Free vibrations of hybrid cable networks with external dampers and pretensioned cross-ties

Abstract

This study proposes a refined model, by taking the cable sag and cross-tie pretension into account, to investigate the effects of cross-ties on dynamics of a hybrid cable network system. Based on a typical hybrid system, i.e., two cables with one pretensioned cross-tie and two near-anchorage external dampers, the system characteristic equation is formulated via the complex modal analysis method, and the influence of cross-tie pretension on the dynamics of the system is discussed. Then, simplified analytical methods, based on the taut-string model, are presented and compared with the refined analysis method. The analytical results indicate that the effect of cross-tie pretension on the dynamic characteristics of hybrid systems is closely related to anchorage form of the cross-tie. When the cross-tie is not connected to the ground, it could apparently change the dynamic characteristics of the system due to its pretension. Nevertheless, when the cross-tie is connected to the ground, the cross-tie pretension marginally influences the system dynamics. The proposed simplified analytical method, which considers the cable tension change caused by cross-tie pretension, is shown to be accurate as compared with the refined analytical method except for the first two modes of the system. However, completely neglecting cable sag and cross-tie pretension in dynamic analyses of hybrid cable networks leads to considerable inaccuracies of the estimated system frequencies and modal damping ratios.