Hyun-Ung Bae

Development of a probabilistic buckling analysis scheme for continuous welded rail track

Continuous welded rail (CWR) track has several advantages when compared with conventional jointed rail track. However, a thermally induced axial load can lead to the buckling of CWR tracks, which can result in train derailment. The buckling of CWR tracks is affected by several parameters, including the rail’s neutral temperature, misalignment of the rails and ballast resistance. Most of these parameters can be considered as random variables. A deterministic analysis approach is generally used to predict the buckling of CWR tracks; however, it can provide conservative results since it is based on the worst-case scenario of these buckling parameters. This paper presents a probabilistic buckling analysis scheme for CWR tracks.

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.

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.

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.

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

Structural Analysis and Design of the H-typed Railway Tie

With speed up of railway, the demand for safety of the railroad transportation is on the increase in Korea`s conventional railways. In additions, freight trains with heavier axle load are required to run conventional railways. In order to solve these requirements, the increase of rail weight and the application of long rail system have been underway in conventional railways. However, the research on ties that is absolutely influencing the track stiffness in ballasted tracks has not been much progress. In this paper, the new H-typed tie is developed to increase the track stiffness and reduce the track irregularity. And from the structural analysis by FE program, the intial design drawing of the new H-typed tie is proposed.

Improvement Strategies for Coastal Zone Safety Facilities through Analysis of Domestic and Foreign Field Survey

Recently, the risk of safety accidents in the coastal zone has been increased due to revitalization of marine leisure and tourism. Because of a lack of regulations about technical and maintenance aspect for safety facilities, the effective measures to prevent safety accidents in the coastal zone have not taken with increasing rate of the accidents. The nature of land/sea and behavioral characteristics of a fisherman/port laborer/tourist/people at leisure should be taken into account properly when safety facilities to prevent safety accidents in the coastal zone are installed, since the characteristics of land/sea and many activities such as fishery, harbor works, tour, leisure are mixed in the geographic and environmental condition of the coastal zone. This study analyzes the current problems on the safety facility in the domestic coastal zone through the domestic and foreign(Hongkong, Macau) field survey. Also the direction of the improvement about the safety facility are proposed.

Development of the Light Emitting System embedded Concrete Curb

The safety accidents due to the insufficient visibility are frequently occurred at the coastal zone. Therefore, safety facilities that provide visibility are certainly required to prevent accidents. In order to solve this demand, the concept of the light emitting system embedded concrete (LESeCON) are established and then concrete curb is produced for application to the coastal zone. To investigate the mechanical and functional performance of concrete curb developed in this study, the bending strength test and the visibility test are conducted.