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In high-speed line, at some part of the track which rubber ballast-mat installed, track irregularity grew rapidly and affected riding comfort and train running stability. It is urgently requested to establish counter-measures which can be applied to track under operation. To do this, it is very important to analysis the origin of that phenomenon before. Track support stiffness is an essential factor for evaluating track condition. Sudden changes of support stiffness along track occur instability of train and bad riding comfort. Preventing sudden changes of track support stiffness is a key technique in high-speed track maintenance. Besides the sudden changes, the magnitude itself also significantly affects track and train. Low stiffness of ballast-mat makes ballast acceleration area wider. And it may accelerate track irregularity growth. So, the stiffness should be limited. To calculate track stiffness, measuring load and displacement on track is needed. In this study, the behavior of the track which rubber ballast-mat installed was measured and analyzed to understand the origin of rapid growth of it.
Most of design parameters of Railway Structures are determined by the serviceability requirements, rather than the structural safety requirements. The serviceability requirements come from Ensuring of Running Safety and Ride Comfort of Train, Reduction of Track Maintenance Work Track-Bridge Interaction should be considered in the design of railway structures. In this study, a numerical method which precisely evaluate an axial force in rail and a rail expansion and contraction when turnout exist in succession on a CWR on a ballasted or on a ballastless track of bridge is developed. From the parameter studies using the developed method, additional stress of stock rail almost 25% is generated due to stock and lead rail interaction, even embankment not bridge. In case of ballasted track, additional stress of stock rail on bridge is very greater than on embankment, and therefore require detailed review in bridge design with turnout. Stresses of turnout rails on bridge are very sensitive according to the installed positions. In case of ballastless track, Stresses of turnout rails are similar as those of normal track.
In this study, a empirical equation which can be feasibly used to evaluate minimal track buckling strength without exact numerical analysis is presented. Parameter studies are carried out to investigate the effects of the individual factor on buckling strength. In order to simulate track buckling in the field as precisely as possible, a rigorous buckling model which accounts for all the important parameters is adopted. A empirical equation for prediction of minimal track buckling strength is derived by taking nonlinear regression of data which are obtained from numerical analyses. Its characteristics and applicability are investigated by comparing the results by the presented equation with the one by the equation which was presented in japan, and is frequently using in korea when designing track structure.
With speed-up of existing railway, a greater attention is paid to the riding safety and the comfort of the passengers. They are combined to some technical factors related to track such as alignment, derailment coefficient, and track bearing capacity. A quantitative analysis method for those technical factors is presented in this study. Calculating the allowable transit speed, the technical reviews of speed-up of Janghang-Line(Chunan~Janghang) are conducted. And the alternatives for improving train speed in existing railway are proposed.
Recently the railway becomes principal transportation on account of the important role in mass transit and commute in urban area. However, rail noise and vibration raise a major problem for the residents living nearby railway track. At that point of view, the effective counterplan for the soundproofing and protection of vibration has to be considered in the process of railway design. Therefore, the reliable computation of load caused by running train on rail is very important to estimate vibration of structure adjacent to railway. In this study, Input identification is used for the calculation of load and vibration, induced by high speed train on rail. The influence of railroad noise and vibration on structure is evaluated using the 3-D Finite element method and the reliability of the evaluation is discussed comparing with the results of the field measurements.
Recently continuous welded rail is generally used to ensure running performances and to overcome the problems such as structural vulnerability and fastener damage at the rail expansion joint. Though the use of continuous welded rail on bridge has the advantage of decreasing the vibration and damage of rail, it still the risk of buckling and breaking of rail due to change of temperature, starting and/or breaking force, axial stress concentration and so on. So, UIC code and many methods has been developed by researchers considering rail-bridge interaction. Although there are many research concerning stability of continuous welded rail about temperature change on bridge and starting and/or breaking force, the study of continuous welded rail for earthquake load is still unsufficient. In this study, the nonlinear seismic response analysis of continuous welded rail on bridge considering soil-structure interaction, geotechnical characteristic of foundation and earthquake isolation equipment has been performed to examine the stability of continuous welded rail.
In general, the national rail system put an emphasis on distribution planing of stations for smooth operation of transporting goods, train allocation, parking, and maintenance. Since the national rail system is operated on the ground level, it is feasible to improve various aspects of the system during its operation. On the contrary, urban rail system is operated in the limited space under the ground, and thus, improving various aspects of the system during its operation is infeasible. Specifically, the urban subway system must have a comprehensive track distribution plan because the urban subway system has to operate in a limited environment such as it operates in a much shorter time period, The subway system has to be ready for various operations and events such as trains returning in the opposite direction, parking trains that need repair, parking during night time, storing various maintenance equipments, and connections to other tracks. Furthermore, considering the future extension of tracks, a comprehensive track distribution plan is a must.