Stochastic Stability of Lateral-Torsional Motion of Slender Bridges Under Turbulent Wind

Abstract

The paper presents a simulation-based approach to investigate the stability of lateral-torsional motion of slender suspension bridges under stochastic wind turbulence. The bridge motion is represented by a linear, two degrees of freedom oscillator. Stochastic turbulence in wind velocity is considered in the form of a periodic excitation with random phase modulation. The stability condition refers to the asymptotic sample stability, for which the necessary and sufficient condition is that the largest Lyapunov exponent be negative. Monte-Carlo simulation is performed to evaluate the largest Lyapunov exponent, and stochastic differential equations of motion are integrated using Euler’s scheme. In contrast with some approximations reported in the literature, the turbulence intensity is shown to have a destabilizing effect on the bridge stability in a sense that an increase in the intensity decreases the critical mean wind velocity below the deterministic flutter velocity.