Abstract: Test on the mechanical properties of bridges under the moving loads of vehicles is one of the important aspects of bridge dynamic test. Considering the complex influence of the pavement roughness on the bridge dynamic test, this paper proposes a measuring technique of the crosstie vehicle′s bumping test which is aimed to suppress the pavement roughness. Firstly, based on the vehicle -bridge coupled vibration theory, the vibration equation is solved by numerical calculation method. The paper studies the factors that have significant influence on the bridge′s impact coefficient, such as the vehicle velocity and pavement roughness. Secondly, a vehicle bridge vibration system model under the condition of crosstie vehicle′s bumping is established. The calculation result shows the major factors which influence the bridge′s impact coefficient are vehicle speed and the height of vehicle′s bumping and pavement roughness. Analysis shows that the bridge′s impact coefficient follows Gaussian distribution on the same grade pavement, bringing significant changes on different grade pavements; the pavement roughness can be ignored when the vehicle speed and the height of vehicle′s bumping meet a certain condition. An engineering example shows that this model can accurately reflect the response of the simply supported beam under the impact load of the vehicle, and can be used to calculate the bridge′ s impact coefficient.

Key words: bridge inspection, vehicle-bridge coupling, pavement roughness, vehicle′s bumping, impact coefficient