Seismic fragility of typical bridges in moderate seismic zone

A set of fragility curves for the bridges commonly found in the Central and Southeastern United States (CSUS) is presented. For this purpose, the typical bridges in the region are determined from a bridge inventory, and detail analytical models of the bridges are developed based on experimental and analytical studies. The developed fragility curves can be used for the economic losses due to earthquakes, and the seismic vulnerability of the bridges estimated from the curves provides the priority of retrofit. Most highway bridges in the CSUS are non-seismic designed, thus it is believed that they are vulnerable to the expected earthquakes. Therefore, it is necessary to assess the vulnerability of the bridges and retrofit measures are required to increase the seismic resistance of the bridges. In this paper, the seismic resistance of the bridges retrofitted by several measures such as elastomeric bearings, lead-rubber bearings, and restrainer cables is also evaluated using fragility analysis and compared with that of the as-built bridges to verify the effect of each retrofit measure quantitatively.