장대레일이 부설된 철도 교량은 궤도-교량 상호작용으로 인하여 경간장 연장에 제약이 있다. 이러한 한계를 극복하기 위하여 궤도와 교량 사이에 저마찰 슬라이드층을 두어 교량과 궤도의 종방향 거동을 분리시켜 상호작용을 원천적으로 저감시키는 슬라이딩 궤도가 개발되고 있다. 본 연구에서는 슬라이드층을 포함하는 궤도 시스템을 실규모로 제작하여 종방향으로 반복하중을 재하하는 시험을 통하여 슬라이딩 궤도의 저마찰 거동을 종합적으로 평가하고자 하였다. 하중 재하 속도를 0.2, 1.0, 5.0, 10mm/min.으로 변화를 주었으며, 5,000, 10,000kg의 부가질량이 재하된 경우에 대한 마찰거동를 비교 검토하였다. 실험 결과 제안된 슬라이드층의 마찰계수는 0.22~0.33인 것으로 확인되었다. 더불어, 30년에 해당하는 10,000회의 반복하중을 재하하여 마찰계수 변화를 관찰한 결과, 마찰계수 증가는 7%에 머물러 반복하중에 대한 장기적인 내구성을 확보한 것으로 확인되었다. 슬라이드층의 마찰계수의 변화에 따른 영향을 상호작용 해석을 통하여 추가로 검토하였다. Railway bridges with continuously welded rail have a limitation of span length due to track-bridge interaction. In order to overcome this, a sliding slab track system has been developed that comprises with a low-frictional sliding layer between the bridge deck and the track slab to isolate the longitudinal behavior between the bridge and the track. In this study, a real scale track system is prepared to experimentally evaluate the longitudinal frictional behavior. Applied loading rates were 0.2, 1.0, 5.0 and 10mm/min; vertical mass on the track are track slab only, 5,000 and 10,000kg added mass, respectively. Test results showed that the resulting frictional coefficients varied from 0.22 to 0.33. In addition, 10,000 cycle loadings were applied to simulate repetitive sliding to represent 30 years of service life. The frictional coefficient increase was measured and found to be 7% of that of the initial loading stage, which means that the sliding layer is adequate to provide low-frictional behavior for the sliding slab track system. Effects of changes of the frictional coefficient of the sliding layer were analyzed by rail-structure interaction analysis.
Continuous welded rail (CWR) on a bridge structure typically experiences a large amount of additional longitudinal axial forces due to longitudinal rail-structure (or track-bridge) interaction under temperature change and train vertical and traction/braking load effect. In order to reduce the additional axial forces, a special type of fastener, such as zero longitudinal restraint (ZLR) and reduced longitudinal restraint (RLR) or rail expansion joint (REJ) should be applied. Sliding slab track system is developed to reduce the effect of rail-structure interaction through the application of a low-frictional sliding layer between slab track and bridge structure. This study presents a track-bridge interaction analysis of the sliding slab track and compares them with conventional fixed slab track on bridges. Various types of span length and longitudinal profiles of bridges are considered in the analysis, which also include multiple continuous spans and extra-dosed bridges. The analysis found that the sliding slab track can reduce the additional axial forces of the continuous welded rail from 80% to 90%, and the difference is more significant for long and continuous span bridge. By the application of the sliding slab track, the use of any other special type of rail fasteners or REJ can be avoided. In addition, span length will not be restricted by the rail-structure interaction effect in planning the railway bridge layout. Continuous span bridge has been usually avoided for railway bridges, but it is preferred for the application of the sliding slab track because the interaction effect can mostly be removed. A continuous span bridge usually has an economical cross-section for the bridge girder, pier and foundation and better dynamic characteristics compared to simple span bridge, and its application eventually will reduce the construction cost of the railway infrastructure.
CWR(continuous welded rail) on railway bridges should be carefully examined and installed due to additional rail stress caused by track-structure interaction. The additional rail stresses are caused by longitudinal displacement of bridge due to temperature change and train vertical load and traction/braking force. Design codes limit the additional rail stress less than or equal to 92 MPa. Previous researches showed that the additional rail stress generated through track-bridge interaction can be reduced significantly up to 80% by applying sliding slab track system. This study evaluates the effectiveness of partial application of the sliding slab track system, in which the sliding slab track is applied only at bridge roller support region rather than applying it to the entire bridge span. The proposed system has been verified here through track-bridge interaction analysis for 60 m or 70 m long simple span bridges and suggested proper application length of the partial sliding slab track.
Continuous welded rail on bridge structure experiences typically a large amount of additional longitudinal axial forces due to longitudinal track-bridge interaction under temperature and traction/braking load effect. In order to reduce the additional axial forces, special type of fastener, such as ZLR and RLR or rail expansion joint should be applied. Sliding slab track system is known to reduce the effect of track-bridge interaction by the application of a sliding layer between slab track and bridge structure. This study presents track-bridge interaction analysis results of the sliding slab track and compares them with conventional fixed slab track on bridges. The result shows that the sliding slab track can significantly reduce the additional axil forces of the continuously welded rail, and the difference is more significant for long and continuous span bridge.
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