Aftershock risk assessment and the decision to Open traffic on bridges.

"Critical issues in emergency management after a seismic event are assessing the functionality of the main. infrastructures (hospitals, road network, etc.) and deciding on their usability just after the mainshock. The. use of a pure analytical tool to assess the aftershock risk of a structure can be contrasted with the limited time. available to make a decision about the usability of a structure. For this reason, this paper presents a method. for evaluating post-earthquake bridge practicability based on a rational combination of information derived. from numerical analyses and in situ inspections. In particular, we propose an effective tool to speed up the. decision-making process involved in evaluating the seismic risk of mainshock-damaged bridges in the. context of aftershocks. The risk is calculated by combining the aftershock hazard using the Omori law. and the fragility curves of the structure, which are calculated using the regression analysis of a sample of. results obtained with data randomly generated by the Latin Hypercube Sampling technique and updated. based on the results of in situ inspection. Different decision criteria regarding the practicability of bridges. are discussed, and a new criterion is proposed. This tool was applied to an old highway RC viaduct. There. are two main findings, including the high sensitivity to Bayesian updating (especially when the damage. predicted by numerical analysis does not match the real damage) and the criteria used to decide when. re-open bridges to traffic.