Effects of Earthquake Wave Direction on Dynamic Response of Earth Dams - Case Study: Shohada Dam

In this paper, the irregularity effects in the initial directions of the seismic loading on the nonlinear time-history responses of the Shohada dam have been investigated. The maximum cross-section of the dam has been simulated by the 2D finite element method under the normal lake level conditions. The near-fault acceleration record of the Tabas earthquake has been applied as dynamic input motion to the two-dimensional numerical models. Numerical analysis has been conducted in the Newmark explicit time integration scheme framework. The main three patterns of horizontal, vertical, and oblique directional seismic loading are considered to investigate the effects of the initial directions of seismic motion propagation. In each case, the seismic responses are compared to the conventional seismic loading responses in the horizontal direction from the upstream (reservoir) to the downstream of the dam. The hardening soil model with small strain (HS-small) and Mohr-Coulomb model was used to model the dam's body and the foundation materials. In most 2D simulations, the initial direction of the input seismic movements has been only in one or two dimensions and in the horizontal or vertical orientation. This study has attempted to compare these traditional seismic loading patterns with other possible states in 2D numerical models. The present study results show that the seismic loading mode with the initial direction of inclination of 45 degrees has the worst and most significant effect on the seismic response of the dam compared to the traditional method of horizontal loading.