To explore the load-bearing performance and the failure patterns of the lining structures,a full-scale loading test on the three-ring staggered assembled shield tunnel segments is carried out through a hydraulic loadi...To explore the load-bearing performance and the failure patterns of the lining structures,a full-scale loading test on the three-ring staggered assembled shield tunnel segments is carried out through a hydraulic loading system.In the experimental study,the segments"internal force,convergence deformation,and displacement,and the bolts'internal force,are analyzed.According to the experimental results,the relationship between internal force and deformation is obtained to determine the residual bearing capacity of the shield tunnel at each stage.Three stages are specified for the evolution of the segment's maximum bending moment during the loading process,in which,the elastic stage is the main and longest stage,in which the bending moment of the segment increases the most.There are two stages for convergence deformation development and segment misalignment development.At the end of loading,the segment's maxi-mum positive and negative convergence values reach 61.22 and-57.69 mm,respectively.Besides,the maximum segment misalignment is 3.67 mm,which occurs in the direction of 90°.The segment cracks when its maximum convergence value reaches 25.03 mm.Moreover,there are signs of fracturing on the waist joint of the segment when its maximum convergence value reaches 32.73 mm.The concrete at the waist joint starts fracturing in pieces when the segment's maximum convergence value reaches 38.93 mm,which is defined as the type of shear failure.Finally,the bearing capacity of shield tunnels during segment failure period can be evaluated by using the corresponding relationship between deformation and internal force.展开更多
Free piston linear generator(FPLG)is a promising range extender for the electrical vehicle with unparallel advantages,such as compact structure,higher system efficiency,and reduced maintenance cost.However,due to the ...Free piston linear generator(FPLG)is a promising range extender for the electrical vehicle with unparallel advantages,such as compact structure,higher system efficiency,and reduced maintenance cost.However,due to the lack of the mechanic crankshaft,the related piston motion control is a challenge for the FPLG which causes problems such as misfire and crash and limits its widespread commercialization.Aimed at resolving the problems as misfire,a single-piston FPLG prototype has been designed and manufactured at Shanghai Jiao Tong University(SJTU).In this paper,the development process and experimental validation of the related control strategies were detailed.From the experimental studies,significant misfires were observed at first,while the FPLG operated in natural-aspiration conditions.The root cause of this misfire was then identified as the poor scavenging process,and a compressed air source was leveraged to enhance the related scavenging pressure.Afterward,optimal control parameters,in terms of scavenging pressure,air-fuel equivalence ratio,and ignition position,were then calibrated in this charged-scavenging condition.Eventually,the FPLG prototype has achieved a continuous stable operation of over 1000 cycles with an ignition rate of 100%and a cycle-to-cycle variation of less than 0.8%,produced an indicated power of 2.8 kW with an indicated thermal efficiency of 26%and an electrical power of 2.5 kW with an overall efficiency of 23.2%.展开更多
基金supported by the General Scientific Research Projects for Agriculture and Social Development in Hangzhou,China(Grant No.20201203B127)the National Natural Science Foundation of China(Grant No.51778576)the Basic Public Welfare Research Projects in Zhejiang Province,China(Grant No.LGF22E080012)。
文摘To explore the load-bearing performance and the failure patterns of the lining structures,a full-scale loading test on the three-ring staggered assembled shield tunnel segments is carried out through a hydraulic loading system.In the experimental study,the segments"internal force,convergence deformation,and displacement,and the bolts'internal force,are analyzed.According to the experimental results,the relationship between internal force and deformation is obtained to determine the residual bearing capacity of the shield tunnel at each stage.Three stages are specified for the evolution of the segment's maximum bending moment during the loading process,in which,the elastic stage is the main and longest stage,in which the bending moment of the segment increases the most.There are two stages for convergence deformation development and segment misalignment development.At the end of loading,the segment's maxi-mum positive and negative convergence values reach 61.22 and-57.69 mm,respectively.Besides,the maximum segment misalignment is 3.67 mm,which occurs in the direction of 90°.The segment cracks when its maximum convergence value reaches 25.03 mm.Moreover,there are signs of fracturing on the waist joint of the segment when its maximum convergence value reaches 32.73 mm.The concrete at the waist joint starts fracturing in pieces when the segment's maximum convergence value reaches 38.93 mm,which is defined as the type of shear failure.Finally,the bearing capacity of shield tunnels during segment failure period can be evaluated by using the corresponding relationship between deformation and internal force.
基金supported by the project of Shanghai Science and Technology Commission(No.19511108500).
文摘Free piston linear generator(FPLG)is a promising range extender for the electrical vehicle with unparallel advantages,such as compact structure,higher system efficiency,and reduced maintenance cost.However,due to the lack of the mechanic crankshaft,the related piston motion control is a challenge for the FPLG which causes problems such as misfire and crash and limits its widespread commercialization.Aimed at resolving the problems as misfire,a single-piston FPLG prototype has been designed and manufactured at Shanghai Jiao Tong University(SJTU).In this paper,the development process and experimental validation of the related control strategies were detailed.From the experimental studies,significant misfires were observed at first,while the FPLG operated in natural-aspiration conditions.The root cause of this misfire was then identified as the poor scavenging process,and a compressed air source was leveraged to enhance the related scavenging pressure.Afterward,optimal control parameters,in terms of scavenging pressure,air-fuel equivalence ratio,and ignition position,were then calibrated in this charged-scavenging condition.Eventually,the FPLG prototype has achieved a continuous stable operation of over 1000 cycles with an ignition rate of 100%and a cycle-to-cycle variation of less than 0.8%,produced an indicated power of 2.8 kW with an indicated thermal efficiency of 26%and an electrical power of 2.5 kW with an overall efficiency of 23.2%.
