Abstract Summary
There are currently no evidence-based regulations to set appropriate speed limits or enforce the closure of road bridges under strong crosswinds in Norway. To provide a scientific basis for future regulations, a test vehicle has been equipped with an anemometer, global navigation satellite system and inertial measurement unit and has been driven across several bridges under extreme crosswinds. The collected data describes the resultant vehicle-driver response to crosswind perturbations. The most significant values of lateral acceleration and yaw rate have been observed in response to easily identifiable gusts created in the wakes of bridge towers. The spatial periods of these significant gusts typically lie in the range 2 to 20 vehicle lengths, which has previously been identified as a range that is critical to vehicle crosswind sensitivity. Additionally, at the typical Norwegian speed limit of 80 kph, these spatial periods translate to frequencies that lie in the range 0.5 to 2 Hz, which has previously been identified as a range in which drivers are likely to amplify the handling response to perturbations (as opposed to attenuation below 0.5 Hz and a neutral effect above 2 Hz). Identifiable gusts of other dimensions/frequency have been observed outside these ranges as well and the resultant responses are of a much lower amplitude. Concrete empirical evidence is therefore presented to support the theory on critical gust dimensions/frequency for vehicle handling stability. A force identification method is proposed that allows the transient aerodynamic loads to be identified such that the contribution of the driver to unstable handling response can be better characterised.
