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
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
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
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
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
The fiber optic sensing technology provides data support in structural health monitoring of the macro facilities,including design,construction,and maintenance of bridges,tunnels,ports and other infrastructures.In this...The fiber optic sensing technology provides data support in structural health monitoring of the macro facilities,including design,construction,and maintenance of bridges,tunnels,ports and other infrastructures.In this paper,a distributed vibration sensing system is proved to be responsive to a single touch over a 1.8-m-long equivalent fiber segment,covering a vibration frequency from 5 Hz to 25 kHz.The sensing fiber was arranged as an S type layout on the bridge to recognize the standing state,windblown disturbance,and walking vibration.Moreover,the knocking and climbing events are recognized fiber laying spinning lines and hanging on the fences,respectively.The demonstration shows an accurate positioning and sensitive vibration monitoring applied on the automated three-dimensional(3D) printed bridge,which is applicable to all kinds of 3D printed facilities as intelligent sensory neuro-networks.展开更多
Main cable displacement-controlled devices(DCDs)are key components for coordinating the vertical deformation of the main cable and main girder in the side span of continuous suspension bridges.To reveal the mechanical...Main cable displacement-controlled devices(DCDs)are key components for coordinating the vertical deformation of the main cable and main girder in the side span of continuous suspension bridges.To reveal the mechanical action mechanisms of DCD on bridge structures,a three-span continuous suspension bridge was taken as the engineering background in this study.The influence of different forms of DCD on the internal force and displacement of the components in the side span of the bridge and the structural dynamic characteristics were explored through numerical simulations.The results showed that the lack of DCD caused the main cable and main girder to have large vertical displacements.The stresses of other components were redistributed,and the safety factor of the suspenders at the side span was greatly reduced.The setting of DCD improved the vertical stiffness of the structure.The rigid DCD had larger internal forces,but its control effect on the internal forces at the side span was slightly better than that of the flexible DCD.Both forms of DCD effectively coordinated the deformation of the main cable and main girder and the stress distribution of components in the side span area.The choice of DCD form depends on the topographic factors of bridge sites and the design requirements of related components at the side span.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
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
When a coin is tossed to a gravity well,it will spiral instead of falling directly to the center.Inspired by this phenomenon,a gravity well-inspired double friction pendulum system(GW-DFPS)is developed to extend the l...When a coin is tossed to a gravity well,it will spiral instead of falling directly to the center.Inspired by this phenomenon,a gravity well-inspired double friction pendulum system(GW-DFPS)is developed to extend the length of sliding trajectories of bridge superstructures during pulse-like near-fault earthquakes.As a result,a greater amount of energy will be dissipated due to the frictional sliding of the isolators.The GW-DFPS consists of a spherical surface and an outer surface described by a 1/x or logarithmic function to build gravity well.Full-scale isolators were fabricated and their response was characterized considering various parameters such as the friction material of slider,surface roughness of sliding surfaces,and applied vertical loads.Additionally,a finite element model of the isolator was created using the experimental test data.Numerical simulations were performed on a case-study bridge structure isolated using both a conventional DFPS system and the proposed GW-DFPS systems.The experimental results reveal that the proposed isolators exhibit stable response under vertical loads varying from 200 kN to 1000 kN with a negative stiffness response when the isolator slides at the outer sliding surface.The numerical simulations of the selected bridge structure demonstrate that the GW-DFPS significantly extends the sliding trajectory lengths of the superstructure during half of the earthquake pulses,resulting in increased energy dissipation during this interval.The kinetic energies of the bridge isolated by GW-DFPS are consistently lower than those of the bridge isolated by the other two kinds of isolators,resulting lower shear forces on the bridge.展开更多
Aiming at the problems of difficulty in balancing construction efficiency and quality,as well as the high safety risks of working at heights during the construction of main piers for highway bridges,this study takes a...Aiming at the problems of difficulty in balancing construction efficiency and quality,as well as the high safety risks of working at heights during the construction of main piers for highway bridges,this study takes a specific bridge project as an example to introduce the technology of hydraulically sliding formwork for the construction of main piers of highway bridges.An in-depth analysis of the project’s construction process found that this technology can effectively improve construction efficiency,ensure the quality of concrete pouring,and significantly reduce the potential safety hazards of working at heights.It provides a reliable technical solution for constructing the main piers of highway bridges and has important reference significance for similar projects.展开更多
High-speed railway bridges are essential components of any railway transportation system that should keep adequate levels of serviceability and safety.In this context,drive-by methodologies have emerged as a feasible ...High-speed railway bridges are essential components of any railway transportation system that should keep adequate levels of serviceability and safety.In this context,drive-by methodologies have emerged as a feasible and cost-effective monitor-ing solution for detecting damage on railway bridges while minimizing train operation interruptions.Moreover,integrating advanced sensor technologies and machine learning algorithms has significantly enhanced structural health monitoring(SHM)for bridges.Despite being increasingly used in traditional SHM applications,studies using autoencoders within drive-by methodologies are rare,especially in the railway field.This study presents a novel approach for drive-by damage detection in HSR bridges.The methodology relies on acceleration records collected from multiple bridge crossings by an operational train equipped with onboard sensors.Log-Mel spectrogram features derived from the acceleration records are used together with sparse autoencoders for computing statistical distribution-based damage indexes.Numerical simulations were performed on a 3D vehicle-track-bridge interaction system model implemented in Matlab to evaluate the robustness and effectiveness of the proposed approach,considering several damage scenarios,vehicle speeds,and environmental and operational variations,such as multiple track irregularities and varying measurement noise.The results show that the pro-posed approach can successfully detect damages,as well as characterize their severity,especially for very early-stage dam-ages.This demonstrates the high potential of applying Mel-frequency damage-sensitive features associated with machine learning algorithms in the drive-by condition assessment of high-speed railway bridges.展开更多
As an evaluation index,the natural frequency has the advantages of easy acquisition and quantitative evaluation.In this paper,the natural frequency is used to evaluate the performance of external cable reinforced brid...As an evaluation index,the natural frequency has the advantages of easy acquisition and quantitative evaluation.In this paper,the natural frequency is used to evaluate the performance of external cable reinforced bridges.Numerical examples show that compared with the natural frequencies of first-order modes,the natural frequencies of higher-order modes are more sensitive and can reflect the damage situation and external cable reinforcement effect of T-beam bridges.For damaged bridges,as the damage to the T-beam increases,the natural frequency value of the bridge gradually decreases.When the degree of local damage to the beam reaches 60%,the amplitude of natural frequency change exceeds 10%for the first time.The natural frequencies of the firstorder vibration mode and higher-order vibration mode can be selected as indexes for different degrees of the damaged T-beam bridges.For damaged bridges reinforced with external cables,the traditional natural frequency of the first-order vibration mode cannot be used as the index,which is insensitive to changes in prestress of the external cable.Some natural frequencies of higher-order vibration modes can be selected as indexes,which can reflect the reinforcement effect of externally prestressed damaged T-beam bridges,and its numerical value increases with the increase of external prestressed cable force.展开更多
To improve the accuracy of thermal response estimation and overcome the limitations of the linear regression model and Artificial Neural Network(ANN)model,this study introduces a deep learning estimation method specif...To improve the accuracy of thermal response estimation and overcome the limitations of the linear regression model and Artificial Neural Network(ANN)model,this study introduces a deep learning estimation method specifically based on the Long Short-Term Memory(LSTM)network,to predict temperature-induced girder end displacements of the Dasha Waterway Bridge,a suspension bridge in China.First,to enhance data quality and select target sensors,preprocessing based on the sigma rule and nearest neighbor interpolation is applied to the raw data.Furthermore,to eliminate the high-frequency components from the displacement signal,the wavelet transform is conducted.Subsequently,the linear regression model and ANN model are established,whose results do not meet the requirements and fail to address the time lag effect between temperature and displacements.The study proceeds to develop the LSTM network model and determine the optimal parameters through hyperparameter sensitivity analysis.Finally,the results of the LSTM network model are discussed by a comparative analysis against the linear regression model and ANN model,which indicates a higher accuracy in predicting temperatureinduced girder end displacements and the ability to mitigate the time-lag effect.To be more specific,in comparison between the linear regression model and LSTM network,the mean square error decreases from 6.5937 to 1.6808 and R^(2) increases from 0.683 to 0.930,which corresponds to a 74.51%decrease in MSE and a 36.14%improvement in R^(2).Compared to ANN,with an MSE of 4.6371 and an R^(2) of 0.807,LSTM shows a decrease in MSE of 63.75%and an increase in R^(2) of 13.23%,demonstrating a significant enhancement in predictive performance.展开更多
Based on the Etihad Railway Station Project,this study selects a single-span frame bridge with a clear span of 7.3 meters as the research object.A comprehensive structural design process was conducted following the AR...Based on the Etihad Railway Station Project,this study selects a single-span frame bridge with a clear span of 7.3 meters as the research object.A comprehensive structural design process was conducted following the AREMA(2023),Manual for Railway Engineering-Volume 2-Structures,with systematic comparisons of techno-economic differences between the Chinese and American codes through recalculation verification and equivalent-precision design methods.The findings reveal:Recalculation using the Chinese code for identical structural dimensions and reinforcement layouts demonstrates that AREMA code exhibits greater conservatism in both strength requirements and crack control;Under equivalent precision design principles,the Chinese code solution reduces reinforcement by 4.128 t tons and a 19.5%reduction in reinforcement at critical sections compared to the AREMA code,indicating slightly reduced economic efficiency of the AREMA code.This research provides quantitative references for standardized design and specification integration in cross-border railway engineering projects.展开更多
A realistic and economical dynamic assessment of railway bridges requires input parameters that correspond to reality.In this context,the applied damping properties of the structure have a decisive influence on the re...A realistic and economical dynamic assessment of railway bridges requires input parameters that correspond to reality.In this context,the applied damping properties of the structure have a decisive influence on the results in the prediction of resonance effects and further in the assessment of the compatibility between rolling stock and railway bridges.The standard prescribes damping factors depending on the type of structure and the span to be used in dynamic calculations.However,these factors can be regarded as very conservative values which do not represent reality.Thus,in situ measurements on the structure are often necessary to classify a bridge categorised as critical in prior dynamic calculations as non-critical.Regarding in situ tests,a measurement-based determination of the damping factor is inevitably accompanied by a scattering of the generated results due to the measurement method used and as a result of the individual scope of action of the test-evaluating person and this person’s interpretation of the measurement data.This paper presents novel evaluation methods and analysis tools for determining the damping factor based on measurements in the frequency and time domains,intending to reduce the scatter of the results and limit the scope of action of the person evaluating the test.The main aim is to provide simple and easy-to-use evaluation algorithms for practical applications without additional data transformations and to define clear principles of action for the data-based evaluation of realistic and high damping factors.Based on in situ tests on 15 existing railway bridges,the data-based procedure for determining the damping factor is explained,and the methods are compared in the time and frequency domains.It is shown that a clearly defined evaluation algorithm can significantly reduce the scattering of results.Furthermore,it is demonstrated that forced vibration excitation and evaluation in the frequency domain provide the best results in reliable,reproducible,and high damping factors.展开更多
The huge carrier transfer resistance caused by large-sized"nitrogen pot"severely limits the photocatalytic performance of carbon nitride(CN).This study aims to explore the selection principle of metal ion br...The huge carrier transfer resistance caused by large-sized"nitrogen pot"severely limits the photocatalytic performance of carbon nitride(CN).This study aims to explore the selection principle of metal ion bridges for constructing dual carrier-transfer channels to delivery carriers to respectively active sites using photodegradation of phenol as the model reaction.Density functional theory(DFT)calculation was used to optimize the structure model of nitrogen vacancies(Nv,provide active sites for reduction of O_(2) and oxidation of phenol)and metal ions(Fe^(3+),Co^(2+),Ni^(2+)or Cu^(2+))co-modified CN,and screen metal ion bridges based on the three parameters including bonding state of metal ion and"nitrogen pot",electrostatic potential(ESP)distribution around the active sites,and three-electron bond length.Both calculation results and activity data show that Fe^(3+),Co^(2+)and Ni^(2+)can construct dual carrier-transfer channels to promote the degradation of phenol while Cu^(2+)cannot Ny and Fe^(3+)co-modified CN(Fe/N_(v)-CN)showed the best catalytic performance among various catalysts and was used as the model catalyst for the detailed characterization to verify the calculation results.This work provides not only the novel strategy for constructing dual carrier-transfer channels in CN,but also the crucial basis for computer simulation as a prediction tool of catalyst structure design rationality.展开更多
BACKGROUND Spinal cord injury(SCI)imposes enduring physical impairments and substantial socio-economic burdens.These injuries are either traumatic incidents or ischemic but exhibit comparable clinical recoveries.This ...BACKGROUND Spinal cord injury(SCI)imposes enduring physical impairments and substantial socio-economic burdens.These injuries are either traumatic incidents or ischemic but exhibit comparable clinical recoveries.This suggests shared underlying neurodegenerative mechanisms,such as neuronal cell death,demyelination,and axonal degeneration,regardless of aetiology.AIM To investigate the relationship between the magnetic resonance imaging(MRI)biomarkers(tissue bridges)and clinical outcome in acute traumatic SCI.METHODS In this prospective study adult patients with acute SCI who were examined clinically and radiologically within first 48 hours and subsequently at intervals were included.Clinical assessment included sensory score,motor score and zone of partial preservation.Radiological scores included measurement kyphotic deformities-sagittal index,regional kyphosis,gardener segmental kyphotic deformity.MRI on 3 Tesla machine was done to evaluate quantitative&qualitative parameters,and tissue bridges at one and 6 months.RESULTS There were 47 patients with a mean age of 40.43±10.73 years and male/female ratio of 34:13.There was a significant(P<0.05)improvement in clinical,radiological,and MRI parameters at 6 months.Maximum spinal cord compression(MSCC),maximal canal compression,lesion length,width,and area;dorsal tissue bridges;ventral tissue bridges,total width of tissue bridges;and midsagittal tissue bridge ratios at one month significantly(P<0.05)correlated with the 6-month total motor score and total sensory score.Further,the regression analysis demonstrated clinical improvement to dimensions of tissue bridges at 6 months.CONCLUSION The MRI imaging biomarkers in SCI patients demonstrated substantial improvement over time.There was a negative correlation between neurological recovery,MSCC,maximum canal compromise,and lesion dimensions(lesion length,lesion width,and lesion area).Higher canal compromise and lesion dimensions were associated with a poorer outcome.The evaluation of the midsagittal tissue bridge(including the ventral tissue bridge,dorsal tissue bridge,total width of the tissue bridge,and tissue bridge ratios)at 1 and 6 months showed a positive correlation with the neurological recovery.展开更多
To investigate the influence of different longitudinal constraint systems on the longitudinal displacement at the girder ends of a three-tower suspension bridge,this study takes the Cangrong Xunjiang Bridge as an engi...To investigate the influence of different longitudinal constraint systems on the longitudinal displacement at the girder ends of a three-tower suspension bridge,this study takes the Cangrong Xunjiang Bridge as an engineering case for finite element analysis.This bridge employs an unprecedented tower-girder constraintmethod,with all vertical supports placed at the transition piers at both ends.This paper aims to study the characteristics of longitudinal displacement control at the girder ends under this novel structure,relying on finite element(FE)analysis.Initially,based on the Weigh In Motion(WIM)data,a random vehicle load model is generated and applied to the finite elementmodel.Several longitudinal constraint systems are proposed,and their effects on the structural response of the bridge are compared.The most reasonable system,balancing girder-end displacement and transitional pier stress,is selected.Subsequently,the study examines the impact of different viscous damper parameters on key structural response indicators,including cumulative longitudinal displacement at the girder ends,maximum longitudinal displacement at the girder ends,cumulative longitudinal displacement at the pier tops,maximum longitudinal displacement at the pier tops,longitudinal acceleration at the pier tops,and maximum bending moment at the pier bottoms.Finally,the coefficient of variation(CV)-TOPSIS method is used to optimize the viscous damper parameters for multiple objectives.The results show that adding viscous dampers at the side towers,in addition to the existing longitudinal limit bearings at the central tower,can most effectively reduce the response of structural indicators.The changes in these indicators are not entirely consistent with variations in damping coefficient and velocity exponent.The damper parameters significantly influence cumulative longitudinal displacement at the girder ends,cumulative longitudinal displacement at the pier tops,and maximum bending moments at the pier bottoms.The optimal damper parameters are found to be a damping coefficient of 5000 kN/(m/s)0.2 and a velocity exponent of 0.2.展开更多
In 2015,the Lancang-Mekong Cooperation(LMC)mechanism was inaugurated in Kunming,Yunnan Province.A decade later,the 10th Lancang-Mekong Cooperation Foreign Ministers’Meeting was held in Anning,Yunnan,following the ri...In 2015,the Lancang-Mekong Cooperation(LMC)mechanism was inaugurated in Kunming,Yunnan Province.A decade later,the 10th Lancang-Mekong Cooperation Foreign Ministers’Meeting was held in Anning,Yunnan,following the river’s course back to where the cooperation journey began.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supported by the National Natural Science Foundation of China (No.6210031560)the Natural Science Foundation of Hebei Province (No.A2020202013)the Natural Science Foundation of Tianjin City (No.21JCQNJC00780)。
文摘The fiber optic sensing technology provides data support in structural health monitoring of the macro facilities,including design,construction,and maintenance of bridges,tunnels,ports and other infrastructures.In this paper,a distributed vibration sensing system is proved to be responsive to a single touch over a 1.8-m-long equivalent fiber segment,covering a vibration frequency from 5 Hz to 25 kHz.The sensing fiber was arranged as an S type layout on the bridge to recognize the standing state,windblown disturbance,and walking vibration.Moreover,the knocking and climbing events are recognized fiber laying spinning lines and hanging on the fences,respectively.The demonstration shows an accurate positioning and sensitive vibration monitoring applied on the automated three-dimensional(3D) printed bridge,which is applicable to all kinds of 3D printed facilities as intelligent sensory neuro-networks.
基金The National Natural Science Foundation of China(No.52338011)the Postgraduate Research&Practice Innovation Program of Jiangsu Province(No.SJCX23_0067).
文摘Main cable displacement-controlled devices(DCDs)are key components for coordinating the vertical deformation of the main cable and main girder in the side span of continuous suspension bridges.To reveal the mechanical action mechanisms of DCD on bridge structures,a three-span continuous suspension bridge was taken as the engineering background in this study.The influence of different forms of DCD on the internal force and displacement of the components in the side span of the bridge and the structural dynamic characteristics were explored through numerical simulations.The results showed that the lack of DCD caused the main cable and main girder to have large vertical displacements.The stresses of other components were redistributed,and the safety factor of the suspenders at the side span was greatly reduced.The setting of DCD improved the vertical stiffness of the structure.The rigid DCD had larger internal forces,but its control effect on the internal forces at the side span was slightly better than that of the flexible DCD.Both forms of DCD effectively coordinated the deformation of the main cable and main girder and the stress distribution of components in the side span area.The choice of DCD form depends on the topographic factors of bridge sites and the design requirements of related components at the side span.
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.
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.
基金financially supported by the National Natural Science Foundation of China(Grants 52178124,52478151).
文摘When a coin is tossed to a gravity well,it will spiral instead of falling directly to the center.Inspired by this phenomenon,a gravity well-inspired double friction pendulum system(GW-DFPS)is developed to extend the length of sliding trajectories of bridge superstructures during pulse-like near-fault earthquakes.As a result,a greater amount of energy will be dissipated due to the frictional sliding of the isolators.The GW-DFPS consists of a spherical surface and an outer surface described by a 1/x or logarithmic function to build gravity well.Full-scale isolators were fabricated and their response was characterized considering various parameters such as the friction material of slider,surface roughness of sliding surfaces,and applied vertical loads.Additionally,a finite element model of the isolator was created using the experimental test data.Numerical simulations were performed on a case-study bridge structure isolated using both a conventional DFPS system and the proposed GW-DFPS systems.The experimental results reveal that the proposed isolators exhibit stable response under vertical loads varying from 200 kN to 1000 kN with a negative stiffness response when the isolator slides at the outer sliding surface.The numerical simulations of the selected bridge structure demonstrate that the GW-DFPS significantly extends the sliding trajectory lengths of the superstructure during half of the earthquake pulses,resulting in increased energy dissipation during this interval.The kinetic energies of the bridge isolated by GW-DFPS are consistently lower than those of the bridge isolated by the other two kinds of isolators,resulting lower shear forces on the bridge.
文摘Aiming at the problems of difficulty in balancing construction efficiency and quality,as well as the high safety risks of working at heights during the construction of main piers for highway bridges,this study takes a specific bridge project as an example to introduce the technology of hydraulically sliding formwork for the construction of main piers of highway bridges.An in-depth analysis of the project’s construction process found that this technology can effectively improve construction efficiency,ensure the quality of concrete pouring,and significantly reduce the potential safety hazards of working at heights.It provides a reliable technical solution for constructing the main piers of highway bridges and has important reference significance for similar projects.
基金support of CNPq(Brazilian Ministry of Science and Technology Agency),of CAPES(Higher Education Improvement Agency),of FAPESP(São Paulo Research Foundation)under grant#2022/13045-1,of VALE Catedra Under Rail and of Base Funding-UIDB/04708/2020Programmatic Funding-UIDP/04708/2020 of the CONSTRUCT-“Instituto de I&D em Estruturas e Construções”.
文摘High-speed railway bridges are essential components of any railway transportation system that should keep adequate levels of serviceability and safety.In this context,drive-by methodologies have emerged as a feasible and cost-effective monitor-ing solution for detecting damage on railway bridges while minimizing train operation interruptions.Moreover,integrating advanced sensor technologies and machine learning algorithms has significantly enhanced structural health monitoring(SHM)for bridges.Despite being increasingly used in traditional SHM applications,studies using autoencoders within drive-by methodologies are rare,especially in the railway field.This study presents a novel approach for drive-by damage detection in HSR bridges.The methodology relies on acceleration records collected from multiple bridge crossings by an operational train equipped with onboard sensors.Log-Mel spectrogram features derived from the acceleration records are used together with sparse autoencoders for computing statistical distribution-based damage indexes.Numerical simulations were performed on a 3D vehicle-track-bridge interaction system model implemented in Matlab to evaluate the robustness and effectiveness of the proposed approach,considering several damage scenarios,vehicle speeds,and environmental and operational variations,such as multiple track irregularities and varying measurement noise.The results show that the pro-posed approach can successfully detect damages,as well as characterize their severity,especially for very early-stage dam-ages.This demonstrates the high potential of applying Mel-frequency damage-sensitive features associated with machine learning algorithms in the drive-by condition assessment of high-speed railway bridges.
基金supported by Henan Province Science and Technology Research Funding Project(No.222102320129)the Key Research Project of Henan Higher Education Institutions(Grant Nos.22A560004,22A56005).
文摘As an evaluation index,the natural frequency has the advantages of easy acquisition and quantitative evaluation.In this paper,the natural frequency is used to evaluate the performance of external cable reinforced bridges.Numerical examples show that compared with the natural frequencies of first-order modes,the natural frequencies of higher-order modes are more sensitive and can reflect the damage situation and external cable reinforcement effect of T-beam bridges.For damaged bridges,as the damage to the T-beam increases,the natural frequency value of the bridge gradually decreases.When the degree of local damage to the beam reaches 60%,the amplitude of natural frequency change exceeds 10%for the first time.The natural frequencies of the firstorder vibration mode and higher-order vibration mode can be selected as indexes for different degrees of the damaged T-beam bridges.For damaged bridges reinforced with external cables,the traditional natural frequency of the first-order vibration mode cannot be used as the index,which is insensitive to changes in prestress of the external cable.Some natural frequencies of higher-order vibration modes can be selected as indexes,which can reflect the reinforcement effect of externally prestressed damaged T-beam bridges,and its numerical value increases with the increase of external prestressed cable force.
基金The National Key Research and Development Program of China grant No.2022YFB3706704 received by Yuan Renthe National Natural and Science Foundation of China grant No.52308150 received by Xiang Xu.
文摘To improve the accuracy of thermal response estimation and overcome the limitations of the linear regression model and Artificial Neural Network(ANN)model,this study introduces a deep learning estimation method specifically based on the Long Short-Term Memory(LSTM)network,to predict temperature-induced girder end displacements of the Dasha Waterway Bridge,a suspension bridge in China.First,to enhance data quality and select target sensors,preprocessing based on the sigma rule and nearest neighbor interpolation is applied to the raw data.Furthermore,to eliminate the high-frequency components from the displacement signal,the wavelet transform is conducted.Subsequently,the linear regression model and ANN model are established,whose results do not meet the requirements and fail to address the time lag effect between temperature and displacements.The study proceeds to develop the LSTM network model and determine the optimal parameters through hyperparameter sensitivity analysis.Finally,the results of the LSTM network model are discussed by a comparative analysis against the linear regression model and ANN model,which indicates a higher accuracy in predicting temperatureinduced girder end displacements and the ability to mitigate the time-lag effect.To be more specific,in comparison between the linear regression model and LSTM network,the mean square error decreases from 6.5937 to 1.6808 and R^(2) increases from 0.683 to 0.930,which corresponds to a 74.51%decrease in MSE and a 36.14%improvement in R^(2).Compared to ANN,with an MSE of 4.6371 and an R^(2) of 0.807,LSTM shows a decrease in MSE of 63.75%and an increase in R^(2) of 13.23%,demonstrating a significant enhancement in predictive performance.
文摘Based on the Etihad Railway Station Project,this study selects a single-span frame bridge with a clear span of 7.3 meters as the research object.A comprehensive structural design process was conducted following the AREMA(2023),Manual for Railway Engineering-Volume 2-Structures,with systematic comparisons of techno-economic differences between the Chinese and American codes through recalculation verification and equivalent-precision design methods.The findings reveal:Recalculation using the Chinese code for identical structural dimensions and reinforcement layouts demonstrates that AREMA code exhibits greater conservatism in both strength requirements and crack control;Under equivalent precision design principles,the Chinese code solution reduces reinforcement by 4.128 t tons and a 19.5%reduction in reinforcement at critical sections compared to the AREMA code,indicating slightly reduced economic efficiency of the AREMA code.This research provides quantitative references for standardized design and specification integration in cross-border railway engineering projects.
基金funded by the Austrian Federal Railways (ÖBB Infrastruktur AG) in the context of the research project ‘Ve Mo Diss’ (acronym)
文摘A realistic and economical dynamic assessment of railway bridges requires input parameters that correspond to reality.In this context,the applied damping properties of the structure have a decisive influence on the results in the prediction of resonance effects and further in the assessment of the compatibility between rolling stock and railway bridges.The standard prescribes damping factors depending on the type of structure and the span to be used in dynamic calculations.However,these factors can be regarded as very conservative values which do not represent reality.Thus,in situ measurements on the structure are often necessary to classify a bridge categorised as critical in prior dynamic calculations as non-critical.Regarding in situ tests,a measurement-based determination of the damping factor is inevitably accompanied by a scattering of the generated results due to the measurement method used and as a result of the individual scope of action of the test-evaluating person and this person’s interpretation of the measurement data.This paper presents novel evaluation methods and analysis tools for determining the damping factor based on measurements in the frequency and time domains,intending to reduce the scatter of the results and limit the scope of action of the person evaluating the test.The main aim is to provide simple and easy-to-use evaluation algorithms for practical applications without additional data transformations and to define clear principles of action for the data-based evaluation of realistic and high damping factors.Based on in situ tests on 15 existing railway bridges,the data-based procedure for determining the damping factor is explained,and the methods are compared in the time and frequency domains.It is shown that a clearly defined evaluation algorithm can significantly reduce the scattering of results.Furthermore,it is demonstrated that forced vibration excitation and evaluation in the frequency domain provide the best results in reliable,reproducible,and high damping factors.
基金supported by the National Natural Science Foundation of China(82301052)China Postdoctoral Science Foundation(2023M732151)+3 种基金Shanxi Provincial Science and Technology Department(202303021212131)Health Commission of Shanxi Province(2022XM14)Shanxi Provincial Education Department(2022L165)Shanxi Medical University(XD2232)。
文摘The huge carrier transfer resistance caused by large-sized"nitrogen pot"severely limits the photocatalytic performance of carbon nitride(CN).This study aims to explore the selection principle of metal ion bridges for constructing dual carrier-transfer channels to delivery carriers to respectively active sites using photodegradation of phenol as the model reaction.Density functional theory(DFT)calculation was used to optimize the structure model of nitrogen vacancies(Nv,provide active sites for reduction of O_(2) and oxidation of phenol)and metal ions(Fe^(3+),Co^(2+),Ni^(2+)or Cu^(2+))co-modified CN,and screen metal ion bridges based on the three parameters including bonding state of metal ion and"nitrogen pot",electrostatic potential(ESP)distribution around the active sites,and three-electron bond length.Both calculation results and activity data show that Fe^(3+),Co^(2+)and Ni^(2+)can construct dual carrier-transfer channels to promote the degradation of phenol while Cu^(2+)cannot Ny and Fe^(3+)co-modified CN(Fe/N_(v)-CN)showed the best catalytic performance among various catalysts and was used as the model catalyst for the detailed characterization to verify the calculation results.This work provides not only the novel strategy for constructing dual carrier-transfer channels in CN,but also the crucial basis for computer simulation as a prediction tool of catalyst structure design rationality.
文摘BACKGROUND Spinal cord injury(SCI)imposes enduring physical impairments and substantial socio-economic burdens.These injuries are either traumatic incidents or ischemic but exhibit comparable clinical recoveries.This suggests shared underlying neurodegenerative mechanisms,such as neuronal cell death,demyelination,and axonal degeneration,regardless of aetiology.AIM To investigate the relationship between the magnetic resonance imaging(MRI)biomarkers(tissue bridges)and clinical outcome in acute traumatic SCI.METHODS In this prospective study adult patients with acute SCI who were examined clinically and radiologically within first 48 hours and subsequently at intervals were included.Clinical assessment included sensory score,motor score and zone of partial preservation.Radiological scores included measurement kyphotic deformities-sagittal index,regional kyphosis,gardener segmental kyphotic deformity.MRI on 3 Tesla machine was done to evaluate quantitative&qualitative parameters,and tissue bridges at one and 6 months.RESULTS There were 47 patients with a mean age of 40.43±10.73 years and male/female ratio of 34:13.There was a significant(P<0.05)improvement in clinical,radiological,and MRI parameters at 6 months.Maximum spinal cord compression(MSCC),maximal canal compression,lesion length,width,and area;dorsal tissue bridges;ventral tissue bridges,total width of tissue bridges;and midsagittal tissue bridge ratios at one month significantly(P<0.05)correlated with the 6-month total motor score and total sensory score.Further,the regression analysis demonstrated clinical improvement to dimensions of tissue bridges at 6 months.CONCLUSION The MRI imaging biomarkers in SCI patients demonstrated substantial improvement over time.There was a negative correlation between neurological recovery,MSCC,maximum canal compromise,and lesion dimensions(lesion length,lesion width,and lesion area).Higher canal compromise and lesion dimensions were associated with a poorer outcome.The evaluation of the midsagittal tissue bridge(including the ventral tissue bridge,dorsal tissue bridge,total width of the tissue bridge,and tissue bridge ratios)at 1 and 6 months showed a positive correlation with the neurological recovery.
基金supported by the National Key Research and Development Program of China(No.2022YFB3706704)the Academician Special Science Research Project of CCCC(No.YSZX-03-2022-01-B).
文摘To investigate the influence of different longitudinal constraint systems on the longitudinal displacement at the girder ends of a three-tower suspension bridge,this study takes the Cangrong Xunjiang Bridge as an engineering case for finite element analysis.This bridge employs an unprecedented tower-girder constraintmethod,with all vertical supports placed at the transition piers at both ends.This paper aims to study the characteristics of longitudinal displacement control at the girder ends under this novel structure,relying on finite element(FE)analysis.Initially,based on the Weigh In Motion(WIM)data,a random vehicle load model is generated and applied to the finite elementmodel.Several longitudinal constraint systems are proposed,and their effects on the structural response of the bridge are compared.The most reasonable system,balancing girder-end displacement and transitional pier stress,is selected.Subsequently,the study examines the impact of different viscous damper parameters on key structural response indicators,including cumulative longitudinal displacement at the girder ends,maximum longitudinal displacement at the girder ends,cumulative longitudinal displacement at the pier tops,maximum longitudinal displacement at the pier tops,longitudinal acceleration at the pier tops,and maximum bending moment at the pier bottoms.Finally,the coefficient of variation(CV)-TOPSIS method is used to optimize the viscous damper parameters for multiple objectives.The results show that adding viscous dampers at the side towers,in addition to the existing longitudinal limit bearings at the central tower,can most effectively reduce the response of structural indicators.The changes in these indicators are not entirely consistent with variations in damping coefficient and velocity exponent.The damper parameters significantly influence cumulative longitudinal displacement at the girder ends,cumulative longitudinal displacement at the pier tops,and maximum bending moments at the pier bottoms.The optimal damper parameters are found to be a damping coefficient of 5000 kN/(m/s)0.2 and a velocity exponent of 0.2.
文摘In 2015,the Lancang-Mekong Cooperation(LMC)mechanism was inaugurated in Kunming,Yunnan Province.A decade later,the 10th Lancang-Mekong Cooperation Foreign Ministers’Meeting was held in Anning,Yunnan,following the river’s course back to where the cooperation journey began.
