Study On Mechanical Behavior Of Ballasted CWR On The Bridge Under Complex Operating Conditions

ABSTRACT:The CWR has a huge advantage on improving running conditions, which reflected that application of this kind of track structure eliminated the rail joint, decreasing the impact from the vehicle, extending the life of the track structure, and reducing the ballasted track maintenance and repair costs. However, there are so much influencing factors to the system of vehicle-track-bridge and itself complex interactions, so as to ensuring the operation safety of train has become a key issue on CWR study. Therefore, the study of mechanical behavior of ballasted CWR on the bridge under complex operations has important theoretical significance and huge application value.In this paper, two kind of finite element models have been built, named Rail-Sleeper-Bridge-Pier model and Vehicle-Track-Bridge coupling dynamics model. The first model is established by ANSYS, which can be used to analyze stability of CWR. The second model is created by ABAQUS, also it can be used to calculate the track structure mechanical behavior. Based this two kind of models, the ballasted CWR can be analyzed. Finally, this paper discussed the CWR stability and proposed some pertinent advice. The main contents and results of this study are as follows:(1)The establishment of a Rail-Sleeper-Bridge-Pier finite element modelComputational model uses triple layers spring element to simulate fasteners, track pillow, foundation, piers and other parts, considering the effect of fastener resistance moment, simulating the actual working conditions of the track frame. What’s more, the model uses a new idea based on the combination of solid element with beam element, achieving a refined modeling of CWR, not only accuracy can be ensured, but the improvement of computational efficiency.(2) Revealing the rules of mechanical behavior of CWR on the bridge under foundation settlement and fastener corrosionBased on Rail-Sleeper-Bridge-Pier finite element model, considering the settlement value, the settlement location, the transition length and other factors, the paper analyzed the changes of CWR longitudinal force on the bridge under the bridge piers or embankment-bridge transition uneven settlement, considering the effect of fastener corrosion to stretching force. Studies have shown that the pier uneven settlement and fastener corrosion reduced the line longitudinal force, and the embankment-bridge transition uneven settlement increases the CWR longitudinal force. (3) Analyzing the effects of fasteners resistance to rail longitudinal forceThe paper summarized a variety of factors leading to the change of fastener resistance, and analyzed the impact of fasteners resistance to the longitudinal force on the large-span bridge, the results show that changes of resistance have a greater impact on the longitudinal force. If the small resistance fasteners longitudinal resistance increases, which can lead to rail broking or bulcking.(4) Exploring the effects of temperature gradient loads to track structureReferring a variety of domestic and international codes about the loading mode to bridge, this paper analyzed the changes of CWR longitudinal force. Results show that different computational model has great effect on rail longitudinal force; Considering the solar elevation angle, the bridge flange plate cover, temperature between sub-ballast and bridge deck and other factors, the paper discussed many load calculation model of instantaneous temperature, analyzed the torsional deformation of the beam as well as its effect on the track geometry and longitudinal force.(5) Analysis of the dynamic response characteristics according to unsupported sleeper or rail expansion joint areaBased on Vehicle-Track-Bridge coupling dynamics model, the paper studied the vertical and lateral wheel-rail force, track displacement, acceleration and so on. Results show that unsupported sleeper has little effect on comfort, but the large displacement, huge wheel unloading rate, make the track structure to be easily damaged; The derailment coefficient and wheel unloading rate of the rail expansion joint region can meet the requirements. However, the value of structure vertical force, displacement and acceleration are out of range, the rail expansion joint area is still the weak link of CWR.