The road construction industry aims to contribute to the protection of already compromised environment.Cold mix asphalt(CMA)is a measure initiated by the road industry to protect the environment and preserve energy.De...The road construction industry aims to contribute to the protection of already compromised environment.Cold mix asphalt(CMA)is a measure initiated by the road industry to protect the environment and preserve energy.Despite having additional benefits,CMA has attracted little attention due to its inferior performance.CMA's performance is enhanced using a sustainable binder bio-modifier,natural cup lump rubber(CLR)is one of them.This study evaluated the tensile properties,rutting,moisture susceptibility,and adhesion properties of CLR-modified CMA(CMA-CR).The tensile property was enhanced by 26%due to CLR modification.CMA-CR had excellent rutting resistance of less than 2 mm rut depth at 10,000 load cycles,showing 70%improvement compared with conventional CMA.Moisture susceptibility evaluation indicated that CMA-CR had tensile strength ratio(TSR)value of 104%,satisfying the minimum 80%requirement of AASHTO T283.It also retained more than 96%bitumen coating.The moisture damage resistance was improved by 12%and 10%in terms of TSR and stripping,respectively.The durability results revealed that the CMA-CR mixture prevented higher mass loss,representing 14%improvement compared with conventional CMA.展开更多
Pavement skid resistance plays a crucial role in ensuring road safety and avoiding accidents.In the past,the laboratory evaluation of the skid resistance was carried out by studying only the coarse aggregates of the w...Pavement skid resistance plays a crucial role in ensuring road safety and avoiding accidents.In the past,the laboratory evaluation of the skid resistance was carried out by studying only the coarse aggregates of the wearing course.To overcome this drawback,the Wehner-Schulze(WS)machine was developed in Germany in the 1960s.This equipment,composed of a polishing unit and a measuring unit,has great potential in predicting pavement skid resistance and its evolution over time,but is still little known in the pavement community(especially outside Europe).For these reasons,there is a need of a comprehensive review of the existing technical-scientific literature concerning the use of the WS machine.Specifically,this paper focuses on the main factors affecting the skid resistance in WS tests,the correlation of WS data with other laboratory test methods and with field skid resistance/polishing,and the available prediction models that have been validated through WS measurements.The critical analysis of the existing literature highlights that it is possible to correlate WS data with typical skid resistance field measurements as well as WS polishing with traffic polishing,but further efforts are needed in this regard.Future work should focus especially on open-graded mixtures and innovative asphalt mixtures(e.g.,containing recycled materials and additives).From the perspective of pavement management,based on a theoretical background,the WS test results could be used as starting point for simplified prediction models of the in-situ skid resistance.展开更多
The morphology of graded crushed stone(GCS)particles has an essential influence on the performance of aggregate mixtures.The impact of particle shape is a comprehensive effect that cannot be considered separately,lead...The morphology of graded crushed stone(GCS)particles has an essential influence on the performance of aggregate mixtures.The impact of particle shape is a comprehensive effect that cannot be considered separately,leading to difficulties in establishing the relationship between the mixture properties and the aggregate morphology by using laboratory methods.The discrete element method(DEM)is an effective way widely adopted to reconstruct the morphology of particles and simulate performance tests of granular materials.However,selecting limited particles characterizing a real particle-assembly for simulation is still a challenge in current research due to the inherent rich variability of particle shapes.In this study,based on the acquisition of three-dimensional(3D)aggregate shapes by using laser scanning,ellipsoid index(EDI)translating the particle shape as a function of surface area,volume,and contour length is proposed to comprehensively evaluate aggregate morphology.Further,a particle library capable of characterizing aggregate morphology distribution is established based on the statistics of the corresponding morphological characteristics of particle samples.The model reliability is validated by carrying out a series of experimental and numerical penetration tests with nine different gradations.The established particle library can be used to model aggregate mixtures and the proposed simulation framework is promising for optimizing the mixture gradation design numerically.展开更多
The rapid growth of urban traffic has intensified daily congestion,affecting both traffic flow and parking.Accurate parking prediction plays a vital role in effectively managing limited parking resources and is essent...The rapid growth of urban traffic has intensified daily congestion,affecting both traffic flow and parking.Accurate parking prediction plays a vital role in effectively managing limited parking resources and is essential for the successful implementation of advanced intelligent systems.In an effort to comprehensively assess the latest developments in parking prediction,we curated a dataset of 639 articles spanning from 2010 to the present,using the Scopus database.Initially,we performed a bibliometric analysis utilizing VOSviewer software.These findings not only illuminate emerging trends within the parking prediction field but also provide strategic guidance for its progression.Subsequently,we categorized advancements in three focal areas:behavior prediction,demand prediction,and parking space prediction.A comprehensive overview of the present research status and future directions was then provided.The findings underscore the substantial progress achieved in current parking prediction models,achieved through diverse avenues like multi-source data integration,multi-variable feature extraction,nonlinear relationship modeling,deep learning techniques application,and ensemble model utilization.These innovative endeavors have not only pushed the theoretical boundaries of parking prediction but also significantly heightened the precision and applicability of predictive models in practical scenarios.Prospective research should explore avenues such as processing unstructured parking datasets,developing predictive models for small-scale data,mitigating noise interference in parking data,and harnessing potent platform fusion techniques.This study's significance transcends guiding and catalyzing advancement in academic and practical domains;it holds paramount relevance across academic research,technological innovation,decision-making support,business applications,and policy formulation.展开更多
This review examines the potential of hydrogen,ammonia,and biodiesel as alternative fuels,focusing on spray dynamics,droplet evaporation,combustion,and emissions.Hydrogen offers superior combustion characteristics but...This review examines the potential of hydrogen,ammonia,and biodiesel as alternative fuels,focusing on spray dynamics,droplet evaporation,combustion,and emissions.Hydrogen offers superior combustion characteristics but faces challenges in NO_(x)emissions.Strategies like nonpremixed direct injection,increased intake boost pressure,and low-pressure EGR are suggested for robust hydrogen combustion in compression-ignition engines.Control of hydrogen start of injection(SOI)and water injection(WI)are identified as effective techniques for reducing NO_(x)emissions.Ammonia shows inferior combustion and higher NO_(x)and unburned NH_(3)emissions in the same conditions as conventional fuels with conventional engines.Understanding ammonia spray and evaporation conditions is significant for optimizing an ammonia-air mixture and minimizing wall impingement and ammonia trap in the crevice,thereby improving combustion and emission reduction.Increasing intake pressure,injection pressure,and EGR rate,employing a turbulent jet,and preheating ammonia improve efficiency and reduce NO_(x)emissions.Utilizing ammonia combustion requires the implementation of after-treatment systems such as NH_(3)adsorber and De NO_(x)catalysts to mitigate unburned NH_(3)and NO_(x)emissions.Biodiesel affects the fuel supply system,combustion,and emission characteristics according to its viscosity and density.Increasing injection pressure and blending with volatile fuels enhance spray and combustion.Optimum biodiesel preheating temperatures for the injection pump and injector are crucial for achieving the best pump capacity and spray formation.By utilizing biodiesel-PODE blends and investigating low-temperature biodiesel combustions,there is potential to improve thermal efficiency and PMNO_(x)trade-off.Therefore,carbon-neutral fuel adoption should be accelerated to mitigate CO_(2)emissions,highlighting the importance of combustion techniques and emissions reduction strategies.展开更多
Good compatibility between waterborne epoxy resin(WER)modifier and styrene-butadiene rubber(SBR)latex modified asphalt emulsion(SBRE)is an essential premise for good pavement performance of WER and SBR latex composite...Good compatibility between waterborne epoxy resin(WER)modifier and styrene-butadiene rubber(SBR)latex modified asphalt emulsion(SBRE)is an essential premise for good pavement performance of WER and SBR latex compositely modified asphalt emulsion(WSAE).This study aims to explore the compatibility between WER modifier and SBRE.To achieve the goal,several WER modifiers produced by two methods were first selected to modify SBRE,thus the WSAEs were prepared.Next,storage stability and workability of the WSAEs themselves,and high-temperature performance,rheological behavior and temperature sensitivity of their evaporated residues were compared and evaluated via performing a series of experiments,respectively,thus the WER modifier possessing an optimal modification effect was recommended.Results show that the storage stability of WSAEs is sensitive to the amount of WERs.The incorporation of 1%WERs by the mass of SBRE improves the storage stability of SBRE,while WERs that exceed 1%weaken its storage stability.When the WERs reach 3%and 4%,the 5 d storage stability of prepared WSAEs will be beyond the limitation of specification.Incorporating WERs into SBRE negatively affects the workability of SBRE,and the workability of WSAEs is adversely influenced by the WERs content and the storage time.To ensure the construction,the WSAEs with 3%and 4%WERs should not be stored for more than 36 h and 48 h,respectively.The WERs effectively improve the high-temperature performance of SBRE residue,especially the 3%WERs.Besides,the WERs notably enhance the rheological property and thermal stability of SBRE residue.In contrast,the WER modifier produced by chemically modified method has a smaller adverse impact on the storage stability and workability of WSAE,and a larger enhancement on the high-temperature performance,rheological property and thermal stability of SBRE residue,which is thus recommended to modify SBRE.展开更多
Microwave heating,which is used for pre-treatment of concrete before it is comminuted,stands as a strong candidate for selective liberation of multiphase materials like concrete.This paper is concerned with the select...Microwave heating,which is used for pre-treatment of concrete before it is comminuted,stands as a strong candidate for selective liberation of multiphase materials like concrete.This paper is concerned with the selective liberation of concrete's raw constituents(particularly aggregate)for recycling by considering the water content of concrete as a parameter of microwave heating for the first time.The deterioration law of the concrete's performance was characterized by the variation in the splitting tensile strength and relative dynamic modulus after heating by microwave at different water contents.Besides,tests were conducted to evaluate the performance of the interface transition zone(ITZ)between aggregate and mortar as well as to investigate the reasons for the stripping behavior of aggregate-mortar,which included the interface tensile strength test,temperature measurement,and porosity test.The deterioration law of splitting tensile strength and relative dynamic modulus revealed that the performance of concrete was subject to different degrees of damage depending on the water content.Furthermore,experimental results showed that interface bonding strength between aggregate and mortar was dramatically impaired,and a large temperature difference was generated between the aggregate and mortar during microwave heating.Meanwhile,the permeable pores increased considerably even when the specimens were dried.In the presence of water,the intactness of ITZ between aggregate and mortar was destroyed by microwave heating,and its performance was significantly lowered,which led to the occurrence of stripping behavior between aggregate and mortar.This was reaffirmed by the microstructure presented by scanning electron microscopy.Thus,the newly developed microwave pretreatment improved by providing appropriate water contents for concrete corresponding to different strength grades is a promising method for recycling aggregate from waste concrete.展开更多
The Portland cement concrete pavement(PCCP)often suffers from different environmental distresses and vehicle load failure,resulting in slab corner fractures,potholes,and other diseases.Rapid repair has become one of t...The Portland cement concrete pavement(PCCP)often suffers from different environmental distresses and vehicle load failure,resulting in slab corner fractures,potholes,and other diseases.Rapid repair has become one of the effective ways to open traffic rapidly.In this study,a novel type of rapid repair material,basalt fiber reinforced polymer modified magnesium phosphate cement(BFPMPC),is used to rapidly repair PCCP.Notably,the mechanical properties and characteristics of the repair interfaces which are named interfacial transition zones(ITZs)formed by BFPMPC and cement concrete are focused on as a decisive factor for the performance of the rapid repair.The changing trend of the elastic moduli was studied by nanoindentation experiments in the ITZs with the deconvolution analysis that the elastic moduli of certain kinds of substances can be determined.The experimental results show that the elastic modulus of ITZ-1 with a width of about20μm can be regarded as 0.098 times of the aggregate,and 0.51 times of the ordinary Portland cement(OPC)mortar.The BFPMPC-OPC mortar ITZ has roughly the same mechanical properties as the ITZ between aggregate and BFPMPC.A multi-scale representative two-dimensional model was established by random aggregate and a two-dimensional extended finite element method(XFEM)to study the mechanical properties of the repair interface.The simulation results show that the ITZ formed by the interface of BFPMPC and OPC mortar and basalt aggregate is the most vulnerable to failure,which is consistent with the nano-indentation experimental results.展开更多
Sight obstructions along road curves can lead to a crash if the driver is not able to stop the vehicle in time.This is a particular issue along curves with limited available sight,where speed management is necessary t...Sight obstructions along road curves can lead to a crash if the driver is not able to stop the vehicle in time.This is a particular issue along curves with limited available sight,where speed management is necessary to avoid unsafe situations(e.g.,driving off the road or invading the other traffic lane).To solve this issue,we proposed a novel intelligent speed adaptation(ISA)system for visibility,called V-ISA(intelligent speed adaptation for visibility).It estimates the real-time safe speed limits based on the prevailing sight conditions.V-ISA comes with three variants with specific feedback modalities(1)visual and(2)auditory information,and(3)direct intervention to assume control over the vehicle speed.Here,we investigated the efficiency of each of the three V-ISA variants on driving speed choice and lateral behavioural response along road curves with limited and unsafe available sight distances,using a driving simulator.We also considered curve road geometry(curve direction:rightward vs.leftward).Sixty active drivers were recruited for the study.While half of them(experimental group)tested the three V-ISA variants(and a V-ISA off condition),the other half always drove with the V-ISA off(validation group).We used a linear mixed-effect model to evaluate the influence of V-ISA on driver behaviour.All V-ISA variants were efficient at reducing speeds at entrance points,with no discernible negative impact on driver lateral behaviour.On rightward curves,the V-ISA intervening variant appeared to be the most effective at adapting to sight limitations.Results of the current study implies that V-ISA might assist drivers to adjust their operating speed as per prevailing sight conditions and,consequently,establishes safer driving conditions.展开更多
Load limits,which appear to be routinely exceeded by trucks,occasionally result in road bridge failures.Therefore,predicting failures is crucial for safeguarding road safety.Past studies have largely focused on foreca...Load limits,which appear to be routinely exceeded by trucks,occasionally result in road bridge failures.Therefore,predicting failures is crucial for safeguarding road safety.Past studies have largely focused on forecasting bridge failure event probability using the reliability analysis method,whilst occasionally accounting for vehicular overloading effects.Only recently,a study has investigated design traffic overloading event frequency using generalised linear regression models(GLRMs),including a power component and negative binomial regressions(NBRs).However,as far as the authors know,artificial neural network models(ANNMs)have never been applied to this field.This paper is an attempt to fill in these gaps.First a frequencybased metric of traffic overloading was adopted as a driver of failure probability.Second,two alternative‘frequency'models were specified,calibrated,and validated.The former was based on a GLRM,the latter on ANNMs.Then,these models were compared using regression plots(RPs),measures of errors(Mo Es)and the ratio between the number of observed vs predicted design load overcoming events to evaluate their performance.The models analysed more than 2 million weigh-in-motion(WIM)data records from a pilot station on a bridge on a heavily used ring road in Brescia(Italy).Results showed that ANNMs outperformed GLRMs.ANNMs have a higher correlation coefficient(between predicted and target frequencies),lower Mo Es,and a closer-to-unity ratio(between predicted and target frequencies).These findings may increase prediction accuracy of design traffic overloading events and give road authorities more effective traffic management to protect bridges from load hazards.展开更多
In recent years,e-scooters have been introduced in many European cities.In several places we have witnessed a rapid uptake of this new mode of transport mainly as a result of public sharing schemes.A number of inciden...In recent years,e-scooters have been introduced in many European cities.In several places we have witnessed a rapid uptake of this new mode of transport mainly as a result of public sharing schemes.A number of incidents,injuries and even fatalities have given rise to questions regarding the safety of these vehicles.These questions are being researched mainly using official crash data and data specifying injuries and hospital treatment.Until now,the research has focused on investigating typical injury patterns and estimating risk levels.Very little is known about exactly where conflicts and crashes occur.Knowledge of hazard hotspots is crucial when investigating risk levels and improving safety for all road users.Hence,this paper develops an approach to investigating locations with potentially dangerous interactions within the active mobility system in the city of Berlin.The approach consists of explorative expert interviews,an online poll,and quantitative analyses.For the latter we combine three datasets.First,we research crash hotspots using official data.Second,we use data based on acceleration sensors from cyclists'smartphones to find locations of sudden movements.Third,we use trip data from the operators of escooter sharing systems.The information gathered is used in a conclusive expert workshop to identify hazard hotspots.Results show that many of the conflicts with pedestrians are caused by parked escooters.Second,e-scooter trips are concentrated in the inner city and along specific routes.In moving traffic,various data sources are used to identify hotspots at intersections and in areas between intersections.The present research lays the foundation for important further studies to investigate interactions at hotspots in detail by determining nine specific locations in the city of Berlin.展开更多
Pedestrian safety is at high stakes due to the non-compliance practices of pedestrians at signalized intersections.Additionally,when pedestrians are hurrying,they deliberately engage in such unsafe behaviour.Therefore...Pedestrian safety is at high stakes due to the non-compliance practices of pedestrians at signalized intersections.Additionally,when pedestrians are hurrying,they deliberately engage in such unsafe behaviour.Therefore,the purpose of this study was to understand how time pressure(i.e.,feeling of hurry or saving time)affected pedestrians'decisions to follow traffic rules at signalized junctions.To achieve the study objectives,a pedestrian simulator setup was used to collect the crossing behaviour of forty participants at a four-legged signalized intersection.Non-compliance,one of the riskiest pedestrian behaviours,was examined with respect to three different forms,comprising dangerous temporal non-compliance(D-TNC),non-dangerous temporal non-compliance(ND-TNC),and spatial non-compliance(SNC)behaviour under two distinct conditions:baseline(i.e.,no time pressure)and time pressure conditions.The effects of demographics,usual walking features,and time pressure on D-TNC and ND-TNC were investigated using a multinomial regression model,while SNC behaviour was investigated using a binary regression model.It was interesting to note that the majority of the factors related to pedestrians’usual walking behaviour had an impact on all kinds of non-compliance behaviours.Importantly,the results also showcased that time pressure had a contrasting impact on D-TNC and ND-TNC behaviour whereas SNC behaviour increased under time pressure.Additionally,the varying impacts of D-TNC,ND-TNC,and SNC were also reflected in the occurrence of the crashes,which were probably triggered by discrepancies in the influence of time pressure on non-compliance behaviours.These findings highlight the need for technical solutions,educational outreach,and efficient enforcement practices to reduce pedestrians'non-compliant behaviour.展开更多
One of the main factors affecting the safety of signalised intersections is the stop/go behaviour during the yellow interval.Although previous research has exhaustively examined drivers’stop/go decision-making,the ex...One of the main factors affecting the safety of signalised intersections is the stop/go behaviour during the yellow interval.Although previous research has exhaustively examined drivers’stop/go decision-making,the expected autonomous vehicles’(AVs’)stop/go behaviour has not yet been thoroughly investigated.Through a series of simulation experiments developed for conventional and autonomous vehicles using different carfollowing,lane-changing,lateral placement and stop/go model parameter values,we examine here whether the default VISSIM stop/go parameter values can adequately replicate the observed drivers’behaviour at the considered intersection and assess the suitability of using the currently available options,albeit referring to human drivers,to simulate the expected stop/go behaviour of AVs.We also propose a policy framework for determining the desired behaviour of AVs in yellow interval,which is integrated into an AVs logic and achieved in the last simulation to explore the effect of automation on the stop/go outcome and,hence,on the safety level of signalised intersections.Several data analysis and modeling techniques were used for the formulation of certain scenarios,including binary choice models.The default stop/go parameter values were found unfit to replicate the observed stop/go behaviour and subjected to calibration.Compared to the currently available options,the proposed AVs logic proved to produce the most accurate results,in terms of the stop/go simulation outcome.Regarding the impact of automation on the stop/go outcome,the simulation experiments showed that AVs preferred a more conservative behaviour in favor of road safety,as indicated by the significant reduction(≈15%)in the number of vehicles crossing the stop line during the yellow light and zero instances of red light violation.However,compared to the conservative drivers represented by the default stop/go parameter values,AVs preferred a more rational behaviour in favor of intersection capacity without compromising road safety.展开更多
This review evaluated research results on polyvinyl alcohol fiber cement-stabilized macadam(PVA-FCSM)to further improve the long-term durability of road structures and promote its in-depth study and high-quality appli...This review evaluated research results on polyvinyl alcohol fiber cement-stabilized macadam(PVA-FCSM)to further improve the long-term durability of road structures and promote its in-depth study and high-quality application.The suitable PVA fiber technical indexes for ordinary cement-stabilized macadam(CSM)were recommended.The difference in the mechanical properties between CSM and PVA-FCSM was described.The extent to which PVA fibers enhance the durability of CSM were clarified.Additionally,the mechanism of enhancement of CSM by PVA fibers was revealed.Finally,the performance of each type of fiber cement-stabilized macadam(FCSM)was compared and evaluated.The results indicated that the suggested PVA fiber length and content for CSM were 12-30 mm and 0.6-1.2 kg/m^(3),respectively.At different ages,the mean degree of improvement in the unconfined compressive strength was 14%,20%,and 14%,that in the compressive resilience modulus was 8%,11%,and 6%,and that in the splitting strength was 29%,15%,and 22%,respectively.At different ages,the mean degree of decreased in the dry shrinkage coefficient was 21%,16%,and 15%and that in the temperature shrinkage coefficient(20℃-30℃)was 23%,23%,and 18%,respectively.The coefficients increased with extended curing age.Moreover,at the same stress level,PVA-FCSM has a higher fatigue life compared to CSM.The bridging effect,high strength,and high modulus of PVA fiber enhance the strength and anti-cracking of CSM.The recommended fiber type for CSM is PVA fiber.展开更多
Stress concentration factors(SCFs) for welded tubular joints can be decreased by filling the chord with concrete leading to a longer fatigue life. However, there are currently no design formula available in guidelines...Stress concentration factors(SCFs) for welded tubular joints can be decreased by filling the chord with concrete leading to a longer fatigue life. However, there are currently no design formula available in guidelines to predict the SCF of concrete-filled circular hollow section(CFCHS) K-joints, thus limiting their applicability in bridge design. To address this gap,finite element models for CFCHS K-joints were developed and compared against test results to ensure their accuracy. Then, a comprehensive parametric study was conducted to establish relationships between maximum SCFs and four variables: brace-to-chord diameter ratio(β), chord diameter-to-thickness ratio(2γ), brace-to-chord thickness ratio(τ), and the angle between braces and chord(θ). A total of 480 FE models were examined under three loading conditions including brace and chord loading: balanced axial force, chord axial force, and chord bending. Design equations to predict the maximum SCF for CFCHS Kjoints were established by multiple regression analyses of the numerical results. A comparison of maximum SCFs between circular hollow section(CHS) and CFCHS K-joints was made, and it was concluded that average reductions of 42% and 33% in maximum SCFs in CFCHS K-joints at the locations of the chord and brace were found compared to CHS joints for balanced axial force, respectively. Finally, a case study illustrating how to use the proposed equations for fatigue safety verification was presented.展开更多
This study proposes an approach of leveraging information gathered from multiple traffic data sources at different resolutions to obtain approximate inference on the traffic distribution of Chicago's O'Hare Ai...This study proposes an approach of leveraging information gathered from multiple traffic data sources at different resolutions to obtain approximate inference on the traffic distribution of Chicago's O'Hare Airport area.Specifically,it proposes the ingestion of traffic datasets at different resolutions to build spatiotemporal models for predicting the distribution of traffic volume on the road network.Due to its good adaptability and flexibility for spatiotemporal data,the Gaussian process(GP)regression was employed to provide short-term forecasts using data collected by loop detectors(sensors)and supplemented by telematics data.The GP regression is used to make predictions of the distribution of the proportion of sensor data traffic volume represented by the telematics data for each location of the sensors.Consequently,the fitted GP model can be used to determine the approximate traffic distribution for a testing location outside of the training points.Policymakers in the transportation sector can find the results of this work helpful for making informed decisions relating to current and future transportation conditions in the area.展开更多
Modern suspension bridges exhibit a trend of lighter structures,more diversified structural forms,and longer spans,the latter already exceeding two kilometers.Bridge performance under dead and live loads depends on th...Modern suspension bridges exhibit a trend of lighter structures,more diversified structural forms,and longer spans,the latter already exceeding two kilometers.Bridge performance under dead and live loads depends on their structural and main cable systems,while cablesupported bridges especially rely on the design analysis and construction control of the main cable.This literary survey systematically analyzes the research progress and state-ofthe-art status quo in the structural systems and design theories of suspension bridges,focusing on the structural systems,main cable shape analyses,live load effect analyses,and emerging lucrative research directions.More than 100 reliable references have been surveyed.(1)Multi-span or multi-main cable schemes appeal to increasing attention,which may become a better choice in terms of structural systems in scenarios with extremely long spans and heavy loads.The cable layouts,such as spatial main cables and hybrid cable-stayed suspension systems have also become feasible approaches for enhancing structural stiffness.(2)The shape-finding analysis during the construction phase is more complex and has more essential factors than that of the completed bridge state.Refined theories combining analytical methods and finite element methods are more suitable for the shape-finding analysis of complex cable systems than any single theory of the two,especially for novel cable systems.(3)The live load effect analysis methods based on traditional deflection theory or modified/improved deflection theories still have wide applications,but the refined theory of treating hangers as discrete members is also constantly developing,which is expected to provide new ideas for more complex structural analysis under the different types of live loads and their distribution forms.展开更多
In the construction of the Shenzhen-Zhongshan Link,a temporary anchorage system,distributed uniformly along the pipe wall,has been employed.To assess the safety and reliability of this system,a combined method utilizi...In the construction of the Shenzhen-Zhongshan Link,a temporary anchorage system,distributed uniformly along the pipe wall,has been employed.To assess the safety and reliability of this system,a combined method utilizing numerical analysis and model experiments was applied to study the safety of the temporary anchorage system and the reliability of the tension rods.Firstly,an overall model of the caisson segment based on GINA rebound force was established to analyze the stress state of the entire system.Secondly,a comprehensive numerical analysis and model experiment verification were conducted for the single tensioning system,revealing its failure mode and safety margin.The results indicate that the tension rod systems are uniformly stressed at an average of 444 k N during underwater jointing,with a safety factor of 1.94.At this point,the maximum von Mises stresses appearing at the front plate corners and the lower edge of the U-groove,with stress values of 181.8 MPa and 172.4 MPa,and safety factors of 1.54 and 1.71,respectively.When the tension rod force reaches 940 k N,the tensioning system reaches its bearing limit,with initial yielding occurring at the front plate corners.Model experiments were conducted to verify the theoretical analysis results,under a test load of 444 k N,the stresses at the front plate corners and the lower edge of the U-groove were 159.6 and 195.9 MPa,respectively.As the test load increased to 940 k N,these stresses reached 390 and 389 MPa,exhibiting good agreement with the numerical analysis.Considering the uncertainty of loads and materials,a reliability analysis of the tension rods was conducted,yielding a reliability index of 4.34,meeting the secondary safety standard.Based on the comprehensive analysis,it can be concluded that the temporary anchorage system in the caisson segments of the Shenzhen-Zhongshan Link exhibits excellent safety margins.展开更多
Fatigue,corrosion,and bolt loosening are the main causes of structural performance degradation and collapse in steel bridges.Accurate monitoring of steel bridge diseases is a basic premise for ensuring high-quality op...Fatigue,corrosion,and bolt loosening are the main causes of structural performance degradation and collapse in steel bridges.Accurate monitoring of steel bridge diseases is a basic premise for ensuring high-quality operation and maintenance of steel bridges.In this regard,a summary and analysis were conducted on the classification of steel bridge diseases,monitoring and detection methods,application statuses,and major difficulties.The main causes,research status,and development trends of steel bridge diseases are discussed.The results showed that,for fatigue crack problems,fatigue crack initiation has a small scale,high difficulty in monitoring and detection,few methods,and low accuracy.As the cracks grow,the difficulty of monitoring and detection decreases,the number of methods increases,and the accuracy improves.Fatigue crack monitoring and detection are affected by the environmental and vehicular loads.Superficial corrosion features are evident in steel bridges,and corrosion identification methods and technologies are rapidly developing.Monitoring and detecting corrosion in concealed areas is difficult and requires further improvements in monitoring and detection technologies and their accuracy.Monitoring and detection methods and supporting equipment for bolt loosening in steel bridges are rapidly developing.The development of intelligent monitoring and detection technologies and supporting equipment is an important research topic that urgently needs to be addressed for the full-lifecycle operation and maintenance of steel bridges and the sustainable development of bridge engineering.Developing new intelligent sensing components based on high-performance materials and sensing element design theory to improve the monitoring and detection perception ability is an important development direction for steel bridge monitoring and detection.Research on intelligent monitoring and detection technologies,standardized indicators,and related topics based on intelligent operations and maintenance provide great support for the development of steel-bridge disease monitoring and detection.展开更多
The transport sector emits 18%of global CO_(2).Industry and consumers must adopt green mobility to reduce emissions and climate change.This will help achieve sustainability by improving efficiency and reducing greenho...The transport sector emits 18%of global CO_(2).Industry and consumers must adopt green mobility to reduce emissions and climate change.This will help achieve sustainability by improving efficiency and reducing greenhouse gas emissions.Thus,smart electric vehicles(SEVs)have emerged.Digital twins concept and technology may help launch SEVs to the market by analysing and optimising supporting infrastructure.This work aims to fill in the gaps between different pieces of research by giving a full review from a technical and scientifically neutral point of view.The study looks at how digital twin technology can be used in smart car systems by looking at its promise and the hurdles faced.Based on a comprehensive literature survey,this is the first in-depth look at how digital twin technology can be used in smart electric cars.The review has been organised into specific areas of the smart vehicle system,such as drive train system battery management system,driver assistance system,vehicle health monitoring system,vehicle power electronics.This review goes into detail about each component of the car to provide an overall view of the smart vehicle system as a whole.This review makes it easier to understand how digital twin technology can be utilized into each area from a scientific point of view.Lastly,the work looks at the technological and economic impact of digital twin technology,which will make considerable changes in car manufacturing processes,as well as help address current obstacles in utilizing advanced technologies.展开更多
基金financially supported by the UTM Shine(Q.J130000.2451.09G26)the UTM High Impact Research Grant(Q.J130000.2451.09G20)provided by Universiti Teknologi Malaysia(UTM)。
文摘The road construction industry aims to contribute to the protection of already compromised environment.Cold mix asphalt(CMA)is a measure initiated by the road industry to protect the environment and preserve energy.Despite having additional benefits,CMA has attracted little attention due to its inferior performance.CMA's performance is enhanced using a sustainable binder bio-modifier,natural cup lump rubber(CLR)is one of them.This study evaluated the tensile properties,rutting,moisture susceptibility,and adhesion properties of CLR-modified CMA(CMA-CR).The tensile property was enhanced by 26%due to CLR modification.CMA-CR had excellent rutting resistance of less than 2 mm rut depth at 10,000 load cycles,showing 70%improvement compared with conventional CMA.Moisture susceptibility evaluation indicated that CMA-CR had tensile strength ratio(TSR)value of 104%,satisfying the minimum 80%requirement of AASHTO T283.It also retained more than 96%bitumen coating.The moisture damage resistance was improved by 12%and 10%in terms of TSR and stripping,respectively.The durability results revealed that the CMA-CR mixture prevented higher mass loss,representing 14%improvement compared with conventional CMA.
基金financially supported by the Sustainable Mobility Center (Centro Nazionale per la Mobilita Sostenibile-MOST), Spoke 7 (Connected Networks and Smart Infrastructure), Work Package 4 (Resilience of networks, structural health monitoring and asset management) under the National Recovery and Resilience Plan (Piano Nazionale di Ripresa e Resilienza-PNRR)funded by the European Union-NextGenerationEU
文摘Pavement skid resistance plays a crucial role in ensuring road safety and avoiding accidents.In the past,the laboratory evaluation of the skid resistance was carried out by studying only the coarse aggregates of the wearing course.To overcome this drawback,the Wehner-Schulze(WS)machine was developed in Germany in the 1960s.This equipment,composed of a polishing unit and a measuring unit,has great potential in predicting pavement skid resistance and its evolution over time,but is still little known in the pavement community(especially outside Europe).For these reasons,there is a need of a comprehensive review of the existing technical-scientific literature concerning the use of the WS machine.Specifically,this paper focuses on the main factors affecting the skid resistance in WS tests,the correlation of WS data with other laboratory test methods and with field skid resistance/polishing,and the available prediction models that have been validated through WS measurements.The critical analysis of the existing literature highlights that it is possible to correlate WS data with typical skid resistance field measurements as well as WS polishing with traffic polishing,but further efforts are needed in this regard.Future work should focus especially on open-graded mixtures and innovative asphalt mixtures(e.g.,containing recycled materials and additives).From the perspective of pavement management,based on a theoretical background,the WS test results could be used as starting point for simplified prediction models of the in-situ skid resistance.
基金supported by Shandong Hi-speed Group Co.,Ltd.Maintenance Technology Project(grant no.2017B61)National Natural Science Foundation of China(no.52108393)+1 种基金the Fundamental Research Funds for the Central Universities,CHD(no.300102211307)China Scholarship Council(no.201806560055).
文摘The morphology of graded crushed stone(GCS)particles has an essential influence on the performance of aggregate mixtures.The impact of particle shape is a comprehensive effect that cannot be considered separately,leading to difficulties in establishing the relationship between the mixture properties and the aggregate morphology by using laboratory methods.The discrete element method(DEM)is an effective way widely adopted to reconstruct the morphology of particles and simulate performance tests of granular materials.However,selecting limited particles characterizing a real particle-assembly for simulation is still a challenge in current research due to the inherent rich variability of particle shapes.In this study,based on the acquisition of three-dimensional(3D)aggregate shapes by using laser scanning,ellipsoid index(EDI)translating the particle shape as a function of surface area,volume,and contour length is proposed to comprehensively evaluate aggregate morphology.Further,a particle library capable of characterizing aggregate morphology distribution is established based on the statistics of the corresponding morphological characteristics of particle samples.The model reliability is validated by carrying out a series of experimental and numerical penetration tests with nine different gradations.The established particle library can be used to model aggregate mixtures and the proposed simulation framework is promising for optimizing the mixture gradation design numerically.
基金supported by the National Natural Science Foundation of China(No.52062027)the Key Research and Development Project of Gansu Province(No.22YF7GA142)+2 种基金Soft Science Special Project of Gansu Basic Research Plan under grant(No.22JR4ZA035)Gansu Provincial Science and Technology Major Special Project-Enterprise Innovation Consortium Project(No.22ZD6GA010,No.21ZD3GA002)the Natural Science Foundation of Gansu Province(No.22JR5RA343)。
文摘The rapid growth of urban traffic has intensified daily congestion,affecting both traffic flow and parking.Accurate parking prediction plays a vital role in effectively managing limited parking resources and is essential for the successful implementation of advanced intelligent systems.In an effort to comprehensively assess the latest developments in parking prediction,we curated a dataset of 639 articles spanning from 2010 to the present,using the Scopus database.Initially,we performed a bibliometric analysis utilizing VOSviewer software.These findings not only illuminate emerging trends within the parking prediction field but also provide strategic guidance for its progression.Subsequently,we categorized advancements in three focal areas:behavior prediction,demand prediction,and parking space prediction.A comprehensive overview of the present research status and future directions was then provided.The findings underscore the substantial progress achieved in current parking prediction models,achieved through diverse avenues like multi-source data integration,multi-variable feature extraction,nonlinear relationship modeling,deep learning techniques application,and ensemble model utilization.These innovative endeavors have not only pushed the theoretical boundaries of parking prediction but also significantly heightened the precision and applicability of predictive models in practical scenarios.Prospective research should explore avenues such as processing unstructured parking datasets,developing predictive models for small-scale data,mitigating noise interference in parking data,and harnessing potent platform fusion techniques.This study's significance transcends guiding and catalyzing advancement in academic and practical domains;it holds paramount relevance across academic research,technological innovation,decision-making support,business applications,and policy formulation.
基金supported by the Laboratory of Space Utilization and D-Drive Project,Hokkaido University,Japan。
文摘This review examines the potential of hydrogen,ammonia,and biodiesel as alternative fuels,focusing on spray dynamics,droplet evaporation,combustion,and emissions.Hydrogen offers superior combustion characteristics but faces challenges in NO_(x)emissions.Strategies like nonpremixed direct injection,increased intake boost pressure,and low-pressure EGR are suggested for robust hydrogen combustion in compression-ignition engines.Control of hydrogen start of injection(SOI)and water injection(WI)are identified as effective techniques for reducing NO_(x)emissions.Ammonia shows inferior combustion and higher NO_(x)and unburned NH_(3)emissions in the same conditions as conventional fuels with conventional engines.Understanding ammonia spray and evaporation conditions is significant for optimizing an ammonia-air mixture and minimizing wall impingement and ammonia trap in the crevice,thereby improving combustion and emission reduction.Increasing intake pressure,injection pressure,and EGR rate,employing a turbulent jet,and preheating ammonia improve efficiency and reduce NO_(x)emissions.Utilizing ammonia combustion requires the implementation of after-treatment systems such as NH_(3)adsorber and De NO_(x)catalysts to mitigate unburned NH_(3)and NO_(x)emissions.Biodiesel affects the fuel supply system,combustion,and emission characteristics according to its viscosity and density.Increasing injection pressure and blending with volatile fuels enhance spray and combustion.Optimum biodiesel preheating temperatures for the injection pump and injector are crucial for achieving the best pump capacity and spray formation.By utilizing biodiesel-PODE blends and investigating low-temperature biodiesel combustions,there is potential to improve thermal efficiency and PMNO_(x)trade-off.Therefore,carbon-neutral fuel adoption should be accelerated to mitigate CO_(2)emissions,highlighting the importance of combustion techniques and emissions reduction strategies.
基金funded by the National Natural Science Foundation of China(NSFC)under Grant No.211021180360the Transportation Science and Technology in Shaanxi Province under Grant No.KY17-02.
文摘Good compatibility between waterborne epoxy resin(WER)modifier and styrene-butadiene rubber(SBR)latex modified asphalt emulsion(SBRE)is an essential premise for good pavement performance of WER and SBR latex compositely modified asphalt emulsion(WSAE).This study aims to explore the compatibility between WER modifier and SBRE.To achieve the goal,several WER modifiers produced by two methods were first selected to modify SBRE,thus the WSAEs were prepared.Next,storage stability and workability of the WSAEs themselves,and high-temperature performance,rheological behavior and temperature sensitivity of their evaporated residues were compared and evaluated via performing a series of experiments,respectively,thus the WER modifier possessing an optimal modification effect was recommended.Results show that the storage stability of WSAEs is sensitive to the amount of WERs.The incorporation of 1%WERs by the mass of SBRE improves the storage stability of SBRE,while WERs that exceed 1%weaken its storage stability.When the WERs reach 3%and 4%,the 5 d storage stability of prepared WSAEs will be beyond the limitation of specification.Incorporating WERs into SBRE negatively affects the workability of SBRE,and the workability of WSAEs is adversely influenced by the WERs content and the storage time.To ensure the construction,the WSAEs with 3%and 4%WERs should not be stored for more than 36 h and 48 h,respectively.The WERs effectively improve the high-temperature performance of SBRE residue,especially the 3%WERs.Besides,the WERs notably enhance the rheological property and thermal stability of SBRE residue.In contrast,the WER modifier produced by chemically modified method has a smaller adverse impact on the storage stability and workability of WSAE,and a larger enhancement on the high-temperature performance,rheological property and thermal stability of SBRE residue,which is thus recommended to modify SBRE.
基金the financial support from the open project funds for National Major Science and Technology Infrastructure of Materials Service Safety Assessment Facilities,China(MSAF-2020-106)the National Natural Science Foundation of China(No.51808051)。
文摘Microwave heating,which is used for pre-treatment of concrete before it is comminuted,stands as a strong candidate for selective liberation of multiphase materials like concrete.This paper is concerned with the selective liberation of concrete's raw constituents(particularly aggregate)for recycling by considering the water content of concrete as a parameter of microwave heating for the first time.The deterioration law of the concrete's performance was characterized by the variation in the splitting tensile strength and relative dynamic modulus after heating by microwave at different water contents.Besides,tests were conducted to evaluate the performance of the interface transition zone(ITZ)between aggregate and mortar as well as to investigate the reasons for the stripping behavior of aggregate-mortar,which included the interface tensile strength test,temperature measurement,and porosity test.The deterioration law of splitting tensile strength and relative dynamic modulus revealed that the performance of concrete was subject to different degrees of damage depending on the water content.Furthermore,experimental results showed that interface bonding strength between aggregate and mortar was dramatically impaired,and a large temperature difference was generated between the aggregate and mortar during microwave heating.Meanwhile,the permeable pores increased considerably even when the specimens were dried.In the presence of water,the intactness of ITZ between aggregate and mortar was destroyed by microwave heating,and its performance was significantly lowered,which led to the occurrence of stripping behavior between aggregate and mortar.This was reaffirmed by the microstructure presented by scanning electron microscopy.Thus,the newly developed microwave pretreatment improved by providing appropriate water contents for concrete corresponding to different strength grades is a promising method for recycling aggregate from waste concrete.
基金financially supported by the Fundamental Research Funds for the Central Universities(DUT20JC50,DUT17RC(3)006)the National Natural Science Foundation of China(51508137)the Research Center of Civil Aviation Airport Safety and Operation Engineering Technology(KFKT2021-01)。
文摘The Portland cement concrete pavement(PCCP)often suffers from different environmental distresses and vehicle load failure,resulting in slab corner fractures,potholes,and other diseases.Rapid repair has become one of the effective ways to open traffic rapidly.In this study,a novel type of rapid repair material,basalt fiber reinforced polymer modified magnesium phosphate cement(BFPMPC),is used to rapidly repair PCCP.Notably,the mechanical properties and characteristics of the repair interfaces which are named interfacial transition zones(ITZs)formed by BFPMPC and cement concrete are focused on as a decisive factor for the performance of the rapid repair.The changing trend of the elastic moduli was studied by nanoindentation experiments in the ITZs with the deconvolution analysis that the elastic moduli of certain kinds of substances can be determined.The experimental results show that the elastic modulus of ITZ-1 with a width of about20μm can be regarded as 0.098 times of the aggregate,and 0.51 times of the ordinary Portland cement(OPC)mortar.The BFPMPC-OPC mortar ITZ has roughly the same mechanical properties as the ITZ between aggregate and BFPMPC.A multi-scale representative two-dimensional model was established by random aggregate and a two-dimensional extended finite element method(XFEM)to study the mechanical properties of the repair interface.The simulation results show that the ITZ formed by the interface of BFPMPC and OPC mortar and basalt aggregate is the most vulnerable to failure,which is consistent with the nano-indentation experimental results.
文摘Sight obstructions along road curves can lead to a crash if the driver is not able to stop the vehicle in time.This is a particular issue along curves with limited available sight,where speed management is necessary to avoid unsafe situations(e.g.,driving off the road or invading the other traffic lane).To solve this issue,we proposed a novel intelligent speed adaptation(ISA)system for visibility,called V-ISA(intelligent speed adaptation for visibility).It estimates the real-time safe speed limits based on the prevailing sight conditions.V-ISA comes with three variants with specific feedback modalities(1)visual and(2)auditory information,and(3)direct intervention to assume control over the vehicle speed.Here,we investigated the efficiency of each of the three V-ISA variants on driving speed choice and lateral behavioural response along road curves with limited and unsafe available sight distances,using a driving simulator.We also considered curve road geometry(curve direction:rightward vs.leftward).Sixty active drivers were recruited for the study.While half of them(experimental group)tested the three V-ISA variants(and a V-ISA off condition),the other half always drove with the V-ISA off(validation group).We used a linear mixed-effect model to evaluate the influence of V-ISA on driver behaviour.All V-ISA variants were efficient at reducing speeds at entrance points,with no discernible negative impact on driver lateral behaviour.On rightward curves,the V-ISA intervening variant appeared to be the most effective at adapting to sight limitations.Results of the current study implies that V-ISA might assist drivers to adjust their operating speed as per prevailing sight conditions and,consequently,establishes safer driving conditions.
基金partially funded by the Department of Civil,Environmental,Architectural Engineering and Mathematics(DICATAM),University of Brescia,within the research grant“valuation of the risk of fare evasion in an urban public transport network”,CUP:D73C22000770002。
文摘Load limits,which appear to be routinely exceeded by trucks,occasionally result in road bridge failures.Therefore,predicting failures is crucial for safeguarding road safety.Past studies have largely focused on forecasting bridge failure event probability using the reliability analysis method,whilst occasionally accounting for vehicular overloading effects.Only recently,a study has investigated design traffic overloading event frequency using generalised linear regression models(GLRMs),including a power component and negative binomial regressions(NBRs).However,as far as the authors know,artificial neural network models(ANNMs)have never been applied to this field.This paper is an attempt to fill in these gaps.First a frequencybased metric of traffic overloading was adopted as a driver of failure probability.Second,two alternative‘frequency'models were specified,calibrated,and validated.The former was based on a GLRM,the latter on ANNMs.Then,these models were compared using regression plots(RPs),measures of errors(Mo Es)and the ratio between the number of observed vs predicted design load overcoming events to evaluate their performance.The models analysed more than 2 million weigh-in-motion(WIM)data records from a pilot station on a bridge on a heavily used ring road in Brescia(Italy).Results showed that ANNMs outperformed GLRMs.ANNMs have a higher correlation coefficient(between predicted and target frequencies),lower Mo Es,and a closer-to-unity ratio(between predicted and target frequencies).These findings may increase prediction accuracy of design traffic overloading events and give road authorities more effective traffic management to protect bridges from load hazards.
基金funded by the German Federal Ministry for Digital and Transport using resources from the National Cycling Plan 2020(NRVP)。
文摘In recent years,e-scooters have been introduced in many European cities.In several places we have witnessed a rapid uptake of this new mode of transport mainly as a result of public sharing schemes.A number of incidents,injuries and even fatalities have given rise to questions regarding the safety of these vehicles.These questions are being researched mainly using official crash data and data specifying injuries and hospital treatment.Until now,the research has focused on investigating typical injury patterns and estimating risk levels.Very little is known about exactly where conflicts and crashes occur.Knowledge of hazard hotspots is crucial when investigating risk levels and improving safety for all road users.Hence,this paper develops an approach to investigating locations with potentially dangerous interactions within the active mobility system in the city of Berlin.The approach consists of explorative expert interviews,an online poll,and quantitative analyses.For the latter we combine three datasets.First,we research crash hotspots using official data.Second,we use data based on acceleration sensors from cyclists'smartphones to find locations of sudden movements.Third,we use trip data from the operators of escooter sharing systems.The information gathered is used in a conclusive expert workshop to identify hazard hotspots.Results show that many of the conflicts with pedestrians are caused by parked escooters.Second,e-scooter trips are concentrated in the inner city and along specific routes.In moving traffic,various data sources are used to identify hotspots at intersections and in areas between intersections.The present research lays the foundation for important further studies to investigate interactions at hotspots in detail by determining nine specific locations in the city of Berlin.
基金the support received from the Science and Engineering Research Board,Government of India(grant number:SRG/2020/001128).
文摘Pedestrian safety is at high stakes due to the non-compliance practices of pedestrians at signalized intersections.Additionally,when pedestrians are hurrying,they deliberately engage in such unsafe behaviour.Therefore,the purpose of this study was to understand how time pressure(i.e.,feeling of hurry or saving time)affected pedestrians'decisions to follow traffic rules at signalized junctions.To achieve the study objectives,a pedestrian simulator setup was used to collect the crossing behaviour of forty participants at a four-legged signalized intersection.Non-compliance,one of the riskiest pedestrian behaviours,was examined with respect to three different forms,comprising dangerous temporal non-compliance(D-TNC),non-dangerous temporal non-compliance(ND-TNC),and spatial non-compliance(SNC)behaviour under two distinct conditions:baseline(i.e.,no time pressure)and time pressure conditions.The effects of demographics,usual walking features,and time pressure on D-TNC and ND-TNC were investigated using a multinomial regression model,while SNC behaviour was investigated using a binary regression model.It was interesting to note that the majority of the factors related to pedestrians’usual walking behaviour had an impact on all kinds of non-compliance behaviours.Importantly,the results also showcased that time pressure had a contrasting impact on D-TNC and ND-TNC behaviour whereas SNC behaviour increased under time pressure.Additionally,the varying impacts of D-TNC,ND-TNC,and SNC were also reflected in the occurrence of the crashes,which were probably triggered by discrepancies in the influence of time pressure on non-compliance behaviours.These findings highlight the need for technical solutions,educational outreach,and efficient enforcement practices to reduce pedestrians'non-compliant behaviour.
文摘One of the main factors affecting the safety of signalised intersections is the stop/go behaviour during the yellow interval.Although previous research has exhaustively examined drivers’stop/go decision-making,the expected autonomous vehicles’(AVs’)stop/go behaviour has not yet been thoroughly investigated.Through a series of simulation experiments developed for conventional and autonomous vehicles using different carfollowing,lane-changing,lateral placement and stop/go model parameter values,we examine here whether the default VISSIM stop/go parameter values can adequately replicate the observed drivers’behaviour at the considered intersection and assess the suitability of using the currently available options,albeit referring to human drivers,to simulate the expected stop/go behaviour of AVs.We also propose a policy framework for determining the desired behaviour of AVs in yellow interval,which is integrated into an AVs logic and achieved in the last simulation to explore the effect of automation on the stop/go outcome and,hence,on the safety level of signalised intersections.Several data analysis and modeling techniques were used for the formulation of certain scenarios,including binary choice models.The default stop/go parameter values were found unfit to replicate the observed stop/go behaviour and subjected to calibration.Compared to the currently available options,the proposed AVs logic proved to produce the most accurate results,in terms of the stop/go simulation outcome.Regarding the impact of automation on the stop/go outcome,the simulation experiments showed that AVs preferred a more conservative behaviour in favor of road safety,as indicated by the significant reduction(≈15%)in the number of vehicles crossing the stop line during the yellow light and zero instances of red light violation.However,compared to the conservative drivers represented by the default stop/go parameter values,AVs preferred a more rational behaviour in favor of intersection capacity without compromising road safety.
基金supported by the Innovation Capability Support Program of Shaanxi(No.2022TD-07)。
文摘This review evaluated research results on polyvinyl alcohol fiber cement-stabilized macadam(PVA-FCSM)to further improve the long-term durability of road structures and promote its in-depth study and high-quality application.The suitable PVA fiber technical indexes for ordinary cement-stabilized macadam(CSM)were recommended.The difference in the mechanical properties between CSM and PVA-FCSM was described.The extent to which PVA fibers enhance the durability of CSM were clarified.Additionally,the mechanism of enhancement of CSM by PVA fibers was revealed.Finally,the performance of each type of fiber cement-stabilized macadam(FCSM)was compared and evaluated.The results indicated that the suggested PVA fiber length and content for CSM were 12-30 mm and 0.6-1.2 kg/m^(3),respectively.At different ages,the mean degree of improvement in the unconfined compressive strength was 14%,20%,and 14%,that in the compressive resilience modulus was 8%,11%,and 6%,and that in the splitting strength was 29%,15%,and 22%,respectively.At different ages,the mean degree of decreased in the dry shrinkage coefficient was 21%,16%,and 15%and that in the temperature shrinkage coefficient(20℃-30℃)was 23%,23%,and 18%,respectively.The coefficients increased with extended curing age.Moreover,at the same stress level,PVA-FCSM has a higher fatigue life compared to CSM.The bridging effect,high strength,and high modulus of PVA fiber enhance the strength and anti-cracking of CSM.The recommended fiber type for CSM is PVA fiber.
基金support has been provided by the National Natural Science Foundation of China(No.52478125)Overseas Students Science and Technology Activities Project Merit Funding in Shaanxi Province(2021-11)the Fundamental Research Funds for the Central Universities,CHD(No.300102213207).
文摘Stress concentration factors(SCFs) for welded tubular joints can be decreased by filling the chord with concrete leading to a longer fatigue life. However, there are currently no design formula available in guidelines to predict the SCF of concrete-filled circular hollow section(CFCHS) K-joints, thus limiting their applicability in bridge design. To address this gap,finite element models for CFCHS K-joints were developed and compared against test results to ensure their accuracy. Then, a comprehensive parametric study was conducted to establish relationships between maximum SCFs and four variables: brace-to-chord diameter ratio(β), chord diameter-to-thickness ratio(2γ), brace-to-chord thickness ratio(τ), and the angle between braces and chord(θ). A total of 480 FE models were examined under three loading conditions including brace and chord loading: balanced axial force, chord axial force, and chord bending. Design equations to predict the maximum SCF for CFCHS Kjoints were established by multiple regression analyses of the numerical results. A comparison of maximum SCFs between circular hollow section(CHS) and CFCHS K-joints was made, and it was concluded that average reductions of 42% and 33% in maximum SCFs in CFCHS K-joints at the locations of the chord and brace were found compared to CHS joints for balanced axial force, respectively. Finally, a case study illustrating how to use the proposed equations for fatigue safety verification was presented.
基金supported by the U.S.Department of Energy,Office of Vehicle Technologies,under contract DE-AC02-06CH11357。
文摘This study proposes an approach of leveraging information gathered from multiple traffic data sources at different resolutions to obtain approximate inference on the traffic distribution of Chicago's O'Hare Airport area.Specifically,it proposes the ingestion of traffic datasets at different resolutions to build spatiotemporal models for predicting the distribution of traffic volume on the road network.Due to its good adaptability and flexibility for spatiotemporal data,the Gaussian process(GP)regression was employed to provide short-term forecasts using data collected by loop detectors(sensors)and supplemented by telematics data.The GP regression is used to make predictions of the distribution of the proportion of sensor data traffic volume represented by the telematics data for each location of the sensors.Consequently,the fitted GP model can be used to determine the approximate traffic distribution for a testing location outside of the training points.Policymakers in the transportation sector can find the results of this work helpful for making informed decisions relating to current and future transportation conditions in the area.
基金financially supported by the National Key R&D Program of China(No.2022YFB3706703)the National Natural Science Foundation of China(Nos.52078134 and 52378138)the Postgraduate Research&Practice Innovation Program of the Jiangsu Province of China(No.KYCX22_0220).
文摘Modern suspension bridges exhibit a trend of lighter structures,more diversified structural forms,and longer spans,the latter already exceeding two kilometers.Bridge performance under dead and live loads depends on their structural and main cable systems,while cablesupported bridges especially rely on the design analysis and construction control of the main cable.This literary survey systematically analyzes the research progress and state-ofthe-art status quo in the structural systems and design theories of suspension bridges,focusing on the structural systems,main cable shape analyses,live load effect analyses,and emerging lucrative research directions.More than 100 reliable references have been surveyed.(1)Multi-span or multi-main cable schemes appeal to increasing attention,which may become a better choice in terms of structural systems in scenarios with extremely long spans and heavy loads.The cable layouts,such as spatial main cables and hybrid cable-stayed suspension systems have also become feasible approaches for enhancing structural stiffness.(2)The shape-finding analysis during the construction phase is more complex and has more essential factors than that of the completed bridge state.Refined theories combining analytical methods and finite element methods are more suitable for the shape-finding analysis of complex cable systems than any single theory of the two,especially for novel cable systems.(3)The live load effect analysis methods based on traditional deflection theory or modified/improved deflection theories still have wide applications,but the refined theory of treating hangers as discrete members is also constantly developing,which is expected to provide new ideas for more complex structural analysis under the different types of live loads and their distribution forms.
基金supported by the National Key Research and Development Program of China(No.2021YFB1600300)。
文摘In the construction of the Shenzhen-Zhongshan Link,a temporary anchorage system,distributed uniformly along the pipe wall,has been employed.To assess the safety and reliability of this system,a combined method utilizing numerical analysis and model experiments was applied to study the safety of the temporary anchorage system and the reliability of the tension rods.Firstly,an overall model of the caisson segment based on GINA rebound force was established to analyze the stress state of the entire system.Secondly,a comprehensive numerical analysis and model experiment verification were conducted for the single tensioning system,revealing its failure mode and safety margin.The results indicate that the tension rod systems are uniformly stressed at an average of 444 k N during underwater jointing,with a safety factor of 1.94.At this point,the maximum von Mises stresses appearing at the front plate corners and the lower edge of the U-groove,with stress values of 181.8 MPa and 172.4 MPa,and safety factors of 1.54 and 1.71,respectively.When the tension rod force reaches 940 k N,the tensioning system reaches its bearing limit,with initial yielding occurring at the front plate corners.Model experiments were conducted to verify the theoretical analysis results,under a test load of 444 k N,the stresses at the front plate corners and the lower edge of the U-groove were 159.6 and 195.9 MPa,respectively.As the test load increased to 940 k N,these stresses reached 390 and 389 MPa,exhibiting good agreement with the numerical analysis.Considering the uncertainty of loads and materials,a reliability analysis of the tension rods was conducted,yielding a reliability index of 4.34,meeting the secondary safety standard.Based on the comprehensive analysis,it can be concluded that the temporary anchorage system in the caisson segments of the Shenzhen-Zhongshan Link exhibits excellent safety margins.
基金funded by the National Key Research and Development Program of China(grant No.2022YFB3706405)National Natural Science Foundation of China(grant Nos.52378316,52278318 and 52108176)+1 种基金National Key Research and Development Program of China(grant No.2021YFB1600300)List of Scientific and Technological Key Projects in Transportation Industry(grant No.2019-MS1-011)。
文摘Fatigue,corrosion,and bolt loosening are the main causes of structural performance degradation and collapse in steel bridges.Accurate monitoring of steel bridge diseases is a basic premise for ensuring high-quality operation and maintenance of steel bridges.In this regard,a summary and analysis were conducted on the classification of steel bridge diseases,monitoring and detection methods,application statuses,and major difficulties.The main causes,research status,and development trends of steel bridge diseases are discussed.The results showed that,for fatigue crack problems,fatigue crack initiation has a small scale,high difficulty in monitoring and detection,few methods,and low accuracy.As the cracks grow,the difficulty of monitoring and detection decreases,the number of methods increases,and the accuracy improves.Fatigue crack monitoring and detection are affected by the environmental and vehicular loads.Superficial corrosion features are evident in steel bridges,and corrosion identification methods and technologies are rapidly developing.Monitoring and detecting corrosion in concealed areas is difficult and requires further improvements in monitoring and detection technologies and their accuracy.Monitoring and detection methods and supporting equipment for bolt loosening in steel bridges are rapidly developing.The development of intelligent monitoring and detection technologies and supporting equipment is an important research topic that urgently needs to be addressed for the full-lifecycle operation and maintenance of steel bridges and the sustainable development of bridge engineering.Developing new intelligent sensing components based on high-performance materials and sensing element design theory to improve the monitoring and detection perception ability is an important development direction for steel bridge monitoring and detection.Research on intelligent monitoring and detection technologies,standardized indicators,and related topics based on intelligent operations and maintenance provide great support for the development of steel-bridge disease monitoring and detection.
基金supported by the Asian Smart Cities Research Innovation Network(grant 150-IIT K-LTU 202).
文摘The transport sector emits 18%of global CO_(2).Industry and consumers must adopt green mobility to reduce emissions and climate change.This will help achieve sustainability by improving efficiency and reducing greenhouse gas emissions.Thus,smart electric vehicles(SEVs)have emerged.Digital twins concept and technology may help launch SEVs to the market by analysing and optimising supporting infrastructure.This work aims to fill in the gaps between different pieces of research by giving a full review from a technical and scientifically neutral point of view.The study looks at how digital twin technology can be used in smart car systems by looking at its promise and the hurdles faced.Based on a comprehensive literature survey,this is the first in-depth look at how digital twin technology can be used in smart electric cars.The review has been organised into specific areas of the smart vehicle system,such as drive train system battery management system,driver assistance system,vehicle health monitoring system,vehicle power electronics.This review goes into detail about each component of the car to provide an overall view of the smart vehicle system as a whole.This review makes it easier to understand how digital twin technology can be utilized into each area from a scientific point of view.Lastly,the work looks at the technological and economic impact of digital twin technology,which will make considerable changes in car manufacturing processes,as well as help address current obstacles in utilizing advanced technologies.
