Static and dynamic nonlinear modelling of long-span cable-stayed bridges

he aim of the paper is to provide numerical evaluations of the static and dynamic behavior of long span cable stayed bridges. In particular, investigations are presented to evaluate, in the framework of a dynamic analysis, the behavior of cable stayed bridges when subjected to the action of moving loads. In addition, the nonlinear static behavior is analyzed with the purpose to evaluate the influence of the geometrically nonlinear effects on the instability phenomena affecting the bridge structure. In both cases, the basic formulation is developed by using a finite element approach, in which a refined schematization is adopted to analyze the interaction behavior between cable system, girder and pylons. The proposed model takes into account geometrical nonlinearities of girder, pylons and of the cable system, for which local vibrations of the stays are also considered. Sensitivity analyses are 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 bridge behavior. Parametric results, developed in the framework of nonlinear static analysis, are also presented to evaluate the effects produced by instability effect of the axial compression in the girder on the maximum load-carrying capacity of the bridge.