Multi-hazard fragility modeling framework for bridges with shallow foundations subjected to earthquake, scour, and vehicular loading

This study aims to advance knowledge on multi-hazard damage to shallow foundation bridges subjected to simultaneous scour, earthquake, and vehicular loads. While most water-crossing bridges have deep foundations, still, a significant number of water-crossing bridges have shallow foundations. In addition, there is limited research focusing on damage assessment of bridges with shallow foundations under multi-hazard scenarios. Therefore, this study proposes a probabilistic multi-hazard damage assessment framework for bridges with shallow foundations exposed to seismic, scour, and vehicular loadings. The proposed framework includes steps for hazard modeling, multi-hazard finite element modeling, non-linear time history analysis, and multi-hazard fragility modeling, and it was showcased on Chemin des Dalles Bridge, which is a typical bridge located in the Province of Quebec in Canada. Demand and fragility models parameterized on hazard and soil parameters were developed for the bridge components and a system fragility model was also developed using a series system assumption. The results from the analysis of these damage and fragility models indicated that scour notably increases component- and bridge-level response in typical shallow foundation bridges. However, until the scour depth is lower than the foundation height, the increased damage does not impose a significant threat to the bridge's safety. It was observed that earthquakes had the highest influence on the bridge components' response followed by scour and vehicular loads. Overall, the proposed framework can be used to facilitate policy-making toward informed bridge maintenance and retrofitting to aid in disaster mitigation planning and emergency response.