Motion Stability of Long‐Span Bridges under Gusty Winds

Abstract

The effects of spanwise wind‐velocity correlation and turbulence intensity on the coupled vertical‐torsional response of long‐span suspension bridges are studied. Turbulence is accounted for in the self‐excited loads that are expressed in terms of the indicial aerodynamic functions. Buffeting forces enter the stability calculations because they are related to the self‐excited loads through the common turbulence field. Assuming the wind‐turbulence terms to be Gaussian white‐noise processes, the coupled parametric‐type equations of motion are transformed into an Ito stochastic differential equation. Stationary response moments are obtained for both vertical and torsional displacements for different degrees of spanwise correlation and turbulence intensity. Motion instability is determined when responses become asymptotically unbounded. Higher turbulence leads to lower critical wind velocity for constant correlation, but less correlation results in higher critical velocity for constant turbulence. Higher turbulence leads to a more gradual transition from a stable to a unstable state.