS)

Philipose, K.E.; Muhkerjee, P.K.; McColm, E.J.

1997-01-01

Most of the major structural components in CANDU nuclear generating stations are constructed of reinforced concrete. Although passive in nature, these structures perform many critical safety functions in the operation of each facility. Aging can affect the structural capacity and integrity of structures. The reduction in capacity due to aging is not addressed in design codes. Thus a program is warranted to monitor the aging of safety-related CANDU plant structures and to prioritize those that require maintenance and repairs. Prioritization of monitoring efforts is best accomplished by focusing on those structures judged to be the most critical to plant performance and safety. The safety significance of each sub-element and its degradation with time can be evaluated using a numerical rating system. This will simplify the utility's efforts, thereby saving maintenance costs while providing a higher degree of assurance that performance is maintained. This paper describes the development of a rating system (ranking procedure) as part of the Plant Life Management of CANDU generating station concrete structures and illustrates its application to an operating plant. (author)

Design of fire resistant concrete structures, using validated Fem models

NARCIS (Netherlands)

Erich, S.J.F.; Overbeek, van A.B.M.; Heijden, van der G.H.A.; Pel, L.; Huinink, H.P.; Vervuurt, A.H.J.M.; Schlangen, E.; Schlutter, de G.

2008-01-01

Fire safety of buildings and structures is an important issue, and has a great impact on human life and economy. One of the processes negatively affecting the strength of a concrete building or structure during fire is spalling. Many examples exists in which spalling of concrete during fire has

Seismic fragility of reinforced concrete structures in nuclear facilities

International Nuclear Information System (INIS)

Gergely, P.

1985-01-01

The failure and fragility analyses of reinforced concrete structures and elements in nuclear reactor facilities within the Seismic Safety Margins Research Program (SSMRP) at the Lawrence Livermore National Laboratory are evaluated. Uncertainties in material modeling, behavior of low shear walls, and seismic risk assessment for nonlinear response receive special attention. Problems with ductility-based spectral deamplification and prediction of the stiffness of reinforced concrete walls at low stress levels are examined. It is recommended to use relatively low damping values in connection with ductility-based response reductions. The study of static nonlinear force-deflection curves is advocated for better nonlinear dynamic response predictions

Analysis of crack propagation in concrete structures with structural information entropy

Institute of Scientific and Technical Information of China (English)

无

2010-01-01

The propagation of cracks in concrete structures causes energy dissipation and release, and also causes energy redistribution in the structures. Entropy can characterize the energy redistribution. To investigate the relation between the propagation of cracks and the entropy in concrete structures, cracked concrete structures are treated as dissipative structures. Structural information entropy is defined for concrete structures. A compact tension test is conducted. Meanwhile, numerical simulations are also carried out. Both the test and numerical simulation results show that the structural information entropy in the structures can characterize the propagation of cracks in concrete structures.

The Service Life Evaluation for Concrete Structure of NPP

International Nuclear Information System (INIS)

Lee, Choon Min; Kim, Seong Soo; Bae, Sung Hwan; Sik, Yoon Eui

2014-01-01

Prolonged exposure to the marine environment degrades the durability of concrete and shortens the service life of concrete due to degradation factors such as chloride, carbonation, freezing and thawing, sulfate. Therefore, many country's organizations like the Korea Concrete Institute (KCI), the American Concrete Institute (ACI), the International Federation for Structural Concrete (FIB), the American Society for Testing and Material (ASTM) which recognized the seriousness of this deterioration proposed equation models to evaluate the service life for the concrete structures. As a result, this paper is to especially consider the service life evaluation using these equation models for concrete structure of NPP in Korea compared with 60 years as a design service life. The concrete durability evaluation for Shin-Hanul NPP units 1 and 2 is carried out by using typically proposed assessment models in domestic and foreign standard. It is confirmed that the service life of concrete durability for each of deterioration factors is significantly higher than 60 years as a design service life. As a result, the study of combined deterioration for the concrete structures of NPP in future is positively necessary and maintenance control through regular monitoring should be conducted to secure safety margin basis

Rational and Safe Design of Concrete Transportation Structures for Size Effect and Multi-Decade Sustainability

Science.gov (United States)

2012-10-01

The overall goal of this project was to improve the safety and sustainability in the design of large : prestressed concrete bridges and other transportation structures. The safety of large concrete : structures, including bridges, has been insufficie...

Proceedings of the NEA workshop on development priorities for NDE of concrete structures in nuclear plants

International Nuclear Information System (INIS)

1998-01-01

The first session's objectives of this conference were to identify the perspectives of national regulators and plant operators on what is required of NDE. The second session objectives were to provide opportunity for NDE practitioners to share experience and views on the status of development of key NDE techniques: tomographic imaging for investigation of concrete structures, four examples of modern NDE techniques applied to the investigation of nuclear and non-nuclear concrete structures and a vision of future improvements, investigating concrete structures by 3D Radar imaging and imaging using mechanical impact, synopsis NDT of concrete using ultrasonics and radar. The third session objectives were to prioritise development of NDE techniques for safety related concrete structures in nuclear installations: key conclusions from earlier sessions, proposed priorities and next steps

Summary and conclusions of a program addressing aging of nuclear power plant concrete structures

International Nuclear Information System (INIS)

Naus, D.J.; Oland, C.B.; Hookham, C.J.; Graves, H.L. III

1999-01-01

Research has been conducted by the Oak Ridge National Laboratory to address aging management of nuclear power plant concrete structures. The purpose was to identify potential structural safety issues and acceptance criteria for use in continued service assessments. The focus of this program was on structural integrity rather than on leaktightness or pressure retention of concrete structures. Primary program accomplishments include formulation of a Structural Materials Information Center that contains data and information on the time variation of material properties under the influence of pertinent environmental stressors and aging factors for 144 materials, an aging assessment methodology to identify critical structures and degradation factors that can potentially impact their performance, guidelines and evaluation criteria for use in condition assessments of reinforced concrete structures, and a reliability-based methodology for current condition assessments and estimations of future performance of reinforced concrete nuclear power plant structures. In addition, in-depth evaluations were conducted of several nondestructive evaluation and repair-related technologies to develop guidance on their applicability. (orig.)

Structural Precast Concrete Handbook

DEFF Research Database (Denmark)

Kjærbye, Per Oluf H

Structural concept for precast concrete systems. Design og precast reinforced concrete components. Design of precast concrete connections. Illustrations on design of precast concrete buildings. Precast concrete assembly.......Structural concept for precast concrete systems. Design og precast reinforced concrete components. Design of precast concrete connections. Illustrations on design of precast concrete buildings. Precast concrete assembly....

Assessment of modular construction for safety-related structures at advanced nuclear power plants

International Nuclear Information System (INIS)

Braverman, J.; Morante, R.; Hofmayer, C.

1997-03-01

Modular construction techniques have been successfully used in a number of industries, both domestically and internationally. Recently, the use of structural modules has been proposed for advanced nuclear power plants. The objective in utilizing modular construction is to reduce the construction schedule, reduce construction costs, and improve the quality of construction. This report documents the results of a program which evaluated the proposed use of modular construction for safety-related structures in advanced nuclear power plant designs. The program included review of current modular construction technology, development of licensing review criteria for modular construction, and initial validation of currently available analytical techniques applied to concrete-filled steel structural modules. The program was conducted in three phases. The objective of the first phase was to identify the technical issues and the need for further study in order to support NRC licensing review activities. The two key findings were the need for supplementary review criteria to augment the Standard Review Plan and the need for verified design/analysis methodology for unique types of modules, such as the concrete-filled steel module. In the second phase of this program, Modular Construction Review Criteria were developed to provide guidance for licensing reviews. In the third phase, an analysis effort was conducted to determine if currently available finite element analysis techniques can be used to predict the response of concrete-filled steel modules

POROUS STRUCTURE OF ROAD CONCRETE

Directory of Open Access Journals (Sweden)

M. K. Pshembaev

2016-01-01

Full Text Available Having a great number of concrete structure classifications it is recommended to specify the following three principal types: microstructure – cement stone structure; mesostructure – structure of cement-sand mortar in concrete; macrostucture – two-component system that consists of mortar and coarse aggregate. Every mentioned-above structure has its own specific features which are related to the conditions of their formation. Thus, microstructure of cement stone can be characterized by such structural components as crystal intergrowth, tobermorite gel, incompletely hydrated cement grains and porous space. The most important technological factors that influence on formation of cement stone microstructure are chemical and mineralogical cement composition, its grinding fineness, water-cement ratio and curing condition. Specific cement stone microstructure is formed due to interrelation of these factors. Cement stone is a capillary-porous body that consists of various solid phases represented predominantly by sub-microcrystals of colloidal dispersion. The sub-microcrystals are able adsorptively, osmotically and structurally to withhold (to bind some amount of moisture. Protection of road concrete as a capillary-porous body is considered as one of the topical issues. The problem is solved with the help of primary and secondary protection methods. Methods of primary protection are used at the stage of designing, preparation and placing of concrete. Methods of secondary protection are applied at the operational stage of road concrete pavement. The paper considers structures of concrete solid phase and characteristics of its porous space. Causes of pore initiation, their shapes, dimensions and arrangement in the concrete are presented in the paper. The highest hazard for road concrete lies in penetration of aggressive liquid in it and moisture transfer in the cured concrete. Water permeability of concrete characterizes its filtration factor which

Porous Structure of Road Concrete

OpenAIRE

Пшембаев, М. К.; Гиринский, В. В.; Ковалев, Я. Н.; Яглов, В. Н.; Будниченко, С. С.

2016-01-01

Having a great number of concrete structure classifications it is recommended to specify the following three principal types: microstructure – cement stone structure; mesostructure – structure of cement-sand mortar in concrete; macrostucture – two-component system that consists of mortar and coarse aggregate. Every mentioned-above structure has its own specific features which are related to the conditions of their formation. Thus, microstructure of cement stone can be characterized by such st...

Assessment of degradation and aging of nuclear power plants concrete structures

International Nuclear Information System (INIS)

Busby, J.; Naus, D.; Graves, H.; Sheikh, A.; Le Pape, Y.; Rashid, J.; Saouma, V.; Wall, J.

2015-01-01

This paper summarizes the results of an expert-panel assessment of ageing degradation modes and mechanisms of concrete structures in NPPs, where, based on specific operating environments, degradation is likely to occur, or may have occurred; to define relevant aging and degradation modes and mechanisms; and to perform systematic assessment of the effects of these age-related degradation mechanisms on the future life of those materials and structures. The following 7 degradation modes and mechanisms have been identified as having the greatest potential impact on the ability of concrete structures to fulfill their safety related functions during long-term NPP operation. 1) Corrosion of conventional reinforcement is difficult to assess because of inaccessibility to inspection; 2) Creep of pre-stressed concrete containments continuously affects the internal stress state and adds to tendon relaxation and gradual loss of prestress; 3) Irradiation of concrete lacks sufficient data to for a clear evaluation of its effects on long-term operations; 4) Alkali-silica reaction potential consequences on the structural integrity of the containment; 5) Fracture/cracking, which is a well understood behavior characteristic of concrete structures and is accounted for in structural design, plays a unique role in post-tensioned containments during de-tensioning and re-tensioning operations which may be undertaken as part of life extension retrofit work, resulting in delamination, and may evolve with time as a creep-cracking interaction mechanism; 6) Boric acid attack of concrete in the spent fuel pool involves knowledge gaps related to the kinetics and the extent of the attack (role of the concrete mix design); 7) Corrosion of the inaccessible side of the spent fuel pool and containment liners and the stress corrosion cracking of the tendons are important degradation modes due to the absence of in-service inspection. The potential impact of these mechanisms may be mitigated by

Concrete structures

CERN Document Server

Setareh, Mehdi

2017-01-01

This revised, fully updated second edition covers the analysis, design, and construction of reinforced concrete structures from a real-world perspective. It examines different reinforced concrete elements such as slabs, beams, columns, foundations, basement and retaining walls and pre-stressed concrete incorporating the most up-to-date edition of the American Concrete Institute Code (ACI 318-14) requirements for the design of concrete structures. It includes a chapter on metric system in reinforced concrete design and construction. A new chapter on the design of formworks has been added which is of great value to students in the construction engineering programs along with practicing engineers and architects. This second edition also includes a new appendix with color images illustrating various concrete construction practices, and well-designed buildings. The ACI 318-14 constitutes the most extensive reorganization of the code in the past 40 years. References to the various sections of the ACI 318-14 are pro...

Structural design of nuclear power plant using stiffened steel plate concrete structure

International Nuclear Information System (INIS)

Moon, Ilhwan; Kim, Sungmin; Mun, Taeyoup; Kim, Keunkyeong; Sun, Wonsang

2009-01-01

Nuclear power is an alternative energy source that is conducive to mitigate the environmental strains. The countries having nuclear power plants are encouraging research and development sector to find ways to construct safer and more economically feasible nuclear power plants. Modularization using Steel Plate Concrete(SC) structure has been proposed as a solution to these efforts. A study of structural modules using SC structure has been performed for shortening of construction period and enhancement of structural safety of NPP structures in Korea. As a result of the research, the design code and design techniques based on limit state design method has been developed. The design code has been developed through various structural tests and theoretical studies, and it has been modified by application design of SC structure for NPP buildings. The code consists of unstiffened SC wall design, stiffened SC wall design, Half-SC slab design, stud design, connection design and so on. The stiffened steel plate concrete(SSC) wall is SC structure whose steel plates with ribs are composed on both sides of the concrete wall, and this structure was developed for improved constructability and safety of SC structure. This paper explains a design application of SC structure for a sample building specially devised to reflect all of major structural properties of main buildings of APR1400. In addition, Stiffening effect of SSC structure is evaluated and structural efficiency of SSC structure is verified in comparison with that of unstiffened SC structure. (author)

Steel-concrete bond model for the simulation of reinforced concrete structures

International Nuclear Information System (INIS)

Mang, Chetra

2015-01-01

Reinforced concrete structure behavior can be extremely complex in the case of exceeding the cracking threshold. The composite characteristics of reinforced concrete structure should be finely presented especially in the distribution stress zone between steel-concrete at their interface. In order to compute the industrial structures, a perfect relation hypothesis between steel and concrete is supposed in which the complex phenomenon of the two-material relation is not taken into account. On the other hand, this perfect relation is unable to predict the significant disorders, the repartition, and the distribution of the cracks, which is directly linked to the steel. In literature, several numerical methods are proposed in order to finely study the concrete-steel bond behavior, but these methods give many difficulties in computing complex structures in 3D. With the results obtained in the thesis framework of Torre-Casanova (2012), the new concrete-steel bond model has been developed to improve performances (iteration numbers and computational time) and the representation (cyclic behavior) of the initial one. The new model has been verified with analytical solution of steel-concrete tie and validated with the experimental results. The new model is equally tested with the structural scale to compute the shear wall behavior in the French national project (CEOS.fr) under monotonic load. Because of the numerical difficulty in post-processing the crack opening in the complex crack formation, a new crack opening method is also developed. This method consists of using the discontinuity of relative displacement to detect the crack position or using the slip sign change between concrete-steel. The simulation-experiment comparison gives validation of not only the new concrete-steel bond model but also the new crack post-processing method. Finally, the cyclic behavior of the bond law with the non-reduced envelope is adopted and integrated in the new bond model in order to take

Safety-related concrete structure design and construction of Rokkasho Reprocessing Plant

International Nuclear Information System (INIS)

Morishita, Hideki; Munakata, Yoshinari; Togashi, Akihito

2003-01-01

The Rokkasho Reprocessing Plant of the Japan Nuclear Fuel Co. Ltd., is a facility to reprocess remained uranium without firing and newly formed plutonium contained in spent fuels used at the nuclear power stations, to produce fuels to be repeatedly used. Constructions in this facility has some characteristics shown as follows: 1) radiation shielding and seismic isolated functions like those at the nuclear power plants, 2) reduction of wall thickness based on partially using heavy concrete at walls required for radiation shielding, 3) protective design against fly-coming matters such as aircrafts, 4) construction period reduction based on winter construction and large scale block engineering. Here were described characteristics of designs on radiation shielding, seismic isolated and fly-coming matters protection construction engineering and quality control on concrete. (G.K.)

Online Monitoring of Concrete Structures in Nuclear Power Plants: Interim Report

Energy Technology Data Exchange (ETDEWEB)

Mahadevan, Sankaran [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cai, Guowei [Idaho National Lab. (INL), Idaho Falls, ID (United States); Agarwal, Vivek [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2015-03-01

The existing fleet of nuclear power plants in the United States have initial operating licenses of 40 years, and many of these plants have applied for and received license extensions. As plant structures, systems, and components age, their useful life—considering both structural integrity and performance—is reduced as a result of deterioration of the materials. Assessment and management of aging concrete structures in nuclear plants require a more systematic approach than simple reliance on existing code-based design margins of safety. Structural health monitoring is required to produce actionable information regarding structural integrity that supports operational and maintenance decisions. The online monitoring of concrete structures project conducted under the Advanced Instrumentation, Information, and Control Technologies Pathway of the Light Water Reactor Sustainability program at Idaho National Laboratory is seeking to develop and demonstrate capabilities for concrete structures health monitoring. Through this research project, several national laboratories and Vanderbilt University propose to develop a framework of research activities for the health monitoring of nuclear power plant concrete structures that includes the integration of four elements—damage modeling, monitoring, data analytics, and uncertainty quantification. This report briefly discusses activities in this project during October-December, 2014. The most significant activity during this period was the organizing of a two-day workshop on research needs in online monitoring of concrete structures, hosted by Vanderbilt University in November 2014. Thirty invitees from academia, industry and government participated in the workshop. The presentations and discussions at the workshop surveyed current activities related to concrete structures deterioration modeling and monitoring, and identified the challenges, knowledge gaps, and opportunities for advancing the state of the art; these

Performance and working life of cathodic protection systems for concrete structures

NARCIS (Netherlands)

Polder, R.B.; Worm, D.; Courage, W.; Leegwater, G.

2012-01-01

Corrosion of reinforcing steel in concrete structures causes concrete cracking and steel diameter reduction, eventually resulting in loss of safety. Conventional repair means heavy, labour intensive and costly work and the required quality level is under economic pressure. Consequently, conventional

Concrete component aging and its significance relative to life extension of nuclear power plants

International Nuclear Information System (INIS)

Naus, D.J.

1986-09-01

The objectives of this study are to (1) expand upon the work that was initiated in the first two Electric Power Research Institute studies relative to longevity and life extension considerations of safety-related concrete components in light-water reactor (LWR) facilities and (2) provide background that will logically lead to subsequent development of a methodology for assessing and predicting the effects of aging on the performance of concrete-based materials and components. These objectives are consistent with Nuclear Plant Aging Research (NPAR) Program goals: (1) to identify and characterize aging and service wear effects that, if unchecked, could cause degradation of structures, components, and systems and, thereby, impair plant safety; (2) to identify methods of inspection, surveillance, and monitoring or of evaluating residual life of structures, components, and systems that will ensure timely detection of significant aging effects before loss of safety function; and (3) to evaluate the effectiveness of storage, maintenance, repair, and replacement practices in mitigating the rate and extent of degradation caused by aging and service wear

Report of the task group reviewing national and international activities in the area of ageing of nuclear power plant concrete structures

International Nuclear Information System (INIS)

1996-01-01

After a background information on the mandate of the task group and its organisation, the longevity of nuclear power plants is first addressed: the present status of nuclear power plants in the 25 OECD Member Countries is summarised and the importance of ensuring continued safe operation of nuclear power plants described. Safety-related concrete structures (primarily containments) for several reactor concepts are briefly described as well as their materials of construction. Primary mechanisms that can produce adverse ageing of the concrete structures are described (e.g., chemical attack and corrosion of steel reinforcement). The overall performance of nuclear power plant concrete structures is described and age-related degradation incidences that have occurred are noted (e.g., corrosion of steel in water intake structures and corrosion of metal liners). National ageing management programmes of OECD Member Countries are then described with the emphasis placed on nuclear power plant safety-related concrete structures. Although the majority of these programmes are addressing components such as the reactor pressure vessel and steam generator, several national programmes have sophisticated activities that address the concrete structures (e.g., Canada, France, Japan, Switzerland, United Kingdom, and the United States). International ageing management activities are then summarised, primarily addressed under the auspices of the International Atomic Energy Agency (IAEA) (ageing management activities for concrete containment buildings) and the Commission of European Communities (CEC) (assessment of the long-term durability of reinforced and prestressed concrete structures and buildings, and steel containments in nuclear power plants). General conclusions and recommendations are provided at the end of the report

Local response of concrete structures to explosive loading

International Nuclear Information System (INIS)

Freund, H.U.; Krutzik, N.J.; Muller, K.

1989-01-01

This paper reports on the HDR safety program experiments performed concerning demolition of concrete structures and pipes by explosive charges. The precalculability of the local structure reaction as well as that of the global plant was checked. The effect on the bore hole wall by the detonating explosive and the local concrete behavior around the bore hole were investigated. The measured pressure-time history in and around the bore hole is compared with the calculated values. The calculated values seem to be near reality (as far as measurements are available), concerning pressure rise curve within the bore hole and the peak pressure. The analysis of the blow off contours performed with two variations of the material strength of the concrete plates is presented

Corrosion initiation and service life of concrete structures

International Nuclear Information System (INIS)

Byung Hwan Oh; Bong Seok Jang

2005-01-01

The Corrosion of steel reinforcements in concrete is of great concern in the view of safety and durability of reinforced concrete structures. The reinforced concrete structures exposed to sea environments suffer from corrosion of steel bars due to chloride ingress. The chloride penetration into concrete is influenced by many parameters such as type of cement, mixture proportions and existence of rebars. The conventional diffusion analyses have neglected the existence of steel bar in concrete. The purpose of the present paper is, therefore, to explore the effects of reinforcement on the chloride diffusion in concrete structures by incorporating realistic diffusion models. To this end, the nonlinear binding isotherm which includes the effects of cement types and mixture proportion has been introduced in the chloride diffusion analysis. The effects of reinforcements on the chloride penetration have been analyzed through finite element analysis. The present study indicates that the chlorides are accumulated in front of a reinforcing bar and the accumulation of chlorides is much more pronounced for the case of larger-size bars. The higher accumulation of chlorides at bar location causes faster corrosion of reinforcing bars. The corrosion initiation time reduces by about 30-40 percent when the existence of rebar is considered in the chloride diffusion analysis. (authors)

An improved basis for evaluating continued service of Category I concrete structures in nuclear power plants

International Nuclear Information System (INIS)

Naus, D.J.; Oland, C.B.; Ellingwood, B.; Mori, Y.; Arndt, E.G.

1992-01-01

The Structural Aging (SAG) Program has the overall objective of preparing technical bases for regulatory criteria which will provide the NRC with potential structural safety issues and acceptance criteria for use in nuclear power plant evaluations for continued service. In meeting this objective three primary activities are underway: (1) development of a structural materials information center containing data and information on the variation of concrete and concrete-related material properties over time; (2) establishment of procedures to make quantitative evaluations of the presence, magnitude, and significance of environmental stressors or aging factors that can impact critical component performance, as well as techniques which can be used for repair of degraded concrete structures; and (3) formulation of a quantitative methodology for performing current condition assessments and making reliability-based life predictions of critical concrete structures in nuclear power plants. Accomplishments to date under each of these tasks are presented

Non-Destructive Testing for Concrete Structure

International Nuclear Information System (INIS)

Tengku Sarah Tengku Amran; Noor Azreen Masenwat; Mohamad Pauzi Ismail

2015-01-01

Nondestructive testing (NDT) is a technique to determine the integrity of a material, component or structure. It is essential in the inspection of alteration, repair and new construction in the building industry. There are a number of non-destructive testing techniques that can be applied to determine the integrity of concrete in a completed structure. Each has its own advantages and limitations. For concrete, these problems relate to strength, cracking, dimensions, delamination, and inhomogeneities. NDT is reasonably good and reliable tool to measure the property of concrete which also gives the fair indication of the compressive strength development. This paper discussed the concrete inspection using combined methods of NDT. (author)

Plant Life Management of the EC6 Concrete Containment Structure

Energy Technology Data Exchange (ETDEWEB)

Abrishami, Homayoun; Ricciuti, Rick; Khan, Azhar [CANDU Energy Inc., Mississauga (Canada)

2012-03-15

Aging of reinforced concrete structures due to service conditions, aggressive environments, or accidents may cause their strength, serviceability and durability to decrease over time. Due to the complex nature of safety-related structures in nuclear power plants in comparison to other structures, they possess a number of characteristics that make them comparison to other structures, they possess a number of characteristics that make them unique. These characteristics are: thick concrete cross-sections, heavy reinforcement, often one-side access only, subjected to such ageing stresses as irradiation and elevated temperature, in addition to other typical ageing mechanisms (i. e., exposure to freeze/thaw cycles, aggressive chemicals, etc.) that typically affects other types of non-nuclear structures. For a new plant, the Plant Life Management Program (PLiM) should start in the design process and then continues through construction, plant operation and decommissioning. Hence PLiM must provide not only Ageing Management program (AMP) but also provide requirements on material characteristic and the design criteria as well. The purpose of this paper is to present the Plant Life Management (PLiM) strategy for the concrete containment structure of EC6 (Enhanced CANDU 6) Nuclear Power Plant designed by CANDU Energy Inc. The EC6 is designed for 100-year plant life including a 60-year operating life and an additional 40-year decommissioning period of time. The approach adopted for the PLiM strategy of the concrete containment structure is a preventive one, key areas being: 1) design methodology, 2) material performance and 3) life cycle management and ageing management program. In addition to strength and serviceability, durability is a major consideration during the design phase, service life and up to the completion of decommissioning. Factors affecting durability design include: a) concrete performance, b) structural application, and c) consideration of environmental

Plant Life Management of the EC6 Concrete Containment Structure

International Nuclear Information System (INIS)

Abrishami, Homayoun; Ricciuti, Rick; Khan, Azhar

2012-01-01

Aging of reinforced concrete structures due to service conditions, aggressive environments, or accidents may cause their strength, serviceability and durability to decrease over time. Due to the complex nature of safety-related structures in nuclear power plants in comparison to other structures, they possess a number of characteristics that make them comparison to other structures, they possess a number of characteristics that make them unique. These characteristics are: thick concrete cross-sections, heavy reinforcement, often one-side access only, subjected to such ageing stresses as irradiation and elevated temperature, in addition to other typical ageing mechanisms (i. e., exposure to freeze/thaw cycles, aggressive chemicals, etc.) that typically affects other types of non-nuclear structures. For a new plant, the Plant Life Management Program (PLiM) should start in the design process and then continues through construction, plant operation and decommissioning. Hence PLiM must provide not only Ageing Management program (AMP) but also provide requirements on material characteristic and the design criteria as well. The purpose of this paper is to present the Plant Life Management (PLiM) strategy for the concrete containment structure of EC6 (Enhanced CANDU 6) Nuclear Power Plant designed by CANDU Energy Inc. The EC6 is designed for 100-year plant life including a 60-year operating life and an additional 40-year decommissioning period of time. The approach adopted for the PLiM strategy of the concrete containment structure is a preventive one, key areas being: 1) design methodology, 2) material performance and 3) life cycle management and ageing management program. In addition to strength and serviceability, durability is a major consideration during the design phase, service life and up to the completion of decommissioning. Factors affecting durability design include: a) concrete performance, b) structural application, and c) consideration of environmental

Study of structural reliability of existing concrete structures

Science.gov (United States)

Druķis, P.; Gaile, L.; Valtere, K.; Pakrastiņš, L.; Goremikins, V.

2017-10-01

Structural reliability of buildings has become an important issue after the collapse of a shopping center in Riga 21.11.2013, caused the death of 54 people. The reliability of a building is the practice of designing, constructing, operating, maintaining and removing buildings in ways that ensure maintained health, ward suffered injuries or death due to use of the building. Evaluation and improvement of existing buildings is becoming more and more important. For a large part of existing buildings, the design life has been reached or will be reached in the near future. The structures of these buildings need to be reassessed in order to find out whether the safety requirements are met. The safety requirements provided by the Eurocodes are a starting point for the assessment of safety. However, it would be uneconomical to require all existing buildings and structures to comply fully with these new codes and corresponding safety levels, therefore the assessment of existing buildings differs with each design situation. This case study describes the simple and practical procedure of determination of minimal reliability index β of existing concrete structures designed by different codes than Eurocodes and allows to reassess the actual reliability level of different structural elements of existing buildings under design load.

Serviceability design load factors and reliability assessments for reinforced concrete containment structures

International Nuclear Information System (INIS)

Han Bong Koo

1998-01-01

A reinforced concrete nuclear power plant containment structure is subjected to various random static and stochastic loads during its lifetime. Since these loads involve inherent randomness and other uncertainties, an appropriate probabilistic model for each load must be established in order to perform reliability analysis. The current ASME code for reinforced concrete containment structures are not based on probability concepts. The stochastic nature of natural hazard or accidental loads and the variations of material properties require a probabilistic approach for a rational assessment of structural safety and performance. The paper develops probability-based load factors for the limit state design of reinforced concrete containment structures. The purpose of constructing reinforced concrete containment structure is to protect against radioactive release, and so the use of a serviceability limit state against crack failure that can cause the emission of radioactive materials is suggested as a critical limit state for reinforced concrete containment structures. Load factors for the design of reinforced concrete containment structures are proposed and carried out the reliability assessments. (orig.)

A Review of the Effects of Elevated Temperature on Concrete Materials and Structures

International Nuclear Information System (INIS)

Naus, D.J.; Graves, H.L. III

2006-01-01

Concrete's properties are more complex than those of most materials because not only is concrete a composite material whose constituents have different properties, but its properties depend upon moisture and porosity. Exposure of concrete to elevated temperature affects its mechanical and physical properties. Elements could distort and displace, and, under certain conditions, the concrete surfaces could spall due to the buildup of steam pressure. Because thermally-induced dimensional changes, loss of structural integrity, and release of moisture and gases resulting from the migration of free water could adversely affect plant operations and safety, a complete understanding of the behavior of concrete under long-term elevated-temperature exposure as well as both during and after a thermal excursion resulting from a postulated design-basis accident condition is essential for reliable design evaluations and assessments of nuclear power plant structures. As the properties of concrete change with respect to time and the environment to which it is exposed, an assessment of the effects of concrete aging is also important in performing safety evaluations. The effects of elevated temperature on Portland cement concretes and constituent materials are summarized, design codes and standards identified, and considerations for elevated temperature service noted. (authors)

Seismic design and performance of nuclear safety related RC structures based on new seismic design principle

International Nuclear Information System (INIS)

Murugan, R.; Sivathanu Pillai, C.; Chattopadhyaya, S.; Sundaramurthy, C.

2011-01-01

Full text: Seismic design of safety related Reinforced Concrete (RC) structures of Nuclear power plants (NPP) in India as per the present AERB codal procedures tries to ensure predominantly elastic behaviour under OBE so that the features of Nuclear Power Plant (NPP) necessary for continued safe operation are designed to remain functional and prevent accident (collapse) of NPP under SSE for which certain Structures, Systems and Components (SSCs) those are necessary to ensure the capability to shut down the reactor safely, are designed to remain functional. While the seismic design principles of non safety related structures as per Indian code (IS 1893-2002) are ensuring elastic behaviour under DBE and inelastic behaviour under MCE by utilizing ductility and energy dissipation capacity of the structure effectively. The design principle of AERB code is ensuring elastic behaviour under OBE and is not enlightening much inference about the overall structural behaviour under SSE (only ensuring the capability of certain SSCs required for safe shutdown of reactor). Various buildings and structures of Indian Nuclear power plant are classified from the basis of associated safety functions in a descending order in according with their roles in preventions and mitigation of an accident or support functions for prevention. This paper covers a comprehensive seismic analysis and design methodology based on the AERB codal provisions followed for safety related RC structure taking Diesel Generator Building of PFBR as a case study and study and investigates its performance under OBE and SSE by carrying out Non-linear static Pushover analysis. Based on the analysis, observed variations, recommendations are given for getting the desired performance level so as to implement performance based design in the future NPP design

Seismic reliability assessment methodology for CANDU concrete containment structures

International Nuclear Information System (INIS)

Stephens, M.J.; Nessim, M.A.; Hong, H.P.

1995-05-01

A study was undertaken to develop a reliability-based methodology for the assessment of existing CANDU concrete containment structures with respect to seismic loading. The focus of the study was on defining appropriate specified values and partial safety factors for earthquake loading and resistance parameters. Key issues addressed in the work were the identification of an approach to select design earthquake spectra that satisfy consistent safety levels, and the use of structure-specific data in the evaluation of structural resistance. (author). 23 refs., 9 tabs., 15 figs

Review of concrete biodeterioration in relation to nuclear waste.

Science.gov (United States)

Turick, Charles E; Berry, Christopher J

2016-01-01

Storage of radioactive waste in concrete structures is a means of containing wastes and related radionuclides generated from nuclear operations in many countries. Previous efforts related to microbial impacts on concrete structures that are used to contain radioactive waste showed that microbial activity can play a significant role in the process of concrete degradation and ultimately structural deterioration. This literature review examines the research in this field and is focused on specific parameters that are applicable to modeling and prediction of the fate of concrete structures used to store or dispose of radioactive waste. Rates of concrete biodegradation vary with the environmental conditions, illustrating a need to understand the bioavailability of key compounds involved in microbial activity. Specific parameters require pH and osmotic pressure to be within a certain range to allow for microbial growth as well as the availability and abundance of energy sources such as components involved in sulfur, iron and nitrogen oxidation. Carbon flow and availability are also factors to consider in predicting concrete biodegradation. The microbial contribution to degradation of the concrete structures containing radioactive waste is a constant possibility. The rate and degree of concrete biodegradation is dependent on numerous physical, chemical and biological parameters. Parameters to focus on for modeling activities and possible options for mitigation that would minimize concrete biodegradation are discussed and include key conditions that drive microbial activity on concrete surfaces. Copyright © 2015. Published by Elsevier Ltd.

Evolution of sorption properties in large-scale concrete structures accounting for long-term physical-chemical concrete degradation - 59297

International Nuclear Information System (INIS)

Perko, Janez; Jacques, Diederik; Mallants, Dirk; Seetharam, Suresh

2012-01-01

Long-term safety of radioactive waste disposal facilities relies on the longevity of natural or engineered barriers designed to minimize the migration of contaminants from the facility into the environment. Especially near surface disposal facilities, such as planned by ONDRAF/NIRAS for the Dessel site in Belgium, long-term safety relies almost exclusively on the containment ability of the engineered barriers (EB) with concrete being the most important EB material used. Concrete is preferred over other materials mainly due to its favourable chemical properties resulting in a high chemical retention capacity, and owing to its good hydraulic isolation properties. However, due to the long time frames typically involved in safety assessment, the chemical, physical and mechanical properties of concrete evolve in time. The alterations in concrete mineralogy also cause changes in pH and sorption behaviour for many radionuclides during chemical degradation processes. Application of dynamic sorption of concrete requires an adequate knowledge of long-term concrete degradation processes, knowledge of the effect of changing mineralogy to sorption of radionuclides and knowledge of large-scale system behaviour over time. Moreover, when applied to safety assessment models, special attention is required to assure robustness and transparency of the implementation. The discussion in this paper focuses on the sorption properties of concrete; selection of data, rescaling issues and on the hypotheses used to build a robust and yet transparent dynamic model for large-scale concrete structures for assessing the long-term performance. In this paper we summarize the steps required for the appropriate use of sorption values for large-scale cementitious components accounting for long-term concrete degradation in safety assessment studies. Four steps were recognized through the safety assessment in the framework of the license application for the near-surface disposal facility in Dessel

Continuing the service of aging concrete structures in nuclear power plants

International Nuclear Information System (INIS)

Naus, D.J.; Oland, C.B.; Arndt, E.G.

1993-01-01

Concrete structures play a vital role in the safe operation of all light-water reactor plants because they provide foundation, support, shielding and containment functions. History tells us that concrete is a durable material. However, a number of factors can compromise its performance, singly or in combination: (1) faulty design, (2) use of unsuitable materials, (3) improper workmanship, (4) exposure to aggressive environments, and (5) excessive structural loads. Furthermore, aging of nuclear power plant (NPP) concrete structures occurs with the passage of time and has the potential, if its effects are not controlled, to increase the risk to public health and safety. Although limited, incidences of degradation of concrete structures in NPPs indicate that there is a need for improved surveillance, inspection/testing, and maintenance to enhance the technical bases for assurance of continued safe operation of NPPs. Guidelines and criteria for use in evaluating the remaining structural margins (residual life) are required. Potential regulatory applications of this research include: improved predictions of long-term material and structural performance and available safety margins at future times; establishment of limits on exposure to environmental stressors; reduction in total reliance by licensing on inspection and surveillance through development of a methodology which will enable the integrity of structures to be assessed (either pre- or post-accident); and improvements in damage inspection methodology through potential incorporation of results into national standards which could be referenced by standard review plans

A study on sodium-concrete reaction

Energy Technology Data Exchange (ETDEWEB)

Pae, Jae Huem; Min, Byung Hoon; Lee, Joon Sik; Lee, Choong Hui; Chung, Ki Hong; Keum, Choong Ki [Suwon University, Suwon (Korea, Republic of)

1994-07-15

Sodium is commonly used as a coolant in liquid metal reactor. A large amount of its leakage may be possible in hypothetical accidents, even though the possibility is very low. In case that the leaked hot sodium comes in direct contact with structural concrete of liquid metal reactor, the reactor`s integrity can be challenged by the rupture of structure materials, hydrogen generation and its explosion, and release of radioactive aerosols due to sodium-concrete reaction. The knowledge of sodium-concrete reaction is evaluated to be one of the important and indispensable technologies for the establishment of safety measure in liquid metal reactor. In this study, the experimental facility of sodium-concrete reaction is to be designed, constructed and operated. And the reaction phenomena of sodium-concrete reaction is also to be analyzed through the experimental results. The aim of this study is to establish the measure of safety and protection for sodium-related facilities and to secure one of the fundamental technologies of liquid metal reactor safety. 47 refs., 7 figs., 13 tab.

Simulation analysis of impact tests of steel plate reinforced concrete and reinforced concrete slabs against aircraft impact and its validation with experimental results

International Nuclear Information System (INIS)

Sadiq, Muhammad; Xiu Yun, Zhu; Rong, Pan

2014-01-01

Highlights: • Simulation analysis is carried out with two constitutive concrete models. • Winfrith model can better simulate nonlinear response of concrete than CSCM model. • Performance of steel plate concrete is better than reinforced concrete. • Thickness of safety related structures can be reduced by adopting steel plates. • Analysis results, mainly concrete material models should be validated. - Abstract: The steel plate reinforced concrete and reinforced concrete structures are used in nuclear power plants for protection against impact of an aircraft. In order to compare the impact resistance performance of steel plate reinforced concrete and reinforced concrete slabs panels, simulation analysis of 1/7.5 scale model impact tests is carried out by using finite element code ANSYS/LS-DYNA. The damage modes of all finite element models, velocity time history curves of the aircraft engine and damage to aircraft model are compared with the impact test results of steel plate reinforced concrete and reinforced concrete slab panels. The results indicate that finite element simulation results correlate well with the experimental results especially for constitutive winfrith concrete model. Also, the impact resistance performance of steel plate reinforced concrete slab panels is better than reinforced concrete slab panels, particularly the rear face steel plate is very effective in preventing the perforation and scabbing of concrete than conventional reinforced concrete structures. In this way, the thickness of steel plate reinforced concrete structures can be reduced in important structures like nuclear power plants against impact of aircraft. It also demonstrates the methodology to validate the analysis procedure with experimental and analytical studies. It may be effectively employed to predict the precise response of safety related structures against aircraft impact

Maintenance and preservation of concrete structures. Report 3: Abrasion-erosion resistance of concrete

Science.gov (United States)

Liu, T. C.

1980-07-01

This report describes a laboratory test program on abrasion-erosion resistance of concrete, including the development of a new underwater abrasion-erosion test method. This program was designed to evaluate the relative abrasion-erosion resistance of various materials considered for use in the repair of erosion-damaged concrete structures. The test program encompassed three concrete types (conventional concrete, fiber-reinforced concrete, and polymer concrete); seven aggregate types (limestone, chert, trap rock, quartzite, granite, siliceous gravel, and slag); three principal water-cement rations (0.72, 0.54, and 0.40); and six types of surface treatment (vacuum, polyurethane coating, acrylic mortar coating, epoxy mortar coating, furan resin mortar coating, and iron aggregate topping). A total of 114 specimens made from 41 batches of concrete was tested. Based on the test data obtained, a comprehensive evaluation of the effects of various parameters on the abrasion-erosion resistance of concrete was presented. Materials suitable for use in the repair of erosion-damaged concrete structures were recommended. Additional work to correlate the reported findings with field performance was formulated.

Working life of cathodic protection systems for concrete structures - Analysis of field data

NARCIS (Netherlands)

Polder, R.B.; Leegwater, G.; Worm, D.; Courage, W.

2012-01-01

Corrosion of reinforcing steel in concrete structures causes concrete cracking, steel diameter reduction and eventually loss of safety. In infrastructure this is mainly due to penetration of chloride ions from de-icing or marine salts. Conventional repair means heavy, labour intensive and costly

A Reusable PZT Transducer for Monitoring Initial Hydration and Structural Health of Concrete

Directory of Open Access Journals (Sweden)

Yaowen Yang

2010-05-01

Full Text Available During the construction of a concrete structure, strength monitoring is important to ensure the safety of both personnel and the structure. Furthermore, to increase the efficiency of in situ casting or precast of concrete, determining the optimal time of demolding is important for concrete suppliers. Surface bonded lead zirconate titanate (PZT transducers have been used for damage detection and parameter identification for various engineering structures over the last two decades. In this work, a reusable PZT transducer setup for monitoring initial hydration of concrete and structural health is developed, where a piece of PZT is bonded to an enclosure with two bolts tightened inside the holes drilled in the enclosure. An impedance analyzer is used to acquire the admittance signatures of the PZT. Root mean square deviation (RMSD is employed to associate the change in concrete strength with changes in the PZT admittance signatures. The results show that the reusable setup is able to effectively monitor the initial hydration of concrete and the structural health. It can also be detached from the concrete for future re-use.

A Reusable PZT Transducer for Monitoring Initial Hydration and Structural Health of Concrete

Science.gov (United States)

Yang, Yaowen; Divsholi, Bahador Sabet; Soh, Chee Kiong

2010-01-01

During the construction of a concrete structure, strength monitoring is important to ensure the safety of both personnel and the structure. Furthermore, to increase the efficiency of in situ casting or precast of concrete, determining the optimal time of demolding is important for concrete suppliers. Surface bonded lead zirconate titanate (PZT) transducers have been used for damage detection and parameter identification for various engineering structures over the last two decades. In this work, a reusable PZT transducer setup for monitoring initial hydration of concrete and structural health is developed, where a piece of PZT is bonded to an enclosure with two bolts tightened inside the holes drilled in the enclosure. An impedance analyzer is used to acquire the admittance signatures of the PZT. Root mean square deviation (RMSD) is employed to associate the change in concrete strength with changes in the PZT admittance signatures. The results show that the reusable setup is able to effectively monitor the initial hydration of concrete and the structural health. It can also be detached from the concrete for future re-use. PMID:22399929

A reusable PZT transducer for monitoring initial hydration and structural health of concrete.

Science.gov (United States)

Yang, Yaowen; Divsholi, Bahador Sabet; Soh, Chee Kiong

2010-01-01

During the construction of a concrete structure, strength monitoring is important to ensure the safety of both personnel and the structure. Furthermore, to increase the efficiency of in situ casting or precast of concrete, determining the optimal time of demolding is important for concrete suppliers. Surface bonded lead zirconate titanate (PZT) transducers have been used for damage detection and parameter identification for various engineering structures over the last two decades. In this work, a reusable PZT transducer setup for monitoring initial hydration of concrete and structural health is developed, where a piece of PZT is bonded to an enclosure with two bolts tightened inside the holes drilled in the enclosure. An impedance analyzer is used to acquire the admittance signatures of the PZT. Root mean square deviation (RMSD) is employed to associate the change in concrete strength with changes in the PZT admittance signatures. The results show that the reusable setup is able to effectively monitor the initial hydration of concrete and the structural health. It can also be detached from the concrete for future re-use.

Topology optimization of reinforced concrete structures considering control of shrinkage and strength failure

DEFF Research Database (Denmark)

Luo, Yangjun; Wang, Michael Yu; Zhou, Mingdong

2015-01-01

To take into account the shrinkage effect in the early stage of Reinforced Concrete (RC) design, an effective continuum topology optimization method is presented in this paper. Based on the power-law interpolation, shrinkage of concrete is numerically simulated by introducing an additional design......-dependent force. Under multi-axial stress conditions, the concrete failure surface is well fitted by two Drucker-Prager yield functions. The optimization problem aims at minimizing the cost function under yield strength constraints on concrete elements and a structural shrinkage volume constraint. In conjunction...... to ensure the structural safety under the combined action of external loads and shrinkage....

Structural aging program to assess the adequacy of critical concrete components in nuclear power plants

International Nuclear Information System (INIS)

Naus, D.J.; Marchbanks, M.F.; Oland, C.B.; Arndt, E.G.

1989-01-01

The Structural Aging (SAG) Program is carried out by the Oak Ridge National Laboratory (ORNL) under sponsorship of the United States Nuclear Regulatory Commission (USNRC). The Program has evolved from preliminary studies conducted to evaluate the long-term environmental challenges to light-water reactor safety-related concrete civil structures. An important conclusion of these studies was that a damage methodology, which can provide a quantitative measure of a concrete structure's durability with respect to potential future requirements, needs to be developed. Under the SAG Program, this issue is being addressed through: establishment of a structural materials information center, evaluation of structural component assessment and repair technologies, and development of a quantitative methodology for structural aging determinations. Progress to date of each of these activities is presented as well as future plans. 7 refs., 5 figs

Analyses of Concrete Structures Exposed to Fire

DEFF Research Database (Denmark)

Hertz, Kristian

The text book contains the data and methods necessary for fire safety design of concrete constructions. The methods relate to standard fire as well as to any time of any other fire course.Material data are presented for concretes exposed to fire, and calculation methods are given for the ultimate...... bending capacity of beams and slabs, the ultimate shear capacity of beams, for the instability of columns and walls and for the deflection of prestressed and non-prestressed beams, slabs, walls and columns.All methods have been derived and compared to tests by Kristian Hertz....

Offshore concrete structures

International Nuclear Information System (INIS)

Lamas Pardo, M.; Carral Couce, L. M.

2011-01-01

In the offshore industry there are two possible materials for the construction of the hull of a structure; the steel and concrete, with the first one widely used until now, as in the rest of the shiphuidling industry of merchant ships, warships, etc. Materials such as aluminum, GRP or timber areused in small units with lengths lower than 100 m, and in less adverse conditions than in the offshore industry. Nevertheless, some ships/barges have been built of concrete in the past, but have been rather isolated cases which have not changed the practice in the industry. In the First and Second World War were built by the scarcity of materials, while the series of barges by Alfred A. Yee was a rare exception. Other units were also made in concrete, but almost anecdotal. Still, the behaviour of these concrete structures, especially in terms of maintenance, has been excellent. Therefore, the fact that the concrete has not had an adequate reception so far in shipbuilding, does not mean that in will not be the material best suited for the offshore industry in the future. The extra displacement and associated fuel costs in concrete ships have been found prohibitive in the past. But the loss of mobility of a concrete hull in relation to a steel hull can be perfectly offset by the advantages offered by the concrete, as the shipping and offshore industry have very different priorities. One of the main differences in these priorities is in terms of maintenance and resistance to fatigue, precisely where the concrete performs better. ships can easily be dry docked for maintenance and repair, while in the offshore platforms these works have to be done in situ so maintenance and fatigue are crucial to them. Besides these, the concrete has other advantages according to findings of several studies. And although they are interested in the conclusions that the makes as they came from people in the concrete industry, the fact that in recent years concrete offshore unit shave been built

Effects of temperature, mechanical loading and of their interactions on the permeability of structural concrete

International Nuclear Information System (INIS)

Choinska, M.

2006-11-01

Concrete permeability may influence the durability of structures indirectly by controlling the penetration rate of aggressive agents, but also directly if the structure has a confinement role, like containment vessels of nuclear power plants for instance. In the industrial background on the safety of these structures, the objective of this study is to characterize the evolution of concrete permeability under the effects of temperature and mechanical loading. The permeability tests are performed on hollow concrete cylinders, subjected to temperature up to 150 C and compressive loading up to failure. Experimental results reveal that the effects of temperature and damage may be decoupled for the estimation of permeability and enable us to propose a relation between permeability, damage and temperature. However, this relation may only be applied in the pre-peak phase as concrete remains micro-cracked. In order to overcome this limit to be able to model also permeability increase in the post-peak phase, another parameter, which is crack opening, is introduced in the relation between permeability and damage. This problem, investigated by modelling, is exploited according to two approaches. The first one is based on the definition of a matching law between existing relations of permeability evolution with damage and with crack opening. With this approach the tendencies are similar to the observed ones on the experimental results. The second approach consists in linking from a mechanical point of view damage with crack opening in order to apply the Poiseuille's law for permeability determination. Experimental validation of this approach, emerging towards a continuous model capable to reproduce permeability variations of a concrete structure, constitutes a major perspective of this work. (author)

Concrete with onyx waste aggregate as aesthetically valued structural concrete

Science.gov (United States)

Setyowati E., W.; Soehardjono, A.; Wisnumurti

2017-09-01

The utillization of Tulungagung onyx stone waste as an aggregate of concrete mixture will improve the economic value of the concrete due to the brighter color and high aesthetic level of the products. We conducted the research of 75 samples as a test objects to measure the compression stress, splits tensile stress, flexural tensile stress, elasticity modulus, porosity modulus and also studied 15 test objects to identify the concrete micro structures using XRD test, EDAX test and SEM test. The test objects were made from mix designed concrete, having ratio cement : fine aggregate : coarse aggregate ratio = 1 : 1.5 : 2.1, and W/C ratio = 0.4. The 28 days examination results showed that the micro structure of Tulungagung onyx waste concrete is similar with normal concrete. Moreover, the mechanical test results proved that Tulungagung onyx waste concretes also have a qualified level of strength to be used as a structural concrete with higher aesthetic level.

Service life and life cycle cost modelling of cathodic protection systems for concrete structures

NARCIS (Netherlands)

Polder, R.B.; Leegwater, G.; Worm, D.; Courage, W.

2012-01-01

Corrosion of reinforcing steel in concrete structures causes concrete cracking, steel diameter reduction and eventually loss of safety. In infrastructure this is mainly due to penetration of chloride ions from de-icing or marine salts. Conventional repair means heavy, labour intensive and costly

The use of concrete-filled steel structures for modular construction of advanced reactors

International Nuclear Information System (INIS)

Braverman, J.; Morante, R.; Hofmayer, C.; Graves, H.

1997-01-01

Modular construction techniques have been successfully used in a number of industries, both domestically and internationally. Recently, the use of structural modules has been proposed for advanced nuclear power plants. This paper presents the results of a research program which evaluated the use of modular construction for safety-related structures in advanced nuclear power plant designs. The research program included review of current modular construction technology, development of licensing review criteria for modular construction, and initial validation of currently available analytical techniques applied to concrete-filled steel structural modules

Evaluation of aged concrete structures for continued service in nuclear power plants

International Nuclear Information System (INIS)

Naus, D.J.; Marchbanks, M.F.; Arndt, E.G.

1988-01-01

Results are summarized of a study on concrete component aging and its significance relative to continued service of nuclear power plants (NPPs) beyond the initial period for which they were granted operating licenses. Progress is presented of a second study being conducted to identify and provide acceptance criteria for structural safety issues which the USNRC staff will need to address when applications are submitted for continued service of NPPs. Major activities under this program include: development of a materials property data base, establishment of structural component assessment and repair procedures, and development of a methodology for determination of structural reliability

Structural Response to Blast Loading: The Effects of Corrosion on Reinforced Concrete Structures

Directory of Open Access Journals (Sweden)

Hakan Yalciner

2014-01-01

Full Text Available Structural blast design has become a necessary part of the design with increasing terrorist attacks. Terrorist attacks are not the one to make the structures important against blast loading where other explosions such as high gas explosions also take an important place in structural safety. The main objective of this study was to verify the structural performance levels under the impact of different blast loading scenarios. The blast loads were represented by using triangular pulse for single degree of freedom system. The effect of blast load on both corroded and uncorroded reinforced concrete buildings was examined for different explosion distances. Modified plastic hinge properties were used to ensure the effects of corrosion. The results indicated that explosion distance and concrete strength were key parameters to define the performance of the structures against blast loading.

Factor Structure of the Piagetian Stage of Concrete Operations.

Science.gov (United States)

Klausmeier, Herbert J.; Sipple, Thomas S.

1982-01-01

The Piagetian developmental stage of concrete operational thought and the theoretical groupement structures underlying children's performance of 12 concrete operations tasks are discussed. Tasks were shown to develop in five related sets. Three factor structures were found in this longitudinal study. (Author/CM)

The study on the mechanical characteristics of concrete of nuclear reactor containment structure

International Nuclear Information System (INIS)

Jung, W. S.; Kwon, K. J.; Cho, M. S.; Song, Y. C.

2000-01-01

Reactor containment structure of nuclear power plant designed by prestressed concrete causes time-dependent prestress loss due to the mechanical characteristics of concrete. Prestress loss strongly affects to the safety factor of structure under the circumstances of designing, construction and inspection. Thus, this study is to investigate the mechanical characteristics of reactor containment concrete structure of Yonggwang No. 5 and 6. In this study, the compressive strength, modulus of elasticity, poisson's ratio and creep test followed by ASTM code are performed to investigate the mechanical characteristics of concrete made by V type cement. Additionally, since creep causes more time-dependent prestress loss than the other, the measurement value from the creep test is compared with the results from the creep prediction equations by KSCE, JSCE, Hansen, ACI and CEB-FIP model for the effective application. Hereafter, the results of this study may enable to assist the calculation effective stress considering time-dependent prestress loss of the prestressed concrete structures

Inspection of Nuclear Power Plant Structures - Overview of Methods and Related Applications

International Nuclear Information System (INIS)

Naus, Dan J.

2009-01-01

The objectives of this limited study were to provide an overview of the methods that are available for inspection of nuclear power plant reinforced concrete and metallic structures, and to provide an assessment of the status of methods that address inspection of thick, heavily-reinforced concrete and inaccessible areas of the containment metallic pressure boundary. In meeting these objectives a general description of nuclear power plant safety-related structures was provided as well as identification of potential degradation factors, testing and inspection requirements, and operating experience; methods for inspection of nuclear power plant reinforced concrete structures and containment metallic pressure boundaries were identified and described; and applications of nondestructive evaluation methods specifically related to inspection of thick-section reinforced concrete structures and inaccessible portions of containment metallic pressure boundaries were summarized. Recommendations are provided on utilization of test article(s) to further advance nondestructive evaluation methods related to thick-section, heavily-reinforced concrete and inaccessible portions of the metallic pressure boundary representative of nuclear power plant containments. Conduct of a workshop to provide an update on applications and needed developments for nondestructive evaluation of nuclear power plant structures would also be of benefit.

Inspection of Nuclear Power Plant Structures - Overview of Methods and Related Applications

Energy Technology Data Exchange (ETDEWEB)

Naus, Dan J [ORNL

2009-05-01

The objectives of this limited study were to provide an overview of the methods that are available for inspection of nuclear power plant reinforced concrete and metallic structures, and to provide an assessment of the status of methods that address inspection of thick, heavily-reinforced concrete and inaccessible areas of the containment metallic pressure boundary. In meeting these objectives a general description of nuclear power plant safety-related structures was provided as well as identification of potential degradation factors, testing and inspection requirements, and operating experience; methods for inspection of nuclear power plant reinforced concrete structures and containment metallic pressure boundaries were identified and described; and applications of nondestructive evaluation methods specifically related to inspection of thick-section reinforced concrete structures and inaccessible portions of containment metallic pressure boundaries were summarized. Recommendations are provided on utilization of test article(s) to further advance nondestructive evaluation methods related to thick-section, heavily-reinforced concrete and inaccessible portions of the metallic pressure boundary representative of nuclear power plant containments. Conduct of a workshop to provide an update on applications and needed developments for nondestructive evaluation of nuclear power plant structures would also be of benefit.

Analysis of time-dependent reliability of degenerated reinforced concrete structure

Directory of Open Access Journals (Sweden)

Zhang Hongping

2016-07-01

Full Text Available Durability deterioration of structure is a highly random process. The maintenance of degenerated structure involves the calculation of the reliability of time-dependent structure. This study introduced reinforced concrete structure resistance decrease model and related statistical parameters of uncertainty, analyzed resistance decrease rules of corroded bending element of reinforced concrete structure, and finally calculated timedependent reliability of the corroded bending element of reinforced concrete structure, aiming to provide a specific theoretical basis for the application of time-dependent reliability theory.

Structural evaluations of existing underground reinforced concrete tanks for radioactive waste storage

International Nuclear Information System (INIS)

Vollert, F.R.

1979-10-01

Structural integrity evaluations are being conducted for underground, steel-lined reinforced concrete tanks for storing radioactive wastes. The tanks sustain large soil overburden loads and elevated temperatures from the waste for long time periods. The evaluations include laboratory experiments to determine the long-term effects of elevated temperatures on the elastic properties of concrete, and to estimate the effect of the waste chemicals on concrete durability. Available concrete samples from the tanks were also tested to determine the quality of the concrete in the tanks and for comparison with the laboratory data. Finite element, nonlinear, time-dependent analyses are performed to show the thermal creep, cracking, and stresses occurring in the concrete tanks due to the service conditions. Ultimate load analyses are made to assess the safety margin in the tanks. Finally, seismic analyses of a tank in the stressed condition due to the soil and thermal loadings were conducted to determine that the structure has sufficient reserve capacity to withstand 0.25 g earthquake accelerations

THE STUDY ON THE DURABILITY OF SUBMERGED STRUCTURE DISPLACEMENT DUE TO CONCRETE FAILURE

Directory of Open Access Journals (Sweden)

M. Mohd

2016-09-01

Full Text Available Concrete structures that exposed to marine environments are subjected to multiple deterioration mechanisms. An overview of the existing technology for submerged concrete, pressure resistant, concrete structures which related such as cracks, debonds, and delamination are discussed. Basic knowledge related to drowning durability such as submerged concrete structures in the maritime environment are the durability of a concrete and the ability to resist to weathering, chemical attack, abrasion or other deterioration processes. The measuring techniques and instrumentation for geometrical monitoring of submerged structural displacements have traditionally been categorized into two groups according to the two main groups, namely as geodetic surveying and geotechnical structural measurements of local displacements. This paper aims to study the durability of submerged concrete displacement and harmful effects of submerged concrete structures.

Sodium concrete reaction - Structural considerations

International Nuclear Information System (INIS)

Ferskakis, G.N.

1984-01-01

An overview of the sodium concrete reaction phenomenon, with emphasis on structural considerations, is presented. Available test results for limestone, basalt, and magnetite concrete with various test article configurations are reviewed. Generally, tests indicate reaction is self limiting before all sodium is used. Uncertainties, however, concerning the mechanism for penetration of sodium into concrete have resulted in different theories about a reaction model. Structural behavior may be significant in the progression of the reaction due to thermal-structuralchemical interactions involving tensile cracking, compressive crushing, or general deterioration of concrete and the exposure of fresh concrete surfaces to react with sodium. Structural behavior of test articles and potential factors that could enhance the progression of the reaction are discussed

A Simple Demonstration of Concrete Structural Health Monitoring Framework

Energy Technology Data Exchange (ETDEWEB)

Mahadevan, Sankaran [Idaho National Lab. (INL), Idaho Falls, ID (United States); Agarwal, Vivek [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cai, Guowei [Idaho National Lab. (INL), Idaho Falls, ID (United States); Nath, Paromita [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bao, Yanqing [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bru Brea, Jose Maria [Idaho National Lab. (INL), Idaho Falls, ID (United States); Koester, David [Idaho National Lab. (INL), Idaho Falls, ID (United States); Adams, Douglas [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kosson, David [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2015-03-01

Assessment and management of aging concrete structures in nuclear power plants require a more systematic approach than simple reliance on existing code margins of safety. Structural health monitoring of concrete structures aims to understand the current health condition of a structure based on heterogeneous measurements to produce high confidence actionable information regarding structural integrity that supports operational and maintenance decisions. This ongoing research project is seeking to develop a probabilistic framework for health diagnosis and prognosis of aging concrete structures in a nuclear power plant subjected to physical, chemical, environment, and mechanical degradation. The proposed framework consists of four elements—damage modeling, monitoring, data analytics, and uncertainty quantification. This report describes a proof-of-concept example on a small concrete slab subjected to a freeze-thaw experiment that explores techniques in each of the four elements of the framework and their integration. An experimental set-up at Vanderbilt University’s Laboratory for Systems Integrity and Reliability is used to research effective combination of full-field techniques that include infrared thermography, digital image correlation, and ultrasonic measurement. The measured data are linked to the probabilistic framework: the thermography, digital image correlation data, and ultrasonic measurement data are used for Bayesian calibration of model parameters, for diagnosis of damage, and for prognosis of future damage. The proof-of-concept demonstration presented in this report highlights the significance of each element of the framework and their integration.

STRUCTURAL PERFORMANCE OF DEGRADED REINFORCED CONCRETE MEMBERS

International Nuclear Information System (INIS)

Braverman, J.I.; Miller, C.A.; Ellingwood, B.R.; Naus, D.J.; Hofmayer, C.H.; Bezler, P.; Chang, T.Y.

2001-01-01

This paper describes the results of a study to evaluate, in probabilistic terms, the effects of age-related degradation on the structural performance of reinforced concrete members at nuclear power plants. The paper focuses on degradation of reinforced concrete flexural members and shear walls due to the loss of steel reinforcing area and loss of concrete area (cracking/spalling). Loss of steel area is typically caused by corrosion while cracking and spalling can be caused by corrosion of reinforcing steel, freeze-thaw, or aggressive chemical attack. Structural performance in the presence of uncertainties is depicted by a fragility (or conditional probability of failure). The effects of degradation on the fragility of reinforced concrete members are calculated to assess the potential significance of various levels of degradation. The fragility modeling procedures applied to degraded concrete members can be used to assess the effects of degradation on plant risk and can lead to the development of probability-based degradation acceptance limits

Loading functions generated by solid explosive detonations inside concrete containment structures

International Nuclear Information System (INIS)

Freund, H.W.; Schumann, S.; Rischbieter, F.; Schmitz, C.

1989-01-01

Partial dismantling of concrete structures by controlled blasting is being considered for nuclear power reactor decommissioning /1,2/. Quantitative prediction of both the desired destructive effects and the side effects caused by the dynamic load is based on knowledge of the time dependent forces acting on the structure, availability of data abut the dynamic material properties, realistic structural models. This work describes investigations performed to obtain time dependent forces for the case where solid explosive charges embedded into concrete are being detonated. The resulting multi component loading function is shown to constitute a set of input data for pre-test safety calculations of the building vibrational response

Analysis of FRP bars used as reinforcement in concrete structures

Directory of Open Access Journals (Sweden)

Kinga Brózda

2016-09-01

Full Text Available In the design and construction of building and engineering structures, it is of utmost importance to provide their reliability and safety. The use of FRP (Fiber Reinforced Polymers bars as reinforcement of structural concrete elements could help reducing the typical defects of reinforced concrete and increase its strength parameters. In the paper the selected FRP bar characteristic properties are presented and advantages derived therefrom are specified. Furthermore, the most commonly used in construction types of FRP bars, depending on the raw material used during the production process are listed. In addition, the possibility of recycling of elements reinforced with FRP bars is presented and compared with traditional reinforced concrete (reinforced with steel bars. The production method of FRP bars (pultrusion is shown. Moreover, the advantages and disadvantages of using this method are discussed.

Durability of fibre reinforced concrete structures

DEFF Research Database (Denmark)

Hansen, Ernst Jan De Place; Hansen, Kurt Kielsgaard

1996-01-01

The planned research will indicate, whether fibre reinforced concrete has better or worse durability than normal concrete. Durability specimens will be measured on cracked as well as uncracked specimens. Also the pore structure in the concrete will be characterized.Keywords: Fibre reinforced...... concrete, durability, pore structure, mechanical load...

Seismic fragility of reinforced concrete structures and components for application to nuclear facilities

International Nuclear Information System (INIS)

Gergely, P.

1984-09-01

The failure and fragility analyses of reinforced concrete structures and elements in nuclear reactor facilities within the Seismic Safety Margins Research Program (SSMRP) at the Lawrence Livermore National Laboratory are evaluated. Uncertainties in material modeling, behavior of low shear walls, and seismic risk assessment for nonlinear response receive special attention. Problems with ductility-based spectral deamplification and prediction of the stiffness of reinforced concrete walls at low stress levels are examined. It is recommended to use relatively low damping values in connection with ductility-based response reductions. The study of static nonlinear force-deflection curves is advocated for better nonlinear dynamic response predictions. Several details of the seismic risk analysis of the Zion plant are also evaluated. 73 references

Data on optimum recycle aggregate content in production of new structural concrete.

Science.gov (United States)

Paul, Suvash Chandra

2017-12-01

This data presented herein are the research summary of "mechanical behavior and durability performance of concrete containing recycled concrete aggregate" (Paul, 2011) [1]. The results reported in this article relate to an important parameter of optimum content of recycle concrete aggregate (RCA) in production of new concrete for both structural and non-structural applications. For the purpose of the research various types of physical, mechanical and durability tests are performed for concrete made with different percentages of RCA. Therefore, this data set can be a great help of the readers to understand the mechanism of RCA in relates to the concrete properties.

Evaluation of aged concrete structures for continued service in nuclear power plants

International Nuclear Information System (INIS)

Naus, D.J.; Marchbanks, M.F.; Arndt, E.G.

1988-01-01

Results are summarized of a study on concrete component aging and its significance relative to continued service of nuclear power plants (NPPs) beyond the initial period for which they were granted operating licenses. Progress is presented of a second study being conducted to identify and provide acceptance criteria for structural safety issues which the USNRC staff will need to address when applications are submitted for continued service of NPPs. Major activities under this program include: development of a materials property data base, establishment of structural component assessment and repair procedures, and development of a methodology for determination of structural reliability. 19 refs., 5 figs., 3 tabs

Basic principles of concrete structures

CERN Document Server

Gu, Xianglin; Zhou, Yong

2016-01-01

Based on the latest version of designing codes both for buildings and bridges (GB50010-2010 and JTG D62-2004), this book starts from steel and concrete materials, whose properties are very important to the mechanical behavior of concrete structural members. Step by step, analysis of reinforced and prestressed concrete members under basic loading types (tension, compression, flexure, shearing and torsion) and environmental actions are introduced. The characteristic of the book that distinguishes it from other textbooks on concrete structures is that more emphasis has been laid on the basic theories of reinforced concrete and the application of the basic theories in design of new structures and analysis of existing structures. Examples and problems in each chapter are carefully designed to cover every important knowledge point. As a basic course for undergraduates majoring in civil engineering, this course is different from either the previously learnt mechanics courses or the design courses to be learnt. Compa...

Reliability of containment and safety-related structures

International Nuclear Information System (INIS)

Nessim, M.A.

1995-09-01

A research program on Reliability of Containment and Safety-related Structures has been developed and is described in this document. This program is designed to support AECB's regulatory activities aimed at ensuring the safety of these structures. These activities include evaluating submissions by operators and requesting special assessments when necessary. The results of the proposed research will also be useful in revising and enhancing the CSA design standards for containment and safety-related structures. The process of developing the research program started with an information collection and review phase. The sources of information included C-FER's previous work in the area, various recent research publications, regulatory documents and relevant design standards, and a detailed discussion with AECB staff. The second step was to outline the process of reliability evaluation, and identify the required models and parameters. Comparison between the required and available information was used to identify gaps in the state-of-the-art, and the research program was designed to fill these gaps. The program is organized in four major topics, namely: development of an approach for reliability analysis; compilation and development of the required analysis tools; application to specific problems related to design, assessment, maintenance and testing of structures; and testing and validation. It is suggested that the program should be supported by an on-going process of communication and consultation between AECB staff and industry experts. This will lend credibility to the results and facilitate their future application. (author). 1 fig

Experimental investigation of the relation between damage at the concrete-steel interface and initiation of reinforcement corrosion in plain and fibre reinforced concrete

DEFF Research Database (Denmark)

Michel, Alexander; Solgaard, Anders Ole Stubbe; Pease, Bradley Justin

2013-01-01

Cracks in covering concrete are known to hasten initiation of steel corrosion in reinforced concrete structures. To minimise the impact of cracks on the deterioration of reinforced concrete structures, current approaches in (inter)national design codes often limit the concrete surface crack width....... Recent investigations however, indicate that the concrete-reinforcement interfacial condition is a more fundamental criterion related to reinforcement corrosion. This work investigates the relation between macroscopic damage at the concrete-steel interface and corrosion initiation of reinforcement...... embedded in plain and fibre reinforced concrete. Comparisons of experimental and numerical results indicate a strong correlation between corrosion initiation and interfacial condition....

Economic effects of full corrosion surveys for aging concrete structures

NARCIS (Netherlands)

Polder, R.B.; Peelen, W.H.A.; Raupach, M.; Reichling, K.

2013-01-01

This paper investigates the economic effects of full corrosion surveys of concrete structures. The background is that the existing concrete infrastructure is aging, while being exposed to aggressive influences, which increases the occurrence of corrosion and related concrete damage over time. The

Concrete structural analysis tools and properties for Hanford site waste tank evaluation

International Nuclear Information System (INIS)

Moore, C.J.; Peterson, W.S.; Winkel, B.V.; Weiner, E.O.

1995-09-01

As Hanford Site Contractors address maintenance and future structural demands on nuclear waste tanks built as early as 1943, it is necessary to address their current safety margins and ensure safe margins are maintained. Although the current civil engineering practice has building codes for reinforced concrete design guidelines, the tanks were not constructed to today's building codes and future demands potentially result in loads and modifications to the tanks that are outside the original design basis and current practice. The Hanford Site engineering staff has embraced nonlinear finite-element modeling of concrete in an effort to obtain a more accurate understanding of the actual tank margins. This document brings together and integrates past Hanford Site nonlinear reinforced concrete analysis methods, past Hanford Site concrete testing, public domain research testing, and current concrete research directions. This document, including future revisions, provides the structural engineering overview (or survey) for a consistent, accurate approach to nonlinear finite-element modeling of reinforced concrete for Hanford Site waste storage tanks. This report addresses concrete strength and modulus degradation with temperature, creep, shrinkage, long-term sustained loads, and temperature degradation of rebar and concrete bonds. Recommendations are given for parameter studies and evaluation techniques for review of nonlinear finite-element analysis of concrete

Risk-targeted safety distance of reinforced concrete buildings from natural-gas transmission pipelines

International Nuclear Information System (INIS)

Russo, Paola; Parisi, Fulvio

2016-01-01

Natural-gas pipeline accidents mostly result in major damage even to buildings located far away. Therefore, proper safety distances should be observed in land use planning to ensure target safety levels for both existing and new buildings. In this paper, a quantitative risk assessment procedure is presented for the estimation of the annual probability of direct structural damage to reinforced concrete buildings associated with high-pressure natural-gas pipeline explosions. The procedure is based on Monte Carlo simulation and takes into account physical features of blast generation and propagation, as well as damage to reinforced concrete columns. The natural-gas jet release process and the flammable cloud size are estimated through SLAB one-dimensional integral model incorporating a release rate model. The explosion effects are evaluated by a Multi-Energy Method. Damage to reinforced concrete columns is predicted by means of pressure–impulse diagrams. The conditional probability of damage was estimated at multiple pressure–impulse levels, allowing blast fragility surfaces to be derived at different performance limit states. Finally, blast risk was evaluated and allowed the estimation of minimum pipeline-to-building safety distances for risk-informed urban planning. The probabilistic procedure presented herein may be used for performance-based design/assessment of buildings and to define the path of new natural-gas pipeline networks. - Highlights: • The safety of buildings against blast loads due to pipeline accidents is assessed. • A probabilistic risk assessment procedure is presented for natural-gas pipelines. • The annual risk of collapse of reinforced concrete building columns is evaluated. • Monte Carlo simulation was carried out considering both pipeline and column features. • A risk-targeted safety distance is proposed for blast strength class 9.

Safety risk assessment for vertical concrete formwork activities in civil engineering construction.

Science.gov (United States)

López-Arquillos, Antonio; Rubio-Romero, Juan Carlos; Gibb, Alistair G F; Gambatese, John A

2014-01-01

The construction sector has one of the worst occupational health and safety records in Europe. Of all construction tasks, formwork activities are associated with a high frequency of accidents and injuries. This paper presents an investigation of the activities and related safety risks present in vertical formwork for in-situ concrete construction in the civil engineering sector. Using the methodology of staticized groups, twelve activities and ten safety risks were identified and validated by experts. Every safety risk identified in this manner was quantified for each activity using binary methodology according to the frequency and severity scales developed in prior research. A panel of experts was selected according to the relevant literature on staticized groups. The results obtained show that the activities with the highest risk in vertical formwork tasks are: Plumbing and leveling of forms, cutting of material, handling materials with cranes, and climbing or descending ladders. The most dangerous health and safety risks detected were falls from height, cutting and overexertion. The research findings provide construction practitioners with further evidence of the hazardous activities associated with concrete formwork construction and a starting point for targeting worker health and safety programmes.

New rheological model for concrete structural analysis

International Nuclear Information System (INIS)

Chern, J.C.

1984-01-01

Long time deformation is of interest in estimating stresses of the prestressed concrete reactor vessel, in predicting cracking due to shrinkage or thermal dilatation, and in the design of leak-tight structures. Many interacting influences exist among creep, shrinkage and cracking for concrete. An interaction which researchers have long observed, is that at simultaneous drying and loading, the deformation of a concrete structure under the combined effect is larger than the sum of the shrinkage deformation of the structure at no load and the deformation of the sealed structure. The excess deformation due to the difference between observed test data and conventional analysis is regarded as the Pickett Effect. A constitutive relation explaining the Pickett Effect and other similar superposition problems, which includes creep, shrinkage (or thermal dilation), cracking, aging was developed with an efficient time-step numerical algorithm. The total deformation in the analysis is the sum of strain due to elastic deformation and creep, cracking and shrinkage with thermal dilatation. Instead of a sudden stress reduction to zero after the attainment of the strength limit, the gradual strain-softening of concrete (a gradual decline of stress at increasing strain) is considered

Mathematical Model to Predict the Permeability of Water Transport in Concrete Structure

OpenAIRE

Solomon Ndubuisi Eluozo

2013-01-01

Mathematical model to predict the permeability of water transport in concrete has been established, the model is to monitor the rate of water transport in concrete structure. The process of this water transport is based on the constituent in the mixture of concrete. Permeability established a relation on the influence of the micropores on the constituent that made of concrete, the method of concrete placement determine the rate of permeability deposition in concrete structure, permeability es...

Characteristics of Structural Breakdown in Plastic Concrete and ...

African Journals Online (AJOL)

Characteristics of Structural Breakdown in Plastic Concrete and Their Potentials for Quality Control. ... A typical trace has four such significant features which characterise the mix. The significance of these features are analysed in relation to the functional requirements of plastic concrete in practice. Finally, the potentials of ...

Critical Study of Corrosion Damaged Concrete Structures

OpenAIRE

Sallehuddin Shah Ayop; John Cairns

2013-01-01

Corrosion of steel reinforcement in concrete is one of the major problems with respect to the durability of reinforced concrete structures. The degradation of the structure strength due to reinforcement corrosion decreases its design life. This paper presents the literature study on the influence of the corrosion on concrete structure starting from the mechanism of the corrosion until the deterioration stage and the structural effects of corrosion on concrete structures.

Superelastic SMA–FRP composite reinforcement for concrete structures

International Nuclear Information System (INIS)

Wierschem, Nicholas; Andrawes, Bassem

2010-01-01

For many years there has been interest in using fiber-reinforced polymers (FRPs) as reinforcement in concrete structures. Unfortunately, due to their linear elastic behavior, FRP reinforcing bars are never considered for structural damping or dynamic applications. With the aim of improving the ductility and damping capability of concrete structures reinforced with FRP reinforcement, this paper studies the application of SMA–FRP, a relatively novel type of composite reinforced with superelastic shape memory alloy (SMA) wires. The cyclic tensile behavior of SMA–FRP composites are studied experimentally and analytically. Tests of SMA–FRP composite coupons are conducted to determine their constitutive behavior. The experimental results are used to develop and calibrate a uniaxial SMA–FRP analytical model. Parametric and case studies are performed to determine the efficacy of the SMA–FRP reinforcement in concrete structures and the key factors governing its behavior. The results show significant potential for SMA–FRP reinforcement to improve the ductility and damping of concrete structures while still maintaining its elastic characteristic, typical of FRP reinforcement

Nonparametric Change Point Diagnosis Method of Concrete Dam Crack Behavior Abnormality

OpenAIRE

Li, Zhanchao; Gu, Chongshi; Wu, Zhongru

2013-01-01

The study on diagnosis method of concrete crack behavior abnormality has always been a hot spot and difficulty in the safety monitoring field of hydraulic structure. Based on the performance of concrete dam crack behavior abnormality in parametric statistical model and nonparametric statistical model, the internal relation between concrete dam crack behavior abnormality and statistical change point theory is deeply analyzed from the model structure instability of parametric statistical model ...

Soft impact testing of a wall-floor-wall reinforced concrete structure

Energy Technology Data Exchange (ETDEWEB)

Vepsä, Ari, E-mail: ari.vepsa@vtt.fi; Calonius, Kim; Saarenheimo, Arja; Aatola, Seppo; Halonen, Matti

2017-01-15

Highlights: • A wall-floor-wall reinforced concrete structure was built. • The structure was subjected to three almost identical soft impact tests. • Response was measured with accelerometers, displacement sensors and strain gauges. • Modal tests was also carried out with the same structure in different conditions. • The results are meant to be used for validation of computational methods and models. - Abstract: Assessing the safety of the reactor building of a nuclear power plant against the crash of an airplane calls for valid computational tools such as finite element models and material constitutive models. Validation of such tools and models in turn calls for reliable and relevant experimental data. The problem is that such data is scarcely available. One of the aspects of such a crash is vibrations that are generated by the impact. These vibrations tend to propagate from the impact point to the internal parts of the building. If strong enough, these vibrations may cause malfunction of the safety-critical equipment inside the building. To enable validation of computational models for this type of behaviour, we have conducted a series of three tests with a wall-floor-wall reinforced concrete structure under soft impact loading. The response of the structure was measured with accelerometers, displacement sensors and strain gauges. In addition to impact tests, the structure was subjected to modal tests under different conditions. The tests yielded a wealth of useful data for validation of computational models and better understanding about shock induced vibration physics especially in reinforced concrete structures.

Prediction of concrete strength in massive structures

International Nuclear Information System (INIS)

Sakamoto, T.; Makino, H.; Nakane, S.; Kawaguchi, T.; Ohike, T.

1989-01-01

Reinforced concrete structures of a nuclear power plant are mostly of mass concrete with cross-sectional dimensions larger than 1.0 m. The temperature of concrete inside after placement rises due to heat of hydration of cement. It is well known that concrete strengths of mass concrete structure subjected to such temperature hysteresis are generally not equal to strengths of cylinders subjected to standard curing. In order to construct a mass concrete structure of high reliability in which the specified concrete strength is satisfied by the specified age, it is necessary to have a thorough understanding of the strength gain property of concrete in the structure and its relationships with the water-cement ratio of the mix, strength of standard-cured cylinders and the internal temperature hysteresis. This report describes the result of studies on methods of controlling concrete strength in actual construction projects

Structural behavior of reinforced concrete structures at high temperatures

International Nuclear Information System (INIS)

Yamazaki, N.; Yamazaki, M.; Mochida, T.; Mutoh, A.; Miyashita, T.; Ueda, M.; Hasegawa, T.; Sugiyama, K.; Hirakawa, K.; Kikuchi, R.; Hiramoto, M.; Saito, K.

1995-01-01

To establish a method to predict the behavior of reinforced concrete structures subjected simultaneously to high temperatures and external loads, this paper presents the results obtained in several series of tests carried out recently in Japan. This paper reports on the material properties of concrete and steel bars under high temperatures. It also considers the heat transfer properties of thick concrete walls under transient high temperatures, and the structural behavior of reinforced concrete beams subjected to high temperatures. In the tests, data up to 800 C were obtained for use in developing a computational method to estimate the non-linear behavior of reinforced concrete structures exposed to high temperatures. (orig.)

The effect of alkali-aggregate reaction on concrete bridge structures

Directory of Open Access Journals (Sweden)

Grković Slobodan

2016-01-01

Full Text Available This paper shows contemporary issues related to unfavorable effects of concrete alkali-aggregate reaction (AAR on concrete bridge structures (CBS. Although AAR unfavorable effects on CBS were identified in 1930s, it was much later that AAR was acknowledged as one of the most pronounced deterioration processes in concrete that results in damages to concrete structures. There are two basic forms of AAR: alkali-silica reaction (ASR and alkali-carbonate reaction (ACR. Compared to ACR, ASR is more prominent, especially in certain geographic parts of the world. Damages to concrete caused by the ASR have negative effect primarily on usability and durability of CBS, what is followed by the decrease in load bearing capacity of structural components and reliability of the whole structure, shortening of service life (SL and costly repairs. For CBS, simultaneous occurrence of ASR and other degradation processes in concrete, such as those caused by the presence of moisture, water, temperature variations and use of deicing salt during winter, are especially damaging. Based on review of the most relevant literature, this paper is focused on mechanisms and mechanisms factors of the ASR, related contemporary research and reliability design guidelines for CBS that are based on prevention of the initiation and development of ASR.

Resistance ability evaluation of safety-related structures for the simulated aircraft accident

Energy Technology Data Exchange (ETDEWEB)

Kim, Young Jin; Kim, Sung Woon; Choi, Jang Kyu [Daewoo E and C Co., Ltd., Suwon (Korea, Republic of)] (and others)

2003-03-15

Aircraft accidents on nuclear safety-related structures can cause severe damage to the safety of NPP(Nuclear Power Plant)s. To assess the safety of nuclear safety-related structures, the local damage and the dynamic response of global structures should be investigated together. This study have compared several local damage assessment formulas suggested for aircraft as an impactor, and have set the assessment system of local damage for impact-proof design of NPP containment buildings. And the local damage of nuclear safety-related structures in operation in Korea for commercial aircraft as impactor have been estimated. Impact load-time functions of the aircraft crash have been decided to assessment the safety of nuclear safety-related structures against the intentional colliding of commercial aircraft. Boeing 747 and Boeing 767 is selected as target aircraft based on the operation frequencies and weights. Comparison of the fire analysis methods showed that the method considering heat convection and radiation is adequate for the temperature analysis of the aircraft fuel fire. Finally, the study covered the analysis of the major structural drawings and design drawings with which three-dimensional finite element model analysis is expected to be performed.

Structural Materials: 95. Concrete

International Nuclear Information System (INIS)

Naus, Dan J.

2012-01-01

Nuclear power plant concrete structures and their materials of construction are described, and their operating experience noted. Aging and environmental factors that can affect the durability of the concrete structures are identified. Basic components of a program to manage aging of these structures are identified and described. Application of structural reliability theory to devise uniform risk-based criteria by which existing facilities can be evaluated to achieve a desired performance level when subjected to uncertain demands and to quantify the effects of degradation is outlined. Finally, several areas are identified where additional research is desired.

Design of ultra-lightweight concrete: towards monolithic concrete structures

Directory of Open Access Journals (Sweden)

Yu Qing Liang

2014-04-01

Full Text Available This study addresses the development of ultra-lightweight concrete. A moderate strength and an excellent thermal conductivity of the lightweight concrete are set as the design targets. The designed lightweight aggregates concrete is targeted to be used in monolithic concrete façade structure, performing as both load bearing element and thermal insulator. The developed lightweight concrete shows excellent thermal properties, with a low thermal conductivity of about 0.12 W/(m·K; and moderate mechanical properties, with 28-day compressive strengths of about 10-12 N/mm . This combination of values exceeds, to the researchers’ knowledge, the performance of all other lightweight building materials. Furthermore, the developed lightweight concrete possesses excellent durability properties.

A survey of the mechanical properties of concrete for structural purposes prepared on construction sites

Directory of Open Access Journals (Sweden)

R. R. J. RIBEIRO

Full Text Available Abstract This paper aims to study the concrete dosage conditions for structural purposes in construction sitesl, and the impacts of non-compliance of structural concrete for structural safety, having as study case the city of Angicos / RN. Were analyzed the dynamic elasticity modulus, static elasticity modulus and the compressive strength of concrete samples. Was conducted to collect the survey data, a field research aiming to gather information about dosage of concrete used in the works, as well as the collection of cylindrical specimens of 150 mm diameter by 300 mm of height, prepared according to practice of those professionals. The study indicated a clear necessity to reflection on the subject, since there is no concern, or even, a lack of knowledge by the interviewed professionals regarding the care and procedures necessary for the production of concrete with satisfactory quality, once at least 50% of evaluated construction sites presented compressive strength lower than 20 MPa, minimal strength to structural concrete, as recommended by ABNT-NBR 6118:2014.

Sustainability and durability analysis of reinforced concrete structures

Science.gov (United States)

Horáková, A.; Broukalová, I.; Kohoutková, A.; Vašková, J.

2017-09-01

The article describes an assessment of reinforced concrete structures in terms of durability and sustainable development. There is a short summary of findings from the literature on evaluation methods for environmental impacts and also about corrosive influences acting on the reinforced concrete structure, about factors influencing the durability of these structures and mathematical models describing the corrosion impacts. Variant design of reinforced concrete structure and assessment of these variants in terms of durability and sustainability was performed. The analysed structure was a concrete ceiling structure of a parking house for cars. The variants differ in strength class of concrete and thickness of concrete slab. It was found that in terms of durability and sustainable development it is significantly preferable to use higher class of concrete. There are significant differences in results of concrete structures durability for different mathematical models of corrosive influences.

Behaviour of concrete structures in fire

Directory of Open Access Journals (Sweden)

Fletcher Ian A.

2007-01-01

Full Text Available This paper provides a "state-of-the-art" review of research into the effects of high temperature on concrete and concrete structures, extending to a range of forms of construction, including novel developments. The nature of concrete-based structures means that they generally perform very well in fire. However, concrete is fundamentally a complex material and its properties can change dramatically when exposed to high temperatures. The principal effects of fire on concrete are loss of compressive strength, and spalling - the forcible ejection of material from the surface of a member. Though a lot of information has been gathered on both phenomena, there remains a need for more systematic studies of the effects of thermal exposures. The response to realistic fires of whole concrete structures presents yet greater challenges due to the interactions of structural elements, the impact of complex small-scale phenomena at full scale, and the spatial and temporal variations in exposures, including the cooling phase of the fire. Progress has been made on modeling the thermomechanical behavior but the treatment of detailed behaviors, including hygral effects and spalling, remains a challenge. Furthermore, there is still a severe lack of data from real structures for validation, though some valuable insights may also be gained from study of the performance of concrete structures in real fires. .

Modeling and analysis of aging behavior of concrete structures in nuclear power plants

Energy Technology Data Exchange (ETDEWEB)

Rashid, J.Y.R.; James, R.J.; Dunham, R.S. [ANATECH (United States)

2011-07-01

As nuclear power plants approach the end of their original design life and begin to transition to the life extension phase, consideration has to be given to the effects of structural aging when evaluating the extended operation of reinforced or pre-stressed concrete structures. The behavior of concrete is highly nonlinear, having low tensile strength, shear stiffness and strength that depend on crack widths, and a confinement-dependent compressive elasto-plasticity. A concrete material model is described having the appropriate capabilities required for evaluating structural aging. The model treats reinforced concrete as a three-phase composite: plain concrete material as a three-dimensional continuum phase, steel reinforcement (rebar) as a uni-directional phase, and a rebar-concrete interaction phase. Structural aging is defined as the combined effects of time dependent material properties degradation and service induced changes in loading and operational conditions. Three broad categories of structural aging, and the interaction between them, are considered: 1) Aging effects due to expected time dependent changes in material properties, 2) Aging effects due to unexpected time dependent material degradation, and 3) Aging effects due to operational environment and loading. Example analyses are presented which illustrate the value of using advanced modeling and simulation in evaluating expected and unusual structural behavior. This is particularly important for safety structures that are approaching the end of their design life and are facing the prospect of re-licensing for extended operation

Structural Concrete, Science into Practice

NARCIS (Netherlands)

Bruggeling, A.S.G.

1987-01-01

There is a need for a more rational and unified approach to all types of concrete structure, reinforced of prestressed. The first chapter explains in a historical review why the approach of reinforced concrete and that of prestressed concrete have hitherto been very different. In outlining the

Structural evaluation and analysis under normal conditions for spent fuel concrete storage cask

Energy Technology Data Exchange (ETDEWEB)

Moon, Taechul; Baeg, Changyeal; Yoon, Sitae [Korea Radioactive waste Management Agency, Daejeon (Korea, Republic of); Jung, Insoo [Korea Nuclear Engineering and Service Co., Daejeon (Korea, Republic of)

2014-05-15

The purpose of this paper is the verification of stabilities of the structural elements that influence the safety of a concrete storage cask. The evaluation results were reviewed with respect to every design criterion, in terms of whether the results satisfy the criteria, provided by 10CFR 72 and NUREG-1536. The basic information on the design is partially explained in 2. Description of spent fuel storage system and the maintainability and assumptions included in the analysis were confirmed through detailed explanations of the acceptable standards, analysis model, and analysis method. ABAQUS 6.10, a widely used finite element analysis program, was used in the structural analysis. The storage cask shall maintain the sub-criticality, shielding, structural integrity, thermal capability and confinement in accordance with the requirements specified in US 10 CFR 72. The safety of storage cask is analyzed and it has been confirmed to meet the requirements of US 10 CFR 72. This paper summarizes the structural stability evaluation results of a concrete storage cask with respect to the design criteria. The evaluation results of this paper show that the maximum stress was below the allowable stress under every condition, and the concrete storage cask satisfied the design criteria.

Concrete under severe conditions. Environment and loading

International Nuclear Information System (INIS)

2007-01-01

-disciplinary ideas in order to improve the current situation. In continuity with previous CONSEC conferences, chloride ingress within concrete structures, durability performance in marine environment, and mitigation of corrosion has deserved important research effort, leading to numerous meaningful contributions. Themes of wear, fatigue resistance of concrete and concrete structures, and control of crack openings represent traditionally important durability issues, for which significant new results are provided. Moreover, with the evolution of research themes, of design and building practice and of social needs, some topics indicate a renewed and major interest of CONSEC'07 contributors: - shock and impact strength of concrete structures, in relation with natural and industrial hazards or terrorist attacks, - thermo-mechanical couplings and fire resistance of concrete structures, which represents an important industrial and safety issue, - rational accounting for chemical attacks and prevention of associated degradations, - performance-based engineering of concrete material, with a special care of durability. Sixteen papers dealing with the behaviour of concrete structures in nuclear facilities have been selected for INIS

Experimental investigation on the threshold chloride concentration for corrosion initiation in reinforced concrete structures

International Nuclear Information System (INIS)

Byung Hwan Oh; Seung Yup Jang

2005-01-01

The corrosion of steel reinforcements in concrete is of great importance in the view of safety and durability of reinforced concrete structures. This study is focused on the corrosion behavior of steel bars induced by internal chlorides in concrete. The main objective of this study is to determine the threshold chloride concentration causing depassivation and active corrosion of steel reinforcement in concrete. To examine the threshold concentration of chloride ion, the half-cell potential, the chemical composition of extracted pore solutions of concrete and the extent of corroded area of the specimens were measured. Major test variables include the added amount of chlorides in concrete, type of binder, and water-to-binder ratios. From the present comprehensive test results, the factors influencing threshold chloride concentration are investigated, and the rational ranges of threshold chloride concentration causing active corrosion of steels are proposed. The present study provides the realistic chloride limit for corrosion initiation of reinforced concrete structures, which can be used efficiently in the future technical specification. (authors)

Recycled construction and demolition concrete waste as aggregate for structural concrete

Directory of Open Access Journals (Sweden)

Ashraf M. Wagih

2013-12-01

Full Text Available In major Egyptian cities there is a surge in construction and demolition waste (CDW quantities causing an adverse effect on the environment. The use of such waste as recycled aggregate in concrete can be useful for both environmental and economical aspects in the construction industry. This study discusses the possibility to replace natural coarse aggregate (NA with recycled concrete aggregate (RCA in structural concrete. An investigation into the properties of RCA is made using crushing and grading of concrete rubble collected from different demolition sites and landfill locations around Cairo. Aggregates used in the study were: natural sand, dolomite and crushed concretes obtained from different sources. A total of 50 concrete mixes forming eight groups were cast. Groups were designed to study the effect of recycled coarse aggregates quality/content, cement dosage, use of superplasticizer and silica fume. Tests were carried out for: compressive strength, splitting strength and elastic modulus. The results showed that the concrete rubble could be transformed into useful recycled aggregate and used in concrete production with properties suitable for most structural concrete applications in Egypt. A significant reduction in the properties of recycled aggregate concrete (RAC made of 100% RCA was seen when compared to natural aggregate concrete (NAC, while the properties of RAC made of a blend of 75% NA and 25% RCA showed no significant change in concrete properties.

Periodic Safety Review of Tendon Pre-stress of Concrete Containment Building for a CA U-Type clear Power Plant

Energy Technology Data Exchange (ETDEWEB)

Joo, Kwang Ho; Lim, Woo Sang [Korea Hydro and clear Power Co., Daejeon (Korea, Republic of)

2009-10-15

Generally, as the tendon pre-stress of concrete containment buildings at nuclear power plants decreases as time passes due to the concrete creep, concrete shrinkage and the relaxation of tendon strands, the tendon pre-stress must secure the structural integrity of these buildings by maintaining its value higher than that of the designed pre-stress during the overall service life of the nuclear power plants. Moreover, if necessary, the degree of tendon pre-stress must also guarantee the structural integrity of concrete containment buildings over their lifetimes. This paper evaluated the changes in the tendon pre-stress of a concrete containment building subject to time-limited aging as an item in a periodic safety review (PSR) of Wolsong unit 1, a CANDU-type nuclear power plant to ensure that the structural integrity can be maintained until the next PSR period after the designed lifetime.

Structure formation control of foam concrete

Science.gov (United States)

Steshenko, Aleksei; Kudyakov, Aleksander; Konusheva, Viktoriya; Syrkin, Oleg

2017-01-01

The process of predetermined foam concrete structure formation is considered to be a crucial issue from the point of process control and it is currently understudied thus defining the need for additional research. One of the effective ways of structure formation control in naturally hardening foam concrete is reinforcement with dispersed fibers or introduction of plasticizers. The paper aims at studying the patterns of influence of microreinforcing and plasticizing additives on the structure and performance properties of foam concrete. Preparation of foam concrete mix has been conducted using one-step technology. The structure of modified foam concrete has been studied by means of electron microscopy. The cellular structure of foam concrete samples with the additives is homogeneous; the pores are uniformly distributed over the total volume. It has been revealed that introduction of the Neolas 5.2 plasticizer and microreinforcing fibers in the foam concrete mixture in the amount of 0.4 - 0.1 % by weight of cement leads to reduction of the average pore diameter in the range of 45.3 to 30.2 microns and the standard deviation of the pore average diameter from 23.6 to 9.2 in comparison with the sample without additive. Introduction of modifying additives has stimulated formation of a large number of closed pores. Thus porosity of conditionally closed pores has increased from 16.06 % to 34.48 %, which has lead to increase of frost resistance brand of foam concrete from F15 to F50 and to reduction of its water absorption by weight by 20 %.

Effect of high temperature on integrity of concrete containment structures

International Nuclear Information System (INIS)

Bhat, P.D.

1986-01-01

The effect of high temperature on concrete material properties and structural behavior are studied in order to relate these effects to the performance of concrete containment structures. Salient data obtained from a test program undertaken to study the behavior of a restrained concrete structure under thermal gradient loads up to its ultimate limit are described. The preliminary results indicate that concrete material properties can be considered to remain unaltered up to temperatures of 100 0 C. The presence of thermal gradients did not significantly affect the structures ultimate mechanical load capacity. Relaxation of restraint forces due to creep was found to be an important factor. The test findings are compared with the observations made in available literature. The effect of test findings on the integrity analysis of a containment structure are discussed. The problem is studied from the viewpoint of a CANDU heavy water reactor containment

Reinforced concrete structures under impact and impulsive loading: recent development, problems and trends

International Nuclear Information System (INIS)

Plauk, G.; Herter, J.

1984-01-01

Nuclear plant facilities and other reinforced concrete structures have to be regarded as to their safety in design and construction with respect to impact and impulsive loading in order to avoid serious damage to mankind and environment. The paper gives a survey on theoretical and experimental developments currently in progress, in particular regarding airplane crash. Some new results arising out of several research programs relevant to particular problems of impact loading have been reviewed and are presented. Experimental investigation for determination of material properties of plain concrete, reinforcing steel as well as steel-concrete bond under high strain-rates are treated in this paper including theoretical approaches for the respective material laws. An outline of soft missile impact tests performed on structural members, e.g. beams and plates, to determine the load deformation or fracture behaviour is given. Furthermore, numerical models and calculations to analyse structural components and structures under impact loading were discussed. (Author) [pt

Numerical analysis oriented biaxial stress-strain relation and failure criterion of plain concrete

International Nuclear Information System (INIS)

Link, J.

1975-01-01

A biaxial stress-strain relation and failure criterion is proposed, which is applicable to structural analysis methods. The formulation of material behavior of plain concrete in biaxial stress-state was developed. A nonlinear elastic, anisotropic stress-strain relation was derived with two moduli of elasticity, E 1 , E 2 and Poisson's ratios, ν 1 , ν 2 , which depend on the prevailing biaxial stress state. The stress-strain relation is valid in the whole biaxial stress field, that means with a smooth transition between the domains of tension/tension, tension/compression and compression/compression. The stress-dependent moduli E 1 , E 2 and the Poisson's ratios ν 1 , ν 2 are approximated by polynomials, trigonometrical and exponential functions. A failure criterion was defined by approximating the test results of the biaxial ultimate concrete strength with a 7th degree polynomial, which is also valid in the whole biaxial stress domain. The definition of the state of failure is given as a function of stresses as well as strains. Initial parameters of the formulation of the biaxial material behavior are the uniaxial cylindrical strength of concrete and the initial values of Young's modulus and Poisson's ratio. A simple expansion of this formulation makes it applicable not only to normal but also to light-weight concrete. Comparison of numerically calculated stress-strain curves up to the ultimate biaxial stresses which indicate the failure criteria with those obtained from tests show a very good agreement. It is shown, that the biaxial stress-strain relation can be extended for use in cases of triaxial tension/tension/compression stress state. Numerical examples of analysis of concrete slabs show the importance of incorporation of a realistic material behavior for better safety estimations

Application of concrete filled steel bearing wall to inner concrete structure fro PWR nuclear power plant

International Nuclear Information System (INIS)

Sekimoto, Hisashi; Tanaka, Mamoru; Inoue, Kunio; Fukihara, Masaaki; Akiyama, Hiroshi.

1992-01-01

'Concrete filled steel bearing wall', applied to the inner concrete structure for PWR nuclear power plant, was developed for rationalization of construction procedure at site. It was concluded through preliminary studies that this new type of wall, where concrete is placed between steel plates, is best suited for the strength members of the above structure, due to the high strength and ductility of surface steel plates and the confinement effect of filled concrete. To verify the behavior from the elastic range to the inelastic range, the ultimate strength and the failure mechanism, and to clarify experimentally the structural integrity of the inner concrete structure, which was composed of a concrete filled steel bearing wall, against seismic lateral loads, horizontal loading tests using a 1/10th scale model of the inner concrete structure for PWR nuclear power plant were conducted. As a result of the tests, the inner concrete structure composed of a concrete filled steel bearing wall appeared to have a larger load carrying capacity and a higher ductility as compared with that composed of a reinforced concrete wall. (author)

Nondestructive testing of concrete structures

International Nuclear Information System (INIS)

Rufino, Randy R.; Relunia, Estrella

1999-01-01

Nondestructive testing of concrete is highly inhomogeneous which makes it cumbersome to setup experimental procedures and analyze experimental data. However, recent research and development activities have discovered the different methods of NDT, like the electromagnetic method, ultrasonic pulse velocity test, pulse echo/impact echo test, infrared thermography, radar or short pulse radar techniques, neutron and gamma radiometry, radiography, carbonation test and half-cell potential method available for NDT of concrete structures. NDT of concrete is emerging as a useful tool for quality control and assurance. This papers also describes the more common NDT methods discussed during the two-week course on 'Nondestructive Testing of Concrete Structures', held at the Malaysian Institute for Nuclear Technology Research (MINT) in Malaysia, which was jointly organized by MINT and the International Atomic Energy Agency (IAEA)

Research on working property and early age mechanical property of self-compacting concrete used in steel-concrete structure

International Nuclear Information System (INIS)

Zhao Yongguang

2013-01-01

Background: Self-compacting concrete that has good working property is the prerequisite of steel-concrete structure. The early age mechanical property of self-compacting concrete is the important parameter when design steel-concrete structure. Purpose: This paper attempts to research the working property and early age mechanical property of self-compacting concrete. Methods: Test is used to research the working property and early age mechanical property of self-compacting concrete. Results: Self-compacting concrete that could meet the requirement of steel-concrete structure has been mixed and parameters of early age mechanical property of self-compacting concrete which is necessary for design of steel-concrete structure have been presented. Conclusions: Base on the results, this paper can guide the construction of self-compacting concrete in steel-concrete structure and the design and construction of steel-concrete structure. (author)

Model techniques for testing heated concrete structures

International Nuclear Information System (INIS)

Stefanou, G.D.

1983-01-01

Experimental techniques are described which may be used in the laboratory to measure strains of model concrete structures representing to scale actual structures of any shape or geometry, operating at elevated temperatures, for which time-dependent creep and shrinkage strains are dominant. These strains could be used to assess the distribution of stress in the scaled structure and hence to predict the actual behaviour of concrete structures used in nuclear power stations. Similar techniques have been employed in an investigation to measure elastic, thermal, creep and shrinkage strains in heated concrete models representing to scale parts of prestressed concrete pressure vessels for nuclear reactors. (author)

Safety Assessment in Installation of Precast Concrete

Directory of Open Access Journals (Sweden)

Yashrri S.N.

2014-03-01

Full Text Available This study was carried out to identify the safety aspects and the level of safety during the installation process in construction sites. A questionnaire survey and interviews were done to provide data on safety requirements in precast concrete construction. All of the interviews and the research questionnaire survey were conducted among contractors that are registered as class 1 to class 7 with the Construction Industry Development Board (CIDB and class A to class G with Pusat Khidmat Kontraktor (PKK in Penang. Returned questionnaires were analysed with the use of simple percentages and the Likert Scale analysis method to identify safety aspects of precast construction. The results indicate that the safety aspect implemented by companies involved in the precast construction process is at a good level in the safety aspect during bracing, propping, welding and grouting processes and at a very good level of safety in general aspects and safety aspects during lifting processes.

Experimental investigation of the relation between damage at the concrete-steel interface and initiation of reinforcement corrosion in plain and fibre reinforced concrete

International Nuclear Information System (INIS)

Michel, A.; Solgaard, A.O.S.; Pease, B.J.; Geiker, M.R.; Stang, H.; Olesen, J.F.

2013-01-01

Highlights: •Cracked plain and steel fibre reinforced concrete flexural beams were investigated. •“Instrumented rebars” provided location- and time-dependent corrosion measurements. •Interfacial condition can be used as a reliable indicator to quantify the risk of corrosion. •Simulated interfacial conditions are in very good agreement with all experimental observations. -- Abstract: Cracks in covering concrete are known to hasten initiation of steel corrosion in reinforced concrete structures. To minimise the impact of cracks on the deterioration of reinforced concrete structures, current approaches in (inter)national design codes often limit the concrete surface crack width. Recent investigations however, indicate that the concrete-reinforcement interfacial condition is a more fundamental criterion related to reinforcement corrosion. This work investigates the relation between macroscopic damage at the concrete-steel interface and corrosion initiation of reinforcement embedded in plain and fibre reinforced concrete. Comparisons of experimental and numerical results indicate a strong correlation between corrosion initiation and interfacial condition

Design and analyses of porous concrete for safety applications

NARCIS (Netherlands)

Agar Ozbek, A.S.

2016-01-01

In an explosion taking place close to or inside a concrete structure, apart from the dangers of the explosive itself, the hazard due to the large debris originating from the concrete structure is an important threat. Protective structures with high probability to experience such extreme loadings

Ultrasonic measurements of undamaged concrete layer thickness in a deteriorated concrete structure

NARCIS (Netherlands)

Demcenko, A.; Visser, Roy; Akkerman, Remko

2016-01-01

Ultrasonic wave propagation in deteriorated concrete structures was studied numerically and experimentally. Ultrasonic single-side access immersion pulse-echo and diffuse field measurements were performed in deteriorated concrete structures at 0.5 MHz center frequency. Numerically and experimentally

STRUCTURAL AND THERMOPHYSICAL PROPERTIES OF HARDENING CONCRETE

Directory of Open Access Journals (Sweden)

L. Krasulina

2012-01-01

Full Text Available Structural and thermophysical properties of thermally treated concrete have been studied in the paper. The paper demonstrates regularities of changes in structural and thermophysical properties of concrete during heat treatment process. It is established that stabilization of coefficient values for heat- and temperature conductivity of concrete corresponds to completion of the process pertaining to intensive formation of the material pore structure and indicates the possibility of transition from the stage of isothermal extraction to the stage of temperature decrease. The obtained results are confirmed by studies of strength growth kinetics of concrete samples.

Study on Semi-Parametric Statistical Model of Safety Monitoring of Cracks in Concrete Dams

Directory of Open Access Journals (Sweden)

Chongshi Gu

2013-01-01

Full Text Available Cracks are one of the hidden dangers in concrete dams. The study on safety monitoring models of concrete dam cracks has always been difficult. Using the parametric statistical model of safety monitoring of cracks in concrete dams, with the help of the semi-parametric statistical theory, and considering the abnormal behaviors of these cracks, the semi-parametric statistical model of safety monitoring of concrete dam cracks is established to overcome the limitation of the parametric model in expressing the objective model. Previous projects show that the semi-parametric statistical model has a stronger fitting effect and has a better explanation for cracks in concrete dams than the parametric statistical model. However, when used for forecast, the forecast capability of the semi-parametric statistical model is equivalent to that of the parametric statistical model. The modeling of the semi-parametric statistical model is simple, has a reasonable principle, and has a strong practicality, with a good application prospect in the actual project.

Hysteretic evaluation of seismic performance of normal and fiber reinforced concrete shear walls

International Nuclear Information System (INIS)

Choun, Young Sun; Hahm, Dae Gi

2012-01-01

The use of fibers in concrete or cement composites can enhance the performance of structural elements. Fibers have been used for a cement mixture to increase the toughness and tensile strength, and to improve the cracking and deformation characteristics. The addition of fibers into concrete can improve the ductility and increase the seismic resistance of concrete structures. The application of fibers to earthquake-resistant concrete structures has a major research topic. A recent study shows that an excellent seismic performance can be obtained in shear critical members constructed with high performance fiber reinforced cement composites. To increase the seismic performance of safety related concrete structures in nuclear power plants, fibers can be used. This study investigated the effect of fibers on the hysteretic behavior of a reinforced concrete (RC) shear wall by cyclic tests

Hysteretic evaluation of seismic performance of normal and fiber reinforced concrete shear walls

Energy Technology Data Exchange (ETDEWEB)

Choun, Young Sun; Hahm, Dae Gi [KAERI, Daejeon (Korea, Republic of)

2012-10-15

The use of fibers in concrete or cement composites can enhance the performance of structural elements. Fibers have been used for a cement mixture to increase the toughness and tensile strength, and to improve the cracking and deformation characteristics. The addition of fibers into concrete can improve the ductility and increase the seismic resistance of concrete structures. The application of fibers to earthquake-resistant concrete structures has a major research topic. A recent study shows that an excellent seismic performance can be obtained in shear critical members constructed with high performance fiber reinforced cement composites. To increase the seismic performance of safety related concrete structures in nuclear power plants, fibers can be used. This study investigated the effect of fibers on the hysteretic behavior of a reinforced concrete (RC) shear wall by cyclic tests.

Aseismic safety analysis of a prestressed concrete containment vessel for CPR1000 nuclear power plant

Science.gov (United States)

Yi, Ping; Wang, Qingkang; Kong, Xianjing

2017-01-01

The containment vessel of a nuclear power plant is the last barrier to prevent nuclear reactor radiation. Aseismic safety analysis is the key to appropriate containment vessel design. A prestressed concrete containment vessel (PCCV) model with a semi-infinite elastic foundation and practical arrangement of tendons has been established to analyze the aseismic ability of the CPR1000 PCCV structure under seismic loads and internal pressure. A method to model the prestressing tendon and its interaction with concrete was proposed and the axial force of the prestressing tendons showed that the simulation was reasonable and accurate. The numerical results show that for the concrete structure, the location of the cylinder wall bottom around the equipment hatch and near the ring beam are critical locations with large principal stress. The concrete cracks occurred at the bottom of the PCCV cylinder wall under the peak earthquake motion of 0.50 g, however the PCCV was still basically in an elastic state. Furthermore, the concrete cracks occurred around the equipment hatch under the design internal pressure of 0.4MPa, but the steel liner was still in the elastic stage and its leak-proof function soundness was verified. The results provide the basis for analysis and design of containment vessels.

Sustainable monitoring of concrete structures : strength and durability performance of polymer-modified self-sensing concrete

OpenAIRE

Torgal, Fernando Pacheco; Gonzalez, J.; Jalali, Said

2012-01-01

Concrete structures all over the world are reaching the end of their service life sooner than expected. This is due to the fact that ordinary Portland cement-based concrete deteriorates under environmental actions and also that structural inspections and conservation actions are expensive. Besides, as they consume energy and non-renewable resources, they have negative environmental impacts. Self-sensing concrete provides an alternative way of monitoring concrete-reinforced structures...

Global models for studying the non linear behavior of structures. Application to reinforced concrete structures

International Nuclear Information System (INIS)

Millard, A.; Hoffmann, A.; Gauvain, J.; Nahas, G.

1982-06-01

The application of global methods to design reinforced concrete structures was investigated. The dynamic calculation of beam structures can be carried out very economically and with suitable accuracy by these methods. Moreover, one ideal application of global methods is design to failure, in order to estimate the safety margins of a given structure subject to accidental stresses, such as explosions, earthquakes, aircraft crash etc. In all cases, the global method combined with finite element programs serves to determine the failure automatically, and offers a good estimate of the failure load [fr

Maintenance and Repair of Concrete Structures

NARCIS (Netherlands)

Bijen, J.M.J.M.

1989-01-01

In 1987 and 1988 a series of articles was published in the Dutchjournal "Cement" about maintenance and repair of concrete structures. The series was written to promote the transfer of know-how concerning maintenance and repair of concrete structures. Use has been made of know-how developed in the

Damping characteristics of reinforced concrete structures

International Nuclear Information System (INIS)

Hisano, M.; Nagashima, I.; Kawamura, S.

1987-01-01

Reinforced concrete structures in a nuclear power plant are not permitted to go far into the inelasticity generally, even when subjected to strong ground motion. Therefore it is important to evaluate the damping appropriately in linear and after cracking stage before yielding in the dynamic response analysis. Next three dampings are considered of reinforced concrete structures. 1) Internal damping in linear range material damping of concrete without cracks;2) Hysteretic damping in inelastic range material hysteretic damping of concrete due to cracking and yielding;3) Damping due to the energy dissipation into the ground. Among these damping material damping affects dynamic response of a nuclear power plant on hard rock site where damping due to energy dissipation into the ground is scarcely expected. However material damping in linear and slightly nonlinear range have only been assumed without enough experimental data. In this paper such damping is investigated experimentally by the shaking table tests of reinforced concrete box-walls which modeled roughly the outer wall structure of a P.W.R. type nuclear power plant

VISCOELASTIC STRUCTURAL MODEL OF ASPHALT CONCRETE

Directory of Open Access Journals (Sweden)

V. Bogomolov

2016-06-01

Full Text Available The viscoelastic rheological model of asphalt concrete based on the generalized Kelvin model is offered. The mathematical model of asphalt concrete viscoelastic behavior that can be used for calculation of asphalt concrete upper layers of non-rigid pavements for strength and rutting has been developed. It has been proved that the structural model of Burgers does not fully meet all the requirements of the asphalt-concrete.

Structural Effects of Reinforced Concrete Beam Due to Corrosion

Science.gov (United States)

Noh, Hamidun Mohd; Idris, Nur'ain; Noor, Nurazuwa Md; Sarpin, Norliana; Zainal, Rozlin; Kasim, Narimah

2018-03-01

Corrosion of steel in reinforced concrete is one of the main issues among construction stakeholders. The main consequences of steel corrosion include loss of cross section of steel area, generation of expansive pressure which caused cracking of concrete, spalling and delaminating of the concrete cover. Thus, it reduces the bond strength between the steel reinforcing bar and concrete, and deteriorating the strength of the structure. The objective of this study is to investigate the structural effects of corrosion damage on the performance of reinforced concrete beam. A series of corroded reinforced concrete beam with a corrosion rate of 0%, 20% and 40% of rebar corrosion is used in parametric study to assess the influence of different level of corrosion rate to the structural performance. As a result, the used of interface element in the finite element modelling predicted the worst case of corrosion analysis since cracks is induced and generate at this surface. On the other hand, a positive linear relationship was sketched between the increase of expansive pressure and the corrosion rate. Meanwhile, the gradient of the graph is decreased with the increase of steel bar diameter. Furthermore, the analysis shows that there is a significant effect on the load bearing capacity of the structure where the higher corrosion rate generates a higher stress concentration at the mid span of the beam. This study could predict the residual strength of reinforced concrete beam under the corrosion using the finite element analysis. The experimental validation is needed on the next stage to investigate the quantitative relation between the corrosion rate and its influence on the mechanical properties.

Internal inspection of reinforced concrete for nuclear structures using shear wave tomography

International Nuclear Information System (INIS)

Scott, David B.

2013-01-01

Highlights: • Aging of reinforced concrete used for worldwide nuclear structures is increasing and necessitating evaluation. • Nondestructive evaluation is a tool for assessing the condition of reinforced concrete of nuclear structures. • Ultrasonic shear wave tomography as a stress wave technique has begun to be utilized for investigation of concrete material. • A study using ultrasonic shear wave tomography indicates anomalies vital to the long-term operation of the structure. • The use of this technique has shown to successfully evaluate the internal state of reinforced concrete members. - Abstract: Reinforced concrete is important for nuclear related structures. Therefore, the integrity of structural members consisting of reinforced concrete is germane to the safe operation and longevity of these facilities. Many issues that reduce the likelihood of safe operation and longevity are not visible on the surface of reinforced concrete material. Therefore, an investigation of reinforced concrete material should include techniques which will allow peering into the concrete member and determining its internal state. The performance of nondestructive evaluations is pursuant to this goal. Some of the categories of nondestructive evaluations are electrochemical, magnetism, ground penetrating radar, and ultrasonic testing. A specific ultrasonic testing technique, namely ultrasonic shear wave tomography, is used to determine presence and extent of voids, honeycombs, cracks perpendicular to the surface, and/or delamination. This technique, and others similar to it, has been utilized in the nuclear industry to determine structural conditions

Application of petrographic examination techniques to the assessment of fire-damaged concrete and masonry structures

International Nuclear Information System (INIS)

Ingham, Jeremy P.

2009-01-01

The number of building fires has doubled over the last 50 years. There has never been a greater need for structures to be assessed for fire damage to ensure safety and enable appropriate repairs to be planned. Fortunately, even after a severe fire, concrete and masonry structures are generally capable of being repaired rather than demolished. By allowing direct examination of microcracking and mineralogical changes, petrographic examination has become widely used to determine the depth of fire damage for reinforced concrete elements. Petrographic examination can also be applied to fire-damaged masonry structures built of materials such as stone, brick and mortar. Petrography can ensure accurate detection of damaged geomaterials, which provides cost savings during building repair and increased safety reassurance. This paper comprises a review of the role of petrography in fire damage assessments, drawing on a range of actual fire damage investigations.

The evolution and structural design of prestressed concrete pressure vessels

International Nuclear Information System (INIS)

Hannah, I.W.

1978-01-01

The introduction of the prestressed concrete pressure vessel to contain the main gas coolant circuit of nuclear reactors has marked a major step forward. This chapter traces the evolution and development of the PCPV, and lists the principal parameters adopted. Current design and loading standards are discussed in relation to the two main limit states of serviceability and safety. Prestressed concrete pressure vessel analysis has called for very extensive adaptation and expansion of conventional finite element and finite difference methods in order to deal with the elevated temperature of operation, together with extensive concrete testing at temperature and under multi-directional stressing. These new methods and extra data are being adopted in prestressed applications in other fields and may well prove to be of much wider significance than is presently appreciated. (author)

Bi-directional evolutionary structural optimization for strut-and-tie modelling of three-dimensional structural concrete

Science.gov (United States)

Shobeiri, Vahid; Ahmadi-Nedushan, Behrouz

2017-12-01

This article presents a method for the automatic generation of optimal strut-and-tie models in reinforced concrete structures using a bi-directional evolutionary structural optimization method. The methodology presented is developed for compliance minimization relying on the Abaqus finite element software package. The proposed approach deals with the generation of truss-like designs in a three-dimensional environment, addressing the design of corbels and joints as well as bridge piers and pile caps. Several three-dimensional examples are provided to show the capabilities of the proposed framework in finding optimal strut-and-tie models in reinforced concrete structures and verifying its efficiency to cope with torsional actions. Several issues relating to the use of the topology optimization for strut-and-tie modelling of structural concrete, such as chequerboard patterns, mesh-dependency and multiple load cases, are studied. In the last example, a design procedure for detailing and dimensioning of the strut-and-tie models is given according to the American Concrete Institute (ACI) 318-08 provisions.

Modeling of crack in concrete structures subjected to severe loadings

International Nuclear Information System (INIS)

Nguyen, T.G.

2012-01-01

Concrete is a construction materials are prevalent in the world. However, in many industries, it is becoming more common to study the safety margins of a structure with respect to solicitations. It becomes important to predict the failure mode of the structure. Much work has already been made in the world on this subject, leading to operational models in computer codes using finite elements. Nevertheless, difficulties remain, mainly related to concrete cracking. These difficulties lead to open problems concerning the location, initiation and crack propagation. The thesis explores two ways of improving methods of numerical simulation of crack propagation. The first possibility of improvement is the use of the extended finite element method, XFEM. A modeling of mechanical behavior of crack is introduced and leads to a description of crack propagation from one element to another. The second possibility is based on damage mechanics. As part of the modeling of damage generalized standard type, the localization phenomenon has been studied numerically for various behaviors: viscous or damage fragile. These behaviors are described in the same spirit that the laws of the visco-elastic or visco-plasticity or plasticity classics, from a general thermodynamic interpretation. In particular, the laws gradient of damage are also considered in conjunction with recent results from the literature. It is well known that a gradient model for interpreting the effects of scale structures under mechanical loading. It also plays an interesting role in the effects of strain localization. (author)

Concrete material characterization reinforced concrete tank structure Multi-Function Waste Tank Facility

International Nuclear Information System (INIS)

Winkel, B.V.

1995-01-01

The purpose of this report is to document the Multi-Function Waste Tank Facility (MWTF) Project position on the concrete mechanical properties needed to perform design/analysis calculations for the MWTF secondary concrete structure. This report provides a position on MWTF concrete properties for the Title 1 and Title 2 calculations. The scope of the report is limited to mechanical properties and does not include the thermophysical properties of concrete needed to perform heat transfer calculations. In the 1970's, a comprehensive series of tests were performed at Construction Technology Laboratories (CTL) on two different Hanford concrete mix designs. Statistical correlations of the CTL data were later generated by Pacific Northwest Laboratories (PNL). These test results and property correlations have been utilized in various design/analysis efforts of Hanford waste tanks. However, due to changes in the concrete design mix and the lower range of MWTF operating temperatures, plus uncertainties in the CTL data and PNL correlations, it was prudent to evaluate the CTL data base and PNL correlations, relative to the MWTF application, and develop a defendable position. The CTL test program for Hanford concrete involved two different mix designs: a 3 kip/in 2 mix and a 4.5 kip/in 2 mix. The proposed 28-day design strength for the MWTF tanks is 5 kip/in 2 . In addition to this design strength difference, there are also differences between the CTL and MWTF mix design details. Also of interest, are the appropriate application of the MWTF concrete properties in performing calculations demonstrating ACI Code compliance. Mix design details and ACI Code issues are addressed in Sections 3.0 and 5.0, respectively. The CTL test program and PNL data correlations focused on a temperature range of 250 to 450 F. The temperature range of interest for the MWTF tank concrete application is 70 to 200 F

Reusing recycled aggregates in structural concrete

Science.gov (United States)

Kou, Shicong

The utilization of recycled aggregates in concrete can minimize environmental impact and reduce the consumption of natural resources in concrete applications. The aim of this thesis is to provide a scientific basis for the possible use of recycled aggregates in structure concrete by conducting a comprehensive programme of laboratory study to gain a better understanding of the mechanical, microstructure and durability properties of concrete produced with recycled aggregates. The study also explored possible techniques to of improve the properties of recycled aggregate concrete that is produced with high percentages (≧ 50%) of recycled aggregates. These techniques included: (a) using lower water-to-cement ratios in the concrete mix design; (b) using fly ash as a cement replacement or as an additional mineral admixture in the concrete mixes, and (c) precasting recycled aggregate concrete with steam curing regimes. The characteristics of the recycled aggregates produced both from laboratory and a commercially operated pilot construction and demolition (C&D) waste recycling plant were first studied. A mix proportioning procedure was then established to produce six series of concrete mixtures using different percentages of recycled coarse aggregates with and without the use of fly ash. The water-to-cement (binder) ratios of 0.55, 0.50, 0.45 and 0.40 were used. The fresh properties (including slump and bleeding) of recycled aggregate concrete (RAC) were then quantified. The effects of fly ash on the fresh and hardened properties of RAC were then studied and compared with those RAC prepared with no fly ash addition. Furthermore, the effects of steam curing on the hardened properties of RAC were investigated. For micro-structural properties, the interfacial transition zones of the aggregates and the mortar/cement paste were analyzed by SEM and EDX-mapping. Moreover, a detailed set of results on the fracture properties for RAC were obtained. Based on the experimental

Review Of Concrete Biodeterioration In Relation To Buried Nuclear Waste

International Nuclear Information System (INIS)

Turick, C.

2012-01-01

Long-term storage of low level radioactive material in below ground concrete disposal units (DUs) (Saltstone Disposal Facility) is a means of depositing wastes generated from nuclear operations of the U.S. Department of Energy. Based on the currently modeled degradation mechanisms, possible microbial induced effects on the structural integrity of buried low level wastes must be addressed. Previous international efforts related to microbial impacts on concrete structures that house low level radioactive waste showed that microbial activity can play a significant role in the process of concrete degradation and ultimately structural deterioration. This literature review examines the recent research in this field and is focused on specific parameters that are applicable to modeling and prediction of the fate of concrete vaults housing stored wastes and the wastes themselves. Rates of concrete biodegradation vary with the environmental conditions, illustrating a need to understand the bioavailability of key compounds involved in microbial activity. Specific parameters require pH and osmotic pressure to be within a certain range to allow for microbial growth as well as the availability and abundance of energy sources like components involved in sulfur, iron and nitrogen oxidation. Carbon flow and availability are also factors to consider in predicting concrete biodegradation. The results of this review suggest that microbial activity in Saltstone, (grouted low level radioactive waste) is unlikely due to very high pH and osmotic pressure. Biodegradation of the concrete vaults housing the radioactive waste however, is a possibility. The rate and degree of concrete biodegradation is dependent on numerous physical, chemical and biological parameters. Results from this review point to parameters to focus on for modeling activities and also, possible options for mitigation that would minimize concrete biodegradation. In addition, key chemical components that drive microbial

Review of Concrete Biodeterioration in Relation to Buried Nuclear Waste

Energy Technology Data Exchange (ETDEWEB)

Turick, C; Berry, C.

2012-10-15

Long-term storage of low level radioactive material in below ground concrete disposal units (DUs) (Saltstone Disposal Facility) is a means of depositing wastes generated from nuclear operations of the U.S. Department of Energy. Based on the currently modeled degradation mechanisms, possible microbial induced effects on the structural integrity of buried low level wastes must be addressed. Previous international efforts related to microbial impacts on concrete structures that house low level radioactive waste showed that microbial activity can play a significant role in the process of concrete degradation and ultimately structural deterioration. This literature review examines the recent research in this field and is focused on specific parameters that are applicable to modeling and prediction of the fate of concrete vaults housing stored wastes and the wastes themselves. Rates of concrete biodegradation vary with the environmental conditions, illustrating a need to understand the bioavailability of key compounds involved in microbial activity. Specific parameters require pH and osmotic pressure to be within a certain range to allow for microbial growth as well as the availability and abundance of energy sources like components involved in sulfur, iron and nitrogen oxidation. Carbon flow and availability are also factors to consider in predicting concrete biodegradation. The results of this review suggest that microbial activity in Saltstone, (grouted low level radioactive waste) is unlikely due to very high pH and osmotic pressure. Biodegradation of the concrete vaults housing the radioactive waste however, is a possibility. The rate and degree of concrete biodegradation is dependent on numerous physical, chemical and biological parameters. Results from this review point to parameters to focus on for modeling activities and also, possible options for mitigation that would minimize concrete biodegradation. In addition, key chemical components that drive microbial

CONCRETE MIX DESIGN FOR STRUCTURES SUBJECTED TO EXPOSURE CLASS XC1 DEPENDING ON CONCRETE COVER

Directory of Open Access Journals (Sweden)

O. Yu. Cherniakevich

2016-01-01

Full Text Available The reinforced steel corrosion which is the most important problem of reinforced concrete structures durability is generally stipulated for carbonization of concrete surrounding it. Concrete cover calculation at the design stage is predicated one because of the differences in manufacturing conditions and use of constructions. The applying of the probabilistic approaches to the carbonation process modeling allows to get predicated grade of the depth of carbonization of concrete and, thus, to settle minimum concrete cover thickness for a given projected service life of a construction. The procedures for concrete mix design for different strength classes of concrete are described in the article. Current recommendations on assignment of concrete strength class as well as concrete cover are presented. The European Standard EN 206:2013 defines the content requirements for the concrete structures operated in the exposure class XC1, including the minimum values of water-cement ratio, minimum cement content, and minimum strength class of concrete. Since the standard does not include any basis or explanations of the requirements, we made an effort to develop a scientific justification for the mentioned requirements. We developed the probabilistic models for the process of carbonation of concrete based on the concrete mix which was designed using the software VTK-Korroziya. The reinforced concrete structures with concrete cover 20–35 mm operated in the most unfavorable conditions within the exposure class XC1 were analyzed. The corresponding probabilistic calculations of the depth of carbonated concrete are described in the article. 

Aging Evaluation of Nuclear Power Plant Concrete Structures

International Nuclear Information System (INIS)

Kitsutaka, Y.; Takesue, N.; Tsukagoshi, M.

2012-01-01

In this paper, method on the aging evaluation in nuclear power plant concrete structures was investigated. Problems on the durability evaluation of reinforced concrete structures were pointed out and an evaluation framework was considered. In view of the importance of evaluating the degree of deterioration of reinforced concrete structures, relationships should be formulated among the number of years elapsed, t, the amount of action of a deteriorative factor, F, the degree of material deterioration, D, and the performance of the structure, P. Evaluation by PDFt diagrams combining these relationships may be effective. A detailed procedure of durability evaluation for a reinforced concrete structure using PDFt concept is presented for the deterioration factors of thermal effect, irradiation, neutralization and penetration of salinity by referring to the recent papers. And the evaluation framework of the deteriorated material constitutive model which can be used for the numerical analysis of the integrity evaluation for the concrete structure was proposed. (author)

HTGR Base Technology Program. Task 2: concrete properties in nuclear environment. A review of concrete material systems for application to prestressed concrete pressure vessels

International Nuclear Information System (INIS)

Naus, D.J.

1981-05-01

Prestressed concrete pressure vessels (PCPVs) are designed to serve as primary pressure containment structures. The safety of these structures depends on a correct assessment of the loadings and proper design of the vessels to accept these loadings. Proper vessel design requires a knowledge of the component (material) properties. Because concrete is one of the primary constituents of PCPVs, knowledge of its behavior is required to produce optimum PCPV designs. Concrete material systems are reviewed with respect to constituents, mix design, placing, curing, and strength evaluations, and typical concrete property data are presented. Effects of extreme loadings (elevated temperature, multiaxial, irradiation) on concrete behavior are described. Finally, specialty concrete material systems (high strength, fibrous, polymer, lightweight, refractory) are reviewed. 235 references

29 CFR 1926.704 - Requirements for precast concrete.

Science.gov (United States)

2010-07-01

... 29 Labor 8 2010-07-01 2010-07-01 false Requirements for precast concrete. 1926.704 Section 1926..., DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR CONSTRUCTION Concrete and Masonry Construction § 1926.704 Requirements for precast concrete. (a) Precast concrete wall units, structural framing...

Concrete structures under projectile impact

CERN Document Server

Fang, Qin

2017-01-01

In this book, the authors present their theoretical, experimental and numerical investigations into concrete structures subjected to projectile and aircraft impacts in recent years. Innovative approaches to analyze the rigid, mass abrasive and eroding projectile penetration and perforation are proposed. Damage and failure analyses of nuclear power plant containments impacted by large commercial aircrafts are numerically and experimentally analyzed. Ultra-high performance concrete materials and structures against the projectile impact are developed and their capacities of resisting projectile impact are evaluated. This book is written for the researchers, engineers and graduate students in the fields of protective structures and terminal ballistics.

Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete.

Science.gov (United States)

López-Uceda, Antonio; Ayuso, Jesús; Jiménez, José Ramón; Agrela, Francisco; Barbudo, Auxiliadora; De Brito, Jorge

2016-02-02

This research aims to produce non-structural concrete with mixed recycled aggregates (MRA) in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%), using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results) from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors' knowledge, there have not been any upscaled applications of concrete with MRA and low cement content.

Upscaling the Use of Mixed Recycled Aggregates in Non-Structural Low Cement Concrete

Directory of Open Access Journals (Sweden)

Antonio López-Uceda

2016-02-01

Full Text Available This research aims to produce non-structural concrete with mixed recycled aggregates (MRA in upscaled applications with low-cement content. Four slabs were executed with concrete made with different ratios of coarse MRA (0%, 20%, 40% and 100%, using the mix design, the mixing procedures and the facilities from a nearby concrete production plant. The analysis of the long-term compressive and splitting tensile strengths in concrete cores, extracted from the slabs, allowed the highlighting of the long-term high strength development potential of MRA incorporation. The study of cast specimens produced in situ under the same conditions as the slabs showed, firstly, that the use of MRA has a great influence on the properties related to durability, secondly, that the loss of compressive strength for total MRA incorporation relative to control concrete increases proportionally with the class strength, and, thirdly, that the mechanical properties (including Schmidt hammer results from the concrete slabs showed no significant differences relative to the control concrete for coarse aggregates replacements up to 40%. Therefore, this upscaled experimental study supports the application of concrete with 100% coarse MRA incorporation and low cement content in non-structural civil works such as bike lanes, gutters, ground slabs, leveling surfaces, and subgrades for foundations. To the best of the authors’ knowledge, there have not been any upscaled applications of concrete with MRA and low cement content.

Radiographic testing in concrete structures

International Nuclear Information System (INIS)

Oliveira, D. de

1987-01-01

The radiographic testing done in concrete structures is used to analyse the homogeneity, position and corrosion of armatures and to detect discontinuity in the concrete such as: gaps, cracks and segregations. This work develops a Image quality Indicator (IQI) with an adequated sensibility to detect discontinuites based on BS4408 norm. (E.G.) [pt

Durability of thin-walled concrete structures

International Nuclear Information System (INIS)

Salomon, M.; Gallias, J.L.

1991-01-01

The aim of the present document is to draw up a survey of knowledge of the problems of ageing of reinforced concrete shell structure atmospheric coolers. The exposure conditions are particularly favourable to the induction and development of degradation which, because of the thinness of the reinforced concrete can compromise the stability and the durability of coolers. The study will be axed on the link between the specific characteristics of coolers from the point of view of operation, design and environment, also the durability of reinforced concrete. The set of factors exerting their influence on the reinforced concrete of the shell structure (condensates, rain water, temperature and humidity gradients, dynamic loads, weathering, etc.) is particularly complex. The principal degradation reactions involved are classified according to the chemical and physical action on concrete and on the reinforcement. Particular emphasis is placed on the analysis of degradation processes and the influence of the characteristics of the materials and of the medium. The aim is to determine the mechanisms which present the greatest risk for coolers. The interaction between the degradation to concrete and the change in mechanical characteristics is also studied [fr

Concrete in dynamic tension: The fracture process

NARCIS (Netherlands)

Vegt, I.

2016-01-01

Concrete is commonly used in protective and civil structures, like tunnels and storage buildings. For the design and reliable safety assessment of such structures it is very important to know the behaviour of concrete under static loading conditions as well as under impulsive loading. To understand

Effect of soil–structure interaction on the reliability of reinforced concrete bridges

Directory of Open Access Journals (Sweden)

Kamel Bezih

2015-09-01

Full Text Available In the design of reinforced concrete (RC bridges, the random and nonlinear behavior of soil may lead to insufficient reliability levels. For this reason, it is necessary to take into account the variability of soil properties which can significantly affect the bridge behavior regarding ultimate and serviceability limit states. This study investigates the failure probability for existing reinforced concrete bridges due to the effects of interaction between the soil and the structure. In this paper, a coupled reliability–mechanical approach is developed to study the effect of soil–structure interaction for RC bridges. The modeling of this interaction is incorporated into the mechanical model of RC continuous beams, by considering nonlinear elastic soil stiffness. The reliability analysis highlights the large importance of soil–structure interaction and shows that the structural safety is highly sensitive to the variability of soil properties, especially when the nonlinear behavior of soil is considered.

Research on Deterioration Mechanism of Concrete Materials in an Actual Structure

Directory of Open Access Journals (Sweden)

Shiping Zhang

2014-01-01

Full Text Available The cause for deterioration of the concrete structure located in severe environment has been explored both in field and in laboratory. Serious cracking and spalling appeared upon surface of the concrete structure soon after the structure was put into service. Both alkali-aggregate reaction and freeze-thaw cycles may result in similar macro visible cracking and spalling. The possibility of alkali-aggregate reaction was excluded by both field survey and lab examination such as chemical analysis, petrographic analysis, and determination of alkali reactivity of aggregates. According to results of freeze-thaw cycles, impermeability testing, and microstructure analysis, it is deduced that the severe environmental conditions plus the relatively inferior frost resistance cause the deterioration of concrete. Usage of air entraining admixture can improve frost resistance and impermeability. Furthermore, new approaches to mitigate the deterioration of concrete used in severe environmental condition are discussed.

Early-age behaviour of concrete in massive structures, experimentation and modelling

International Nuclear Information System (INIS)

Zreiki, J.; Bouchelaghem, F.; Chaouche, M.

2010-01-01

This study is focused on the behaviour of concrete at early-age in massive structures, in relation with the prediction of both cracking risk and residual stresses, which is still a challenging task. In this paper, a 3D thermo-chemo-mechanical model has been developed, on the basis of complete material characterization experiments, in order to predict the early-age development of strains and residual stresses, and in order to assess the risk of cracking in massive concrete structures. The parameters of the proposed model were identified on two different concretes, High Performance Concrete and Fibrous Self-Compacted Concrete - from simple experiments in the laboratory: uniaxial tension and compression tests, dynamic Young's modulus measurements, free and autogenous shrinkages, semi-adiabatic calorimetry. The proposed model has been implemented in a Finite Element code, and the numerical simulations of the laboratory tests have proved the model consistency. Furthermore, early-age experiments conducted on massive structures have also been simulated, in order to investigate the predictive capability of the model, and to assess the model performance in practical situations where varying temperatures are involved.

Injection technologies for the repair of damaged concrete structures

CERN Document Server

Panasyuk, V V; Sylovanyuk, V P

2014-01-01

This book analyzes the most important achievements in science and engineering practice concerning operational factors that cause damage to concrete and reinforced concrete structures. It includes methods for assessing their strength and service life, especially those that are based on modern concepts of the fracture mechanics of materials. It also includes basic approaches to the prediction of the remaining service life for long-term operational structures. Much attention is paid to injection technologies for restoring the serviceability of damaged concrete and reinforced concrete structures. In particular, technologies for remedying holes, cracks, corrosion damages etc. The books contains sample cases in which the above technologies have been used to restore structural integrity and extend the reliable service life of concrete and reinforced concrete constructions, especially NPPs, underground railways, bridges, seaports and historical relics.

Lateral rigidity of cracked concrete structures

International Nuclear Information System (INIS)

Castellani, A.; Chesi, C.

1979-01-01

Numerical results are discussed on the lateral rigidity of reinforced concrete structures with a given crack distribution. They have been favourably checked with experimental results for cylindrical shells under the effect of a thermal gradient producing vertical cracking or vertical plus horizontal cracking. The main effects characterizing the concrete behaviour are: (1) The shear transfer across a crack; (2) The shear transfer degradation after cyclic loading; (3) The tension stiffening provided by the concrete between crack and crack, in the normal stress transfer; (4) The temperature effect on the elastic moduli of concrete, when cracks are of thermal origin. Only the 1st effect is discussed on an experimental basis. Two broad cathegories of reinforced concrete structures have been investigated in this respect: shear walls of buildings and cylindrical containment structures. The main conclusions so far reached are: (1) Vertical cracks are unlikely to decrease the lateral rigidity to less than 80% of the original one, and to less than 90% when they do not involve the entire thickness of the wall; (2) The appearence of horizontal cracks can reduce the lateral rigidity by some 30% or more; (3) A noticeable but not yet evaluated influence is shown by cyclic loading. (orig.)

Durability of cracked fibre reinforced concrete structures

DEFF Research Database (Denmark)

Hansen, Ernst Jan De Place

1998-01-01

structure are made on specimens drilled or sawed from beams after unloading (mechanical load). The pore structure of the concretes will be studied by microscopy, sorption and suction curves. The test programme involves three different concrete qualities (water-cement ratios). Both steel fibres (ZP...

Considerations in the evaluation of concrete structures for continued service in aged Nuclear Power Plants (NPPs)

International Nuclear Information System (INIS)

Naus, D.; Marchbanks, M.; Oland, B.; Arndt, G.; Brown, T.

1989-01-01

Currently, there are /approximately/119 commercial nuclear power plants (NPPs) in the US either under construction, operating at low-to-full power, or awaiting an operating license. Together, these units have a net generating capacity of /approximately/110 GW(e). Assuming no life extension of present facilities, the operating licenses for these plants will start to expire in the middle of the next decade with Yankee Rowe being the first plant to attain this status. Where it is noted that with no life extension of facilities, a potential loss of electrical generating capacity in excess of 75 GW(e) could occur during the time period 2006 to 2020 when the operating licenses of 80 to 90 NPPs are scheduled to expire. A potential timely and cost-effective solution to meeting future electricity demand, which has worked well for non-nuclear generating plants, is to extend the service life (operating licenses) of existing NPPs. Since the concrete components in these plants provide a vital safety function, any continued service considerations must include an in-depth assessment of the safety-related concrete structures. 7 refs

anisotropic crack modelling of reinforced concrete structures with an enhanced kinematics: application to bidimensional elements under cyclic loading

International Nuclear Information System (INIS)

Kishta, Ejona

2016-01-01

Civil engineering buildings, massive and unique, are mostly made of reinforced or prestressed concrete. Sustainability, tightness and safety are the major pillars of a building's performance. Cracking is a major phenomenon which impacts the buildings' behaviour under different loadings in terms of sustainability and structural capacity. Development of numerical models which describe accurately the response of quasi-brittle materials under complex loading remains an important research topic for the scientific community. The objective of this work is the development of a numerical model which represents explicitly cracking of reinforced concrete structures. Concrete and reinforced concrete degradation process, characterised by the appearance of several anisotropic crack families, is described by means of an anisotropic damage model accounting for oriented crack families. The kinematics of this model is enriched with a displacement jump in order to reproduce the development of cracks in the material during loading. This displacement jump is identified as the crack opening. The developed model is validated on simulations of plain concrete structures exhibiting model as well as mixed-mode failure. The performances of the enriched model are shown by the simulation of reinforced concrete structures such as a shear wall submitted to cyclic loading. (author) [fr

Advanced analysis and design for fire safety of steel structures

CERN Document Server

Li, Guoqiang

2013-01-01

Advanced Analysis and Design for Fire Safety of Steel Structures systematically presents the latest findings on behaviours of steel structural components in a fire, such as the catenary actions of restrained steel beams, the design methods for restrained steel columns, and the membrane actions of concrete floor slabs with steel decks. Using a systematic description of structural fire safety engineering principles, the authors illustrate the important difference between behaviours of an isolated structural element and the restrained component in a complete structure under fire conditions. The book will be an essential resource for structural engineers who wish to improve their understanding of steel buildings exposed to fires. It is also an ideal textbook for introductory courses in fire safety for master’s degree programs in structural engineering, and is excellent reading material for final-year undergraduate students in civil engineering and fire safety engineering. Furthermore, it successfully bridges th...

Numerical modelling of crack initiation and propagation in concrete structure under hydro-mechanical loading

International Nuclear Information System (INIS)

Bian, H.B.; Jia, Y.; Shao, J.F.

2012-01-01

Document available in extended abstract form only. This subject is devoted to numerical analysis of crack initiation and propagation in concrete structures due to hydro-mechanical coupling processes. When the structures subjected to the variation in hydraulic conditions, fractures occur as a consequence of coalescence of diffuse damage. Consequently, the mechanical behaviour of concrete is described by an isotropic damage model. Once the damage reaches a critical value, a macroscopic crack is initiated. In the framework of extended Finite Element Method (XFEM), the propagation of localized crack is studied in this paper. Each crack is then considered as a discontinuity surface of displacement. According to the determination of crack propagation orientations, a tensile stress-based criterion is used. Furthermore, spatial variations of mechanical properties of concrete are also taken into account using the Weibull distribution function. Finally, the proposed model is applied to numerical analysis of a concrete liner in the context of feasibility studies for geological storage of radioactive wastes. The numerical results show that the proposed approach is capable to reproduce correctly the initiation and propagation crack process until the complete failure of concrete structures during hydro-mechanical loading. The concrete is most widely used construction material in many engineering applications. It is generally submitted to various environmental loading: such as the mechanical loading, the variation of relative humidity and the exposure to chemical risk, etc. In order to evaluate the safety and durability of concrete structures, it is necessary to get a good knowledge on the influence of loading path on the concrete behaviour. The objective of this paper is to study numerically the crack propagation in concrete structure under hydro-mechanical loading,.i.e. the mechanical behaviour of concrete subjected to drying process. The drying process leads to desiccation

Assessment of mass fraction and melting temperature for the application of limestone concrete and siliceous concrete to nuclear reactor basemat considering molten core-concrete interaction

Energy Technology Data Exchange (ETDEWEB)

Lee, Ho Jae; Kim, Do Gyeum [Korea Institute of Civil Engineering and Building Technology, Goyang (Korea, Republic of); Cho, Jae Leon [Korea Hydro and Nuclear Power Co., Ulsan (Korea, Republic of); Yoon, Eui Sik [Korea Institute of Nuclear Safety, Daejeon (Korea, Republic of); Cho, Myung Suk [Korea Hydro and Nuclear Power Co., Central Research Institute, Daejeon (Korea, Republic of)

2016-04-15

Severe accident scenarios in nuclear reactors, such as nuclear meltdown, reveal that an extremely hot molten core may fall into the nuclear reactor cavity and seriously affect the safety of the nuclear containment vessel due to the chain reaction caused by the reaction between the molten core and concrete. This paper reports on research focused on the type and amount of vapor produced during the reaction between a high-temperature molten core and concrete, as well as on the erosion rate of concrete and the heat transfer characteristics at its vicinity. This study identifies the mass fraction and melting temperature as the most influential properties of concrete necessary for a safety analysis conducted in relation to the thermal interaction between the molten core and the basemat concrete. The types of concrete that are actually used in nuclear reactor cavities were investigated. The H2O content in concrete required for the computation of the relative amount of gases generated by the chemical reaction of the vapor, the quantity of CO2 necessary for computing the cooling speed of the molten core, and the melting temperature of concrete are evaluated experimentally for the molten core-concrete interaction analysis.

On the Degradation of Concrete in Marine Structures

DEFF Research Database (Denmark)

Burcharth, Hans F.; Hofman Frisch, P.; Freisleben, P.

1985-01-01

Concrete is a cheap and extremely handy material and as such used extensively also in marine structures. Everybody dealing with this material knows examples of concrete apparently of almost infinite durability but also examples where serious degradation started shortly after completion of the str......Concrete is a cheap and extremely handy material and as such used extensively also in marine structures. Everybody dealing with this material knows examples of concrete apparently of almost infinite durability but also examples where serious degradation started shortly after completion...

Nonlinear finite element analysis of concrete structures

International Nuclear Information System (INIS)

Ottosen, N.S.

1980-05-01

This report deals with nonlinear finite element analysis of concrete structures loaded in the short-term up until failure. A profound discussion of constitutive modelling on concrete is performed; a model, applicable for general stress states, is described and its predictions are compared with experimental data. This model is implemented in the AXIPLANE-program applicable for axisymmetrick and plane structures. The theoretical basis for this program is given. Using the AXIPLANE-program various concrete structures are analysed up until failure and compared with experimental evidence. These analyses include panels pressure vessel, beams failing in shear and finally a specific pull-out test, the Lok-Test, is considered. In these analyses, the influence of different failure criteria, aggregate interlock, dowel action, secondary cracking, magnitude of compressive strenght, magnitude of tensile strenght and of different post-failure behaviours of the concrete are evaluated. Moreover, it is shown that a suitable analysis of the theoretical data results in a clear insight into the physical behaviour of the considered structures. Finally, it is demonstrated that the AXISPLANE-program for widely different structures exhibiting very delicate structural aspects gives predictions that are in close agreement with experimental evidence. (author)

Teaching concrete structures

DEFF Research Database (Denmark)

Goltermann, Per

2014-01-01

The teaching of concrete structures has been revised and a number of new approaches have been developed, implemented and evaluated. Inductive teaching, E-learning and “patches” have been found to be improvements and may be an inspiration and help for others development of the teaching and learning...

Ultrasonic imaging in concrete

International Nuclear Information System (INIS)

Ribay, G.; Paris, O.; Rambach, J.M.

2009-01-01

The third and final protection barrier confining nuclear reactors is usually a concrete containment structure. Monitoring the structural integrity of these barriers is critical in ensuring the safety of nuclear power plants. The Institute for Radiological Protection and Nuclear Safety (IRSN) in France in collaboration with the French Atomic commission (CEA/LIST) has developed an ultrasonic phased-array technique capable of inspecting thick concrete walls. The non-destructive method is dedicated to detect cracks and bulk defects. Given the thickness of the structure (1.2 m) undergoing inspection and the heterogeneity of the concrete, the optimal frequency lies in the 50-300 kHz range. At these frequencies, the ultrasonic beam profiles are widespread (non-directive) with poor signal-to-noise ratio. Previous studies have shown the potential of using phased-array techniques (i.e., beam focusing and beam steering) in order to improve detection resolution and sizing accuracy. In this paper we present experimental studies performed with array up to 16 transducers working at 200 kHz. Experiments are carried out on representative concrete blocks containing artificial defects. One is a reinforced mock-up representative of the first reinforcing mesh of wall containment. Experimental results show that in spite of the reinforcement, artificial defects deep as half a meter can be detected. Reconstructed images resulting from phased array acquisitions on an artificial crack embedded in a concrete block are also presented and discussed. The presented method allows detecting oriented defects in concrete with improved signal to noise ratio and sensibility. A simulation model of the interaction of ultrasound with a heterogeneous medium like concrete is briefly commented. (authors)

Utilization of recycled concrete aggregates in structural concrete by applying a fraction partitioning model

NARCIS (Netherlands)

Wouw, van de P.M.F.; Doudart de la Grée, G.C.H.; Florea, M.V.A.; Brouwers, H.J.H.; Bilek, V.; Kersner, Z.

2014-01-01

The recycling of concrete waste into new structural concrete reduces the utilization of raw materials, decreases transport and production energy cost, and saves the use of limited landfill space. Currently, recycling involves the use of recycled concrete aggregates (RCA) as road base material or in

Structural aging program status report

International Nuclear Information System (INIS)

Naus, D.J.; Oland, C.B.; Ellingwood, B.; Graves, H.L. III

1994-01-01

Research is being conducted at the Oak Ridge National Laboratory under Nuclear Regulatory Commission (USNRC) sponsorship to address aging management of safety-related concrete structures. Documentation is being prepared to provide the USNRC with potential structural safety issues and acceptance criteria for use in continued service evaluations of nuclear power plants. Program accomplishments have included development of the Structural Materials Information Center containing data and information on the time variation of 144 material properties under the influence of pertinent environmental stressors or aging factors, performance assessments of reinforced concrete structures in several United Kingdom nuclear power facilities, evaluation of European and North American repair practices for concrete, an evaluation of factors affecting the corrosion of metals embedded in concrete, and application of the time-dependent reliability methodology to reinforced concrete flexure and shear structural elements to investigate the role of in-service inspection and repair on their probability of failure

Early-age behaviour of concrete in massive structures, experimentation and modelling

Energy Technology Data Exchange (ETDEWEB)

Zreiki, J., E-mail: zreiki@lmt.ens-cachan.f [ENS Cachan/CNRS UMR8535/UPMC/PRES UniverSud Paris, Cachan (France); Bouchelaghem, F. [ENS Cachan/CNRS UMR8535/UPMC/PRES UniverSud Paris, Cachan (France); UPMC Univ Paris 06 (France); Chaouche, M. [ENS Cachan/CNRS UMR8535/UPMC/PRES UniverSud Paris, Cachan (France)

2010-10-15

This study is focused on the behaviour of concrete at early-age in massive structures, in relation with the prediction of both cracking risk and residual stresses, which is still a challenging task. In this paper, a 3D thermo-chemo-mechanical model has been developed, on the basis of complete material characterization experiments, in order to predict the early-age development of strains and residual stresses, and in order to assess the risk of cracking in massive concrete structures. The parameters of the proposed model were identified on two different concretes, High Performance Concrete and Fibrous Self-Compacted Concrete - from simple experiments in the laboratory: uniaxial tension and compression tests, dynamic Young's modulus measurements, free and autogenous shrinkages, semi-adiabatic calorimetry. The proposed model has been implemented in a Finite Element code, and the numerical simulations of the laboratory tests have proved the model consistency. Furthermore, early-age experiments conducted on massive structures have also been simulated, in order to investigate the predictive capability of the model, and to assess the model performance in practical situations where varying temperatures are involved.

High performance repairing of reinforced concrete structures

International Nuclear Information System (INIS)

Iskhakov, I.; Ribakov, Y.; Holschemacher, K.; Mueller, T.

2013-01-01

Highlights: ► Steel fibered high strength concrete is effective for repairing concrete elements. ► Changing fibers’ content, required ductility of the repaired element is achieved. ► Experiments prove previously developed design concepts for two layer beams. -- Abstract: Steel fibered high strength concrete (SFHSC) is an effective material that can be used for repairing concrete elements. Design of normal strength concrete (NSC) elements that should be repaired using SFHSC can be based on general concepts for design of two-layer beams, consisting of SFHSC in the compressed zone and NSC without fibers in the tensile zone. It was previously reported that such elements are effective when their section carries rather large bending moments. Steel fibers, added to high strength concrete, increase its ultimate deformations due to the additional energy dissipation potential contributed by fibers. When changing the fibers’ content, a required ductility level of the repaired element can be achieved. Providing proper ductility is important for design of structures to dynamic loadings. The current study discusses experimental results that form a basis for finding optimal fiber content, yielding the highest Poisson coefficient and ductility of the repaired elements’ sections. Some technological issues as well as distribution of fibers in the cross section of two-layer bending elements are investigated. The experimental results, obtained in the frame of this study, form a basis for general technological provisions, related to repairing of NSC beams and slabs, using SFHSC.

Digital Image Correlation of Concrete Slab at University of Tennessee, Knoxville

Energy Technology Data Exchange (ETDEWEB)

Mahadevan, Sankaran [Idaho National Lab. (INL), Idaho Falls, ID (United States); Agarwal, Vivek [Idaho National Lab. (INL), Idaho Falls, ID (United States); Pham, Binh T. [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kyle, Neal [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2016-09-01

Assessment and management of aging concrete structures in nuclear power plants require a more systematic approach than simple reliance on existing code margins of safety. Some degradation mechanisms of concrete manifest themselves via swelling or by other shape deformation of the concrete. Specifically, degradation of concrete structure damaged by ASR is viewed as one of the dominant factors impacting the structural integrity of aging nuclear power plants. Structural health monitoring of concrete structures aims to understand the current health condition of a structure based on heterogeneous measurements to produce high-confidence actionable information regarding structural integrity that supports operational and maintenance decisions. Number of nondestructive examination techniques (i.e., thermography, digital image correlation, mechanical deformation measurements, nonlinear impact resonance (DIC) acoustic spectroscopy, and vibro-acoustic modulation) is used to detect the damage caused by ASR. DIC techniques have been increasing in popularity, especially in micro- and nano-scale mechanical testing applications due to its relative ease of implementation and use. Advances in computer technology and digital cameras help this method moving forward. To ensure the best outcome of the DIC system, important factors in the experiment are identified. They include standoff distance, speckle size, speckle pattern, and durable paint. These optimal experimental options are selected basing on a thorough investigation. The resulting DIC deformation map indicates that this technique can be used to generate data related to degradation assessment of concrete structure damaged by the impact of ASR.

Digital Image Correlation of Concrete Slab at University of Tennessee, Knoxville

International Nuclear Information System (INIS)

Mahadevan, Sankaran; Agarwal, Vivek; Pham, Binh T.; Kyle, Neal

2016-01-01

Assessment and management of aging concrete structures in nuclear power plants require a more systematic approach than simple reliance on existing code margins of safety. Some degradation mechanisms of concrete manifest themselves via swelling or by other shape deformation of the concrete. Specifically, degradation of concrete structure damaged by ASR is viewed as one of the dominant factors impacting the structural integrity of aging nuclear power plants. Structural health monitoring of concrete structures aims to understand the current health condition of a structure based on heterogeneous measurements to produce high-confidence actionable information regarding structural integrity that supports operational and maintenance decisions. Number of nondestructive examination techniques (i.e., thermography, digital image correlation, mechanical deformation measurements, nonlinear impact resonance (DIC) acoustic spectroscopy, and vibro-acoustic modulation) is used to detect the damage caused by ASR. DIC techniques have been increasing in popularity, especially in micro- and nano-scale mechanical testing applications due to its relative ease of implementation and use. Advances in computer technology and digital cameras help this method moving forward. To ensure the best outcome of the DIC system, important factors in the experiment are identified. They include standoff distance, speckle size, speckle pattern, and durable paint. These optimal experimental options are selected basing on a thorough investigation. The resulting DIC deformation map indicates that this technique can be used to generate data related to degradation assessment of concrete structure damaged by the impact of ASR.

Failure/leakage predictions of concrete structures containing cracks

International Nuclear Information System (INIS)

Pan, Y.C.; Marchertas, A.H.; Kennedy, J.M.

1984-06-01

An approach is presented for studying the cracking and radioactive release of a reactor containment during severe accidents and extreme environments. The cracking of concrete is modeled as the blunt crack. The initiation and propagation of a crack are determined by using the maximum strength and the J-integral criteria. Furthermore, the extent of cracking is related to the leakage calculation by using a model developed by Rizkalla, Lau and Simmonds. Numerical examples are given for a three-point bending problem and a hypothetical case of a concrete containment structure subjected to high internal pressure during an accident

Monitoring of Concrete Structures Using Ofdr Technique

Science.gov (United States)

Henault, J. M.; Salin, J.; Moreau, G.; Delepine-Lesoille, S.; Bertand, J.; Taillade, F.; Quiertant, M.; Benzarti, K.

2011-06-01

Structural health monitoring is a key factor in life cycle management of infrastructures. Truly distributed fiber optic sensors are able to provide relevant information on large structures, such as bridges, dikes, nuclear power plants or nuclear waste disposal facilities. The sensing chain includes an optoelectronic unit and a sensing cable made of one or more optical fibers. A new instrument based on Optical Frequency Domain Reflectometry (OFDR), enables to perform temperature and strain measurements with a centimeter scale spatial resolution over hundred of meters and with a level of precision equal to 1 μstrain and 0.1 °C. Several sensing cables are designed with different materials targeting to last for decades in a concrete aggressive environment and to ensure an optimal transfer of temperature and strain from the concrete matrix to the optical fiber. Tests were carried out by embedding various sensing cables into plain concrete specimens and representative-scale reinforced concrete structural elements. Measurements were performed with an OFDR instrument; meanwhile, mechanical solicitations were imposed to the concrete element. Preliminary experiments are very promising since measurements performed with distributed sensing system are comparable to values obtained with conventional sensors used in civil engineering and with the Strength of Materials Modelling. Moreover, the distributed sensing system makes it possible to detect and localize cracks appearing in concrete during the mechanical loading.

Assessment of Mass Fraction and Melting Temperature for the Application of Limestone Concrete and Siliceous Concrete to Nuclear Reactor Basemat Considering Molten Core–Concrete Interaction

Directory of Open Access Journals (Sweden)

Hojae Lee

2016-04-01

Full Text Available Severe accident scenarios in nuclear reactors, such as nuclear meltdown, reveal that an extremely hot molten core may fall into the nuclear reactor cavity and seriously affect the safety of the nuclear containment vessel due to the chain reaction caused by the reaction between the molten core and concrete. This paper reports on research focused on the type and amount of vapor produced during the reaction between a high-temperature molten core and concrete, as well as on the erosion rate of concrete and the heat transfer characteristics at its vicinity. This study identifies the mass fraction and melting temperature as the most influential properties of concrete necessary for a safety analysis conducted in relation to the thermal interaction between the molten core and the basemat concrete. The types of concrete that are actually used in nuclear reactor cavities were investigated. The H2O content in concrete required for the computation of the relative amount of gases generated by the chemical reaction of the vapor, the quantity of CO2 necessary for computing the cooling speed of the molten core, and the melting temperature of concrete are evaluated experimentally for the molten core–concrete interaction analysis.

Studies on connecting structure between steel shell and steel reinforced concrete; Kokaku to tekkotsu tekkin concrete tono ketsugo kozo ni kansuru kenkyu

Energy Technology Data Exchange (ETDEWEB)

Morimoto, A. [Kinki University, Osaka (Japan). Faculty of Science and Engineering; Morikawa, H.; Ito, N. [Metropolitan Expressway Public Corp., Tokyo (Japan)

1996-02-15

On the insert reinforcing bar structure for the connecting part of the main tower of cable stayed bridges, this paper reports verification results on a load resistant safety with a full-scale model, structure analysis and construction work. The basic structure was composed of a drilled steel shell, inserted reinforcing bars, fixing structure of bars in lining concrete of the shell and a pressure bearing plate. As an experimental result, the connecting part had a sufficient load carrying capacity against both tensile and compressive loads. The shear stress of the insert reinforcing bar structure was estimated successfully under von Mises`s condition. The shear spring constant in deformation characteristics was linearly proportional to an inserted reinforcing bar ratio. In earthquake, nearly 60% of an allowable compressive load was transferred to concrete through the pressure bearing plate. The analytical results of load resistant deformation characteristics of the connecting part well agreed with experimental ones, and the proposed analytical model was applicable to estimation of a dynamic behavior. 5 refs., 22 figs., 4 tabs.

Seismic fragility of a reinforced concrete structure

Energy Technology Data Exchange (ETDEWEB)

Kurmann, Davide [Axpo Power AG, Baden (Switzerland); Proske, Dirk [Axpo Power AG, Doettingen (Switzerland); Cervenka, Jan [Cervenka Consulting, Prague (Czech Republic)

2013-05-15

Structures can be exposed to seismic loading. For structures of major importance, extreme seismic loadings have to be considered. The proof of safety for such loadings requires sophisticated analysis. This paper introduces an analysis method which of course still includes simplifications, but yields to a far more realistic estimation of the seismic load bearing capacity of reinforced concrete structures compared to common methods. It is based on the development of pushover curves and the application of time-histories for the dynamic model to a representative harmonic oscillator. Dynamic parameters of the oscillator, such as modal mass and damping are computed using a soil-structure-interaction analysis. Based on the pushover-curve nonlinear force-deformation-capacities are applied to the oscillator including hysteresis behaviour characteristics. The oscillator is then exposed to time-histories of several earthquakes. Based on this computation the ductility is computed. The ductility can be scaled based upon the scaling of the time-histories. Since both, the uncertainty of the earthquake by using different timehistories and the uncertainty of the structure by using characteristic and mean material values, are considered, the uncertainty of the structure under seismic loading can be explicitly represented by a fragility. (orig.)

Phases of fracture process zone and tension softening properties of concrete

International Nuclear Information System (INIS)

Mihashi, H.; Nomura, N.

1991-01-01

The safety and serviceability of concrete structures are influenced very much by the cracking behavior of concrete. Since comprehensive numerical analysis techniques have been extensively developed to predict the mechanical behavior of concrete structures in the limit state, it is essential to study the constitutive laws to describe the cracking behavior of concrete in detail. The tension softening behavior of concrete is highly dominated by the existence of a fracture process zone (FPZ) ahead of a crack tip. Since the direct observation of the FPZ of concrete is hardly possible, the indirect techniques are applied, but it is still ambiguous what happens in the FPZ and how it affects the tension softening property. The purpose of this study is to present the property of the FPZ focusing on the influence of material structures by means of three-dimensional acoustic emission. These results are correlated to tension softening behavior evaluated by a numerical analysis to discuss how the tension softening property is related to the characteristics of the FPZ. The test procedure and the results are reported. (K.I.)

Reinforced concrete containment structures in high seismic zones

International Nuclear Information System (INIS)

Aziz, T.S.

1977-01-01

A new structural concept for reinforced concrete containment structures at sites where earthquake ground motions in terms of the Safe Shutdown Earthquake (SSE) exceeds 0.3 g is presented. The structural concept is based on: (1) an inner steel-lined concrete shell which houses the reactor and provides shielding and containment in the event of loss of coolant accident; (2) an outer annular concrete shell structure which houses auxiliary reactor equipment and safeguards systems. These shell structures are supported on a common foundation mat which is embedded in the subgrade. Under stipulated earthquake conditions the two shell structures interact to resist lateral inertia forces. Thus the annular structure which is not a pressure boundary acts as a lateral support for the inner containment shell. The concept is practical, economically feasible and new to practice. (Auth.)

Evaluation and rehabilitation of corrosion damaged reinforced concrete structures

International Nuclear Information System (INIS)

Paul, I.S.

1999-01-01

For the last two decades, rehabilitation of corrosion damaged concrete structures has been one of the most important challenges faced by the construction industry throughout the world. The extent of the damage is significant in cold climates and also in hot and humid climates. In both cases, the corrosion is invariably initiated by ingress of salts into the concrete either from de-icing salts used on roads, or from salt-laden air, soils or ground water. However, there is a contrast in sites of distress in the two climatic regions mentioned above. In cold climates, where de-icing salts are used, the damage is generally to superstructures and is therefore visible, but in hot, humid coastal regions damage is primarily in the substructures and may not be so clearly apparent. This paper presents the corrosion mechanism in concrete deterioration, the methods of evaluation of the damaged structures, and rehabilitation strategies. A case history of a concrete rehabilitation project is included together with some lessons learned in rehabilitation of corrosion damaged structures. Recommendations are made for maintenance of concrete structures and a warning is issued that salt run-off from roads in cold climates may cause distress in below ground concrete structures, similar to structures in hot and humid climates with saline groundwater and soils. (author)

Mimicking Bone Healing Process to Self Repair Concrete Structure Novel Approach Using Porous Network Concrete

NARCIS (Netherlands)

Sangadji, S.; Schlangen, H.E.J.G.

2013-01-01

To repair concrete cracks in difficult or dangerous conditions such as underground structures or hazardous liquid containers, self healing mechanism is a promising alternative method. This research aims to imitate the bone self healing process by putting porous concrete internally in the concrete

Civil engineering: calculations of pre-stressed concrete structures using CodeAster

International Nuclear Information System (INIS)

Gerard, B.; Ulm, F.

1997-11-01

This document presents an analysis of the different calculation methods for pre-stressed concrete structure which can be performed by using finite element methods. Two methods of calculating the pre-stressing of concrete structures with finite elements have been determined. The equivalent method which consists of replacing the action of pre-stressing the concrete by equivalent forces. These method is well suited to dimensioning and studying the overall stability of a structure. It is not an easy matter to take into account the coupled or time-varying phenomena. This approach ignores the evolution of the interaction between the pre-stressing and the concrete. The explicit method which consists of including the mechanical resolution of the pre-stressed cables in that of a concrete structure. Not only does this allow a local study of the pre-stressed to be made, it also allows the coupling which developed over time to be determined, e.g. slip, deferred deformation and coupling between the steel and concrete behaviours. This method enables non-linear phenomena with varying degrees of complexity, such as fracture or yielding of the steels, drying out of the concrete, creep, etc to be described. The two methods are complementary. This document presents the mathematical and computer developments relating to each of this method. In the case of the explicit method, certain of the Code-Aster functions already make it possible to meet several EDF application requirements. Several couplings can be taken into account, such as thermomechanical, shrinkage in drying, creep, relaxation and injection of the cables. Three immediate developments of Code-Aster are proposed for the following applications: - a procedure for calculating the pre-stress losses along the pre-stressing cables; - a command to allocate these forces in the form of an initial force field in the bar elements associated with the cables; - a procedure for linking elements whose nodes do not coincide with each other

Required performance to the concrete structure of the accelerator facilities

International Nuclear Information System (INIS)

Irie, Masaaki; Yoshioka, Masakazu; Miyahara, Masanobu

2006-01-01

As for the accelerator facility, there is many a thing which is constructed as underground concrete structure from viewpoint such as cover of radiation and stability of the structure. Required performance to the concrete structure of the accelerator facility is the same as the general social infrastructure, but it has been possessed the feature where target performance differs largely. As for the body sentence, expressing the difference of the performance which is required from the concrete structure of the social infrastructure and the accelerator facility, construction management of the concrete structure which it plans from order of the accelerator engineering works facility, reaches to the design, supervision and operation it is something which expresses the method of thinking. In addition, in the future of material structural analysis of the concrete which uses the neutron accelerator concerning view it showed. (author)

Void structure of concrete with superabsorbent polymers and its relation to frost resistance of concrete

DEFF Research Database (Denmark)

Hasholt, Marianne Tange; Jensen, Ole Mejlhede; Laustsen, Sara

2013-01-01

the difference between poor and satisfactory frost-resistance. Furthermore, the results indicate that voids created directly by SAP protect concrete against frost deterioration just like other air voids; if the concrete contains enough SAP voids, these alone can provide sufficient frost resistance. © 2013 RILEM....

Impact of soil-structure interaction on the probabilistic frequency variation of concrete structures

International Nuclear Information System (INIS)

Hadjian, A.H.; Hamilton, C.W.

1975-01-01

Earthquake response of equipment in nuclear power plants is characterized by floor response spectra. Since these spectra peak at the natural frequencies of the structure, it is important, both from safety and cost standpoints, to determine the degree of the expected variability of the calculated structural frequencies. A previous work is extended on the variability of the natural frequencies of structures due to the variations of concrete properties and a rigorous approach is presented to evaluate frequency variations based on the probability distributions of both the structural and soil parameters and jointly determine the distributions of the natural frequencies. It is assumed that the soil-structure interaction coefficients are normally distributed. With the proper choice of coordinates, the simultaneous random variations of both the structural properties and the interaction coefficients can be incorporated in the eigenvalue problem. The key methodology problem is to obtain the probability distribution of eigenvalues of matrices with random variable elements. Since no analytic relation exists between the eigenvalues and the elements, a numerical procedure had to be designed. It was found that the desired accuracy can be best achieved by splitting the joint variation into two parts: the marginal distribution of soil variations and the conditional distribution of structural variations at specific soil fractiles. Then after calculating the actual eigenvalues at judiciously selected paired values of soil and structure parameters, this information is recombined to obtain the desired cumulative distribution of natural frequencies

Surface Chloride Levels in Colorado Structural Concrete

Science.gov (United States)

2018-01-01

This project focused on the chloride-induced corrosion of reinforcing steel in structural concrete. The primary goal of this project is to analyze the surface chloride concentration level of the concrete bridge decks throughout Colorado. The study in...

Structural behaviour of concrete poles used in electric's power distribution network

Directory of Open Access Journals (Sweden)

Mehran Zeynalian

2017-12-01

Full Text Available Based on a preliminary study on regional electric companies, it is shown that there is no precise structural design on the concrete poles. This leads to uneconomical and overestimated networks’ components. Therefore, this study was aimed to investigate the lateral performance of the concrete poles which are employed in electric’s power distribution network. This paper presents a numerical study on structural performance of 12 m concrete poles used in electric’s power distribution network using Abaqus software. A sensitivity study for mesh size is carried out and concrete damaged plasticity has been employed. The results show that relatively coarse mesh (average in damaged concrete method gives more reliable result. Some experimental tests based on the Iranian standards were performed in order to make a bench mark for numerical output. Comparison between numerical and experimental results indicates a good agreement between the results. The outcomes also suggest that while the applied lateral load is less than around 400 kg which is assumed as the nominal resistance of the pole, no transverse crack occurs. Based on both experimental and numerical results, one or two transverse cracks are reported when the applied force reaches up to 600 kg. The rate of cracks is amplified by increasing the applied force; and finally, the pole would lose its capacity when the load rises much more than 1200 kg. The study also shows that the poles are very weak when the load direction changes. Also, it can be concluded that the final strength of the pole is higher than what the standards recommend. Finally, seismic behavior factor of the poles around both main axes are evaluated. The estimated seismic resistance factor for the concrete poles indicates that the prescribed R factor for such structure is relatively low; and can be improved at least 20%.

Experiment Observations of the Effects of Fiber Types on the Post-peak Behaviors of Steel Fiber Reinforced Concretes under Tension

International Nuclear Information System (INIS)

Cho, Hyun Woo; Moon, Jae Heum; Lee, Jang Hwa; Kang, Su Tae

2012-01-01

Concrete is one of the major construction materials that are used to form the containing structures with the function as a radiation barrier for nuclear power plants. While current (steel reinforced) concrete structures for nuclear power plants provide reliable serviceability regarding the requirements of design codes, further safety requirement has been issued with the considerations of the impact of a large, commercial aircraft. U.S. NRC (Nuclear Regulatory Commission) announced the new regulatory code, 10CFR50.150 related to an aircraft impact assessment (AIA). The goal of AIA is to enhance the safety and robustness of new reactor designs at the design stage. To enhance the safety against aircraft impact, two approaches can be simply suggested, increase of barrier wall thickness and/or application of double containment structures. However, these two approaches expect much higher construction costs and much longer building period. Even also, when the thickness of concrete structure is increased, special cares will be expected during the process of concrete placement because of the cracking behavior of mass concrete due to hydration heat. To avoid the pre-described problems and difficulties, strengthening of the concrete properties could be an alternative and the increase of fracture toughness of concrete itself will be the practical approach to enhance the impact resistivity. With this consideration, this research observed the effects of steel fiber reinforcement on the enhancement of fracture toughness for possible future application to nuclear power plant structures

Experiment Observations of the Effects of Fiber Types on the Post-peak Behaviors of Steel Fiber Reinforced Concretes under Tension

Energy Technology Data Exchange (ETDEWEB)

Cho, Hyun Woo; Moon, Jae Heum; Lee, Jang Hwa [Korea Institute of Construction Technology, Goyang (Korea, Republic of); Kang, Su Tae [Daegu University, Gyeongsan (Korea, Republic of)

2012-05-15

Concrete is one of the major construction materials that are used to form the containing structures with the function as a radiation barrier for nuclear power plants. While current (steel reinforced) concrete structures for nuclear power plants provide reliable serviceability regarding the requirements of design codes, further safety requirement has been issued with the considerations of the impact of a large, commercial aircraft. U.S. NRC (Nuclear Regulatory Commission) announced the new regulatory code, 10CFR50.150 related to an aircraft impact assessment (AIA). The goal of AIA is to enhance the safety and robustness of new reactor designs at the design stage. To enhance the safety against aircraft impact, two approaches can be simply suggested, increase of barrier wall thickness and/or application of double containment structures. However, these two approaches expect much higher construction costs and much longer building period. Even also, when the thickness of concrete structure is increased, special cares will be expected during the process of concrete placement because of the cracking behavior of mass concrete due to hydration heat. To avoid the pre-described problems and difficulties, strengthening of the concrete properties could be an alternative and the increase of fracture toughness of concrete itself will be the practical approach to enhance the impact resistivity. With this consideration, this research observed the effects of steel fiber reinforcement on the enhancement of fracture toughness for possible future application to nuclear power plant structures

Radiation shielding structure for concrete structure

International Nuclear Information System (INIS)

Oya, Hiroshi

1998-01-01

Crack inducing members for inducing cracks in a predetermined manner are buried in a concrete structure. Namely, a crack-inducing member comprises integrally a shielding plate and extended plates situated at the center of a wall and inducing plates vertically disposed to the boundary portion between them with the inducing plates being disposed each in a direction perforating the wall. There are disposed integrally a pair of the inducing plate spaced at a predetermined horizontal distance on both sides of the shielding plate so as to form a substantially crank-shaped cross section and extended plates formed in the extending direction of the shielding plate, and the inducing plates are disposed each in a direction perforating the wall. Then, cracks generated when stresses are exerted can be controlled, and generation of cracks passing through the concrete structure can be prevented reliably. The reliability of a radiation shielding effect can be enhanced remarkably. (N.H.)

Peculiarities of Thermal Treatment of Monolithic Reinforced Concrete Structures

Science.gov (United States)

Kuchin, V. N.; Shilonosova, N. V.

2017-11-01

A mathematical program has been developed that allows one to determine the parameters of heat treatment of monolithic structures. One of the quality indicators of monolithic reinforced concrete structures is the level of temperature stresses arising in the process of heat treatment and further operation of structures. In winter at heat treatment the distribution of temperatures along the cross-section of the structure is uneven. A favorable thermo-stressed state in a concrete massif occurs when using the preheating method, providing the concrete temperature in the center of the structure is greater than at the periphery. In this case, after the strength is set and the temperature is later equalized along the cross-section, the central part of the structure tends to decrease its dimensions more but the extreme zones prevent it. Therefore, the center is in a state of tension, and the extreme zones on the periphery are compressed. In compressed concrete there is a lesser chance of cracks or defects. The temperature gradient over the section of the structure, the stress in the concrete and its strength are determined. When calculating the temperature and strength fields, the stress level was determined - a value equal to the ratio of the tensile stresses in the section under consideration to the tensile strength of the concrete in this section at the same time. The nature of the change in stress level is determined by the massive structure and power of the formwork heaters. It is shown that under unfavorable conditions the stress level is close to the critical value. The greatest temperature gradient occurs in the outer layers adjacent to the heating formwork. A technology for concrete conditioning is proposed which makes it possible to reduce the temperature stresses along the cross-section of the structure. The time for concrete conditioning in the formwork is reduced. In its turn, it further reduces labor costs and the cost of concrete work along with the cost of

Concrete and criticality

International Nuclear Information System (INIS)

Carter, R.D.

1978-01-01

Concrete is a widely used structural material which occurs frequently in systems requiring criticality analyses. Ordinarily, we give little thought to what its actual composition is (as compared to reference compositions), yet in criticality safety, differences in composition can cause large changes in k-effective and it may not be easy to predict in which direction the change will occur. Concrete composition is quite variable with differences in the aggregate used in the concrete in various parts of the country providing relative large differences in k-effective. The water content of concrete can also strongly affect the reactivity of a system in which it acts as a reflector or is interspersed between fissile units. Because concrete is so common and is often (but not always) a better reflector than water, one must know the concrete compositions or be prepared to use a ''worst case'' composition. It may be a problem, however, to determine just what is the worst case. At the Hanford Plant, the aggregate normally used is basalt, which gives a composition very low in carbon as opposed to those areas (e.g., Oak Ridge) where the use of limestone aggregate will result in concrete with a high carbon content. The data presented show some of the effects found in situations using ''Hanford'' concrete, but similar effects might be found with other compositions. In some cases, the use of concrete may be incidental to the effects shown. While the numbers shown are those for actual systems, the primary intent is to alert the reader that these effects can occur. In applying this information, the analyst should use material specific to the systems being analyzed

Recycled Concrete as Aggregate for Structural Concrete Production

Directory of Open Access Journals (Sweden)

Mirjana Malešev

2010-04-01

Full Text Available A comparative analysis of the experimental results of the properties of fresh and hardened concrete with different replacement ratios of natural with recycled coarse aggregate is presented in the paper. Recycled aggregate was made by crushing the waste concrete of laboratory test cubes and precast concrete columns. Three types of concrete mixtures were tested: concrete made entirely with natural aggregate (NAC as a control concrete and two types of concrete made with natural fine and recycled coarse aggregate (50% and 100% replacement of coarse recycled aggregate. Ninety-nine specimens were made for the testing of the basic properties of hardened concrete. Load testing of reinforced concrete beams made of the investigated concrete types is also presented in the paper. Regardless of the replacement ratio, recycled aggregate concrete (RAC had a satisfactory performance, which did not differ significantly from the performance of control concrete in this experimental research. However, for this to be fulfilled, it is necessary to use quality recycled concrete coarse aggregate and to follow the specific rules for design and production of this new concrete type.

Evaluation of microbially-influenced degradation of massive concrete structures

International Nuclear Information System (INIS)

Hamilton, M.A.; Rogers, R.D.; Zolynski, M.; Veeh, R.

1996-01-01

Many low level waste disposal vaults, both above and below ground, are constructed of concrete. One potential contributing agent to the destruction of concrete structures is microbially-influenced degradation (MID). Three groups of bacteria are known to create conditions that are conducive to destroying concrete integrity. They are sulfur oxidizing bacteria, nitrifying bacteria, and heterotrophic bacteria. Research is being conducted at the Idaho National Engineering Laboratory to assess the extent of naturally occurring microbially influenced degradation (MID) and its contribution to the deterioration of massive concrete structures. The preliminary steps to understanding the extent of MID, require assessing the microbial communities present on degrading concrete surfaces. Ultimately such information can be used to develop guidelines for preventive or corrective treatments for MID and aid in formulation of new materials to resist corrosion. An environmental study was conducted to determine the presence and activity of potential MID bacteria on degrading concrete surfaces of massive concrete structures. Scanning electron microscopy detected bacteria on the surfaces of concrete structures such as bridges and dams, where corrosion was evident. Enumeration of sulfur oxidizing thiobacilli and nitrogen oxidizing Nitrosomonas sp. and Nitrobacter sp. from surface samples was conducted. Bacterial community composition varied between sampling locations, and generally the presence of either sulfur oxidizers or nitrifiers dominated, although instances of both types of bacteria occurring together were encountered. No clear correlation between bacterial numbers and degree of degradation was exhibited

Numerical analysis of pipe impact on reinforced concrete structures

International Nuclear Information System (INIS)

Prinja, N.K.

1990-01-01

This paper presents the methodology and the results of numerical analyses carried out by using the computer code DYNA3D to analyse pipe impacts on a reinforced concrete slab, a floor beam and a column. Modelling techniques employed to represent various features of typical reinforced concrete (RC) structures and the details of a soil and crushable foam type of material model used to represent concrete material behaviour are described. The results show that a reasonable prediction of global behaviour of reinforced concrete structures under impact loading can be obtained by this numerical method. (author)

Sensor Systems for Corrosion Monitoring in Concrete Structures

Directory of Open Access Journals (Sweden)

K.Kumar

2006-05-01

Full Text Available It is a need of permanently embedded corrosion monitoring devices to monitor the progress of corrosion problems on a new or existing reinforced concrete structures before embarking on repair or rehabilitation of the structures. Numerous devices are available for investigating corrosion problems, because no single technique exists which tells an engineer what he needs to know, namely how much damage there is on a structure now and how rapidly the damage will grow with time. In this investigation the studies on the sensors systems based on the measurements of half cell potential of rebars inside the concrete, resistivity of concrete, corrosion rate of rebars by eddy current measurements and sensing of chloride ions are reported. An integrated system consists of above sensors are fabricated and embedded into concrete. The response from each sensor was acquired and analyzed by NI hardware through LabVIEW software.

Seismic analysis for safety related structures of 900MWe PWR NPP

International Nuclear Information System (INIS)

Liu Wei

2002-01-01

Nuclear Power Plant aseismic design becomes more and more important in China due to the fact that China is a country where earthquakes occur frequently and most of plants arc unavoidably located in seismic regions. Therefore, Chinese nuclear safety authority and organizations have worked out a series of regulations and codes related to NPP anti-seismic design taking account of local conditions. The author presents here an example of structural anti-seismic design of 90GM We PWR NPP which is comprised of: ground motion input, including the principles for ground motion determination and time history generation; soil and upper-structure modelling, presenting modeling procedures and typical models of safety related buildings such as Reactor Building, Nuclear Auxiliary Building and Fuel Building; soil-structure interaction analysis; and in-structure response analysis and floor response spectrum generation. With this example, the author intends to give an overview of Chinese practice in NPP structure anti-seismic design such as the main procedures to be followed and the codes and regulations to be respected. (author)

Reliability analysis of prestressed concrete containment structures

International Nuclear Information System (INIS)

Jiang, J.; Zhao, Y.; Sun, J.

1993-01-01

The reliability analysis of prestressed concrete containment structures subjected to combinations of static and dynamic loads with consideration of uncertainties of structural and load parameters is presented. Limit state probabilities for given parameters are calculated using the procedure developed at BNL, while that with consideration of parameter uncertainties are calculated by a fast integration for time variant structural reliability. The limit state surface of the prestressed concrete containment is constructed directly incorporating the prestress. The sensitivities of the Choleskey decomposition matrix and the natural vibration character are calculated by simplified procedures. (author)

Recycled Concrete as Aggregate for Structural Concrete Production

OpenAIRE

Mirjana Malešev; Vlastimir Radonjanin; Snežana Marinković

2010-01-01

A comparative analysis of the experimental results of the properties of fresh and hardened concrete with different replacement ratios of natural with recycled coarse aggregate is presented in the paper. Recycled aggregate was made by crushing the waste concrete of laboratory test cubes and precast concrete columns. Three types of concrete mixtures were tested: concrete made entirely with natural aggregate (NAC) as a control concrete and two types of concrete made with natural fine and recycle...

Study on Detailing Design of Precast Concrete Frame Structure

Science.gov (United States)

Lida, Tian; Liming, Li; Kang, Liu; Jiao, Geng; Ming, Li

2018-03-01

Taking a certain precast concrete frame structure as an example, this paper introduces the general procedures and key points in detailing design of emulative cast-in-place prefabricated structure from the aspects of structural scheme, precast element layout, shop drawing design and BIM 3D modelling. This paper gives a practical solution for the detailing design of precast concrete frame structure under structural design codes in China.

Porous Network Concrete : A bio-inspired building component to make concrete structures self-healing

NARCIS (Netherlands)

Sangadji, S.

2015-01-01

The high energy consumption, its corresponding emission of CO2 and financial losses due to premature failure are the pressing sustainability issues which must be tackled by the concrete infrastructure industry. Enhancement of concrete materials and durability of structures (designing new

Selected Aspects of Computer Modeling of Reinforced Concrete Structures

Directory of Open Access Journals (Sweden)

Szczecina M.

2016-03-01

Full Text Available The paper presents some important aspects concerning material constants of concrete and stages of modeling of reinforced concrete structures. The problems taken into account are: a choice of proper material model for concrete, establishing of compressive and tensile behavior of concrete and establishing the values of dilation angle, fracture energy and relaxation time for concrete. Proper values of material constants are fixed in simple compression and tension tests. The effectiveness and correctness of applied model is checked on the example of reinforced concrete frame corners under opening bending moment. Calculations are performed in Abaqus software using Concrete Damaged Plasticity model of concrete.

Flexural strength of structural concrete repaired with HBPMM cement

International Nuclear Information System (INIS)

Memon, G.H.; Khaskheli, G.B.; Kumar, A.

2009-01-01

To repair damaged concrete structures, Dadabhoy Cement Factory in Sindh has launched a product known as HBPMM (Hi-Bond Polymer Modified Mortar) cement. HBPMM is used to repair various concrete structures in Pakistan but the experimental back up regarding the real performance of the product, as far as flexural strength of concrete is concerned, is not well known yet. This study is thus aimed to investigate the flexural strength of structural concrete repaired with HBPMM compared to that repaired with OPC (Ordinary Portland Cement). In total 32 concrete beams (6x6x18) having compressive strength of 3000 and 5000 psi were manufactured. To obtain flexural strength of the beams, these were splitted by using a UTM (Universal Testing Machine). Beams were then repaired with different applications of HBPMM and OPC. After 28 days of curing, the repaired beams were re-splitted to determine the flexural strength of repaired beams. Results show that both HBPMM and OPC are not very effective. However, the performance of HBPMM remained slightly better than that of OPC. Both OPC and HBPMM remained more efficient in case of 5000 psi concrete than that of 3000 psi concrete. Flexural strength of repaired beams could be increased by increasing application of the repairing material. (author)

Alkali aggregate reactivity in concrete structures in western Canada

International Nuclear Information System (INIS)

Morgan, D.R.; Empey, D.

1989-01-01

In several regions of Canada, particularly parts of Ontario, Quebec and the Maritime Provinces, research, testing and evaluation of aged concrete structures in the field has shown that alkali aggregate reactivity can give rise to pronounced concrete deterioration, particularly in hydraulic structures subjected to saturation or alternate wetting and drying such as locks, dams, canals, etc. Concrete deterioration is mainly caused by alkali-silica reactions and alkali-carbonate reactions, but a third type of deterioration involves slow/late expanding alkali-silicate/silica reactivity. The alkalies NaOH and KOH in the concrete pore solutions are mainly responsible for attack on expansive rocks and minerals in concrete. Methods for evaluating alkali-aggregate reaction potential in aggregates, and field and laboratory methods for detecting deterioration are discussed. Examples of alkali-aggregate reactions in structures is western Canada are detailed, including a water reservoir at Canadian Forces Base Chilliwack in British Columbia, the Oldman River diversion and flume, the Lundbreck Falls Bridge, and the St Mary's Reservoir spillway, all in southern Alberta. Mitigative measures include avoidance of use of suspect aggregates, but if this cannot be avoided it is recommended to keep the total alkalies in the concrete as low as possible and minimize opportunities for saturation of concrete by moisture. 16 refs., 19 figs., 1 tab

A Demonstration of Concrete Structural Health Monitoring Framework for Degradation due to Alkali-Silica Reaction

Energy Technology Data Exchange (ETDEWEB)

Mahadevan, Sankaran [Idaho National Lab. (INL), Idaho Falls, ID (United States); Agarwal, Vivek [Idaho National Lab. (INL), Idaho Falls, ID (United States); Neal, Kyle [Idaho National Lab. (INL), Idaho Falls, ID (United States); Nath, Paromita [Idaho National Lab. (INL), Idaho Falls, ID (United States); Bao, Yanqing [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cai, Guowei [Idaho National Lab. (INL), Idaho Falls, ID (United States); Orme, Peter [Idaho National Lab. (INL), Idaho Falls, ID (United States); Adams, Douglas [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kosson, David [Idaho National Lab. (INL), Idaho Falls, ID (United States)

2016-04-01

Assessment and management of aging concrete structures in nuclear power plants require a more systematic approach than simple reliance on existing code margins of safety. Structural health monitoring of concrete structures aims to understand the current health condition of a structure based on heterogeneous measurements to produce high-confidence actionable information regarding structural integrity that supports operational and maintenance decisions. This ongoing research project is seeking to develop a probabilistic framework for health diagnosis and prognosis of aging concrete structures in a nuclear power plant that is subjected to physical, chemical, environment, and mechanical degradation. The proposed framework consists of four elements: monitoring, data analytics, uncertainty quantification and prognosis. This report focuses on degradation caused by ASR (alkali-silica reaction). Controlled specimens were prepared to develop accelerated ASR degradation. Different monitoring techniques – thermography, digital image correlation (DIC), mechanical deformation measurements, nonlinear impact resonance acoustic spectroscopy (NIRAS), and vibro-acoustic modulation (VAM) -- were used to detect the damage caused by ASR. Heterogeneous data from the multiple techniques was used for damage diagnosis and prognosis, and quantification of the associated uncertainty using a Bayesian network approach. Additionally, MapReduce technique has been demonstrated with synthetic data. This technique can be used in future to handle large amounts of observation data obtained from the online monitoring of realistic structures.

Bond-Slip Behavior of Basalt Fiber Reinforced Polymer Bar in Concrete Subjected to Simulated Marine Environment: Effects of BFRP Bar Size, Corrosion Age, and Concrete Strength

OpenAIRE

Yongmin Yang; Zhaoheng Li; Tongsheng Zhang; Jiangxiong Wei; Qijun Yu

2017-01-01

Basalt Fiber Reinforced Polymer (BFRP) bars have bright potential application in concrete structures subjected to marine environment due to their superior corrosion resistance. Available literatures mainly focused on the mechanical properties of BFRP concrete structures, while the bond-slip behavior of BFRP bars, which is a key factor influencing the safety and service life of ocean concrete structures, has not been clarified yet. In this paper, effects of BFRP bars size, corrosion age, and c...

A method for three-dimensional structural analysis of reinforced concrete containment

International Nuclear Information System (INIS)

Kulak, R.F.; Fiala, C.

1989-01-01

A finite element method designed to assist reactor safety analysts in the three-dimensional numerical simulation of reinforced concrete containments to normal and off-normal mechanical loadings is presented. The development of a lined reinforced concrete plate element is described in detail, and the implementation of an empirical transverse shear failure criteria is discussed. The method is applied to the analysis of a 1/6th scale reinforced concrete containment model subjected to static internal pressurization. 11 refs., 14 figs., 1 tab

Preliminary Study on Impact Resistances of Fiber Reinforced Concrete Applied Nuclear Power Plants

International Nuclear Information System (INIS)

Jin, Byeong Moo; Kim, Young Jin; Jeon, Se Jin

2013-01-01

Studies to improve the impact resistance depending upon design parameters for fiber reinforced concrete, such as type of fibers and application ratio, are in progress. Authors assessed first the impact resistance of concrete walls depending upon fiber types and missile impact velocities. The safety assessment of nuclear power plants against large civil aircraft crashes have been accomplished for normal concrete and fiber reinforced concretes in this study. Studies on the safety assessments on the nuclear power plants against large civil aircraft crashes are ongoing actively. As a step of evaluating the applicability of fiber reinforced concrete in means of ensuring more structural safety of the nuclear power plants against impact, the impact resistance for the 1% steel and 2% polyamide fiber reinforced concretes have been evaluated. For reactor containment building structures, it seem there is no impact resistance enhancement of fiber reinforced concrete applied to reactor containment building in the cases of impact velocity 150 m/sec considered in this study. However this results from the pre-stressing forces which introduce compressive stresses in concrete wall and dome section of reactor containment building. Nonetheless there may be benefits to apply fiber reinforced concrete to nuclear power plants. For double containment type reactor containment building, the outer structure is a reinforced concrete structure. The impact resistances for non pre-stressed cylindrical reactor containment buildings are enhanced by 23 to 47 % for 2 % polyamide fiber reinforced concretes and 1 % steel fiber reinforced concretes respectively. For other buildings such as auxiliary building, compound building and fuel storage building surrounding the reactor containment building, there are so many reinforced concrete walls which are anticipated some enhancements of impact resistance by using fiber reinforced concretes. And heavier or faster large civil aircraft impacts produce higher

Preliminary Study on Impact Resistances of Fiber Reinforced Concrete Applied Nuclear Power Plants

Energy Technology Data Exchange (ETDEWEB)

Jin, Byeong Moo; Kim, Young Jin; Jeon, Se Jin [Daewoo E and C Co. Ltd., Suwon (Korea, Republic of)

2013-10-15

Studies to improve the impact resistance depending upon design parameters for fiber reinforced concrete, such as type of fibers and application ratio, are in progress. Authors assessed first the impact resistance of concrete walls depending upon fiber types and missile impact velocities. The safety assessment of nuclear power plants against large civil aircraft crashes have been accomplished for normal concrete and fiber reinforced concretes in this study. Studies on the safety assessments on the nuclear power plants against large civil aircraft crashes are ongoing actively. As a step of evaluating the applicability of fiber reinforced concrete in means of ensuring more structural safety of the nuclear power plants against impact, the impact resistance for the 1% steel and 2% polyamide fiber reinforced concretes have been evaluated. For reactor containment building structures, it seem there is no impact resistance enhancement of fiber reinforced concrete applied to reactor containment building in the cases of impact velocity 150 m/sec considered in this study. However this results from the pre-stressing forces which introduce compressive stresses in concrete wall and dome section of reactor containment building. Nonetheless there may be benefits to apply fiber reinforced concrete to nuclear power plants. For double containment type reactor containment building, the outer structure is a reinforced concrete structure. The impact resistances for non pre-stressed cylindrical reactor containment buildings are enhanced by 23 to 47 % for 2 % polyamide fiber reinforced concretes and 1 % steel fiber reinforced concretes respectively. For other buildings such as auxiliary building, compound building and fuel storage building surrounding the reactor containment building, there are so many reinforced concrete walls which are anticipated some enhancements of impact resistance by using fiber reinforced concretes. And heavier or faster large civil aircraft impacts produce higher

Review of Repair Materials for Fire-Damaged Reinforced Concrete Structures

Science.gov (United States)

Zahid, MZA Mohd; Abu Bakar, BH; Nazri, FM; Ahmad, MM; Muhamad, K.

2018-03-01

Reinforced concrete (RC) structures perform well during fire and may be repaired after the fire incident because their low heat conductivity prevents the loss or degradation of mechanical strength of the concrete core and internal reinforcing steel. When an RC structure is heated to more than 500 °C, mechanical properties such as compressive strength, stiffness, and tensile strength start to degrade and deformations occur. Although the fire-exposed RC structure shows no visible damage, its residual strength decreases compared with that in the pre-fire state. Upon thorough assessment, the fire-damaged RC structure can be repaired or strengthened, instead of subjecting to partial or total demolition followed by reconstruction. The structure can be repaired using several materials, such as carbon fiber-reinforced polymer, glass fiber-reinforced polymer, normal strength concrete, fiber-reinforced concrete, ferrocement, epoxy resin mortar, and high-performance concrete. Selecting an appropriate repair material that must be compatible with the substrate or base material is a vital step to ensure successful repair. This paper reviews existing repair materials and factors affecting their performance. Of the materials considered, ultra-high-performance fiber-reinforced concrete (UHPFRC) exhibits huge potential for repairing fire-damaged RC structures but lack of information available. Hence, further studies must be performed to assess the potential of UHPFRC in rehabilitating fire-damaged RC structures.

Containment performance evaluation of prestressed concrete containment vessels with fiber reinforcement

Energy Technology Data Exchange (ETDEWEB)

Choun, Young Sun; Park, Hyung Kui [Integrated Safety Assessment Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-12-15

Fibers in concrete resist the growth of cracks and enhance the postcracking behavior of structures. The addition of fibers into a conventional reinforced concrete can improve the structural and functional performance of safety-related concrete structures in nuclear power plants. The influence of fibers on the ultimate internal pressure capacity of a prestressed concrete containment vessel (PCCV) was investigated through a comparison of the ultimate pressure capacities between conventional and fiber-reinforced PCCVs. Steel and polyamide fibers were used. The tension behaviors of conventional concrete and fiber-reinforced concrete specimens were investigated through uniaxial tension tests and their tension-stiffening models were obtained. For a PCCV reinforced with 1% volume hooked-end steel fiber, the ultimate pressure capacity increased by approximately 12% in comparison with that for a conventional PCCV. For a PCCV reinforced with 1.5% volume polyamide fiber, an increase of approximately 3% was estimated for the ultimate pressure capacity. The ultimate pressure capacity can be greatly improved by introducing steel and polyamide fibers in a conventional reinforced concrete. Steel fibers are more effective at enhancing the containment performance of a PCCV than polyamide fibers. The fiber reinforcement was shown to be more effective at a high pressure loading and a low prestress level.

Containment performance evaluation of prestressed concrete containment vessels with fiber reinforcement

International Nuclear Information System (INIS)

Choun, Young Sun; Park, Hyung Kui

2015-01-01

Fibers in concrete resist the growth of cracks and enhance the postcracking behavior of structures. The addition of fibers into a conventional reinforced concrete can improve the structural and functional performance of safety-related concrete structures in nuclear power plants. The influence of fibers on the ultimate internal pressure capacity of a prestressed concrete containment vessel (PCCV) was investigated through a comparison of the ultimate pressure capacities between conventional and fiber-reinforced PCCVs. Steel and polyamide fibers were used. The tension behaviors of conventional concrete and fiber-reinforced concrete specimens were investigated through uniaxial tension tests and their tension-stiffening models were obtained. For a PCCV reinforced with 1% volume hooked-end steel fiber, the ultimate pressure capacity increased by approximately 12% in comparison with that for a conventional PCCV. For a PCCV reinforced with 1.5% volume polyamide fiber, an increase of approximately 3% was estimated for the ultimate pressure capacity. The ultimate pressure capacity can be greatly improved by introducing steel and polyamide fibers in a conventional reinforced concrete. Steel fibers are more effective at enhancing the containment performance of a PCCV than polyamide fibers. The fiber reinforcement was shown to be more effective at a high pressure loading and a low prestress level

Topology Optimization for Conceptual Design of Reinforced Concrete Structures

DEFF Research Database (Denmark)

Amir, Oded; Bogomolny, Michael

2011-01-01

Design of reinforced concrete structures is governed by the nonlinear behavior of concrete and by its dierent strengths in tension and compression. The purpose of this article is to present a computational procedure for optimal conceptual design of reinforced concrete structures, based on topology...... must be consid- ered. Optimized distribution of material is achieved by introducing interpolation rules for both elastic and plastic material properties. Several numerical examples illustrate the capability and potential of the proposed procedure....

Evaluation of seismic shear capacity of prestressed concrete containment vessels with fiber reinforcement

Energy Technology Data Exchange (ETDEWEB)

Choun, Young Sun; Park, Jun Hee [Integrated Safety Assessment Division, Korea Atomic Energy Research Institute, Daejeon (Korea, Republic of)

2015-10-15

Fibers have been used in cement mixture to improve its toughness, ductility, and tensile strength, and to enhance the cracking and deformation characteristics of concrete structural members. The addition of fibers into conventional reinforced concrete can enhance the structural and functional performances of safety-related concrete structures in nuclear power plants. The effects of steel and polyamide fibers on the shear resisting capacity of a prestressed concrete containment vessel (PCCV) were investigated in this study. For a comparative evaluation between the shear performances of structural walls constructed with conventional concrete, steel fiber reinforced concrete, and polyamide fiber reinforced concrete, cyclic tests for wall specimens were conducted and hysteretic models were derived. The shear resisting capacity of a PCCV constructed with fiber reinforced concrete can be improved considerably. When steel fiber reinforced concrete contains hooked steel fibers in a volume fraction of 1.0%, the maximum lateral displacement of a PCCV can be improved by > 50%, in comparison with that of a conventional PCCV. When polyamide fiber reinforced concrete contains polyamide fibers in a volume fraction of 1.5%, the maximum lateral displacement of a PCCV can be enhanced by ∼40%. In particular, the energy dissipation capacity in a fiber reinforced PCCV can be enhanced by > 200%. The addition of fibers into conventional concrete increases the ductility and energy dissipation of wall structures significantly. Fibers can be effectively used to improve the structural performance of a PCCV subjected to strong ground motions. Steel fibers are more effective in enhancing the shear performance of a PCCV than polyamide fibers.

Evaluation of seismic shear capacity of prestressed concrete containment vessels with fiber reinforcement

International Nuclear Information System (INIS)

Choun, Young Sun; Park, Jun Hee

2015-01-01

Fibers have been used in cement mixture to improve its toughness, ductility, and tensile strength, and to enhance the cracking and deformation characteristics of concrete structural members. The addition of fibers into conventional reinforced concrete can enhance the structural and functional performances of safety-related concrete structures in nuclear power plants. The effects of steel and polyamide fibers on the shear resisting capacity of a prestressed concrete containment vessel (PCCV) were investigated in this study. For a comparative evaluation between the shear performances of structural walls constructed with conventional concrete, steel fiber reinforced concrete, and polyamide fiber reinforced concrete, cyclic tests for wall specimens were conducted and hysteretic models were derived. The shear resisting capacity of a PCCV constructed with fiber reinforced concrete can be improved considerably. When steel fiber reinforced concrete contains hooked steel fibers in a volume fraction of 1.0%, the maximum lateral displacement of a PCCV can be improved by > 50%, in comparison with that of a conventional PCCV. When polyamide fiber reinforced concrete contains polyamide fibers in a volume fraction of 1.5%, the maximum lateral displacement of a PCCV can be enhanced by ∼40%. In particular, the energy dissipation capacity in a fiber reinforced PCCV can be enhanced by > 200%. The addition of fibers into conventional concrete increases the ductility and energy dissipation of wall structures significantly. Fibers can be effectively used to improve the structural performance of a PCCV subjected to strong ground motions. Steel fibers are more effective in enhancing the shear performance of a PCCV than polyamide fibers

Probabilistic Analysis of Structural Member from Recycled Aggregate Concrete

Science.gov (United States)

Broukalová, I.; Šeps, K.

2017-09-01

The paper aims at the topic of sustainable building concerning recycling of waste rubble concrete from demolition. Considering demands of maximising recycled aggregate use and minimising of cement consumption, composite from recycled concrete aggregate was proposed. The objective of the presented investigations was to verify feasibility of the recycled aggregate cement based fibre reinforced composite in a structural member. Reliability of wall from recycled aggregate fibre reinforced composite was assessed in a probabilistic analysis of a load-bearing capacity of the wall. The applicability of recycled aggregate fibre reinforced concrete in structural applications was demonstrated. The outcomes refer to issue of high scatter of material parameters of recycled aggregate concretes.

A study on the water permeability of concrete structures

International Nuclear Information System (INIS)

Loadsman, R.V.C.; Acres, D.H.; Stokes, C.J.; Wadeson, L.

1988-03-01

This report forms part of the DoE's research programme on the disposal of nuclear waste. The information available on the permeability of concrete and the effects of various factors on this value are reviewed. The effect of defects on the overall permeability of concrete structures is examined and the recorded performance of a range of existing concrete structures is considered with identification of some of the factors that are significant in practice. Deficiencies in the information available on this subject are identified and recommendations for further work are made including a list of structures suitable for future monitoring. (author)

Condition monitoring and maintenance of nuclear power plant concrete structures

International Nuclear Information System (INIS)

Orr, R.; Prasad, N.

1988-01-01

Nuclear power plant concrete structures are potentially subject to deterioration due to several environmental conditions, including weather exposure, ground water exposure, and sustained high temperature and radiation levels. The nuclear power plant are generally licensed for a term of 40 years. In order to maximize the return from the existing plants, feasibility studies are in progress for continued operation of many of these plants beyond the original licensed life span. This paper describes a study that was performed with an objective to define appropriate condition monitoring and maintenance procedures. A timely implementation of a condition monitoring and maintenance program would provide a valuable database and would provide justification for extension of the plant's design life. The study included concrete structures such as the containment buildings, interior structures, basemats, intake structures and cooling towers. Age-related deterioration at several operating power plants was surveyed and the potential degradation mechanisms have been identified

EFFECT OF ELEVATED TEMPERATURE ON COMPRESSIVE STRENGTH OF FIBER REINFORCED CONCRETE

OpenAIRE

Prashant shinkar*, Prof. Deepak kakade, Dr.A.P.Wadekar

2017-01-01

This paper deals with the mechanical properties of concrete with steel fibers subjected to temperatures up to 500°C. Now a day concrete are being used extensively in the construction that might be subjected to elevated temperatures. The behavior of concrete structures at elevated temperatures is of significant importance in predicting the safety of structures in response to certain accidents or particular service conditions. Concrete mixes of M 50 have been designed along with steel fibers fr...

Nonlinear analysis of reinforced concrete structures using software package abaqus

OpenAIRE

Marković Nemanja; Stojić Dragoslav; Cvetković Radovan

2014-01-01

Reinforced concrete (AB) is characterized by huge inhomogeneity resulting from the material characteristics of the concrete, then, quasi-brittle behavior during failure. These and other phenomena require the introduction of material nonlinearity in the modeling of reinforced concrete structures. This paper presents the modeling reinforced concrete in the software package ABAQUS. A brief theoretical overview is presented of methods such as: Concrete Damage Plasticity (CDP), Smeared Concrete Cr...

Development of heat resistant concrete and its application to concrete casks. Improvement of neutron shielding performance of concrete in high temperature environment

International Nuclear Information System (INIS)

Owaki, Eiji; Hata, Akihito; Sugihara, Yutaka; Shimojo, Jun; Taniuchi, Hiroaki; Mantani, Kenichi

2003-01-01

Heat resistant concrete with hydrogen, which is able to shield neutron at more than 100degC, was developed. Using this new type concrete, a safety concrete cask having the same concept of metal casks was designed and produced. The new type cask omitted the inhalation and exhaust vent of the conventional type concrete casks. The new concrete consists of Portland cement added calcium hydroxide, iron powder and iron fiber. It showed 2.17 g/cm 3 density, 10.8 mass% water content, 1.4 W/(m·K) thermal conductivity at 150degC. Increasing of heat resistance made possible to produce the perfect sealing type structure, which had high shielding performance of radiation no consideration for streaming of radiation. Moreover, a monitor of sealing can be set. General view of concrete casks, outer view of 1/3 scaled model, cask storage system in the world, properties of new developed heat resistant concrete, results of shielding calculation are contained. (S.Y.)

Integrity of Safety-Related Fast Reactor Structures

International Nuclear Information System (INIS)

Rose, R.T.; Tomkins, B.

1981-01-01

The LMFBR contains several structural items whose integrity must be safeguarded during the life of the plant. These items include the main core support structures (strongback, diagrid) and the primary tank to which these structures are attached. In order to demonstrate an acceptable level of structural integrity, the chosen design philosophy must be supported by both analytical and experimental evidence. This paper describes the current approaches in the UK to these requirements. Section 2 describes the materials mechanical properties tests performed to date on both fracture toughness and fatigue crack growth in Type 316 austenitic stainless steel plate and weldments. This data illustrates the problems in identifying the relevant materials fracture parameters for use in assessments. Section 3 shows the test programmes in hand to extend the materials programmes to tests on structural features (mainly welded wide plate tests) which incorporate the complexity of weldments in a structural context. This includes experimental evidence on the effects of local weld residual stresses on structural failure. Various routes are open for the integrity assessment of FR structures. These are discussed in Section 4 but in effect they reduce to a fracture mechanics approach using some technique to cope with elastic-plastic fracture. The main problems at present relate to our ability in analysis to cope with residual stresses and the post-initiation region of the fracture resistance curve. Also, there is the problem of initial defect sizing by current NDE techniques. Current conservative analytical assessments give acceptable defect sizes of order a few millimetres in irradiated weldments. Finally, Section 5 discusses the options open in design to cope with safety related structures under normal and abnormal loading conditions. It is clear that several options exist in design to satisfy the demand for high integrity

Performance of Hydrophobisation Techniques in Case of Reinforced Concrete Structures

Science.gov (United States)

Błaszczyński, Tomasz; Osesek, Mateusz; Gwozdowski, Błażej; Ilski, Mirosław

2017-10-01

Concrete is, unchangeably, one of the most frequently applied building materials, also in the case of bridges, overpasses or viaducts. Along with the aging of such structures, the degradation of concrete, which may accelerate the corrosion of reinforcing steel and drastically decrease the load-bearing capacity of the structure, becomes an important issue. The paper analyzes the possibilities of using deep hydrophobisation in repairing reinforced concrete engineering structures. The benefits of properly securing reinforced concrete structures from the damaging effects of UV radiation, the influence of harmful gases, or progression of chlorine induced corrosion have been presented, especially in regards to bridge structures. The need to calculate the costs of carrying out investments along with the expected costs of maintaining such structures, as well as the high share of costs connected with logistics, has also been indicated in the total costs of repair works.

Ageing management of CANDUtm concrete containment buildings

International Nuclear Information System (INIS)

Philipose, K.E.; Gregor, F.E.

2009-01-01

The containment system in a Nuclear Power Plant (NPP) provides the final physical barrier against release of radioactive materials to the external environment. Even though there are different physical configurations to meet this fundamental safety function in various reactor types, a common feature is the use of a thick-walled concrete structure as part of the containment system commonly referred to as 'Concrete Containment Building'. In order for the concrete containment buildings to continue to provide the required safety function, it has to maintain its structural integrity. As well, its leak rates under test pressures must be maintained below acceptable limits. As some of the containment buildings of the CANDU nuclear power plants are approaching their fourth decade of successful operation, questions regarding the impact of ageing on their ultimate useful service life emerge. Ageing Management has become the tool for addressing those questions. In this paper, the ageing and ageing management of the CANDU concrete containments are discussed, including the specific programs being implemented to monitor and trend the ageing conditions. Specifically, the usefulness of the embedded strain gauges as a tool for the assessment of the condition of the containment concrete structure is discussed. Some of the operational and test data accumulated over the last 30 years have been evaluated and trended to provide some results and conclusions regarding the satisfactory long-term behaviour of the concrete containment buildings. (authors)

Concrete containment modeling and management, Conmod

International Nuclear Information System (INIS)

Jovall, O.; Larsson, J.-A.; Shaw, P.; Touret, J.-P.; Karlberg, G.

2003-01-01

The CONMOD project aims to create a system which will ensure that safety requirements for concrete containment structures will be up-held during the entire planned lifetime of plants and possibly during an extended lifetime. An important part of the project is to develop the application and understanding of Non-Destructive Testing (NDT) techniques for the assessment of conformity and condition of concrete reactor containments and to integrate this with state-of-the-art and developed Finite Element (FE) modelling techniques and analysis of structural behaviour. The objective being to create a diagnostic method for evaluation of ageing and degradation of concrete containments. This method, the C ONMOD-methodology , will help in the planning and execution of actions that will improve safety in a manner which is optimal both in terms of economy and safety. The knowledge gained during the project will be presented in a handbook of best practice. The decommissioned Barsebaeck unit 1 reactor containment will be accessible for non-destructive examination throughout the duration of the project. Intrusive investigations will also be made including coring and material tests as a valuable complement to NDT. (author)

Primer on Durability of Nuclear Power Plant Reinforced Concrete Structures - A Review of Pertinent Factors

Energy Technology Data Exchange (ETDEWEB)

Naus, Dan J [ORNL

2007-02-01

The objective of this study was to provide a primer on the environmental effects that can affect the durability of nuclear power plant concrete structures. As concrete ages, changes in its properties will occur as a result of continuing microstructural changes (i.e., slow hydration, crystallization of amorphous constituents, and reactions between cement paste and aggregates), as well as environmental influences. These changes do not have to be detrimental to the point that concrete will not be able to meet its performance requirements. Concrete, however, can suffer undesirable changes with time because of improper specifications, a violation of specifications, or adverse performance of its cement paste matrix or aggregate constituents under either physical or chemical attack. Contained in this report is a discussion on concrete durability and the relationship between durability and performance, a review of the historical perspective related to concrete and longevity, a description of the basic materials that comprise reinforced concrete, and information on the environmental factors that can affect the performance of nuclear power plant concrete structures. Commentary is provided on the importance of an aging management program.

Primer on Durability of Nuclear Power Plant Reinforced Concrete Structures - A Review of Pertinent Factors

International Nuclear Information System (INIS)

Naus, Dan J.

2007-01-01

The objective of this study was to provide a primer on the environmental effects that can affect the durability of nuclear power plant concrete structures. As concrete ages, changes in its properties will occur as a result of continuing microstructural changes (i.e., slow hydration, crystallization of amorphous constituents, and reactions between cement paste and aggregates), as well as environmental influences. These changes do not have to be detrimental to the point that concrete will not be able to meet its performance requirements. Concrete, however, can suffer undesirable changes with time because of improper specifications, a violation of specifications, or adverse performance of its cement paste matrix or aggregate constituents under either physical or chemical attack. Contained in this report is a discussion on concrete durability and the relationship between durability and performance, a review of the historical perspective related to concrete and longevity, a description of the basic materials that comprise reinforced concrete, and information on the environmental factors that can affect the performance of nuclear power plant concrete structures. Commentary is provided on the importance of an aging management program

Thermal stress-dependent dilation of concrete

International Nuclear Information System (INIS)

Pfeiffer, P.A.; Marchertas, A.H.

1984-01-01

Recent studies in nuclear fast reactor safety consider the possibility of concrete containment being subjected to extremely severe environmental conditions. Certain safety scenarios subject the concrete to very high temperatures hence raising the concern of containment integrity. Some of the main detrimental effects of high temperature on concrete are: reduction of strength, redistribution of moisture and etc. Consequently, analytical prediction of concrete response under the high temperature conditions becomes very complex. A rather simple but important experiment of concrete at high temperatures was conducted by Anderberg and Thelandersson. The test samples were small so that moisture was free to evaporate with no appreciable gradient as the temperature increased. Their results revealed that good correlation with analysis could be obtained if thermal expansion was made a function of both temperature and stress. The method of relating the thermal strain to temperature and stress has been integrated into the TEMP-STRESS code. Thus, high temperature concrete computational capability is now available for thermal-stress calculations

Mathematical modeling of vibration processes in reinforced concrete structures for setting up crack initiation monitoring

Science.gov (United States)

Bykov, A. A.; Matveenko, B. P.; Serovaev, G. S.; Shardakov, I. N.; Shestakov, A. P.

2015-03-01

The contemporary construction industry is based on the use of reinforced concrete structures, but emergency situations resulting in fracture can arise in their exploitation. In a majority of cases, reinforced concrete fracture is realized as the process of crack formation and development. As a rule, the appearance of the first cracks does not lead to the complete loss of the carrying capacity but is a fracture precursor. One method for ensuring the safe operation of building structures is based on crack initiation monitoring. A vibration method for the monitoring of reinforced concrete structures is justified in this paper. An example of a reinforced concrete beam is used to consider all stages related to the analysis of the behavior of natural frequencies in the development of a crack-shaped defect and the use of the obtained numerical results for the vibration test method. The efficiency of the method is illustrated by the results of modeling of the physical part of the method related to the analysis of the natural frequency evolution as a response to the impact action in the crack development process.

Soft projectile impacts on thin reinforced concrete slabs: tests, modelling and simulations

International Nuclear Information System (INIS)

Pontiroli, C.; Rouquand, A.

2011-01-01

Numerical simulations of reinforced concrete structures subjected to high velocity impacts and explosions remain a difficult task today. Since ten years and more now, the CEA-Gramat has maintained a continuous research effort with the help of different French universities in order to overcome encountered difficulties in modelling the behaviour of concrete structures under severe loading. These difficulties are related to numerical aspects (convergence difficulties of the non linear stress strain relation in 3D configuration, efficiency of the numerical procedure and robustness), but also due to the ability of the material model to simulate the accurately behaviour of a very complex and heterogeneous material like concrete. A new concrete model, named PRM model, has been developed at CEA-Gramat (Pontiroli, Rouquand and Mazars) to predict the concrete response under a large range of dynamic loadings. Works presented in this paper have been performed in the framework of the French VULCAIN PGCU 2007 research project (founded by the French National Research Agency). This project aims at defining a theoretical and probabilistic methodology in order to assess the structural safety of industrial structures that might be submitted to transient loadings such as blasts or impacts generated by various projectiles. A complementary objective is to improve diagnosis, prevention or protection actions. This scientific program gathers well-known and complementary scientific institutes, firms and universities in France. (authors)

Effect of Water-Cement Ratio on Pore Structure and Strength of Foam Concrete

Directory of Open Access Journals (Sweden)

Zhongwei Liu

2016-01-01

Full Text Available Foam concrete with different dry densities (400, 500, 600, 700, and 800 kg/m3 was prepared from ordinary Portland cement (P.O.42.5R and vegetable protein foaming agent by adjusting the water-cement ratio through the physical foaming method. The performance of the cement paste adopted, as well as the structure and distribution of air pores, was characterized by a rheometer, scanning electron microscope, vacuum water saturation instrument, and image analysis software. Effects of the water-cement ratio on the relative viscosity of the cement paste, as well as pore structure and strength of the hardened foam concrete, were discussed. Results showed that water-cement ratio can influence the size, distribution, and connectivity of pores in foam concrete. The compressive strength of the foam concrete showed an inverted V-shaped variation law with the increase in water-cement ratio.

Final report on characterization of time dependent deformations in concrete grades used in nuclear power plants

International Nuclear Information System (INIS)

Ramaswamy, Ananth; Chandra Kishen, J.M.

2009-09-01

Time dependent deformations in concrete, both creep and shrinkage, play a critical role in prestressed concrete structures, such as bridge girders, nuclear containment vessels, etc. These strains result in losses, through release of prestress, and thereby influence the safety of these structures. The present study comprises of an experimental and analytical program to assess the levels of creep and shrinkage in normal and heavy density concrete. The experimental program includes tests on creep using standard cylinder specimen, while shrinkage studies have been conducted using prism specimen, both under controlled environmental conditions. The experimental results suggest that creep and shrinkage strains are higher in heavy density concrete than in normal concrete. This may be attributed to the relatively smaller pore structure of heavy density concrete that results in larger availability of free water and a relatively slower hydration process in comparison to normal concrete. While there is some scatter in the results, creep strains decrease with age of loading and both creep and shrinkage strains are smaller when the relative humidity is higher. Statistical model reported in the literature for normal concrete is able to predict the test results for both normal and heavy density concrete quite well. Long term predictions of creep and shrinkage using this model, accounting for uncertainties, is also projected and shown to predict some long term measured results not used in the model calibration. The long term predictions are sensitive to the initial data used in model calibration. (author)

Processing disaster debris liberating aggregates for structural concrete

NARCIS (Netherlands)

van de Wouw, P.M.F.; Florea, M.V.A.; Brouwers, H.J.H.; Schmidt, W.; Msinjili, N.S.

2016-01-01

Worldwide, the removal of debris and reconstruction is requested when natural disasters and conflicts cause damaged or collapsed buildings. The on-site recycling of concrete waste into new structural concrete decreases transport and production energy costs, reduces the utilization of raw materials,

Prestressing of reinforcing bars in concrete slabs due to concrete expansion induced by Alkali-Silica Reaction

DEFF Research Database (Denmark)

Gustenhoff Hansen, Søren; Antonio Barbosa, Ricardo; Hoang, Linh Cao

2017-01-01

Alkali-silica reactions (ASR) in concrete bridges have been a major concern worldwide for many decades. In Denmark, several bridges are severely damaged due to ASR and over 600 bridges have the potential to develop ASR in the future. The majority of these bridges are slab-bridges. Despite the many...... cases, experimental research on structural safety and residual load carrying capacity of ASR-damaged bridges is limited. As ASR causes severe cracks in the concrete, which may affect the concrete compressive and tensile strength, concerns have been directed towards the residual shear capacity. Yet...

Experimental research into the relation between the peeling angle and the debonding of CFRP laminates bonded to concrete

NARCIS (Netherlands)

Klamer, E.L.

2004-01-01

CFRP is a relatively new, innovative strengthening material to strengthen reinforced concrete structures. Main issue, when strengthening a concrete structure is the debonding of CFRP. Although a lot of research has been carried out into the debonding behavior, still some questions remain open. In

Progress in research on aging of structures

International Nuclear Information System (INIS)

Naus, D.J.; Oland, C.B.; Ellingwood, B.; Mori, Y.; Arndt, E.G.

1991-01-01

The Structural Aging (SAG) Program is conducted for the Nuclear Regulatory Commission. The program has the overall objective of preparing an expandable handbook or report which will provide the NRC with potential structural safety issues and acceptance criteria for use in nuclear power plant evaluations for continued service. Initial focus of the program is on concrete and concrete-related materials which comprise the safety-related (Category I) structures in light-water reactor facilities. The program consists of a management task and three technical tasks: materials property data base, structural component assessment/repair technology, and quantitative methodology for continued service determinations. Objectives, background information, and accomplishments under each of these tasks are presented

Prevention of shrinkage cracking in tight concrete structures

International Nuclear Information System (INIS)

Alvaredo, A.M.; Wittmann, F.H.

1995-01-01

It is shown that crack formation and propagation in concrete members subjected to restrained shrinkage can be realistically predicted by means of a comprehensive approach including a diffusion analysis and fracture mechanics considerations. The conditions for stable crack propagation regarding dimensions of the concrete member, degree of restraint to the imposed deformation and material properties are discussed. Guidelines on the prevention of shrinkage cracking of concrete structures are given. (author). 10 refs., 5 figs

Structural-functional integrated concrete with macro-encapsulated inorganic PCM

Science.gov (United States)

Mohseni, Ehsan; Tang, Waiching; Wang, Zhiyu

2017-09-01

Over the last few years the application of thermal energy storage system incorporating phase change materials (PCMs) to foster productivity and efficiency of buildings energy has grown rapidly. In this study, a structural-functional integrated concrete was developed using macro-encapsulated PCM-lightweight aggregate (LWA) as partial replacement (25 and 50% by volume) of coarse aggregate in control concrete. The PCM-LWA was prepared by incorporation of an inorganic PCM into porous LWAs through vacuum impregnation. The mechanical and thermal performance of PCM-LWA concrete were studied. The test results revealed that though the compressive strength of concrete with PCM-LWA was lower than the control concrete, but ranged from 22.02 MPa to 42.88 MPa which above the minimum strength requirement for structural application. The thermal performance test indicated that macro-encapsulated PCM-LWA has underwent the phase change transition reducing the indoor temperature.

Importance of modeling beam-column joints for seismic safety of reinforced concrete structures

International Nuclear Information System (INIS)

Sharma, Akanshu; Reddy, G.R.; Vaze, K.K.; Eligehausen, R.; Hofmann, J.

2011-01-01

Almost all structures, except the containment building, in a NPP can be classified as reinforced concrete (RC) framed structures. In case of such structures subjected to seismic loads, beam-column joints are recognized as the critical and vulnerable zone. During an earthquake, the global behavior of the structure is highly governed by the behavior of the joints. If the joints behave in a ductile manner, the global behavior generally will be ductile, whereas if the joints behave in a brittle fashion then the structure will display a brittle behavior. The joints of old and non-seismically detailed structures are more vulnerable and behave poorly under the earthquakes compared to the joints of new and seismically detailed structures. Modeling of these joint regions is very important for correct assessment of the seismic performance of the structures. In this paper, it is shown with the help of a recently developed joint model that not modeling the inelastic behavior of the joints can lead to significantly misleading and unsafe results in terms of the performance assessment of the structures under seismic loads. Comparison of analytical and experimental results is shown for two structures, tested under lateral monotonic seismic pushover loads. It is displayed that the model can predict the inelastic seismic response of structures considering joint distortion with high accuracy by little extra effort in modeling. (author)

Ageing management of nuclear power plant concrete structures - Overview and suggested research topics

International Nuclear Information System (INIS)

Naus, J.

2009-01-01

Nuclear power plant concrete structures are described and their operating experience noted. Primary considerations related to management of their ageing are noted and an indication of their status provided: degradation mechanisms, damage models, and material performance; assessment and remediation (i.e., component selection, in-service inspection, non-destructive examinations, and remedial actions); and estimation of performance at present or some future point in time (i.e., application of structural reliability theory to the design and optimisation of in-service inspection/maintenance strategies, and determination of the effects of degradation on plant risk). Several activities are identified that provide background information and data on areas of concern with respect to non-destructive examination of nuclear power plant concrete structures: inspection of thick-walled, heavily-reinforced sections; basemat; and inaccessible areas of the containment metallic pressure boundary. Topics are noted where additional research would be of benefit to ageing management of nuclear power plant concrete structures. (author)

Impact design of reinforced concrete fuel storage structures

International Nuclear Information System (INIS)

Nickell, R.E.; Rashid, Y.R.; Williams, R.F.

1987-01-01

We characterize the loading experienced by reinforced concrete slabs, as the result of a drop or a tip-over of a dry storage cask, and we provide simple design charts and formulas by which the margin of safety of such slabs can be readily demonstrated. These charts are based on the calculation of crack patterns in the concrete and yielding in the reinforcement as the pad is loaded by the dropping or tip-over of a dry storage cask to a point of collapse. This ultimate-strength design approach is appropriate for unlikely loading events provided that adequate margin against slab collapse is maintained. (orig./HP)

Monitoring Corrosion of Steel Bars in Reinforced Concrete Structures

Science.gov (United States)

Verma, Sanjeev Kumar; Bhadauria, Sudhir Singh; Akhtar, Saleem

2014-01-01

Corrosion of steel bars embedded in reinforced concrete (RC) structures reduces the service life and durability of structures causing early failure of structure, which costs significantly for inspection and maintenance of deteriorating structures. Hence, monitoring of reinforcement corrosion is of significant importance for preventing premature failure of structures. This paper attempts to present the importance of monitoring reinforcement corrosion and describes the different methods for evaluating the corrosion state of RC structures, especially hal-cell potential (HCP) method. This paper also presents few techniques to protect concrete from corrosion. PMID:24558346

Monitoring corrosion of steel bars in reinforced concrete structures.

Science.gov (United States)

Verma, Sanjeev Kumar; Bhadauria, Sudhir Singh; Akhtar, Saleem

2014-01-01

Corrosion of steel bars embedded in reinforced concrete (RC) structures reduces the service life and durability of structures causing early failure of structure, which costs significantly for inspection and maintenance of deteriorating structures. Hence, monitoring of reinforcement corrosion is of significant importance for preventing premature failure of structures. This paper attempts to present the importance of monitoring reinforcement corrosion and describes the different methods for evaluating the corrosion state of RC structures, especially hal-cell potential (HCP) method. This paper also presents few techniques to protect concrete from corrosion.

Monitoring Corrosion of Steel Bars in Reinforced Concrete Structures

Directory of Open Access Journals (Sweden)

Sanjeev Kumar Verma

2014-01-01

Full Text Available Corrosion of steel bars embedded in reinforced concrete (RC structures reduces the service life and durability of structures causing early failure of structure, which costs significantly for inspection and maintenance of deteriorating structures. Hence, monitoring of reinforcement corrosion is of significant importance for preventing premature failure of structures. This paper attempts to present the importance of monitoring reinforcement corrosion and describes the different methods for evaluating the corrosion state of RC structures, especially hal-cell potential (HCP method. This paper also presents few techniques to protect concrete from corrosion.

Numerical Limit Analysis of Precast Concrete Structures

DEFF Research Database (Denmark)

Herfelt, Morten Andersen

Precast concrete elements are widely used in the construction industry as they provide a number of advantages over the conventional in-situ cast concrete structures. Joints cast on the construction site are needed to connect the precast elements, which poses several challenges. Moreover, the curr...... problems are solved efficiently using state-of-the-art solvers. It is concluded that the framework and developed joint models have the potential to enable efficient design of precast concrete structures in the near future......., the current practice is to design the joints as the weakest part of the structure, which makes analysis of the ultimate limit state behaviour by general purpose software difficult and inaccurate. Manual methods of analysis based on limit analysis have been used for several decades. The methods provide...... of the ultimate limit state behaviour. This thesis introduces a framework based on finite element limit analysis, a numerical method based on the same extremum principles as the manual limit analysis. The framework allows for efficient analysis and design in a rigorous manner by use of mathematical optimisation...

New Surface-Treatment Technique of Concrete Structures Using Crack Repair Stick with Healing Ingredients.

Science.gov (United States)

Ahn, Tae-Ho; Kim, Hong-Gi; Ryou, Jae-Suk

2016-08-04

This study focused on the development of a crack repair stick as a new repair method along with self-healing materials that can be used to easily repair the cracks in a concrete structure at the construction site. In developing this new repair technique, the self-healing efficiency of various cementitious materials was considered. Likewise, a crack repair stick was developed to apply to concrete structures with 0.3 mm or lower crack widths. The crack repair stick was made with different materials, such as cement, an expansive material (C 12 A₇), a swelling material, and calcium carbonate, to endow it with a self-healing property. To verify the performance of the crack repair stick for concrete structures, two types of procedures (field experiment and field absorption test) were carried out. As a result of such procedures, it was concluded that the developed crack repair stick could be used on concrete structures to reduce repair expenses and for the improved workability, usability, and serviceability of such structures. On the other hand, to evaluate the self-healing performance of the crack repair stick, various tests were conducted, such as the relative dynamic modulus of elasticity test, the water tightness test, the water permeability test, observation via a microscope, and scanning electron microscope (SEM) analysis. From the results, it is found that water leakage can be prevented and that the durability of a concrete structure can be improved through self-healing. Also, it was verified that the cracks were perfectly closed after 28 days due to application of the crack repair stick. These results indicate the usability of the crack repair stick for concrete structures, and its self-healing efficiency.

Inelastic seismic behavior of post-installed anchors for nuclear safety related structures: Generation of experimental database

Energy Technology Data Exchange (ETDEWEB)

Mahadik, Vinay, E-mail: vinay.mahadik@iwb.uni-stuttgart.de; Sharma, Akanshu; Hofmann, Jan

2016-02-15

Highlights: • Experiments for evaluating seismic behavior of anchors were performed. • Two undercut anchor products in use in nuclear facilities were considered. • Monotonic tension, shear and cycling tension tests at different crack widths. • Crack cycling tests at constant, in-phase and out-of phase tension loads. • Characteristics for the two anchors as a function of crack width were identified. - Abstract: Post installed (PI) anchors are often employed for connections between concrete structure and components or systems in nuclear power plants (NPP) and related facilities. Standardized practices for nuclear related structures demand stringent criteria, which an anchor has to satisfy in order to qualify for use in NPP related structures. In NPP and related facilities, the structure–component interaction in the event of an earthquake depends on the inelastic behavior of the concrete structure, the component system and also the anchorage system that connects them. For analysis, anchorages are usually assumed to be rigid. Under seismic actions, however, it is known that anchors may undergo significant plastic displacement and strength degradation. Analysis of structure–component interaction under seismic loads calls for numerical models simulating inelastic behavior of anchorage systems. A testing program covering different seismic loading scenarios in a reasonably conservative manner is required to establish a basis for generating numerical models of anchorage systems. Currently there is a general lack of modeling techniques to consider the inelastic behavior of anchorages in structure–component interaction under seismic loads. In this work, in view of establishing a basis for development of numerical models simulating the inelastic behavior of anchors, seismic tests on two different undercut anchors qualified for their use in NPP related structures were carried out. The test program was primarily based on the DIBt-KKW-Leitfaden (2010) guidelines

Modelling of the Deterioration of Reinforced Concrete Structures

DEFF Research Database (Denmark)

Thoft-Christensen, Palle

Stochastic modelling of the deterioration of reinforced concrete structures is addressed in this paper on basis of a detailed modelling of corrosion initiation and corrosion cracking. It is proposed that modelling of the deterioration of concrete should be based on a sound understanding...... of the physical and chemical properties of the concrete. The relationship between rebar corrosion and crack width is investigated. A new service life definition based on evolution of the corrosion crack width is proposed....

Stress-based topology optimization of concrete structures with prestressing reinforcements

Science.gov (United States)

Luo, Yangjun; Wang, Michael Yu; Deng, Zichen

2013-11-01

Following the extended two-material density penalization scheme, a stress-based topology optimization method for the layout design of prestressed concrete structures is proposed. The Drucker-Prager yield criterion is used to predict the asymmetrical strength failure of concrete. The prestress is considered by making a reasonable assumption on the prestressing orientation in each element and adding an additional load vector to the structural equilibrium function. The proposed optimization model is thus formulated as to minimize the reinforcement material volume under Drucker-Prager yield constraints on elemental concrete local stresses. In order to give a reasonable definition of concrete local stress and prevent the stress singularity phenomenon, the local stress interpolation function and the ɛ -relaxation technique are adopted. The topology optimization problem is solved using the method of moving asymptotes combined with an active set strategy. Numerical examples are given to show the efficiency of the proposed optimization method in the layout design of prestressed concrete structures.

Offshore concrete structures; Estructuras Offshore (mar adentro) de Hormigon

Energy Technology Data Exchange (ETDEWEB)

Lamas Pardo, M.; Carral Couce, L. M.

2011-07-01

In the offshore industry there are two possible materials for the construction of the hull of a structure; the steel and concrete, with the first one widely used until now, as in the rest of the shipbuilding industry of merchant ships, warships, etc. Materials such as aluminum, GRP or timber areused in small units with lengths lower than 100 m, and in less adverse conditions than in the offshore industry. Nevertheless, some ships/barges have been built of concrete in the past, but have been rather isolated cases which have not changed the practice in the industry. In the First and Second World War were built by the scarcity of materials, while the series of barges by Alfred A. Yee was a rare exception. Other units were also made in concrete, but almost anecdotal. Still, the behaviour of these concrete structures, especially in terms of maintenance, has been excellent. Therefore, the fact that the concrete has not had an adequate reception so far in shipbuilding, does not mean that in will not be the material best suited for the offshore industry in the future. The extra displacement and associated fuel costs in concrete ships have been found prohibitive in the past. But the loss of mobility of a concrete hull in relation to a steel hull can be perfectly offset by the advantages offered by the concrete, as the shipping and offshore industry have very different priorities. One of the main differences in these priorities is in terms of maintenance and resistance to fatigue, precisely where the concrete performs better. ships can easily be dry docked for maintenance and repair, while in the offshore platforms these works have to be done in situ so maintenance and fatigue are crucial to them. Besides these, the concrete has other advantages according to findings of several studies. And although they are interested in the conclusions that the makes as they came from people in the concrete industry, the fact that in recent years concrete offshore unit shave been built

Potential applications of steel fibre reinforced concrete to improve seismic response of frame structures

International Nuclear Information System (INIS)

Adhikari, S.; Patnaik, A.

2012-01-01

Fibre reinforced concrete has gained acceptance in several civil engineering applications. The proclivity of new generation of engineers to use steel fibre reinforced concrete can be attributed to some distinct functional and structural benefits that it can provide compared to conventional reinforced concrete. Fibre reinforced concrete has been found to increase the post-cracking tensile strength of concrete thus facilitating pseudo-plastic response, improved energy absorption, and better energy dissipation capabilities that lead to better structural response under cyclic loading. These factors suggest benefits in considering the use of steel fibre reinforced concrete to enhance the structural response of reinforced concrete structures under earthquake loading. This paper summarizes useful background on steel fibre reinforced concrete, the benefits over conventional reinforced concrete, and its response to cyclic excitation. The authors believe that steel fibre reinforced concrete is a suitable ductile high performance material that is gaining acceptance for applications in frame structures and is particularly suitable for enhancing seismic response. (author)

Application of limit state design to outdoor important civil engineering reinforced concrete structures in nuclear power plant

International Nuclear Information System (INIS)

1992-01-01

As for the basic concept and the procedure of the aseismatic design of nuclear power structures, it is the present state to verify the safety by allowable stress design method, but the necessity of considering the limit state in the safety verification of these structures has been pointed out. For the purpose of clarifying the technique and procedure when limit state design method is applied to the aseismatic design of important civil engineering structures in outdoors of nuclear power stations and contributing to the rationalization of aseismatic design, aiming at completing the safety verification manual for designers, as the research on the standardization of the aseismatic design of A class civil engineering structures considering the limit state, the deliberation of the contents of research has been carried out. The outline of the manual expected to be published soon is described. The items of research, the constitution of the manual, the features of the manual, the basic concept of safety verification, the calculation of design seismic load, the method of verification for reinforced concrete structures and the verifying experiment are described. (K.I.)

UO2/magnetite concrete interaction and penetration study

International Nuclear Information System (INIS)

Farhadieh, R.; Purviance, R.; Carlson, N.

1983-01-01

The concrete structure represents a line of defense in safety assessment of containment integrity and possible minimization of radiological releases following a reactor accident. The penetration study of hot UO 2 particles into limestone concrete and basalt concrete highlighted some major differences between the two concretes. These included penetration rate, melting and dissolution phenomena, released gases, pressurization of the UO 2 chamber, and characteristics of post-test concrete. The present study focuses on the phenomena associated with core debris interaction with and penetration into magnetite type concrete. The real material experiment was carried out with UO 2 particles and magnetite concrete in a test apparatus similar to the one utilized in the UO 2 /limestone experiment

Conservation of concrete structures according to fib Model Code 2010

NARCIS (Netherlands)

Matthews, S.; Bigaj-Van Vliet, A.; Ueda, T.

2013-01-01

Conservation of concrete structures forms an essential part of the fib Model Code for Concrete Structures 2010 (fib Model Code 2010). In particular, Chapter 9 of fib Model Code 2010 addresses issues concerning conservation strategies and tactics, conservation management, condition surveys, condition

Characterization of Radiation Fields for Assessing Concrete Degradation in Biological Shields of NPPs

Science.gov (United States)

Remec, Igor; Rosseel, Thomas M.; Field, Kevin G.; Pape, Yann Le

2017-09-01

Life extensions of nuclear power plants (NPPs) to 60 years of operation and the possibility of subsequent license renewal to 80 years have renewed interest in long-term material degradation in NPPs. Large irreplaceable sections of most nuclear generating stations are constructed from concrete, including safety-related structures such as biological shields and containment buildings; therefore, concrete degradation is being considered with particular focus on radiation-induced effects. Based on the projected neutron fluence values (E > 0.1 MeV) in the concrete biological shields of the US pressurized water reactor fleet and the currently available data on radiation effects on concrete, some decrease in mechanical properties of concrete cannot be ruled out during extended operation beyond 60 years. An expansion of the irradiated concrete database is desirable to ensure reliable risk assessment for extended operation of nuclear power plants.

The Effect of Elevated Temperature on Concrete Materials and Structures - a Literature Review.

Energy Technology Data Exchange (ETDEWEB)

Naus, Dan J [ORNL

2006-03-01

The objective of this limited study was to provide an overview of the effects of elevated temperature on the behavior of concrete materials and structures. In meeting this objective the effects of elevated temperatures on the properties of ordinary Portland cement concrete constituent materials and concretes are summarized. The effects of elevated temperature on high-strength concrete materials are noted and their performance compared to normal strength concretes. A review of concrete materials for elevated-temperature service is presented. Nuclear power plant and general civil engineering design codes are described. Design considerations and analytical techniques for evaluating the response of reinforced concrete structures to elevated-temperature conditions are presented. Pertinent studies in which reinforced concrete structural elements were subjected to elevated temperatures are described.

The Effect of Elevated Temperature on Concrete Materials and Structures - a Literature Review

International Nuclear Information System (INIS)

Naus, Dan J.

2006-01-01

The objective of this limited study was to provide an overview of the effects of elevated temperature on the behavior of concrete materials and structures. In meeting this objective the effects of elevated temperatures on the properties of ordinary Portland cement concrete constituent materials and concretes are summarized. The effects of elevated temperature on high-strength concrete materials are noted and their performance compared to normal strength concretes. A review of concrete materials for elevated-temperature service is presented. Nuclear power plant and general civil engineering design codes are described. Design considerations and analytical techniques for evaluating the response of reinforced concrete structures to elevated-temperature conditions are presented. Pertinent studies in which reinforced concrete structural elements were subjected to elevated temperatures are described.

Corrosion initiation and propagation in cracked concrete - a literature review

NARCIS (Netherlands)

Pacheco, J.; Polder, R.

2012-01-01

The major degradation mechanism in civil engineering concrete structures is corrosion of reinforcement due to chloride penetration. Corrosion reduces serviceability and safety due to cracking and spalling of concrete and loss of steel cross section. Recently, service life design has moved from

Study on Seismic Behavior of Recycled Concrete Energy-efficient Homes Structure Wall

Directory of Open Access Journals (Sweden)

Dong Lan

2016-01-01

Full Text Available The main point is to study the seismic behavior of the lattice type recycled concrete energy saving wall under low-cyclic loading,to provide the basis for the seismic performance of application of recycled concrete lattice wall in energy-saving residential structure. Design two walls with the same structure measures, include Lattice type recycled concrete wall and natural concrete wall, they are tested under low-cycle repetitive loading, compared failure mode and seismic performance in different reinforcement conditions of side column. The bearing capacity and ductility of recycled aggregate concrete are better than natural aggregate concrete, The stiffness degradation curves and the skeleton curves of the walls are basically the same, both of them have better seismic energy dissipation capacity. Lattice type concrete wall is good at seismic performance, recycled aggregate concrete is good at plastic deformation ability, it is advantageous to seismic energy dissipation of wall, it can be applied in energy efficient residential structure wall.

New insights into the spatial variability of biofilm communities and potentially negative bacterial groups in hydraulic concrete structures.

Science.gov (United States)

Cai, Wei; Li, Yi; Niu, Lihua; Zhang, Wenlong; Wang, Chao; Wang, Peifang; Meng, Fangang

2017-10-15

The composition and distribution characteristics of bacterial communities in biofilms attached to hydraulic concrete structure (HCS) surfaces were investigated for the first time in four reservoirs in the middle and lower reaches of the Yangtze River Basin using 16S rRNA Miseq sequencing. High microbial diversity was found in HCS biofilms, and notable differences were observed in different types of HCS. Proteobacteria, Cyanobacteria and Chloroflexi were the predominant phyla, with respective relative abundances of 35.3%, 25.4% and 13.0%. The three most abundant genera were Leptolyngbya, Anaerolineaceae and Polynucleobacter. The phyla Beta-proteobacteria and Firmicutes and genus Lyngbya were predominant in CGP, whereas the phyla Cyanobacteria and Chloroflexi and genera Leptolyngbya, Anaerolinea and Polynucleobacter survived better in land walls and bank slopes. Dissolved oxygen, ammonia nitrogen and temperature were characterized as the main factors driving the bacterial community composition. The most abundant groups of metabolic functions were also identified as ammonia oxidizers, sulphate reducers, and dehalogenators. Additionally, functional groups related to biocorrosion were found to account for the largest proportion (14.0% of total sequences) in gate piers, followed by those in land walls (11.5%) and bank slopes (10.2%). Concrete gate piers were at the greatest risk of biocorrosion with the most abundant negative bacterial groups, especially for sulphate reducers. Thus, it should be paid high attention to the biocorrosion prevention of concrete gate piers. Overall, this study contributed to the optimization of microbial control and the improvement of the safety management for water conservation structures. Copyright © 2017 Elsevier Ltd. All rights reserved.

A corrosion monitoring system for existing reinforced concrete structures.

Science.gov (United States)

2015-05-01

This study evaluated a multi-parameter corrosion monitoring system for existing reinforced concrete structures in chloride-laden service environments. The system was fabricated based on a prototype concrete corrosion measurement system that : had bee...

Review of Carbon Fiber Reinforced Polymer Reinforced Material in Concrete Structure

Directory of Open Access Journals (Sweden)

Ayuddin Ayuddin

2016-05-01

Full Text Available Carbon Fiber Reinforced Polymer (FRP is a material that is lightweight, strong, anti-magnetic and corrosion resistant. This material can be used as an option to replace the steel material in concrete construction or as material to improve the strength of existing construction. CFRP is quite easy to be attached to the concrete structure and proved economically used as a material for repairing damaged structures and increase the resilience of structural beams, columns, bridges and other parts of the structure against earthquakes. CFRP materials can be shaped sheet to be attached to the concrete surface. Another reason is due to the use of CFRP has a higher ultimate strength and lower weight compared to steel reinforcement so that the handling is significantly easier. Through this paper suggests that CFRP materials can be applied to concrete structures, especially on concrete columns. Through the results of experiments conducted proved that the concrete columns externally wrapped with CFRP materials can increase the strength. This treatment is obtained after testing experiments on 130 mm diameter column with a height of 700 mm with concentric loading method to collapse. The experimental results indicate that a column is wrapped externally with CFRP materials can achieve a load capacity of 250 kN compared to the concrete columns externally without CFRP material which only reached 150 kN. If the column is given internally reinforcing steel and given externally CFRP materials can reach 270 kN. It shows that CFRP materials can be used for concrete structures can even replace reinforcing steel that has been widely used in building construction in Indonesia.

Doubling the Life of Concrete Structures

Energy Technology Data Exchange (ETDEWEB)

Pesic, Batric [Univ. of Idaho, Moscow, ID (United States); Raja, Krishnan [Univ. of Idaho, Moscow, ID (United States); Xi, Yumping [Univ. of Colorado, Boulder, CO (United States); Jun, Jiheon [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

2017-07-24

Overall objective of the project was to study the fundamental properties of concrete (with and without steel reinforcement) with respect to chemical and physical parameters that can influence its structural integrity.

Doubling the Life of Concrete Structures

International Nuclear Information System (INIS)

Pesic, Batric; Raja, Krishnan; Xi, Yumping; Jun, Jiheon

2017-01-01

Overall objective of the project was to study the fundamental properties of concrete (with and without steel reinforcement) with respect to chemical and physical parameters that can influence its structural integrity.

Nonlinear analysis of reinforced concrete structures using software package abaqus

Directory of Open Access Journals (Sweden)

Marković Nemanja

2014-01-01

Full Text Available Reinforced concrete (AB is characterized by huge inhomogeneity resulting from the material characteristics of the concrete, then, quasi-brittle behavior during failure. These and other phenomena require the introduction of material nonlinearity in the modeling of reinforced concrete structures. This paper presents the modeling reinforced concrete in the software package ABAQUS. A brief theoretical overview is presented of methods such as: Concrete Damage Plasticity (CDP, Smeared Concrete Cracking (CSC, Cap Plasticity (CP and Drucker-Prager model (DPM. We performed a nonlinear analysis of two-storey reinforced concrete frame by applying CDP method for modeling material nonlinearity of concrete. We have analyzed damage zones, crack propagation and loading-deflection ratio.

The Barrier code for predicting long-term concrete performance

International Nuclear Information System (INIS)

Shuman, R.; Rogers, V.C.; Shaw, R.A.

1989-01-01

There are numerous features incorporated into a LLW disposal facility that deal directly with critical safety objectives required by the NRC in 10 CFR 61. Engineered barriers or structures incorporating concrete are commonly being considered for waste disposal facilities. The Barrier computer code calculates the long-term degradation of concrete structures in LLW disposal facilities. It couples this degradation with water infiltration into the facility, nuclide leaching from the waste, contaminated water release from the facility, and associated doses to members of the critical population group. The concrete degradation methodology of Barrier is described

Axisymmetric global structural analysis of BARC prestressed concrete containment model for beyond design pressure

International Nuclear Information System (INIS)

Singh, Tarvinder; Singh, R.K.; Ghosh, A.K.

2008-10-01

In order to check the adequacy of the Indian Pressurized Heavy Water Reactor (PHWR) containment structure to withstand severe accident induced internal pressure load, the ultimate load capacity assessment is required. Reactor Safety Division (RSD) of Bhabha Atomic Research Centre (BARC) has initiated an experimental program at BARC Tarapur Containment Test Facility to evaluate the ultimate load capacity of Indian PHWR containment. For this study, BARC Containment Model (BARCOM), which is 1:4 scale representation of Tarapur Atomic Power Station (TAPS) unit-3 and 4 540 MWe PHWR Inner Containment of Pre-stressed Concrete has been constructed. The model includes all the important major design features of the prototype containment and simulates Main Air Lock (MAL), Steam Generator (SG), Emergency Air Lock (EAL) and Fueling Machine Air Lock (FMAL) openings. The design pressure (Pd) of BARCOM is 1.44kg/cm 2 (g), which is same as the prototype. The pretest analysis of BARCOM has been performed with finite element axi-symmetric modeling. The objective of this simulation was to understand the behavior of containment model under internal pressure and find out the various failure modes and critical locations important for instrumentation during the experiment. The structural response of the containment model is assessed in terms of wall and dome displacement; cracking of concrete, longitudinal and hoop strains and stresses. Another objective of the analysis was to predict the various failure modes of BARCOM with regard to the concrete cracking, reinforcement yielding and tendon inelastic behavior along with the estimation of the ultimate load capacity of the containment model. It is noted that the BARCOM has an ultimate load capacity factor of 3.54 Pd. However, further analysis is needed to quantify the factor of safety with detail 3D model, which should account for the local structural behavior due to various openings. Meanwhile, this preliminary simplified analysis helps to

PARCS - A pre-stressed and reinforced concrete shell element for analysis of containment structures

International Nuclear Information System (INIS)

Buragohain, D.N.; Mukherjee, A.

1993-01-01

Containment structures are designed as pressure vessels against a huge internal pressure build up in the event of a postulated LOCA. In such situations the containment structures experience predominantly in-plane stress in tension. Therefore, pre-stressed concrete has been very frequently used for the construction of containment. For larger plants a dual containment with a pre-stressed concrete inner containment and a reinforced concrete outer containment has been adopted. These structures are required to perform within very stringent safety requirements under extremely severe loading. Naturally, their design has attracted a lot of investigators and a huge volume of literature has been published in previous SMiRT conferences. However, it seems that the structural modeling of the containment has not developed accordingly. It is a common practice to consider the concrete section only in the model and the effects of pre-stress and reinforcements are usually neglected. This is due to the difficulty in including these effects without generating an unduly large model. To include these effects using the existing software, the concrete can be modeled with 3D elements. The reinforcements can be included in the model as bar or cable elements. However, that would require a nodal line along every reinforcement. Therefore, this method would generate a huge model unmanageable even with modern computing facilities. Alternatively, the reinforcements can be assumed to be smeared uniformly within the structure and an average property can be included. This model is acceptable when the reinforcements are very closely spaced. However, for sparsely spaced reinforcements it would result in loss of accuracy, especially in important areas like the vicinity of large openings. In this paper a shell element for the analysis of pre-stressed and reinforced concrete structures has been proposed which alleviates this difficulty. This element can accommodate the reinforcing bars or cables anywhere

Plant life management of the ACR-1000 Concrete containment structure

International Nuclear Information System (INIS)

Abrishami, H.H.; Ricciuti, R.; Elgohary, M.

2009-01-01

The Ageing of reinforced concrete structures due to service conditions, aggressive environments, or accidents may cause their strength, serviceability and durability to decrease over time. For a new plant, a Plant Life Management (PLiM) program should start in the design process and then continues through the plant operation and decommissioning. Hence, PLiM must provide not only Ageing Management program (AMP) but also provide requirements on material characteristic and design criteria as well. The purpose of this paper is to present the Plant Life Management (PLiM) strategy for the concrete containment structure of the ACR-10001 (Advanced CANDU Reactor) designed by AECL. The ACR-1000 is designed for a 100-year plant life including 60-year operating life and an additional 40-year decommissioning period. The approach adopted for the PLiM strategy of the concrete containment structure is a preventive one, key areas being: 1) design methodology, 2) material performance and 3) ageing management program. During the design phase, in addition to strength and serviceability, durability, throughout the service life and decommissioning phase of the ACR-1000 structure, is a major consideration. Factors affecting durability design include: a) concrete performance, b) structural application, and c) consideration of environmental conditions. In addition to addressing the design methodology and material performance requirements, a systematic approach for the ageing management program for the concrete containment structure is presented. (authors)

Nonparametric Change Point Diagnosis Method of Concrete Dam Crack Behavior Abnormality

Directory of Open Access Journals (Sweden)

Zhanchao Li

2013-01-01

Full Text Available The study on diagnosis method of concrete crack behavior abnormality has always been a hot spot and difficulty in the safety monitoring field of hydraulic structure. Based on the performance of concrete dam crack behavior abnormality in parametric statistical model and nonparametric statistical model, the internal relation between concrete dam crack behavior abnormality and statistical change point theory is deeply analyzed from the model structure instability of parametric statistical model and change of sequence distribution law of nonparametric statistical model. On this basis, through the reduction of change point problem, the establishment of basic nonparametric change point model, and asymptotic analysis on test method of basic change point problem, the nonparametric change point diagnosis method of concrete dam crack behavior abnormality is created in consideration of the situation that in practice concrete dam crack behavior may have more abnormality points. And the nonparametric change point diagnosis method of concrete dam crack behavior abnormality is used in the actual project, demonstrating the effectiveness and scientific reasonableness of the method established. Meanwhile, the nonparametric change point diagnosis method of concrete dam crack behavior abnormality has a complete theoretical basis and strong practicality with a broad application prospect in actual project.

Acoustic Emission Analysis of Prestressed Concrete Structures

Science.gov (United States)

Elfergani, H. A.; Pullin, R.; Holford, K. M.

2011-07-01

Corrosion is a substantial problem in numerous structures and in particular corrosion is very serious in reinforced and prestressed concrete and must, in certain applications, be given special consideration because failure may result in loss of life and high financial cost. Furthermore corrosion cannot only be considered a long term problem with many studies reporting failure of bridges and concrete pipes due to corrosion within a short period after they were constructed. The concrete pipes which transport water are examples of structures that have suffered from corrosion; for example, the pipes of The Great Man-Made River Project of Libya. Five pipe failures due to corrosion have occurred since their installation. The main reason for the damage is corrosion of prestressed wires in the pipes due to the attack of chloride ions from the surrounding soil. Detection of the corrosion in initial stages has been very important to avoid other failures and the interruption of water flow. Even though most non-destructive methods which are used in the project are able to detect wire breaks, they cannot detect the presence of corrosion. Hence in areas where no excavation has been completed, areas of serious damage can go undetected. Therefore, the major problem which faces engineers is to find the best way to detect the corrosion and prevent the pipes from deteriorating. This paper reports on the use of the Acoustic Emission (AE) technique to detect the early stages of corrosion prior to deterioration of concrete structures.

Acoustic Emission Analysis of Prestressed Concrete Structures

International Nuclear Information System (INIS)

Elfergani, H A; Pullin, R; Holford, K M

2011-01-01

Corrosion is a substantial problem in numerous structures and in particular corrosion is very serious in reinforced and prestressed concrete and must, in certain applications, be given special consideration because failure may result in loss of life and high financial cost. Furthermore corrosion cannot only be considered a long term problem with many studies reporting failure of bridges and concrete pipes due to corrosion within a short period after they were constructed. The concrete pipes which transport water are examples of structures that have suffered from corrosion; for example, the pipes of The Great Man-Made River Project of Libya. Five pipe failures due to corrosion have occurred since their installation. The main reason for the damage is corrosion of prestressed wires in the pipes due to the attack of chloride ions from the surrounding soil. Detection of the corrosion in initial stages has been very important to avoid other failures and the interruption of water flow. Even though most non-destructive methods which are used in the project are able to detect wire breaks, they cannot detect the presence of corrosion. Hence in areas where no excavation has been completed, areas of serious damage can go undetected. Therefore, the major problem which faces engineers is to find the best way to detect the corrosion and prevent the pipes from deteriorating. This paper reports on the use of the Acoustic Emission (AE) technique to detect the early stages of corrosion prior to deterioration of concrete structures.

Improvement of impact-resistance of a nuclear containment building using fiber reinforced concrete

International Nuclear Information System (INIS)

Jeon, Se-Jin; Jin, Byeong-Moo

2016-01-01

Highlights: • Impact-resistance of a structure can be improved by fiber reinforced concrete (FRC). • Material modeling of FRC is incorporated into finite element analysis of a structure. • A new index for impact-resistance is proposed based on plastic dissipation energy. • A nuclear power plant made of FRC shows improved resistance against aircraft crashes. - Abstract: Since the act of terrorism that occurred in the USA on September 11, 2001, the protection of nuclear power plants against large commercial aircraft crashes has been an emerging issue. Besides the verification of the safety of nuclear power plants in operation or in design, efficient methods for improving the impact-resistance of these structures have been investigated. Fiber reinforced concrete (FRC) has been generally accepted as an effective material for this purpose. In particular, FRC has been developed to improve the tensile behavior of concrete such as tensile strength, ductility and toughness. One of the main fields of application of FRC can be found in blast-protective or blast-resistant concrete structures. It is expected, therefore, that safety-related structures in a nuclear power plant can also be effectively protected from external blast, aircraft crash, etc. by applying FRC. In order to analytically verify the effect on structural behavior of applying FRC, the particular material properties of FRC should be incorporated into the material modeling of a structural analysis program. This study investigates the mathematical modeling of FRC, which represents various aspects of material behavior. Two numerical examples are provided to show the improved impact-resistance of a nuclear containment building that is expected when applying FRC in comparison with ordinary concrete. The analysis results show that the displacement decreases by 43–67% while the impact-resistance increases by 40–82%, depending on a fiber type.

Improvement of impact-resistance of a nuclear containment building using fiber reinforced concrete

Energy Technology Data Exchange (ETDEWEB)

Jeon, Se-Jin, E-mail: conc@ajou.ac.kr [Ajou University, 206, World cup-ro, Yeongtong-gu, Suwon-si, Gyeonggi-do 16499 (Korea, Republic of); Jin, Byeong-Moo [DAEWOO E& C, Institute of Construction Technology, 20, Suil-ro 123beon-gil, Jangan-gu, Suwon-si, Gyeonggi-do 16297 (Korea, Republic of)

2016-08-01

Highlights: • Impact-resistance of a structure can be improved by fiber reinforced concrete (FRC). • Material modeling of FRC is incorporated into finite element analysis of a structure. • A new index for impact-resistance is proposed based on plastic dissipation energy. • A nuclear power plant made of FRC shows improved resistance against aircraft crashes. - Abstract: Since the act of terrorism that occurred in the USA on September 11, 2001, the protection of nuclear power plants against large commercial aircraft crashes has been an emerging issue. Besides the verification of the safety of nuclear power plants in operation or in design, efficient methods for improving the impact-resistance of these structures have been investigated. Fiber reinforced concrete (FRC) has been generally accepted as an effective material for this purpose. In particular, FRC has been developed to improve the tensile behavior of concrete such as tensile strength, ductility and toughness. One of the main fields of application of FRC can be found in blast-protective or blast-resistant concrete structures. It is expected, therefore, that safety-related structures in a nuclear power plant can also be effectively protected from external blast, aircraft crash, etc. by applying FRC. In order to analytically verify the effect on structural behavior of applying FRC, the particular material properties of FRC should be incorporated into the material modeling of a structural analysis program. This study investigates the mathematical modeling of FRC, which represents various aspects of material behavior. Two numerical examples are provided to show the improved impact-resistance of a nuclear containment building that is expected when applying FRC in comparison with ordinary concrete. The analysis results show that the displacement decreases by 43–67% while the impact-resistance increases by 40–82%, depending on a fiber type.

An overview of the Structural Aging Program

International Nuclear Information System (INIS)

Naus, D.J.; Arndt, E.G.

1992-01-01

The structural Aging Program is conducted at the Oak Ridge National Laboratory (ORNL) for the Nuclear Regulatory Commission (NRC). The program has the overall objective of preparing an expandable handbook or report which will provide NRC with potential structural safety issues and acceptance criteria for use in nuclear power plant evaluations for continued service. Initial focus of the program is on concrete and concrete-related materials which comprise safety-related (Category I) structures in light-water reactor facilities. The program is organized into four tasks: Task S.1 -- Program Management, Task S.2 -- Materials Property Data Base, Task S.3 -- Structural Component Assessment/Repair Technology, and Task S.4 -- Quantitative Methodology for Continued Service Determinations. Objectives, background information, and accomplishments under each of these tasks are presented

Fibre Concrete 2017

Science.gov (United States)

2017-09-01

9th international conference on fibre reinforced concretes (FRC), textile reinforced concretes (TRC) and ultra-high performance concretes (UHPC) Preface The Fibre Concrete Conference series is held biennially to provide a platform to share knowledge on fibre reinforced concretes, textile concretes and ultra-high performance concretes regarding material properties and behaviour, technology procedures, topics of long-term behaviour, creep, durability; sustainable aspects of concrete including utilisation of waste materials in concrete production and recycling of concrete. The tradition of Fibre Concrete Conferences started in eighties of the last century. Nowadays the conference is organized by the Department of Concrete and Masonry Structures of the Czech Technical University in Prague, Faculty of Civil Engineering. The 9th International Conference Fibre Concrete 2017 had 109 participants from 27 countries all over the world. 55 papers were presented including keynote lectures of Professor Bažant, Professor Bartoš and Dr. Broukalová. The conference program covered wide range of topics from scientific research to practical applications. The presented contributions related to performance and behaviour of cement based composites, their long-term behaviour and durability, sustainable aspects, advanced analyses of structures from these composites and successful applications. This conference was organized also to honour Professor Zděnek P. Bažant on the occasion of his jubilee and to appreciate his merits and discoveries in the field of fibre reinforced composites, structural mechanics and engineering.

Strategy for 100-year life of the ACR-1000 concrete containment structure

International Nuclear Information System (INIS)

Abrishami, H.; Elgohary, M.

2006-01-01

The purpose of this paper is to present the Plant Life Management (PLiM) strategy for the concrete containment structure of the ACR-1000 (Advanced CANDU Reactor) designed by AECL. The ACR-1000 is designed for 100-year plant life including 60-year operating life and additional 40-year decommissioning period of time. The approach adopted for the PLiM strategy of the concrete containment structure is a preventive one, key areas being: 1) design methodology, 2) material performance and 3) life cycle management and ageing management program. In the design phase, in addition to strength and serviceability, durability is a major requirement during the service life and decommissioning phase of the ACR structure. Parameters affecting durability design include: a) concrete performance, b) structural application, and c) environmental conditions. Due to the complex nature of the environmental effects acting on structures during the service life of project, it is considered that true improved performance during the service life can be achieved by improving the material characteristics. Many recent innovations in advanced concrete materials technology have made it possible to produce modern concrete such as high-performance concrete with exceptional performance characteristics. In this paper, the PLiM strategy for the ACR-1000 concrete containment is presented. In addition to addressing the design methodology and material performance areas, a systematic approach for ageing management program for the concrete containment structure is presented. (author)

DYNAPCON: a computer code for dynamic analysis of prestressed concrete structures

International Nuclear Information System (INIS)

Marchertas, A.H.

1982-09-01

A finite element computer code for the transient analysis of prestressed concrete reactor vessels (PCRVs) for LMFBR containment is described. The method assumes rotational symmetry of the structure. Time integration is by an explicit method. The quasistatic prestressing operation of the PCRV model is performed by a dynamic relaxation technique. The material model accounts for the crushing and tensile cracking in arbitrary direction in concrete and the elastic-plastic behavior of reinforcing steel. The variation of the concrete tensile cracking and compressive crushing limits with strain rate is taken into account. Relative slip is permitted between the concrete and tendons. Several example solutions are presented and compared with experimental results. These sample problems range from simply supported beams to small scale models of PCRV's. It is shown that the analytical methods correlate quite well with experimental results, although in the vicinity of the failure load the response of the models tend to be quite sensitive to input parameters

Modelling Dowel Action of Discrete Reinforcing Bars in Cracked Concrete Structures

International Nuclear Information System (INIS)

Kwan, A. K. H.; Ng, P. L.; Lam, J. Y. K.

2010-01-01

Dowel action is one of the component actions for shear force transfer in cracked reinforced concrete. In finite element analysis of concrete structures, the use of discrete representation of reinforcing bars is considered advantageous over the smeared representation due to the relative ease of modelling the bond-slip behaviour. However, there is very limited research on how to simulate the dowel action of discrete reinforcing bars. Herein, a numerical model for dowel action of discrete reinforcing bars crossing cracks in concrete is developed. The model features the derivation of dowel stiffness matrix based on beam-on-elastic-foundation theory and the direct assemblage of dowel stiffness into the concrete element stiffness matrices. The dowel action model is incorporated in a nonlinear finite element programme with secant stiffness formulation. Deep beams tested in the literature are analysed and it is found that the incorporation of dowel action model improves the accuracy of analysis.

Analysis of the status of pre-release cracks in prestressed concrete structures using long-gauge sensors

International Nuclear Information System (INIS)

Abdel-Jaber, H; Glisic, B

2015-01-01

Prestressed structures experience limited tensile stresses in concrete, which limits or completely eliminates the occurrence of cracks. However, in some cases, large tensile stresses can develop during the early age of the concrete due to thermal gradients and shrinkage effects. Such stresses can cause early-age cracks, termed ‘pre-release cracks’, which occur prior to the transfer of the prestressing force. When the prestressing force is applied to the cross-section, it is assumed that partial or full closure of the cracks occurs by virtue of the force transfer through the cracked cross-section. Verification of the closure of the cracks after the application of the prestressing force is important as it can either confirm continued structural integrity or indicate and approximate reduced structural capacity. Structural health monitoring (SHM) can be used for this purpose. This paper researches an SHM method that can be applied to prestressed beam structures to assess the condition of pre-release cracks. The sensor network used in this method consists of parallel long-gauge fiber optic strain sensors embedded in the concrete cross-sections at various locations. The same network is used for damage detection, i.e. detection and characterization of the pre-release cracks, and for monitoring the prestress force transfer. The method is validated on a real structure, a curved continuous girder. Results from the analysis confirm the safety and integrity of the structure. The method and its application are presented in this paper. (paper)

Analysis of the status of pre-release cracks in prestressed concrete structures using long-gauge sensors

Science.gov (United States)

Abdel-Jaber, H.; Glisic, B.

2015-02-01

Prestressed structures experience limited tensile stresses in concrete, which limits or completely eliminates the occurrence of cracks. However, in some cases, large tensile stresses can develop during the early age of the concrete due to thermal gradients and shrinkage effects. Such stresses can cause early-age cracks, termed ‘pre-release cracks’, which occur prior to the transfer of the prestressing force. When the prestressing force is applied to the cross-section, it is assumed that partial or full closure of the cracks occurs by virtue of the force transfer through the cracked cross-section. Verification of the closure of the cracks after the application of the prestressing force is important as it can either confirm continued structural integrity or indicate and approximate reduced structural capacity. Structural health monitoring (SHM) can be used for this purpose. This paper researches an SHM method that can be applied to prestressed beam structures to assess the condition of pre-release cracks. The sensor network used in this method consists of parallel long-gauge fiber optic strain sensors embedded in the concrete cross-sections at various locations. The same network is used for damage detection, i.e. detection and characterization of the pre-release cracks, and for monitoring the prestress force transfer. The method is validated on a real structure, a curved continuous girder. Results from the analysis confirm the safety and integrity of the structure. The method and its application are presented in this paper.

Modeling of fracture of protective concrete structures under impact loads

Energy Technology Data Exchange (ETDEWEB)

Radchenko, P. A., E-mail: radchenko@live.ru; Batuev, S. P.; Radchenko, A. V.; Plevkov, V. S. [Tomsk State University of Architecture and Building, Tomsk, 634003 (Russian Federation)

2015-10-27

This paper presents results of numerical simulation of interaction between a Boeing 747-400 aircraft and the protective shell of a nuclear power plant. The shell is presented as a complex multilayered cellular structure consisting of layers of concrete and fiber concrete bonded with steel trusses. Numerical simulation was performed three-dimensionally using the original algorithm and software taking into account algorithms for building grids of complex geometric objects and parallel computations. Dynamics of the stress-strain state and fracture of the structure were studied. Destruction is described using a two-stage model that allows taking into account anisotropy of elastic and strength properties of concrete and fiber concrete. It is shown that wave processes initiate destruction of the cellular shell structure; cells start to destruct in an unloading wave originating after the compression wave arrival at free cell surfaces.

Modeling of fracture of protective concrete structures under impact loads

Science.gov (United States)

Radchenko, P. A.; Batuev, S. P.; Radchenko, A. V.; Plevkov, V. S.

2015-10-01

This paper presents results of numerical simulation of interaction between a Boeing 747-400 aircraft and the protective shell of a nuclear power plant. The shell is presented as a complex multilayered cellular structure consisting of layers of concrete and fiber concrete bonded with steel trusses. Numerical simulation was performed three-dimensionally using the original algorithm and software taking into account algorithms for building grids of complex geometric objects and parallel computations. Dynamics of the stress-strain state and fracture of the structure were studied. Destruction is described using a two-stage model that allows taking into account anisotropy of elastic and strength properties of concrete and fiber concrete. It is shown that wave processes initiate destruction of the cellular shell structure; cells start to destruct in an unloading wave originating after the compression wave arrival at free cell surfaces.

Leakage of pressurized gases through unlined concrete containment structures

International Nuclear Information System (INIS)

Rizkalla, S.H.; Simmonds, S.H.

1983-01-01

Eight reinforced concrete specimens were fabricated and subjected to tensile membrane forces and air pressure to study the air leakage characteristics in cracked reinforced concrete members. A mathematical expression for the rate of pressurized air flowing through an idealized crack is presented. The mathematical expression is refined by using the experimental data to describe the air flow rate through any given crack pattern. Graphical charts are also presented for the calculation of the air leakage rate through concrete cracks. The concept of equivalent crack width for a given crack pattern is introduced. The mathematical expression and graphical charts are modified to include this equivalent crack width concept. The proposed technique is applicable for the prediction of the leakage from concrete containment structures or any similar structures due to high internal pressure sufficient to initiate cracking. (orig.)

Quality control of fireproof coatings for reinforced concrete structures

Science.gov (United States)

Gravit, Marina; Dmitriev, Ivan; Ishkov, Alexander

2017-10-01

The article analyzes methods of quality inspection of fireproof coatings (work flow, measuring, laboratory, etc.). In modern construction there is a problem of lack of distinct monitoring for the fire protection testing. There is a description of this testing for reinforced concrete structures. The article shows the results of calculation quality control of hatches as an example of fireproof coating for reinforced concrete structures.

Three dimensional finite element linear analysis of reinforced concrete structures

International Nuclear Information System (INIS)

Inbasakaran, M.; Pandarinathan, V.G.; Krishnamoorthy, C.S.

1979-01-01

A twenty noded isoparametric reinforced concrete solid element for the three dimensional linear elastic stress analysis of reinforced concrete structures is presented. The reinforcement is directly included as an integral part of the element thus facilitating discretization of the structure independent of the orientation of reinforcement. Concrete stiffness is evaluated by taking 3 x 3 x 3 Gauss integration rule and steel stiffness is evaluated numerically by considering three Gaussian points along the length of reinforcement. The numerical integration for steel stiffness necessiates the conversion of global coordiantes of the Gaussian points to nondimensional local coordinates and this is done by Newton Raphson iterative method. Subroutines for the above formulation have been developed and added to SAP and STAP routines for solving the examples. The validity of the reinforced concrete element is verified by comparison of results from finite element analysis and analytical results. It is concluded that this finite element model provides a valuable analytical tool for the three dimensional elastic stress analysis of concrete structures like beams curved in plan and nuclear containment vessels. (orig.)

Detecting alkali-silica reaction in thick concrete structures using linear array ultrasound

Science.gov (United States)

Bull Ezell, N. Dianne; Albright, Austin; Clayton, Dwight; Santos-Villalobos, Hector

2018-03-01

Commercial nuclear power plants (NPPs) depend heavily on concrete structures, making the long-term performance of these structures crucial for safe operation, especially with license period extensions to 60 years and possibly beyond. Alkali-silica reaction (ASR) is a reaction that occurs over time in concrete between alkaline cement paste and reactive, noncrystalline silica (aggregates). In the presence of water, an expansive gel is formed within the aggregates, which results in microcracks in aggregates and adjacent cement paste. ASR can potentially affect concrete properties and performance characteristics such as compressive strength, modulus of elasticity, flexural stiffness, shear strength, and tensile strength. Currently, no nondestructive evaluation methods have proven effective in identifying ASR before surface cracks form. ASR is identified visibly or by petrographic analysis. Although ASR definitely impacts concrete material properties, the performance of concrete structures exhibiting ASR depends on whether or not the concrete is unconfined or confined with reinforcing bars. Confinement by reinforcing bars restrainsthe expansion of ASR-affected concrete, similar to prestressing, thus improving the performance of a structure. Additionally, there is no direct correlation between the mechanical properties of concrete sample cores and the in-situ properties of the concrete. The University of Tennessee-Knoxville, Oak Ridge National Laboratory, and a consortium of universities have developed an accelerated ASR experiment. Three large concrete specimens, representative of NPP infrastructure, were constructed containing both embedded and surface instruments. This paper presents preliminary analysis of these specimens using a frequency-banded synthetic aperture focusing technique.

Covercrete with hybrid functions - A novel approach to durable reinforced concrete structures

Energy Technology Data Exchange (ETDEWEB)

Tang, L.; Zhang, E.Q. [Chalmers University of Technology, SE-412 96 Gothenburg (Sweden); Fu, Y. [KTH Royal Institute of Technology, SE-106 91 Stockholm (Sweden); Schouenborg, B.; Lindqvist, J.E. [CBI Swedish Cement and Concrete Research Institute, c/o SP, Box 857, SE-501 15 Boraas (Sweden)

2012-12-15

Due to the corrosion of steel in reinforced concrete structures, the concrete with low water-cement ratio (w/c), high cement content, and large cover thickness is conventionally used for prolonging the passivation period of steel. Obviously, this conventional approach to durable concrete structures is at the sacrifice of more CO{sub 2} emission and natural resources through consuming higher amount of cement and more constituent materials, which is against sustainability. By placing an economically affordable conductive mesh made of carbon fiber or conductive polymer fiber in the near surface zone of concrete acting as anode we can build up a cathodic prevention system with intermittent low current density supplied by, e.g., the solar cells. In such a way, the aggressive negative ions such as Cl{sup -}, CO{sub 3}{sup 2-}, and SO{sub 4}{sup 2-} can be stopped near the cathodic (steel) zone. Thus the reinforcement steel is prevented from corrosion even in the concrete with relatively high w/c and small cover thickness. This conductive mesh functions not only as electrode, but also as surface reinforcement to prevent concrete surface from cracking. Therefore, this new type of covercrete has hybrid functions. This paper presents the theoretical analysis of feasibility of this approach and discusses the potential durability problems and possible solutions to the potential problems. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

Structural analysis of reinforced concrete structures under monotonous and cyclic loadings: numerical aspects

International Nuclear Information System (INIS)

Lepretre, C.; Millard, A.; Nahas, G.

1989-01-01

The structural analysis of reinforced concrete structures is usually performed either by means of simplified methods of strength of materials type i.e. global methods, or by means of detailed methods of continuum mechanics type, i.e. local methods. For this second type, some constitutive models are available for concrete and rebars in a certain number of finite element systems. These models are often validated on simple homogeneous tests. Therefore, it is important to appraise the validity of the results when applying them to the analysis of a reinforced concrete structure, in order to be able to make correct predictions of the actual behaviour, under normal and faulty conditions. For this purpose, some tests have been performed at I.N.S.A. de Lyon on reinforced concrete beams, subjected to monotonous and cyclic loadings, in order to generate reference solutions to be compared with the numerical predictions given by two finite element systems: - CASTEM, developed by C.E.A./.D.E.M.T. - ELEFINI, developed by I.N.S.A. de Lyon

Finite element analysis of prestressed concrete reactor vessels

International Nuclear Information System (INIS)

Smith, P.D.; Cook, W.A.; Anderson, C.A.

1977-01-01

Several present and proposed gas-cooled reactors use concrete pressure vessels. In addition, concrete is almost universally used for the secondary containment structures of water-cooled reactors. Regulatory agencies must have means of assuring that these concrete structures perform their containment functions during normal operation and after extreme conditions of transient overpressure and high temperature. The NONSAP nonlinear structural analysis program has been extensively modified to provide one analytical means of assessing the safety of reinforced concrete pressure vessels and containments. Several structural analysis codes were studied to evaluate their ability to model the nonlinear static and dynamic behavior of three-dimensional structures. The NONSAP code was selected because of its availability and because of the ease with which it can be modified. In particular, the modular structure of this code allows ready addition of specialized material models. Major modifications have been the development of pre- and post-processors for mesh generation and graphics, the addition of an out-of-core solver, and the addition of constitutive models for reinforced concrete subject to either long-term or short-term loads. Emphasis was placed on development of a three-dimensional analysis capability

Relating Fresh Concrete Viscosity Measurements from Different Rheometers.

Science.gov (United States)

Ferraris, Chiara F; Martys, Nicos S

2003-01-01

Concrete rheological properties need to be properly measured and predicted in order to characterize the workability of fresh concrete, including special concretes such as self-consolidating concrete (SCC). It was shown by a round-robin test held in 2000 [1,2] that different rheometer designs gave different values of viscosity for the same concrete. While empirical correlation between different rheometers was possible, for a procedure that is supposed to "scientifically" improve on the empirical slump tests, this situation is unsatisfactory. To remedy this situation, a new interpretation of the data was developed. In this paper, it is shown that all instruments tested could be directly and quantitatively compared in terms of relative plastic viscosity instead of the plastic viscosity alone. This should eventually allow the measurements from various rheometer designs to be directly calibrated against known standards of plastic viscosity, putting concrete rheometry and concrete workability on a sounder materials science basis.

Recovery and residual stress of SMA wires and applications for concrete structures

International Nuclear Information System (INIS)

Choi, Eunsoo; Cho, Sung-Chul; Park, Taehyo; Hu, Jong Wan; Chung, Young-Soo

2010-01-01

In general, NiTi shape memory alloys are used for applications in civil structures. NiTi SMAs show good superelasticity and shape memory effect properties. However, for application of the shape memory effect, it is desirable for SMAs to show a wide temperature hysteresis, especially for civil structures which are exposed to severe environmental conditions. NiTiNb SMAs, in general, show a wider temperature hysteresis than NiTi SMAs and are more applicable for civil structures. This study examines the temperature hysteresis of NiTiNb and NiTi SMAs, and their recovery and residual stress are investigated. In addition, the tensile behaviors of SMA wires under residual stress are evaluated. This study explains the possible applications for concrete structures with the shape memory effect and illustrates two experimental results of concrete cylinders and reinforced concrete columns. For both tests, SMA wires of NiTiNb and NiTi are used to confine concrete using residual stress. The SMA wire jackets on the concrete cylinders increase the peak strength and the ductility compared to the plain concrete cylinders. In addition, the SMA wire jackets on reinforced concrete columns increase the ductility greatly without flexural strength degradation

Safety design guide for safety related systems for CANDU 9

International Nuclear Information System (INIS)

Lee, Duk Su; Chang, Woo Hyun; Lee, Nam Young; A. C. D. Wright

1996-03-01

In general, two types of safety related systems and structures exist in the nuclear plant; The one is a systems and structures which perform safety functions during the normal operation of the plant, and the other is a systems and structures which perform safety functions to mitigate events caused by failure of the normally operating systems or by naturally occurring phenomena. In this safety design guide, these systems are identified in detail, and the major events for which the safety functions are required and the major safety requirements are identified in the list. As the probabilistic safety assessments are completed during the course of the project, additions or deletions to the list may be justified. 3 tabs. (Author) .new

Safety design guide for safety related systems for CANDU 9

Energy Technology Data Exchange (ETDEWEB)

Lee, Duk Su; Chang, Woo Hyun; Lee, Nam Young [Korea Atomic Energy Research Institute, Daeduk (Korea, Republic of); Wright, A.C.D. [Atomic Energy of Canada Ltd., Toronto (Canada)

1996-03-01

In general, two types of safety related systems and structures exist in the nuclear plant; The one is a systems and structures which perform safety functions during the normal operation of the plant, and the other is a systems and structures which perform safety functions to mitigate events caused by failure of the normally operating systems or by naturally occurring phenomena. In this safety design guide, these systems are identified in detail, and the major events for which the safety functions are required and the major safety requirements are identified in the list. As the probabilistic safety assessments are completed during the course of the project, additions or deletions to the list may be justified. 3 tabs. (Author) .new.

Structural Behaviors of Reinforced Concrete Piers Rehabilitated with FRP Wraps

Directory of Open Access Journals (Sweden)

Junsuk Kang

2017-01-01

Full Text Available The use of fiber-reinforced polymer (FRP wraps to retrofit and strengthen existing structures such as reinforced concrete piers is becoming popular due to the higher tensile strength, durability, and flexibility gained and the method’s ease of handling and low installation and maintenance costs. As yet, however, few guidelines have been developed for determining the optimum thicknesses of the FRP wraps applied to external surfaces of concrete or masonry structures. In this study, nonlinear pushover finite element analyses were utilized to analyze the complex structural behaviors of FRP-wrapped reinforced rectangular piers. Design parameters such as pier section sizes, pier heights, pier cap lengths, compressive strengths of concrete, and the thicknesses of the FRP wraps used were thoroughly tested under incremental lateral and vertical loads. The results provide useful guidelines for analyzing and designing appropriate FRP wraps for existing concrete piers.

Measurements of resonance frequencies on prestressed concrete beams during post-tensioning

International Nuclear Information System (INIS)

Lundqvist, P.; Ryden, N.

2011-01-01

The reactor containment, which is a concrete structure prestressed vertically and horizontally, is the most essential safety barrier in a nuclear power plant and is designed to withstand a severe internal accident. The safety of the containment depends on the induced compressive stresses in the concrete, however due to various long-term mechanisms the tendon forces will decrease with time. Today, no methods exist for measuring these prestress losses in containments with bonded tendons and thus there is a need for non-destructive methods for estimating the losses in these structures. Recent results from non-linear ultrasonic measurements during uniaxial loading have demonstrated a strong acoustic and elastic effect in concrete. The present research applies resonant acoustic spectroscopy (RAS) during static loading and unloading of three prestressed concrete beams. At each load step multiple modes of vibration are measured using an accelerometer and a small impact source. Measured resonant frequencies increase with increasing compressive stress. The stress dependency of the modulus of elasticity indicates that the change in state of stress in a simple concrete structure can be estimated by simply measuring the resonance frequency

Ultimate load capacity assessment of reinforced concrete shell structures

International Nuclear Information System (INIS)

Gupta, Amita; Singh, R.K.; Kushwaha, H.S.; Mahajan, S.C.; Kakodkar, A.

1993-01-01

The objective of this study is to develop capability for prediction of ultimate load capacity of reinforced concrete shell structures. The present finite element code ULCA (Ultimate Load Capacity Assessment) adopts a degenerate concept of formulating general isoparametric shell element with a layered approach in the thickness direction. Different failure modes such as crushing, tensile cracking and reinforcement yielding are recognised for various problems. The structure fails by crushing of concrete when the concrete strain/stress reaches the ultimate stress or strain of concrete. Material nonlinearities as a result of tension cracking, tension stiffening between reinforcement and concrete in cracked region and yielding of reinforcement are considered along with geometric nonlinearity. Thus with this code it is possible to predict the pressure at which the first cracking, first through thickness cracking, first yielding of reinforcement occurs. After validating the code with few bench mark problems for different failure modes a reinforced concrete nuclear containment is analysed for its ultimate capacity and the results are matched with the published results. Further the ultimate load capacity of outer containment wall of Narora Atomic Power Station is predicted. It is observed that containment fails in membrane region and has a sufficient margin against design pressure. (author). 9 refs., 56 figs., 3 tabs., 1 appendix with 4 tabs

Scope and selection of structures subject to aging management review

International Nuclear Information System (INIS)

Mendoza, G.; Diaz, A.; Viais, J.; Carmona, M.; Santander, L.

2014-10-01

The purpose of this work is to determine the structures included within the scope of license renewal based on the performance of the functions and select those intended for aging management review; one purpose is to show the methodology used to establish the structure and structural components that are subject to a review of aging management, within the framework of license renewal rule. This is through the application of different types of structures and structural components related and unrelated to safety located in the rooms of the reactor building where there are components of the reactor core isolation cooling system (Rcic), these structures are poured concrete, concrete block, structural steel, shielding walls, attached metal, pile foundations, etc.; other non- security related , such as: 1) inherent characteristics not related to security that protect the equipment related to the safety of the missiles, that is, walls, low walls, dikes, doors, etc., which also provide flood barriers to structures, systems and components related to safety, 2 ) whipping restrictions on non- security, shields mitigation jet, vent panels , etc. that are designed and installed to protect equipment related with the safety of the effects of a broken line of high energy. Only rooms where there are components of the Rcic 68 structures within the scope were identified. (Author)

Bond slip model for the simulation of reinforced concrete structures

International Nuclear Information System (INIS)

Casanova, A.; Jason, L.; Davenne, L.

2012-01-01

This paper presents a new finite element approach to model the steel-concrete bond effects. This model proposes to relate steel, represented by truss elements, with the surrounding concrete in the case where the two meshes are not necessary coincident. The theoretical formulation is described and the model is applied on a reinforced concrete tie. A characteristic stress distribution is observed, related to the transfer of bond forces from steel to concrete. The results of this simulation are compared with a computation in which a perfect relation between steel and concrete is supposed. It clearly shows how the introduction of the bond model can improve the description of the cracking process (finite number of cracks). (authors)

Evaluation of the environmental, material, and structural performance of recycled aggregate concrete

Science.gov (United States)

Michaud, Katherine Sarah

Concrete is the most commonly used building material in the construction industry, and contributes to 52% of construction and demolition waste in Canada. Recycled concrete aggregate (RCA) is one way to reduce this impact. To evaluate the performance of coarse and granular (fine and coarse) RCA in structural concrete applications, four studies were performed: an environmental assessment, a material testing program, a shear performance study, and a flexural performance study. To determine the environmental benefits of recycled aggregate concrete (RAC), three case studies were investigated using different populations and proximities to city centres. Environmental modelling suggested that RCA replacement could result in energy savings and greenhouse gas emission reductions, especially in remote areas. Tests were performed to determine if the volumetric replacement of up to 30% coarse RCA and 20% granular RCA is suitable for structural concrete applications in Canada. Fresh, hardened, and durability properties were evaluated. All five (5) of the RCA mixes showed equivalent material performance to the control mixes and met the requirements for a structural concrete mix. The five (5) RAC mixes were also used in structural testing. One-way reinforced concrete slab specimens were tested to failure to evaluate the shear and flexural performance of the RAC members. Peak capacities of and crack formation within each member were analyzed to evaluate the performance of RAC compared to conventional concrete. The shear capacity of specimens made from four (4) of the five (5) RAC mixtures was higher or equivalent to the control specimens. Specimens of the concrete mixture containing the highest content of recycled aggregate, 20% volumetric replacement of granular RCA, had shear capacities 14.1% lower, and exhibited cracking at lower loads than the control. The average flexural capacities of all RAC specimens were within 3.7% of the control specimens. Results from this research

Cathodic protection of reinforced concrete structures in the Netherlands - Experience and developments: Cathodic protection of concrete - 10 years experience

NARCIS (Netherlands)

Polder, R.B.

1998-01-01

Cathodic protection (CP) of reinforcing steel in concrete structures has been used successfully for over 20 years. CP is able to stop corrosion in a reliable and economical way where chloride contamination has caused reinforcement corrosion and subsequent concrete damage. To new structures where

Aging management of containment structures in nuclear power plants

International Nuclear Information System (INIS)

Naus, D.J.; Oland, C.B.; Ellingwood, B.R.; Graves, H.L. III; Norris, W.E.

1996-01-01

Research is being conducted by Oak Ridge National Laboratory under US nuclear regulatory commission (USNRC) sponsorship to address aging management of nuclear power plant containment and other safety-related structures. Documentation is being prepared to provide the USNRC with potential structural safety issues and acceptance criteria for use in continued service evaluations of nuclear power plants. Accomplishments include development of a structural materials information center containing data and information on the time variation of 144 material properties under the influence of pertinent environmental stressors or aging factors, evaluation of models for potential concrete containment degradation factors, development of a procedure to identify critical structures and degradation factors important to aging management, evaluations of non-destructive evaluation techniques, assessments of European and North American repair practices for concrete, review of parameters affecting corrosion of metals embedded in concrete, and development of methodologies for making current condition assessments and service life predictions of new or existing reinforced concrete structures in nuclear power plants. (orig.)

Aging management of containment structures in nuclear power plants

International Nuclear Information System (INIS)

Naus, D.J.; Oland, C.B.; Ellingwood, B.R.

1994-01-01

Research is being conducted by Oak Ridge National Laboratory under U.S. Nuclear Regulatory Commission sponsorship to address aging management of nuclear power plant containment and other safety-related structures. Documentation is being prepared to provide the US-NRC with potential structural safety issues and acceptance criteria for use in continued service evaluations of nuclear power plants. Accomplishments include development of a Structural Materials Information Center containing data and information on the time variation of 144 material properties under the influence of pertinent environmental stressors or aging factors, evaluation of models for potential concrete containment degradation factors, development of a procedure to identify critical structures and degradation factors important to aging management, evaluations of nondestructive evaluation techniques, assessments of European and North American repair practices for concrete, review of parameters affecting corrosion of metals embedded in concrete, and development of methodologies for making current condition assessments and service life predictions of new or existing reinforced concrete structures in nuclear power plants. (author). 29 refs., 2 figs

Aging management of containment structures in nuclear power plants

International Nuclear Information System (INIS)

Naus, D.J.; Oland, C.B.; Ellingwood, B.R.; Graves, H.L. III; Norris, W.E.

1994-01-01

Research is being conducted by ORNL under US Nuclear Regulatory Commission (USNRC) sponsorship to address aging management of nuclear power plant containment and other safety-related structures. Documentation is being prepared to provide the USNRC with potential structural safety issues and acceptance criteria for use in continued service evaluations of nuclear power plants. Accomplishments include development of a Structural Materials Information Center containing data and information on the time variation of 144 material properties under the influence of pertinent environmental stressors or aging factors, evaluation of models for potential concrete containment degradation factors, development of a procedure to identify critical structures and degradation factors important to aging management, evaluations of nondestructive evaluation techniques. assessments of European and North American repair practices for concrete, review of parameters affecting corrosion of metals embedded in concrete, and development of methodologies for making current condition assessments and service life predictions of new or existing reinforced concrete structures in nuclear power plants

Computational experiences with variable modulus, elastic-plastic, and viscoelastic concrete models

International Nuclear Information System (INIS)

Anderson, C.A.

1981-01-01

Six years ago the Reactor Safety Research Division of the Nuclear Regulatory Commission (NRC) approached the Los Alamos National Laboratory to develop a comprehensive concrete structural analysis code to predict the static and dynamic behavior of Prestressed Concrete Reactor Vessels (PCRVs) that serve as the containment structure of a High-Temperature Gas-Cooled Reactor. The PCRV is a complex concrete structure that must be modeled in three dimensions and posseses other complicating features such as a steel liner for the reactor cavity and woven cables embedded vertically in the PCRV and wound circumferentially on the outside of the PCRV. The cables, or tendons, are used for prestressing the reactor vessel. In addition to developing the computational capability to predict inelastic three dimensional concrete structural behavior, the code response was verified against documented experiments on concrete structural behavior. This code development/verification effort is described

Analysis of seismic effects on reinforced concrete structures

International Nuclear Information System (INIS)

Tai, A.A.

1981-12-01

An important bibliographical research was undertaken in order to make the best possible analysis of the dynamic behaviour of materials and of structural components. This research work was completed by the study of the structures tested on a seismic table. The results obtained from this preliminary study, particularly those concerning the modification in the rigidity of reinforced concrete structures under alternate and seismic loading, enabled a calculation method (called ''equivalent static'') to be drawn up for analyzing the behaviour of reinforced concrete structures in earthquakes. This method takes into account the non-linearity of the behaviour of materials, in particular. The earthquake responses that were obtained by this method on gantries tested on a vibrating table, tally very satisfactorily with the test figures [fr

Compressive behavior of pervious concretes and a quantification of the influence of random pore structure features

International Nuclear Information System (INIS)

Deo, Omkar; Neithalath, Narayanan

2010-01-01

Research highlights: → Identified the relevant pore structure features of pervious concretes, provided methodologies to extract those, and quantified the influence of these features on compressive response. → A model for stress-strain relationship of pervious concretes, and relationship between model parameters and parameters of the stress-strain relationship developed. → Statistical model for compressive strength as a function of pore structure features; and a stochastic model for the sensitivity of pore structure features in strength prediction. - Abstract: Properties of a random porous material such as pervious concrete are strongly dependent on its pore structure features, porosity being an important one among them. This study deals with developing an understanding of the material structure-compressive response relationships in pervious concretes. Several pervious concrete mixtures with different pore structure features are proportioned and subjected to static compression tests. The pore structure features such as pore area fractions, pore sizes, mean free spacing of the pores, specific surface area, and the three-dimensional pore distribution density are extracted using image analysis methods. The compressive stress-strain response of pervious concretes, a model to predict the stress-strain response, and its relationship to several of the pore structure features are outlined. Larger aggregate sizes and increase in paste volume fractions are observed to result in increased compressive strengths. The compressive response is found to be influenced by the pore sizes, their distributions and spacing. A statistical model is used to relate the compressive strength to the relevant pore structure features, which is then used as a base model in a Monte-Carlo simulation to evaluate the sensitivity of the predicted compressive strength to the model terms.

Method on the aging evaluation in nuclear power plant concrete structures

International Nuclear Information System (INIS)

Kitsutaka, Yoshinori; Tsukagoshi, Masayuki

2014-01-01

In this paper, method on the durability evaluation in nuclear power plant concrete structures was investigated. In view of the importance of evaluating the degree of deterioration of reinforced concrete structures, relationships should be formulated among the number of years elapsed, t, the amount of action of a deteriorative factor, F, the degree of material deterioration, D, and the performance of the structure, P. Evaluation by PDFt diagrams combining these relationships may be effective. A detailed procedure of durability evaluation for a reinforced concrete structure using PDFt concept is presented for the deterioration factors of thermal effect, irradiation, neutralization and penetration of salinity by referring to the recent papers

Development of fast reactor containment safety analysis code, CONTAIN-LMR. (3) Improvement of sodium-concrete reaction model

International Nuclear Information System (INIS)

Kawaguchi, Munemichi; Doi, Daisuke; Seino, Hiroshi; Miyahara, Shinya

2015-01-01

A computer code, CONTAIN-LMR, is an integrated analysis tool to predict the consequence of severe accident in a liquid metal fast reactor. Because a sodium-concrete reaction behavior is one of the most important phenomena in the accident, a Sodium-Limestone Concrete Ablation Model (SLAM) has been developed and installed into the original CONTAIN code at Sandia National Laboratories (SNL) in the U.S. The SLAM treats chemical reaction kinetics between the sodium and the concrete compositions mechanistically using a three-region model, containing a pool (sodium and reaction debris) region, a dry (boundary layer (B/L) and dehydrated concrete) region, and a wet (hydrated concrete) region, the application is limited to the reaction between sodium and limestone concrete. In order to apply SLAM to the reaction between sodium and siliceous concrete which is an ordinary structural concrete in Japan, the chemical reaction kinetics model has been improved to consider the new chemical reactions between sodium and silicon dioxide. The improved model was validated to analyze a series of sodium-concrete experiments which were conducted in Japan Atomic Energy Agency (JAEA). It has been found that relatively good agreement between calculation and experimental results is obtained and the CONTAIN-LMR code has been validated with regard to the sodium-concrete reaction phenomena. (author)

Embedded micro-sensor for monitoring pH in concrete structures

Science.gov (United States)

Srinivasan, Rengaswamy; Phillips, Terry E.; Bargeron, C. Brent; Carlson, Micah A.; Schemm, Elizabeth R.; Saffarian, Hassan M.

2000-04-01

Three major causes of corrosion of steel in concrete are chloride ions (Cl-), temperature (T) and acidity (pH). Under normal operating temperatures and with pH above 13, steel does not undergo pitting corrosion. In presence of Cl-, if the pH decreases below 12, the probability of pitting increases. Acid rain and atmospheric carbon dioxide cause the pH to drop in concrete, often leading to corrosion of the structure with the concomitant cost of repair or replacement. Currently, the pH level in concrete is estimated through destructive testing of the structures. Glass ISFET, and other pH sensors that need maintenance and calibration cannot be embedded in concrete. In this paper, we describe an inexpensive solid state pH sensor that can be embedded in concrete, to detect pH changes at the early stages. It employs a chemical reagent, trinitrobenzenesulfonic acid (TNBS) that exhibits changes in optical properties in the 12 - 14 pH range, and is held in a film of a sol-gel/TNBS composite on an optically transparent surface. A simple LED/filter/photodiode transducer monitors pH-induced changes in TNBS. Such a device needs no periodic calibration or maintenance. The optical window, the light-source and sensor can be easily housed and encapsulated in a chemically inert structure, and embedded in concrete.

Thick Concrete Specimen Construction, Testing, and Preliminary Analysis

Energy Technology Data Exchange (ETDEWEB)

Clayton, Dwight A. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States); Hoegh, Kyle [Univ. of Minnesota, Minneapolis, MN (United States); Khazanovich, Lev [Univ. of Minnesota, Minneapolis, MN (United States)

2015-03-01

The purpose of the U.S. Department of Energy Office of Nuclear Energy’s Light Water Reactor Sustainability (LWRS) Program is to develop technologies and other solutions that can improve the reliability, sustain the safety, and extend the operating lifetimes of nuclear power plants (NPPs) beyond 60 years. Since many important safety structures in an NPP are constructed of concrete, inspection techniques must be developed and tested to evaluate the internal condition. In-service containment structures generally do not allow for the destructive measures necessary to validate the accuracy of these inspection techniques. This creates a need for comparative testing of the various nondestructive evaluation (NDE) measurement techniques on concrete specimens with known material properties, voids, internal microstructure flaws, and reinforcement locations. A preliminary report detailed some of the challenges associated with thick reinforced concrete sections and prioritized conceptual designs of specimens that could be fabricated to represent NPP concrete structures for using in NDE evaluation comparisons. This led to the construction of the concrete specimen presented in this report, which has sufficient reinforcement density and cross-sectional size to represent an NPP containment wall. Details on how a suitably thick concrete specimen was constructed are presented, including the construction materials, final nominal design schematic, as well as formwork and rigging required to safely meet the desired dimensions of the concrete structure. The report also details the type and methods of forming the concrete specimen as well as information on how the rebar and simulated defects were embedded. Details on how the resulting specimen was transported, safely anchored, and marked to allow access for systematic comparative NDE testing of defects in a representative NPP containment wall concrete specimen are also given. Data collection using the MIRA Ultrasonic NDE equipment and

Deterioration of Concrete Structures

DEFF Research Database (Denmark)

Thoft-Christensen, Palle

Chloride ingress is a common cause of deterioration of reinforced concrete bridges. Concrete may be exposed to chloride by seawater or de-icing salts. The chloride initiates corrosion of the reinforcement, which through expansion disrupts the concrete. In addition, the corrosion reduces the cross...

Numerical Limit Analysis of Reinforced Concrete Structures

DEFF Research Database (Denmark)

Larsen, Kasper Paaske

For more than half a century, limit state analysis based on the extremum principles have been used to assess the load bearing capacity of reinforced concrete structures. Extensi- ve research within the field has lead to several techniques for performing such analysis manually. While these manual...... methods provide engineers with valuable tools for limit sta- te analysis, their application becomes difficult with increased structural complexity. The main challenge is to solve the optimization problem posed by the extremum principles. This thesis is a study of how numerical methods can be used to solve...... limit state analysis problems. The work focuses on determination of the load bearing capacity of reinforced concrete structures by employing the lower bound theorem and a finite element method using equilibrium elements is developed. The recent year’s development within the field of convex optimization...

Overview of the age-related degradation of nuclear power plant structures

International Nuclear Information System (INIS)

Deng, Daniel

2004-01-01

License renewal of nuclear power plants is an issue of increasing interest to the U.S. nuclear industry and the U.S. NRC. This paper presents and evaluates the plausible age-related degradation mechanisms that may affect the concrete and steel containment structures and other Class I structures to continue to perform their safety functions. Preventive and/or mitigative options are outlined for managing degradation mechanisms that could significantly affect plant performance during the license renewal period. The provided technical information and the degradation management options may be used as references for comparison with plant specific conditions to ensure that age-related degradation is controlled during the license renewal term. Plausible degradation mechanisms described and analyzed as they may affect the concrete, reinforcing steel, containment steel shell, prestressed-tendon, steel liner and other structural components typically used in Class I structures. The significance of these age-related degradation mechanisms to the structural components are evaluated, giving consideration to the design basis and quality of construction; typical service conditions; operating and maintenance history; and current test, inspection and refurbishment practices for containment and Class I structures. Degradation mechanisms which cannot be generically dispositioned on the basis of the two-step approach: (1) they will not cause significant degradation, or (2) any potential degradation will be bounded by current test, inspection, analytical evaluation, and/or refurbishment programs are identified. Aging degradation management measures are recommended to address the remaining age-related degradation mechanisms. A three-phase approach for the management of the containment and Class I structures is introduced. Various techniques, testing tools and the acceptable criteria for each step of the evaluation of the structures status are provided. The preventive and mitigative

Contrastive Numerical Investigations on Thermo-Structural Behaviors in Mass Concrete with Various Cements

Science.gov (United States)

Zhou, Wei; Feng, Chuqiao; Liu, Xinghong; Liu, Shuhua; Zhang, Chao; Yuan, Wei

2016-01-01

This work is a contrastive investigation of numerical simulations to improve the comprehension of thermo-structural coupled phenomena of mass concrete structures during construction. The finite element (FE) analysis of thermo-structural behaviors is used to investigate the applicability of supersulfated cement (SSC) in mass concrete structures. A multi-scale framework based on a homogenization scheme is adopted in the parameter studies to describe the nonlinear concrete behaviors. Based on the experimental data of hydration heat evolution rate and quantity of SSC and fly ash Portland cement, the hydration properties of various cements are studied. Simulations are run on a concrete dam section with a conventional method and a chemo-thermo-mechanical coupled method. The results show that SSC is more suitable for mass concrete structures from the standpoint of temperature control and crack prevention. PMID:28773517

Standard practice for qualification of journeyman painters for application of coatings to concrete surfaces of safety-related areas in nuclear facilities

International Nuclear Information System (INIS)

Anon.

1984-01-01

This practice provides a standard qualifying method for journeyman painters to verify their proficiency and ability to attain the required quality for application of specified coatings to concrete surfaces in safety-related areas in a nuclear facility. Variations or simplifications of the practice set forth herein may be appropriate for special coating work such as maintenance. It is not the intent of this practice to mandate a singular basis for all qualifications. Evaluation of the journeyman painter being qualified in accordance with this practice, shall be by qualified agents as specified in 4.1. Reports shall be prepared as specified in Section 5, and qualification as specified in Section 6. It is the intent of this practice to judge only the ability of the journeyman painter to apply specified coatings with the proper tools and equipment

Ceramic ware waste as coarse aggregate for structural concrete production.

Science.gov (United States)

García-González, Julia; Rodríguez-Robles, Desirée; Juan-Valdés, Andrés; Morán-Del Pozo, Julia M; Guerra-Romero, M Ignacio

2015-01-01

The manufacture of any kind of product inevitably entails the production of waste. The quantity of waste generated by the ceramic industry, a very important sector in Spain, is between 5% and 8% of the final output and it is therefore necessary to find an effective waste recovery method. The aim of the study reported in the present article was to seek a sustainable means of managing waste from the ceramic industry through the incorporation of this type of waste in the total replacement of conventional aggregate (gravel) used in structural concrete. Having verified that the recycled ceramic aggregates met all the technical requirements imposed by current Spanish legislation, established in the Code on Structural Concrete (EHE-08), then it is prepared a control concrete mix and the recycled concrete mix using 100% recycled ceramic aggregate instead of coarse natural aggregate. The concretes obtained were subjected to the appropriate tests in order to conduct a comparison of their mechanical properties. The results show that the concretes made using ceramic sanitary ware aggregate possessed the same mechanical properties as those made with conventional aggregate. It is therefore possible to conclude that the reuse of recycled ceramic aggregate to produce recycled concrete is a feasible alternative for the sustainable management of this waste.