A Reliability Based Crack Propagation Model for Reinforced Concrete Bridge Piers Subject to Vehicle Impact

Bridges play a critical role in transportation infrastructure networks. As such, their ability to withstand hazardous loading scenarios is essential. The response of bridges and specifically of bridge piers to hazardous loading scenarios such as earthquake and blast have received significant attention. However, their behavior under vehicle impact has received less attention. This is significant due to the fact that the frequency of occurrence for vehicular impact is appreciably higher than that of earthquake and blast. Of larger significance however is the fact that bridge piers that have experienced impact loading may have reduced capacities to withstand secondary hazardous loadings. This multi-hazard loading scenario of bridge piers is ideally suited for reliability-based risk analysis methods for study; however, very few such studies exist. In this research, a reliability-based model is used to determine the crack propagation in circular reinforced concrete bridge piers at different strain rates. Crack propagation is an important characteristic for structural health and ability to withstand future loading. However, in the case of vehicular impact, only the deformation of the pier is typically taken into account for determine post impact serviceability. In the model, quasi-static to dynamic strain rates are considered for steel while only dynamic strain rates are considered for concrete. Using Monte Carlo simulation, crack propagation rates for both Grade 60 and Grade 80 reinforcing steel are developed. The Hasofer-Lind reliability method is then used to determine the subsequent reliability of the piers post-impact. Models representing the dynamic reliability indices validating limit state equations show persuasive and practical trends. Furthermore, the model can serve as a design tool in predicting serviceability as well as analyzing design scenarios in an economic and practical way.