A Study Of The Construct And Layout Of Rail Expasion Joint

The technology of continuous welded rail is more and more perfect and mature, and it has got extensive application in the world.In the process of the large-scale construction of passenger dedicated line in China, the proportion of bridge in the whole basis is increasing and many long span bridges have been constructed. When the continuous welded rail is laid on the bridge, the expansion of beam increases interaction between beam and rail, then the rail has to bear additional expansion and contraction forces which probably exceed allowable stress of the rail. Meanwhile, large relative displacement between rail and bridge beams also influences the stability of the line. As a result, it is necessary to use the rail expansion joint on the continuous welded rail which has a super-long span. However, it needs a thorough research on the problems, such as how many rail expansion joints to use, where to lay them and choose what kind of rail expansion joint.On the base of the continuous welded rail calculation software bcwr, this paper applied the apdl language of ANSYS finite element software to programming the rail expansion joint calculation program EJ, and this program is used to analysis interaction between beam and rail in the situation of beam expansion, moreover, different forms of bridges, railway, rail expansion joints and the various layout of them could be considered in the program. This paper also provides the testing indices of rail expansion joint containing the expansion of stock rail, relative displacement between rail and beam(ballast track),gauge variation, bolt strength of rail brace.This paper chooses some typical bridges with ballast track and lays the rail expansion joint on them, then analyses and calculates them by EJ. The result is as below:for improving the fixed action of the switch rail, the fastening resistance of all the switch rail should be increased. It is not proper to only change the four fasteners at the end of the switch rail to fasteners with bolts, even if the four sleepers are linked together by the sleeper coupling. Through the sleeper coupling, the sleepers form a frame so that the resistance increases, then the fastener has to transfer greater force to overcome the resistance. By lengthening the sleeper coupling, the relative displacement between rail and beam can be reduced effectively and the sleeper can be prevented from loosening, in addition, it does not change the gauge. However, in this situation, the fastener at the end of the switch rail bears greater force so that the fastener which can provide larger resistance is needed. Relative to single circular curve and compound circular curve, the expansion resistance of stock rail is much larger when the non-working side of the switch rail is transition curve. The resistance of single circular curve and compound circular curve are close, while the curvature variation of compound circular curve is more reasonable with two small and similar abrupt change of curvature. Based on the curvature and the expansion resistance of stock rail, compound circular curve with R600+R300is applied to the non-working side of the switch rail. According to the testing indices of rail expansion joint, the pier force and the rail force and so on, the proper layout of the rail expansion joint is designed after calculating it by EJ. When the rail expansion joint is laid at the end of continuous beam, it should be close to1/4of the bridge span and the peak value of additional expansion and contraction forces. On one hand, it can effectively reduce additional expansion and contraction forces of the rail, on the other hand, the force fixed pier bearing is not too great. For the continuous beam having the big temperature span, one unidirectional joint is set at one end and one bidirectional at the other. Compared to the design that sets unidirectional joints at both ends and links the switch rail together, the former can keep the track stability because of the great temperature force accumulating in the rail on the bridge which may make the rail run from the fastener during the maintenance operation.