다채널 충격반향법을 활용한 철도 콘크리트 궤도 슬래브 TCL/HSB 층분리 평가

이훈재,기성훈,이진욱,조국환 한국철도학회 2020 한국철도학회논문집 Vol.23 No.7

The primary objective of this research is to investigate the feasibility of multi-channel Impact-echo (IE) testing as a non-destructive evaluation method for evaluating debonding at the interface between TCL (traffic control layer) and HSB (hydraulically stabilized based course) in railway concrete slabs for the Korea train express (KTX). For these purposes, the research performed in this study includes three main tasks. First, prototype equipment was developed to perform multi-channel IE testing on the surface of concrete. Second, two concrete slab specimens (1500mm (width) × 1500mm (length) × 300mm (thickness)) were fabricated in the laboratory. Concrete slabs include six fabricated delamination defects with different areal sizes and depths. A signal interpretation method was proposed to evaluate the delamination defects using multi-channel IE testing. Third, multi-channel IE testing was applied to condition assessment of delamination defects between TCL and HSB in a real-scaled concrete mock-up specimen simulating railway concrete slabs for KTX. It was observed that the resonance frequencies measured over the delaminated defects were consistently lower than those measured in solid regions. Statistical analysis showed that the frequency difference due to delamination defects is statically meaningful at the significance level of 0.01.

고속철도 콘크리트 궤도상 토공노반의 장기거동 특성 연구

최찬용(Chan-Yong Choi),정재현(Jae-Hyun Jung) 한국산학기술학회 2018 한국산학기술학회논문지 Vol.19 No.4

본 논문의 목적은 고속철도 콘크리트 궤도 및 노반 측정 데이터(노반압력, 진동가속도, 탄성변위 등)를 이용하여 토공노반의 장기거동을 분석하고 궤도·노반의 장기성능을 평가하고자 하는데 있다. 최근 고속철도 궤도 형식이 콘크리트 슬래브로 채택되고 있다. 그러나 콘크리트 궤도는 노반 침하에 취약하다. 자갈궤도의 경우 노반이 침하되어도 유지보수로 원상복구가 용이하다. 반면에 콘크리트 궤도의 경우 노반의 과도한 침하가 발생하면 도상 및 침목에 균열이 지속적으로 발생되고 사용성이 크게 저하된다. 이와 같은 이유로 부분보수만으로 원상복구가 어렵다. 본 논문에서는 운영 중 콘크리트 궤도에 대하여 건설 초부터 매설된 센서의 측정 데이터를 개통 후 약 3년까지 모니터링하여 장기성능평가를 수행하였다. 성능평가 방법은 열차별 궤도·토공노반 및 장기 궤도·노반 성능평가, 장기침하에 따른 궤도․노반 성능 영향 분석 및 장기 침하 영향인자 분석 등이다. 열차별 궤도·노반 성능평가에서는 KTX-산천중련의 노반응답이 가장 컸다. 장기 궤도·노반 성능평가 결과는 측정항목이 기준치이내로 측정되었다. 장기침하에 따른 궤도·노반 성능영향 평가는 TCL처짐은 침하와 깊은 연관이 있는 것으로 분석되었다. 장기침하의 외부영향인자 분석을 통해 함수비와 지하수위의 영향성을 확인하였다. 이와같은 방법을 통해 궤도상 토공노반의 안정성을 확보할 수 있을 것으로 사료된다. This study examined the long-term behavior of a roadbed using high-speed railway concrete track and roadbed measurement data and evaluated the long-term performance of the track and roadbed. Recently, high-speed railway track type has been adopted as a concrete slab. On the other hand, the concrete track is vulnerable to roadbed settlement. In the case of gravel tracks, it is easy to restore the original state by maintenance even if the roadbed settles. On the other hand, in the case of the concrete track, if excessive settlement of the roadbed occurs, cracks are generated continuously on the slabs and sleepers, resulting in greatly reduced usability. For this reason, it is difficult to restore the original state only by partial maintenance. In this paper, a long-term performance valuation was carried out on a concrete track during operation by monitoring the measurement data of sensors buried from the beginning of construction for approximately 3 years after the high-speed railway opened. Performance evaluation methods include a performance evaluation of track/roadbed when the train passes, long-term track and roadbed performance evaluation, analysis of the track/roadbed effect on long-term settlement and analysis of the factors influencing long-term settlement. The trail response of KTX-Sancheon was greatest in the track/roadbed performance evaluation by train. The results of the long-term track and roadbed performance evaluation were measured within the standard values. The track and roadbed performance impact assessment with long-term settlement was strongly related to TCL settlement. The influences of the water content and groundwater level were verified by analyzing the external factors of long-term settlement. Through such a method, the stability of a track/roadbed can be secured.

PSC 박스 거더 철도교량의 해석 및 스트럿-타이 모델에 의한 격벽부 설계

송하원,김형운,김영훈,변근주,Song, Ha-Won,Kim, Hyoung-Woon,Kim, Young-Hoon,Byun, Keun-Joo 한국철도학회 1998 한국철도학회논문집 Vol.1 No.1

The functions of diaphragms at abutments and piers of PSC box girder railway bridge are to transfer forces from the superstructure onto bearings or columns and to stiffen the superstructure cross-section against in -plane deformation. Due to stress disturbance at diaphragm, the design for the diaphragm using conventional design method is relatively irrational than those for other structural members. And, due to contribution to boundary condition of deck slab by the diaphragm, the behavior of deck slab near the diaphragm is different from that of the deck slab obtained from two dimensional analysis of the bridge, which is basis for the design of deck slab. In this paper, three dimensional behavior of deck slab near the diaphragm of prestressed concrete (PSC) box girder railway bridge constructed by the precast span method are analyzed by using three dimensional finite element modeling and using the strut-and-tie model design of the diaphragm are presented. The modeling techniques used in this paper can be applied effectively to examine the causes of cracks at deck slab near diaphragm and to design diaphragm rationally.

PSC 박스거더 철도교량의 해석 및 스트럿-타이 모델에 의한 격벽부 설계

송하원(Song Ha-Won),김형운(Kim Hyoung-Woon),김영훈(Kim Young-Hoon),변근주(Byun Keun-Joo) 한국철도학회 1998 철도저널 Vol.1 No.1

The functions of diaphragms at abutments and piers of PSC box girder railway bridge are to transfer forces from the superstructure onto bearings or columns and to stiffen the superstructure cross-section against in-plane deformation. Due to stress disturbance at diaphragm, the design for the diaphragm using conventional design method is relatively irrational than those for other structual members. And, due to contribution to boundary condition of deck slab by the diaphragm, the behavior of deck slab near the diaphragm is different from that of the deck slab obtained from two dimensional analysis of the bridge, which is basis for the design of deck slab. In this paper, three dimensional behavior of deck slab near the diaphragm of prestressed concrete (PSC) box girder railway bridge constructed by the precast span method are analyzed by using three dimensional finite element modeling and using the strut-and-tie model design of the diaphragm are presented. The modeling techniques used in this paper can be applied effectively to examine the causes of cracks at deck slab near diaphragm and to design diaphragm rationally.

경부고속철도 콘크리트궤도의 균열 및 손상 유형

장승엽(Seung Yup Jang),최승선(Seung Sun Choi) 한국철도학회 2014 한국철도학회 학술발표대회논문집 Vol.2014 No.5

2010년 개통된 경부고속철도 2단계 구간(동대구~부산)에는 토공 구간을 비롯한 전 구간에 콘크리트궤도를 부설하였다. 우리나라에서는 콘크리트궤도에 대한 유지보수 경험이 많지 않기 때문에 앞으로 보다 체계적인 관리 기준을 수립해 나갈 필요가 있다. 이에 이 논문에서는 경부고속철도에 적용된 콘크리트궤도에 발생한 균열 또는 손상의 유형을 살펴 보았다. 현장조사 결과에 따르면, 가장 빈번하게 관찰되는 균열은 콘크리트 슬래브 (TCL)에서 횡방향으로 발생하는 균열로, 프리캐스트 콘크리트(PC) 침목과의 경계를 따라 나타나며, 토공구간에서 가장 빈도가 높게 나타나고 있다. 또 침목 하부 간극에 의한 침목-TCL 간의 분리 현상이 일부 구간에서 관찰되었고, 일부 PC 침목에서도 균열이 관찰되었으나 상대적으로 매우 빈도가 낮았다. 이러한 현장조사 결과를 토대로 각 균열 및 손상 유형별로 그 원인과 대책을 분석하였다. In the entire 2nd phase section(Dong-Dae-Gu~Busan) of Kyeong-Bu high-speed railway that was open in 2010, the concrete track has been installed. In Korea, because of insufficient experience on the concrete track, systematic maintenance standards should be established in the future. For this purpose, this paper investigated patterns of crack and damage occurred in the concrete track of Kyeong-Bu high-speed railway. According to the field investigation, cracks in concrete slab (TCL) are the most frequent, which develop following the interface between PC sleeper and TCL, and show the highest frequency on the earthwork. The separation of PC sleeper and TCL was observed in some area. Cracks in PC sleepers were also observed in some area, but the frequency was very low relative to the cracks in TCL. Based on these results, the causes and countermeasures on each type of cracks and damages were discussed.

Investigation of Cement Matrix Compositions of Nanosilica Blended Concrete

Kim, Jung Joong,Moon, Jiho,Youm, Kwang-Soo,Lee, Hak-Eun,Lim, Nam-Hyoung The Korean Society for Railway 2014 International Journal of Railway Vol.7 No.3

The use of pozzolanic materials in concrete mixtures can enhance the mechanical properties and durability of concrete. By reactions with pozzolanic materials and calcium hydroxide in cement matrix, calcium-silicate-hydrate (C-S-H) increases and calcium hydroxide decreases in cement matrix of concrete. Consequently, the volume of solid materials increases. The pozzolanic particles also fill spaces between clinker grains, thereby resulting in a denser cement matrix and interfacial transition zone between cement matrix and aggregates; this lowers the permeability and increases the compressive strength of concrete. Moreover, the total contents of alkali in concrete are reduced by replacing cements with pozzolanic materials; this prevents cracks due to alkali-aggregate reaction (AAR). In this study, nanosilica is incorporated in cement pastes. The differences of microstructural compositions between the hydrated cements with and without nanosilica are examined using nanoindentation, XRDA and $^{29}Si$ MAS NMR. The results can be used for a basic research to enhance durability of concrete slab tracks and concrete railway sleepers.

Investigation of Cement Matrix Compositions of Nanosilica Blended Concrete

Jung Joong Kim,Jiho Moon,Kwang-Soo Youm,Hak-Eun Lee,Nam-Hyoung Lim 한국철도학회 2014 International Journal of Railway Vol.7 No.3

The use of pozzolanic materials in concrete mixtures can enhance the mechanical properties and durability of concrete. By reactions with pozzolanic materials and calcium hydroxide in cement matrix, calcium-silicate-hydrate (C-S-H) increases and calcium hydroxide decreases in cement matrix of concrete. Consequently, the volume of solid materials increases. The pozzolanic particles also fill spaces between clinker grains, thereby resulting in a denser cement matrix and interfacial transition zone between cement matrix and aggregates; this lowers the permeability and increases the compressive strength of concrete. Moreover, the total contents of alkali in concrete are reduced by replacing cements with pozzolanic materials; this prevents cracks due to alkali-aggregate reaction (AAR). In this study, nanosilica is incorporated in cement pastes. The differences of microstructural compositions between the hydrated cements with and without nanosilica are examined using nanoindentation, XRDA and 29Si MAS NMR. The results can be used for a basic research to enhance durability of concrete slab tracks and concrete railway sleepers.

Crack detection in concrete slabs by graph-based anomalies calculation

Yuqing Zhou,Weifang Sun,Jiawei Xiang,Binqiang Chen,Wei Feng 국제구조공학회 2022 Smart Structures and Systems, An International Jou Vol.29 No.3

Concrete slab cracks monitoring of modern high-speed railway is important for safety and reliability of train operation, to prevent catastrophic failure, and to reduce maintenance costs. This paper proposes a curvature filtering improved crack detection method in concrete slabs of high-speed railway via graph-based anomalies calculation. Firstly, large curvature information contained in the images is extracted for the crack identification based on an improved curvature filtering method. Secondly, a graph-based model is developed for the image sub-blocks anomalies calculation where the baseline of the subblocks is acquired by crack-free samples. Once the anomaly is large than the acquired baseline, the sub-block is considered as crack-contained block. The experimental results indicate that the proposed method performs better than convolutional neural network method even under different curvature structures and illumination conditions. This work therefore provides a useful tool for concrete slabs crack detection and is broadly applicable to variety of infrastructure systems.

콘크리트궤도 부설 교량의 단부 사용성 검토를 위한 매개변수 연구

성덕룡(Sung Deok-Yong),김영하(Kim Young-Ha),박용걸(Park Yong-Gul),김성일(Kim Sung-Il) 한국철도학회 2008 한국철도학회 학술발표대회논문집 Vol.- No.-

Construction of concrete slab track is trending to increase gradually in national and international for reduction in track maintenance cost and secure of ride comfort. However, in case of railway bridge installed concrete slab track, the serviceability review of end deck should be performed for reducing the maintenance cost of track. The serviceability review of track contains that the compression force which is occurred on fastener of end bridge should be smaller than the compression force causing the deformation limit of elastic pad and the uplift force which is occurred on fastener of end abutment should be smaller than initial fastening force. Therefore, this study calculated the deflection and end rotation of the railway bridge according to the span length and stiffness of railway bridge and estimated the compression force and uplift force which are occurred on the track of end bridge using the finite element method. This study indicated the several diagrams that are contained the correlation between the behaviour of the track and the behaviour of the railway bridge. As a result, to reduce the end rotation of the railway bridge is very efficient to increase the height of railway deck.

슬라이딩 궤도 콘크리트 슬래브의 동절기 균열 검토

이경찬(Kyoung-Chan Lee),이성철(Seong-Cheol Lee),장승엽(Sung Yup Jang),여인호(Inho Yeo) 한국철도학회 2015 한국철도학회 학술발표대회논문집 Vol.2015 No.10

슬라이딩 궤도는 궤도 슬래브와 교량 바닥판 상면 사이에 저마찰 슬라이드층을 두어 궤도-교량 상호작용을 원천적으로 저감시킬 수 있는 새로운 형태의 궤도 시스템이다. 슬라이딩 궤도의 슬래브는 교량구간에 대해서도 일반적인 토공노반 구간의 콘크리트 궤도와 동일한 연속철근콘크리트 궤도(CRCT)의 형식을 취한다. 이러한 형태의 궤도 슬래브는 동절기 온도 하강시에 슬래브 전단면에 인장력이 재하되어 콘크리트에 균열이 필연적으로 발생하므로, 콘크리트의 수축과 크리프의 영향을 비롯하여 동절기 온도 하강시 발생할 수 있는 균열 간격과 균열폭을 유로코드 (EN 1992-1-1)와 CIRIA C660 보고서에 제시된 방법에 따라 검토하였다. 검토 결과 최대 균열간격에 대하여 허용 균열폭을 초과할 수 있으나, 침목과 슬래브가 접하는 면에서 신구 콘크리트 접합으로 인하여 선균열이 유도되므로, 침목간 순 간격을 고려할 시 허용 균열폭을 만족함을 확인하였다. Sliding slab track is a new type of slab track system enabling to reduce interaction between railway bridge and track by means of a low-frictional sliding layer. The slab is a continuously reinforced structure all over the bridge region including neighboring abutment and approaches, which becomes the similar type of CRCT as a conventional slab track in embankment region. This kind of slab tracks may exhibit cracks due to tension through the entire cross-section of slab when the ambient temperature is low in winter. In this paper, therefore, based on EN 1992-1-1 and CIRIA C660, crack spacing and crack width in winter have been theoretically examined with the consideration of concrete creep and shrinkage, and low ambient temperature. The results indicated that the predicted crack width is within the allowable limit provided by the design codes when the sleeper net spacing is considered as crack spacing, since cracks are induced at the interfaces between slabs and sleepers.