Experiments of aerodynamic admittances for moving vehicles on bridges

Abstract

Aerodynamic admittance is an important parameter for revealing the buffeting force on a vehicle. This paper is the first to present an experimental study on the admittances of moving vehicles under turbulence flow. The power spectrums of the wind velocity experienced by a moving point on the bridge and measured at a stationary point are investigated. The effects of wind velocity power spectrum types, vehicle motion states, and yaw angles on the aerodynamic admittance of a moving vehicle are evaluated, and a simple empirical equation is proposed to fit the aerodynamic admittance. The results indicate that the movement of the measured point has little effect on the vertical component spectrum, but a great effect on the longitudinal component spectrum. Moreover, the admittance defined by using the static wind velocity power spectrum will be underestimated at low frequencies. Static wind tunnel test will overestimate the admittance of the vehicle at low frequencies, and the peaks of the lift and side force admittances of the moving vehicle shift toward higher frequencies, and the value of the lift force admittance at low frequencies is sensitive to the moving speed.