Aftershock risk assessment and the decision to open traffic on bridges

Abstract

SUMMARY: 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. © 2013 John Wiley & Sons, Ltd

Hybrid simulation of a multi‐span RC viaduct with plain bars and sliding bearings

“…As highlighted in , the portal piers accumulated damage during each seismic event, while the deck remained in the linear regime. To track the progressive degradation of PSs portal piers, both the maximum concrete strength f pc and the relevant unloading/reloading stiffness 2 f pc / ε psc0 of the OpenSEES RM of Section 3.1 were updated offline according to the test program of Table .…”

“…On the basis of a previous experimental campaign and simulations presented in , OpenSEES‐based numerical simulation of the seismic response of the bridge in the as‐built configuration proved that the most likely damage patterns at the ULS correspond to brittle failure of transverse beams and fixed‐end rotation at beam‐to‐column and base–column joints. Therefore, the installation of pairs of CSB isolation devices between each pier and the deck was proposed for seismic retrofitting, together with the removal of the Gerber saddles.…”

Assessment of the Seismic Behaviour of a Retrofitted Old R.C. Highway Bridge Through PsD Testing

“…14.14 and 14.15. The threshold limit for the drift causing shear failure of the transverse beams is 2 % (Alessandri et al 2013). A 2.4 % drift ratio was reached in the short pier, thus shear failure occurred in the transverse beams.…”

Seismic risk assessment considering cumulative damage due to aftershocks

“…Substituting P ( LS as | MS i , n as ) from Eqn and P ( n as | MS i ) from Eqn into Eqn and performing some simple algebraic manipulations (considering that the sum of the Poisson probability mass function terms is asymptotically equal to unity for large N as values): …”