Field measurements and wind tunnel investigation of wind characteristics at a bridge site in a Y-shaped valley

Abstract

It is essential in a bridge design to study the wind parameters at the bridge site, particularly in a complex mountain area where the wind characteristics vary from location to location. The aim of this paper is to study the wind characteristics in a Y-shaped valley in mountainous terrain, the site of a proposed long-span bridge. Data recorded continuously for almost two years by a Doppler Sodar observation system installed at the bridge site was analysed. The results show that the terrain-induced effect plays a significant role in the wind direction variation and there are regular changes in characteristics depending on the direction. To supplement the full-scale measurements, wind tunnel tests were also carried out using a high-precision terrain model at a scale of 1:1500. Vertical profiles of velocity and turbulence at key points along the bridge, and the lateral profile along the bridge axis were studied. The results from the different test directions showed the influence of the incoming flow field particularly shielding and channelling effects which contribute to wind deceleration and acceleration at the bridge location respectively. Furthermore, the speed-up of the valley and mountaintop is evident and there is greater acceleration at the mountaintop.