AN EFFICIENT ALGORITHM FOR DYNAMIC ANALYSIS OF BRIDGES UNDER MOVING VEHICLES USING A COUPLED MODAL AND PHYSICAL COMPONENTS APPROACH

A general and efficient method is proposed for the resolution of the d ynamic interaction problem between a bridge, discretized by a three-di mensional finite element model, and a dynamic system of vehicles runni ng at a prescribed speed. The resolution is easily performed with a st ep-by-step solution technique using the central difference scheme to s olve the coupled equation system. This leads to a modified mass matrix called a pseudo-static matrix, for which its inverse is known at each time step without any numerical effort. The method uses a modal super position technique for the bridge components. The coupled system vecto rs contain both physical and modal components. The physical components are the degrees of freedom of a vehicle modelled as linear discrete m ass-spring-damper systems. The modal components are the degrees of fre edom of a linear finite element model of the bridge. In this context, the resolution of the eigenvalue problem for the bridge is indispensab le. The elimination of the interaction forces between the two systems (bridge and vehicles) gives a unique coupled system (supersystem) cont aining the modal and physical components. In this study, we duly consi der the bridge pavement as a random irregularity surface. The comparis on between this study and the uncoupled iterative method is performed. (C) 1998 Academic Press Limited.