Train Bridge Research Articles

Monitoring displacement, strain, and acceleration of a steel railway bridge

An evaluation of the existing steel railway bridge is necessary to obtain information in supporting policymakers to decide further strategies of the railway bridge maintenance process. The reliability and durability of the existing steel railway bridge were monitored regularly by installing instrumentations on the bridge. The railway bridge characteristics were reviewed by implementing a structural health monitoring system (SHMS). The advantages of the SHMS include an early warning system for the railway bridge structure in order to avoid failures. The objective of this study is to evaluate and monitor conditions of the railway bridge structure. The results of the study explained the vertical deflection of the railway bridge, the stress distribution of the entire truss, and the frequency that happens during loadings. This paper discusses and provides a recommendation to solve problems for users and necessary action in practice. This paper may be used by practicing engineers and researchers.

Dynamic Analysis of Train–Bridge Coupling System for a Long-Span Railway Suspension Bridge Subjected to Strike–Slip Fault

Long-span railway bridges crossing active faults are more vulnerable owing to the joint combination of pulse ground motions and surface dislocation. To study the dynamic effects resulting from the coupling of long-span railway suspension bridges crossing strike–slip fault and trains, a nonlinear model in which wheel–rail contact was established based on Hertz’s nonlinear theory and Kalker creep theory. To generate the ground motions across strike–slip fault, an artificial synthetic method, which considers both the fling-step effect with a single pulse and the directivity effect with multiple pulses, is employed. The effects of fault-crossing angles (FCAs) and permanent ground rupture displacements (PGRDs) are systematically investigated based on wheel–rail dynamic (derailment coefficient, lateral wheel–rail force, and wheel–load reduction rate). Conclusions are drawn and can be applied in the practical seismic design and train running safety assessment of long-span railway suspension bridges crossing strike–slip fault.

Influence of Variable Height of Piers on the Dynamic Characteristics of High-Speed Train–Track–Bridge Coupled Systems in Mountainous Areas

With the increase in the occupancy ratio of bridges and the speed of trains, the probability of trains being located on bridges during earthquakes increases, and the risk of derailment increases. To investigate the influence of unequal-height piers on the dynamic response of high-speed railway train bridge systems, a seismic action model of high-speed train–track–bridge dynamic systems was established based on the in-house code using the finite element method and multi-body dynamics method. It is found that (1) compared to equal-height piers, the peak lateral dynamic response of unequal-height piers (with gradually increasing pier heights) decreases, while the peak vertical dynamic response increases; (2) the peak lateral dynamic response of unequal-height piers (with a steep increase in pier height) increases sharply, while the peak vertical dynamic response decreases; and (3) the safety indicators of equal-height piers are significantly superior to the two unequal-height pier operating conditions.

Dynamic field load testing of a horizontally curved longspan LRT Kuningan bridge using eccentric mass vibrator and experimental modal analysis

Light Rail Transit (LRT) infrastructure in Indonesia is developing at a rapid pace. The LRT challenging construction is the Kuningan-Longspan Curved bridge with a span of 148 meters and the radius of curvature R = 115 meter. Therefore, Kuningan LRT Bridge is considered as one of the longest concretes curved balanced cantilever LRT Bridge in the world. The implementation of bridge regulations in Indonesia requires a functional feasibility test before the bridge is operational. In the case of the Kuningan LRT bridge, functional feasibility tests were carried out in the form of static and the dynamic tests. The dynamic load test aim is finding the structure natural frequency in the vertical, Longitudinal and Transverse direction. There are 3 methods that being used to measure the dynamic parameters of the train bridge structure in Indonesia. The first method is the Impulsive method using the moving train with the speed of 25 Km/hour as a load. The second method is the usage of The Experimental Modal Analysis and the third method is the combination method of Experimental Modal Analysis with a vibrating instrument in the form of an Eccentric Mass Vibrator (Exciter). The experiment results and the modal fem from the designer is compared and presented in this paper.

Stochastic analysis and dynamic reliability of the heavy-haul train–bridge system based on direct probability integral method

In this paper, a heavy-haul ballasted track–bridge interaction model is established by the finite element method in matrix representations, and their interaction to the train is achieved by the wheel–rail contact. A new direct probability integral method (DPIM) is introduced to achieve the stochastic analysis and reliability assessment of the train-ballasted track–bridge interaction (TTBI) system. Besides, the accuracy of the train-ballasted track–bridge model is validated by the field measurement. The probability characteristics of the dynamic behavior of the system are compared between DPIM and sophisticated PDEM, to show the accuracy and efficiency of the stochastic analysis method. The results demonstrated that the efficiency is improved by 1–2 orders of magnitude in terms of stochastic post-processing. Furthermore, the influences of random factors, e.g., track irregularity, axle loads and bridge parameters, etc., on the dynamic behavior of system are investigated by the proposed method, and the time-dependent reliability is presented with the aid of the extreme distribution events. The results indicate that the train axle load, running speed and variability of parameters have remarkable effects on dynamic performance. Besides, the failure probability of the bridge is very small attribution to the higher allowable threshold (e.g., mid-span displacement), but the safety of train operation decreases with the increase of vehicle speed especially under the critical speed of resonance.

Parametric Study on the Aerodynamic Characteristics of Wind Guide Barriers for a Train–Bridge System

This paper presents a new type of wind guide barrier (WGB). Through wind tunnel experiments, the key parameters of three types of WGB were studied, as well as their effects on the aerodynamic characteristics of a high-speed train and blunt body box girder system, while the bridge deck wind field was investigated. The results show that the shielding effect is the main factor affecting the windproof performance of the WGB. When the WGB is installed, the mean wind pressure distribution on the train is comparable to that of using a vertical wind barrier while reducing barrier resistance and the resistance of the bridge–barrier system. At the same time, the WGB can guide the oncoming flow, resulting in an increase in the streamwise and vertical wind velocity ratios on the bridge deck, as well as an increase in the maximum aerodynamic coefficient on the train.

Stochastic response analysis of uncertain train–bridge interaction system by stochastic pseudo excitation method

The stochastic pseudo-excitation method (SPEM) is applied to improve the efficiency of the random vibration analysis of an uncertain train–bridge interaction (TBI) system. This method is combined with the first-order reliability method to handle the reliability analysis of the system. It is characterized by the introduction of a random variable of the amplitude coefficient based on the principle of the PEM, establishing stochastic excitation at each selected frequency point. Unlike the traditional PEM, the calculation results by the SPEM can consider the random characteristics of external loads and also reflect the effect of uncertain parameters. Two comparisons were conducted to verify the accuracy and efficiency of the proposed method for the dynamic analysis of an uncertain TBI system. First, the results calculated using the SPEM were compared with those calculated using the PEM, indicating that the SPEM can calculate the dynamic responses of the TBI system without uncertainties. Second, the stochastic responses of the uncertain TBI system obtained by the SPEM were compared with those obtained by the MCM, which exhibited good agreement and verified the efficiency of the proposed method. Third, the system response of the simplified TBI model was analyzed to determine the parametric sensitivity. Finally, the reliability of the TBI model was studied based on the selected sensitive parameters. These results indicated that the uncertain mass of the train played an essential role in the random vibration of the system. In addition, the safety index of the structure became more accurate with increasing number of samples, and the probabilistic distribution of the dynamic responses of the uncertain TBI system followed a Gaussian distribution extremely well, further verifying the appropriateness of the selected amplitude coefficient in the SPEM.

A Scalable Multiple-Time-Step Efficient Numerical Algorithm for Wind–Road Vehicle–Train–Bridge Dynamic Simulations

During the past two decades, more and more rail-cum-road bridges have been built to meet the ever-increasing demand of highway and railway transportation in China. The rail-cum-road bridges are expected to withstand multiple types of loadings during normal operation, including wind, road vehicle, and train. Accurate quantifications of the coupling dynamics among bridge, road vehicle, and train are essential to ensure the safety and reliability of rail-cum-road bridges during their lifetime. The present study develops an analytical framework to simulate the complex wind–road vehicle–train–bridge (WRVTB) system. In addition, a scalable multiple-time-step (SMTS) algorithm is proposed to overcome the computational efficiency issue of traditional single-time-step (STS) algorithms for solving the WRVTB interaction. The SMTS algorithm utilizes domain decomposition techniques to enable a fine and a coarse time-step to be assigned for a road vehicle–train subsystem and bridge subsystem, which greatly improves the computational efficiency for solving the WRVTB interaction. A numerical simulation of coupled WRVTB analysis is conducted based on a prototype rail-cum-road bridge to demonstrate the computational efficiency and accuracy of the proposed method. The results indicate that both the MTS and the SMTS algorithms are able to achieve better accuracy and efficiency simultaneously in comparison with the STS algorithm. Although the SMTS algorithm does not exhibit obvious superiority over the MTS algorithm in terms of the overall accuracy and computational efficiency, the major advantage of the proposed SMTS algorithm over the MTS algorithm is the flexibility. When the SMTS algorithm is adopted, a refined time-step can be assigned to a subsystem of interest, while relatively coarse time-steps can be assigned to the remaining subsystems. As such, the desired accuracy of the subsystem of interest is guaranteed at a low computational cost.

Deformation mapping between pier settlement and maglev track for high-speed multi-span simply supported maglev bridge

When a bridge pier settles, deformation of the complex coupling between a maglev track and girders may occur because of the disparity between the continuity of the maglev track and discontinuity of the simply supported girder bridge. This introduces additional irregularity to the track, resulting in the combined vibration of the maglev train–bridge system. In this study, a high-speed maglev track–simply supported bridge is considered as the research object. The deformation characteristics of the maglev track caused by the pier settlement are analysed. First, the mapping relationship between the settlement of a single pier and the deformation of the maglev track is theoretically deduced. Then, an analytical model for the deformation of the maglev track is developed. The model is compared with a finite element model and found to have sufficient accuracy. The additional irregularity of the maglev track includes the rigid displacement caused by pier settlement and the elastic displacement influenced by the track and girder. The elastic deformation of the longitudinal beam of the maglev track is the main component of the deformation in the vertical displacement of the maglev track. Based on the established analytical model, the elastic deformation of the longitudinal beam of the maglev track and its main influencing factors are further examined.

Dynamic Analysis of Coupled Train and Cracked Bridge Systems Using Multiscale Finite Element Modeling

Cracking frequently encountered in railway bridges can lead to significant changes in bridge dynamic characteristics and further dynamic performance of train–bridge interaction (TBI) system. It is desirable to develop an effective method to understand the dynamic behavior of coupled train and cracked bridge systems. This paper proposes a framework for coupled vibration analysis of train and cracked bridge systems using multiscale finite element modeling. A multiscale bridge model adopting frictional surface–surface contact to characterize nonlinear breathing phenomenon of the crack is incorporated into the three-dimensional coupled TBI model. Subsequently, a multiloop numerical solution strategy is formulated to solve the established dynamic equation of coupled train and cracked bridge systems. The proposed framework is used to analyze the cracked beams presented in the literature, and the obtained and literature data are compared. Moreover, an actual heavy-haul railway bridge is taken as an illustrative example, in which vehicle dynamic response, bridge vibration, and train running safety index are calculated considering various crack types, train speeds, and track conditions. The results show that apart from the bridge displacement and acceleration, the presence of crack can have a large influence on the vehicle acceleration response, derailment factor, and offload factor. Differences larger than ±10% in the maximum dynamic indices associated with the intact and cracked bridges are observed, indicating the necessity of considering the crack damage in train–bridge coupled dynamic analysis.

A New Method for Separating Temperature Effect of Bridge Strain Monitoring

Temperature has a significant influence on bridge strain monitoring data. To improve the accuracy of temperature effect separation in strain monitoring data, this paper proposes a temperature effect separation method comprising variational nonlinear chirp mode decomposition (VNCMD), principal component analysis (PCA) and blind source separation. Firstly, VNCMD was used to decompose the monitoring data of strain and temperature, and the intrinsic mode functions (IMF) of strain and temperature signals were obtained. Secondly, PCA was used to reduce the dimension of IMF, and the false components were eliminated to select the optimal components. After reducing the dimension, the components were used as the input of fast independent component analysis model for blind source separation. Finally, the feasibility and accuracy of the method was verified via the signal-to-noise ratio (SNR) in the simulated signal, and the separation results were evaluated using the Pearson correlation coefficient between the strain component and the corresponding temperature component in real bridge monitoring data. The proposed method performed better than the empirical mode decomposition (EMD) method. The signal-to-noise ratio (SNR) of VNCMD improved 51.80% for daily temperature difference effect and 32.41% for annual temperature difference effect in the numerical study, respectively; the correlation coefficients of VNCMD improved 52.90% for daily temperature difference effect and 4.26% for annual temperature difference effect in practical verification, respectively.

Wheel–rail contact model for railway vehicle–structure interaction applications: development and validation

An enhancement in the wheel–rail contact model used in a nonlinear vehicle–structure interaction (VSI) methodology for railway applications is presented, in which the detection of the contact points between wheel and rail in the concave region of the thread–flange transition is implemented in a simplified way. After presenting the enhanced formulation, the model is validated with two numerical applications (namely, the Manchester Benchmarks and a hunting stability problem of a suspended wheelset), and one experimental test performed in a test rig from the Railway Technical Research Institute (RTRI) in Japan. Given its finite element (FE) nature, and contrary to most of the vehicle multibody dynamic commercial software that cannot account for the infrastructure flexibility, the proposed VSI model can be easily used in the study of train–bridge systems with any degree of complexity. The validation presented in this work proves the accuracy of the proposed model, making it a suitable tool for dealing with different railway dynamic applications, such as the study of bridge dynamics, train running safety under different scenarios (namely, earthquakes and crosswinds, among others), and passenger riding comfort.

Dynamic Interaction Analysis and Running Safety Assessment of the Wind–Train–Bridge System Considering the Moving Train’s Aerodynamic Coupling with Crosswind

Trains tend to be faster and lighter to meet the increasing public travel needs and interact with crosswind to produce a strong aerodynamic interaction, leaving a safety hazard for the operation. This paper presents a study into the dynamic response and running safety of the train–bridge system accounting for this aerodynamic interaction. The threedimensional flow features of a moving train in crosswinds are first investigated by a computational fluid dynamics method, and then an aerodynamic model for simulating unsteady crosswind force is developed. Furthermore, the dynamic responses of the train and bridge are calculated by using a wind–train–bridge dynamic interaction equation, and finally, the characteristic wind curve and surface are defined to evaluate the train’s running safety. The results show that the lateral response of the train–bridge system significantly increases as the crosswind increases, and the head car can experience a high derailment risk and determine the running safety of the train due to the aerodynamic coupling effect of a moving train and crosswind. Variations in the wind direction need to be factored into the safety assessment for low train speeds, and the train is at greater danger when the crosswind appears perpendicular to the car body.

An Improved Approach for Grasp Force Sensing and Control of Upper Limb Soft Robotic Prosthetics.

The following research proposes a closed loop force control system, which is implemented on a soft robotic prosthetic hand. The proposed system uses a force sensing approach that does not require any sensing elements to be embedded in the prosthetic's fingers, therefore maintaining their monolithic structural integrity, and subsequently decreasing the cost and manufacturing complexity. This is achieved by embedding an aluminum test specimen with a full bridge strain gauge circuit directly inside the actuator's housing rather than in the finger. The location of the test specimen is precisely at the location of the critical section of the bending moment on the actuator housing due to the tension in the driving tendon. Therefore, the resulting loadcell can acquire a signal proportional to the prosthetic's grasping force. A PI controller is implemented and tested using this force sensing approach. The experiment design includes a flexible test object, which serves to visually demonstrate the force controller's performance through the deformation that the test object experiences. Setpoints corresponding to "light", "medium", and "hard" grasps were tested with pinch, tripod, and full grasps and the results of these tests are documented in this manuscript. The developed controller was found to have an accuracy of ±2%. Additionally, the deformation of the test object increased proportionally with the given grasp force setpoint, with almost no deformation during the light grasp test, slight deformation during the medium grasp test, and relatively large deformation of the test object during the hard grasp test.

Nonlinear Dynamic Analysis of the Wind–Train–Bridge System of a Long-Span Railway Suspension Truss Bridge

In order to study the coupling vibration between a bridge and a train under the action of crosswind loads, a dynamic interaction model of the wind–train–bridge system is established considering the geometric nonlinear factors of a long-span suspension bridge. A calculation frame is composed, and a corresponding computer program is written. A long-span highway–railway suspension bridge scheme is studied as an example. The linear and nonlinear vibration responses of the bridge under the simultaneous action of both train loads and wind loads are compared using the self-written program, and the influence of wind velocity and train speed on the dynamic responses of the bridge is studied. The results show that the large displacement nonlinearity of the structure does not influence the changing tendency of bridge displacement and acceleration time histories, but reduces the maximum values of the responses. The geometric nonlinear influence on the bridge accelerations is more obvious than that on the displacements. The natural frequencies of this long-span suspension bridge are very low and it is sensitive to wind action. The changes in train speed and average wind velocity have a great influence on the maximum value of bridge displacement, especially when the lateral deformation and acceleration increase sharply with the wind velocity, and the coupling vibration between wind, train, and the bridge can easily occur. The research results can provide references for the safe operation and maintenance of long-span bridges.

Multiple Damaged Cables Identification in Cable-Stayed Bridges Using Basis Vector Matrix Method

A new damaged cable identification method using the basis vector matrix (BVM) is proposed to identify multiple damaged cables in cable-stayed bridges. The relationships between the cable tension stiffness and the girder bending strain of the cable-stayed bridge are established using a force method. The difference between the maximum bending strains of the bridges with intact and damaged cables is used to obtain the damage index vectors (DIXVs). Then, BVM is obtained by the normalized DIXV. Finally, the damage indicator vector (DIV) is obtained by DIXV and BVM to identify the damaged cables. The damage indicator is substituted into the damage severity function to identify the corresponding damage severity. A field cable-stayed bridge is used to verify the proposed method. The three-dimensional finite element model is established using ANSYS, and the model is validated using the field measurements. The validated model is used to simulate the strain response of the bridge with different damage scenarios subject to a moving vehicle load, including one, two, three, and four damaged cables with damage severity of 10%, 20%, and 30%, respectively. The noise effect is also discussed. The results show that the BVM method has good anti-noise capability and robustness.

Seismic analysis of 3D train–wheel–bridge–bearing systems: Modeling

AbstractBearing effects have not been deeply investigated in the dynamic analysis of a train–bridge coupled system subjected to earthquake motions, and existing studies on base isolation of railway bridges have typically not considered the running train. To fill these gaps, this paper develops the numerical model of a three‐dimensional train–wheel–bridge–bearing (TWBB) system for seismic analysis. The substructuring method is implemented to separate the TWBB system into the train, wheel–rail, bridge and bearing subsystems, and couple them using state‐space representations. The complete model of the TWBB system has three main features: fewer degrees of freedom (DOF) than traditional finite element methods, applicability to different types of bearings, and simplicity as no iterations in the simulation are required. Therefore, the proposed procedure demonstrates that the TWBB model is an efficient and flexible representation to obtain and predict realistic demands for engineering purposes.

Buffer scheme for aero-performance deterioration caused by trains passing bilateral vertical noise barriers with crosswinds

Bilateral vertical noise barriers have been widely used along high-speed railway lines in coastal cities where typhoons are frequent. When a high-speed train (HST) enters (or exits) a noise barrier under strong crosswind conditions, its running safety will be more severely tested because of the instantaneous switching of aerodynamic environment. Installing a buffer structure at the end of the noise barrier is necessary to ensure the running safety of HSTs. In this study, two types of aerodynamic buffer structures (triangle and fence types) for the end of the noise barrier are proposed. The buffering effects of the two structures on the sudden change amplitude of the aerodynamic load of the carriage are compared by using an improved delayed detached eddy simulation method. The difference in the influence of the two buffer structures on the aerodynamic responses of the carriage is discussed by using a wind–train–bridge coupling dynamic response calculation method. The buffer mechanisms of the two structures are revealed in terms of the flow field. Results show that the buffering effect of fence type is superior triangle type, and the buffer length of 4 L is the most reasonable.

Train–Track–Bridge Dynamic Interaction on a Bowstring-Arch Railway Bridge: Advanced Modeling and Experimental Validation

This article describes the validation of a 3D dynamic interaction model of the train-track-bridge system on a bowstring-arch railway bridge based on experimental tests. The train, track, and bridge subsystems were modeled on the basis of large-scale and highly complex finite elements models previously calibrated on the basis of experimental modal parameters. The train-bridge dynamic interaction problem, in the vertical direction, was efficiently solved using a dedicated computational application (TBI software). This software resorts to an uncoupled methodology that considers the two subsystems, bridge and train, as two independent structures and uses an iterative procedure to guarantee the compatibility of the forces and displacements at the contact points at each timestep. The bridge subsystem is solved by the mode superposition method, while the train subsystem is solved by a direct integration method. The track irregularities were included in the dynamic problem based on real measurements performed by a track inspection vehicle. A dynamic test under traffic actions allowed measuring the responses in the bridge, track, and vehicles, which were synchronized by GPS systems. The test results demonstrated the occurrence of upward displacements on the deck, which is a characteristic of structures with an arch structural behavior, as well as an alternation of tensile/compressive stresses between the rail and deck due to the deck-track composite effect. Furthermore, the acceleration response of the bridge proved to be significantly influenced by the train operating speed. The validation procedure involved comparing the dynamic responses obtained from the train-bridge interaction model, including track irregularities, and the responses obtained experimentally, through the test under traffic actions. A very good correlation was obtained between numerical and experimental results in terms of accelerations, displacements, and strains. The contributions derived from the parametric excitation of the train, the global/local dynamic behavior of the bridge, and the excitation derived from the track irregularities were decisive to accurately reproduce the complex behavior of the train-track-bridge system.

An adaptive surrogate model approach for random vibration analysis of the train–bridge system

To improve the efficiency of random vibration analysis of the train–bridge system, a new approach is proposed based on the adaptive sampling (AS) surrogate model in this paper. First, an initial sample set and a candidate sample set are generated by the method based on Generalized F (GF)-discrepancy. Second, a theoretical model is used to calculate the maximum dynamic response of the train–bridge system corresponding to the initial sample set, and a surrogate model based on Gaussian process regression (GPR) is constructed. Third, the learning function is used to identify new samples in the candidate sample set to optimize the current surrogate model until it meets satisfactory prediction accuracy. Finally, the maximum dynamic response of each sample in the representative sample set is predicted by the final surrogate model, and then the statistical properties of the dynamic response of the train–bridge system are analyzed. To verify the effectiveness of the proposed method, the distribution of training sample points and prediction accuracy of the AS surrogate model and the one-stage sampling (OS) surrogate model are compared and analyzed, taking the prediction of the maximum wheel load reduction rate (WLRR) of a train on the bridge as an example. On this basis, the prediction accuracy of the AS and OS surrogate models for the random characteristics of the train on the bridge is evaluated. The results show that the proposed method can significantly improve the prediction accuracy of the surrogate model without increasing the number of training samples.