Steel and ultra⁃high performance concrete(UHPC)composite decks are effective at reducing fatigue cracking and asphalt pavement damage.The shear behavior of innovative open steel tube(OST)connectors in steel⁃UHPC compo...Steel and ultra⁃high performance concrete(UHPC)composite decks are effective at reducing fatigue cracking and asphalt pavement damage.The shear behavior of innovative open steel tube(OST)connectors in steel⁃UHPC composite decks was investigated by conducting push⁃out tests.The test parameter is the presence of reinforcement in the deck.The load⁃slip curves and shear behavior of the push⁃out specimens were obtained and discussed.The test results indicate that as compared with plain concrete specimens,the limit slip of reinforced specimens decreased by 32%and the shear stiffness increased by 10%,but the ultimate shear capacity was almost the same.The use of UHPC influenced the failure process as it was observed that the OST connector was sheared off at its lower semi⁃tube,followed by the pull⁃out failure of the upper semi⁃tube.A finite element model was verified by tests and was then used to analyze the deformation and failure behaviors of the composite deck with open tubes.The model demonstrates that there is a stress concentration zone at the connector root,and the lower semi⁃tube is the main component that is subject to loads.展开更多
On-ramp control is an effective approach for alleviating traffic congestion on highways.However,there is still a lack of on-ramp control approaches applicable to large regional highway networks.Here,we develop a targe...On-ramp control is an effective approach for alleviating traffic congestion on highways.However,there is still a lack of on-ramp control approaches applicable to large regional highway networks.Here,we develop a targeted on-ramp control approach applicable to regional highway networks by taking advantage of the vehicle source information,which pinpoints the on-ramps contributing major traffic flow to the highway bottleneck.Furthermore,a combined and tunable controlling index is proposed to enhance the equity of the generated traffic control scheme.The proposed on-ramp control approach is validated on an actual large highway network using actual travel demand data.Results indicate that the proposed approach can well mitigate the traffic congestion of highway bottleneck while at the same time enhancing the equity and practicability of the generated traffic control scheme.展开更多
Bus reliability has long attracted attention and been extensively studied to enhance service quality.However,existing research generally evaluates bus reliability of specific routes or stops.To this end,this study exp...Bus reliability has long attracted attention and been extensively studied to enhance service quality.However,existing research generally evaluates bus reliability of specific routes or stops.To this end,this study explores en-route bus reliability with real-time data at network scale.Drawing on data of bus automatic vehicle location and smart card usage in Ningbo,China,this study calculates headway-based reliability with the difference between actual and scheduled headway at each stop.To demonstrate the trend of stop-level reliability along a bus route,reliability is graded and visualized on a map with ridership at each stop,which is then weighted with passenger-boarding volume.Route-level reliability is then quantified and mapped,where unreliable service basically concentrates in or extends through the centre area.With respect to network-level reliability,temporal changes are demonstrated with ridership on weekdays and at the weekend.It is observed that on weekdays,the reliability trend is similar to that of ridership,implying a causal relationship between bus travel-time variation and bus waiting-time at stops.Furthermore,a reliability comparison between weekdays in December and October shows the necessity of evaluating periodically and around important events to avoid negative riding experiences that discourage public transport usage.This research provides insights for bus agencies to systematically evaluate service reliability both spatially and temporarily,in order to identify and prioritize the routes and stops where the scope for reliability improvement and the expected benefit are greatest.展开更多
基金Sponsored by the National Natural Science Foundation of China(Grant No.51478120)。
文摘Steel and ultra⁃high performance concrete(UHPC)composite decks are effective at reducing fatigue cracking and asphalt pavement damage.The shear behavior of innovative open steel tube(OST)connectors in steel⁃UHPC composite decks was investigated by conducting push⁃out tests.The test parameter is the presence of reinforcement in the deck.The load⁃slip curves and shear behavior of the push⁃out specimens were obtained and discussed.The test results indicate that as compared with plain concrete specimens,the limit slip of reinforced specimens decreased by 32%and the shear stiffness increased by 10%,but the ultimate shear capacity was almost the same.The use of UHPC influenced the failure process as it was observed that the OST connector was sheared off at its lower semi⁃tube,followed by the pull⁃out failure of the upper semi⁃tube.A finite element model was verified by tests and was then used to analyze the deformation and failure behaviors of the composite deck with open tubes.The model demonstrates that there is a stress concentration zone at the connector root,and the lower semi⁃tube is the main component that is subject to loads.
基金Project(52178443)supported by the National Natural Science Foundation of ChinaProject(2019YFC1904704)supported by the National Key R&D Program of China+1 种基金Project(2022YJ120)supported by the Key R&D Program of Chinese Academy of Railway SciencesProjects(2022JZZ03,2021JZZ01,2021JZZ02)supported by the Open Foundation of Key Laboratory of Engineering Structures of Heavy Haul Railway of Ministry of Education,China。
基金supported by the Hunan Provincial Natural Science Fund for Distinguished Young Scholars(No.2022JJ10077)the 2021 Science and Technology Progress and Innovation Plan of Department of Transportation of Hunan Province(No.202102).
文摘On-ramp control is an effective approach for alleviating traffic congestion on highways.However,there is still a lack of on-ramp control approaches applicable to large regional highway networks.Here,we develop a targeted on-ramp control approach applicable to regional highway networks by taking advantage of the vehicle source information,which pinpoints the on-ramps contributing major traffic flow to the highway bottleneck.Furthermore,a combined and tunable controlling index is proposed to enhance the equity of the generated traffic control scheme.The proposed on-ramp control approach is validated on an actual large highway network using actual travel demand data.Results indicate that the proposed approach can well mitigate the traffic congestion of highway bottleneck while at the same time enhancing the equity and practicability of the generated traffic control scheme.
文摘Bus reliability has long attracted attention and been extensively studied to enhance service quality.However,existing research generally evaluates bus reliability of specific routes or stops.To this end,this study explores en-route bus reliability with real-time data at network scale.Drawing on data of bus automatic vehicle location and smart card usage in Ningbo,China,this study calculates headway-based reliability with the difference between actual and scheduled headway at each stop.To demonstrate the trend of stop-level reliability along a bus route,reliability is graded and visualized on a map with ridership at each stop,which is then weighted with passenger-boarding volume.Route-level reliability is then quantified and mapped,where unreliable service basically concentrates in or extends through the centre area.With respect to network-level reliability,temporal changes are demonstrated with ridership on weekdays and at the weekend.It is observed that on weekdays,the reliability trend is similar to that of ridership,implying a causal relationship between bus travel-time variation and bus waiting-time at stops.Furthermore,a reliability comparison between weekdays in December and October shows the necessity of evaluating periodically and around important events to avoid negative riding experiences that discourage public transport usage.This research provides insights for bus agencies to systematically evaluate service reliability both spatially and temporarily,in order to identify and prioritize the routes and stops where the scope for reliability improvement and the expected benefit are greatest.
