On the aerostatic divergence of suspension bridges: A cable-length-based criterion for the stiffness degradation. (January 2015)

• Record Type: Journal Article
• Authors: Zhang, Z.T.; Ge, Y.J.; Chen, Z.Q.
• Is Part Of: Journal of fluids and structures. Volume 52(2015:Jan.)
• Page Start: 118
• Page End: 129
• Publication Date: 2015-01
• Subjects: Suspension bridge -- Aerodynamic -- Divergence -- Stiffness degradation -- Cable length; Fluid-structure interaction -- Periodicals; Fluid mechanics -- Periodicals; Structural dynamics -- Periodicals; Structural analysis (Engineering) -- Periodicals; 620.106
• DOI: 10.1016/j.jfluidstructs.2014.10.005
• Languages: English
• ISSNs: 0889-9746

Abstract

Abstract: Motions of a suspension bridge immersed in turbulent wind flows, including both mean and stochastic, can under certain conditions lead to the degradation of the structure׳s torsional stiffness and ensuing aerodynamic torsional divergence (ATD). It is the incompressibility of the main cables that determines their effectiveness as supporting members be limited in a tension state, and dropping out of either one cable from a tension state could result in the vanish of the torsional stiffness contributed by the whole cable system. Although the physical conception is quite explicit, evaluation of the critical threshold of ATD of a suspension bridge, when experiencing stochastic aerodynamic responses, can be complicated by the deformations of the towers, the lateral oscillations of the deck and cables, and other high-order modes participating in the vibration. In view of this, a criterion based on the tracking of the length of the main cables is presented in this study. It is shown that, with the numerical example, the advent of ATD, the degradation of the system׳s stiffness, as well as some striking post-ATD behaviors, can be well explained with the proposed model by tracking the cable lengths. Highlights: The mechanism of torsional stiffness degradation of suspension bridges is presented. Logic relations among three critical wind speeds are analyzed. A criterion based on the tracking of the main cable lengths is brought forward. The issue of the influences of the bridge–tower deformations, lateral structural oscillations, and higher-order motions, etc., can be circumvented by the cable-length-based criterion. Numerical example verifies the effectiveness of the method presented.