Seismic Response of RC Bridge considering scour effect: A Case Study of Kathmandu Valley

Bridge foundation scour is one of the major problems for bridges in Nepal. Kathmandu Valley, which is the main economic hub and capital of Nepal lies in a seismically active zone. In this study, a bridge spanning over Bagmati River in the Valley is studied as a reference bridge to assess seismic response of the typical bridge affected by scouring. Modal analysis of the bridge revealed the bridge becomes more flexible when the scour depth of over 2 m is considered. A series of pushover analysis is conducted on the bridge pier with varying level of scour damage. It is observed that with increasing scour the damages are transferred from the bridge piers to the piles. The nonlinear time history analysis revealed that scouring could have beneficial impact in response of pier at the cost of the piles. Scouring also increased the bearing responses and relative displacement between adjacent bridge decks, abutment and deck thus increasing the probability of bearing failure and deck unseating, respectively. Moreover, more frequent pounding occurrences were also observed leading to more severe localized damages at bridge joints.