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Copyright of Journal of Railway Science & Engineering is the property of Journal of Railway Science & Engineering Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Additional temperature stresses in continuously welded rails (CWRs) are caused by track/bridge interaction (TBI) due to thermal actions. Exceeding permissible stresses in CWRs on the bridge can lead to track buckling or rail cracking, compromising the safety of railway traffic. The main aim of the conducted study is to determine the effects of the key parameters such as rail cross-sectional area, track longitudinal resistance, bridge expansion length, and longitudinal stiffness of the fixed bridge support on the reduction of additional temperature stresses in CWRs on steel truss railway bridges. To quantify the effects of these parameters, two steel railway bridges with CWRs and the maximum expansion lengths according to UIC Code 774-3 were analyzed: (1) simply supported truss bridge with expansion length of 60 m and (2) continuous truss bridge with expansion lengths of 2 × 60 m. According to the obtained results, the track longitudinal resistance had the most significant impact on additional temperature stresses in CWRs, leading to their reduction of up to 72%. The bridge expansion length and the rail cross-sectional area led to reductions of up to 25% and up to 18%, respectively. Considering the deformation criteria of TBI, the longitudinal stiffness of the fixed bridge support had a minor effect on the reduction of additional temperature stresses in CWRs. [ABSTRACT FROM AUTHOR]

Copyright of Railway Standard Design is the property of Railway Standard Design Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Additional temperature stresses in continuously welded rails (CWRs) are caused by track/bridge interaction (TBI) due to thermal actions. Exceeding permissible stresses in CWRs on the bridge can lead to track buckling or rail cracking, compromising the safety of railway traffic. The main aim of the conducted study is to determine the effects of the key parameters such as rail cross-sectional area, track longitudinal resistance, bridge expansion length, and longitudinal stiffness of the fixed bridge support on the reduction of additional temperature stresses in CWRs on steel truss railway bridges. To quantify the effects of these parameters, two steel railway bridges with CWRs and the maximum expansion lengths according to UIC Code 774-3 were analyzed: (1) simply supported truss bridge with expansion length of 60 m and (2) continuous truss bridge with expansion lengths of 2 × 60 m. According to the obtained results, the track longitudinal resistance had the most significant impact on additional temperature stresses in CWRs, leading to their reduction of up to 72%. The bridge expansion length and the rail cross-sectional area led to reductions of up to 25% and up to 18%, respectively. Considering the deformation criteria of TBI, the longitudinal stiffness of the fixed bridge support had a minor effect on the reduction of additional temperature stresses in CWRs.

In order to study the influence of temperature gradient load on CRTS I double block ballastless track on a long-span continuous beam bridge of high-speed railway, a CWR calculation model is established based on the principle of beam-slab-rail interaction. The mechanical properties of track structure under vertical and transverse temperature gradient loads of track slab are analyzed, and the check value of the sleeper is used to study the influence of the two kinds of loads on the static height irregularity and track direction. Research results show that: The vertical temperature gradient load of track slab has relatively great influence on rail vertical displacement and medium and long wave height irregularity. The transverse temperature gradient load has a great influence on the lateral displacement of the rail. Compared with the load without temperature difference, the extreme value of lateral displacement increases by 121. 30% and 242. 59% respectively, when the temperature difference is 5 °C and 10 °C. With the increase of transverse temperature gradient load, the overall track deviation tends to increase. The height deviation of the beam end of the simply supported beam to the sunny side gradually decreases, and the height deviation of the back-shady side gradually increases, while the change rule of the beam end of the continuous beam is opposite. The transverse temperature difference load has a great influence on the track deviation. The transverse temperature difference mainly affects the distribution of the height deviation of the sunny and shady surfaces, and the magnitude of the temperature difference load directly affects the amplitude of the track deviation. The research results can provide reference for the design of CWR on bridge in the area with high temperature difference. [ABSTRACT FROM AUTHOR]

Linear guided wave based methods have been proposed to measure the axial load of continuously welded rail (CWR) in service. The underlying principle is that the propagation velocities of excited guided waves are sensitive to the axial load. However, the in-service CWR inevitably faces changes in rail wear and temperature, which also affects the propagating guided waves and results in severe degradation of existing methods. In this paper, we proposed the IGA-IWLS algorithm to estimate the axial load of in-service CWR using multiple guided wave modes. This novel load estimation method takes rail profile and phase velocities of a small set of wave modes as input, then uses an improved genetic algorithm to roughly search the candidate solutions of axial load and Young's modulus, and finally employs weighted least squares algorithm to iteratively converge to the estimated value of axial load. The paper presents the estimation theory in detail, including selection of the optimal set of guided wave modes and the IGA-IWLS algorithm. Numerical experiments show that the proposed method is able to estimate the axial load of CWR with an accuracy less than 2 MPa and is robust to measurement error and model error.

Abstract The technology of continuously welded rails (CWRs) is important in modern railway track structures. To measure rail stress, resistance strain gauges are preferred due to their good stability, sensitivity, and resistance to external interference. Based on the bi-directional strain method, we present a new method for measuring longitudinal rail stress using resistance strain gauges and develop a monitoring device for rail stress to realize long-term and multi-point measurement. Also relevant experimental verification and analysis are conducted. Results indicate that under various constraints the rail stress–strain values can be calculated just with the measured total longitudinal strain and total vertical strain. Considering the measurement error caused by sectional feature of sensors, we put forward a correction equation applicable to different stress conditions. Although the temperature values of the four full-bridge stress gauges can offset each other, the measurement error caused by rail flexural strain can also be eliminated to a certain extent at the same time, the non-uniform distribution of rail cross section temperature and unbalanced flexural strain still affect the measurement error. The experimental results also show that the developed rail-stress-monitoring sensor is suitable for measuring rail stress with reliable working performance.

Due to the rail-bridge thermal interaction, the high additional axial force in continuously welded rails on continuous bridges may lead to rail buckling or breaking. However, there is little research on the influence of the location of the fixed bearing of continuous beam on the additional force of rail. In order to study the influence of bridge bearing arrangement on the additional longitudinal force of CWR, the thermal interaction model is established for rail, and simple and continuous beams considering nonlinear stiffness and the methods are proposed to determine the locations of fixed bearings of continuous beams corresponding to the maximum additional forces in rail reaching minimum values. Multiple continuous beams with several different lengths and simple beams with three types of bearing arrangements are taken into account to find the effect laws of the locations of the fixed bearings of continuous beams on the maximum additional forces in rail. The results show that as long as the same number of continuous beams, the ratios of the distances of adjacent two fixed bearings to the distance between the two fixed bearings of the simple beams neighbour to the first and last continuous beams respectively are approximately equal to each other. Furthermore the appropriate locations of the fixed bearings of continuous beams are recommended. The results can guide designing the location of the fixed bearing of continuous railway bridge while reducing the additional axial force in continuously welded rails due to bridge thermal effect. [ABSTRACT FROM AUTHOR]

The thermal interaction of continuously welded rails with railway bridges has attracted the wide attention of researchers. In this paper, the model of a continuously welded rail and a bridge with longitudinal nonlinear stiffness has been considered. The detailed mechanics equation of the rail on the bridge and the embankment with longitudinal nonlinear stiffness has been presented using the finite element analysis. The validity of the presented model and the compiled program is illustrated. The influences of nonlinear stiffness, span number of the bridge, constant longitudinal restoring force, bridge bearing arrangement, and the span length of the bridge on the additional longitudinal stress and displacement of rails are investigated for multispan simply supported bridges. The results show that (1) the responses of rails for the nonlinear stiffness are less than those for the linear stiffness; (2) when the bridge span reaches a certain number, the maximum additional longitudinal stress and the displacement of the rail tend to be constant; (3) with the increase of the value of the constant longitudinal restoring stress, the maximum additional longitudinal stress and the displacement of the rail increase; (4) the maximum additional longitudinal stress of the rail on multispan simply supported bridges can be reduced by using alternate bearings on one pier; and (5) the maximum additional longitudinal stress and displacement of the rail increase with the increase of the span length of the bridge. [ABSTRACT FROM AUTHOR]

The key functions of the fastener system are to hold the rail against the sleepers and to restrain the rail from all forms of movements that could lead to loss of geometry and stability of the track. Thus, fastener resistance is an important parameter in the continuously welded rail technology. This study investigates the characteristics of the longitudinal resistance of WJ-8 fasteners subjected to varying torques and vertical loadings. The vertical loading was applied to the rail section through a reaction frame, while the torque was applied using a digital torque wrench. Two types of fasteners, conventional-resistance and small-resistance fasteners, were tested in this study. The study shows that: (1) The growth rate of the longitudinal resistance of the fastener is independent of the vertical loading until the fastener slips. (2) The slip resistance of fasteners increases as the torque and vertical loading are increased. (3) The relationship between the longitudinal resistance and the displacement of fasteners at varying torques and vertical loadings fits a power index function. (4) The relationship between the longitudinal resistance and the displacement of the fastener exhibits hysteresis. The study serves as a reference for verifying and improving future calculation methods for the longitudinal resistance of fasteners in continuously welded rails. [ABSTRACT FROM AUTHOR]

Due to the temperature change of bridges, there is a great additional force in continuously welded rails on continuous bridges. Laying rail expansion regulators is an effective measure to reduce the additional force. The nonlinear finite element model is presented for a continuously welded rail track with a rail expansion regulator resting on the embankment and simple and continuous beams, considering the temperature change of the bridge. Then, a method is proposed to determine the locations of the rail expansion regulator and the fixed bearing of the continuous beam, corresponding to the maximum additional forces of rail reaching minimum values. Their appropriate matching locations are recommended based on the obtained influence laws of any locations of the rail expansion regulator and the fixed bearing of the continuous beam on the maximum additional forces of rail. The results can provide the theoretical basis for the design of the rail expansion regulator and the fixed bearing of long-span continuous bridges. [ABSTRACT FROM AUTHOR]

The lateral resistance is one of the main functions of continuously welded rails that are influenced by various factors such as rail temperature, specifications of fastening systems, sleepers, ballast layer, the maintenance process of rails, etc. Nowadays, heavy haul and high-speed railways are operated under extremely complicated conditions, with the structure of the ballasted track and sleeper types also being constantly innovated. Therefore, research on the lateral resistance of ballasted tracks needs further investigation. In this paper, the ballasted track profile, the characteristics of the ballast aggregates, maintenance, and innovative sleepers were investigated and categorized to precisely examine the lateral behaviour of the ballasted tracks. In addition, the changes in the specifications of the abovementioned factors and components were also investigated. It was concluded that the geometry of the ballast layer and the interaction between the ballast and the sleeper are the main factors that led to the higher lateral resistance. In this regard, changes in the shape and type of sleepers as well as the ballast could increase the resistance. The influence of the loading frequency induced by trains and environmental conditions should be considered in further studies. [ABSTRACT FROM AUTHOR]

Copyright of Journal of South China University of Technology (Natural Science Edition) is the property of South China University of Technology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

To study the distribution and regularity of the longitudinal force of continuously welded rail on a railway bridge, a railway suspension bridge with a span of (84 + 84 + 1092 + 84 + 84) m is taken as the engineering background. Considering the main cable, suspender, steel truss, orthotropic plate and adjacent bridge structure, a model of the interaction between the suspension bridge and four-line tracks is established. Distribution patterns of the longitudinal forces on the suspension railway bridge with length exceeding 1000 m are explored. On this basis, the influences of design parameters on the longitudinal force are discussed. The results show that the track expansion force at the bridge end can be greatly reduced after the installation of rail expansion devices at the end of the suspension bridge. As the vertical stiffness of the suspension bridge is relatively low, the deflection force instead of the expansion force becomes the control load. When the four-line loading is simultaneously loaded, the vertical rail displacement is 2.4 m, and the track deflection stress is up to 103.0 MPa. The relative displacement between the suspension bridge and track is about 10.8 mm owing to the vertical load, which could cause the ballast track to buckle. [ABSTRACT FROM AUTHOR]

Due to the temperature change of bridges, there is a great additional force in continuously welded rails on continuous bridges. Laying rail expansion regulators is an effective measure to reduce the additional force. The nonlinear finite element model is presented for a continuously welded rail track with a rail expansion regulator resting on the embankment and simple and continuous beams, considering the temperature change of the bridge. Then, a method is proposed to determine the locations of the rail expansion regulator and the fixed bearing of the continuous beam, corresponding to the maximum additional forces of rail reaching minimum values. Their appropriate matching locations are recommended based on the obtained influence laws of any locations of the rail expansion regulator and the fixed bearing of the continuous beam on the maximum additional forces of rail. The results can provide the theoretical basis for the design of the rail expansion regulator and the fixed bearing of long-span continuous bridges.

The technology of continuously welded rails (CWRs) is important in modern railway track structures. To measure rail stress, resistance strain gauges are preferred due to their good stability, sensitivity, and resistance to external interference. Based on the bi-directional strain method, we present a new method for measuring longitudinal rail stress using resistance strain gauges and develop a monitoring device for rail stress to realize long-term and multi-point measurement. Also relevant experimental verification and analysis are conducted. Results indicate that under various constraints the rail stress-strain values can be calculated just with the measured total longitudinal strain and total vertical strain. Considering the measurement error caused by sectional feature of sensors, we put forward a correction equation applicable to different stress conditions. Although the temperature values of the four full-bridge stress gauges can offset each other, the measurement error caused by rail flexural strain can also be eliminated to a certain extent at the same time, the non-uniform distribution of rail cross section temperature and unbalanced flexural strain still affect the measurement error. The experimental results also show that the developed rail-stress-monitoring sensor is suitable for measuring rail stress with reliable working performance. [ABSTRACT FROM AUTHOR]

A new model is presented for the calculation of the rail extension, the friction created by sleeper fastenings and the temperature-induced stress for continuously welded rail (CWR) under free conditions and the calculation and analysis of temperature-induced stress when the temperature is changing and the rail is anchored. The mechanism for generating friction and the phenomenon of rail creep (extension) on site are used to establish a law that states that the friction force of the fasteners is distributed from the center of the CWR section towards the two ends in increasing scale; this observation is used to derive a formula for calculation of the distribution of the friction force in CWR fastenings. Formulas for calculating the temperature-induced stress and its distribution are also derived. The presented results show that the distribution of temperature-induced stress is cone-shaped in the absence of rail creep (extension), and with creep it presents a tangent and a cone shape in anchored sections. A comparison with the traditional temperature-induced stress distribution pattern in a rail of a tangent constitutes an argument against the established methods. The results reported in this paper should play an important role in guiding site maintenance activities. [ABSTRACT FROM PUBLISHER]

Considering arch rib, lateral brace, suspender, girder, pier and track position, the model for the interaction between long-span tied arch continuous bridge and multiple tracks was established by using steel-concrete composite section beam element to simulate concrete-filled steel tube (CFST) arch rib, using the beam element with rigid arm to simulate the prestressed concrete girder and using nonlinear bar element to simulate longitudinal constraint between track and bridge. Taking a (77+3×156.8+77) m tied arch continuous bridge with four tracks on the Harbin-Qiqihar Passenger Dedicated Line as an example, the arrangement of continuously welded rail (CWR) was explored. The longitudinal force in CWR on the tied arch continuous bridge, the pier top horizontal force and torque due to the unbalance load case, were analyzed under the action of temperature, vertical live load, train braking and wind load. Studies show that, it can significantly reduce track displacement to set the track expansion devices at main span arch springing on both sides; the track stress due to arch temperature variation can reach 40.8 MPa; the track stress, pier top horizontal force and torque are related to the number of loaded tracks and train running direction, and the bending force applied to unloaded track is close to the loaded track, while the braking force applied to unloaded track is 1/4 to 1/2 of the loaded track; the longitudinal force of track due to the wind load is up to 12.4 MPa, which should be considered. [ABSTRACT FROM AUTHOR]

Based on the large-mass method of multi-point excitation, the nonlinear bar element was used to simulate the beamtrack contact. The track-structure interaction model of simply-supported beams was established for the first time with considering the seismic traveling wave effect. Taking 5-32 m simply-supported beams on the Shanghai-Kunming line as a case, the impact of track on the seismic performance of the bridge was analyzed under traveling wave effect. The force law of the track and pier was studied, and the influence of parameters was discussed. Studies have shown that the seismic response of the beam and substructure increases greatly under the traveling wave effect; the track is extremely sensitive to the traveling wave effect; the lower the apparent velocity is, the larger the force exerted on the track and pier is; the bearing arrangement and the sudden change of the pier stiffness significantly affect the force of the adjacent piers; with the increase of the number of spans, the track and pier force gradually increase and approach a fixed value. [ABSTRACT FROM AUTHOR]

The article offers information regarding the seismic pounding effect between neighboring simply supported beams. It focuses on the influence of the continuously welded rail (CWR) during earthquakes including the seismic response of the railway bridge, yielding uneconomic design and neglecting the influence of seismic pounding on track forces. It discusses use of several numerical modeling methods including Large-mass method and Kelvin model.