ABSTRACT
Bridges are among the most vulnerable elements of infrastructure networks. A prompt recovery of bridge performance and functionality after seismic events is essential to mitigate the detrimental effects and economic losses of traffic disruptions. This can be ensured by suitable levels of seismic resilience, that is the ability to withstand the effects of earthquakes and to recover the original functionality in a timely and efficient way (Bruneau et al. 2003, Chang & Shinozuka 2004, Cimellaro et al. 2010, Bocchini & Frangopol 2012a, 2012b, Decò et al. 2013).
The initial seismic performance and functionality and, consequently, the seismic resilience, may decrease over time due to deterioration processes associated with the effects of aging and environmental aggressiveness (Titi & Biondini 2013, Biondini et al. 2015). Therefore, it is important to combine seismic and environmental hazards to identify cost-effective post-earthquake recovery processes of critical infrastructure facilities, such as bridges, by considering the time of occurrence of the seismic event.
This paper proposes a life-cycle probabilistic approach to cost-optimization of post-earthquake recovery processes under target levels of seismic resilience for concrete bridges under corrosion. The bridge time-variant seismic capacity is evaluated through a general methodology for lifetime assessment of concrete structures exposed to the diffusive attack from aggressive agents, such as chlorides (Biondini et al. 2004, 2014). The seismic capacity associated to prescribed limit states is assumed as functionality indicator and the corresponding resilience is evaluated over the structural lifetime.
The parameters of the recovery function are calibrated by means of a life-cycle cost analysis aimed at quantifying the economic demand of the resilience targets required by stakeholders. To this purpose, an objective function related to the cost of the recovery process is formulated by taking into account both the direct cost of the repair interventions and the indirect economic loss due to the bridge outage.
The methodology is applied to a four-span continuous concrete bridge with box cross-section piers exposed to corrosion. The results show (a) that the detrimental effects of structural deterioration may affect the cost-effectiveness of the recovery process, leading over time to a significant increase of the recovery costs, and (b) a significant dependency of the optimal recovery profile on the time of occurrence of the seismic event.
