Static And Dynamic Properties Of The Ballastless Track On Long-span Plate-truss Cable-stayed Bridge

With the vigorous development of high-speed railway, more and more long-span plate-truss cable-stayed bridges have been or will be built across the Yangtze river or Yellow River. The ballastless track has been widely used on high-speed railway both at home and abroad in recent years, due to its technical characteristics like good structure constancy, stability, durability, less maintenance and economy. Static matching and dynamic adaption problems occur under train loads between the long-span plate-truss cable-stayed bridge and the ballastless track, due to their structural characteristics. However, studies on static and dynamic properties of the long-span plate-truss cable-stayed bridge with ballastless track, are rare both at home and abroad. Therefore, it is necessary to carry out research on these.This article studied static and dynamic properties of long-span plate-truss cable-stayed bridges with ballastless track, using finite element software ANSYS as the static calculation tool, and explicit dynamic analysis program LS-DYNA as the dynamic calculation tool, and LS-PREPOST3.2as the post-processing dynamic calculation tool.Firstly, established a three-inter beam-solid-shell local refined ANSYS model, regarding the plate-truss cable-stayed bridge and ballastless track as a system to study its static properties.Secondly, set up five track bed slab and support layer finite element models arranged in different ways. And analysis and compared orbits’integral stiffness and their change law within the truss internodes under different arrangements of track bed slabs, and discussed the differences of orbits’integral stiffness between long-span plate-truss cable-stayed bridgess with ballastless track and that on normal lines and concrete simply-supported bridges with ballastless track, then found out the characteristics of integral stiffness of the long-span plate-truss cable-stayed bridges with ballastless track.Using Two methods, that is, nonlinear spring element and contact element, to simulate the contact relationship between elastic damping cushion layer and track bed slab, and calculate the possibility of partial void, void volume and void range at different places within the truss internodes. Then, compared the void volume which is in different track bed slab layout conditions and which is in different elastic damping cushion stiffness combination cases. At the same time, put forward some optimization schemes to reduce void volume.Thirdly, using the explicit dynamic analysis method, established the vertical vibration model of the local deck system of train-ballastless track-long-span plate-truss cable-stayed bridge, and taking trains, railways and bridges as a coupled vibration system of interaction and coordination.Finally, analyzed the distribution and features of local vibration of road track bed slab and bridge panel within the internodes, and studied the necessarity of setting the support layer on long-span plate-truss cable-stayed bridges, then compared the influence of different train speeds on the vibration of bridge deck and the track bed slab, and optimized the stiffness of elastic damping cushion layer through time domain analysis and frequency domain analysis.The static analysis results showed that, uneven stiffness of the long-span plate-truss cable-stayed bridge orthotropic bridge deck had some influence on orbits’integral stiffness, and the structural discontinuity of ballastless track significantly affected the uniformity of orbits’integral stiffness in vertical position. The design of long-span plate-truss cable-stayed bridge with ballastless track should take full account of the impact of the bridge structure, in order to ensure the matching of track structure and bridge structure. It’s possible that there may exist void between road track bed slab across the main beams at the board terminal region and the support layer. The maximum void volume was related to load position and track bed slab layout form, so we should give priority to the layout that track bed slabs were disconnected at the main beams. The layout of elastic damping cushion layers using small stiffness on both ends and big stiffness on the middle can obviously reduce void volume and void range.The Dynamic analysis results show that the long-span plate-truss cable-stayed bridge floor system with ballastless track adopted in longitudinal beam system, girder set between transverse spacing can reduce the local vibration of bridge deck. Setting support layer significantly reduced the acceleration response in the areas beneath the track structure, between the longitudinal beam bridge deck and on the edge of the track bed slab juncture. The peak value of vertical acceleration of the bridge panel at the bottom of track structure increases with the increase of train speed. At high train design speed, the length of the track bed slab should match with intemodes length, avoiding the case that track bed slab across the main beam. Based on the analysis of time domain and frequency domain, the stiffness of elastic vibration isolation cushion should be preferred0.05N/mm3This article has the certain reference values on further studies about the static and dynamic properties of long-span plate-truss cable-stayed bridge with ballastless track. Besides, this paper also provides basis for the future design of long-span steel bridge with ballastless track.