Probabilistic structural performance evaluation of concrete slab bridge system subjected to scour and earthquake

Bridges are consistently subjected to various hazards throughout their expected lifespan while being subjected to constant use as a vital component of the national transportation network. Scour effects around the abutments and pier columns are one of the most common causes of bridge damage in the United States. Therefore, a multi-hazard analysis is necessary to evaluate if the bridges are capable of resisting scour and seismic loadings. This is of high importance as several earthquake-prone states regularly undergo flooding where extreme scour depths have been found. The current study employs non-linear time history analysis using 30 synthetic ground motions applied to a 3D analytical bridge model to simulate the responses of the combined effects of an earthquake and scour. The soil-structure interaction behaviors are taken into account using soil springs underneath the foundations in the model. To quantify probabilistic performance results, analytical fragility analysis is conducted to compute the probability of exceeding predetermined damage states. Comparisons are made between various levels of scour. Results indicate that as scour increases the response of bridge components increase, meaning the bridge becomes more fragile, specifically an increase in scour depths made the columns the most susceptible component at all damage levels. As scour increases, PGA required to achieve 50% exceedance probability were about two or three times lower for each damage state compared to the zero scour case.