This study focuses on the bending failure performance of a shield tunnel segment.A full-scale test was conducted to investigate deformation and failure characteristics.During the loading,the bending failure process ca...This study focuses on the bending failure performance of a shield tunnel segment.A full-scale test was conducted to investigate deformation and failure characteristics.During the loading,the bending failure process can be divided into four stages:the elastic stage,working stage with cracks,failure stage,and ultimate stage.The characteristic loads between contiguous stages are the cracking,failure,and ultimate loads.A numerical model corresponding to the test was established using the elastoplastic damage constitutive model of concrete.After a comparative analysis of the simulation and test results,parametric studies were performed to discuss the influence of the reinforcement ratio and proportion of tensile longitudinal reinforcement on the bearing capacity.The results indicated that the change in the reinforcement ratio and the proportion of tensile longitudinal reinforcement had little effect on the cracking load but significantly influenced the failure and ultimate loads of the segment.It is suggested that in the reinforcement design of the subway segment,the reinforcement ratio and the proportion of tensile longitudinal reinforcement can be chosen in the range of 0.7%–1.2%and 49%–55%,respectively,allowing the segment to effectively use the reinforcement and exert the design strength,thereby improving the bearing capacity of the segment.展开更多
采用fib Model Code 2010中纤维对受弯承载力贡献的作用方式,并结合GB 50010—2010《混凝土结构设计规范》中偏心受压构件正截面受力分析,提出了不对称配筋纤维混凝土盾构管片配筋计算方法。以国内某地铁工程管片配筋计算为例,采用该方...采用fib Model Code 2010中纤维对受弯承载力贡献的作用方式,并结合GB 50010—2010《混凝土结构设计规范》中偏心受压构件正截面受力分析,提出了不对称配筋纤维混凝土盾构管片配筋计算方法。以国内某地铁工程管片配筋计算为例,采用该方法计算了纤维混凝土管片正截面配筋并与普通混凝土管片配筋进行对比。同时,计算分析了采用不同等级纤维混凝土时该管片正截面配筋的变化规律。结果表明,纤维的加入可以降低钢筋用量,该方法结合了欧洲规范和国内的钢筋混凝土设计规范,具有较高的可靠性,可用于纤维混凝土盾构隧道管片设计。展开更多
The emergence of Segment Routing(SR)provides a novel routing paradigm that uses a routing technique called source packet routing.In SR architecture,the paths that the packets choose to route on are indicated at the in...The emergence of Segment Routing(SR)provides a novel routing paradigm that uses a routing technique called source packet routing.In SR architecture,the paths that the packets choose to route on are indicated at the ingress router.Compared with shortest-path-based routing in traditional distributed routing protocols,SR can realize a flexible routing by implementing an arbitrary flow splitting at the ingress router.Despite the advantages of SR,it may be difficult to update the existing IP network to a full SR deployed network,for economical and technical reasons.Updating partial of the traditional IP network to the SR network,thus forming a hybrid SR network,is a preferable choice.For the traffic is dynamically changing in a daily time,in this paper,we propose a Weight Adjustment algorithm WASAR to optimize routing in a dynamic hybrid SR network.WASAR algorithm can be divided into three steps:firstly,representative Traffic Matrices(TMs)and the expected TM are obtained from the historical TMs through ultrascalable spectral clustering algorithm.Secondly,given the network topology,the initial network weight setting and the expected TM,we can realize the link weight optimization and SR node deployment optimization through a Deep Reinforcement Learning(DRL)algorithm.Thirdly,we optimize the flow splitting ratios of SR nodes in a centralized online manner under dynamic traffic demands,in order to improve the network performance.In the evaluation,we exploit historical TMs to test the performance of the obtained routing configuration in WASAR.The extensive experimental results validate that our proposed WASAR algorithm has superior performance in reducing Maximum Link Utilization(MLU)under the dynamic traffic.展开更多
采用混凝土Rankine-Plasticity植入式钢筋模型,就配筋率对管片承载性能的影响进行了研究,研究表明:(1)植入式钢筋方法可较好地捕捉管片加载全程中的混凝土开裂、钢筋屈服、混凝土压碎等关键特征;(2)配筋率在0.29%~1.6%范围变化时,配筋...采用混凝土Rankine-Plasticity植入式钢筋模型,就配筋率对管片承载性能的影响进行了研究,研究表明:(1)植入式钢筋方法可较好地捕捉管片加载全程中的混凝土开裂、钢筋屈服、混凝土压碎等关键特征;(2)配筋率在0.29%~1.6%范围变化时,配筋率对管片屈服弯矩影响较显著,配筋率每增加1‰,屈服弯矩增加50~60 k N·m;屈服弯矩增加幅度随着配筋率增大而逐渐减小并趋于稳定;(3)管片轴力、混凝土抗压强度、钢筋等级等是控制配筋率对管片承载能力影响程度的重要因素,轴力增大、混凝土和钢筋强度降低等会弱化配筋率对管片承载力的影响;(4)配筋率对整环承载能力的影响要弱于其对管片承载性能的影响。展开更多
基金the financial support provided by the National Natural Science Foundation of China(Grant Nos.51978019 and 52278382)the Beijing Natural Science Foundation(No.8222004).
文摘This study focuses on the bending failure performance of a shield tunnel segment.A full-scale test was conducted to investigate deformation and failure characteristics.During the loading,the bending failure process can be divided into four stages:the elastic stage,working stage with cracks,failure stage,and ultimate stage.The characteristic loads between contiguous stages are the cracking,failure,and ultimate loads.A numerical model corresponding to the test was established using the elastoplastic damage constitutive model of concrete.After a comparative analysis of the simulation and test results,parametric studies were performed to discuss the influence of the reinforcement ratio and proportion of tensile longitudinal reinforcement on the bearing capacity.The results indicated that the change in the reinforcement ratio and the proportion of tensile longitudinal reinforcement had little effect on the cracking load but significantly influenced the failure and ultimate loads of the segment.It is suggested that in the reinforcement design of the subway segment,the reinforcement ratio and the proportion of tensile longitudinal reinforcement can be chosen in the range of 0.7%–1.2%and 49%–55%,respectively,allowing the segment to effectively use the reinforcement and exert the design strength,thereby improving the bearing capacity of the segment.
文摘采用fib Model Code 2010中纤维对受弯承载力贡献的作用方式,并结合GB 50010—2010《混凝土结构设计规范》中偏心受压构件正截面受力分析,提出了不对称配筋纤维混凝土盾构管片配筋计算方法。以国内某地铁工程管片配筋计算为例,采用该方法计算了纤维混凝土管片正截面配筋并与普通混凝土管片配筋进行对比。同时,计算分析了采用不同等级纤维混凝土时该管片正截面配筋的变化规律。结果表明,纤维的加入可以降低钢筋用量,该方法结合了欧洲规范和国内的钢筋混凝土设计规范,具有较高的可靠性,可用于纤维混凝土盾构隧道管片设计。
基金supported by the MSIT(Ministry of Science,ICT),Korea,under the ITRC(Information Technology Research Center)support program(IITP-2020-2016-0-00465)supervised by the IITP(Institute for Information&Communications Technology Planning&Evaluation).
文摘The emergence of Segment Routing(SR)provides a novel routing paradigm that uses a routing technique called source packet routing.In SR architecture,the paths that the packets choose to route on are indicated at the ingress router.Compared with shortest-path-based routing in traditional distributed routing protocols,SR can realize a flexible routing by implementing an arbitrary flow splitting at the ingress router.Despite the advantages of SR,it may be difficult to update the existing IP network to a full SR deployed network,for economical and technical reasons.Updating partial of the traditional IP network to the SR network,thus forming a hybrid SR network,is a preferable choice.For the traffic is dynamically changing in a daily time,in this paper,we propose a Weight Adjustment algorithm WASAR to optimize routing in a dynamic hybrid SR network.WASAR algorithm can be divided into three steps:firstly,representative Traffic Matrices(TMs)and the expected TM are obtained from the historical TMs through ultrascalable spectral clustering algorithm.Secondly,given the network topology,the initial network weight setting and the expected TM,we can realize the link weight optimization and SR node deployment optimization through a Deep Reinforcement Learning(DRL)algorithm.Thirdly,we optimize the flow splitting ratios of SR nodes in a centralized online manner under dynamic traffic demands,in order to improve the network performance.In the evaluation,we exploit historical TMs to test the performance of the obtained routing configuration in WASAR.The extensive experimental results validate that our proposed WASAR algorithm has superior performance in reducing Maximum Link Utilization(MLU)under the dynamic traffic.
文摘采用混凝土Rankine-Plasticity植入式钢筋模型,就配筋率对管片承载性能的影响进行了研究,研究表明:(1)植入式钢筋方法可较好地捕捉管片加载全程中的混凝土开裂、钢筋屈服、混凝土压碎等关键特征;(2)配筋率在0.29%~1.6%范围变化时,配筋率对管片屈服弯矩影响较显著,配筋率每增加1‰,屈服弯矩增加50~60 k N·m;屈服弯矩增加幅度随着配筋率增大而逐渐减小并趋于稳定;(3)管片轴力、混凝土抗压强度、钢筋等级等是控制配筋率对管片承载能力影响程度的重要因素,轴力增大、混凝土和钢筋强度降低等会弱化配筋率对管片承载力的影响;(4)配筋率对整环承载能力的影响要弱于其对管片承载性能的影响。
