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.
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 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
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
To address local concrete damage in joint areas at the footing of prefabricated assembled self-centering bridge piers(PASPs)in seismic design,a damage transfer configuration(DTC)was proposed,based on the bridge pier s...To address local concrete damage in joint areas at the footing of prefabricated assembled self-centering bridge piers(PASPs)in seismic design,a damage transfer configuration(DTC)was proposed,based on the bridge pier structure configuration and the mechanism of local damage formation.Integrating the DTC into the PASP,numerical models of a previous experimental reference PASP and a PASP with damage transfer configuration(DTPASP)were established using the finite element software ABAQUS with a concrete damage plasticity(CDP)model.The models were then compared with experimental results regarding damage distribution,hysteresis curves,energy dissipation capacity,the joint opening degree,and residual displacement.The findings indicate that the finite element model developed in this study can well reflect the experimental results of the reference PASP.The incorporation of the DTC proved to be beneficial in preserving structural integrity,bearing capacity,and the functionality of the core structure of bridge piers following an earthquake.Meanwhile,this addition did not exert a significant influence on the seismic behavior of the core structure of the bridge pier.展开更多
Complex bridge structures designed and constructed by humans often necessitate extensive on-site execution,which carries inherent risks.Consequently,a variety of engineering practices are employed to monitor bridge co...Complex bridge structures designed and constructed by humans often necessitate extensive on-site execution,which carries inherent risks.Consequently,a variety of engineering practices are employed to monitor bridge construction.This paper presents a case study of a large-span prestressed concrete(PC)variable-section continuous girder bridge in China,proposing a feedback system for construction monitoring and establishing a finite element(FE)analysis model for the entire bridge.The alignment of the completed bridge adheres to the initial design expectations,with maximum displacement and pre-arch differences from the ideal state measuring 6.39 and 17.7 mm,respectively,which were less than the 20 mm limit required by the specification.Additionally,the stress monitoring showed that the maximum compressive stress was 10.44 MPa,which was 7.5%different from the finite element results,and better predicted the most unfavorable possible location.These results demonstrate that a scientifically rigorous construction monitoring and feedback system can ensure the safety of bridge construction and meet the expected construction standards.The findings presented in this paper provide valuable insights for bridge construction monitoring practices.展开更多
This article discusses the design strategy of complex mountain highway bridges.During the research phase,details were obtained based on prior literature review and analysis of engineering materials from mountainous ar...This article discusses the design strategy of complex mountain highway bridges.During the research phase,details were obtained based on prior literature review and analysis of engineering materials from mountainous area bridges.After analyzing the design characteristics of complex mountainous area road and bridge projects,the principles for the design of bridges on complex mountainous area expressways were proposed.The research on bridge design was carried out from five dimensions:bridge type selection,foundation design,superstructure design,connection part design,and material and technological innovation.Eventually,a relatively complete design system was formed.It is expected that this paper can provide technical references and value for road and bridge projects in China and promote the sustainable development of China’s road traffic system from a macro perspective.展开更多
Railway bridges are continuously loaded by railway trains;therefore, it is important to understand the nonlinear seismic response of the Vehicle-Bridge Interaction (VBI) system under strong earthquakes. For this purpo...Railway bridges are continuously loaded by railway trains;therefore, it is important to understand the nonlinear seismic response of the Vehicle-Bridge Interaction (VBI) system under strong earthquakes. For this purpose, the nonlinear behavior of the pier was introduced into the in-house VBI solvers. The nonlinear the seismic response of the VBI system was comprehensively evaluated using this model, and the effect of the vehicle dynamics on seismic performance of the bridge was identified. It was found that the seismic responses of most simply-supported bridges were reduced in the presence of railway trains due to the out-of-phase motion of the vehicle-bridge system. Meanwhile, the nonlinear behavior of the pier can reduce the vehicle’s seismic responses. Therefore, ignoring the nonlinear behavior of the pier during strong earthquakes can significantly overestimate the seismic response of the vehicle.展开更多
Aerodynamic and dynamic interference from trains is a key issue of concern for the safety of road vehicles travelling on single-level rail-cum road bridges.Based on the wind-road vehicle-train-bridge(WRTB)coupled vibr...Aerodynamic and dynamic interference from trains is a key issue of concern for the safety of road vehicles travelling on single-level rail-cum road bridges.Based on the wind-road vehicle-train-bridge(WRTB)coupled vibration system developed herein,this study examines the dynamic characteristics when road vehicles meet trains in this situation.The influence of load combination,vehicle type and vehicle location is analyzed.A method to obtain the aerodynamic load of road vehicles encountering the train at an arbitrary wind speed is proposed.The results show that due to the windproof facilities and the large line distance between the railway and highway,the aerodynamic and dynamic influence of trains on road vehicles is slight,and the vibration of road vehicles depends on the road roughness.Among the road vehicles discussed,the bus is the easiest to rollover,and the truck-trailer is the easiest to sideslip.Compared with the aerodynamic impact of trains,the crosswind has a more significant influence on road vehicles.The first peak/valley value of aerodynamic loads determines the maximum dynamic response,and the quick method is optimized based on this conclusion.Test cases show that the optimized method can produce conservative results and can be used for relevant research or engineering applications.展开更多
Aerodynamic and dynamic interference between the railway and highway are two major issues that influence travel safety on single-level rail-cum-road bridges.Based on a computational fluid dynamics simulation and vehic...Aerodynamic and dynamic interference between the railway and highway are two major issues that influence travel safety on single-level rail-cum-road bridges.Based on a computational fluid dynamics simulation and vehicle-bridge coupled vibration system,this research explores the dynamic response of a moving van encountering travelling trains on a typical single-level rail-cum-road bridge.The relationship between the line distance of the railway and highway and the dynamic response of the van is discussed.The study reveals that the vertical response of the van is primarily governed by the coupled vibration of the vehicle-bridge system and road roughness,with minimal impact from the line distance.The aerodynamic impact of the train-induced wind significantly influences the lateral,yawing and rolling responses,and the line distance also affects the vehicle’s behavior,with decreasing distance leading to increased response.Among them,the yawing vibration is the most influential.The relationship between the maximum dynamic response and line distance is quantitatively analyzed using the proposed fitting formulas,which perform well on the lateral,rolling and yawing response and shows higher accuracy for acceleration compared to velocity and displacement.Relevant results could provide help on optimizing the arrangement of bridge deck.展开更多
With people living longer,the societal impact of age-related cognitive decline is becoming more pronounced(Crimmins,2015).Thus,it is increasingly important to comprehend the cognitive shifts linked to aging-whether th...With people living longer,the societal impact of age-related cognitive decline is becoming more pronounced(Crimmins,2015).Thus,it is increasingly important to comprehend the cognitive shifts linked to aging-whether they are physiological or pathological.展开更多
This paper studies the deterioration of bridge substructures utilizing the Long-Term Bridge Performance(LTBP)Program InfoBridge^(TM)and develops a survival model using Cox proportional hazards regression.The survival ...This paper studies the deterioration of bridge substructures utilizing the Long-Term Bridge Performance(LTBP)Program InfoBridge^(TM)and develops a survival model using Cox proportional hazards regression.The survival analysis is based on the National Bridge Inventory(NBI)dataset.The study calculates the survival rate of reinforced and prestressed concrete piles on bridges under marine conditions over a 29-year span(from 1992 to 2020).The state of Maryland is the primary focus of this study,with data from three neighboring regions,the District of Columbia,Virginia,and Delaware to expand the sample size.The data obtained from the National Bridge Inventory are condensed and filtered to acquire the most relevant information for model development.The Cox proportional hazards regression is applied to the condensed NBI data with six parameters:Age,ADT,ADTT,number of spans,span length,and structural length.Two survival models are generated for the bridge substructures:Reinforced and prestressed concrete piles in Maryland and reinforced and prestressed concrete piles in wet service conditions in the District of Columbia,Maryland,Delaware,and Virginia.Results from the Cox proportional hazards regression are used to construct Markov chains to demonstrate the sequence of the deterioration of bridge substructures.The Markov chains can be used as a tool to assist in the prediction and decision-making for repair,rehabilitation,and replacement of bridge piles.Based on the numerical model,the Pile Assessment Matrix Program(PAM)is developed to facilitate the assessment and maintenance of current bridge structures.The program integrates the NBI database with the inspection and research reports from various states’department of transportation,to serve as a tool for condition state simulation based on maintenance or rehabilitation strategies.展开更多
The rust layer is a critical factor in determining the corrosion resistance performance of weathering bridge steel.Understanding the evolution mechanism of this rust layer is fundamental for the design and optimizatio...The rust layer is a critical factor in determining the corrosion resistance performance of weathering bridge steel.Understanding the evolution mechanism of this rust layer is fundamental for the design and optimization of such steel.This study investigates the evolu-tion of the rust layer on high-Cr-content weathering bridge steel,using an atmospheric corrosion monitoring(ACM)sensor and big data mining techniques in a simulated tropical marine atmosphere.Results reveal that the protective properties of the rust layer follow a peri-odic pattern of“ascending–constant”rather than a continuous ascending.Correlation analysis indicates that this phenomenon is attributed to the introduction of Cr,which promotes the formation of FeCr_(2)O_(4) in the rust layer.FeCr_(2)O_(4) helps prevent chloride ions from penetrating the rust layer,exerting a protective effect.These findings provide a strong scientific foundation for the design and improvement of new high-Cr-content weathering bridge steels.展开更多
Synergy strategy of photocatalysts and polymer resins are promising technology for marine antifouling.However,it is still a main challenge to obtain a green,safe,and efficient antifouling coatings.Herein,carbon(graphe...Synergy strategy of photocatalysts and polymer resins are promising technology for marine antifouling.However,it is still a main challenge to obtain a green,safe,and efficient antifouling coatings.Herein,carbon(graphene or CNT)modified Ti O_(2)photocatalyst was synthesized via hydrothermal and annealing process and has successfully applied in acrylate fluoroboron polymer(ABFP)composite coating.Morphology and chemical composition were detailed characterized.The graphene or CNT acted as a bridge with supplemental spatial structures(petal gaps,entanglement)and new functional groups(C-O,C-Ti-O,etc.)on Ti O_(2)particle.Carbon nanotube(CNT)modified TiO_(2)-ABFP coatings(BTCP)achieved excellent antibacterial and anti-diatom adhesion rate of 89.3%-96.70%and 99.00%-99.50%,which was 1.84-4.94-fold more than that of the single ABFP.CNT or graphene served as electronic bridges was considered as the crucial mechanism,which significantly improved the light absorption range and capacity,conductivity,and photoelectric response of Ti O_(2),and further accelerated the generation and transfer of free radicals to the surface of BTCP or FTGP.Moreover,the improvement of catalyst activity synergizes with the smooth surface,hydrophilicity,and slow hydrolysis of composite coatings,achieved long-term and efficient antifouling performance.This work provides a new insight into the modification of Ti O_(2)and antifouling mechanism of polymer coating.展开更多
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 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.
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.
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.
基金National Natural Science Foundation of China under Grant Nos.51408359,52278527 and 52478536。
文摘To address local concrete damage in joint areas at the footing of prefabricated assembled self-centering bridge piers(PASPs)in seismic design,a damage transfer configuration(DTC)was proposed,based on the bridge pier structure configuration and the mechanism of local damage formation.Integrating the DTC into the PASP,numerical models of a previous experimental reference PASP and a PASP with damage transfer configuration(DTPASP)were established using the finite element software ABAQUS with a concrete damage plasticity(CDP)model.The models were then compared with experimental results regarding damage distribution,hysteresis curves,energy dissipation capacity,the joint opening degree,and residual displacement.The findings indicate that the finite element model developed in this study can well reflect the experimental results of the reference PASP.The incorporation of the DTC proved to be beneficial in preserving structural integrity,bearing capacity,and the functionality of the core structure of bridge piers following an earthquake.Meanwhile,this addition did not exert a significant influence on the seismic behavior of the core structure of the bridge pier.
基金The Guangdong Basic and Applied Basic Research Foundation(Grant#2023A1515010535).
文摘Complex bridge structures designed and constructed by humans often necessitate extensive on-site execution,which carries inherent risks.Consequently,a variety of engineering practices are employed to monitor bridge construction.This paper presents a case study of a large-span prestressed concrete(PC)variable-section continuous girder bridge in China,proposing a feedback system for construction monitoring and establishing a finite element(FE)analysis model for the entire bridge.The alignment of the completed bridge adheres to the initial design expectations,with maximum displacement and pre-arch differences from the ideal state measuring 6.39 and 17.7 mm,respectively,which were less than the 20 mm limit required by the specification.Additionally,the stress monitoring showed that the maximum compressive stress was 10.44 MPa,which was 7.5%different from the finite element results,and better predicted the most unfavorable possible location.These results demonstrate that a scientifically rigorous construction monitoring and feedback system can ensure the safety of bridge construction and meet the expected construction standards.The findings presented in this paper provide valuable insights for bridge construction monitoring practices.
文摘This article discusses the design strategy of complex mountain highway bridges.During the research phase,details were obtained based on prior literature review and analysis of engineering materials from mountainous area bridges.After analyzing the design characteristics of complex mountainous area road and bridge projects,the principles for the design of bridges on complex mountainous area expressways were proposed.The research on bridge design was carried out from five dimensions:bridge type selection,foundation design,superstructure design,connection part design,and material and technological innovation.Eventually,a relatively complete design system was formed.It is expected that this paper can provide technical references and value for road and bridge projects in China and promote the sustainable development of China’s road traffic system from a macro perspective.
基金supported by the National Natural Science Foundation of China(Grant No.51678490)the Natural Science Foundation of Sichuan Province(Grant No.2024NSFSC0161).
文摘Railway bridges are continuously loaded by railway trains;therefore, it is important to understand the nonlinear seismic response of the Vehicle-Bridge Interaction (VBI) system under strong earthquakes. For this purpose, the nonlinear behavior of the pier was introduced into the in-house VBI solvers. The nonlinear the seismic response of the VBI system was comprehensively evaluated using this model, and the effect of the vehicle dynamics on seismic performance of the bridge was identified. It was found that the seismic responses of most simply-supported bridges were reduced in the presence of railway trains due to the out-of-phase motion of the vehicle-bridge system. Meanwhile, the nonlinear behavior of the pier can reduce the vehicle’s seismic responses. Therefore, ignoring the nonlinear behavior of the pier during strong earthquakes can significantly overestimate the seismic response of the vehicle.
基金The Research Project of Southwest Municipal Design&Research Institute of China under Grant No.2023KY-KT-02-I。
文摘Aerodynamic and dynamic interference from trains is a key issue of concern for the safety of road vehicles travelling on single-level rail-cum road bridges.Based on the wind-road vehicle-train-bridge(WRTB)coupled vibration system developed herein,this study examines the dynamic characteristics when road vehicles meet trains in this situation.The influence of load combination,vehicle type and vehicle location is analyzed.A method to obtain the aerodynamic load of road vehicles encountering the train at an arbitrary wind speed is proposed.The results show that due to the windproof facilities and the large line distance between the railway and highway,the aerodynamic and dynamic influence of trains on road vehicles is slight,and the vibration of road vehicles depends on the road roughness.Among the road vehicles discussed,the bus is the easiest to rollover,and the truck-trailer is the easiest to sideslip.Compared with the aerodynamic impact of trains,the crosswind has a more significant influence on road vehicles.The first peak/valley value of aerodynamic loads determines the maximum dynamic response,and the quick method is optimized based on this conclusion.Test cases show that the optimized method can produce conservative results and can be used for relevant research or engineering applications.
基金Associate Professor Training Project of Nanning University-“Research on the Full-Cycle Rapid Modeling Method of Bridges Based on‘BIM+’Technology”under Grant No.2021JSGC17Guangxi Science and Technology Planning Project:Construction of China ASEAN International Joint Laboratory for Comprehensive Transportation under Grant No.GUIKE AD20297125Basic Ability Promotion Project for Young and Middle-Aged Teachers in Guangxi Universities under Grant No.2019KY0929。
文摘Aerodynamic and dynamic interference between the railway and highway are two major issues that influence travel safety on single-level rail-cum-road bridges.Based on a computational fluid dynamics simulation and vehicle-bridge coupled vibration system,this research explores the dynamic response of a moving van encountering travelling trains on a typical single-level rail-cum-road bridge.The relationship between the line distance of the railway and highway and the dynamic response of the van is discussed.The study reveals that the vertical response of the van is primarily governed by the coupled vibration of the vehicle-bridge system and road roughness,with minimal impact from the line distance.The aerodynamic impact of the train-induced wind significantly influences the lateral,yawing and rolling responses,and the line distance also affects the vehicle’s behavior,with decreasing distance leading to increased response.Among them,the yawing vibration is the most influential.The relationship between the maximum dynamic response and line distance is quantitatively analyzed using the proposed fitting formulas,which perform well on the lateral,rolling and yawing response and shows higher accuracy for acceleration compared to velocity and displacement.Relevant results could provide help on optimizing the arrangement of bridge deck.
基金Clévio Nóbrega’s laboratory is funded by the Cure CSB projectthe Viljem Julijan Association for Children with Rare Diseases(Slovenia)+1 种基金the Algarve Biomedical Center Research Institute(ABC-Ri)funded by CRESC Algarve 2020(Operation Code:ALG-01-0145-FEDER-072586)(to CN)。
文摘With people living longer,the societal impact of age-related cognitive decline is becoming more pronounced(Crimmins,2015).Thus,it is increasingly important to comprehend the cognitive shifts linked to aging-whether they are physiological or pathological.
基金This research receives funding from the Maryland Department of Transportation State Highway Administration.
文摘This paper studies the deterioration of bridge substructures utilizing the Long-Term Bridge Performance(LTBP)Program InfoBridge^(TM)and develops a survival model using Cox proportional hazards regression.The survival analysis is based on the National Bridge Inventory(NBI)dataset.The study calculates the survival rate of reinforced and prestressed concrete piles on bridges under marine conditions over a 29-year span(from 1992 to 2020).The state of Maryland is the primary focus of this study,with data from three neighboring regions,the District of Columbia,Virginia,and Delaware to expand the sample size.The data obtained from the National Bridge Inventory are condensed and filtered to acquire the most relevant information for model development.The Cox proportional hazards regression is applied to the condensed NBI data with six parameters:Age,ADT,ADTT,number of spans,span length,and structural length.Two survival models are generated for the bridge substructures:Reinforced and prestressed concrete piles in Maryland and reinforced and prestressed concrete piles in wet service conditions in the District of Columbia,Maryland,Delaware,and Virginia.Results from the Cox proportional hazards regression are used to construct Markov chains to demonstrate the sequence of the deterioration of bridge substructures.The Markov chains can be used as a tool to assist in the prediction and decision-making for repair,rehabilitation,and replacement of bridge piles.Based on the numerical model,the Pile Assessment Matrix Program(PAM)is developed to facilitate the assessment and maintenance of current bridge structures.The program integrates the NBI database with the inspection and research reports from various states’department of transportation,to serve as a tool for condition state simulation based on maintenance or rehabilitation strategies.
基金supported by the National Natural Science Foundation of China(No.52171063).
文摘The rust layer is a critical factor in determining the corrosion resistance performance of weathering bridge steel.Understanding the evolution mechanism of this rust layer is fundamental for the design and optimization of such steel.This study investigates the evolu-tion of the rust layer on high-Cr-content weathering bridge steel,using an atmospheric corrosion monitoring(ACM)sensor and big data mining techniques in a simulated tropical marine atmosphere.Results reveal that the protective properties of the rust layer follow a peri-odic pattern of“ascending–constant”rather than a continuous ascending.Correlation analysis indicates that this phenomenon is attributed to the introduction of Cr,which promotes the formation of FeCr_(2)O_(4) in the rust layer.FeCr_(2)O_(4) helps prevent chloride ions from penetrating the rust layer,exerting a protective effect.These findings provide a strong scientific foundation for the design and improvement of new high-Cr-content weathering bridge steels.
基金supported by the National Natural Science Foundation of China(Nos.42277315,22066009)the Scientific Research Startup Fund of Hainan University(Nos.XJ2300005916,kyqd(zr)22185)+1 种基金supported by Scientific Research Project of Hainan Higher Education Institutions(No.Hnky2023-9)Innovational Fund for Scientific and Technological Personnel of Hainan Province(No.KJRC2023C12)。
文摘Synergy strategy of photocatalysts and polymer resins are promising technology for marine antifouling.However,it is still a main challenge to obtain a green,safe,and efficient antifouling coatings.Herein,carbon(graphene or CNT)modified Ti O_(2)photocatalyst was synthesized via hydrothermal and annealing process and has successfully applied in acrylate fluoroboron polymer(ABFP)composite coating.Morphology and chemical composition were detailed characterized.The graphene or CNT acted as a bridge with supplemental spatial structures(petal gaps,entanglement)and new functional groups(C-O,C-Ti-O,etc.)on Ti O_(2)particle.Carbon nanotube(CNT)modified TiO_(2)-ABFP coatings(BTCP)achieved excellent antibacterial and anti-diatom adhesion rate of 89.3%-96.70%and 99.00%-99.50%,which was 1.84-4.94-fold more than that of the single ABFP.CNT or graphene served as electronic bridges was considered as the crucial mechanism,which significantly improved the light absorption range and capacity,conductivity,and photoelectric response of Ti O_(2),and further accelerated the generation and transfer of free radicals to the surface of BTCP or FTGP.Moreover,the improvement of catalyst activity synergizes with the smooth surface,hydrophilicity,and slow hydrolysis of composite coatings,achieved long-term and efficient antifouling performance.This work provides a new insight into the modification of Ti O_(2)and antifouling mechanism of polymer coating.
