Dynamic analysis of cable-stayed bridges affected by accidental failure mechanisms under moving loads

The dynamic behavior of cable -stayed bridges subjected to moving loads and affected by anaccidental failure in the cable suspension system is investigated. The main aim of the paper is to quantify, numerically,the dynamic amplification factors of typical kinemat ic and stress design variables, by means of a parametric studydeveloped in terms of the structural characteristics of the bridge components. The bridge formulation is developed byusing a geometric nonlinear formulation, in which the effects of local vibrations of the stays and of large displacementsin the girder and the pylons are taken into account. Explicit time dependent damage laws, reproducing the failuremechanism in the cable system, are considered to investigate the influence of the failure mode characteristics on thedynamic bridge behavior. The analysis focuses attention on the influence of the inertial characteristics of the movingloads, by accounting coupling effects arising from the interaction between girder and moving system. Se nsitivityanalyses of typical design bridge variables are proposed. In particular, the effects produced by the moving systemcharacteristics, the tower typologies and the failure mode characteristics involved in the cable system are investigated.by means of comparisons between damaged and undamaged bridge configurations.