Analysis Of Dynamics Behavior For The Defective Track Under The Moving Load

As a product of modern technology, Railway plays an important role in both enhancing inter-regional contact and promoting the development of national economy. East Shinkansen of Japan (train speed of 210km) was built in 1964, which marked the advent of the modern era of high-speed rail. Now our country has the fastest and the most complex high-speed rail system of the world. Track structure as an important carrier of the train, experiencing long-term moving randomly wheel-rail power loads, which may lead to stiffness change or favorable settlement defects etc. The dynamic characteristic analysis is essential for safe operation of trains. Therefore, the study of dynamics behavior for the defective rail-track not only has the guiding significance for the scientific rail-track line and rational design, but also has some practical significance for the actual track maintenance.Based on pseudo-excitation method (PEM), using the commercial finite element system ANSYS secondary development achieved dynamic behavior analysis of track structure under a moving load in this paper. By establishing the finite element model of vertical track structure as an Euler beam supporting three layers of discrete elastic points, Dynamic response of track structure was respectively studied for fastener defect, ballast defect or subgrade defect under single-point moving harmonic load and random load.In this paper, five areas were studied:1) Establishment of track structure model, moving load types and the methods of defective track structure were reviewed. Then track structure model, moving loads and the simulation method of defective track structure were determined; 2) Based on the theory of track dynamics, ballast track structure vertical vibration equation was expressed. The finite element model and parameters of track structure were used; 3)The basic theory of PEM under single-point random moving excitation was introduced. This part had effectively combined PEM and secondary development of ANSYS to solve the random vibration problems under a moving load in ANSYS; 4) Dynamic behavior of track structure including fastener defect, ballast defect and subgrade defect problems had been studied respectively under single-point moving harmonic load; 5) Random vibration problems of track structure including fastener defect, ballast defect and subgrade defect problems had been studied respectively under single-point moving random load. The results show that the track structure dynamic response increases significantly for the fastener defect compared with the normal line. Especially when the fastener fails completely, the rail displacement increases rapidly on the fastener defect; Track structure dynamic response increases significantly for the ballast defect compared with the normal line. Especially when the ballast fails completely, sleeper vibration significantly strengthens on the ballast defect; The track structure dynamic response significantly increases for the subgrade defect than the normal line and the fastener defect, the ballast defect. Especially when part of the subgrade fails completely, vibration of each track component sharply increases, so there is a serious risk the integrity of track structure and the quality of track vehicle.