TRANSIENT-RESPONSE OF RESERVOIR DAM SOIL SYSTEMS TO EARTHQUAKES

A direct time-domain numerical procedure is proposed to analyse the tr ansient dynamic response of two-dimensional reservoir-dam-soil systems . The reservoir extends to infinity and the dam is supported by an unb ounded soil. The structure with either linear or non-linear material p roperties is modelled by the Finite Element Method (FEM). The soil is assumed to be an elastic, isotropic and homogeneous half-space represe nted by a boundary condition in the form of generalized impedance dete rmined by the transient Lamb's solution due to a uniformly distributed traction imposed on the free surface, Guan and Novak.(1) Moreover, a technique is developed to include the influence of the reservoir on th e dam in terms of nodal accelerations along their interface at differe nt time steps. The advantages of the proposed procedure are obvious. F or example, it avoids any additional discretization of the boundaries except the soil-dam interface, and the influence matrix of the fluid i s obtained explicitly using shape functions defined at the upstream fa ce of the dam without the finite analysis of the reservoir so that it works very efficiently. Numerical results for a system consisting of r eservoir, elastic dam and foundation subjected to the San Fernando, 19 71 earthquake ground motion are presented.