To ensure the compatibility between rolling stock and infrastructure when dynamically assessing railway bridges under high-speed traffic,the damping properties considered in the calculation model significantly influen...To ensure the compatibility between rolling stock and infrastructure when dynamically assessing railway bridges under high-speed traffic,the damping properties considered in the calculation model significantly influence the predicted acceleration amplitude at resonance.However,due to the normative specifications of EN 1991-2,which are considered to be overly conservative,damping factors that are far below the actual damping have to be used when predicting vibrations of railway bridges,which means that accelerations at resonance tend to be overestimated to an uneconomical extent.Comparisons between damping factors prescribed by the standard and those identified based on in situ structure measurements always reveal a large discrepancy between reality and regulation.Given this background,this contribution presents a novel approach for defining the damping factor of railway bridges with ballasted tracks,where the damping factor for bridges is mathematically determined based on three different two-dimensional mechanical models.The basic principle of the approach for mathematically determining the damping factor is to separately define and superimpose the dissipative contributions of the supporting structure(including the substructure)and the superstructure.Using the results of a measurement campaign on 15 existing steel railway bridges in the Austrian rail network,the presented mechanical models are calibrated,and by analysing the energy dissipation in the ballasted track,guiding principles for practical application are defined.This guideline is intended to establish an alternative to the currently valid specifications of EN 1991-2,enabling the damping factor of railway bridges to be assessed in a realistic range by mathematical calculation and thus without the need for extensive in situ measurements on the individual structure.In this way,the existing potential of the infrastructure with regard to the damping properties of bridges can be utilised.This contribution focuses on steel bridges,but the mathematical approach for determining the damping factor applies equally to other bridge types(concrete,composite,or filler beam).展开更多
Tunneling diodes hold significant promise for future rectification in the terahertz(THz)and visible light spectra,thanks to their femtosecond-scale transit-time tunneling capabilities.In this work,TiN/ZnO/Pt fin tunne...Tunneling diodes hold significant promise for future rectification in the terahertz(THz)and visible light spectra,thanks to their femtosecond-scale transit-time tunneling capabilities.In this work,TiN/ZnO/Pt fin tunneling diodes(FTDs)with tunneling distances of 10 and 5 nm are fabricated,which demonstrate remarkable characteristics,including ultrahigh asymmetry(1.6×10^(4)for 10 nm device and 1.6×10^(3) for 5 nm device),high responsivity(25.3 V^(-1) for 10 nm device and 28.3 V^(-1) for 5 nm device)at zero bias,surpassing the thermal voltage limit of conventional Schottky diodes,and low turn-on voltage(V_(on))of approximately 100 mV for both devices,making them ideal for power conversion applications.Using technology computer-aided design(TCAD)simulations,the observed asymmetry in electronic transport is attributed to the transition between Fowler-Nordheim tunneling(FNT)and trap-assisted tunneling(TAT)under different biasing conditions,as illustrated by the corresponding energy band profiles.Furthermore,by integrating the FTDs,a rectifier bridge circuit is designed and exhibits full-wave rectification behavior,validated through SPICE simulations for THz-band operations.This advancement offers a highly efficient solution for THz-band energy conversion and effective detection applications.展开更多
In the Kigongo area of Mwanza Region,northwest Tanzania,fishmonger Neema Aisha remembers how the morning’s fresh catch would sour while she queued for the ferry,putting her business at risk.
To examine stress redistribution phenomena in bridges subjected to varying operational conditions,this study conducts a comprehensive analysis of three years of monitoring data from a 153-m double-deck road–rail stee...To examine stress redistribution phenomena in bridges subjected to varying operational conditions,this study conducts a comprehensive analysis of three years of monitoring data from a 153-m double-deck road–rail steel arch bridge.An initial statistical comparison of sensor data distributions reveals clear temporal variations in stress redistribution patterns.XGBoost(eXtreme Gradient Boosting),a gradient-boosting machine learning(ML)algorithm,was employed not only for predictive modeling but also to uncover the underlying mechanisms of stress evolution.Unlike traditional numerical models that rely on extensive assumptions and idealizations,XGBoost effectively captures nonlinear and time-varying relationships between stress states and operational/environmental factors,such as temperature,traffic load,and structural geometry.This approach allows for the identification of critical periods and conditions under which stress redistribution becomes significant.Results indicate a clear shift of stress concentrations frombeamends toward mid-span regions following the commencement of metro operations,reflecting both structural adaptation and localized overstress near arch ribs.Furthermore,the model generates robust predictions of stress evolution,demonstrating potential applications in early warning systems and fatigue risk assessment.This work represents the first application of interpretable gradient-boosting techniques to stress redistribution modeling in double-deck bridges.In addition,a Stress Redistribution Index(SRI)is proposed,derived from this monitoring study and finite-element-based transverse load distributions,to quantify temporal stress shifts between midspan and edge beams.The results provide both theoretical contributions and practical guidance for the design,inspection,and maintenance of complex bridge structures.展开更多
This study proposes a new post-tensioned precast bridge column(PT-PBC)with a socket connection.Compared to conventional PBCs connected by PT tendons,the combination of the PT tendons with the socket connection can avo...This study proposes a new post-tensioned precast bridge column(PT-PBC)with a socket connection.Compared to conventional PBCs connected by PT tendons,the combination of the PT tendons with the socket connection can avoid tensioning the PT tendons on site,which further accelerates construction speed while improving construction quality and safety.In addition,compared to conventional PBCs with a socket connection,a rocking interface can avoid the formation of a plastic hinge in a column,which greatly alleviates seismic damage to that area.One specimen for quasi-static testing is used to validate the feasibility of this connection type.Subsequently,finite element models(FEM)are established to systematically predict the responses of the proposed columns under lateral cyclic loading.The accuracy of the FEM is verified through quasistatic testing.Next,the influences of the key design parameters of the PT-PBC,including the area ratio and prestress level of the PT tendons,the area ratio of energy dissipation(ED)steel rebars,and the total axial compression ratio on the seismic performances of PT-PBC are systematically investigated.The use of shape memory alloy(SMA)rods as energy dissipation devices and their performances also are investigated.The results show that increasing the area ratio and prestress level of PT tendons has an overall positive impact on the self-centering capacity of the column.The prestress level of PT tendons should be kept between 35%and 55%,depending on different conditions.The total compression axial ratio of the columns should be maintained between 0.3 and 0.4.Both ED steel rebars and SMA rods can boost the column’s energy dissipation capacity,while SMA rods can reduce residual deformation due to their inherent mechanical properties.展开更多
The goal of this paper is to investigate the long-time dynamics of solutions to a Kirchhoff type suspension bridge equation with nonlinear damping and memory term.For this problem we establish the well-posedness and e...The goal of this paper is to investigate the long-time dynamics of solutions to a Kirchhoff type suspension bridge equation with nonlinear damping and memory term.For this problem we establish the well-posedness and existence of uniform attractor under some suitable assumptions on the nonlinear term g(u),the nonlinear damping f(u_(t))and the external force h(x,t).Specifically,the asymptotic compactness of the semigroup is verified by the energy reconstruction method.展开更多
The main cable is the primary load-bearing component of a suspension bridge,continuously exposed to harsh environmental conditions,such as wind and rain,throughout the year.These adverse conditions contribute to varyi...The main cable is the primary load-bearing component of a suspension bridge,continuously exposed to harsh environmental conditions,such as wind and rain,throughout the year.These adverse conditions contribute to varying degrees of degradation and damage to the main cable,necessitating regular inspections to prevent catastrophic failures.Traditional manual inspection methods not only suffer from low efficiency but also pose significant safety risks to personnel.To address these challenges and ensure the safe and effective inspection of suspension bridge main cables,this study introduces a novel cooperative climbing robot,designated as Main Cable Robot Version II(CCRobot-M-II),inspired by the locomotion of the inchworm.The robot employs an alternating opening and closing mechanism of four gripper sets,mimicking the inchworm's movement to achieve efficient crawling along the suspension bridge handrails.This paper provides a comprehensive analysis of the structural design,key components,and motion mechanisms of CCRobot-M-II.A detailed force analysis of the robot's crawling process is also presented,followed by the design of the control system and the development of an efficient motion control algorithm.Laboratory experiments demonstrate that the robot achieves a positional error of 00.64%during crawling,with a maximum average crawling speed of 7.6 m/min.Furthermore,the biomimetic design enables the robot to overcome obstacles up to 30 mm in height and possess the capability to handle suspension bridge cables with spans ranging from 740 to 1100 mm.Finally,CCRobot-M-II successfully conducted an inspection of the main cable on a suspension bridge,marking the world's first successful deployment of a climbing robot for main cable inspection on a suspension bridge.展开更多
The spatial offset of bridge has a significant impact on the safety,comfort,and durability of high-speed railway(HSR)operations,so it is crucial to rapidly and effectively detect the spatial offset of operational HSR ...The spatial offset of bridge has a significant impact on the safety,comfort,and durability of high-speed railway(HSR)operations,so it is crucial to rapidly and effectively detect the spatial offset of operational HSR bridges.Drive-by monitoring of bridge uneven settlement demonstrates significant potential due to its practicality,cost-effectiveness,and efficiency.However,existing drive-by methods for detecting bridge offset have limitations such as reliance on a single data source,low detection accuracy,and the inability to identify lateral deformations of bridges.This paper proposes a novel drive-by inspection method for spatial offset of HSR bridge based on multi-source data fusion of comprehensive inspection train.Firstly,dung beetle optimizer-variational mode decomposition was employed to achieve adaptive decomposition of non-stationary dynamic signals,and explore the hidden temporal relationships in the data.Subsequently,a long short-term memory neural network was developed to achieve feature fusion of multi-source signal and accurate prediction of spatial settlement of HSR bridge.A dataset of track irregularities and CRH380A high-speed train responses was generated using a 3D train-track-bridge interaction model,and the accuracy and effectiveness of the proposed hybrid deep learning model were numerically validated.Finally,the reliability of the proposed drive-by inspection method was further validated by analyzing the actual measurement data obtained from comprehensive inspection train.The research findings indicate that the proposed approach enables rapid and accurate detection of spatial offset in HSR bridge,ensuring the long-term operational safety of HSR bridges.展开更多
Designing a heterogeneous interface to improve the kinetics of electrocatalysts represents an effective yet challenging approach for enhancing the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).Herei...Designing a heterogeneous interface to improve the kinetics of electrocatalysts represents an effective yet challenging approach for enhancing the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).Herein,a simple MOF-assisted etching-pyrolysis strategy is proposed to fabricate an advanced Mott-Schottky(M–S)electrocatalyst composed of Co/CeO_(2)hetero-nanoparticles embedded within N-doped hollow carbon nanoboxes(H-Co/CeO_(2)@NCBs).Notably,the interfacial Co–O–Ce bond bridging productively facilitates the electron transfer and modulates the charge distribution of the active center,thereby contributing to the ORR/OER kinetics.As expected,the optimal M–S H-Co/CeO_(2)@NCBs catalyst exhibits promising bifunctional electrocatalytic activity with a small potential discrepancy of 0.65 V.Theoretical calculations reveal that the built-in electric field in the M–S heterojunction promotes electron transfer in oxygen electrocatalysis and the interfacial bridge-induced electron redistribution optimizes the adsorption/desorption of the oxygen intermediates,leading to reduced activation energy for the bifunctional ORR/OER reactions.Importantly,H-Co/CeO_(2)@NCBs-assembled Zn-air battery(ZAB)delivers high power density(179.8 mW cm^(−2))and long-term stability(400 h).Furthermore,the assembled flexible solid-state ZAB with H-Co/CeO_(2)@NCBs cathode also exhibits excellent charge–discharge reversibility and flexibility at various bending angles.This work provides a novel perspective on developing efficient and stable M–S bifunctional oxygen electrocatalysts.展开更多
A monolithic integrated full-wave bridge rectifier consisted of horizontal Schottky-barrier diodes(SBD)is prepared based on 100 nm ultra-thin β-Ga_(2)O_(3)and demonstrated the solar-blind UV(SUV)light-modulated chara...A monolithic integrated full-wave bridge rectifier consisted of horizontal Schottky-barrier diodes(SBD)is prepared based on 100 nm ultra-thin β-Ga_(2)O_(3)and demonstrated the solar-blind UV(SUV)light-modulated characteristics.Under SUV light illumination,the rectifier has the excellent full-wave rectification characteristics for the AC input signals of 5,12,and 24 V with different frequencies.Further,experimental results confirmed the feasibility of continuously tuning the rectified output through SUV light-encoding.This work provides valuable insights for the development of optically programmable Ga_(2)O_(3)ACDC converters.展开更多
The Beipanjiang Bridge sits over 565 meters above the Beipan River Valley nestled between two very steep cliffs,making it the world's highest bridge.Also known as the Duge Bridge or“China's Impossible Enginee...The Beipanjiang Bridge sits over 565 meters above the Beipan River Valley nestled between two very steep cliffs,making it the world's highest bridge.Also known as the Duge Bridge or“China's Impossible Engineering Feat”,the world's highest bridge may not look that impressive at first sight,but it is a testament to Chinese engineering and innovation.展开更多
Most studies have analyzed the aerodynamic characteristics and wind-train(vehicle)-bridge coupled vibration response of trains or vehicles on bridges of a certain structural system,while few comparative studies have b...Most studies have analyzed the aerodynamic characteristics and wind-train(vehicle)-bridge coupled vibration response of trains or vehicles on bridges of a certain structural system,while few comparative studies have been carried out on the wind-train-bridge coupled vibration response on bridges of three different structural systems.This paper takes the main span 1120 m dual-purpose highway-railway bridge as the engineering background,and studies the three bridge types of(122+1120+90+92)m suspension bridge,(130+432+1120+432+130)m cable-stayed bridge and(92+210+1120+210+92)m cable-stayed-suspension collaborative system bridge.The trend of the maximum value of the train dynamic response to the wind-train-bridge coupling of the three structural system bridges as well as the speed thresholds are compared and analyzed,and conclusions are drawn:1)Under the same speed,the maximum value of train safety indexes in three types of bridges increases with the increase of wind speed.2)Under the same wind speed,the safety and smoothness indicators of trains in three types of bridges without wind barriers rank in the order of cable-stayed suspension collaborative system bridge>cable-stayed bridge>suspension bridge.3)At low wind speeds(≤15 m/s),a 3.0 m wind barrier has negligible effect on speed thresholds.The safety ranking of structural systems remains unchanged:cable-stayed-suspension collaborative system bridge>cable-stayed bridge>suspension bridge.4)At high wind speeds(≥20 m/s),the 3.0 m wind barrier can increase the train speed threshold for bridges within the same structural system.The safety ranking of the three bridge types(3.0 m 30%wind barrier)remains unchanged:cable-stayed suspension collaborative system bridge>cable-stayed bridge>suspension bridge.This study represents the first systematic comparative analysis of wind speed critical values and performance ratings across three distinct bridge structural systems.展开更多
Bridge pressure flow scour at clear water threshold condition is studied theoretically and experimentally.The flume experiments reveal that the measured scour profiles under a bridge are more or less 2-dimensional;all...Bridge pressure flow scour at clear water threshold condition is studied theoretically and experimentally.The flume experiments reveal that the measured scour profiles under a bridge are more or less 2-dimensional;all the measured scour profiles can be described by two similarity equations,where the horizontal distance is scaled by the deck width while the local scour by the maximum scour depth;the maximum scour position is located just under the bridge about 15% deck width from the downstream deck edge;the scour begins at about one deck width upstream the bridge while the deposition occurs at about 2.5 deck widths downstream the bridge;and the maximum scour depth decreases with increas-ing sediment size,but increases with deck inundation.The theoretical analysis shows that:bridge scour can be divided into three cases,i.e.downstream unsubmerged,partially submerged,and totally submerged.For downstream unsubmerged flows,the maximum bridge scour depth is an open-channel problem where the conventional methods in terms of critical velocity or bed shear stress can be applied;for partially and totally submerged flows,the equilibrium maximum scour depth can be described by a scour and an inundation similarity number,which has been confirmed by experiments with two decks and two sediment sizes.For application,a design and field evaluation procedure with examples is presented,including the maximum scour depth and scour profile.展开更多
Much of the research has focused on identifying bridge frequencies for health monitoring,while the bridge damping ratio also serves as an important factor in damage detection.This study presents an enhanced method for...Much of the research has focused on identifying bridge frequencies for health monitoring,while the bridge damping ratio also serves as an important factor in damage detection.This study presents an enhanced method for identifying bridge damping ratios using a two-axle,three-mass test vehicle,relying on wheel responses captured by only two mounted sensors.Damping ratio estimation formulas are derived using both the Hilbert Transform(HT)and Wavelet Transform(WT),with a consistent formulation that confirms accurate estimation is achievable with minimal instrumentation,particularly when addressing the support effect.A comparative analysis of the two signal processing techniques reveals the superior performance of WT in identifying bridge damping ratios.The effectiveness of the proposed procedure and formulas is validated through a detailed parametric study,demonstrating robustness across bridges with varying modal damping ratios and different spans using minimal sensors.Moreover,the present study shows that responses from only the first two spans of a multi-span bridge are sufficient for reliable damping estimation,underscoring the practicality and scalability of the procedure for structural health monitoring applications.展开更多
Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the...Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the approach bridge.For long-span railway bridges,it must also be coordinated with rail expansion joint(REJ),which is necessary to accommodate the expansion and contraction of,and reducing longitudinal stress in,the rails.The main aim of this study is to present analysis of recent developments in the research and application of BEJs in high-speed railway(HSR)long-span bridges in China,and to propose a performance-based integral design method for BEJs used with REJs,from both theoretical and engineering perspectives.Design/methodology/approach–The study first presents a summary on the application and maintenance of BEJs in HSR long-span bridges in China representing an overview of their state of development.Results of a survey of typical BEJ faults were analyzed,and field testing was conducted on a railway cable-stayed bridge in order to obtain information on the major mechanical characteristics of its BEJ under train load.Based on the above,a performance-based integral design method for BEJs with maximum expansion range 1600 mm(±800 mm),was proposed,covering all stages from overall conceptual design to consideration of detailed structural design issues.The performance of the novel BEJ design thus derived was then verified via theoretical analysis under different scenarios,full-scale model testing,and field testing and commissioning.Findings–Two major types of BEJs,deck-type and through-type,are used in HSR long-span bridges in China.Typical BEJ faults were found to mainly include skewness of steel sleepers at the bridge gap,abnormally large longitudinal frictional resistance,and flexural deformation of the scissor mechanisms.These faults influence BEJ functioning,and thus adversely affect track quality and train running performance at the beam end.Due to their simple and integral structure,deck-type BEJs with expansion range 1200 mm(±600 mm)or less have been favored as a solution offering improved operational conditions,and have emerged as a standard design.However,when the expansion range exceeds the above-mentioned value,special design work becomes necessary.Therefore,based on engineering practice,a performance-based integral design method for BEJs used with REJs was proposed,taking into account four major categories of performance requirements,i.e.,mechanical characteristics,train running quality,durability and insulation performance.Overall BEJ design must mainly consider component strength and the overall stiffness of BEJ;the latter factor in particular has a decisive influence on train running performance at the beam end.Detailed BEJ structural design must stress minimization of the frictional resistance of its sliding surface.The static and dynamic performance of the newlydesigned BEJ with expansion range 1600 mm have been confirmed to be satisfactory,via numerical simulation,full-scale model testing,and field testing and commissioning.Originality/value–This research provides a broad overview of the status of BEJs with large expansion range in HSR long-span bridges in China,along with novel insights into their design.展开更多
Safety evaluation of a bridge under Moving Abnormal Indivisible Loads(MAILs)directly relates to whether an oversized and/or overweight Large-Cargo Transportation(LCT)vehicle is permitted to pass the bridge.Safety eval...Safety evaluation of a bridge under Moving Abnormal Indivisible Loads(MAILs)directly relates to whether an oversized and/or overweight Large-Cargo Transportation(LCT)vehicle is permitted to pass the bridge.Safety evaluation can be updated by fusing bridge inspection data and load test data,but there are two fundamental difficulties in updating.The first difficulty is to develop an updating scheme to utilize the unstructured inspection data.The second difficulty is to develop a successive updating scheme using load test data based on the previous updating results of the inspection data.This paper proposed a framework,consisting of three modules,to tackle these two fundamental difficulties of updating.Module one is the updating of Finite Element Model(FEM)and resistance of the bridge based on fusing bridge inspection data and load test data.The first difficulty in utilizing the unstructured inspection data is tackled by introducing updating guidelines using the unstructured inspection data.The second difficulty in conducting a successively updating scheme using load test data based on previous updating results is tackled by Bayesian updating.Module two is the simulation of a bridge under a MAIL,updating the ProbabilityDensity Functions(PDFs)of Load Effects(LEs)of critical sections of critical components based on the updated FEM and the givenMAIL.Module three is the safety evaluation of the bridge based on the load-bearing capacity index and reliability index,updating indices based on the updated resistance and LE.Theillustrative examples consist of a simulated example and an engineering example,demonstrating the effectiveness of the proposed framework.The simulated example is the safety evaluation of a bridge under a MAIL,and the engineering example is the safety evaluation of the Anning River Bridge of the Yazhong-Jiangxi Ultra-High-Voltage Direct Current(UHVDC)MAIL project.The results show that it is crucial to fuse bridge inspection data and load test data for updating the safety evaluation of bridges under MAILs.展开更多
The effect of seismic directionality is crucial for curved bridges,a subject generally overlooked in seismic vulnerability analysis.This paper focuses on seismic fragility development as a function of seismic incidenc...The effect of seismic directionality is crucial for curved bridges,a subject generally overlooked in seismic vulnerability analysis.This paper focuses on seismic fragility development as a function of seismic incidence directions for a geometrically curved bridge.A series of non-linear time history analyses were carried out for a representative finite element model of the bridge by considering actual ground motions.For reliable seismic demand models,a total of eleven intensity measures(IM)were analyzed based on optimality metrics.To quantify the sensitivity of fragility functions to input incidence directions,fragility surfaces were developed throughout the horizontal plane by considering spectral acceleration at one second(Sa_(1.0))as the optimal IM.Results show that the optimal IM ranking is insignificantly influenced by seismic directionality.However,seismic orientation influences fragility,which intensifies in higher damage states,particularly for piers.For a bridge system,the differences in median demand corresponding to the least and most vulnerable direction for slight,moderate,extensive,and collapse states are about 9.0%,7.31%,10.32%,and 11.60%,respectively.These results imply that while evaluating the vulnerability of curved bridges,the optimality of IM in demand estimation and the impact of seismic directionality should not be disregarded.展开更多
From complicated overpasses that defy(违抗)engineering conventions to suspended“river highways”,China is internationally recognized for its innovative infrastructure.Another example of the nation's fearless appr...From complicated overpasses that defy(违抗)engineering conventions to suspended“river highways”,China is internationally recognized for its innovative infrastructure.Another example of the nation's fearless approach to building and design is the temporary suspension bridge.展开更多
The detection of surface defects in concrete bridges using deep learning is of significant importance for reducing operational risks,saving maintenance costs,and driving the intelligent transformation of bridge defect...The detection of surface defects in concrete bridges using deep learning is of significant importance for reducing operational risks,saving maintenance costs,and driving the intelligent transformation of bridge defect detection.In contrast to the subjective and inefficient manual visual inspection,deep learning-based algorithms for concrete defect detection exhibit remarkable advantages,emerging as a focal point in recent research.This paper comprehensively analyzes the research progress of deep learning algorithms in the field of surface defect detection in concrete bridges in recent years.It introduces the early detection methods for surface defects in concrete bridges and the development of deep learning.Subsequently,it provides an overview of deep learning-based concrete bridge surface defect detection research from three aspects:image classification,object detection,and semantic segmentation.The paper summarizes the strengths and weaknesses of existing methods and the challenges they face.Additionally,it analyzes and prospects the development trends of surface defect detection in concrete bridges.展开更多
基金funded by the Austrian Federal Railways(ÖBB Infrastruktur AG)in the context of the research project‘VeMoDiss’(acronym)。
文摘To ensure the compatibility between rolling stock and infrastructure when dynamically assessing railway bridges under high-speed traffic,the damping properties considered in the calculation model significantly influence the predicted acceleration amplitude at resonance.However,due to the normative specifications of EN 1991-2,which are considered to be overly conservative,damping factors that are far below the actual damping have to be used when predicting vibrations of railway bridges,which means that accelerations at resonance tend to be overestimated to an uneconomical extent.Comparisons between damping factors prescribed by the standard and those identified based on in situ structure measurements always reveal a large discrepancy between reality and regulation.Given this background,this contribution presents a novel approach for defining the damping factor of railway bridges with ballasted tracks,where the damping factor for bridges is mathematically determined based on three different two-dimensional mechanical models.The basic principle of the approach for mathematically determining the damping factor is to separately define and superimpose the dissipative contributions of the supporting structure(including the substructure)and the superstructure.Using the results of a measurement campaign on 15 existing steel railway bridges in the Austrian rail network,the presented mechanical models are calibrated,and by analysing the energy dissipation in the ballasted track,guiding principles for practical application are defined.This guideline is intended to establish an alternative to the currently valid specifications of EN 1991-2,enabling the damping factor of railway bridges to be assessed in a realistic range by mathematical calculation and thus without the need for extensive in situ measurements on the individual structure.In this way,the existing potential of the infrastructure with regard to the damping properties of bridges can be utilised.This contribution focuses on steel bridges,but the mathematical approach for determining the damping factor applies equally to other bridge types(concrete,composite,or filler beam).
基金National Key Research and Development Program of China(2024YFA1410700,2021YFA1200700)National Natural Science Foundation of China(62474065,T2222025,62174053)+3 种基金Natural Science Foundation of Chongqing(CSTB2024NSCQ-JQX0005)Shanghai Science and Technology Innovation Action Plan(24QA2702300,24YF2710400)National Postdoctoral Program(GZB20240225)Fundamental Research Funds for the Central Universities。
文摘Tunneling diodes hold significant promise for future rectification in the terahertz(THz)and visible light spectra,thanks to their femtosecond-scale transit-time tunneling capabilities.In this work,TiN/ZnO/Pt fin tunneling diodes(FTDs)with tunneling distances of 10 and 5 nm are fabricated,which demonstrate remarkable characteristics,including ultrahigh asymmetry(1.6×10^(4)for 10 nm device and 1.6×10^(3) for 5 nm device),high responsivity(25.3 V^(-1) for 10 nm device and 28.3 V^(-1) for 5 nm device)at zero bias,surpassing the thermal voltage limit of conventional Schottky diodes,and low turn-on voltage(V_(on))of approximately 100 mV for both devices,making them ideal for power conversion applications.Using technology computer-aided design(TCAD)simulations,the observed asymmetry in electronic transport is attributed to the transition between Fowler-Nordheim tunneling(FNT)and trap-assisted tunneling(TAT)under different biasing conditions,as illustrated by the corresponding energy band profiles.Furthermore,by integrating the FTDs,a rectifier bridge circuit is designed and exhibits full-wave rectification behavior,validated through SPICE simulations for THz-band operations.This advancement offers a highly efficient solution for THz-band energy conversion and effective detection applications.
文摘In the Kigongo area of Mwanza Region,northwest Tanzania,fishmonger Neema Aisha remembers how the morning’s fresh catch would sour while she queued for the ferry,putting her business at risk.
基金supported by the Key Technologies Research and Development Program under Grant 2021YFB1600300.
文摘To examine stress redistribution phenomena in bridges subjected to varying operational conditions,this study conducts a comprehensive analysis of three years of monitoring data from a 153-m double-deck road–rail steel arch bridge.An initial statistical comparison of sensor data distributions reveals clear temporal variations in stress redistribution patterns.XGBoost(eXtreme Gradient Boosting),a gradient-boosting machine learning(ML)algorithm,was employed not only for predictive modeling but also to uncover the underlying mechanisms of stress evolution.Unlike traditional numerical models that rely on extensive assumptions and idealizations,XGBoost effectively captures nonlinear and time-varying relationships between stress states and operational/environmental factors,such as temperature,traffic load,and structural geometry.This approach allows for the identification of critical periods and conditions under which stress redistribution becomes significant.Results indicate a clear shift of stress concentrations frombeamends toward mid-span regions following the commencement of metro operations,reflecting both structural adaptation and localized overstress near arch ribs.Furthermore,the model generates robust predictions of stress evolution,demonstrating potential applications in early warning systems and fatigue risk assessment.This work represents the first application of interpretable gradient-boosting techniques to stress redistribution modeling in double-deck bridges.In addition,a Stress Redistribution Index(SRI)is proposed,derived from this monitoring study and finite-element-based transverse load distributions,to quantify temporal stress shifts between midspan and edge beams.The results provide both theoretical contributions and practical guidance for the design,inspection,and maintenance of complex bridge structures.
基金Natural Science Foundation of China under Grant No.52178449,the Beijing Natural Science Foundation under Grant No.8234060the Innovation Center of Beijing Association for Science and Technology。
文摘This study proposes a new post-tensioned precast bridge column(PT-PBC)with a socket connection.Compared to conventional PBCs connected by PT tendons,the combination of the PT tendons with the socket connection can avoid tensioning the PT tendons on site,which further accelerates construction speed while improving construction quality and safety.In addition,compared to conventional PBCs with a socket connection,a rocking interface can avoid the formation of a plastic hinge in a column,which greatly alleviates seismic damage to that area.One specimen for quasi-static testing is used to validate the feasibility of this connection type.Subsequently,finite element models(FEM)are established to systematically predict the responses of the proposed columns under lateral cyclic loading.The accuracy of the FEM is verified through quasistatic testing.Next,the influences of the key design parameters of the PT-PBC,including the area ratio and prestress level of the PT tendons,the area ratio of energy dissipation(ED)steel rebars,and the total axial compression ratio on the seismic performances of PT-PBC are systematically investigated.The use of shape memory alloy(SMA)rods as energy dissipation devices and their performances also are investigated.The results show that increasing the area ratio and prestress level of PT tendons has an overall positive impact on the self-centering capacity of the column.The prestress level of PT tendons should be kept between 35%and 55%,depending on different conditions.The total compression axial ratio of the columns should be maintained between 0.3 and 0.4.Both ED steel rebars and SMA rods can boost the column’s energy dissipation capacity,while SMA rods can reduce residual deformation due to their inherent mechanical properties.
基金Supported by the National Natural Science Foundation of China(Grant Nos.11961059,1210502)the University Innovation Project of Gansu Province(Grant No.2023B-062)the Gansu Province Basic Research Innovation Group Project(Grant No.23JRRA684).
文摘The goal of this paper is to investigate the long-time dynamics of solutions to a Kirchhoff type suspension bridge equation with nonlinear damping and memory term.For this problem we establish the well-posedness and existence of uniform attractor under some suitable assumptions on the nonlinear term g(u),the nonlinear damping f(u_(t))and the external force h(x,t).Specifically,the asymptotic compactness of the semigroup is verified by the energy reconstruction method.
基金Shenzhen Science and Technology Program(Grant No.20220817171811004)(Grant No.RCBS20231211090816033)+4 种基金the Major Key Project of PCL,China under Grant PCL2025A13Longgang District,Shenzhen's"Ten-Action Plan"for Supporting Innovation Projects(Grant No.LGKCSDPT2024002,LGKCSDPT2024003,LGKCSDPT2024004)the"Zhiguo"Action of Guangxi Science and Technology Program(Grant No.ZG2503980003)Guangdong S&T Program under(Grant No.2025B0909040003)Guangdong Provincial Leading Talent Program(Grant No.2024TX08Z319).
文摘The main cable is the primary load-bearing component of a suspension bridge,continuously exposed to harsh environmental conditions,such as wind and rain,throughout the year.These adverse conditions contribute to varying degrees of degradation and damage to the main cable,necessitating regular inspections to prevent catastrophic failures.Traditional manual inspection methods not only suffer from low efficiency but also pose significant safety risks to personnel.To address these challenges and ensure the safe and effective inspection of suspension bridge main cables,this study introduces a novel cooperative climbing robot,designated as Main Cable Robot Version II(CCRobot-M-II),inspired by the locomotion of the inchworm.The robot employs an alternating opening and closing mechanism of four gripper sets,mimicking the inchworm's movement to achieve efficient crawling along the suspension bridge handrails.This paper provides a comprehensive analysis of the structural design,key components,and motion mechanisms of CCRobot-M-II.A detailed force analysis of the robot's crawling process is also presented,followed by the design of the control system and the development of an efficient motion control algorithm.Laboratory experiments demonstrate that the robot achieves a positional error of 00.64%during crawling,with a maximum average crawling speed of 7.6 m/min.Furthermore,the biomimetic design enables the robot to overcome obstacles up to 30 mm in height and possess the capability to handle suspension bridge cables with spans ranging from 740 to 1100 mm.Finally,CCRobot-M-II successfully conducted an inspection of the main cable on a suspension bridge,marking the world's first successful deployment of a climbing robot for main cable inspection on a suspension bridge.
基金sponsored by the National Natural Science Foundation of China(Grant No.52178100).
文摘The spatial offset of bridge has a significant impact on the safety,comfort,and durability of high-speed railway(HSR)operations,so it is crucial to rapidly and effectively detect the spatial offset of operational HSR bridges.Drive-by monitoring of bridge uneven settlement demonstrates significant potential due to its practicality,cost-effectiveness,and efficiency.However,existing drive-by methods for detecting bridge offset have limitations such as reliance on a single data source,low detection accuracy,and the inability to identify lateral deformations of bridges.This paper proposes a novel drive-by inspection method for spatial offset of HSR bridge based on multi-source data fusion of comprehensive inspection train.Firstly,dung beetle optimizer-variational mode decomposition was employed to achieve adaptive decomposition of non-stationary dynamic signals,and explore the hidden temporal relationships in the data.Subsequently,a long short-term memory neural network was developed to achieve feature fusion of multi-source signal and accurate prediction of spatial settlement of HSR bridge.A dataset of track irregularities and CRH380A high-speed train responses was generated using a 3D train-track-bridge interaction model,and the accuracy and effectiveness of the proposed hybrid deep learning model were numerically validated.Finally,the reliability of the proposed drive-by inspection method was further validated by analyzing the actual measurement data obtained from comprehensive inspection train.The research findings indicate that the proposed approach enables rapid and accurate detection of spatial offset in HSR bridge,ensuring the long-term operational safety of HSR bridges.
基金supported by the National Natural Science Foundation of China(U24A20550,52273264 and 52470073)the Key Project of the Heilongjiang Provincial Natural Science Foundation(ZD2024B001)Outstanding Youth Fund of Heilongjiang Province(JQ2022E005).
文摘Designing a heterogeneous interface to improve the kinetics of electrocatalysts represents an effective yet challenging approach for enhancing the oxygen reduction reaction(ORR)and oxygen evolution reaction(OER).Herein,a simple MOF-assisted etching-pyrolysis strategy is proposed to fabricate an advanced Mott-Schottky(M–S)electrocatalyst composed of Co/CeO_(2)hetero-nanoparticles embedded within N-doped hollow carbon nanoboxes(H-Co/CeO_(2)@NCBs).Notably,the interfacial Co–O–Ce bond bridging productively facilitates the electron transfer and modulates the charge distribution of the active center,thereby contributing to the ORR/OER kinetics.As expected,the optimal M–S H-Co/CeO_(2)@NCBs catalyst exhibits promising bifunctional electrocatalytic activity with a small potential discrepancy of 0.65 V.Theoretical calculations reveal that the built-in electric field in the M–S heterojunction promotes electron transfer in oxygen electrocatalysis and the interfacial bridge-induced electron redistribution optimizes the adsorption/desorption of the oxygen intermediates,leading to reduced activation energy for the bifunctional ORR/OER reactions.Importantly,H-Co/CeO_(2)@NCBs-assembled Zn-air battery(ZAB)delivers high power density(179.8 mW cm^(−2))and long-term stability(400 h).Furthermore,the assembled flexible solid-state ZAB with H-Co/CeO_(2)@NCBs cathode also exhibits excellent charge–discharge reversibility and flexibility at various bending angles.This work provides a novel perspective on developing efficient and stable M–S bifunctional oxygen electrocatalysts.
基金supported by Natural Science Basic Research Program of Shaanxi Province of China(Grant No.2023JCYB574)National Natural Science Foundation of China(Grant No.62204203)。
文摘A monolithic integrated full-wave bridge rectifier consisted of horizontal Schottky-barrier diodes(SBD)is prepared based on 100 nm ultra-thin β-Ga_(2)O_(3)and demonstrated the solar-blind UV(SUV)light-modulated characteristics.Under SUV light illumination,the rectifier has the excellent full-wave rectification characteristics for the AC input signals of 5,12,and 24 V with different frequencies.Further,experimental results confirmed the feasibility of continuously tuning the rectified output through SUV light-encoding.This work provides valuable insights for the development of optically programmable Ga_(2)O_(3)ACDC converters.
文摘The Beipanjiang Bridge sits over 565 meters above the Beipan River Valley nestled between two very steep cliffs,making it the world's highest bridge.Also known as the Duge Bridge or“China's Impossible Engineering Feat”,the world's highest bridge may not look that impressive at first sight,but it is a testament to Chinese engineering and innovation.
基金Project(52327810)supported by the National Natural Science Foundation of ChinaProject(51925808)supported by the National Natural Science Foundation for Distinguished Young Scholars of China+1 种基金Project(U1934209)supported by the Key Project of National Natural Science Foundation of ChinaProject(P2019G002)supported by the Science and Technology Research and Development Program of China National Railway Group Co.,Ltd。
文摘Most studies have analyzed the aerodynamic characteristics and wind-train(vehicle)-bridge coupled vibration response of trains or vehicles on bridges of a certain structural system,while few comparative studies have been carried out on the wind-train-bridge coupled vibration response on bridges of three different structural systems.This paper takes the main span 1120 m dual-purpose highway-railway bridge as the engineering background,and studies the three bridge types of(122+1120+90+92)m suspension bridge,(130+432+1120+432+130)m cable-stayed bridge and(92+210+1120+210+92)m cable-stayed-suspension collaborative system bridge.The trend of the maximum value of the train dynamic response to the wind-train-bridge coupling of the three structural system bridges as well as the speed thresholds are compared and analyzed,and conclusions are drawn:1)Under the same speed,the maximum value of train safety indexes in three types of bridges increases with the increase of wind speed.2)Under the same wind speed,the safety and smoothness indicators of trains in three types of bridges without wind barriers rank in the order of cable-stayed suspension collaborative system bridge>cable-stayed bridge>suspension bridge.3)At low wind speeds(≤15 m/s),a 3.0 m wind barrier has negligible effect on speed thresholds.The safety ranking of structural systems remains unchanged:cable-stayed-suspension collaborative system bridge>cable-stayed bridge>suspension bridge.4)At high wind speeds(≥20 m/s),the 3.0 m wind barrier can increase the train speed threshold for bridges within the same structural system.The safety ranking of the three bridge types(3.0 m 30%wind barrier)remains unchanged:cable-stayed suspension collaborative system bridge>cable-stayed bridge>suspension bridge.This study represents the first systematic comparative analysis of wind speed critical values and performance ratings across three distinct bridge structural systems.
文摘Bridge pressure flow scour at clear water threshold condition is studied theoretically and experimentally.The flume experiments reveal that the measured scour profiles under a bridge are more or less 2-dimensional;all the measured scour profiles can be described by two similarity equations,where the horizontal distance is scaled by the deck width while the local scour by the maximum scour depth;the maximum scour position is located just under the bridge about 15% deck width from the downstream deck edge;the scour begins at about one deck width upstream the bridge while the deposition occurs at about 2.5 deck widths downstream the bridge;and the maximum scour depth decreases with increas-ing sediment size,but increases with deck inundation.The theoretical analysis shows that:bridge scour can be divided into three cases,i.e.downstream unsubmerged,partially submerged,and totally submerged.For downstream unsubmerged flows,the maximum bridge scour depth is an open-channel problem where the conventional methods in terms of critical velocity or bed shear stress can be applied;for partially and totally submerged flows,the equilibrium maximum scour depth can be described by a scour and an inundation similarity number,which has been confirmed by experiments with two decks and two sediment sizes.For application,a design and field evaluation procedure with examples is presented,including the maximum scour depth and scour profile.
文摘Much of the research has focused on identifying bridge frequencies for health monitoring,while the bridge damping ratio also serves as an important factor in damage detection.This study presents an enhanced method for identifying bridge damping ratios using a two-axle,three-mass test vehicle,relying on wheel responses captured by only two mounted sensors.Damping ratio estimation formulas are derived using both the Hilbert Transform(HT)and Wavelet Transform(WT),with a consistent formulation that confirms accurate estimation is achievable with minimal instrumentation,particularly when addressing the support effect.A comparative analysis of the two signal processing techniques reveals the superior performance of WT in identifying bridge damping ratios.The effectiveness of the proposed procedure and formulas is validated through a detailed parametric study,demonstrating robustness across bridges with varying modal damping ratios and different spans using minimal sensors.Moreover,the present study shows that responses from only the first two spans of a multi-span bridge are sufficient for reliable damping estimation,underscoring the practicality and scalability of the procedure for structural health monitoring applications.
基金National Key R&D Program of China(2022YFB2602900)R&D Fund Project of China Academy of Railway Sciences Corporation Limited(2021YJ084)+2 种基金Project of Science and Technology R&D Program of China Railway(2016G002-K)R&D Fund Project of China Railway Major Bridge Reconnaissance&Design Institute Co.,Ltd.(2021)R&D Fund Project of China Railway Shanghai Group(2021141).
文摘Purpose–The bridge expansion joint(BEJ)is a key device for accommodating spatial displacement at the beam end,and for providing vertical support for running trains passing over the gap between the main bridge and the approach bridge.For long-span railway bridges,it must also be coordinated with rail expansion joint(REJ),which is necessary to accommodate the expansion and contraction of,and reducing longitudinal stress in,the rails.The main aim of this study is to present analysis of recent developments in the research and application of BEJs in high-speed railway(HSR)long-span bridges in China,and to propose a performance-based integral design method for BEJs used with REJs,from both theoretical and engineering perspectives.Design/methodology/approach–The study first presents a summary on the application and maintenance of BEJs in HSR long-span bridges in China representing an overview of their state of development.Results of a survey of typical BEJ faults were analyzed,and field testing was conducted on a railway cable-stayed bridge in order to obtain information on the major mechanical characteristics of its BEJ under train load.Based on the above,a performance-based integral design method for BEJs with maximum expansion range 1600 mm(±800 mm),was proposed,covering all stages from overall conceptual design to consideration of detailed structural design issues.The performance of the novel BEJ design thus derived was then verified via theoretical analysis under different scenarios,full-scale model testing,and field testing and commissioning.Findings–Two major types of BEJs,deck-type and through-type,are used in HSR long-span bridges in China.Typical BEJ faults were found to mainly include skewness of steel sleepers at the bridge gap,abnormally large longitudinal frictional resistance,and flexural deformation of the scissor mechanisms.These faults influence BEJ functioning,and thus adversely affect track quality and train running performance at the beam end.Due to their simple and integral structure,deck-type BEJs with expansion range 1200 mm(±600 mm)or less have been favored as a solution offering improved operational conditions,and have emerged as a standard design.However,when the expansion range exceeds the above-mentioned value,special design work becomes necessary.Therefore,based on engineering practice,a performance-based integral design method for BEJs used with REJs was proposed,taking into account four major categories of performance requirements,i.e.,mechanical characteristics,train running quality,durability and insulation performance.Overall BEJ design must mainly consider component strength and the overall stiffness of BEJ;the latter factor in particular has a decisive influence on train running performance at the beam end.Detailed BEJ structural design must stress minimization of the frictional resistance of its sliding surface.The static and dynamic performance of the newlydesigned BEJ with expansion range 1600 mm have been confirmed to be satisfactory,via numerical simulation,full-scale model testing,and field testing and commissioning.Originality/value–This research provides a broad overview of the status of BEJs with large expansion range in HSR long-span bridges in China,along with novel insights into their design.
基金funded by the Science and Technology Development Fund(SKLIOTSC(UM)-2021-2023)the State Key Laboratory of Internet of Things for Smart City(University of Macao)(SKL-IoTSC(UM)-2024-2026/ORP/GA07/2023)Guangdong Provincial Key Laboratory of Modern Civil Engineering Technology(2021B1212040003).
文摘Safety evaluation of a bridge under Moving Abnormal Indivisible Loads(MAILs)directly relates to whether an oversized and/or overweight Large-Cargo Transportation(LCT)vehicle is permitted to pass the bridge.Safety evaluation can be updated by fusing bridge inspection data and load test data,but there are two fundamental difficulties in updating.The first difficulty is to develop an updating scheme to utilize the unstructured inspection data.The second difficulty is to develop a successive updating scheme using load test data based on the previous updating results of the inspection data.This paper proposed a framework,consisting of three modules,to tackle these two fundamental difficulties of updating.Module one is the updating of Finite Element Model(FEM)and resistance of the bridge based on fusing bridge inspection data and load test data.The first difficulty in utilizing the unstructured inspection data is tackled by introducing updating guidelines using the unstructured inspection data.The second difficulty in conducting a successively updating scheme using load test data based on previous updating results is tackled by Bayesian updating.Module two is the simulation of a bridge under a MAIL,updating the ProbabilityDensity Functions(PDFs)of Load Effects(LEs)of critical sections of critical components based on the updated FEM and the givenMAIL.Module three is the safety evaluation of the bridge based on the load-bearing capacity index and reliability index,updating indices based on the updated resistance and LE.Theillustrative examples consist of a simulated example and an engineering example,demonstrating the effectiveness of the proposed framework.The simulated example is the safety evaluation of a bridge under a MAIL,and the engineering example is the safety evaluation of the Anning River Bridge of the Yazhong-Jiangxi Ultra-High-Voltage Direct Current(UHVDC)MAIL project.The results show that it is crucial to fuse bridge inspection data and load test data for updating the safety evaluation of bridges under MAILs.
基金financial support from the Ministry of Education,Culture,Sports,Science and Technology (MEXT),Japan
文摘The effect of seismic directionality is crucial for curved bridges,a subject generally overlooked in seismic vulnerability analysis.This paper focuses on seismic fragility development as a function of seismic incidence directions for a geometrically curved bridge.A series of non-linear time history analyses were carried out for a representative finite element model of the bridge by considering actual ground motions.For reliable seismic demand models,a total of eleven intensity measures(IM)were analyzed based on optimality metrics.To quantify the sensitivity of fragility functions to input incidence directions,fragility surfaces were developed throughout the horizontal plane by considering spectral acceleration at one second(Sa_(1.0))as the optimal IM.Results show that the optimal IM ranking is insignificantly influenced by seismic directionality.However,seismic orientation influences fragility,which intensifies in higher damage states,particularly for piers.For a bridge system,the differences in median demand corresponding to the least and most vulnerable direction for slight,moderate,extensive,and collapse states are about 9.0%,7.31%,10.32%,and 11.60%,respectively.These results imply that while evaluating the vulnerability of curved bridges,the optimality of IM in demand estimation and the impact of seismic directionality should not be disregarded.
文摘From complicated overpasses that defy(违抗)engineering conventions to suspended“river highways”,China is internationally recognized for its innovative infrastructure.Another example of the nation's fearless approach to building and design is the temporary suspension bridge.
基金supported by the Key Research and Development Program of Shaanxi Province-International Science and Technology Cooperation Program Project (No.2020KW-001)the Contract for Xi'an Municipal Science and Technology Plan Project-Xi'an City Strong Foundation Innovation Plan (No.21XJZZ0074)the Key Project of Graduate Student Innovation Fund at Xi'an University of Posts and Telecommunications (No.CXJJZL2023013)。
文摘The detection of surface defects in concrete bridges using deep learning is of significant importance for reducing operational risks,saving maintenance costs,and driving the intelligent transformation of bridge defect detection.In contrast to the subjective and inefficient manual visual inspection,deep learning-based algorithms for concrete defect detection exhibit remarkable advantages,emerging as a focal point in recent research.This paper comprehensively analyzes the research progress of deep learning algorithms in the field of surface defect detection in concrete bridges in recent years.It introduces the early detection methods for surface defects in concrete bridges and the development of deep learning.Subsequently,it provides an overview of deep learning-based concrete bridge surface defect detection research from three aspects:image classification,object detection,and semantic segmentation.The paper summarizes the strengths and weaknesses of existing methods and the challenges they face.Additionally,it analyzes and prospects the development trends of surface defect detection in concrete bridges.
