Seismic Assessment of Three Generations of Isfahan Bridges Using Fragility Curves

Highway Bridges are a major part of the transportation network and an important part of a country's national economy. Despite numerous studies on their seismicity and fragility, very little research has comprehensively addressed all of their dimensions. In this regard, the purpose of this study is to consider the unique details of the design period of these bridges in Isfahan City. To do so, the bridges of the last 50 years in Isfahan were examined through fragility curves. Considering uncertainties and changes in loading in this study is one of the most important surveys conducted through the non-linear history-time analysis method. The 1971 San Fernando and 1989 Loma Prieta earthquakes revolutionized the philosophy of bridge design. Therefore, the study of the three bridges that were designed and built in the three periods before the San Fernando earthquake, after that and after the Loma Prieta earthquake has been done. The results of this study showed that due to the significant improvements in different seismic codes, the possibility of damage to bridges at different times, under the influence of different earthquake intensities is likely. Also, according to the results of this study, column failure is not the sole criterion of bridge failure and the involvement of different components of a bridge in probabilistic seismic evaluation of that bridge will lead to greater fragility. Therefore, in order to evaluate the probabilistic seismicity properly, in addition to the column, the involvement of all bridge members must be considered.