Energy-Based Evaluation on Soil–Structure-Interaction-Related Damping of Inelastic Bridge Pier Structure Subjected to Pulse-like Velocity Ground Motion

Abstract

This study proposed a procedure of using the energy method to evaluate the SSI-related damping effect when the soil–structure interaction (SSI) was considered in a bridge pier system, which can thus be deemed a soil–foundation–superstructure (SFS) inelastic system. Firstly, the SSI is implemented by adopting a discrete-time recursive filter approach as well as frequency-dependent foundation–soil impedance functions to solve for the external soil forces exerted onto the foundation. Then, by integrating such external soil forces into the motion equations of the SSI-based SFS system, the energy equations can be formulated during the ground motions. To demonstrate the proposed procedure, an implementation study involving a bridge pier was carried out, considering two earthquake recordings. The resultant energy quantities and SSI-related damping ratio shed light on how the aspects of earthquake characteristics affected the energy dissipation mechanism of the bridge pier SSI-based SFS system. This proposed procedure renders a promising solution for quantifying the soil role in the seismic energy dissipation of arbitrary single- and multiple-degree-of-freedom systems considering the SSI effect. The results obtained show that the SSI effect was suppressed when the SFS system underwent near-fault earthquakes, which illustrated that the stiffness and damping contribution from the soil was not pronounced. Furthermore, near-fault earthquakes with large incremental velocities may lead to a low SSI-related damping ratio (SSIDR).