In‐plane dynamic behaviors of two‐cable networks with a pretensioned cross‐tie

Abstract

Connecting cables with cross-ties to form a cable network is a viable solution for suppressing cable vibrations. The cross-ties need to be pretensioned to prevent them from being completely released and suffering from shocks during cable vibrations. However, most existing studies have ignored the cross-tie pretension for dynamic analysis. Therefore, this study investigates the effects of cross-tie pretension on in-plane dynamics of a cable network. The effect on cable tension forces and static profiles is first studied. Complex modal analysis is then performed to formulate the characteristic equation of a cable network considering small cable sag, cross-tie stiffness, and pretension, and dynamics of a two-cable network is discussed in detail. It is found that when the cross-tie is not connected to the bridge deck, the cross-tie could reduce the system frequency due to its pretension, particularly in modes where the vibration of the cable whose tension is reduced by the cross-tie pretension dominates. Nevertheless, when the cross-tie is connected to the ground, it seems to always increase system frequencies. Furthermore, simplified analyses are conducted based on the taut-string model of the cables considering cable tension force modified by the cross-tie pretension while ignoring cable sag induced by either gravity or cross-tie pretension. A comparison of the results indicates that the cross-tie pretension affects the system dynamics mainly through modifying cable tension while the introduced change in cable profile only has limited influences on the system lower modes. This study demonstrates the importance of cross-tie pretension in dynamics of cable networks.