Enhancing a Three-Mass Vehicle Model with Wheel-Size Effect for Scanning Bridge Frequencies

An advanced miniature vehicle model is proposed by incorporating size of two wheels in a three-mass vehicle model to consider the offset of contact points due to the presence of pavement irregularity. In this proposed vehicle-bridge system, each wheel has its own dimension in addition to the mass related to the degree-of-freedom while it is assumed to be rigid. In the theoretical formulation, the real contact points and contact displacements turn to be unknown parameters. As such, a numerical framework is established by proposing a procedure in the time integration scheme to determine these parameters and deriving explicit coding structure to locate the two wheels on the bridge during simulation. The parametric study investigates the size effect of wheels, effect of vehicle damping, and pitching effect as a result of wheel size on the identification of frequencies. The results show that using larger wheels leads to smaller dynamic responses of the bridge and smaller vertical responses of the vehicle by the present vehicle model. Furthermore, higher accuracy is observed in the proposed vehicle model in comparison with the traditional three-mass vehicle model. The first three bridge frequencies can be identified distinctly under the most severe pavement irregularity.