Dynamic Simulation of a Long-Span Bridge-Traffic System Subjected to Combined Service and Extreme Loads

Long-span bridges support busy traffic and experience considerable wind loads on the bridge decks nearly every day. In addition to these two major service loads, some extreme loads such as earthquake, vehicle collision, or blast may also occur on the bridges simultaneously. Excessive dynamic responses of the bridge under extreme and service loads may not only cause local member damage, serviceability issues, or even global failure of the bridge structure, but also traffic safety concern on moving vehicles. A general simulation platform is established to investigate the dynamic performance of the bridge-traffic system under multiple service and extreme loads. The fully coupled bridge-traffic interaction model is developed by coupling the mode-based bridge model and all individual moving vehicles of the simulated stochastic traffic flow considering excitations from bridge deck roughness and other external dynamic loads. Through the established simulation platform, the global dynamic responses of the bridge and each individual vehicle subjected to various service and extreme loads can be rationally predicted in the time domain. As a demonstration, the proposed strategy is applied to a bridge-traffic system consisting of a prototype long-span cable-stayed bridge and stochastic traffic subjected to the excitations of road surface roughness, turbulent wind, and seismic ground motions. The vertical and lateral responses for the bridge and a representative vehicle are obtained and analyzed in different loading scenarios. Some observations are made based on the performance of both the prototype bridge and representative vehicle subjected to multiple dynamic loads.