Seismic cracking of concrete gravity dams by plastic–damage model using different damping mechanisms

Utilizing two different damping mechanisms, seismic cracking response of concrete gravity dams is examined by a plastic–damage model implemented in three-dimensional space. The material constitutive law employed herein is based on the one proposed by Lee and Fenves for the 2-D plane stress case. This plastic–damage model basically intended for cyclic or dynamic loading was founded on the combination of non-associated multi-hardening plasticity and isotropic damage theory to simulate the irreversible damages occurring in fracturing process of concrete. In this study, considering the HHT scheme as an implicit operator, the time integration procedure to iteratively solve the governing nonlinear equations is presented. Further, seismic fracture responses of gravity dams due to constant and damage-dependent damping mechanisms are compared. In order to assess the validity of the proposed model, several simple examples are solved and their results are presented first. Subsequently, Koyna gravity dam, which is a benchmark problem for the seismic fracture researches, is analyzed. It is concluded that employing the damage-dependent damping mechanism leads to more extensive damages and also predicts more reliable crack patterns in comparison with the constant damping mechanism in seismic analysis of concrete dams. Furthermore, including dam–water interaction intensifies the existing differences between the results of the two damping mechanisms.