Response of Steel Bridge Bearings to Reversed Cyclic Loading
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The seismic performance of low and high type steel bridge bearing specimens is investigated in this study. As part of this research, experimental apparatus was developed for investigating the performance of steel bridge bearings. This test apparatus enables large cyclic horizontal loads and displacements to be applied to bearing specimens while keeping gravity loads constant. To increase seismic performance, simple seismic retrofit strategies are proposed and investigated experimentally. To increase the resistance in the longitudinal direction of the high type rocker bearings, retrofitting consisted of welding steel wedges to the masonry plate. It is shown that by retrofitting the existing high type steel bridge bearings it is possible to provide sufficient strength and displacement capability to withstand substantial ground shaking. The weak link in the chain of force transmission may thus become the anchor bolts and/or the reinforced concrete pedestal. In order to understand the influence of the reinforced concrete pedestal and mild steel anchorage on the overall behavior of a high type fixed bearing assembly, a full scale reinforced concrete cap beam with pedestals was constructed. The test results demonstrate the importance of considering the flexibility of the concrete pedestal-anchor bolt system. As a retrofit method for the damaged reinforced concrete pedestal a steel jacket was wrapped around the damaged reinforced concrete pedestal.