MOTION STABILITY OF LONG-SPAN BRIDGES UNDER GUSTY WINDS.

The effects of spanwise wind-velocity correlation and turbulence intensity on the coupled vertical-torsional response of long-span suspension bridges are studied. 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.