Study On The Dynamic Response Of Double-deck Steel Truss Bridge Under Moving Vehicles.

The wheel load is an important load for bridge structure, especially for the steel bridge, and live load makes up a large proportion in bridge designing; Thus, vehicle load has become an important control factor for steel bridge design, and the effect of vehicle bridge interaction is more prominent. During bridge designing, dynamic load is equivalently treated as static load by using "dynamic amplification factors"(DFA), which is a approximate metheology to calculate the dynamic response of bridge structure under moving vehicle. Hence the main problems regarding vehicle bridge coupling vibration is to study the impact factor of the structure.Bridge-vehicle coupling vibration does not normally lead to the major bridge failures, but the wheel loads often induce local vibration of bridge components and contribute to fatigue and surface wear. Since double steel truss bridge has strong extensity and complicated loading condition and all two layers are forced with the vehicle load, the bridge-vehicle coupling vibration is more obvious. This paper mainly focuses on the dynamic response of double-deck steel truss bridge under moving vehicles.In this paper, the vibration equations are induced by the generalized virtual work principle, and Newmark-βmethod is written in Matlab to slove the vehicular vibration equation. Meanwhile, the dynamic equilibrium equation of the bridge structure is solved by Ansys, and the displacement equation and the equation of the vehicle bridge interaction simultaneous up and bridge system are put forward to solve bridge-vehicle coupling vibration. Finally, this method is verified by a simple case. The study indicates that the above method is reliable.This paper studies the parametric analysis of roughness, bridge damping and the vehicle speed, and the numerical result suggests that:(1)road roughness is a significant factor for bridge-vehicle coupling vibration; Specifically, bridge-vehicle coupling vibration will become more intensive and the global and local effects of the bridge will have a greater impact with road roughness deteriorating, (2)the bars of steel truss bridge(the displacement, the rotation and the axial forces)response significantly reduce by the vehicle load with the high damping; (3)the vehicle speed and dynamic response functions of steel truss bridge do not show regular trend. (4)compared with the dynamic response of the whole bridge, load of single-deck will have a greater effects on local vibration of bridge components. Through the data analysis, the bridge dynamic amplification factor of different bridge parts and the sensitivity of the parameters are not the same during the bridge partial design, and should be local to the local dynamic amplification factor in order to describe the impact effect of the vehicle.