Kyung-Min Yun

Containment capacity and estimation of crashworthiness of derailment containment walls against high-speed trains

Europe, USA, China, Japan, and Korea, which possess advanced railway technologies, have attempted to develop high-speed rail technology and ensure safety based on social requirements and the need for greater speeds. However, despite these efforts, there have been recent reports of train accidents resulting in loss of lives. Fatal train accidents usually involve derailments or collisions that do not happen frequently. However, when they occur, the damage is catastrophic. Therefore, a protection infrastructure should be installed to minimize such damage. Since the high-speed railways were introduced in Korea, derailment containment walls have been constructed to mitigate and minimize the damages caused by such accidents. The need for the judgment of effectiveness and feasibility review of the derailment containment walls in terms of economics and construction ability has been presented by designers and constructors. In this paper, the authors have evaluated the containment capacity and collision durability (crashworthiness) of a derailment containment wall, constructed in Korea, using a collision simulation after the derailment of a train.

Effects of H-type Sleeper on the Track Behavior

The demand for improved rail transportation safety is growing due to the increased speeds of current railways. In addition, freight trains with heavier axle loads are required to run on conventional railways. In order to meet these requirements, increased rail weights and the application of a CWR system have been introduced on conventional railways. The H type sleeper, which has higher lateral resistance than the existing mono sleepers, has been recently developed to increase track stiffness and reduce track irregularities. In this paper, the effects of a H-type sleeper on track behavior were investigated by 3-Dimensional F.E. analysis.

A Guideline for Development of Track-Bridge Structural System with Sliding Layer to Reduce the Track-Bridge Interaction

The bridges take a significant part of entire route in Korea railway, because 70% of Korean territory is covered with mountains. For this reason, span enlargement of railway bridges is more advantageous to increase economic efficiency on the bridge design. However there are many limitations such as additional axial force of the rail, excessive displacement due to track-bridge interaction. In this study, track-bridge interaction analysis was conducted considering the sliding layer which was installed between the track and girder. From the numerical analysis results, the behavior of track-bridge interaction was investigated according to the installation method of sliding layer. Finally, a guideline for development of track-bridge structure system to reduce the track-bridge interaction was proposed.

Additional Axial Stress of CWR Track on the Bridge according to the Variation of Design Vehicle Load

The CWR(Continuous Welded Rail) on a bridge shows complex structural behavior compared to those on the roadbed. The influence factors on the track-bridge interaction are the variation of temperature and vehicle load. The analysis methods for track-bridge interaction, material property, modeling method, loads and combination method are indicated in the domestic railway design principle, KR C-08080. The vehicle load in KR C-08080 was changed in 2014. In this study, to evaluate the effect of the changed vehicle load on the track-bridge interaction, the track-bridge interaction analyses were performed for 22 bridges by using finite element method.

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

Design Consideration of Fish-bone Girder Pier using the Analysis of Torsional Behavior

Abstract A modular fish-bone girder pier consists of one main girder system named as “Spine Girder”. Therefore, this pier can be most affected by torsion as well as flexural bending. The design considerations of the fish-bone girder pier are proposed to assure the reasonable design in this study. In order to investigate the behavior characteristics, structural analysis F.E model is developed, and the verification of the developed model is performed by comparison with experimental data. From the investigation of the structural behavior, the vertical stiffener is required at the bottom of bone-beams to prevent the excessive local stress. Also, it is found that the normal stress of the flange and the shear stress of the web and flange are dominantly affected by the warping torsion and pure torsion, respectively. Key Words : Pier, Fish-bone girder, Spine girder, Bone beam, warping, torsion 본 연구는 국토해양부 지역기술혁신사업(09지역기술혁신 B-01)의 연구비지원에 의해 수행되었습니다. * Corresponding Author : Nam-Hyoung Lim(Chungnam National Univ.)Tel: +82-41-821-7005 email: nhrim@cnu.ac.krReceived November 28, 2013 Revised January 8, 2014 Accepted January 9, 2014

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.

Impact Force Evaluation of the Derailment Containment Wall for High-Speed Train through a Collision Simulation

Fatal train accidents usually involve derailments or collisions. These derailment/collision accidents are infrequent. However, the damage due to derailment can be catastrophic. Derailment containment walls are usually used in Korea to minimize such damages. However, the impact forces that are needed to design the derailment containment walls were not well defined, and only limited studies were conducted for the behavior of the derailment containment walls. In this study, the focus was made on the impact force analysis of the containment wall through a series of 3D collision simulation after train derailment. Finite element modeling was conducted to analyze the dynamic behavior of the derailed train that collides with a structure such as containment wall using the LS-DYNA analysis software application. The FE models of car bodies, bogie frames, and wheel sets were created such that full conformity was achieved between their numerical models and actual vehicles with respect to the masses and principal mass moments of inertia. In addition, various installation situations of the containment wall were considered for the collision simulation. Finally, the economical alternative method to reduce the impact force was proposed.

Investigation of Microstructure and Mechanical Properties of KR60 Rail

The use of continuous welded rail is increasing because of its many advantages, including vibration reduction, enhanced driving stability, and maintenance cost savings. In this work, two different types of continuous welded rails were examined to determine the influence of repeated wheel-rail contact on the crystal structure, microstructure and mechanical properties of the rails. The crystal structure was determined by x-ray diffraction, and the microstructure was examined using optical microscopy and scanning electron microscopy. Tensile and microhardness tests were conducted to examine the mechanical behaviors of prepared specimens taken from different positions in the cross section of both newly manufactured rail and worn rail. Analysis revealed that both the new and worn rail had a mixed microstructure consisting of ferrite and pearlite. The specimens from the top position of each rail exhibited decreased lamella spacing of the pearlite and increased yield strength, ultimate tensile strength and hardness, as compared with those from other positions of the rail. It is thought that the enhanced mechanical property on the top position of the worn rail might be explained by a mixed effect resulting from a directional microstructure, the decreased lamella spacing of pearlite, and work hardening by the repeated wheel-rail contact stress.

An Experimental Study for Longitudinal Resistance of Ballast Track on Bridge

Abstract When a ballast track of a high-speed train is constructed on a bridge, the displacement of the bridge deckscan occur because they are not fixed to the rails. Moreover, relative displacements occur between the bridge and railscaused by temperature changes and external loads. The current longitudinal resistance criteria (UIC Code 774-3, KRC-08080) on ballast tracks with continuous welded rails (CWRs) do not take into account the longitudinal movement of the bridge and the frictional force between the ballast and slabs. In addition, the magnitude of the longitudinalresistance, k, is calculated somewhat conservatively and, (therefore?) it acts as an unfavorable element in the design of long span and continuous railway bridges. Thus, in order to replicate the actual behavior more effectively, the longitudinal resistance of CWRs should take into account the additional rigidity between the slab and track. In this study, the longitudinal resistances of the ballasted track on the bridge were analyzed by carrying out an experimentalstudy with a test setup designed to simulate the deck and bed track. In the test results, the maximum longitudinalresistances of the tests were similar to the resistances of the current codes, however, the measured longitudinal stiffness designed to limit the displacement of the tests were much smaller in comparison with the longitudinal stiffness on the codes.