Downslope Gusty Wind Loading of Vehicles on Bridges

Abstract

Downslope crosswind bora gusts impacting vehicles represent a significant traffic safety issue, and vehicles on bridges are particularly vulnerable to such crosswinds. Wind tunnel experiments were carried out to investigate the effects of the vertical wind incidence angle and vehicle position on the resulting transient aerodynamic loads. When considering accident risk for the vehicle/infrastructure scenario investigated in this study, the higher risk for vehicles exists at lower vertical wind incidence angles up to 30° and closer to the upwind edge of the bridge deck with respect to steady aerodynamic loads. Shed vortices and wind gusting determined the unsteady aerodynamic loading of a vehicle on the bridge. Effects of shed vortices decreased at larger vertical wind incidence angles, with the wind gusts driving the unsteady aerodynamic loads. Difficulties associated with vehicle maneuvering and stability in the upwind traffic lane in terms of unsteady aerodynamic loading are expected to occur at the wind gusting frequency. Dynamic loading of vehicles in the downwind traffic lanes was due to shed vortices as a consequence of the bridge architecture and aerodynamic form of the vehicle.