Safe speeds for a heavy articulated vehicle when passing a floating bridge tower under crosswind

Abstract

This paper recommends safe speeds for a heavy articulated vehicle when passing by Bjørnafjorden floating bridge tower under two constant crosswind speeds (65 km/h and 100 km/h). The analysis is based on the tractor-semitrailer (TS) model with fifth-wheel (FW) coupling in roll and free in yaw. Comparison of safe speeds assessments has been made with two TS models differ in FW coupling. Aerodynamic forces and moments for TS models as function of their position relative to the bridge tower and time were computed using Computational Fluid Dynamics (CFD) simulations. For TS model coupled in roll and free in yaw, no rollover risk is noticeable for both crosswind excitations. For TS model free in roll and in yaw, roll-over risk is noticeable at lower vehicle velocities (at 36 km/h and 54 km/h). TS with rigid connection in FW stays in the traffic lane for every considered vehicle velocity. TS model which is roll and yaw moment free in the FW overestimates rollover risk assessment at lower vehicle velocities. TS model with rigid connection in the FW underestimates traffic lane departure assessment at higher vehicle velocity. Appropriate mathematical modelling of a heavy articulated vehicle that considers tractor and semitrailer units as two separate bodies coupled in roll and free in yaw is of importance for accurately assessing safe speeds when a vehicle passing by the bridge tower.

Keywords

• Bjørnafjorden
• Aerodynamic loads
• Rollover risk
• Traffic lane departure
• Tractor-semitrailer
• Vehicle modelling