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
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
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
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
I have just returned from another inspiring journey through China,which has compelled me to reflect on today’s complex international landscape and the need to strengthen people-to-people diplomacy as a key tool to ad...I have just returned from another inspiring journey through China,which has compelled me to reflect on today’s complex international landscape and the need to strengthen people-to-people diplomacy as a key tool to address the global common challenges that lie ahead.The opportunity to witness first-hand China’s economic,technological,and social development–as well as its willingness to open up and collaborate with the rest of the world–has prompted me to have a realistic diagnosis of future challenges and the design of effective strategies to improve the lives of our citizens.展开更多
A steel-concrete composite cable-stayed bridge features integrated steel girders and concrete decks linked by shear connectors to support loads,but stress concentration in wet joints can lead to cracking.In-situ tests...A steel-concrete composite cable-stayed bridge features integrated steel girders and concrete decks linked by shear connectors to support loads,but stress concentration in wet joints can lead to cracking.In-situ tests were conducted on key sections of steel-concrete composite cable-stayed bridges to analyze the stress-strain evolution of wet joints under environmental factors,constraints,and complex construction processes.The coordinated working performance of the bridge decks was also analyzed.The results indicate that temperature is the key factor affecting the stresses and strains in wet joint concrete.Approximately 7 days after casting the wet joint concrete,the strains at each measurement point of the wet joint are approximately negatively correlated with the temperature change at the measurement point.Different locations within the wet joints have respective impacts,presenting potential weak points.Construction conditions have a certain impact on the stress and strain of the wet joint.The top deck of the steel box girder is not fully bonded to the bottom surface of the wet joints,resulting in a certain strain difference after loading.To further analyze the cooperative working performance of steel box girders and concrete wet joint bridge deck systems,finite element analysis was conducted on composite girder structures.A stiffness calculation method for shear connectors based on numerical simulation was proposed.The results indicate that strain differences can cause interface slip in composite girders.This slip leads to increased deflection of the composite girders and increased tensile stress in the bottom plate of the steel box girders.This study clarifies the stress conditions and factors affecting wet joints during construction,preventing early cracking,and offers precise data for a full bridge finite element model.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
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
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
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
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
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
Tuning the conjugated bridges between the electron-donor and electron-acceptor moieties plays a crucial role in enhancing the memristive properties of organic materials,yet it is rarely reported.Herein,we designed and...Tuning the conjugated bridges between the electron-donor and electron-acceptor moieties plays a crucial role in enhancing the memristive properties of organic materials,yet it is rarely reported.Herein,we designed and synthesized four donor-acceptor(D-A)organic small molecules,namely 4,7-bis(4-((9H-fluoren-9-ylidene)(phenyl)methyl)phenyl)benzo[c][1,2,5]thiadiazole(DF-BT),4,7-bis((4-((9H-fluoren-9-ylidene)(phenyl)methyl)phenyl)ethynyl)benzo[c][1,2,5]thiadiazole(DF-ynl-BT),4,7-bis(5-(4-((9H-fluoren-9-ylidene)(phenyl)methyl)phenyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole(DF-Th-BT),and 4,7-bis((5-(4-((9H-fluoren-9-ylidene)(phenyl)methyl)phenyl)thiophen-2-yl)ethynyl)benzo[c][1,2,5]thiadiazole(DF-Th-ynl-BT),featuring unique conjugated bridges.These molecules were employed as active layers in resistive random-access memory(RRAM)devices to systematically investigate the influence of conjugation bridges on the electrical parameters.The results revealed that devices based on DF-BT,DF-ynl-BT,and DF-Th-BT exhibited write-once-read-many-times(WORM)characteristics,while the DF-Th-ynl-BT-based device demonstrated stable Flash-type switching behavior.Compared to DF-BT,memory devices utilizing DF-ynl-BT,DF-Th-BT,and DF-Th-ynl-BT,which incorporate additional conjugated bridges,exhibited nonvolatile memory properties with reduced threshold voltages,an improved ON/OFF current ratio,enhanced stability,and better uniformity.These findings demonstrated that tailoring the conjugated bridges in D-A molecules can effectively modulate resistive memory behavior and enhance device performance.Furthermore,the DF-Th-ynl-BT-based device was successfully integrated into logic gate circuits and display functions,highlighting its significant potential for applications in artificial intelligence(AI)neural networks.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
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
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
Streamlined box girders serve as a prevalent choice for the primary structural elements in large-span suspension bridge designs.With the increase in traffic demands,the design of such girders is evolving towards wider...Streamlined box girders serve as a prevalent choice for the primary structural elements in large-span suspension bridge designs.With the increase in traffic demands,the design of such girders is evolving towards wider bridge decks and larger aspect ratios(B/D).To obtain more effective and aerodynamic design shapes for streamlined box girders,it is essential to investigate the impact of B/D on their aerodynamic performance.Accordingly,in this study we investigate the buffeting responses of large-span suspension bridges using girders of varying aspect ratios(B/D of 7.5,9.3,and 12.7).First,the aerodynamic coefficients of these girders are estimated using computational fluid dynamics(CFD)simulations.Subsequently,spatial finite element(FE)models of three long-span suspension bridges with different girders(B/D of 7.5,9.3,and 12.7)are established in Ansys software,and the dynamic characteristics of these bridges are obtained.Then,the time-domain buffeting analysis is performed by simulating the fluctuating wind fields acting on the bridge through the spectral representation method.Ultimately,the buffeting responses are computed using Ansys software,and the impact of B/D on these responses is assessed.The results reveal that the root mean square(RMS)values of the main girder’s buffeting displacement are highest at the midspan position and are lowest at the ends of the bridge.A decrease in B/D of the main girder leads to a more severe buffeting response because both the range and the effective value of the displacement increase with the decreasing B/D.Comparing the buffeting displacements in three directions,B/D plays a significant role in the vertical buffeting displacement,moderately impacts the torsional displacement,and has the least effect on the lateral displacement.The findings of this study may help wind resistance analysis and design optimization for bridges.展开更多
Failure tests were conducted on two concrete-filled steel tubular(CFST)truss arch bridges with a span of approximately 12 m to investigate the influence of initial geometric defects on the in-plane bearing capacity of...Failure tests were conducted on two concrete-filled steel tubular(CFST)truss arch bridges with a span of approximately 12 m to investigate the influence of initial geometric defects on the in-plane bearing capacity of CFST truss arch bridges.The effects of antisymmetric defect on the ultimate bearing capacity,failure mode,structural response,and steel–concrete confinement effect of CFST truss arch bridges under quarter-point loading were analyzed.On this basis,numerical simulations were conducted to investigate the in-plane bearing capacity of CFST truss arch bridges further under different scenarios.The initial defect formof the archwas obtained by using theoretical deduction,and the theoretical basis for the weakening of the ultimate bearing capacity of the arch bridge caused by geometric defects was clarified.Results indicate that the antisymmetric defect does not change the four-hinge failure mode of the model arch under quarter-point loading but increases the local cracking area and crack density of the concrete inside the pipe.The sine geometric defect with an amplitude of L/250 resulted in a 44.4%decrease in the yield load of the single hinge of the model arch,a 10.5%decrease in the failure load of the four hinges,and a 40.9%increase in themaximum vertical deformation during failure.At the initial stage of loading,the steel pipe and the concrete inside the pipe were subjected to relatively independent forces.After reaching 67%of the ultimate load,the catenary arch ribs began to produce a steel pipe concrete constraint effect.The initial geometric defects resulted in a decrease in the load when the constraint effect occurred.The antisymmetric defects with the same amplitude have a greater impact on the in-plane bearing capacity of the CFST arch bridge than the initial geometric defects with symmetry.The linear deviation at L/4 caused by constructionmust be controlled to be less than L/600 to ensure that the internal bearing capacity of the CFST arch bridge reaches 95%of the design bearing capacity.The structural deformation caused by geometric initial defects increases linearly with the increase in defect amplitude.The bearing capacity is weakened because the structural deflection and bending moment are amplified by initial defects.展开更多
This study focuses on the hydrated ion bridge(HIB)effect at the oil-rock interface in low-to ultra-low-permeability oil reservoirs.It systematically summarizes the research methodologies,formation mechanisms,interacti...This study focuses on the hydrated ion bridge(HIB)effect at the oil-rock interface in low-to ultra-low-permeability oil reservoirs.It systematically summarizes the research methodologies,formation mechanisms,interaction strength,and disruption mechanisms of HIB,and discusses the influencing mechanisms of HIB on the occurrence state and mobility of crude oil.On this basis,the key challenges inherent in the current HIB research are analyzed,and prospective directions for future development are proposed.Currently,research in this field primarily relies on experimental characterization techniques and molecular simulation methods.The microscopic interactions involved in HIB formation mainly include electrostatic interactions,hydrogen bonds and van der Waals forces.Notably,the hydrogen bonds between polar molecules in crude oil and hydrated ions serve as the primary sites for disrupting the HIB effect.The interaction strength of HIB is collectively modulated by ion type and concentration,reservoir solution environment,mineral type of reservoir rocks,and polar components in crude oil,which subsequently influence the occurrence state and mobility of crude oil.Systematic challenges persist in HIB-related research across three dimensions:research methodologies,scale integration and geological complexity.Specifically,the dynamic evolution mechanism of HIB remains inadequately elucidated;a discontinuity exists in the connection of spatiotemporal cross-scale modeling and prediction;and the reproducibility of actual geological environments in experimental settings is insufficient.Future research may pursue breakthroughs in the following three aspects:(1)developing in-situ dynamic experimental characterization techniques and machine learning-augmented simulation strategies;(2)establishing a framework for cross-scale model fusion and upscaling prediction;and(3)conducting in-depth studies on HIB under the coupled effects of complex mineral systems and multi-physical fields.展开更多
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I have just returned from another inspiring journey through China,which has compelled me to reflect on today’s complex international landscape and the need to strengthen people-to-people diplomacy as a key tool to address the global common challenges that lie ahead.The opportunity to witness first-hand China’s economic,technological,and social development–as well as its willingness to open up and collaborate with the rest of the world–has prompted me to have a realistic diagnosis of future challenges and the design of effective strategies to improve the lives of our citizens.
文摘A steel-concrete composite cable-stayed bridge features integrated steel girders and concrete decks linked by shear connectors to support loads,but stress concentration in wet joints can lead to cracking.In-situ tests were conducted on key sections of steel-concrete composite cable-stayed bridges to analyze the stress-strain evolution of wet joints under environmental factors,constraints,and complex construction processes.The coordinated working performance of the bridge decks was also analyzed.The results indicate that temperature is the key factor affecting the stresses and strains in wet joint concrete.Approximately 7 days after casting the wet joint concrete,the strains at each measurement point of the wet joint are approximately negatively correlated with the temperature change at the measurement point.Different locations within the wet joints have respective impacts,presenting potential weak points.Construction conditions have a certain impact on the stress and strain of the wet joint.The top deck of the steel box girder is not fully bonded to the bottom surface of the wet joints,resulting in a certain strain difference after loading.To further analyze the cooperative working performance of steel box girders and concrete wet joint bridge deck systems,finite element analysis was conducted on composite girder structures.A stiffness calculation method for shear connectors based on numerical simulation was proposed.The results indicate that strain differences can cause interface slip in composite girders.This slip leads to increased deflection of the composite girders and increased tensile stress in the bottom plate of the steel box girders.This study clarifies the stress conditions and factors affecting wet joints during construction,preventing early cracking,and offers precise data for a full bridge finite element model.
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.
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supported by the financial support from the National Natural Science Foundation of China(Grant Nos.:62174116 and 61774109)the start-up fund from Shanghai University.
文摘Tuning the conjugated bridges between the electron-donor and electron-acceptor moieties plays a crucial role in enhancing the memristive properties of organic materials,yet it is rarely reported.Herein,we designed and synthesized four donor-acceptor(D-A)organic small molecules,namely 4,7-bis(4-((9H-fluoren-9-ylidene)(phenyl)methyl)phenyl)benzo[c][1,2,5]thiadiazole(DF-BT),4,7-bis((4-((9H-fluoren-9-ylidene)(phenyl)methyl)phenyl)ethynyl)benzo[c][1,2,5]thiadiazole(DF-ynl-BT),4,7-bis(5-(4-((9H-fluoren-9-ylidene)(phenyl)methyl)phenyl)thiophen-2-yl)benzo[c][1,2,5]thiadiazole(DF-Th-BT),and 4,7-bis((5-(4-((9H-fluoren-9-ylidene)(phenyl)methyl)phenyl)thiophen-2-yl)ethynyl)benzo[c][1,2,5]thiadiazole(DF-Th-ynl-BT),featuring unique conjugated bridges.These molecules were employed as active layers in resistive random-access memory(RRAM)devices to systematically investigate the influence of conjugation bridges on the electrical parameters.The results revealed that devices based on DF-BT,DF-ynl-BT,and DF-Th-BT exhibited write-once-read-many-times(WORM)characteristics,while the DF-Th-ynl-BT-based device demonstrated stable Flash-type switching behavior.Compared to DF-BT,memory devices utilizing DF-ynl-BT,DF-Th-BT,and DF-Th-ynl-BT,which incorporate additional conjugated bridges,exhibited nonvolatile memory properties with reduced threshold voltages,an improved ON/OFF current ratio,enhanced stability,and better uniformity.These findings demonstrated that tailoring the conjugated bridges in D-A molecules can effectively modulate resistive memory behavior and enhance device performance.Furthermore,the DF-Th-ynl-BT-based device was successfully integrated into logic gate circuits and display functions,highlighting its significant potential for applications in artificial intelligence(AI)neural networks.
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.
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.
基金funded by the National Natural Science Foundation of China(Grant No.52108435)the Science and Technology Research Program of Chongqing Municipal Education Commission(Grant No.KJQN202404320)+1 种基金Chongqing Jiaotong University Postgraduate Research and Innovation Project(2024S0013)Chongqing Jiaotong University Undergraduate Innovation and Entrepreneurship Project(S202410618019).
文摘Streamlined box girders serve as a prevalent choice for the primary structural elements in large-span suspension bridge designs.With the increase in traffic demands,the design of such girders is evolving towards wider bridge decks and larger aspect ratios(B/D).To obtain more effective and aerodynamic design shapes for streamlined box girders,it is essential to investigate the impact of B/D on their aerodynamic performance.Accordingly,in this study we investigate the buffeting responses of large-span suspension bridges using girders of varying aspect ratios(B/D of 7.5,9.3,and 12.7).First,the aerodynamic coefficients of these girders are estimated using computational fluid dynamics(CFD)simulations.Subsequently,spatial finite element(FE)models of three long-span suspension bridges with different girders(B/D of 7.5,9.3,and 12.7)are established in Ansys software,and the dynamic characteristics of these bridges are obtained.Then,the time-domain buffeting analysis is performed by simulating the fluctuating wind fields acting on the bridge through the spectral representation method.Ultimately,the buffeting responses are computed using Ansys software,and the impact of B/D on these responses is assessed.The results reveal that the root mean square(RMS)values of the main girder’s buffeting displacement are highest at the midspan position and are lowest at the ends of the bridge.A decrease in B/D of the main girder leads to a more severe buffeting response because both the range and the effective value of the displacement increase with the decreasing B/D.Comparing the buffeting displacements in three directions,B/D plays a significant role in the vertical buffeting displacement,moderately impacts the torsional displacement,and has the least effect on the lateral displacement.The findings of this study may help wind resistance analysis and design optimization for bridges.
基金National Natural Science Foundation of China(Grant No.52408314)Science and Technology Project of Sichuan Provincial TransportationDepartment(GrantNo.2023-ZL-03)Science and Technology Project of Guizhou Provincial Transportation Department(Grant No.2024-122-018).
文摘Failure tests were conducted on two concrete-filled steel tubular(CFST)truss arch bridges with a span of approximately 12 m to investigate the influence of initial geometric defects on the in-plane bearing capacity of CFST truss arch bridges.The effects of antisymmetric defect on the ultimate bearing capacity,failure mode,structural response,and steel–concrete confinement effect of CFST truss arch bridges under quarter-point loading were analyzed.On this basis,numerical simulations were conducted to investigate the in-plane bearing capacity of CFST truss arch bridges further under different scenarios.The initial defect formof the archwas obtained by using theoretical deduction,and the theoretical basis for the weakening of the ultimate bearing capacity of the arch bridge caused by geometric defects was clarified.Results indicate that the antisymmetric defect does not change the four-hinge failure mode of the model arch under quarter-point loading but increases the local cracking area and crack density of the concrete inside the pipe.The sine geometric defect with an amplitude of L/250 resulted in a 44.4%decrease in the yield load of the single hinge of the model arch,a 10.5%decrease in the failure load of the four hinges,and a 40.9%increase in themaximum vertical deformation during failure.At the initial stage of loading,the steel pipe and the concrete inside the pipe were subjected to relatively independent forces.After reaching 67%of the ultimate load,the catenary arch ribs began to produce a steel pipe concrete constraint effect.The initial geometric defects resulted in a decrease in the load when the constraint effect occurred.The antisymmetric defects with the same amplitude have a greater impact on the in-plane bearing capacity of the CFST arch bridge than the initial geometric defects with symmetry.The linear deviation at L/4 caused by constructionmust be controlled to be less than L/600 to ensure that the internal bearing capacity of the CFST arch bridge reaches 95%of the design bearing capacity.The structural deformation caused by geometric initial defects increases linearly with the increase in defect amplitude.The bearing capacity is weakened because the structural deflection and bending moment are amplified by initial defects.
基金Supported by the National Key Research and Development Program,China(2019YFA0708700)National Natural Science Foundation of China(52542310).
文摘This study focuses on the hydrated ion bridge(HIB)effect at the oil-rock interface in low-to ultra-low-permeability oil reservoirs.It systematically summarizes the research methodologies,formation mechanisms,interaction strength,and disruption mechanisms of HIB,and discusses the influencing mechanisms of HIB on the occurrence state and mobility of crude oil.On this basis,the key challenges inherent in the current HIB research are analyzed,and prospective directions for future development are proposed.Currently,research in this field primarily relies on experimental characterization techniques and molecular simulation methods.The microscopic interactions involved in HIB formation mainly include electrostatic interactions,hydrogen bonds and van der Waals forces.Notably,the hydrogen bonds between polar molecules in crude oil and hydrated ions serve as the primary sites for disrupting the HIB effect.The interaction strength of HIB is collectively modulated by ion type and concentration,reservoir solution environment,mineral type of reservoir rocks,and polar components in crude oil,which subsequently influence the occurrence state and mobility of crude oil.Systematic challenges persist in HIB-related research across three dimensions:research methodologies,scale integration and geological complexity.Specifically,the dynamic evolution mechanism of HIB remains inadequately elucidated;a discontinuity exists in the connection of spatiotemporal cross-scale modeling and prediction;and the reproducibility of actual geological environments in experimental settings is insufficient.Future research may pursue breakthroughs in the following three aspects:(1)developing in-situ dynamic experimental characterization techniques and machine learning-augmented simulation strategies;(2)establishing a framework for cross-scale model fusion and upscaling prediction;and(3)conducting in-depth studies on HIB under the coupled effects of complex mineral systems and multi-physical fields.
