Optimal seismic isolation characteristics for bridges in moderate and high seismicity areas

Abstract

This paper aims to identify the optimal properties of seismic isolation systems (SISs) for bridges in moderate seismicity areas (MSAs) and high seismicity areas (HSAs). Amplitude and spectral parameters of ground motions are proposed to identify these areas. A parametric study, with varying SIS properties, is carried out, and the seismic isolation performance is evaluated for several locations within MSAs and HSAs in North America and Europe. The optimal characteristic strength, Qd, and post-elastic stiffness, Kd, of SISs are determined for each seismic area class to minimize seismic forces and displacement demands. Results indicate that ground motions for MSAs have a rich high frequency content, causing seismic acceleration spectrum to decrease more rapidly with the elongation of the structure period. SISs with low-to-moderate energy dissipation capacities show the best performance for MSAs, while HSAs require SISs with higher damping capacities. Ranges for optimal Qd and Kd of SISs for bridges in MSAs and HSAs are proposed.