Vehicle-induced Local Vibration Performance Of Bridge Deck System With Unballasted Track And Elastic Damping Cushion Optimization For Long-span Steel-Truss Cable-stayed Bridges

With the rapid development of high-speed railway construction, vehicle will intensify the dynamic action on bridge and the impact is significant especially when the bridge span is large and the vehicle speed is high, so the local vibration performance of bridge deck system caused by the vehicle can’t be ignored. The number of long-span steel-truss cable-stayed bridges in high-speed railway construction is gradually increasing local vibration of the deck system caused by the vehicle can’t be ignored, the long-span steel-truss cable-stayed bridges is taken as research object, local vibration law and spectral characteristics of bridge deck system with three different stiffness cushions of ballastless track are analyzed by taking vehicle-track-bridge coupling vibration analysis method based on dynamic analysis program LS—DYNA in this paper. Based on the studies, the dynamic response of the deck system is reduced by optimizing the elastic damping cushion, The main contents are as follows:Firstly, structural parameters of vehicle, unballasted track, long-span steel-truss cable-stayed bridges are introduced systematically, Presumptions and simplified method of vertical dynamics of vehicles-unballasted track-long-span steel-truss cable-stayed bridge are proposed, the vertical dynamic model is established by equivalent elastic cushion stiffness, linearizing wheel-rail contact and analogizing track irregularity based on dynamic analysis program LS—DYNA.Secondly, explicit dynamics calculation method and central difference theory are taken in this paper, based on vehicle-track-bridge coupling vibration analysis method, the local vibration characteristics of slab, seating plates and bridge deck under three elastic stiffness of the damping cushion are analyzed through the use of CRH2vehicle model at a speed of200km/h. RMS values of acceleration and displacement at different locations of the deck system are obtained, and thus the local acceleration and displacement at different locations are analyzed.Finally, the distributions of the spectrum principles of structure below the track under three elastic stiffness of the damping cushion are studied by spectrum analysis. By combining different stiffness of the elastic damping cushion and optimizing the arrangement of unballasted track elastic damping cushion, the dynamic response of the deck system under the track is reduced and the optimal combination of unballasted track elastic damping layer is got. The main results indicate that:1) By comparing the variation principles of RMS value of vertical acceleration and displacement at different locations between the deck department, it is found that the variation principles of RMS value of vertical acceleration and displacement at different locations are similar under different elastic damping stiffness; the response of vertical acceleration RMS value becomes smaller at different locations of deck system when elastic stiffness of the damping cushion is smaller; elastic damping cushion has a greater impact on the displacement of superstructure (slab), the larger the damping cushion stiffness is, the smaller the displacement is. In contrast with the slab, the elastic damping cushion has a smaller impact on the substructure (seating plates and bridge deck), the larger the damping cushion stiffness is, the larger the displacement is.2) Spectrum analysis shows that:in the whole frequency range of0~500Hz, spectral characteristics of acceleration of the deck system are basically same under three elastic stiffness of the damping cushion, distribution of dominant frequency is in the low-frequency part (11.9Hz) and high-frequency part (180Hz~500Hz), vibration will be intensified within the frequency range of180~500Hz,the main peak frequency are11.9Hz and181.9Hz.low stiffness elastic damping cushion (0.05N/mm3) causes minimal vibration energy of deck system within the low frequency (11.9Hz); vibration energy caused by high stiffness elastic damping cushion (0.15N/mm3) is small in the high frequency part (180Hz~500Hz).3) Impact of different combinations of the elastic stiffness of the damping cushion on the frequency distribution of the deck system is little, but the impact on energy distribution is significant under different frequency; based on vibration analysis of slab, seating plates and bridge deck, damping effect is much better when elastic damping cushion stiffness is high at the both sides while it is low in the middle in contrast with the one the elastic damping cushion stiffness is isotropic, effect is significant especially on the slab.