Design loads and integrated performance metrics for highway bridges impacted by heavy vehicles

Current prescriptive design provisions adopt a constant impact design load to address vehicular collisions to bridge piers. This practice can account for neither the vehicle characteristics nor the pier’s structural properties, which may render the existing highway bridges vulnerable to accidental heavy vehicle collisions. To address this limitation, the first objective of this article is to develop a predictive model to efficiently link the impact design load with influential structural and vehicular parameters. An essential step to achieve this objective is to use validated finite element modelling approaches to obtain the impact force-time history response for vehicle-bridge collision events with varying structural and vehicular characteristics. Statistical techniques are employed for optimal model determination. As an alternative to the prescriptive design, the performance-based approach features the ability to explicitly define structural collision safety and deliver efficient design solutions. Two complementary performance metrics (percentage loss of axial capacity and the ratio of the maximum relative displacement at the impact location to the pier height) are proposed to characterize collision-induced damage in an objective manner. The integration of these two metrics into collision performance assessment makes it possible to quantify the capacity of a bridge to resume its normal operation after collision incidents.