A Modified Bridge System method to characterize and decouple vehicle–bridge interaction

Abstract

This paper examines the effect of traversing vehicles on the vibration of the supporting bridge. It shows that the effect of vehicle–bridge interaction (VBI) on the mechanical system of the bridge breaks down into three constituent mechanisms: (a) an additional damping, (b) an additional stiffness, and (c) a modified loading term. The study characterizes these three mechanisms with explicit analytical expressions in the case of a single-degree of freedom (SDOF) vehicle–SDOF bridge system. The analysis reveals that the impedance ratio—defined as the ratio of the vehicle’s damping to the bridge’s mechanical impedance—is a dominant coupling parameter of VBI, in addition to the (well-known) vehicle-to-bridge stiffness ratio. Subsequently, the study proposes an original approach, namely the Modified Bridge System (MBS) method, to decouple the VBI problem when the stiffness ratio is small. The MBS approach solves a modified bridge system, independent of the traversing vehicle. Numerical applications on simply supported railway bridges show that the MBS method outperforms other decoupling approaches, such as the moving load approximation. At the same time, compared to the solution of the coupled vehicle–bridge system, the proposed MBS method is equally accurate but computationally more efficient. The paper also outlines limitations of the proposed approach related to the single-mode representation of both vehicle and bridge.