Seismic responses of an underground powerhouse structure subjected to oblique incidence SV and P waves

Abstract

In this work, the impacts of seismic motion incident angles and the rock-structure interaction (RSI) on the seismic response of an underground powerhouse structure of a hydropower station are studied. Based on the viscous-spring artificial boundary condition, the input methods of oblique incidence SV and P waves are presented by transforming the seismic motion into equivalent nodal forces acting on the nodes of artificial boundaries. Based on the explicit central difference method, an explicit dynamic contact analysis method considering the bonding and damage characteristics of the contact face between the surrounding rock and the underground powerhouse structure is also proposed. Consequently, the proposed methods are implemented into an dynamic finite element program and applied to the seismic damage evolution process analysis for the concrete structure of an underground powerhouse, and the results reveal that (1) the stress and deformation response of the underground powerhouse structure caused by seismic excitations are clearly affected by the incident angle and its degree of damages reaches a maximum when the incident angle is 30°; (2) compared to the case of without the RSI, the damage distribution ranges and the damage coefficient of the underground powerhouse structure are much larger than that in the case of with the RSI; and (3) the contact state of the contact face plays a key role in the dynamic stability of the underground powerhouse structure, and a good contact state can help to reduce the dynamic damage of the underground structure.