CHAPTER 4 Dams and Hydraulic Structures Applications. Remedial Works Book Editor(s):Alain Sellier, Alain SellierSearch for more papers by this authorÉtienne Grimal, Étienne GrimalSearch for more papers by this authorStéphane Multon, Stéphane MultonSearch for more papers by this authorÉric Bourdarot, Éric BourdarotSearch for more papers by this author First published: 30 June 2017 https://doi.org/10.1002/9781119437703.ch4 Read the full textAboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Swelling Concrete in Dams and Hydraulic Structures: DSC 2017 RelatedInformation

Some large civil engineering structures, principally certain concrete dams, are subject to the structural effects of Alkali-silica reaction (ASR). Due to the directions of loading and reinforcement, the stress state is mostly anisotropic. The aim of this paper is to describe the impact of applied stresses and restraint due to reinforcement or boundary conditions on ASR-expansion and induced anisotropic cracking. After the definition and validation of the poromechanical modelling, the paper gives a detailed description of the effects of different aspects of stress (in one, two or three directions) and reinforcement on ASR-expansion for engineers in charge of damaged structures.

CHAPTER 2 Physico-Chemical Mechanisms. Experimental Test Book Editor(s):Alain Sellier, Alain SellierSearch for more papers by this authorÉtienne Grimal, Étienne GrimalSearch for more papers by this authorStéphane Multon, Stéphane MultonSearch for more papers by this authorÉric Bourdarot, Éric BourdarotSearch for more papers by this author First published: 30 June 2017 https://doi.org/10.1002/9781119437703.ch2 Read the full textAboutPDFPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShareShare a linkShare onFacebookTwitterLinked InRedditWechat Swelling Concrete in Dams and Hydraulic Structures: DSC 2017 RelatedInformation

Delayed ettringite formation (DEF) is a process which can lead to swelling and cracking of concrete. This paper proposes a chemical model to predict the kinetics and the amount of DEF in concretes subjected to high-temperature curing. The modelling considers several types of phenomena: the thermodynamic equilibria of hydrate crystallisation, the binding of ionic species to hydrated calcium silicates and the mass balance equations, which include the diffusion mechanisms. All the constitutive equations are provided and the thermodynamic constants found from a wide-ranging literature review are given in particular detail. The model has been implemented in a finite element code. The numerical results give the amount of ettringite and monosulphates, and ionic concentration fields in the simulated structure. They are compared with experimentation in which the early-age thermal cycle and long-term alkali release combine to cause DEF.

This article presents the different steps of a research process initiated in the field of dam engineering, through collaboration between EDF and ENS Cachan, following Jacky Mazars' pioneering work on the application of the damage concept to concrete structure modelling. Considering the importance of concrete swelling phenomena for the long-term behaviour of concrete dams, special efforts have been devoted to the development of a rheologic model in this field. This paper explains how the research performed contributed to the elaboration and the justification of the main equations included. An application to the Temple-sur-Lot dam is presented.

ABSTRACT This article presents the different steps of a research process initiated in the field of dam engineering, through collaboration between EDF and ENS Cachan, following Jacky Mazars' pioneering work on the application of the damage concept to concrete structure modelling. Considering the importance of concrete swelling phenomena for the long-term behaviour of concrete dams, special efforts have been devoted to the development of a rheologic model in this field. This paper explains how the research performed contributed to the elaboration and the justification of the main equations included. An application to the Temple-sur-Lot dam is presented.

Since 1964, the Temple-sur-Lot Dam, built in southwest France in 1948, has been subject to continuous alkali-aggregate reaction (AAR)-induced displacements despite low and relatively constant alkali content in the concrete and nonsignificant residual swelling test results. It has been assumed that a substitution process between alkali and calcium in the alkali-aggregate reactive gel could explain this long-term behavior As the calcium substitution phenomenon is very slow, it cannot be detected using a conventional residual swelling test, so an original method to assess the AAR kinetics and the residual swelling capability is proposed. This method first involved a laboratory test dealing with the silica consumption kinetics and, second, a numerical finite element inverse analysis of the dam, which included the consumption kinetics measured in the laboratory. The final swelling amplitude was thus fitted from only one observed structural displacement rate at a given period The model prediction capability was validated through the comparison between the displacement of instrumented points predicted by the calculations (not used for the fitting) and the variations measured on the dam. Finally, calculations were performed to predict the future displacements and damage fields of the dam.

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ABSTRACT This article presents the recent French recommendations drawn up by FRCOLD for the design of gravity dams. Recognising the disparities in the approaches of the various dam engineering bodies, the recommendations aim at harmonising practices to arrive at a standard approach. They adopt the same limit state design method as already used in the Eurocodes, with particular emphasis on cracking and shear strength limit states. They define a series of new parameters which were not introduced in earlier methods such as characteristic strength of materials, partial factors of safety and inclusion of new design situations. The background to the new format is the probabilistic concept of the acceptable design requirements. These recommendations are applied to an existing concrete gravity dam and the results are compared with other international guidelines.

Modeling the behavior of alkali aggregate reaction (AAR)damaged concrete is made complex by the large number of elementary physical phenomena to be taken into account (concrete reactivity, thermal activation, moisture dependence, concrete rheology, and damage interaction). This paper presents the elementary physical principles that lead to the formulation of a visco-elasto-plastic orthotropic damage model including chemical pressure induced by AAR. Particular attention is also paid to the modeling of moisture effects on AAR development and on drying shrinkage. The constitutive modeling proposed is developed into the framework of an anisotropic damage theory to realistically model the strong cracking anisotropy and swelling observed on affected reinforced beams. This paper is followed by a second one in which a calibration procedure is given for the model parameters and experimental results are used to verify the capability of the model to describe the mechanical behavior of degraded structures under various environmental and loading conditions.

ABSTRACT Concrete structures affected by alkali silica reaction deteriorate slowly. Damage kinetic and amplitude are modelled in the purpose to know their residual safety margin at various terms. Numerical modelling used includes several phenomena that involve a large number of material parameter to assess. The sensitivity study presented in this paper tries to draw the more influent parameters in order to assess them with a particular attention.

Alkali-silica reaction (ASR) is a concrete pathology due to chemical reactions involving reactive silica from reactive aggregates and the inner solution of concrete. Main effects are swelling, cracking, and reduction in the mechanical properties of affected concretes. Water is very important for ASR; the more available water, the more expansion and degradation. This article presents new laws for modeling of the influence of water upon ASR. They are based on experimental results and then used to simulate results taken out of the scientific literature.

ABSTRACT Assessment of ASR-damaged structures is a major concern for bridge and dam owners in France. Thus, validated models are needed in order to predict the behavior and residual bearing capacity of such works. With this aim, a large experimental program was carried out at the LCPC with EDF as a partner. Measurements were taken from the behavior of structures and specimens placed in various moisture and mechanical environments in order to realize a complete data bank. The mechanical analysis of the measurements showed the significance of ASR-induced strains anisotropy due to stresses, and moisture effect on ASR-induced expansion amplitude, on predicted behavior. They appear to be the main parameters to be accounted for in order to obtain good predictive models.

ABSTRACT Nowadays, knowledge about ASR mechanisms is good enough to prevent new cases. Nevertheless a numerical tool seems necessary for all affected structures. This article deals with a new modelling based on the description of alkalis and calcium transport within concrete. It takes into account the effect of the size and distribution of reactive aggregates. Results from an experimental campaign and corresponding numerical simulations are presented and compared.