Investigation of The Effect of Sediment Inertia on Seismic Response of Concrete Gravity Dams Using Finite Element Model

This paper presents a finite element model to get a reliable estimation of the effect of sediment inertiaon seismic performance of concrete gravity dams considering interaction effects. The equivalent fluid assumption is used to show the sediment behavior. Water is assumed as compressible, inviscid fluid with small amplitude displacements and the dam is modeled as an elastic solid. Due to the complexity of a dam­reservoir-foundation system, the finite element method is an efficient tool for studying the dynamic response of concrete gravity dams in which the different boundary conditions can be simulated more appropriately. In order to seismic analysis, a computational procedure for two-dimensional finite element analysis of system subjected to seismic excitations is developed using Ansys software. The analysis is carried out in time domain considering dynamic excitations. Newmark time integration scheme is developed to solve the time­discretized equations which is an unconditionally stable implicit method. To demonstrate the effect of sediment on seismic performance of concrete gravity dams, the response of Pine Flat dam due to El Centro ground motion is presented as a case study. The model was analyzed and compared with the cases in which the reservoir is assumed without sediment and with 20% volume of sediment. Obtained results show the amplification effect of sediment on seismic response of model.