A procedure for the evaluation of the seismic vulnerability of bridge networks

Bridge owners need a procedure for the evaluation of the seismic vulnerabilty of bridge at a network level and assess the best resource allocation with the aim of minimizing the consequences due to an earthquake. The proposed procedure takes into account the economic losses derived from the degradation of the transportation network due to an earthquake. Bridges are the main elements subjected to seismic risk and their vulnerability is evaluated according to fragility curves. The reduction of transportation capacity of the system caused by the damage to the bridges is quantified. The final result consist in global delay in the network versus seismic action occurring time. This can be considered the system fragility curve. An iterative procedure finally defines the priority for optimal budget allocation for retrofitting according to the results for damaged and undamaged network with and without retrofitting. The procedure has been tested on a real bridge network located in the North-eastern part of Italy.