Effects of fault rupture on seismic responses of fault-crossing simply-supported highway bridges

Past earthquakes have demonstrated that fault-crossing bridges were susceptible to damage or even collapse. This study focused on investigating the effects of fault rupture on seismic responses of a simply-supported highway bridge. Six sets of ground motions with fling-step effect in fault-parallel direction and forward directivity effect in fault-normal direction were selected as the inputs from four strike-slip earthquakes. A simplified baseline correction method was used to recover the permanent ground displacement in these records. A typical simply-supported girder bridge located in China was taken as the prototype bridge and the numerical model of the bridge was generated in OpenSees. Effects of fault crossing angles (from 15 degrees to 165 degrees) and the amplitude of permanent ground displacement on the seismic behaviors of the bridge were evaluated. More specially, two special cases, i.e. contact case and separation case, are considered and compared considering the contact and separation between the girder and abutment in bridge longitudinal direction. Results revealed that the piers and bearings in contact case have larger seismic damage compared to separation case, and the separation case causes the unseating of the bridge spans. It was found that the fault crossing angle has a great impact on the seismic responses of the fault-crossing bridge. The fault crossing angle from 60 degrees to 90 degrees causes the lowest structural seismic responses. The permanent ground displacement is another important influence factor of the bridge. Unlike the bridges without crossing fault, the peak values of the responses of the bridge increase as the pulse amplitudes and pulse periods increase.