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3D Modeling of Damage and Cracking in Anisotropic Concrete and its Application in Seismic Analysis of Dams

Daneshyar, Alireza | 2019

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  1. Type of Document: Ph.D. Dissertation
  2. Language: Farsi
  3. Document No: 51820 (09)
  4. University: Sharif University of Technology
  5. Department: Civil Engineering
  6. Advisor(s): Ghaemian, Mohsen
  7. Abstract:
  8. A finite element model for seismic analysis of concrete arch dams is proposed. Material inelasticity as well as joints nonlinearity is considered. In order to provide a precise description of concrete response, a novel plastic-damage constitutive model for plain concrete is developed. For this purpose, the microplane theory is proposed for overcoming the deficiency of available anisotropic continuum plastic-damage models in reproducing the true anisotropic nature of damage in multidimensional loadings.Based on the microplane theory, the degeneration process in concrete is considered along with plastic deformations. Using the principle of strain energy equivalence, a transformation between the nominal and effective states of material is achieved, that results in a decoupled formulation for damage and plasticity. A yield function with multiple internal variables and a non-associative flow function are employed to describe the plastic behavior of concrete. In order to discriminate between the behavior of concrete in tension and compression, stress tensor is decomposed into tensile and compressive parts, and two sets of microplanes are defined for each material point,leading to corresponding independent anisotropic damage tensors in tension and compression.Utilizing rate-dependent anisotropic damage-plastic model, irreversible deformations,stiffness degeneration, induced anisotropy, closing/reopening of cracks,and viscous response of concrete are attained. Non-penetration condition, frictional behavior, and adhesion resulted by grouting of contraction and peripheral joints are also modeled in a coupled and rate-dependent manner. Different combinations of material and joints nonlinearities are used to model a system of dam-foundationreservoir.The system is excited using three components of an earthquake, and effect of different sources of nonlinearities is investigated through comparison between results. In addition, capability of the presented anisotropic damage-plastic model is compared against available isotropic formulations. A sensitivity analysis has also been performed to investigate the effect of different assumptions for joints. Owing to high convergence rate of material and joints constitutive models, implicit time integration is employed, which leads to fast and stable solutions
  9. Keywords:
  10. Seismic Analysis ; Arc Dam ; Dam-Reservoir-Foundation Interaction ; Damage Mechanics Model ; Plasticity ; Anisotropic Damage ; Contact Mechanics ; Adhesion ; Friction

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