Safety analysis of a road vehicle passing by a bridge tower under crosswinds

As a road vehicle passes by a bridge tower under crosswinds, the vehicle will be briefly shielded from the crosswinds by the tower within a very short period of time, but when it gets out of the tower it enters a sharp-edged crosswind gust with the obvious danger of overturning or course deviation. The accident vehicle/wind speed associated with such an event is currently estimated by applying a 0.5 s sudden step crosswind gust to the vehicle to see if overturning, sideslip or rotation accident will occur. In reality, a much more complicated wind condition than a sudden crosswind gust is confronted by the vehicle when it passes by a bridge tower. This study aims at a more accurate safety analysis of a road vehicle passing by a bridge tower under crosswinds. Varying wind loads experienced by a road vehicle passing by a bridge tower are first formulized in terms of time-varying aerodynamic coefficients obtained from computational fluids dynamics. Varying wind loads are then enforced on the vehicle together with a coupled road vehicle-bridge-wind (RVBW) system. Safety analysis is finally performed to examine the behavior and safety of the vehicle. The results show that the rolling and lateral motions of the vehicle are influenced significantly by the tower and that the driver needs to take quick action with a high steer angle to keep the right course. The influence of the bridge dynamic response on the safety of a single vehicle passing by the tower under crosswinds is insignificant.