Concrete as a multi-physical material with applications to hydro power facilities

Detta är en avhandling från Stockholm : KTH Royal Institute of Technology

Sammanfattning: During its lifetime, a concrete structure is subjected to many different actions, ranging from mechanical loads to environmental actions. To accurately predict its integrity from casting and throughout its service life, a modelling strategy is required that considers mechanical loading but also implicitly accounts for physical effects such as temperature and moisture variations. This is especially true for large concrete structures found in many infrastructure applications such as bridges, nuclear power plants and dams. Modelling concrete as a multi-physical material is becoming an increasingly used approach for which large research efforts are being made, including the development of more refined mathematical and numerical methods as well as considering more physical and chemical variables in the coupled model.The research project, of which this licentiate thesis is the first phase, aims at investigating aging concrete structures at hydro power facilities, with focus on the internal structures of the power plants. This thesis presents a review of advanced mathematical methods and concepts for modelling aging concrete found in the literature which can later be applied to study such structures. The focus is on models that describe the deformational behaviour of concrete where aspects such as aging, cracking, creep and shrinkage are investigated. However, in order to accurately describe such phenomena, a multi-physical approach is adopted where moisture and temperature variations in the concrete are studied. Also, models that describe the chemical behaviour related to hydration and thus in extension aging, are also reviewed and introduced in the multi-physical framework. The use of such models are discussed in the context of the finite element method (FEM), in which coupled models are implemented, verified and applied in the appended papers using two different FE codes.Several verification examples are presented covering different aspects of the implemented models, both in isolation and coupled in a multi-physical setting. By comparing the numerical results with experimental data from the literature it can be shown that it is possible to predict most aspects of aging concrete that have been of interest here. While these examples are all on a laboratory scale, numerical examples and case studies are also provided that exemplify how the models can be applied on a structural scale. By using the developed analysis tools, valuable information and insights can be gained on aging concrete structures and these tools will in the next phase of the research project be applied to large concrete structures at hydro power facilities.

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