Dynamic impact analysis of long span cable-stayed bridges under moving loads

The aim of this paper is to investigate the dynamic response of long span cable-stayed bridges subjected to moving loads. The analysis is based on a continuum model of the bridge, in which the stay spacing is assumed to be small in comparison with the whole bridge length. As a consequence, the interaction forces between the girder, towers and cable system are described by means of continuous distributed functions. A direct integration method to solve the governing equilibrium equations has been utilized and numerical results, in the dimensionless context, have been proposed to quantify the dynamic impact factors for displacement and stress variables. Moreover, in order to evaluate, numerically, the influence of coupling effects between bridge deformations and moving loads, the analysis focuses attention on the usually neglected non-standard terms related to both centripetal and Coriolis forces. Finally, results are presented with respect to eccentric loads, which introduce both flexural and torsional deformation modes. Sensitivity analyses have been proposed in terms of dynamic impact factors, emphasizing the effects produced by the external mass of the moving system and the influence of both “A” and “H” shaped tower typologies on the dynamic behaviour of the bridge.