Experimental investigation and seismic fragility analysis of isolated highway bridges considering the coupled effects of pier height and elastomeric bearings

Elastomeric bearings are widely utilized in highway bridges and attracting a great deal of attention, although their mechanical behavior has been clearly recognized, the coupled effects of critical bridge structural components and complex mechanical behavior of elastomeric bearings are yet to be well characterized. In this study, experimental investigation and seismic fragility analysis were conducted to evaluate the seismic performance of isolated highway bridges, with a special emphasis on considering the coupled effects of pier height and rate dependent behavior of elastomeric bearings on the bridge response. To this end, real-time hybrid simulation (RTHS) tests featured by a velocity loading control were performed on a typical highway bridge. Two pier heights and two common types of elastomeric bearings including low damping rubber bearing and high damping rubber bearing were paired and tested. The effects of pier height and elastomeric bearings were illustrated by comparing and analyzing a wide range of response quantities of the bridge. The test results indicated that pier height and rate-dependent behavior of elastomeric bearings could remarkably influence the seismic response of the bridge in both individual and combined ways. Subsequently, a hyper-viscoelastic model of elastomeric bearings was proposed to capture their mechanical behavior, then, both the proposed and conventional bilinear models were implemented in the numerical simulation to evaluate the seismic fragility of the bridge. Fragility curves for two bridge components including piers and elastomeric bearings as well as for the bridge system were developed and discussed. The study reveals crucial effects of pier height and mechanical behavior of elastomeric bearings on both the component and system fragility curves of the bridge, it is found that an optimal combination of pier height and elastomeric bearings should be considered to improve the seismic performance of isolated highway bridges.