Identification of Dynamic Vehicular Axle Loads: Theory and Simulations

This paper presents a new method of identifying dynamic vehicular axle loads by directly using bridge measurements. To demonstrate how the proposed methodology works out, vehicle-bridge coupling equations are first established for numerical simulations. The developed vehicle-bridge coupled system contains only the modal properties of the bridge and the physical parameters of the vehicle. Using the superposition principle and influence surface concept, the dynamic interaction forces (i.e. the dynamic axle loads) can then be identified from the measured bridge responses. A series of simulations are carried out in which the effects of various factors such as bridge inertia force, measurement station, vehicle speed, traveling route, number of vehicles, road surface condition, and noise level have been investigated. The identified results show that the proposed method is able to identify dynamic axle loads with good accuracy, which can serve as a basis for dynamic bridge-weigh-in-motion. This paper also serves as a theoretical base for the companion paper in which the proposed method is applied to identify the dynamic axle loads of a real truck on an existing bridge.