A new method for probabilistic aftershock risk evaluation of damaged bridges.

"A critical issue in the emergency management after the earthquake is the functionality. of the main infrastructure (hospitals, road network, etc.) and the decision on their usability. just after the main shock. At present, a decision is taken on the basis of a structure insitu. inspection; an analytical assessment is in contrast with the lack of time and data. For this. reason in this paper a method that rationally combines information from the analytical approach. and the in situ inspection is proposed. In particular an effective tool to speed-up the. decision making phase concerning the evaluation of the seismic risk of mainshock-damaged. structures due to aftershocks has been proposed. The risk is calculated combining the aftershock. hazard using the Omori law and the fragility curves of the structure calculated using. IDA technique and updated using in-situ inspection data. The procedure has been applied to. a highway r.c. bridge. The results have highlighted a high sensitivity to the Bayesian updating. especially when the damage predicted by the numerical analysis does not correspond to the. real damage. The mean annual rates of collapse provided by the method has shown that the. risk structure change dramatically when an aftershock sequence strike the bridge and this. risk decreases with time allowing the authorities to decide if and when re-open the bridge to. traffic."