High-speed Railway Bridge Research Articles

Dynamic responses of a train-track-bridge coupled system under earthquakes

The probability of a train running over a bridge when an earthquake occurs is increasing with the total mileage of China’s high-speed railway network expanding. To study this issue, a three-dimensional train-track-bridge dynamic interaction system subjected to seismic excitations is established based on commercial mathematical software. Besides, a set of motion equations of the system are derived according to the multibody dynamics, the finite element method theory and the bridge seismic theory. Moreover, in order to study the dynamic response of high-speed railway bridges under earthquake, a series of experiments are conducted on a scaled high-speed railway simple supported bridge model with a ballastless track slab excited by shaking table tests. Meanwhile, the strain of rails, track slabs, base plates and girder in various working conditions are measured by quasi-distributed optical fiber sensing stuck in bridge members. At last, the dynamic response of each structure member is demonstrated in the time and frequency domains. Furthermore, the seismic isolation performance of bridge members, such as fasteners, cement asphalt (CA) mortar layer and so on, is explained in details.

Damage Detection of Spatial Track–Bridge System with Interlayer Connection Using High-Speed Train Response and Sensitivity Analysis

Bridge damage detection has attracted much attention recently. Most studies on damage detection of the high-speed railway (HSR) bridge neglect the effect of the interlayer connection between the railway track and bridge. This paper proposes a damage detection method for the HSR bridge using response-based sensitivity analysis of high-speed trains. The HSR bridge is modeled as a spatial track–bridge system, in which the fasteners, sleepers and track slabs are modeled as one viscoelastic layer. The responses of multiple vehicles are merged to overcome the critical issue that the length of response data recorded by a high-speed vehicle moving over the bridge is too short to perform the sensitivity analysis. Numerical studies demonstrate that the proposed method is capable to detect damages of the track–bridge system with different train speed, car-body mass, irregularity grade and the interlayer connection properties. By using the signal merging method and the averaged response from multiple train trips, the proposed method is robust to high speed and measurement noise. The damage on the bridge beam and the interlayer connection can be well-identified. It is also found that increasing the car-body mass, damping ratio of the track–bridge system, damping coefficient of interlayer connection could improve the efficiency of damage detection.

Random analysis of train-bridge coupled system under non-uniform ground motion

The increasing prevalence of simply supported bridges in high-speed railway (HSR) lines has raised concerns about the safety of trains crossing these bridges during an earthquake. As these bridges are typically continuous and long, it is essential to consider the effects of traveling seismic waves on the random vibration of the train-bridge coupled (TBC) system. To address this issue, the new point estimate method (NPEM) is used to analyze the dynamic response and parametric sensitivity of a three-dimensional TBC system subjected to non-uniform ground motion with multiple random parameters. The motion equations of the TBC system are derived using bridge seismic theory under multi-support excitations. The analysis incorporates random variables such as the damping ratio, density, Young’s modulus, and seismic magnitude to capture the influence of traveling seismic waves on the random vibration of the TBC system. Simulation results show that the traveling seismic wave effect can cause changes in the first vibration frequencies of the train and bridge, potentially leading to the first few frequencies reordering. Additionally, considering the traveling wave effect will make the TBC system’s response less apparent than without considering the traveling wave effect. The uncertainty of bridge and seismic parameters can seriously affect the train’s running safety. The sensitivity of the bridge density and seismic magnitude is particularly prominent for bridge responses when the traveling seismic waves effect is strong. This methodology can be used for random and sensitivity analysis of a train running over a long bridge under non-uniform earthquake conditions. Overall, the NPEM can provide valuable insights into the dynamic behavior and safety of TBC systems, enabling more effective design and maintenance of HSR bridges.

Local Track Irregularity Identification Based on Multi-Sensor Time–Frequency Features of High-Speed Railway Bridge Accelerations

Shortwave track diseases are generally reflected in the form of local track irregularity. Such diseases will greatly impact the train–track–bridge interaction (TTBI) dynamic system, seriously affecting train safety. Therefore, a method is proposed to detect and localize local track irregularities based on the multi-sensor time–frequency features of high-speed railway bridge accelerations. Continuous wavelet transform (CWT) was used to analyze the multi-sensor accelerations of railway bridges. Moreover, time–frequency features based on the sum of wavelet coefficients were proposed, considering the influence of the distance from the measurement points to the local irregularity on the recognition accuracy. Then, the multi-domain features were utilized to recognize deteriorated railway locations. A simply-supported high-speed railway bridge traversed by a railway train was adopted as a numerical simulation. Comparative studies were conducted to investigate the influence of vehicle speeds and the location of local track irregularity on the algorithm. Numerical simulation results show that the proposed algorithm can detect and locate local track irregularity accurately and is robust to vehicle speeds.

A velocity-related running safety assessment index in seismic design for railway bridge

With the rapid expansion of the high-speed railway (HSR) network, high-speed train running safety (TRS) over bridges is increasingly highlighted in the world. Previously, spectral intensity (SI) was proposed and considered as a performance-based index for discussing TRS over HSR bridges in seismic design. However, the speed independence of the conventional SI index greatly limits its rationality and generalisation in the performance-based bridge design under earthquake. To this end, the velocity-related SI index is proposed for the first time and improves the limitations of the conventional index in this research. The discrepancy between the proposed SI and the conventional SI is explained theoretically, and the correlation between the proposed SI and train running speed is illustrated in detail. Additionally, a series of scale model experiments are conducted to validate the feasibility of the train-bridge coupled (TBC) system. The probability analysis of the proposed SI index is presented to help discuss the randomness and economy of HSR bridges. Furthermore, systematic parametric analyses are finished by taking the train running speed as the kernel parameter based on the TBC model. The simulation results show the conventional SI index unduly neglected the velocity-induced vibration of the train under an earthquake. Within the common train running speed range, the proposed SI indices have the same varying pattern with the derailment factors and are comprehensively larger than the conventional SI indices. The vibration induced by train speed seriously threatens TRS under earthquake, but it was ignored in the seismic design for the HSR bridge before.

Combined Prediction Model for High-Speed Railway Bridge Pier Settlement Based on Robust Weighted Total Least-Squares Autoregression and Adaptive Dynamic Cubic Exponential Smoothing

Combined Prediction Model for High-Speed Railway Bridge Pier Settlement Based on Robust Weighted Total Least-Squares Autoregression and Adaptive Dynamic Cubic Exponential Smoothing

Seismic performance of precast hollow concrete bridge double columns with shallow socket connection

In this paper, a precast hollow concrete bridge double column with shallow socket connection (PHCBDCSS) is proposed for reducing the socket depth and achieving rapid construction of high-speed railway bridge structures. To investigate the mechanical properties and reliability of the PHCBDCSS under earthquake excitations, full-scale pier in-situ pseudo-static test and numerical simulation of a practical high speed railway PHCBDCSS are performed. Accordingly, the damage state and damage characteristics of PHCBDCSS are analyzed, and the seismic performance is assessed in terms of strain distribution, hysteresis curve, stiffness degradation and ductility, as well as the sensitivity of spigot and socket connection piers to the stiffness of spliced joints is revealed. The results show that the socket connection of PHCBDCSS can effectively and reliably transfer the applied load, which meets the design requirements. Similar to the cast-in-place integral pier, the failure mode of PHCBDCSS is a typical plastic hinge bending failure. Moreover, PHCBDCSS and cast-in-place integral pier have good plastic deformation capacity, bearing capacity and member ductility. The key points of the pier hysteresis curve obtained from fiber element simulation are in accordance with the test results. When the ratio of connection joints' stiffness to pier columns' stiffness exceeds 10, the mechanical properties of the socket connection pier and the cast-in-place integral pier are similar.

Influence of Track Typology on the Dynamic Response of Short-Span High-Speed Railway Bridges

It is known that short-span high-speed railway viaducts are prone to suffer significant dynamic effects due to the passage of moving train loads. Recent technological advances in railway engineering have resulted in track typologies different from the conventional ballasted track consisting of discrete sleepers fastened to the rails and resting on a ballast bed. In particular, ballastless track has been identified as an effective solution due to reduced maintenance costs, high track stability and excellent geometric quality. Though different track typologies are available in the market, they can be classified as monolithic or independent according to the interaction degree with the bridge girder. In the present paper, the dynamic behaviour of short-span bridges is numerically studied by taking into account the track-bridge interaction by modelling explicitly the components of the track. Two types of ballastless track (monolithic continuous slab and independent short slabs) and conventional ballasted track are considered on simply supported bridges with span length in the range of 15-25 m subjected to envelope and commercial train loads at speeds between 200 and 360 km/h. In total, 2448 numerical cases have been analyzed. The study shows that dynamic deflections and accelerations produced at the bridge girder by moving train loads can be reduced when the ballasted track is replaced to ballastless track systems, especially for the critical speeds higher than 300 km/h. Moreover, it is shown that the two ballastless track systems lead to very similar results, with the monolithic system resulting in slightly smaller bridge deflections and also moderately larger accelerations.

Study on the seismic influence coefficient of track irregularity on the train dynamic effect of high-speed railway bridge

Track irregularity is an important factor affecting the train-track-bridge system interaction, and for the seismic design of the track-bridge system, the study of the law of the influence of track irregularity on the train dynamic effect is of great theoretical significance. Based on this, the finite element models of China railway track structure (CRTS) II plate high-speed railway simple-supported girder bridge and CRH2C high-speed train model are developed and compared with the shaking table test results to verify their validity. Considering track irregularity and earthquake randomness, a sample library of the train dynamic effect of the track-bridge system under earthquake is established, the probabilistic statistical characteristics of the train dynamic effect are analyzed, and the influence level of track irregularity on the train dynamic effect of the track-bridge system under earthquake is studied, and the standard value of track irregularity influence coefficient of train dynamic effect based on probability guarantee rate is proposed. The results indicate that: the influence of track irregularity on the seismic response of bridge structure is slight, with their greatest impact not exceeding 1%. However, it has a significant impact on the seismic response of track structures. The standard values of the sliding and mortar layers’ track irregularity influence coefficients are 1.49 and 1.71, respectively, at 0.1 g. Under various peak ground acceleration (PGA) settings, the fasteners’ standard values for the track irregularity influence coefficient are less than 1.1. Additionally, the degree of influence of track irregularity on the seismic response of track structure decreases significantly as the PGA increases.

Fatigue Characteristics of Long-Span Bridge-Double Block Ballastless Track System

The key issues in designing ballastless track for high-speed railway bridges are to reduce maintenance and improve track smoothness by understanding fatigue damage characteristics. This paper is based on the principle of bridge-rail interaction and train-track-bridge coupling dynamics, the refined simulation model of bridge-CRTS I Bi-block ballastless track system is established by using the finite element method. The longitudinal force distribution law of CWR (Continuously Welded Rail) and the dynamic response characteristics of coupling systems are studied, based on the Miner rule and S-N curve. The fatigue characteristics of ballastless track system laying on long-span bridge under the dynamic train load and the effect of ballastless track system design parameters changes on fatigue characteristics are discussed. The results show that the extreme values of longitudinal force of CWR all appear in the middle of the bridge span or near the bridge bearing, and attention should be paid to the strength checking of CRW laying on long-span bridge. Under the dynamic train load, the fatigue life curve of rail on the bridge is relatively smooth and the minimum life of rail which is laying on continuous bridge decreases from 27.1 years to 17 years that which is laying on cable-stayed bridge. The life curve of track plate laying on continuous bridge is relatively smooth, and the life curve of track plate laying on cable-stayed bridge is related to the stiffness of elastic cushion, which decreases in a stepped manner, and there will be no fatigue failure on the track plate during service. The life curve of the baseplate is related to the type of bridge, the minimum life value of the baseplate appears near the bridge bearing, and there will be no fatigue failure on the baseplate during service. Increasing the stiffness of elastic cushion can effectively improve the fatigue life of track plate, and increasing the vertical stiffness of fasteners can enhance the connection between rail and track plate and improve the fatigue life of rail. The increase in train speed will increase the dynamic stress amplitude of track structure and reduce the fatigue life of the rail.

Analysis on Reliability of Wind Barrier on High-speed Railway Bridge under Wind Load

In order to guarantee the safety of wind barrier structure on the railway bridge and to prevent the overturning of wind barrier in the strong wind impacting on the normal operation of the train, the study on reliability of wind barrier is conducted. Taking the single side 4m wind barrier installed on the Lanzhou-Xinjiang second double-line railway bridge as an example, considering the randomness of natural wind velocity and train speed, based on the probabilistic theory analyze the reliability of the wind barrier structure system under the static wind load and dynamic wind load, and evaluate the wind barrier safety with the reliability index and failure probability of structural system. And parameter sensitivity analysis is performed to find out which factors are more important to the reliability of the wind barrier system. The research results show that the reliability index of the wind barrier system meets the requirements of the design specification, and the failure probability is small; the reliability index of the wind barrier system under the static wind load and dynamic wind load is more sensitive to the wind velocity than the train speed.

Extended harmonic input method for response spectrum determination of vehicle–bridge systems

The calculation of response power spectral densities (PSDs) from the excitation PSDs of vehicle–bridge (VB) systems is crucial for the safety evaluation of operating vehicles, bridge fatigue analysis, and vibration control optimization. However, calculations using the available methods result in considerable computational errors when applied to evaluate the response PSDs of VB systems. Hence, an extended harmonic input method (HIM) is proposed to compute the time-varying response spectrum in VB systems. First, the unique characteristics of VB systems that may cause the inapplicability of conventional methods are systematically analyzed. Subsequently, an extended version of the HIM is mathematically established to calculate the time-varying response spectrum of VB systems via the representation of inputs and decomposition of responses. Finally, a numerical example of an actual high-speed railway bridge subjected to track irregularities or seismic excitations is presented to illustrate the efficacy of the novel method.

Seismic response of concrete bridge of Lanzhou-Xinjiang high-speed railway under the near-fault strong earthquake

The MS6.9 earthquake in Menyuan, Qinghai, on January 8, 2022 caused severe damage to Sulphur Gully Bridge of Lanzhou-Xinjiang high-speed railway. In this paper, a two-dimensional numerical model of the structure and site soil is established with Sulphur Gully Bridge as the research object, and finite element dynamic time analysis is used to study the dynamic response characteristics of the box girder, pier, pile foundation and site of Sulphur Gully Bridge under ground motion loads. The results show that the peak acceleration in the pile and bridge superstructure system as a whole decreases linearly with height, the horizontal peak displacement of the bridge pile-superstructure system decreases linearly with height, and the peak displacement of the soil site as a whole gradually decays linearly as it is amplified farther from the bridge, and the horizontal peak displacement in the direction of the source is smaller than that of the site further away; the difference between the vertical peak displacement and the horizontal peak displacement is the difference between the vertical peak displacement and the horizontal peak displacement is about 5–13.6 times; the vertical peak displacement of the middle of the bridge pier and the pile changes very little as the height decreases, and the vertical peak displacement of the soil layer site as a whole gradually decays as the distance from the bridge is enlarged; the ground motion frequency of the bridge is mainly concentrated in 1–10 Hz, and the main frequency is distributed in 2 Hz, the peak Fourier spectrum of ground motion in the pile-superstructure system tends to decrease as the height decreases, and the peak Fourier spectrum of ground motion is the relationship is: box girder > abutment > soil site > pile; the relationship between the peak of ground motion energy spectrum of bridge is: pile > soil site > abutment > box girder.

Comparison of the Differences in Impact Factor according to Loading Conditions in the Evaluation of Load Carrying Capacity of a High-speed Railway PSC BOX Girder Bridge

In this study, the load carrying capacity was evaluated using the results of the dynamic load test, instead of the static load test of the field, in the precision safety diagnosis of a high-speed railway PSC BOX girder bridge, and the differences in the impact factor of the bridge according to the load condition of the train and the configuration of the bridge were compared. The impact factor of the bridge was obtained from the measured displacement response via static and dynamic tests for the precision safety diagnosis performed on high-speed railway bridges. The analysis conditions included the location of the sensor, running track of the train, type and span of the bridge, and load condition of the dynamic load test train, test running train, and service train. Consequently, when the impact factor was calculated based on the displacement response of the test running train, instead of the static load test in the load capacity evaluation of the bridge, a difference of -4.96-5.93% was obtained in comparison with the calculation based on the displacement response of the static load test; this corresponds to 0.943-1.053 times the basic load-carrying capacity rate, indicating a difference from the load-carrying capacity rate obtained by the static load test.

Seismic evaluation method on shear strength models for round-end hollow piers of high-speed railway bridges

Round-end hollow pier has been widely used in China's high-speed railway (HSR) lines. Experimental studies have shown that the HSR round-end hollow pier may experiece bending shear failure in the transverse direction of bridge, which is a brittle failure. Although it is of great significance to clarify the shear strength model for HSR round-end hollow piers, their seismic shear performance and failure mode criterion are still unclear. Considering the existing seismic design codes of bridges are mostly applicable to ordinary bridge components, this paper proposes a shear strength model for HSR round-end hollow piers based on the truss model limiting equilibrium theory, and quasi-static test results. According to the proposed shear strength model, a bending-shear coupling numerical pier model was established using OpenSees. Then the accuracy of the proposed shear strength model is verified. The study results show that the proposed shear strength model can accurately obtain the shear strength of HSR round-end hollow piers compared with other evaluation methods. Besides, the numerical simulation results illustrate that the HSR round-end hollow pier is not prone to damage under the design seismic excitation. Corresponding to the extreme seismic excitation with the peak ground acceleration of 0.75 g, the HSR round-end hollow pier experiences bending shear failure, which can be accurately determine by the proposed shear strength model.

Influence of damping on seismic-induced track geometric irregularity spectrum in high-speed railway track-bridge system

Track irregularities are an important factor affecting the safety, smoothness, comfort, and lifespan of high-speed railway track structures. Damping greatly affects the seismic response, and the influence of damping on seismic-induced track geometric irregularities is of significant interest. In this study, the simple-supported beam bridge of the CRTS-II ballastless track high-speed railway was adopted as the research object. A power spectral density curve spectrum of seismic-induced track geometric irregularity based on guarantee rate was established, and the influence of structural damping ratio on the power spectral density curve under different earthquake intensities was analysed. A simplified calculation method for power spectral density curve of seismic-induced track geometric irregularity was proposed. The main findings of this work are as follows: (1) Seismic-induced track irregularities of high-speed railway bridges are dominated by alignment irregularity, and a segmented polynomial function can be fitted to the power spectral density curve of the seismic-induced track irregularity based on guarantee rate; (2) Seismic-induced track irregularities of high-speed railway bridges worsen as structural damping decreases and peak ground acceleration increases; (3) More spikes are observed in the high-frequency waveband of the power spectral density curve, and seismic-induced track irregularity results in more high frequency periodic components.

Dynamic Amplification Factor Variation Analysis of a High-Speed Railway Bridge under Multiple Loading Cases

Long-span and wide railway bridges are loaded with various loading cases, and the structural dynamic amplification factor (DAF) corresponding to different loading cases has great variability. This study presents an approach to obtaining DAF under different loading cases. Then the approach is applied to the analyses of DAFs from long-term monitoring data. The usual values of vibration amplitude and DAF under eight single-train loading cases during long-term operation are analyzed, and the midspan amplitude and displacement DAF of the main girder under the typical two-vehicle intersection, three-train intersection, and four-train intersection loading cases are also investigated. The correlation between the DAF of the eight loading cases, the structural temperature, and the train speed under the single-train loading case is analyzed. The obtained results show that in the long-term operation, the vibration amplitude level and DAF level of the railway bridge are mainly related to the train loading case, and in 16-carriage loading cases, the DAF value is higher than that in eight-carriage loading cases in the same line. The vertical dynamic response of the midspan main girder under each working condition is small. Furthermore, depending on this evolution law, different traffic loading cases must be considered during the assessment of dynamic performance.

3D analysis of railway induced vibrations on skew girder bridges including ballast track–bridge interaction effects

This work is devoted to the analysis of the vibratory response of High-Speed (HS) multi-track railway bridges composed by simply-supported spans. In particular, it aims to investigate the influence of three geometrical aspects usually disregarded in numerical models used to evaluate the Serviceability Limit State of traffic safety in such structures: (i) the deck obliquity, (ii) the presence and correct execution of transverse diaphragms at the supports, and (iii) the number of successive simply-supported spans weakly coupled through the ballast track layer. The influence of these aspects is analysed from the correlation of a detailed numerical model and experimental measurements on an in-service High Speed (HS) multi-track railway bridge. From the reference model, a set of variants accounting for different levels of deck obliquity and diaphragm configurations are envisaged and the maximum transverse acceleration over the platform is determined under railway excitation. The analysis is extended to bridges with an increasing number of successive spans. Special attention is paid to the particular location of the maximum response and to the participation of modes different from the longitudinal bending one. Finally, a numerical–experimental comparison of the bridge response under two train passages is presented for the straight and oblique models, and the response adjustment along with the actual bridge performance are assessed.

Bridge Static Influence Line Identification Based on Structural Dynamic Responses Under High-Speed Trains

Bridge influence lines can reflect the performance status of bridge structures and are an important tool to evaluate high-speed railway bridges. Because a high-speed train can cause large dynamic response on a bridge, it is difficult to identify the static influence line of the bridge. To extract the static bridge influence lines for bridge evaluation, this paper proposes a low-pass filter design method for static influence line identification. By maximizing the difference in bridge static and dynamic energy, the relationship between the frequency domain characteristics of the bridge dynamic response and the filter parameters is established. Based on this relationship, reasonable values of the low-pass filter parameters can be determined. After filtering the dynamic response, the quasi-static response can be effectively obtained, and the bridge static influence line can be identified through the least square regularization method. Finally, a numerical example of the vehicle–bridge interaction model is used to verify the effectiveness of the proposed method. The results show that the low-pass filter designed through the proposed principle can accurately remove the dynamic effects, and its stability and robustness are good. The research results provide a reliable method for the static influence line identification of high-speed railway bridges.

Transverse seismic analysis of high-speed railway bridge in China based on a simplified calculation model

Transverse seismic analysis of high-speed railway bridge in China based on a simplified calculation model