Damage Model And Seismic Damage Description Of High-rise Reinforced Concrete Structures

The high-rise structures developed rapidly, but less has been checked up under major earthquakes, and seismic damage mechanism is still not explicit. In order to describe the seismic damage mechanism, the material damage models, member damage models and the whole structure seismic damage description is studied respectively in this paper.Firstly, a plastic damage model for concrete (CPDM) complying with the laws of thermodynamics is proposed based on continuum damage mechanics theory. The expression of plastic Helmholtz free energy, which considers the effect of plasticity and damage, is introduced to be able to adequately describe the plasticity and damage degradation behavior of concrete. Moreover, the Weibull distribution hypothesis of damage index and damage energy release rate is used in deriving the damage evolution equations; the model simulates the effects of damage on the elastic stiffness. The damage constitutive equations, the damage evolution equations and plastic deformation of concrete is presented under uniaxial monotonic and cyclic loading, the proposed model results show good correlation with the experimental data.Secondly, for further evaluating the validity of CPDM applying in seismic damage analysis of concrete structures, the classical seismic damage analysis example for Koyna concrete dam is used. Contrast analysis results show that the proposed concrete plastic damage model could describe seismic damage evolution process well and the damage variable defined could simulate damage accumulation of concrete structures well by recording the concrete structure failure history. Seismic damage analysis based on material damage model can reflect damage mechanism of concrete structure under strong earthquakes.Thirdly, in this paper the seismic damage nonlinear analysis of RC beam column member is studied. The model of 3D beam column element was developed with VUEL subroutine based on ABAQUS/Explicit platform. RC member fiber damage analysis model is established by analyzing section of fiber beam column element with CPDM proposed in this paper, and the member damage index is defined, which can describe the nonlinear damage behavior of RC members under any loadings. Accuracy of the model is identified preliminarily by comparing with the analysis results of solid element. Finally, a combined finite element model for high-rise RC structure based on ABAQUS/Explicit platform is built to analyze the structural seismic damage, and the analysis results are compared with the test results of shaking table, and the analysis results agree well with the test results. The test results show that it is not sufficient for the story drift angle of the structure to verify the structural seismic performance and weak parts. It indicates that the seismic damage description based on material damage model is more reasonable and more reliable to evaluate the whole seismic performance, the weak parts and the seismic damage evolution process of high-rise RC structures.