Seismic performance of near-fault girder bridges based on laminated rubber bearings under the impact of sequential earthquakes

Strong aftershocks frequently follow near-fault earthquakes, exacerbating the damage to bridges already impacted by the main shock. However, current seismic design codes worldwide overlook the adverse effects of aftershocks on near-fault bridges. Therefore, it is imperative to conduct research on the seismic performance of near-fault girder bridges under sequential earthquakes. This study proposes a seismic isolation design for near-fault girder bridges subjected to sequential earthquakes, utilizing laminated rubber bearings, sacrificial shear keys, and cable-type unseating prevention devices. Seismic ground motion records from typical stations during the Turkey-Syria earthquakes were collected to assess the seismic safety of bridges. Nonlinear time-history analysis systematically investigated the seismic displacements of the laminated rubber bearings and girder, as well as the seismic damage of shear keys and pier. The results show that the lateral displacement of the girder induced by the sequential earthquake was approximately 1.5 times greater than that caused by a single main shock, while the longitudinal displacement of the girder remained similar. The seismic isolation design proposed in this study not only controlled the relative displacement between the piers and the girder but also effectively protected the pier from severe seismic damage, ensuring the bridge's functionality after the sequential earthquake.