New Fragility Curves for Evaluation of the Vulnerability of Bridges to Earthquakes in Iran

Bridges are vulnerable structures in transportation networks, as demonstrated by the results of recent earthquakes worldwide. Their failure can lead to disruptions in the functionality of road networks and cause delays in emergency response and recovery after earthquakes. Researchers have developed different fragility functions to assess the vulnerability of bridges to earthquakes. However, suitable fragility curves are not available for many types of bridges for seismic-risk assessment of transportation networks. The current study presents new fragility functions for four common bridge categories in Iran. For this purpose, existing fragility curves were collected through a systematic literature review according to the bridge typologies. The analytical hierarchy process was used to adjust the collected functions for the case of Iran based on expert opinion, considering local practices, bridge similarities, and construction quality. The newly developed fragility functions were validated by converting the data to vulnerability curves and comparing them to the damage observed to bridges from past earthquakes in Iran and other countries under similar conditions. The results revealed that, for over 50% of the evaluated damaged bridges, the relative error in vulnerability curves for estimating the loss ratio was below 20%.