Effect of reverse bending deformation of large-span cable-stayed bridge on ballastless tracks’ behaviors

Weiqi Zheng,Xingwang Sheng,Zhihui Zhu,Tao Shi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.80 No.2

Laying ballastless tracks on large-span cable-stayed bridge is a new challenge, and it is particularly important due to the obvious advantages of ballastless track and the high requirements of high-speed railways. Under the complex load conditions in service, cable-stayed bridges have a variety of beam local deformations, and they inevitably affect the performances of the ballastless tracks laid on the bridge. In this work, a series of experimental studies and FEM simulations are carried out based on a large-span cable-stayed bridge and its segmental model. The main conclusions include: Under the most unfavorable reverse bending deformation of the large-span cable-stayed bridge, tensile and compressive deformations occurred at interlayers of the ballastless tracks with different isolation layers. The interlayer deformation variations of the ballastless tracks with EPDM or geotextile isolation layers are the same, and the deformation values of the ballastless tracks with EPDM isolation layers are larger than that of the ballastless tracks with geotextile isolation layers. However, due to the pre-compression of the EPDM isolation layer subjected to its upper structures’ deadweight, it can reduce the influences of the reverse bending deformation on the ballastless tracks, and the gaps and voids at ballastless track interlayers can be avoided. Furthermore, the 5.92 m length ballastless tracks with EPDM isolation layer is recommended to apply on the large-span cable-stayed bridge in high-speed railway to ensure the reliability and durability of the ballastless tracks.

무도상 교량 레일 장대화시 침목고정장치 강성에 따른 궤도-교량 상호작용 영향 분석

박종찬,이영섭,유근한,임남형 한국도시철도학회 2019 한국도시철도학회논문집 Vol.7 No.2

In recent years, in Korea, the speed of train has been increased drastically. So it is essential to installing continuous welded rail to complement the rail joint which is the vulnerable point of the track. Continuous welded rail not only can offer the pleasant ride for the passengers by remove the vibration of train but also it can make a huge contribution on the reduction of maintenance cost by extending the track maintenance period. In Korea, ballastless track bridge has been constructed since 1900s and it has been the most constructed type. However, it is difficult to install continuous welded rail in ballastless track bridge because of the additional stress caused during the installation of continuous welded rail. The stiffness of the sleeper fastener device, which is a component of ballastless track bridge, has a great influence on the additional stress due to track-bridge interaction when installing continuous welded rail. Thus, in this paper, in order to examine the possibility of installation of continuous welded rail by controlling the stiffness of sleeper fastener device, the influence of track-brdige interaction is analyzed according to stiffness of sleeper fastener device. 최근 국내에는 열차속도의 증가로 궤도의 취약부인 레일 이음매를 보완할 수 있는 장대레일은 필수적인 요소이다. 이러한 장대레일은 열차의 진동을 제거하여 쾌적한 승차감을 줄 뿐만 아니라 궤도 유지보수주기 연장으로 유지보수비용 절감에도 큰 기여를 한다. 그러나 국내에 1900년대부터 건설되어 현재까지 가장 많이 부설된 무도상 교량은 레일장대화시 발생하는 부가응력으로 인해 레일 장대화가 어려운 실정이다. 이러한 무도상 교량의 구성품인 침목고정장치의 강성은 레일장대화시 궤도-교량 상호작용에 의한 부가응력에 지대한 영향을 미친다. 따라서 본 논문에서는 침목고정장치 강성의 제어로 레일 장대화에 대한 가능성을 검토하고자 침목고정장치 강성에 따른 궤도-교량 상호작용의 영향을 분석하였다.

A comprehensively overall track-bridge interaction study on multi-span simply supported beam bridges with longitudinal continuous ballastless slab track

Miao Su,Yiyun Yang,Rensheng Pan 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.2

Track-bridge interaction has become an essential part in the design of bridges and rails in terms of modern railways. As a unique ballastless slab track, the longitudinal continuous slab track (LCST) or referred to as the China railway track system Type-II (CRTS II) slab track, demonstrates a complex force mechanism. Therefore, a comprehensive track-bridge interaction study between multi-span simply supported beam bridges and the LCST is presented in this work. In specific, we have developed an integrated finite element model to investigate the overall interaction effects of the LCST-bridge system subjected to the actions of temperature changes, traffic loads, and braking forces. In that place, the deformation patterns of the track and bridge, and the distributions of longitudinal forces and the interfacial shear stress are studied. Our results show that the additional rail stress has been reduced under various loads and the rail’s deformation has become much smoother after the transition of the two continuous structural layers of the LCST. However, the influence of the temperature difference of bridges is significant and cannot be ignored as this action can bend the bridge like the traffic load. The uniform temperature change causes the tensile stress of the concrete track structure and further induce cracks in them. Additionally, the influences of the friction coefficient of the sliding layer and the interfacial bond characteristics on the LCST’s performance are discussed. The systematic study presented in this work may have some potential impacts on the understanding of the overall mechanical behavior of the LCSTbridge system.

무도상 교량 미끄럼 허용 궤광 시스템의 횡방향 보강판 현장 실험

박종찬(Jong Chan Park),임동휘(Dong Hwi Im),임남형(Nam Hyoung Lim),이진옥(Chin Ok Lee) 한국방재학회 2022 한국방재학회논문집 Vol.22 No.6

미끄럼 허용 궤광(Sliding Track Panel) 시스템은 트러스 교량과 같이 경간장이 긴 무도상 교량의 장대레일화 기법으로서 궤도-교량 상호작용으로 인해 레일에 발생하는 부가응력을 감소시키는데 목적이 있다. 그러나 STP 시스템은 기존 무도상 교량에 설치되어 있는 침목고정장치를 제거하여 종방향 저항력을 소거하는 시스템으로 수직방향과 횡방향에 대한 좌굴안정성이 결여되어 있다. 이를 보완하기 위해 횡방향 저항력을 증대 시킬 수 있는 횡방향 보강판을 설치하는 방안을 고안하였다. 본 논문에서는 횡방향 보강판에 대한 횡방향 저항력 증대 효과를 알아보기 위해 현장실험을 수행하여 궤광의 횡방향 저항성능을 도출하였다. The Sliding Track Panel (STP) System is a method for installing Continuous Welded Rail (CWR) in a long-span ballastless track bridge, such as a truss bridge. The STP system aims to reduce additional stress generated on the rail due to track-bridge interactions. However, as the STP system eliminates longitudinal resistance by eliminating the sleeper fastener device installed on the existing ballastless track bridge, there is no buckling stability in the vertical and lateral directions. Therefore, a plan was devised to install a lateral reinforcement plate to increase the lateral resistance. This paper investigated the effect of increasing the lateral resistance of the reinforcing plate through a field test to determine the lateral resistance performance of the track panel.

Dynamic Analysis of Slab Track with Crack Considering Rail Corrugation

Jianwei Yang,Peishan Liu,Xiaohui Wang,Yue Zhao,Fu Liu 대한토목학회 2023 KSCE Journal of Civil Engineering Vol.27 No.12

To investigate the dynamic response of ballastless slab track with crack in the rail corrugation area under the load of urban rail vehicle, this study establishes a vertical coupling dynamic model of the vehicle-rail-slab track, considering crack and rail corrugation. The exact closed-form solution of the vibration mode of the Euler Bernoulli beam with crack is introduced. Furthermore, a finite element model of the slab track is developed, and the vertical dynamic model's fastening force is applied to the slab track at the rail corrugation frequency to calculate the surface compressive stress of the slab track. The results indicate that, under rail corrugation conditions of varying magnitudes, the presence of crack induces higher vertical acceleration amplitudes in the slab track at low frequencies. As the wave depth increases, the acceleration of the slab track at the crack gradually intensifies. Moreover, with an increasing wavelength, the corresponding frequency to the acceleration amplitude of the slab track at the crack gradually decreases. Notably, when the wave depth is 0.2 mm and the wavelength is 50 mm, the axle load transfer rate exhibits the greatest increase. These research findings offer valuable insights for the maintenance of urban rail transit slab track systems.

Design Loads on Railway Substructure

Konstantinos GIANNAKOS 한국철도학회 2014 International Journal of Railway Vol.7 No.2

The superstructure of the railway track undertakes the forces that develop during train passage and distributes them towards its seating. The track panel plays a key role in terms of load distribution, while at the same time it maintains the geometrical distance between the rails. The substructure and ballast undergo residual deformations under high stresses that contribute to the deterioration of the so-called geometry of the track. The track stiffness is the primary contributing factor to the amount of the stresses that develop on the substructure and is directly influenced by the fastening resilience. Four methods from the international literature are used in this paper to calculate the loads and stresses on the track substructure and the results are compared and discussed. A parametric investigation of the stresses that develop on the substructure of different types of railway tracks (i.e. balastless vs ballasted) is performed and the results are presented as a function of the total static track stiffness.

Design Loads on Railway Substructure: Sensitivity Analysis of the Influence of the Fastening Stiffness

Giannakos, Konstantinos The Korean Society for Railway 2014 International Journal of Railway Vol.7 No.2

The superstructure of the railway track undertakes the forces that develop during train passage and distributes them towards its seating. The track panel plays a key role in terms of load distribution, while at the same time it maintains the geometrical distance between the rails. The substructure and ballast undergo residual deformations under high stresses that contribute to the deterioration of the so-called geometry of the track. The track stiffness is the primary contributing factor to the amount of the stresses that develop on the substructure and is directly influenced by the fastening resilience. Four methods from the international literature are used in this paper to calculate the loads and stresses on the track substructure and the results are compared and discussed. A parametric investigation of the stresses that develop on the substructure of different types of railway tracks (i.e. balastless vs ballasted) is performed and the results are presented as a function of the total static track stiffness.

무도상 장대교량 레일의 장대화 방안에 대한 소고

박종찬,이영섭,유근한,임남형 한국방재학회 2018 한국방재학회논문집 Vol.18 No.7

In Korea, ballastless track bridges have been built since the early 1900s and are one of the most popular railway bridges. However, because the self-weight of the upper structure is relatively lightweight compared to the train, severe noise and vibration occur, and it is difficult to increase the train speed, owing to a 20-50 m long rail being connected by the seam plate. To overcome these problems, welded rails for ballastless track bridges are urgently required. This study preliminarily investigates the installation of continuous welded rails (CWR) for ballastless tracks in order to analyze the effects of and issues due to the track-bridge interaction in this configuration and determine solutions. 국내에서 무도상교량은 1900년대 초반부터 건설이 시작되어 현재까지 가장 많이 부설되어 온 철도교 형식 중 하나로 100년 이상 공용중인 교량도 있는 상황이다. 그러나 무도상교량은 상부구조의 자중이 열차보다 상대적으로 경량이라는 특성때문에 심각한 소음과 진동이 발생하며, 20~50 m 길이의 레일을 이음매판으로 연결하여 사용하고 있어 고속화도 어려운 실정이다. 이러한 문제점들을 해결하기 위해서는 무도상교량 레일의 장대화가 시급하다. 본 논문은 무도상교량 레일의 장대화를 위한 기초연구로서 장대화시 궤도 교량 상호작용으로 인한 영향과 문제점을 파악하고 그 해결방안에 대해 알아보고자 한다.

Intelligent identification of mortar void in ballastless slab track using the wheelset acceleration combined with CNN-SVM

Xin Xin,Zunsong Ren,Yi Yin,Jinsheng Gao 대한기계학회 2022 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.36 No.12

Mortar void is a hidden defect in ballastless slab track difficult to be efficiently identified by traditional detection methods. This paper is dedicated to proposing a new detection method to identify the mortar void position and length using the vehicle response combined with the hybrid convolutional neural network-support vector machine (CNN-SVM) classifier. The vertical wheelset accelerations with different mortar void conditions are collected from a vehicle-track coupled dynamics simulation model. The first components decomposed from wheelset accelerations by local mean decomposition and their envelopes are utilized as the training data due to their sensitivity to mortar void. To improve the identification precision, the scope descent method is proposed to determine the range influenced by mortar void (IMVR) and samples are labeled according to IMVR. Meanwhile, identification results are post processed based on the mortar void characteristics. The results show that over 90 % mortar void conditions with the length of 0.65 m are detected correctly and the identification has a higher precision with the mortar void length greater than 0.95 m. The proposed technology of mortar void detection using the wheelset accelerations with the hybrid CNN-SVM classifier provides reference for engineering application, which is of great significance to relieve the pressure of health monitoring of railway track.

Experimental Study on Bond Performances of Track Slab and Mortar Based on DIC Technology

Chengguang Su,Dan Liu,Chenxu Ding,Chuang Gong,Pingrui Zhao,Xueyi Liu 대한토목학회 2018 KSCE JOURNAL OF CIVIL ENGINEERING Vol.22 No.9

In order to guarantee the normal long-time service performance of CRST II slab track, it is necessary to study the interface parameters between track slab and CA mortar layer of CRTS II slab track. Thus the splitting and shearing model test of concrete and mortar bonded composite specimens were conducted. Based on the Digital Image Correlation (DIC) technology, the stress-strain relationship and cohesion model parameters were obtained from the interface displacement and distribution of strain. The results showed that: The displacement and the strain field distribution of the composite specimens as well as the whole interlaminar cracking process of initiation, propagation and failure can be well described with DIC. The bond failure between the track slab and the CA mortar layer is part of the brittle failure, and the normal and tangent interface tension-displacements are both bilinear. The shear strength between the track slab and the CA mortar layer is 1.82 MPa with the peak strain of 2.49 × 10−4 and the secant modulus of 7.30 × 103 MPa; While the shear strength is 2.40 MPa with the peak strain of 6.17 × 10−3 and the secant modulus of 3.89 × 102 MPa. When the shear strain is about 7.5×10-4, the shear stress-strain curve tends to remain stable. At this point, the shear strain is 0.12 times of the peak strain. Parameters of the cohesive zone model between the track slab and the CA mortar layer are suggested as follows: the normal cohesive strength is 1.792 MPa with the interface stiffness of 708.485 MPa/ mm and the critical fracture energy of 0.0252 mJ/mm2; the tangential cohesive strength is 0.956 MPa with the interface stiffness of 63.039 MPa/mm and the critical fracture of 0.018 mJ/mm2.