Probabilistic safety evaluation of a river bridge substructure against floods

摘要

Many factors affect the safety of a reinforced concrete river bridge, and some of these factors might have significant uncertainty that should be evaluated. This study focuses on a system reliability analysis of a reinforced concrete bridge, which is the most common type of river bridge in Taiwan. Specifically, non-linear behaviours of core/cover concrete and steel reinforcement in the substructure of a bridge are considered. Uncertainties of stream surface elevation, water velocity, local scour depth, soil property and record-to-record variations are included in the probabilistic model. The aforementioned parameters of six river geometries are incorporated into a Hydrologic Engineering Center-river analysis system (HEC-RAS) model to assess their impacts on the bridge safety. The effect of river geometry has not been studied thoroughly. Results shown here indicate that it plays an important role. Adopting Bayesian theory to consider the record-to-record uncertainty by combining historic and HEC simulation data is another innovative aspect of this study. Monte Carlo simulation is used to conduct the reliability analysis. The results obtained indicate that the proposed procedure for the bridge reliability analysis is consistent with expert engineering judgement and that the variation in scouring depth and river geometry are pertinent to bridge safety.