Probabilistic evaluation of seismic vulnerability of multi-span ‎bridges in north of Iran

Bridges are known as the most susceptible components of any and transportation system. That is why before the earthquake in vulnerability assessment, to take the necessary actions. The ‎generation of vulnerability functions in the form of fragility curves is a common approach for assessing bridges ‎seismic vulnerability. The purpose of this study, Using an analytical method for the production of ‎fragility curves for a road bridge in Mazandaran Province. Since this curves used for planning before and after the ‎earthquake, and in order to increase the reliability of them, in this study we tried to use the most accurate analytical ‎methods (non-linear time history analysis) and most prestigious modeling assumptions. Due to the specific ‎characteristics of far fault earthquakes, effects of such earthquakes on bridges have been investigated using fragility ‎curves. Due to the geometry of the bridge for exact analysis, bridges was under 100 pairs of earthquake ‎records in orthogonal directions and fragility curves was drawn and then were compared. Observed that changing the diameter of the bridge piers affect how much on the. One of ‎the common simplifications used in modeling are: elimination of abutment and foundation and pile by fixing the ‎abutment and foundations in modeling. It can be seen that by eliminating this effect, increase the median values of ‎fragility and in fact to reduce probability of vulnerability in Charts. After time history analysis it was found that by ‎reducing the diameter of the piers, relative displacement (drift) in the longitudinal direction and in the transverse ‎direction increases