Wind-Induced Asymmetry Torsional Divergence of Long-Span Bridges: Mechanism, Three-Dimensional and Turbulence Effects

Abstract

Flexible suspension bridges are susceptible to aerodynamic instability phenomena. In this paper, the torsional divergence is addressed in terms of underlying mechanism, 3D and turbulence effects. A 3D generalized analytical model is first established by reasonable simplification of the model. Comparisons among results from different models are performed. The mechanisms of symmetric and asymmetric torsional divergence are explored. Finally, the 3D and turbulence effects are investigated. The results show that the proposed 3D generalized model is feasible for estimating the critical wind speed of asymmetric torsional divergence, and its computational accuracy is higher than the method provided by the code. The effects of turbulence on torsional divergence are multifaceted: the buffeting response due to wind fluctuations can significantly reduce the aerostatic stability of the bridge, resulting in a much lower critical wind speed than that in a smooth flow; the threshold of divergence is ambiguous and the instability is intermittent; further, the left and right quarter span sections largely vibrate in opposite directions during asymmetric torsional divergence.