Vibration Analysis Of Track Structure Containing Imperfections Under Moving Random Loads

With the development of high speed realization of passenger transport and heavy haul realization of freight transport, the status of railway transportation is becoming more and more important in the transportation system. As the basis of railway transportation, the track structure often has fastener failure, unsupported sleeper, uneven settlement of subgrade and other unfavorable imperfections under repeated train loads. The presence of these imperfections is very unfavorable for the safe run of train, and greatly accelerates the fatigue damage of track structure. In view of this, many scholars at home and abroad have studied these imperfections. But to simplify the problem, they generally use deterministic excitation to simulate the train load. However, since the objective existence of the track random irregularity, the train load actually is random excitation. Therefore, using random process to simulate the train load, and studying the vibration of track structure system containing imperfections under moving random loads is more practical significance for the design, maintenance and repair of track line.Based on pseudo-excitation method, this paper presents the basic principle of random vibration analysis of track structure under moving random loads and the implementation process of this principle in the finite element software ANSYS. And according to this, the track structure model of rail as an Euler beam supported three layers of discrete elastic points considering the shear effect between the adjacent ballast block is established to study the effect of fastener failure, unsupported sleeper and uneven settlement of subgrade on the random vibration characteristics of track structure.The main conclusions of this study are as follows:1) When there are imperfections in the track lines, vibrations of the track structure components at imperfections and adjacent location have obviously increased. And the more serious the imperfections are, the more significant random vibrations of the components are. This is also more unfavorable to keep the stability of track structure and the comfort of line.2) Fastener failure and unsupported sleeper have a certain impact on the distribution of the displacement power spectral density of the track structure components at imperfections and adjacent location in frequency domain. And the greater the number of continuous fastener failure and unsupported sleeper is, the broader the scope of influence is, also the more significant the effect is.3) Uneven settlement of subgrade has a great impact on the distribution of the displacement's and acceleration's power spectral density of the track structure components in frequency domain. Especially when the values of subgrade's stiffness and damping at the magnitude of settlement are zore, this effect will become very obvious and shouldn't be ignored.4) Single fastener failure's scope of influence is the same as single unsupported sleeper. their scope of influence are all about six sleeper spacings which include imperfection section. And the effect of fastener failure or unsupported sleeper on the random vibration characteristics of the track structure which is farther from the imperfection is also weaker.5) Among the three kinds of imperfections which are fastener failure, unsupported sleeper and uneven settlement of subgrade, the effect of uneven settlement of subgrade on the displacement and acceleration of the components is most significant and it has also most serious damage on the stability and comfort of track structure.6) The effect of single fastener failure on the random vibration displacement of the track structure components is basically the same as single unsupported sleeper, but the effect of the former on the random vibration acceleration of the components is more serious than the latter.7) The effect of two consecutive unsupported sleeper on the random vibration displacement of the track structure components is obviously larger than two consecutive fastener failure, but there isn't obvious rule about the effect of them on the vibration acceleration of the components.