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When subjected to moving train loads, the bridge-end transition zone becomes an important geotechnical site, requiring detailed investigation. Dealing with complex track–substructure–soil interaction is essential because of the varying stiffness at the specific region. A field data–based, validated, comprehensive numerical model can accurately evaluate the long-term performance of the end-approach zone. In this study, a comprehensive numerical approach was used to examine the transition region of an elevated railway bridge between Rohtak and Gohana in Haryana, India. To explore the overall behavior of the bridge transition zone for the investigated scenario, a static approach to replicating the moving load analysis has been successfully implemented while also considering the effects of rail pad stiffness and repetition of the load. The study revealed that using a softer rail pad significantly affects the overall behavior of the track, abutment wall, and subsurface geomaterials. With the increase in loading cycles, the zone closest to the end substructures is affected more, particularly at shallower depths, considered from the sleeper base. At the same time, because of increased stress mobilization, the deeper soil is relatively more affected when observed at a longer transition distance. [ABSTRACT FROM AUTHOR]

A large proportion of Iranian railway bridge assets comprises masonry arch bridges, which have been in service for over 70 years. Seismic assessment of such structures is very important, particularly for highly seismic regions. This study assesses the seismic performance of Veresk masonry arch bridge, the longest masonry arch bridge in the Iranian railway network (span length 99 m), spanning a valley 110 m deep, through reliable sensor-based model updating. Dynamic tests are conducted using a test train, composed of six-axle locomotives and four-axle freight wagons, which travels across the bridge; the vibration response of the instrumented bridge is subsequently measured. A high-fidelity three-dimensional finite-element model of the bridge is developed and updated using the measured vibration characteristics: mid-span displacements and natural frequencies. Finally, a seismic performance assessment of the bridge is performed using non-linear static and dynamic analyses for two seismic hazard levels with return periods of 150 and 1000 years. It is found that, for the hazard level with a return period of 150 years, both non-linear static and dynamic analyses give very similar results. However, for the seismic hazard level with a return period of 1000 years, the results of the static analysis are more conservative. [ABSTRACT FROM AUTHOR]

When a train traverses a curved bridge, it inherently tends to shift laterally outward. To counteract this propensity, the strategy of track superelevation is employed. After earthquake, curved bridges may exhibit diverse degrees of residual deformation. The precise failure mechanisms that compromise train safety and passenger comfort during transit over curved bridges, particularly under the combined influence of residual deformation, centrifugal force, and track superelevation, remain not entirely comprehended. A comprehensive system integrating trains with curved track-bridges is developed to examine the impact of girder end misalignments on residual track irregularities. The analysis concentrated on the dynamic time-history responses of trains traversing bridges featuring girder misalignments, exploring a range of amplitudes, train velocities, and curve radii. The findings revealed significant variances in the dynamic train responses, especially in lateral acceleration and the Nadal index, when contrasting centripetal and centrifugal girder side misalignments. Furthermore, it is discerned that lateral misalignment at the girder ends markedly affects train lateral acceleration and the Nadal index, with a relatively minor influence on other dynamic response metrics. Finally, the thresholds for misalignment deformation were summarized, for curve radii of 800, 1000, and 1200 meters, the comfort deformation thresholds at 100 km/h are determined to be 23, 23, and 20 mm respectively, while the safety deformation thresholds are found to be 26, 30, and 38 mm respectively. At a speed of 120 km/h, the comfort deformation thresholds for the same curve radii are 18, 18, and 15 mm, with the safety deformation thresholds at 12, 15, and 21 mm. [ABSTRACT FROM AUTHOR]

Girder rotation at the bridge support or girder end is a key deformation indicator that reflects the high-speed railway (HSR) bridge stiffness. Large rotation deformation at these locations leads to train derailment risks, bridge expansion joint degradation, and track system anomaly, which significantly affects HSR bridge operation safety. Hence, it is very assuring to assess girder rotation periodically to ensure safe operation of HSR bridges. However, the mechanical relationship between girder rotation and HSR bridge operation safety indicator is difficult to reveal owing to the high complexity of the dynamic interaction calculation, lack of design information, and lack of finite-element model in practice. To present a girder rotation assessment method that can provide reasonable guidance for HSR bridge operation safety management, a general analytical solution for the girder rotation threshold corresponding to HSR bridge operation safety limit using a train–track interaction model is first derived in this study. Then, an online virtual-loaded method based on rotation influence line is used to predict the most unfavorable effects of HSR bridges with various forms. The automated assessment is achieved by comparing effects to the threshold. Finally, an in-service long-span HSR bridge is used to verify the proposed method. The application results show that the method can periodically generate the most unfavorable rotation effect reflecting bridge stiffness and the rotation threshold reflecting operation safety, achieving long-term automated assessment during HSR bridge operation. [ABSTRACT FROM AUTHOR]

Significant dynamic deformations during the operation of kilometer‐span high‐speed railway bridges adversely affect track maintenance. This paper proposes a three‐stage smoothness control method based on a comprehensive analysis of track alignment characteristics to address this issue. In the method, historical measured data are grouped into multicategories, and reference alignments for each category are reconstructed. Then, the reference alignment category to which the track to be adjusted belongs is accurately matched. Finally, a novel smoothness optimization algorithm is designed to use the 60 m chord as the optimization unit, and the 10 m and 30 m combined chords within the unit constrain the midchord offset and vector distance difference. The proposed method was applied to formulate the maintenance scheme for the Shanghai–Suzhou–Nantong Yangtze River Bridge. The result indicates that the track smoothness improved by more than 79.7%, and the high‐speed train operational performance improved by over 64.3%, effectively enhancing the maintenance quality. [ABSTRACT FROM AUTHOR]

In recent years, wireless sensor networks (WSNs) have become a crucial technology for infrastructure monitoring. To ensure the reliability of monitoring services, evaluating the network's reliability is particularly important. Sensor nodes are distributed linearly when monitoring linear structures, such as railway bridges, forming what is known as a Linear Wireless Sensor Network (LWSN). Although existing evaluation methods, such as enumeration and Binary Decision Diagram (BDD)-based methods, can be used to assess the reliability of various types of networks, their efficiency is relatively low. Therefore, we classified network states based on the number of failed nodes located at the network's ends and analyzed the arrangement characteristics of nodes under different network states. This paper proposed a new reliability assessment method for LWSNs. This method is based on the combinatorial patterns of nodes and uses the concept of integer partitions to calculate the total number of states at different performance levels, applying probability formulas to assess network reliability. Compared to Multi-Valued Decision Diagram (MDD)-based evaluation algorithms, this method is suitable for large-scale LWSNs and offers lower time complexity. [ABSTRACT FROM AUTHOR]

This article explores the use of distributed fiber optic sensing (DFOS) technology in monitoring civil infrastructure, with a concrete example of an elevated railway bridge in Taiwan. The field test utilized multiple strain-sensing fibers attached to a 1 km span of a bullet train railway bridge, which were combined to calculate the 3-dimensional bridge deformation. The installed sensing system and continuous measurements enabled quick safety confirmation after earthquakes of Richter scale 6.4 and 6.8 magnitudes occurred. Finally, the dynamic monitoring of a bullet train using Distributed Acoustic Sensing (DAS) demonstrated the merits of fiber optic sensing for both static and dynamic measurements. The empirical data gathered through this work aid in the evaluation of DFOS technology for structural-monitoring applications. [ABSTRACT FROM AUTHOR]

As one of the three strong tidal bays in the world, Hangzhou Bay has extremely harsh sea conditions. The establishment of ZIHE2D tide level model for astronomical tide-storm tide level prediction in Hangzhou Bay is of great significance to the design and construction of bridge structures. According to the hydrological monitoring data over the years and the latest erosion and deposition topography of Hangzhou Bay, the tidal level model was modified and compared with the measured tidal level in 2018 to ensure the accuracy of tidal level prediction in Hangzhou Bay. The results show that the modified numerical model can predict the tidal level of different return periods in Hangzhou Bay project area. The 100-year high tidal level is 6.17 m, the low tidal level is -3.62 m, and the tidal range is 9.79 m. It provides an effective calculation method for tidal level prediction in Hangzhou Bay. The average high tidal level in the return period has a great influence on bridge safety and construction cost. It provides a reference for the foundation design of Hangzhou Bay Cross-sea Railway Bridge. [ABSTRACT FROM AUTHOR]

Resonance in high-speed railway bridges can deteriorate the structural integrity and running safety of a train; thus, the resonant speed needs to be identified. Previous studies have proposed resonant conditions analytically, but their applications to in-service bridges are limited. Free vibration after the passage of a train was utilized to assess resonance, but it could not capture the natural frequency of the coupled system because the train-bridge interaction was neglected. This study proposed a practical framework for quantifying the resonance in a high-speed railway bridge using a phase shift. The static displacement of the railway bridge was numerically reconstructed using the train loading history. Phase angles were extracted by comparing the static and dynamic displacements, which were directly utilized to develop a novel resonance indicator in this study. Numerical simulations and field demonstrations validated the applicability of the proposed method for understanding the resonance behavior of full-scale railway bridges. [ABSTRACT FROM AUTHOR]

The subject of research is a steel arch-tied bridge at a high-speed railway line in Poland. After the construction was completed, a resonance phenomenon was observed at the bridge, consisting of the occurrence of intense (visible to the unaided eye) undamped vibrations of some vertical hangers in the horizontal direction, transverse to the track axis. These vibrations occurred without the presence of a railway load on the bridge. Before the bridge was put into operation, an acceptance static and dynamic load test was performed, and then the bridge deck vibrations were monitored for a year. The research during dynamic loads testing included both quasi-static (10 km/h) and high-speed (200 km/h) testing train passages. The vertical displacement measurements were carried out in three cross sections of the span, and the acceleration of vibrations on girders and selected hangers was also measured. Next, an innovative system for determining displacements indirectly using inertial sensors (inclinometers and accelerometers) was used for bridge deck vibration monitoring. The primary aim of the research was to investigate the possibility of assessing the safe operation of the bridge using a monitoring system consisting of a limited number of inertial sensors. The second aim was to verify the feasibility of calibrating the numerical model based on the results of dynamic load testing. Numerical analyses of the behavior of the bridge during the passage of trains with speeds up to 200 km/h were carried out. The developed and calibrated numerical model provides additional information about the overall structural vibrations, facilitating the interpretation of outcomes of the monitoring system. No significant impact of hanger vibrations on the monitored displacements and accelerations of the bridge deck vibrations during the passage of trains was found. [ABSTRACT FROM AUTHOR]

Utilizing the results of static load tests using the self-balancing method on two large-diameter bored piles from the Huaiyang Left Line Special Bridge Project of the Lianyungang–Zhenjiang Railway, this study aims to investigate the effect of combined tip-and-side post-grouting on the bearing characteristics of post-grouted piles in railway bridges. The difference in bearing performance between individual piles before and after grouting was evaluated using a comparative analysis. The results show that the bearing capacity of the pile foundations is greatly increased by combined tip-and-side post-grouting. In particular, following grouting, a single pile's maximum bearing capacity rises from 32.99% to 38.42%. The combined post-grouting produces a compressed grout that enhances the mechanical characteristics of the pile–soil contact, resulting in a significant increase in side resistance all the way along the pile. The combined post-grouting also optimizes the performance of the tip resistance, resulting in a more rapid response as the pile tip displacement increases. Additionally, the combined post-grouting modifies the pile shaft's load transfer mechanism by increasing the tip resistance's contribution to the pile foundation's ultimate bearing capacity and moving the bearing's center of gravity closer to the pile end. [ABSTRACT FROM AUTHOR]

Optimization of the method for calculating influence lines from measurement data As part of the measurement‐based reassessment of steel railway bridges, influence lines resulting from the passage of a load vehicle are used to determine structural loading. The commonly used method for deriving influence lines from measurement data is the Braune method, which computes the influence line step by step from the data. This article discusses the matrix method, an alternative method for determining influence lines, and compares it with the Braune method. For this purpose, different factors influencing the result quality of the influence lines were investigated using artificial strain lines generated on the static model of the Norderelbe railway overpass and validated using measurement data obtained during the reassessment of the bridge. The findings demonstrate that the matrix method offers a robust approach to influence line determination and the amount of work involved in determining the influence lines can be reduced in comparison to the Braune method. Furthermore, the matrix method can be flexibly integrated into the existing process of influence line determination. [ABSTRACT FROM AUTHOR]

This study addressed the issue of distortion in evaluating the seismic damage state of railway bridge piers using the original Park-Ang damage index. By constructing a parameterized co-simulation program with two finite element models, OpenSees and Abaqus, five sets of flexural failure and five sets of flexural-shear failure rectangular pier quasi-static test results were selected to validate the rationality of the calculation program. Four hundred and eighty parameterized calculations were conducted using this program. The combination coefficient β and critical damage index DI within the Park-Ang damage index were modified using nonlinear regression algorithm and convolutional neural network algorithm. The adaptability of the damage index calculation was ultimately verified through an engineering case study of a simply supported beam bridge. The research findings are as follows: 1) The main factor influencing β is the longitudinal reinforcement ratio, while the axial compression ratio, shear span ratio, volumetric stirrup ratio, aspect ratio, concrete strength, and steel strength are secondary parameters influencing β. 2) Compared to the nonlinear regression algorithm, the convolutional neural network algorithm can better establish a calculation model between pier structural parameters and β, clarifying their relationship. 3) It is recommended to use critical values of 0.11, 0.29, 0.49, and 1.00 for assessing pier damage as no, slight, moderate, severe, and collapse damage when using the damage index calculation model. 4) The Park-Ang index corrected by convolutional neural networks demonstrates improved accuracy and computational stability, making it suitable for practical assessment of seismic damage in bridge structures. Highlights: The original Park-Ang damage index has been modified to suit railway rectangular bridge piers. The possibility of flexural-shear failure in railway bridge piers has also been taken into consideration. In addition to the nonlinear regression algorithm, a convolutional neural network algorithm has been applied in the construction of the damage index calculation model. A simple supported beam bridge engineering case has been used to validate the applicability of the damage index calculations. [ABSTRACT FROM AUTHOR]

Welded Turnout on Large-span Bridge (WTLB) is a complex multi-layer heterogeneous system and can significantly influence the service performance of High-Speed Railway (HSR). Understanding the coupling dynamic response of the vehicle and WTLB is essential. Previous research did not consider the dynamic behavior of foundations, leading to an underestimation of the vehicle-turnout-foundation coupling dynamic response, particularly when turnouts were laid on large-span bridges. This study proposes a novel modeling method that includes the foundations, to overcome the previous shortcomings by applying a rigid-flexible coupling system. In this approach, the vehicle was modeled as a rigid body sub-model in a Multi-Body Software (MBS), while WTLB was modeled as a flexible bodies sub-model using Finite Element (FE) software. The modal information from the FE model was imported into the MBS software. The two sub-models were coupled by the wheel-rail contact in the MBS environment and then the Vehicle-turnout-bridge Rigid-flexible Coupling Dynamic (VRCD) calculation model was established and it was discovered that the calculation results showed good agreement with the field test data. Through the VRCD model, the safety of the structure, the stability of the vehicle and the comfort of passengers were investigated, as well as several important infrastructure factors. The results demonstrate that this novel method provides accurate calculations and highlights the complex and significant interactions in the vehicle-turnout-bridge system. [ABSTRACT FROM AUTHOR]

The issue of low-frequency structural noise radiated from high-speed railway (HSR) box-girder bridges (BGBs) is a significant challenge worldwide. Although it is known that vibrations in BGBs caused by moving trains can be reduced by installing multiple tuned mass dampers (MTMDs) on the top plate, there is limited research on the noise reduction achieved by this method. This study aims to investigate the noise reduction mechanism of BGBs installed with MTMDs on the top plate. A sound radiation prediction model for the BGB installed with MTMDs is developed, based on the vehicle–track–bridge coupled dynamics and acoustics boundary element method. After being verified by field tested results, the prediction model is employed to study the reduction of vibration and noise of BGBs caused by the MTMDs. It is found that installing MTMDs on top plate can significantly affect the vibration distribution and sound radiation law of BGBs. However, its impact on the sound radiation caused by vibrations dominated by the global modes of BGBs is minimal. The noise reduction achieved by MTMDs is mainly through changing the acoustic radiation contributions of each plate of the bridge. In the lower frequency range, the noise reduction of BGB caused by MTMDs can be more effective if the installation of MTMDs can modify the vibration frequency and distribution of the BGB to avoid the influence of small vibrations and disperse the sound radiation from each plate. [ABSTRACT FROM AUTHOR]

This study aimed to quantify carbon emission indicators for railway bridge construction and explore green, low-carbon optimization strategies. It focused on analyzing the carbon emissions generated by different precast schemes during the construction phase of railway bridges. A carbon emission calculation framework for the construction phase was established, and the analysis was applied to an intercity railway bridge project in the Guangdong - Hong Kong - Macao Greater Bay Area (GBA). Two design schemes were considered: the segment precast continuous rigid frame bridge and the full-span precast simply supported beam bridge. The results showed that the segment precast continuous rigid frame bridge scheme produced lower carbon emissions per unit distance than the full-span precast simply supported beam bridge scheme, reducing emissions by about 3.96%. The material production stage accounted for the highest proportion of carbon emissions, about 95%, while transportation contributed the least, about 1 %, and the mechanical construction stage accounted for about 4%. Compared to the segment-precast continuous rigid frame scheme, the full-span precast simply supported scheme had 4.37% higher material-related carbon emissions, 15.57% higher transportation carbon emissions, and 4.04% lower machinery carbon emissions. For both schemes, the carbon emissions from steel and concrete accounted for over 94% of the total material-related emissions. The full-span simply supported beam scheme had higher carbon emissions from concrete production and transportation, which were 20.27% and 19.35% higher, respectively, than those of the segment-precast continuous rigid frame scheme. The primary energy types consumed by construction machinery were diesel and electricity, accounting for over 99% of total energy consumption. [ABSTRACT FROM AUTHOR]

The complex deformation of large-span high-speed railway bridges, influenced by factors such as thermal load, poses a challenge in the acceptance inspection of track irregularity quality on the bridges. To quickly establish targeted maintenance and repair standards for kilometer-span high-speed railway bridges, time-frequency distribution characteristics of track irregularities were analyzed using dynamic and static track irregularity detection data from existing kilometer-span high-speed railway bridges in China as samples. The accumulated data over the course of a year was examined using the mid-chord method, vector distance difference method, and track irregularity power spectral method. The results showed that, in the time domain, the dynamic and static track irregularity over-limit points on suspension and cable-stayed bridges were mainly located at the bridge piers and mid-spans. The amplitudes of track irregularities were elevated at the rail expansion joints installed at the ends of the suspension bridges, requiring timely control of the irregularity amplitude at critical positions on the bridges. In terms of frequency-domain characteristics, the track spectra of kilometer-span high-speed railway bridges exhibited a change pattern roughly similar to the ballasted track irregularities on high-speed railways in China. A combined analysis of dynamic and static power spectra revealed that the track spectrum of kilometer-span high-speed railway bridges, in the medium-and long-wavelength frequency bands for high and low irregularities, was mainly located between the ballast spectrum of China and the low-interference spectrum of Germany. Among them, the overall performance of the kilometer-span suspension bridges was significantly inferior to that of the kilometer-span cable-stayed bridges in the long-wavelength band around 100 m and in the medium-and short-wavelength band below 10 m. Both bridge types commonly showed periodic wavelength components of 1 ~ 3 m and 8 ~ 12 m. Daily railway maintenance operations should continue to address rail smoothness issues caused by factors such as irregularities in new rails and weld joints. [ABSTRACT FROM AUTHOR]

The shortcomings of segmentally assembled round‐end hollow‐section piers (SRHPs), such as weak segment joints and poor energy‐dissipation capacity, have limited their application in high‐intensity earthquake regions. Therefore, this article particularly focuses on the seismic performance of SRHPs. Three high‐speed railway bridges are designed, which are equipped with three different types of round‐end hollow‐section piers (RHPs): cast‐in situ RHP (CRHP), segmentally assembled RHP with energy‐dissipation bar (E‐SRHP), and segmentally assembled RHP with low‐yield point steel connection buckles (L‐SRHP). Subsequently, three nonlinear finite element models of the corresponding bridges were established and validated by quasi‐static test results. Furthermore, compared to CRHP, the seismic performance of E‐SRHP and L‐SRHP was evaluated from the perspectives of seismic fragility and life‐cycle seismic loss. Research results revealed that the seismic fragility performance of the bridge with L‐SRHP is the best among all three bridges, followed by the bridge with E‐SRHP. Notably, the life‐cycle cost considering seismic loss for E‐SRHP is 83% of that for CRHP, whereas L‐SRHP is only 65% of that for CRHP. In general, the high‐speed railway bridge supported by L‐SRHP possesses the best seismic performance and economic benefits among the three bridges, which shows promising application prospects in high‐intensity earthquake‐prone regions. [ABSTRACT FROM AUTHOR]

Near-fault ground motions may cause serious damage and consequence of high-speed railway bridges (HSRBs), since their particularly detrimental effects, including the hanging-wall effects and velocity pulse effects. However, the induced seismic demand depends on the complex relationship between natural vibration characteristics of structures and frequent contents of ground motions, leading to the difficulty in attributing to less seismic attenuation or/and the above special effects. This work adopts a framework to select a ground motion suite with a specified near-fault effect by multiple controllable constraints on the target response spectrum. Near-fault effect on seismic demand is visualized and quantified by empirical cumulative distribution functions (ECDFs) and the Kolmogorov-Smirnov test. An ECDF-based method is proposed to develop a bilinear probabilistic seismic demand model (PSDM) to capture the nonlinear relationship between engineering demand parameter (EDP) and intensity measure caused by near-fault effects. In the case study, the hanging-wall effects and the directivity-induced velocity pulse effects are investigated on a simply-supported HSRB. The influence of the two effects on key structural components is examined, in which the demand changes are attributed to one of them. The result shows that the hanging-wall effect amplifies both mean and variance of the seismic demands. Pulse-like records cause sudden increases in demand ECDFs, which are used to determine the transition point in the bilinear PSDMs. The refined PSDMs well capture the nonlinear trend of EDP varying with PGV when considering pulse-like records. [ABSTRACT FROM AUTHOR]

Translation abstract Applicability of train‐specific additional damping to new car generationsThe structural vibrations caused by high‐speed trains and the compliance with associated limits often constitute a decisive criterion in the dynamic assessment of railway bridges. In this context, the results of computational simulations frequently exhibit significant discrepancies when compared to measurements. This is partly attributed to oversimplified modelling and the resulting need for conservative assumptions. The mechanism of vehicle‐bridge interaction, depicted by a multibody model of the passing high‐speed train, which usually has a favorable effect, can be integrated into calculations using a simpler mechanical train model of moving loads by considering an additional factor of damping of the bridge‐structure, without increasing the model complexity. The introduction of a new generation of the Railjet raises questions regarding the applicability of the additional damping values valid in Austria for the Railjet, which are derived using the data of the currently operating Railjet generation. This article outlines the corresponding investigation, which seeks to address the aforementioned questions through the application of efficiency‐optimised dynamic analyses to crossing simulations. [ABSTRACT FROM AUTHOR]

Efficient probabilistic prediction of seismic responses is crucial for assessing the seismic-resistant capability of long-span continuous girder high-speed railway bridges. Thus, a Bayesian physics-informed neural network (BPINN) is adopted to rapidly and effectively predict the probabilistic seismic responses of such bridges. The BPINN model combines deep learning and physics to improve the accuracy and consistency of predictions, while also quantifying the uncertainties using Bayesian inference methods. Various seismic excitations, including pulse, far-field and near-field types, are employed to probabilistically predict the seismic responses of the top of bridge pier. Evaluation metrics, including mean squared error and prediction interval coverage probability, are used to assess the deterministic and probabilistic estimates of BPINN. Results demonstrate that BPINN performs better in deterministic results for far-/near-field ground motions compared to pulse-like earthquakes, with most cases exhibiting a close approximation to the 95% confidence interval. The flexibility and adaptability of BPINN in handling different types of ground motions can provide valuable insights for assessing the seismic performance of such structures. [ABSTRACT FROM AUTHOR]

In order to study the dynamic response of high-speed railway bridge and its deformation law under the coupling effect of vibration load and shield tunneling, a coupling model of shield tunneling and train load is established based on the actual case of tunneling under an adjacent bridge. The deformation characteristics and dynamic response of the bridge are investigated by analyzing the deformation under different tunneling conditions and train running speeds. The results show that the maximum disturbance of the original stress field around the bridge is caused when the shield penetrates to the near side of the bridge structure, at which time, the damping effect of the ground and bridge system on the vibration load is weakened, thus intensifying the dynamic response of the bridge system, and the additional deformation caused by the vibration load is the largest; the presence of train loads during the shield excavation slightly attenuates the differential settlement of the bridge, but increases the cumulative settlement of the bridge, in addition, the additional deformation of the bridge will increase with the increase of the train running speed; the additional deformation caused by the train load within 2 m of the shield crossing on both sides of the bridge is large, so the construction should be avoided as much as possible when the train is running in this construction section. [ABSTRACT FROM AUTHOR]

A novel damage detection model, which utilizes the spatiotemporal characteristics of the acceleration data, is proposed to assess the structural integrity of railway bridges. For this, the measured acceleration data are decomposed into several intrinsic mode functions (IMFs) using the sparse random mode decomposition model. The generated IMFs are subsequently integrated into the enhanced time series conditional generative adversarial network model to identify possible damage in bridges across various frequency bands. The influence of environmental and operational variables (EOVs), particularly temperature fluctuations, was also investigated. The proposed model was verified using both numerical and experimental data from a plate girder bridge. Further validation was conducted using the Z24 bridge dataset, and damage cases under the influence of EOVs were successfully predicted. Throughout the validation process, various anomaly metrics were introduced to establish a threshold value, and a covariance‐based time domain metric was proven to be the most effective in our cases. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Harbin Institute of Technology. Social Sciences Edition / Haerbin Gongye Daxue Xuebao. Shehui Kexue Ban is the property of Harbin Institute 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.)

This paper presents a novel statistical analysis-based approach to non-parametric damage detection in truss bridges. The method utilizes the normalized acceleration response time histories (NARTHs) of a bridge under random excitation. The coefficients of variation matrices are calculated using NARTHs for the truss bridge in both its baseline and damaged states. The results are shown as the difference in covariance matrices (DCMs) between the two conditions (pristine and damaged). The row or column-wise summation of the DCM matrix yields a summation of the difference in covariance matrix (SDCM) bar plot having one distinct peak for the damaged member. The location and relative severity of the damage can be determined by examining the DCM matrix and the SDCM bar plot. The variation in magnitude of the coefficients demonstrates the relative severity of damage. Experimental investigation of the proposed method for detecting damage on the truss bridge shows promising results. The approach is then numerically validated using a finite element model of a truss bridge. The proposed method effectively identified, located, and evaluated damage, even when the acceleration time histories are contaminated with noise. The case of multiple-member damage detection in the truss structure is further investigated in the study. The early detection of damage and monitoring of its progression through this method can assist in creating efficient maintenance strategies for truss bridge infrastructure. [ABSTRACT FROM AUTHOR]

The health monitoring of infrastructure is vital for ensuring the safety and structural integrity of bridges. Recently, ground-based real aperture radar (GB-RAR) systems have been successfully utilized in the dynamic and static monitoring of bridges. In this study, a comprehensive and innovative approach is presented to monitor the vertical deformation of a long-span metallic railway bridge and a reinforced concrete Shinkansen bridge in Japan using a polarimetric GB-RAR system. Distinct from conventional signal processing procedures, the proposed method omits the coherent scatterer selection step. Instead, polarization analysis is employed to evaluate the properties of scatterers and identify those corresponding to bridge sections requiring monitoring, while considering the structural characteristics of the bridge. Simultaneously, the signal-to-noise ratio for monitoring is enhanced by combining co-polarization responses from scatterers. Furthermore, the radar look angle is determined by accounting for the spatial configuration of the survey and the polarization orientation angle. Lastly, vertical deformation is assessed by projecting line of sight deformation in the vertical direction. The findings reveal the dynamic responses of the two bridges under diverse loading conditions, which include the transit of a low-speed train and a high-speed Shinkansen bullet train. The results demonstrate that the polarimetric GB-RAR interferometry technique, coupled with the developed algorithms, can be effectively applied to monitor any type of bridge with unparalleled spatial and temporal resolutions. [ABSTRACT FROM AUTHOR]

Fabricated ballastless track has witnessed increasingly wide application in large-span bridges of municipal railways. The current ballastless track standard is applicable to bridges with a main span of 200 m to 400 m. For the main span is longer than 400 m, it is necessary to ensure the travelling safety and comfort on the fabricated tracks. In this study, static and dynamic analysis models of train-track-bridge are established to explore the influence of complex ambient temperature changes and concrete shrinkage and creep on bridge deformation, followed by the analysis of the deformation coordination between long-span bridge and fabricated ballastless tracks, thereby revealing the dynamic response of the train-track-bridge system under the complex influence of temperature. The results show that when a train runs at a speed of 160 km/h, the existing ballastless track design standard is still applicable to a bridge span of 688 m. Compared with CRTS type III track, the adoption of the novel prefabricated ballastless track on long-span urban bridges provides higher safety and greater comfort, with comprehensive power performance improved by more than 10%. This design comprehensively takes into account the deformation coordination and dynamic performance of the rail bridge, providing a basis for the design and application of fabricated ballastless tracks on long-span bridges of urban railways. [ABSTRACT FROM AUTHOR]

The steel–concrete composite beam, as a structural form that combines the advantages of steel and concrete, has been applied in railway engineering. However, with the increase in railway operation time, the degradation pattern of the service performance of steel–concrete composite bridges remains unclear. This paper proposes a method for calculating the long-term service performance of railway steel–concrete composite beams, considering the cumulative fatigue damage of steel beams and studs, based on the vehicle–bridge coupling theory and Miner's linear cumulative damage criterion. The proposed method is validated using measured data from an in-service steel–concrete composite railway bridge with spans of 40 + 50 + 40 m. The calculated mid-span vertical displacement and the first two natural frequencies of the composite beam deviated from the measured results by only 2.1%, 7.7%, and 9.5%, respectively. The research results can provide a basis for extending the service life of composite beams and preventing the occurrence of safety accidents. [ABSTRACT FROM AUTHOR]

This paper proposes a novel damage index for railway bridges based on synchronous strain and displacement data collected at the passage of trains. The approach identifies a transformation operator that converts strains into displacements in a data‐driven fashion without prior structural knowledge and with no parameter selection. The displacement prediction error is proposed as a robust damage index, insensitive to the vehicle loads and temperature effects. Numerical simulations and data generated through the calibrated finite element model of a steel truss bridge showcase the effectiveness of the proposed approach. [ABSTRACT FROM AUTHOR]

Monitoring and predicting the dynamic responses of railway bridges under moving trains, including displacement and acceleration, are vital for evaluating the safety and serviceability of the train–bridge system. Traditionally, finite element analysis methods with high computational burden are used to predict the train-induced responses according to the given train loads and, hence, cannot easily be integrated as an available structural-health-monitoring strategy. Therefore, this study develops a novel framework, combining the train–bridge coupling mechanism and deep learning algorithms to efficiently predict the train-induced bridge responses while considering train load duration. Initially, the feasibility of using neural networks to calculate the train–bridge coupling vibration is demonstrated by leveraging the nonlinear relationship between train load and bridge responses. Subsequently, the instantaneous multiple moving axial loads of the moving train are regarded as the equivalent node loads that excite adjacent predefined nodes on the bridge. Afterwards, a deep long short-term memory (LSTM) network is established as a surrogate model to predict the train-induced bridge responses. Finally, the prediction accuracy is validated using a numerical case study of a simply supported railway bridge. The factors that may affect the prediction accuracy, such as network structure, training samples, the number of structural units, and noise level, are discussed. Results show that the developed framework can efficiently predict the train-induced bridge responses. The prediction accuracy of the bridge displacement is higher than that of the acceleration. In addition, the robustness of the displacement prediction is proven to be better than that of the acceleration with the variation of carriage number, riding speed, and measurement noise. [ABSTRACT FROM AUTHOR]

As part of the development of advanced, data-driven methods for predictive maintenance of railway infrastructure, this paper analyzes and evaluates more realistic predictions of eigenfrequencies of railway bridges, also referred to as natural frequencies, based on a population of already assessed, measured existing bridges using regression techniques. For this purpose, Machine Learning (ML) techniques such as Polynomial Regression (PR), ANN and XGBoost are consistently evaluated and the application of the XGBoost algorithm is identified as the most suitable prediction model for these eigenfrequencies, usable for dynamic train-bridge interactions. The results of the post-processing are incorporated into the safety architecture for bridge verification (risk management). The presented data-based techniques are a steppingstone towards digitalization of structural health monitoring and offer safety and longevity of the railway bridges. Furthermore, the use of these methods can save costs that would be incurred by physical in-situ measurements. The types of bridges analyzed with ML are Filler Beam Bridges (FBE), which outnumber other construction types of bridges in Germany (DB InfraGO AG). This methodology is applicable to any bridge type as long as sufficient data are gathered for training, validation and testing. [ABSTRACT FROM AUTHOR]

The Wind–Vehicle–Bridge (WVB) coupling method is extensively applied in engineering practices for the dynamic analysis of railway bridges. However, research on the dynamic behaviors of the vehicle on curved bridges in wind conditions remains limited due to the complexities of interactions involved. In this study, the railway alignment and an actual curved bridge were chosen and modeled. The framework of the WVB system was detailed, and four excitation cases were investigated, considering mean wind, fluctuating wind and track irregularities. Three distinct scenarios, including vehicle on a curved bridge subjected to Inward Blowing Wind (IBW), Outward Blowing Wind (OBW) and vehicle on a straight bridge subjected to wind, were explored. The main conclusions are as follows: (1) wind direction significantly affects wheel unloading rate, lateral force, and derailment coefficient; (2) under mean wind condition, critical wind speed increases with the vehicle speed increasing under IBW, while it decreases with the vehicle speed increasing under OBW; (3) Combined wind and track irregularities reveal that wind direction significantly influences dynamic responses, and lower speeds are not necessarily equal to safer conditions for vehicles on curved bridges. [ABSTRACT FROM AUTHOR]

Restructuring of the railways and steel railway bridges in Chemnitz and Hannover around 1900 The development of the railway network in the mid‐19th century had massive implications for settlement and landscape planning in Germany, deeply affecting the cultural and historical development of each region. As a consequence of high industrialization, around 1900, there was a significant increase in the population's desire for mobility and the necessity of transporting goods. This led to the continuous expansion of the railway network. Particularly in urban areas, this expansion was accompanied by the construction of extensive infrastructure, which increasingly reached its capacity limits on both roads and railways. The necessary track diversions required the construction of a large number of new bridge structures. This gave rise to a variety of steel solid web girder bridges with short spans, which, with their economical design language and richly adorned abutment pylons, profoundly transformed the cities. These bridge ensembles, as well as the respective construction and planning processes, will be examined in more detail for the cities of Hannover and Chemnitz. The discussion will focus on the solutions found for the same construction task against the backdrop of each region's unique political context and how they have shaped the urban landscape. [ABSTRACT FROM AUTHOR]

This paper presents a maintenance prioritisation framework for Taiwan's 1268 pedestrian bridges. It aims to standardise their inspection and maintenance, as Taiwan's current bridge management specifications and manuals only apply to its highway and railway bridge infrastructure. It is designed to assess the structural safety and serviceability of six pedestrian bridge types by visual inspection. To assign weight factors to the structural safety and serviceability components of the identified bridge types, two rounds of Delphi method interviews with bridge experts were conducted. The framework is centred on a weighted average condition assessment method that integrates expert-determined weight factors with visual inspection results to calculate a condition index (PBCI). Pedestrian bridges are ranked and classified based on their PBCIs to set appropriate inspection frequency and scope, and to inform maintenance resource allocation. The application of the framework to five pedestrian bridges in Taoyuan City demonstrated its practicality and value for bridge authorities tasked with managing large inventories of pedestrian bridges. [ABSTRACT FROM AUTHOR]

The 2022 M6.9 Menyuan earthquake caused severe damage to a high-speed railway bridge, which was designed for high-speed trains running at speeds of above 250 km/h and is located right next to the fault. Bridges of this type have been widely used for rapidly constructing the high-speed railway network, but few bridges have been tested by near-fault devastating earthquakes. The potential severe impact of the earthquake on the high-speed railway is not only the safety of the infrastructure, trains and passengers, but also economic loss due to interrupted railway use. Therefore, a field survey was carried out immediately after the earthquake to collect time-sensitive data. The damage to the bridge was carefully investigated, and quantitative analyses were conducted to better understand the mechanism of the bridge failure. It was found that seismic action perpendicular to the bridge's longitudinal direction caused severe damage to the girders and rails, while none of the piers showed obvious deformation or cracking. The maximum values of transverse displacement, out-of-plane rotation and twisting angle of girders reached 212.6 cm, 3.1 degrees and 19.9 degrees, respectively, causing severe damage to the bearing supports and anti-seismic retaining blocks. These observations provide a basis for improving the seismic design of high-speed railway bridges located in near-fault areas. [ABSTRACT FROM AUTHOR]

Long integral bridges experience an enhanced cyclic soil structure interaction with their granular backfills, especially due to seasonal thermal loading. For numerical modelling of this interaction behaviour under cyclic loading, it is important to employ a suitable constitutive model and calibrate it thoroughly. However, up to the present, experimental data and calibrated soil models for this purpose with focus on typical well-graded coarse-grained bridge backfill materials are rarely available in the literature. Therefore, one aim of this paper is to present results of a comprehensive cyclic laboratory testing programme on highly compacted gravel backfill material. Based on this, a hypoplastic constitutive model with intergranular strain extension for small strain and cyclic behaviour is calibrated and evaluated against the experimental test data. The soil model's abilities and limitations are discussed at element test level. In addition, cyclic FE analyses of an integral bridge are conducted with several hypoplastic parameter sets from the literature and compared to the calibrated gravel backfill material. The investigation highlights that poorly-graded sands show significantly smaller cyclic earth pressures compared to well-graded gravels intended for the backfilling of a bridge. The soil structure interaction behaviour is clearly governed by the general soil model stiffness, including the small strain stiffness. [ABSTRACT FROM AUTHOR]

During the operation of rack railway on super-slope bridges (especially under temperature load), structural deformation of bridge-end is much larger than that of rack due to the difference of structural continuity between bridge and rack, which greatly increases local stress in rack, damages rack and fastener, and seriously threatens the operation reliability. To investigate the reliability of rack caused by temperature load and nonlinear dynamic interaction between super-slope bridge and rack, a detailed vehicle-rack(rail)-bridge coupled dynamic model is established with consideration of nonlinear dynamic meshing behaviour of gear-rack system and nonlinear dynamic contact behaviour of wheel-rail system. Then a field test is performed to obtain the basis dynamic behaviour of rack railway and validate the established numerical model. On this basis, the effects of temperature load, gear-rack meshing behaviour and wheel-rail contact behaviour on deformation and internal stress of rack-bridge system are investigated. Finally, the method to guarantee the structural reliability of rack railway on super-slope bridge is proposed. Results show that rack deformation nearby bridge gap is highly inconsistent with bridge deformation subject to different loads, and the internal stresses in rack and bolt exceed limit values written in relevant code, which seriously threatens the reliability of the rack structure. The maximum rack stress is 898 MPa, which exceeds the tensile strength of rack. The maximum shear stresses of bolts between fastener and rack and between fastener and sleeper are 1510 MPa and 656 MPa respectively, which exceed the shear strength of bolts. According to the calculation results in this paper, elastic fastener is suggested to be used to connect rack and sleeper, which can effectively reduce stress in rack and bolt, and improve the reliability of the rack structure. [ABSTRACT FROM AUTHOR]

In order to study the influence law of rockfall on the train running safety of railway bridges, a simply supported box girder bridge on a railway in western mountainous area was taken as the research object. A rockfall impact simulation model and a vehicle-track-bridge coupling dynamic analysis model, which fully considered material nonlinearity and contact nonlinearity, were established. The characteristics of rockfall impact force on bridge piers were clarified, and the train running safety on the bridge under rockfall impact was analyzed. The influence of rockfall impact speed, angle, height, and rockfall diameter on running safety was also revealed. The results showed that: (1) The peak impact force value of rockfall increased with the speed and diameter of the rockfall, while the impact height and angle had little effect on the peak impact force. (2) The increase in rockfall diameter enlarged the damage range of the pier structure, characterized by the appearance of multiple impact force peaks and an extended impact force time history. (3) The faster the rockfall impact speed and the greater the impact energy, the more significant the threat to train running safety on the bridge. The closer the rockfall impact height was to the top of the pier and the larger the diameter of the falling rock, the greater the lateral dynamic response of the train, posing a higher threat to train safety on the bridge. (4) The variation patterns of the time-history curves of each safety evaluation index of the train under different working conditions were similar across different impact angles of rockfall, with minimal changes in their impact on train safety. (5)The wheel load reduction rate was highly sensitive to rockfall diameter and impact height. The wheel load reduction rate exceeded the standard limit when the rockfall diameter reached 2. 5 meters. The research results will provide a reference for the whole life cycle design and safe operation and maintenance of railway bridges in western mountainous area. [ABSTRACT FROM AUTHOR]

In order to evaluate the post-earthquake condition of railway bridges, this study develops a method for evaluating the traffic function of railway bridges based on vulnerability. Taking common railway bridges in China as references, 20 four-span simply-supported beam bridges with varying structural parameters were modeled in OpenSees for full-bridge finite element analysis. Seismic timehistory analysis was employed to evaluate both the vulnerability and traffic function of the bridges, clarifying the key factors influencing seismic damage and traffic function. The findings indicated that the longitudinal reinforcement ratio and shear span-to-depth ratio were the core factors affecting seismic damage, with the axial compression ratio also playing a significant role, while the volumetric stirrup ratio served as a secondary factor. To control seismic damage of the bridges, increasing the longitudinal reinforcement ratio and reducing the shear span-to-depth ratio were recommended. A higher reinforcement ratio significantly enhanced traffic capacity, while an increased shear span-to-depth ratio reduced it. Additionally, slight improvements in traffic capacity were observed with increases in the reinforcement ratio and axial compression ratio. The longitudinal reinforcement ratio and shear span-to-depth ratio were the main factors affecting the traffic function of the bridges, while the volumetric stirrup ratio and axial compression ratio were secondary. To ensure optimal traffic capacity, the longitudinal reinforcement ratio should be appropriately increased or the pier shear span-to-depth ratio be reduced, with modest increases in the volumetric stirrup ratio and axial compression ratio. The traffic capacity evaluation method proposed in this study provides an effective tool for assessing bridge functionality and is suitable for post-earthquake assessments. [ABSTRACT FROM AUTHOR]

A railway bridge is located in a high-intensity seismic zone near a fault, with asymmetric deep-cut valleys. To determine the optimal bridge design, three types of bridge structures were proposed, taking into account climatic, topographical, geological conditions, and other relevant factors. The proposed schemes included a (95+160+95+59) m prestressed concrete continuous rigid-frame bridge, a (60+200+106+50) m partial cable-stayed bridge and a (253+145) m continuous steel truss flexible arch. Each scheme's structural dimensions and construction methods were introduced in detail. Finite element analysis models for the bridges were established using BSAS and Midas Civil software, and analyses were conducted on the main beams, pylons, piers, pile foundations and dynamic characteristics. Comparisons of the three schemes were performed based on structural stiffness, construction difficulty, construction period, seismic performance, maintenance requirements and engineering cost. The results showed that: (1) Under static load, the continuous rigid-frame bridge exhibited a vertical displacement of 38 mm, with a span-to-deflection ratio of 1/4 210; the partial cable-stayed bridge had a vertical displacement of 135. 4 mm, with a span-to-deflection ratio of 1/1 477; and the continuous steel truss flexible arch showed a vertical displacement of 78 mm, with a span-to-deflection ratio of 1/3 231. (2) The first-order period of the continuous rigid-frame bridge was 2. 02 s; the partial cable-stayed bridge was 2. 4 s; and the steel truss flexible arch was 2. 58 s. (3) All three bridge schemes met the design specifications and were proven to be safe and feasible, but the continuous rigid-frame bridge was significantly more cost-effective than the other two options. ( 4) Prestressed concrete continuous rigid-frame bridge, with its large stiffness, mature construction technology, superior seismic performance, low engineering cost and minimal maintenance requirements, was considered the optimal scheme. [ABSTRACT FROM AUTHOR]

The subject of this study is the inventory and assessment of the load-bearing capacity of a railway bridge. The analysis was conducted on a bridge with a concrete slab reinforced by steel beams as the load-bearing element. The structure is located in the village of Bukowina, Warmian-Masurian Voivodeship, Poland. The aim of the study is to assess the load-bearing capacity of the bridge. The structure's geometry was measured, and its concrete strength class determined. This article presents the results of stress limitation calculations for the tested bridge. Three calculation procedures based on two approaches--a concrete-encased beam and a bending section reinforced with rigid inserts -- were applied. The analysis demonstrated that, despite the unesthetic appearance of the bridge, it meets the stress limitation requirements. Though over a hundred years old, the structure remains suitable for use today. [ABSTRACT FROM AUTHOR]

Increasing the operating speed of the trains on modern networks necessitates performing dynamic analyses to assess the performance of bridges under passage of trains. The detailed investigation of their responses requires constructing complex computational models capable to take the train–track–bridge interaction effects into account. Such models have successfully been developed; however, employing those elaborated models for practical engineering applications, or to perform studies that require a large number of analyses may become infeasible. Among such situations are conducting probabilistic investigations, screening of entire networks, or sensitivity analyses. These concerns have been addressed by employing simplified models mostly relying on moving load modeling strategy which disregards the train–track–bridge interaction effects. Those neglected contributions can be compensated by implementing additional correction factors. The distribution of loads within track is one of those disregarded effects where a reduction factor is recommended by design guidelines to take its contribution into account. It has been shown that the existing relationship for these reduction factors delivers an acceptable performance for vertical accelerations, while showing a less favorable performance for displacements. Then, a data-driven strategy is adopted in this study to propose easy-to-apply relationships for reduction factors of deflections, due to load distribution within the track. In this context, three different distributive lengths of triangular load footprints have been considered, namely 2.0, 2.5 and 3.0m. The procedure employed has trained and tested for more than 1200 train configurations, comprising conventional, articulated and regular vehicles, and including several tens of thousand data points for each distributive length. The performance observed in the new models revealed a considerable improvement with respect to the existing relationship. [ABSTRACT FROM AUTHOR]

Accurately identifying the axle loads of the moving train on the railway bridge can provide reliable information for assessing the safety of the train–bridge system. Bridge weigh-in-motion, namely, BWIM, is an effective approach for identifying the positions and weights of the train axles based on the monitored bridge responses. Existing BWIM methods generally focus on identifying the probable value of the axle weights instead of quantifying the identification uncertainty. To address this issue, a novel two-stage train load identification framework for the medium-small railway bridge is developed by combining the virtual axle theory and Bayesian inference. In the first stage, the axle configuration including the axle number, axle spacing and axle weight of the moving train, are estimated according to the modified virtual axle theory in which a clustering algorithm is embedded to automatically determine the axle number. In the second stage, the most probable value (MPV) and the uncertainty of the train axle weight are accurately identified using the Bayesian inference method which takes five types of error patterns into consideration. Finally, the proposed framework is verified using the data from numerical simulations and an in-situ railway bridge. Results show that the proposed framework can improve the accuracy of train load identification after quantifying the uncertainty of estimated axle weights and can confirm the confidence interval of the individual axle weight and gross train weight. [ABSTRACT FROM AUTHOR]

Various approaches to mechanical modeling are available in practice to calculate the dynamic response of railway bridges under high-speed traffic, differing significantly in their complexity and accuracy. Very simple models often overestimate the vibrations occurring in reality but are much more computationally efficient and dependent on only a few input parameters than more complex and accurate models. Modeling the high-speed train as a multi-body system can represent the beneficial vehicle-bridge interaction, but it requires knowledge of numerous vehicle parameters, which manufacturers rarely disclose. In contrast, the track-bridge interaction can also be depicted by a simple coupling beam modeling of the structure, requiring only a few input parameters representing the dynamic stiffness and damping of the track. Several calculations on different single-span steel girder bridges demonstrate the influence of different model variants and input parameters on the acceleration results of the structure. Additionally, an approach for determining a dynamic distribution of the train axle loads affecting the bridge depending on the assumed vertical track stiffness is presented. [ABSTRACT FROM AUTHOR]

Increasing the operating speed of trains in modern railway networks can induce greater actions on the infrastructure than was previously the case. This is due, in particular, to the occurrence of the resonance phenomenon in railway bridges, which is the focus of this paper and was not traditionally considered as a concern. In this context, the vibrations experienced by bridges, both vertical accelerations and displacements, are limited by design regulations to ensure that the safety of train passages over bridges and the comfort of passengers are guaranteed. However, previous studies have shown that the conventional dynamic design methods do not always result in conservative designs, nor is the achieved safety always consistent. Therefore, a probabilistic approach is adopted in this study to optimize the cross-section properties of various railway bridges in a wide design range including section types, span lengths, and number of spans. For this purpose, an iterative line search-based optimization problem is formulated to minimize the thickness of the cross-sections under consideration and consequently the linear mass of the bridges. Meanwhile, the associated failure probabilities of the above dynamic limit states are constrained to be less than the desired level of safety by incorporating them into the optimization constraint. In this regard, First-Order Reliability Method (FORM) is adopted to perform reliability analyses. Thus, the obtained results are presented in the form of design curves that may assist designers to select minimum cross-section dimensions satisfying the desired level of safety in terms of dynamic limit states. This objective can be achieved using the proposed design curves without the need to construct associated complex computational models and perform computationally expensive dynamic analyses. [ABSTRACT FROM AUTHOR]

Fully enclosed noise barriers (FENBs) are increasingly being installed on high-speed railway bridges for noise pollution control. However, the aerodynamic effects of high-speed trains passing FENBs have an adverse impact on barrier durability and generate micro-pressure waves. In this paper, a numerical model of a train passing an FENB on a bridge is established. The aerodynamic pressure distribution along the FENB is analyzed for both a single train and two trains passing one another. The propagation characteristics and evolution mechanisms of pressure waves are then investigated. The results show that the pressure is lower at the ends of the FENB and higher in the middle along the direction of train travel. The peak positive and negative pressures at the mid-span are 1.95 and 4.47 times higher than those at the ends, respectively. This distribution is caused by the propagation, superposition, reflection, and attenuation of pressure waves. Compression waves account for 78.9% of the peak positive pressure. An amplification factor must be considered when estimating the impact of two trains passing one another. Analysis of five pressure-relief schemes shows that arranging a single pressure-relief hole at a high-pressure location effectively alleviates the over-pressure in the FENB. The overall pressure-relief effect is an exponential function of the single opening area. Considering a constant opening area, arranging several relief holes at equal spacing optimizes the adverse pressure distribution compared with the single-hole relief scheme. The equivalent forces of the multi-hole scheme are 3.35% and 7.58% lower than in the single-hole scheme. [ABSTRACT FROM AUTHOR]

The Friesen bridge near Weener – Europes largest lift‐swing‐bridge In December 2015, the historic railway bridge over the Ems River near Weener was destroyed by a ship collision. The movable bridge part of the Friesen bridge, a rolling bascule bridge (Scherzer bridge) was so severely damaged that it could not be repaired. After an intensive political discourse, it was decided to rebuild the bridge. A feasibility study determined that, considering all conditions, the reconstruction of the Friesenbrücke as a lift‐swing bridge is the preferred option. The bridge structure of the Friesenbrücke has a total length of 337 m, with the centerpiece being the approx. 145 m long movable truss section of the lift‐swing bridge. The new Friesenbrücke provides a clear width of 56.60 m for shipping and meets the safety and ease‐of‐navigation requirements for all affected traffic routes. The new Friesenbrücke in the northwest of Lower Saxony is a major project that is unique in its structural dimensions and logistical conditions. It will become the largest lift‐swing bridge for railway traffic in Europe. [ABSTRACT FROM AUTHOR]

Of the 100,000 railroad bridges in the United States, 50% are over 100 years old. Many of these bridges do not meet the minimum vertical clearance standards, making them susceptible to impact from over-height vehicles. The impact can cause structural damage and unwanted disruption to railroad bridge services; rapid notification of the railroad authorities is crucial to ensure that the bridges are safe for continued use and to affect timely repairs. Therefore, researchers have developed approaches to identify these impacts on railroad bridges. Some recent approaches use machine learning to more effectively identify impacts from the sensor data. Typically, the collected sensor data are transmitted to a central location for processing. However, the challenge with this centralized approach is that the transfer of data to a central location can take considerable time, which is undesirable for time-sensitive events, like impact detection, that require a rapid assessment and response to potential damage. To address the challenges posed by the centralized approach, this study develops a framework for edge implementation of machine-learning predictions on wireless smart sensors. Wireless sensors are used because of their ease of installation and lower costs compared to their wired counterparts. The framework is implemented on the Xnode wireless smart sensor platform, thus bringing artificial intelligence models directly to the sensor nodes and eliminating the need to transfer data to a central location for processing. This framework is demonstrated using data obtained from events on a railroad bridge near Chicago; results illustrate the efficacy of the proposed edge computing framework for such time-sensitive structural health monitoring applications. [ABSTRACT FROM AUTHOR]

The effective monitoring of railway facilities is crucial for safety and operational efficiency. This study proposes an enhanced remote monitoring technique for railway facilities, specifically bridges, using satellite radar InSAR (Interferometric Synthetic Aperture Radar) technology. Previous studies faced limitations such as insufficient data points and challenges with topographical and structural variations. Our approach addresses these issues by analysing displacements from 30 images captured by the X-band SAR satellite, TerraSAR-X, over two years. We tested each InSAR parameter to develop an optimal set of parameters, applying the technique to a post-tensioned PSC (pre-stressed concrete) box bridge. Our findings revealed a recurring arch-shaped elevation along the bridge, attributed to temporal changes and long-term deformation. Further analysis showed a strong correlation between this deformation pattern and average surrounding temperature. This indicates that our technique can effectively identify micro-displacements due to temperature changes and structural deformation. Thus, the technique provides a theoretical foundation for improved SAR monitoring of large-scale social overhead capital (SOC) facilities, ensuring efficient maintenance and management. [ABSTRACT FROM AUTHOR]