Beom-Ho Park

Statistical Characteristics for Longitudinal Friction Behavior of Rail Fastening System for Concrete Track

Abstract In the case of CWR (Continuous welded rail) located on the railway bridge, the CWR has additional axialforce due to interaction of bridge and track. Therefore, the CWR tracks located on the bridge have to secure the safetyof running train and CWR track through mitigating influence for interaction of bridge and track. The railway designguide in Korea (KR C-08080) provides a certain value for property of longitudinal friction behavior of rail fastening system that is major parameter of interaction behavior by applying European codes. However, in order to apply todomestic railway, it is necessary to review property characteristics of the rail fastening system in actual use. In thispaper, the experiment for longitudinal friction behavior of rail fastener applied to concrete track on the railway bridgein Korea was carried out, and statistical characteristic for property of the rail fastener was analyzed from the result of the experiment. Keywords : Concrete track, Longitudinal friction behavior, Rail fastener, Statistical characteristic, Track-bridge interaction

Suggestion for allowable additional compressive stress based on track conditions

A continuous welded rail has immovable zones due to its structural characteristics. In an immovable zone, thermal expansion and contraction of rails are restricted when the temperature changes, thereby causing excessive axial force on the rail. When the immovable zone of the continuous welded rail is located on a bridge, additional stress and displacement occur through track–bridge interactions. Additional stress and displacement of the rail compared to the embankment area are restricted when constructing the bridge under the continuous welded rail track to prevent problems with the track–bridge interaction according to UIC 774-3R and Euro codes. According to the various codes, the maximum allowable additional compressive stress is 72 MPa, with the conditions of a curve with a radius (R) ≥ 1500 m, UIC 60 continuous welded rail (tensile strength of at least 900 MPa), ballasted track with concrete sleepers and 30 cm of deep for a well-consolidated ballast. However, the lateral resistance that has the greatest effect on track stability can depend on the conditions mentioned above. Therefore, an additional review of various track conditions is required. In this paper, an evaluation of the current criteria was performed using the minimum buckling strength calculation formula, and the allowable additional stress on the rail suggested by codes could only be used on tracks with a large lateral resistance above 18 kN/m/track. Thus, a three-dimensional nonlinear analysis model was developed and analyzed to calculate the allowable additional compressive stress considering various track conditions. According to the results of the analysis, the allowable additional compressive stress was reduced with a comparatively small lateral resistance. The freedom of design can be enhanced with respect to the parameters of various track and bridge conditions using this model.

Behavior of Tension Clamp in Rail Fastening System

Abstract In a situation in which importance of rail fastening system is growing with increasing the construction of concrete track, an accident of tension clamp(the component of rail fastening system) breaking has been recently occurred. This results from various factors such as field condition, operating agency, running condition, traffic frequency and so on. Thus, the study for the behavior of tension clamp is required. In this paper, an experiment and finite element analysis(FEA) have been performed to analyse the mechanical behavior of tension clamp. The stressand displacement of tension clamp have been analyzed as the clamping force through a laboratory test, and they werecompared with FEA results. Furthermore, the stress and displacement of the tension clamp are derived from train loadcondition applying the verified model, and the fatigue vulnerability of the tension clamp is identified through stressanalysis. Keywords : Concrete Track, Finite Element Analysis(FEA), Mechanical Behavior, Rail Fastening system, Tension Clamp

Track-bridge Longitudinal Interaction Response Analysis Considering the Variation of Temperature

When a continuous welded rail(CWR) track is supported by bridge, additional axial stress and displacement are occurred by track-bridge interaction, and they have an effect on safety and serviceability of track. Domestic and foreign standards for track-bridge interaction offer analysis methods and limit values which are guiding the safety design, because the influence on interaction is difficult to be evaluated quantitatively. In this study, measurement system was constructed on the concrete a track supported by a bridge, and field monitoring has been carried out to evaluate the influence on track-bridge interaction by temperature changes. And track-bridge interaction responses under various temperatures were analyzed by comparing results of measurement and numerical analysis.

Some Thoughts on the Preliminary Seismic Performance Evaluation Procedure of Subway Infrastructures

There is a few problems in the preliminary seismic performance evaluation procedure of subway infrastructures, such as cut-and-cover tunnel structures and bridge structures, recently because the characteristics of subway infrastructures are not properly considered in the procedure. In particular, the evaluation procedure of vehicular bridge structures is applied to subway bridges without any modification. Moreover, the present evaluation procedure is lack of both theoretical and empirical backgrounds, which makes the evaluation less reliable. This paper presents problems in the existing preliminary evaluation procedure and proposes possible modification(revision) to the procedure.