Dynamic Response Analysis Of The 87-Type Railway Steel Beams For Rush-repair (64m, Deck Truss)

The 87-type military railway beams for rush-repair are a type of long span military beams. They can be assembled quickly and used repeatedly. In order to better meet future requirements of warfare logistics and peacetime emergencies, a research team has been founded to improve their performance. The problems of the through and the half-through can be solved easily; however, the deck truss, with best comprehensive tactics but low lateral stiffness, are difficult to meet high requirement and need to be emphasisly analyzed.Dynamic analysis is carried out on the 64 m span deck truss. Seven 3D FEM models, with different ends and different designs, are established using beam element by ANSYS. By inputting sections, defining key points and section offsets, the direction and position of the member sections are simulated; and by releasing part of the node degrees, the connection of the members is simulated. Modal analysis is then performed to determine the free vibration characteristics. A model by substructure method is also established to study the application of substructure in the analysis of free vibration of 87-type steel beams. Vehicle-bridge dynamic analysis is then conducted using existed program. Finally, the influences on vehicle-bridge dynamic response with different beam ends, different reinforced designs, different speeds and loads are analyzed.Through calculation and analysis, the conclusions are as follows. Firstly, lateral stiffness of the final design is relatively low; the influences on vehicle-bridge dynamic response between different ends are very little; four different reinforced designs can significantly improve the lateral stiffness, but have little influence on vehicle dynamic response, and has little effect on increasing speed limit. Secondly, for different speeds, it can be seen that the resonance speed of four reinforced designs is about 45 km/h and the suggested speed limit is 40 km/h, which can be provided for design reference. Thirdly, for different loads, when the train running through reinforced design (1) at 40 km/h, the dynamic response of heavy-loaded vehicle is all below limits, but the derailment coefficient and offload reduction rate of unloaded vehicle and mixed unit train are much greater, which have seriously exceeded the limits, with the risk of derailment.