Numerical simulation of the aeroelastic response of bridge structures including instabilities

Abstract

This paper presents a finite element model for the time-domain simulation of light-weight bridges under wind loading. In particular, aeroelastic effects are taken into account which allow the detection of flutter instabilities. It is assumed that the overall aeroelastic behaviour can be described by cross-section properties. Their determination is not part of the numerical model, instead they are assumed to have been experimentally determined before; in the design phase this is usually done by section testing in a boundary layer wind tunnel. The paper concentrates on flutter in smooth flow for which a description of the self-excited forces by flutter derivatives is chosen. These aeroelastic forces are introduced into a general 3D finite element code which in principle permits the modelling of the structure with arbitrary accuracy, allowing also structural nonlinearities, though that aspect is not pursued further here. The critical wind speed is calculated by numerical experiments in the time domain where wind speed and flutter frequency are modified until a contradiction-free solution is found. An extensive numerical study, studying in particular the effects of dampers on the flutter vulnerability, demonstrates the capabilities of the proposed model. The usefulness of this approach lies in the combination of relatively simple 2D measurements with advanced 3D computational methods. These are free from the constraints of the model laws so that, depending on the quality of the FE model, any number of mode shapes can be accurately captured, which would be extremely difficult to achieve in a fully aeroelastic 3D model test.