Development of Fragility Curves for Seismic Performance Comparison of Hammerhead and Multicolumn Bridge Pier

Bhabuk Raj Aryal, Nabin Chandra Sharma

Abstract: In this research, it is primarily intended to assess seismic vulnerability of bridge piers that are commonly used in context of Nepal. Seismic vulnerability are compared for a double span bridge with a typical span of 25m. These two pier sections are analysed in finite element based software SAP 2000. Displacement capacity is determined by non-linear static (Pushover) analysis. Capacity analysis of the pier section shows that the top level displacement is more in case of hammerhead pier than multicolumn pier section. Response analysis is done using time history data of Gorkha earthquake to calculate the demand, after this analysis the top level displacement corresponding to the subjected ground motion is more in case of hammerhead pier than multicolumn pier section. The seismic vulnerability of piers are determined by developing analytical fragility curves. Using the fragility curves, it is concluded that for 0.45g PGA the probability of failure corresponding to slight, moderate, extensive and complete damage are 71.2 %, 12.7 %, 4.6 % & 3.4 % for hammerhead bridge piers and 56.3 %, 9.1 % 3.5 % & 2.1 % for multicolumn bridge piers.

Keywords: fragility curve, multicolumn pier, hammerhead pier, capacity analysis, Seismic vulnerability