Simulation of linear and non-linear propagation effects of a random turbulence field on bridge flutter instability

This paper presents the results of an analytical and numerical investigation on the implications associated with the propagation of an “uncertain” turbulence field on the aeroelastic stability of long-span bridges. Even though the influence of turbulence on flutter has received the attention of the wind engineering community in the recent past, an alternative formulation for simulating turbulence effects on flutter is proposed, in the general context of uncertainty and modeling error simulation. The coupled-mode flutter threshold, limited to the fundamental bending and torsional modes of a bridge, is estimated in the time domain by stochastic calculus techniques. A generalized modal correlation length is used to simulate turbulence modeling errors. Both linear and non-linear random propagation is investigated by means of stochastic stability. A numerical integration scheme is employed for the solution of the dynamic equations and to derive second-moment stability conditions for non-linear case. A set of simplified bridge examples is analyzed. Either a decrement or an increment in the critical velocity is observed for the non-linear random turbulence case, depending on the selected example. Nevertheless, this variation is usually small, of the order of a few percents in comparison with the “turbulence-free” scenario.