• Title/Summary/Keyword: Resilience pad

Search Result 14, Processing Time 0.021 seconds

Natural Frequency Analysis of Sleeper Floating Track System using Modal Test Technique (모달시험기법을 이용한 침목플로팅궤도의 고유진동수 분석)

  • Jung-Youl Choi
    • The Journal of the Convergence on Culture Technology
    • /
    • v.10 no.3
    • /
    • pp.833-838
    • /
    • 2024
  • The urban railway sleeper floating track(STEDEF) is a structure that structurally separates the sleepers and the concrete bed using sleeper boots and resilience pads to reduce vibration transmitted to the concrete bed. Recently, the resilience pads of sleeper floating tracks that have been in use for more than 20 years are deteriorating. Accordingly, in order to evaluate the performance of the resilience pad, a static spring stiffness test is being performed after extracting the resilience pad. This evaluation technique is performed after replacing the resilience pad in use. However, the track natural frequency can change depending on the resilience pad spring stiffness and the uplift and subsidence of the concrete bed. In this study, modal testing technique was used to evaluate the track natural frequency. For this purpose, the sleeper boots material, resilience pad spring stiffness, and track natural frequency according to concrete bed uplift and subsidence were measured using modal tests at a laboratory scale. It was analyzed that the natural frequency of the sleeper floating track was directly affected by changes in the spring stiffness of the resilience pad. In addition, the change in natural frequency due to the uplift and subsidence of the concrete bed was also found to be large. Therefore, it is believed that the modal test technique presented in this study can be used to evaluate the resilience pad deterioration and voided sleepers.

Evaluation on Fatigue Behavior of Resilience pad for Sleeper Floating Track System in Urban Transit (도시철도 침목플로팅궤도(STEDEF)의 침목방진패드 피로거동 분석)

  • Choi, Jung-Youl;Lee, Jeong-Sug;Bong, Jae-Geun;Kim, Su-Jin;Chung, Jee-Seung
    • The Journal of the Convergence on Culture Technology
    • /
    • v.6 no.3
    • /
    • pp.347-352
    • /
    • 2020
  • In this study, the variation of track impact factor according to the spring stiffness change rate of sleeper resilience pad was analyzed based on field measurements. In addition, the correlation between field measurement results and 7 million fatigue test results was verified. The fatigue effect diagram of the sleeper resilience pads was presented considering the nonlinear deterioration characteristics of the sleeper resilience pads used for the STEDEF track. Based on the field measurement results, the nonlinear characteristics of the track impact factor for the spring stiffness change rate over 30% of sleeper resilience pad on the track impact factor-track support stiffness diagram were analyzed to be consistent with the fatigue test results.

Estimation Method of Resilience Pads Spring Stiffness for Sleeper Floating Tracks based on Track Vibration (궤도 진동기반의 침목플로팅궤도 침목방진패드 스프링강성 추정 기법 연구)

  • Jung-Youl Choi;Sang-Wook Park;Jee-Seung Chung
    • The Journal of the Convergence on Culture Technology
    • /
    • v.9 no.6
    • /
    • pp.1057-1063
    • /
    • 2023
  • The urban railway sleeper floating track, the subject of this study, is an anti-vibration track to reduce vibration transmitted to the structure. currently, the replacement cycle of resilience pad for sleeper floating tracks is set and operated based on load. however, most previous studies were conducted on load-based structural safety aspects, such as fatigue life evaluation of sleeper anti-vibration pads and increase in track impact coefficient and track support stiffness due to increase in spring stiffness. therefore, in this study, we measure the vibration acceleration of the ballast for each analysis section and use the results of 7 million fatigue tests to calculate the spring stiffness of the resilience pad for each section. the spring stiffness of the resilience pad calculated for each section was set as the analysis data and the concrete vibration acceleration was derived analytically. the adequacy of analysis modeling was verified as the analyzed concrete bed vibration acceleration for each section was within the field-measured concrete bed vibration acceleration range. using the vibration acceleration curve according to the derived spring stiffness change, the spring stiffness of the resilience pad is estimated from the measured vibration acceleration. therefore, we would like to present a technique that can estimate the spring stiffness of resilience pad of a running track using the vibration acceleration of the measured concrete bed.

Damage Evaluation of Track Components for Sleeper Floating Track System in Urban Transit (도시철도 침목플로팅궤도 궤도구성품의 손상평가)

  • Choi, Jung-Youl;Kim, Hak-Seon;Han, Kyung-Sung;Jang, Cheol-Ju;Chung, Jee-Seung
    • The Journal of the Convergence on Culture Technology
    • /
    • v.5 no.4
    • /
    • pp.387-394
    • /
    • 2019
  • In this study, in order to evaluate the damage and deterioration of the track components of sleeper floating track (STEDEF), the field samples(specimens) were taken from the serviced line over 20 years old, and the track components were visually inspected, and investigated by laboratory tests and finite element analysis. As a result of visual inspection, the damage of the rail pad and fastener was slight, but the rubber boot was worn and torn at the edges of bottom. The resilience pads were clearly examined for thickness reduction and fatigue hardening layer. As a result of spring stiffness test of rail pad and resilience pad, the deterioration of rail pad was insignificant, but the deterioration of resilience pad exceeded design standard value. Therefore resilience pad was directly affected by train passing tonnage. As a result of comparing the deterioration state of the field sample and the numerical analysis result, the stress and displacement concentration position of the finite element model and the damage position of the field sample were coincident.

Dynamic Behavior of Sleeper Floating Track System(STEDEF) on Urban Rapid Transit According to Replacement of Resilience Pad (도시철도 침목플로팅궤도(STEDEF) 침목방진패드 교체에 따른 동적 거동)

  • Choi, Jung-Youl;Bong, Jae-Gun;Lee, Jeong-sug;Han, Jae-Min;Chung, Jee-Seung
    • The Journal of the Convergence on Culture Technology
    • /
    • v.6 no.3
    • /
    • pp.335-340
    • /
    • 2020
  • The purpose of this study was to compare the dynamic behavior of STEDEF track that of the sleeper floating track on urban rapid transit according to replacing the resilience pads and analyze the necessity of replacing the resilience pads experimentally. It was analyzed that the uniformity of the track support stiffness could be secured by replacing the used resilience pads with new resilience pads. Therefore, by replacing the used resilience pads, the measured track impact factor was found to be dramatically reduced below the track design standard, and it was analyzed that the track support stiffness could be restored to the design value. As a results, it is possible to restore track support stiffness to the design value and reduce track impact factor by replacing timely resilience pads, which is important to securing durability and improving service life of track components.

A Study on Estimation Method of Concrete Sleeper Strength for Sleeper Floating Track using Rebound Hardness Test Method (반발경도법을 이용한 침목플로팅 궤도의 콘크리트 침목 강도추정 기법 연구)

  • Chung, Jee-Seung;Lee, Jeong-Sug;Choi, Jung-Youl
    • The Journal of the Convergence on Culture Technology
    • /
    • v.8 no.3
    • /
    • pp.277-282
    • /
    • 2022
  • The sleeper floating track (STEDEF) in this study was a track type in which a very soft resilience pad was installed under a relatively thin concrete sleeper (RC Block). Therefore it was expected that the resilience pad could affect the estimation results of the concrete strength. In this study, field applicability evaluation was performed to apply the rebound hardness test method, which was a general method for estimating the compressive strength of concrete in civil structures, to concrete sleepers of railway tracks. In order to analyze the strength estimation technique of concrete sleepers reflecting the characteristics of track structures different from those of civil structures, the parameter experiments that could affect the strength estimation results of concrete sleepers in a serviced line were performed. As a result of the study, the appropriate hitting position was suggested considering the shape of the concrete sleeper, and the difference in strength estimation results according to the condition of the concrete sleeper and supporting conditions was derived.

Damage Analysis of Manganese Crossings for Turnout System of Sleeper Floating Tracks on Urban Transit (도시철도 침목플로팅궤도 분기기 망간크로싱의 손상해석)

  • Choi, Jung-Youl;Yoon, Young-Sun;Ahn, Dae-Hee;Han, Jae-Min;Chung, Jee-Seung
    • The Journal of the Convergence on Culture Technology
    • /
    • v.8 no.5
    • /
    • pp.515-524
    • /
    • 2022
  • The turnout system of the sleeper floating tracks (STEDEF) on urban transit is a Anti-vibration track composed of a wooden sleeper embedded in a concrete bed and a sleeper resilience pad under the sleeper. Therefore, deterioration and changes in spring stiffness of the sleeper resilience pad could be cause changes in sleeper support conditions. The damage amount of manganese crossings that occurred during the current service period of about 21 years was investigated to be about 17% of the total amount of crossings, and it was analyzed that the damage amount increased after 15 years of use (accumulated passing tonnage of about 550 million tons). In this study, parameter analysis (wheel position, sleeper support condition, and dynamic wheel load) was performed using a three-dimensional numerical model that simulated real manganese crossing and wheel profile, to analyze the damage type and cause of manganese crossing that occurred in the actual field. As a result of this study, when the voided sleeper occurred in the sleeper around the nose, the stress generated in the crossing nose exceeded the yield strength according to the dynamic wheel load considering the design track impact factor. In addition, the analysis results were evaluated to be in good agreement with the location of damage that occurred in the actual field. Therefore, in order to minimize the damage of the manganese crossing, it is necessary to keep the sleeper support condition around the nose part constant. In addition, by considering the uniformity of the boundary conditions under the sleepers, it was analyzed that it would be advantageous to to replace the sleeper resilience pad together when replacing the damaged manganese crossing.

Experimental and analytical study of a new seismic isolation device under a column

  • Benshuai Liang;Guangtai Zhang;Mingyang Wang;Jinpeng Zhang;Jianhu Wang
    • Earthquakes and Structures
    • /
    • v.24 no.6
    • /
    • pp.415-428
    • /
    • 2023
  • Low-cost techniques with seismic isolation performance and excellent resilience need to be explored in the case of rural low-rise buildings because of the limited buying power of rural residents. As an inexpensive and eco-friendly isolation bearing, scrap tire pads (STPs) have the issue of poor resilience. Thus, a seismic isolation system under a column (SISC) integrated with STP needs to be designed for the seismic protection of low-rise rural buildings. The SISC, which is based on a simple exterior design, maintains excellent seismic performance, while the mechanical behavior of the internal STP provides elastic resilience. The horizontal behaviors of the SISC are studied through load tests, and its mechanical properties and the intrinsic mechanism of the reset ability are discussed. Results indicate that the average residual displacement ratio was 24.59%, and the reset capability was enhanced. Comparative experimental and finite element analysis results also show that the load-displacement relationship of the SISC was essentially consistent. The dynamic characteristics of isolated and fixed-base buildings were compared by numerical assessment of the response control effects, and the SISC was found to have great seismic isolation performance. SISC can be used as a low-cost base isolation device for rural buildings in developing countries.

Cause Analysis for Sleeper Damage of Sleeper Floating Track in Urban Transit (도시철도 침목플로팅궤도의 침목손상 원인 분석)

  • Choi, Jung-Youl;Shin, Hwang-Sung
    • The Journal of the Convergence on Culture Technology
    • /
    • v.8 no.6
    • /
    • pp.667-674
    • /
    • 2022
  • In this study, the correlation between the damage type and operating conditions of the sleepers was analyzed based on the design data and visual inspection results for the concrete sleepers of the sleeper floating track (STEDEF) that have been in operation for more than 20 years. It appeared in the form of cracks, breakages, and breaks in the concrete at the center and tie bar contact and buried areas. As a result of the numerical analysis, it was analyzed that the change in the left and right spring stiffness of the sleeper resilience pad increases the maximum stress, tensile stress, compressive stress, and displacement of the concrete sleeper, and stress concentration in the concrete at the tie bar contact area. It was proved analytically that the sleeper resilience pad can affect the damage of the concrete sleeper. Therefore, damage of concrete sleepers in the sleeper floating track in urban transit could be caused by changes in spring stiffness of sleeper resilience pads. It was reviewed that preventive maintenance such as improvement and timely replacement of sleeper resilience pads was necessary.

Numerical Study on Flexible Forming Process for Sheet Metal (박판용 가변성형공정의 수치적 연구)

  • Heo, S.C.;Seo, Y.H.;Park, J.W.;Ku, T.W.;Song, W.J.;Kim, J.;Kang, B.S.
    • Proceedings of the Korean Society for Technology of Plasticity Conference
    • /
    • 2009.10a
    • /
    • pp.281-284
    • /
    • 2009
  • Flexible forming process for sheet metal using reconfigurable die is introduced based on numerical simulation. Numerical simulation of sheet metal forming process is carried out by using flexible dies model instead of conventional matched die set. Elastic cushion which has high resilience behavior from excessive deformation are inserted between forming punches and blank material for smoothing the forming surface which has discrete due to characteristics of the flexile die. As an elastic cushion, urethane pads are utilized using hyperelastic material model in the simulation. Formability in view of surface defect such as onset of dimple is compared with regard to various punch sizes. Consequently, it is confirmed that the flexible forming process for sheet material has appropriate capability and feasibility for manufacturing of smoothly curved surface instead of conventional die forming process.

  • PDF