Development of methology for seismic design of concrete gravity dam

Abstract

Earthquake analysis and earthquake resistance design of dams is of major importance because of the catastrophic consequences if such a structure is to fail. In India we don’t have any guidelines to take into account the seismic load for the analysis of Dam. In the absence of any well-defined method, design offices generally use an empirical method which does not consider the dynamic properties of dam and different earthquake zone. This study is an attempt to develop guidelines to consider seismic force for the analysis of concrete gravity dam. An equivalent static method for seismic design of concrete gravity dam is developed considering the dynamic properties of the dam as well as different earthquake zones. For this to achieve, a family of concrete gravity Dam with varying height, base-width and side slope is analyzed using finite element software ANSYS. Dams are modeled with 2-D plane strain elements. Dynamic properties of all the selected dams are evaluated. A regression analysis is carried out on the modal properties obtained from the finite element analysis in order to develop empirical relation between time period, height and base width. The minimum number of modes that must be taken into for the analysis is decided by considering the mass participation ratios. Design base shear is calculated by using the Design horizontal acceleration spectrum value and Seismic weight of the building. A method is proposed to distribute the calculated base shear over the height of the Dam.