Seismic response analysis of a coupled vehicle - Bridge system

Traditionally, the traffic and the seismic dynamics have been considered independently when analyzing the seismic response of bridges. Given the ever increasing traffic volume though, vehicles are more likely to encounter an earthquake while crossing a bridge. Hence, there is a growing need to examine the dynamic vehicle-bridge interaction (VBI) under the simultaneous action of seismic ground motions. This study presents an original framework to analyze the seismic response of a coupled vehicle-bridge system during earthquake excitation. The examined dynamical system consists of the vehicle subsystem and the bridge subsystem. The two subsystems are coupled through the contact forces between the vehicle wheels and the bridge. The bridge subsystem is simulated with the finite element method, while the truck vehicles are modelled as rigid body assemblies. The proposed approach relies on the calculation of the coupling contact forces, and results in a system of global equations which provides the response of both the bridge and the vehicle simultaneously. A pilot application of the proposed scheme to a realistic case of (highway) bridge - (truck) vehicles interaction is presented. In this context, the study brings forward new problems encountered when analyzing the seismic response of interacting vehicle-bridge systems. Specifically, the paper underlines the need to consider different positions of the vehicle/s (on the bridge) during earthquake shaking, and highlights the importance of selecting representative parameters for the speed, the number and type of vehicles, which should reflect the site-specific traffic characteristics.