Abstract:The Liuhuanggou Bridge in the Lanzhou—Urumqi high-speed railway, which is near a fault zone, has been threatened by near-fault earthquakes for a long time. In this study, the seismic vulnerability of the bridge was analyzed with a nonlinear finite element model of the bridge containing a three-dimensional soil layer. The model was established by using OpenSees software. Incremental dynamic analysis and probabilistic seismic demand models were adopted, and the four typical continuous piers of the bridge were examined. Given the uncertainty of bridge materials, numerous model-ground motion samples were obtained with the Latin hypercube sampling method for nonlinear dynamic response analysis, and the upper and lower limits of the bridge system’s vulnerability curve were obtained with the first-order boundary method. Results show that the seismic performance of the bridge system is good, and the probability of complete damage is less than 30% under extremely rare earthquakes in the area; the seismic performance of single pier is excellent, and the probability of complete damage is only 6.92% under extremely rare earthquakes; when the earthquake load reaches 0.35g, the pier is at the critical point of elastic stage and plastic stage; the piers with a relatively high height (3# and 4#) have greater stiffness and stronger capacity of deformation and dissipation than relatively low piers (1# and 2#). This study evaluates the seismic performance of the Liuhuanggou Bridge in Lanzhou—Urumqi high-speed railway during simulated near-fault earthquakes, which can provide an important basis for risk prevention before the earthquake and post-earthquake decision-making on disaster relief and mitigation.
