development of seismic fragility functions for typical iranian multi-span rc bridges with deficient cap beam–column joints

Reinforced concrete (rc) bridges with multi-column bents are the most common bridges in iran. there were no special requirements for design of the cap beam–column joints prior to introduction of the seismic codes and thus many existing bridges have poor joint details. cyclic tests conducted on old multi-column bridge bents have resulted in extensive damage to the joints with little or no damage to the cap beam or columns. in these tests, exterior joints have been damaged more severely than interior joints. the main objective of this research is to develop fragility functions for a typical rc bridge with deficient joint detailing. nonlinear incremental dynamic analyses (ida) are performed on finite element model of the bridge to develop the fragility functions at four performance levels. the model for the bridge bent includes nonlinear spring elements with proper characteristics simulating the hysteretic responses of the interior and exterior joints. the parameters defining the hysteretic characteristics of these springs are derived by comparing the analytical and experimental hysteretic responses of the test specimens. the fragility assessment of the bridge is carried out at component level assuming a probabilistic log-normal distribution of the responses. the fragility of the bridge system is generated using joint probabilistic seismic demand model (jpsdm). the analytical results indicate the bridge system fragility is highly influenced by the fragility of the exterior and interior joints. © 2021, iran university of science and technology.