Theory and implementation of plastic-damage model for concrete structures under cyclic and dynamic loading

In this dissertation, the constitutive relations for a new plastic-damage model based on plasticity and continuum damage mechanics, and its numerical implementation are presented. The model is especially developed to simulate crack initiation and propagation in concrete structures subjected to quasi-static or dynamic loads.; The rate-independent plastic-damage model is developed based on continuum damage mechanics and a plasticity model for concrete. Cracking is represented by the evolution of damage in strength and stiffness degradation. To make the system well-posed, the viscoplastic regularization based on the Duvaut-Lions model is imposed on the rate-independent model. This leads to a rate-dependent version of the plastic-damage model. A formulation for evaluating the characteristic length, which is assumed to be proportional to the crack bandwidth, is presented based on the derived internal length of the Duvaut-Lions model.; A solution procedure for both rate-independent and rate-dependent models is developed in the context of the finite element method and the backward-Euler method. A new version of the return-mapping algorithm is presented to solve nonlinear equations for the numerical system. The present return-mapping algorithm is efficient for a model having principal stresses in the yield function. The algorithmic tangent stiffness is derived for both rate-independent and rate-dependent models.; Through the numerical examples, the present plastic-damage model is shown to give the results that agree well with experimental data for concrete under cyclic loading as well as monotonic loading. Stiffness degradation and crack opening/closing are simulated properly. The numerical algorithm using the characteristic length gives objective results for the finite element mesh in the dissipated energy sense. In the dynamic tests, it is shown that both global and local responses are fairly mesh-objective, if the viscosity parameter is chosen appropriately based on the crack bandwidth.