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Abstract

The compounding effect of seismicity, exposure to corrosion, and climate change in regions such as North America pose significant challenges for bridge design engineers, as the multi-hazards impact on the performance-based design of bridges remains underexplored. This research provided a performance-based assessment approach for existing bridges in multi-hazard environments, aiming to improve their fragility and minimize their lifecycle costs (LCC). Initially, a screening framework for deficient concrete bridge piers was proposed, incorporating criteria beyond the traditional condition index, such as location, population density, and other socio-economic impacts. An indicator called the Bridge Screening Index (BSI) was proposed to prioritize deficient bridges. Subsequently, a probabilistic seismic demand assessment (PSDA) in the form of temporal incremental dynamic analysis (IDA) was employed to formulate predictive expressions for the drift demand of reinforced concrete (RC) columns across various environments and under different climate change scenarios. Analysis indicated that the future effect of corrosion varies depending on the excitation level of the earthquake. Moreover, The impact of exposure conditions, such as marine atmospheric and marine splash zones, on the response of RC columns is comparable, while the effect of de-icing salt spray is significantly greater. For instance, after 120 years at a PGA of 1.25g, drift demand increases by 52.3% in marine atmospheric zones, 71.8% in marine splash zones, and 215.2% in de-icing salt spray zones. The step following PSDA is fragility analysis. This study developed novel time-based fragility tools for RC bridge columns, accounting for the cyclic enhancement in seismic fragility due to routine maintenance actions. Finally, an optimization model, using mixed-integer linear programming, was employed to minimize the operational LCC while maintaining the fragility within a user-defined upper limit. Finally, A case study was used to illustrate the proposed approach. With this optimization model, it was possible to decrease the LCC of two existing bridge piers, in two different environments: marine atmospheric and marine splash, by 38.4% and 35%, respectively. Overall, the results of this study indicate that reducing the maintenance interval between future activities is beneficial only up to a certain limit, which varies depending on the seismic risk and environmental exposure.