无砟轨道桩板结构路基设计计算

鉴于无砟轨道桩板结构路基没有相应的设计规范,在分析其结构特点和使用要求的基础上,借鉴相关行业标准和研究成果,将荷载分为永久荷载、可变荷载和偶然荷载,提出按承载能力极限状态和正常使用极限状态分别进行荷载效应组合,取各自的最不利组合以分项系数形式的表达式进行桩板结构路基设计计算。对荷载分项系数、组合值系数、准永久值系数以及结构抗力设计值和正常使用规定限值提出建议值。建议:承载板长度宜取20~50 m、厚度宜取0.5~0.8 m,并按一定原则设置;桩间距纵向宜取5~10 m,横向宜与线间距相对应;设置过渡段以满足过渡衔接处差异沉降和竖向转角要求。     

关于"载重线公约-附则I修正案"生效

国际载重线公约-附则I的修正案,是"国际载重线公约"自1966年4月5日(在伦敦1966年国际载重线公约缔约)以来较大的一次修订,"修正案"的生效和施行将对船舶、海上财产以及船上人命安全等方面产生重大影响.该文基于作者对规范的理解并结合了一定的案例分析,以期裨益读者.     

全电力船舶的电力推进系统建模与仿真

本文介绍了全电力船舶的典型推进系统并给出了仿真结果。由于模型的复杂性,仿真计算的工程量非常巨大。因此设计了一个可供替代的简化仿真系统。从船舶网络的角度来看,简化系统的仿真结果和实际模型的结果十分接近。     

Design research of gravity retaining wall based on limit state design methodEI北大核心

Research purposes: Gravity retaining wall limit state design research is based on the design research of retaining structure limit state of open-cut foundation with the lateral earth pressure supported by wall body weight. This paper sums up the research thought of gravity retaining wall and analyzed their main calculation results, which provides reference for the open-cut foundation retaining structure design research of cantilever retaining wall, counterfort retaining wall, groove type retaining wall and so on. Research conclusions: (1) The steps for design research of the gravity retaining wall limit state are to establish a limit state equation, to calculate reliability index and determine the target reliability index, calculate partial coefficient and set up the design expression. (2) The most critical factor influencing gravity retaining wall limit state is comprehensive internal friction angle. (3) There are different function calculations and different design conditions for the gravity retaining wall in the current specification, their underlying reliability index is different, the corresponding partial coefficient should also be different. (4) The research conclusion can be used to guide the design of gravity retaining wall, which provides the reference to the design research of other open-cut foundation retaining structure.     

公路旧桥车辆通行能力的荷载试验验证

某跨江公路大桥引桥40m简支预应力混凝土小箱梁,运营过程中出现腹板超宽斜裂缝、横隔板断裂等病害,通过静荷载试验与理论分析,评价桥跨实际承载能力,为同类工程试验研究及设计提供一些参考.     

低路堤荷载作用下钢波纹管涵切向应变现场测试

为研究钢波纹管涵在低路堤荷载作用下的力学性能,依托泗许高速安徽淮北段一处试验涵,对荷载分别作用于超车道、行车道、应急车道情况下管涵的切向应变进行现场测试。试验数据表明：当荷载作用于不同车道时,钢波纹管切向应变不同,随着荷载的移动,波纹管不同断面同一角度的切向应变值不同但变化规律相似。试验结果可以为今后的钢波纹管涵洞设计和施工提供理论依据。     

桩自平衡测试技术及其在桥梁工程中的应用

结合杭州湾跨海大桥的工程实例对桩自平衡测试技术的原理、应用以及测试过程中的施工注意事项作了综合的介绍.     

High speed tensile test of steel sheets for the stress-strain curve at the intermediate strain rate

This paper presents stress-strain curves of steel sheets for an auto-body obtained at intermediate strain rates with a servo-hydraulic type high speed tensile testing machine. The apparatus has the maximum stroke velocity of 7.8 m/sec to obtain the tensile material properties at a strain rate of up to 500/sec. A special jig fixture is specially designed for accurate acquisition of tensile loads with reduction of the load-ringing phenomenon induced by unstable stress wave propagation at high strain rates. Tensile testing of steel sheets for an auto-body was carried out to obtain stress-strain curves of mild steel and advanced high strength steels at strain rates ranged from 1/sec to 200/sec. The test results provide interesting information regarding the stress-strain curves at intermediate strain rates ranged from 1/sec to 200/sec and demonstrate that strain rate hardening is strongly coupled with strain hardening.     

测试应力腐蚀临界应力强度因子的新方法

应力腐蚀临界应力强度因子的测试方法是基于线弹性继裂力学理论和应力腐蚀理论提出的一种新的测试方法。该方法采用精密电子元件测试所需应力值,并利用显微镜测得的直径,通过计算便可获得应力腐蚀临界应力强度因子值。实践表明：该方法具有操作简单、应用灵活、成本低等优点。     

Norm approximation method for handling traffic count inconsistencies in path flow estimator

Path flow estimator (PFE) is a one-stage network observer proposed to estimate path flows and hence origin–destination (O–D) flows from traffic counts in a transportation network. Although PFE does not require traffic counts to be collected on all network links when inferring unmeasured traffic conditions, it does require all available counts to be reasonably consistent. This requirement is difficult to fulfill in practice due to errors inherited in data collection and processing. The original PFE model handles this issue by relaxing the requirement of perfect replication of traffic counts through the specification of error bounds. This method enhances the flexibility of PFE by allowing the incorporation of local knowledge, regarding the traffic conditions and the nature of traffic data, into the estimation process. However, specifying appropriate error bounds for all observed links in real networks turns out to be a difficult and time-consuming task. In addition, improper specification of the error bounds could lead to a biased estimation of total travel demand in the network. This paper therefore proposes the norm approximation method capable of internally handling inconsistent traffic counts in PFE. Specifically, three norm approximation criteria are adopted to formulate three L_p-PFE models for estimating consistent path flows and O–D flows that simultaneously minimize the deviation between the estimated and observed link volumes. A partial linearization algorithm embedded with an iterative balancing scheme and a column generation procedure is developed to solve the three L_p-PFE models. In addition, the proposed L_p-PFE models are illustrated with numerical examples and the characteristics of solutions obtained by these models are discussed.