Analysis of cross effect on inherent deformation during the line heating process – Part 1 – Single crossed heating lines

This paper describes the effect of previous heating on inherent deformation by a subsequent heating line, more specifically, the case of two heating lines intersecting (crossing) each other. The paper has been divided into two parts. In the first part, the case of single crossed heating lines is studied in detail. The second part of the paper, discusses the case of more than one crossed heating lines. The novelty of the work lies in revealing the cross effect and how, factors such as, for example, the heating condition and the plate geometry, influence the resulting inherent deformation of crossed heating. In addition, relationships to easily get these influences are provided. The results are suitable for a wide range of heating conditions and plate thickness.     

横梁端部节点优化

通过有限元计算,对比几种常见的横梁端部连接方式,综合考虑结构整体强度、钢材使用量、舱室空间利用率、施工便利性等方面的影响因素,确定较优的连接过渡方式和过渡结构的参数尺寸,为船舶设计横梁端部节点形式的确定提供参考。     

Commuting and wellbeing: a critical overview of the literature with implications for policy and future research

ABSTRACT

This review provides a critical overview of what has been learnt about commuting’s impact on subjective wellbeing (SWB). It is structured around a conceptual model which assumes commuting can affect SWB over three time horizons: (i) during the journey; (ii) immediately after the journey; and (iii) over the longer term. Our assessment of the evidence shows that mood is lower during the commute than other daily activities and stress can be induced by congestion, crowding and unpredictability. People who walk or cycle to work are generally more satisfied with their commute than those who travel by car and especially those who use public transport. Satisfaction decreases with duration of commute, regardless of mode used, and increases when travelling with company. After the journey, evidence shows that the commute experience “spills over” into how people feel and perform at work and home. However, a consistent link between commuting and life satisfaction overall has not been established. The evidence suggests that commuters are generally successful in trading off the drawbacks of longer and more arduous commute journeys against the benefits they bring in relation to overall life satisfaction, but further research is required to understand the decision making involved. The evidence review points to six areas that warrant policy action and research: (i) enhancing the commute experience; (ii) increasing commute satisfaction; (iii) reducing the impacts of long duration commutes; (iv) meeting commuter preferences; (v) recognising flexibility and constraints in commuting routines and (vi) accounting for SWB impacts of commuting in policy making and appraisal.     

Assessment of fatigue strength of steel butt-welded joints in as-welded condition – Alternative approaches for curve fitting and mean stress effect analysis

Experimental fatigue data for butt-welded joints in as-welded condition and under constant amplitude tensile loading (secondary bending included) were analyzed using the nominal stress system and the notch stress system. Two approaches were used; a standard fitting procedure and minimization of the sum of squared perpendicular distances from a line with a fixed and free slope. In all cases, the latter method gave better agreement between the experimental and predicted fatigue life and fatigue strength. The analyses showed both with all broken specimen data included and with reduced data that the FAT225 curve, as recommended by IIW, might be too optimistic for the notch stress approach in the case of butt-welded joints in as-welded condition. It was also found that use of the local stress ratio instead of the applied stress ratio might explain many issues concerning current observations and apparent inconsistencies in reported literature.     

一种商用车铅酸蓄电池状态监控系统的开发

本文介绍一种商用车铅酸蓄电池状态监控系统的开发,系统实现蓄电池传感器实时采集蓄电池状态参数信息,并通过TBOX将数据上传至后台服务器,进行数据存储分析及报警判断,并将亏电报警信息推送给手机客户端,提醒用户注意。同时,系统根据蓄电池SOC值的限值判断,进行电磁开关的切断控制,以保证车辆的正常起动。     

Plate scanning tools to obtain travel times in traffic networks

The management of vehicle travel times has been shown to be fundamental to traffic network analysis. To collect travel time measurement, some methods focus solely on isolated links or highway segments, and where two measurement points, at the beginning and at the end of a section, are deemed sufficient to evaluate users' travel time. However, in many cases, transport studies involve networks in which the problem is more complex. This article takes advantage of the plate scanning technique to propose an algorithm that minimizes the required number of registering devices and their location in order to identify vehicles candidates to compute the travel times of a given set of routes (or subroutes). The merits of the proposed method are explained using simple examples and are illustrated by its application to the real network of Ciudad Real.     

Travel time estimation oriented freeway sensor placement problem considering sensor failure

Optimal sensor placement on freeway corridor is of great interest to transportation authorities. However, current traffic sensors are easily subject to various failures. Therefore, it is necessary to incorporate sensor failure into the optimal sensor placement model. In this article, a two-stage stochastic model is proposed for the purpose of travel time estimation on freeway corridor. To balance the effectiveness and reliability, a stochastic conditional value at risk (CVaR) model is also proposed. Since both models are too complicated, a customized genetic algorithm is developed. Numerical experiments show that considering sensor failure makes a significant performance improvement in the sensor placement pattern. Sensitivity analysis is also applied to investigate the impact of a number of allowable sensors and different traffic sensor failure probability.     

小直径盾构施工中管片纵向应力监测研究

为了探索小直径盾构法隧道在施工过程中管片纵向应力的变化规律,对北京槐房再生水厂污水隧道管片纵向应力进行了现场监测:将第976环、第1 054环管片分别设为第1和第2监测断面,2监测断面各预埋5个纵向应力计,各监测断面从本监测断面管片安装后即开始监测,当盾构掘进至第1 129环时停止监测。研究表明:1)在管片离开盾尾50环后,其纵向应力波动值小于管片拼装期间应力值的5%。2)在盾构掘进期间,管片距离盾构越远,其纵向压应力值越小。3)在管片拼装期间,管片距离盾构越远,其纵向压应力经历了先增大后减小的过程。4)管片距离盾构108环后,该管片纵向压应力趋近于0.2~0.3 MPa。5)随着盾构推进,管片纵向应力经历了4个阶段的变化过程,即周期性剧烈波动阶段—动态稳定阶段—逐渐衰减阶段—趋于稳定阶段。     

极高地应力软岩隧道超前导洞应力释放及多层支护变形控制技术

为了解决极高地应力软岩隧道大变形控制难题,以兰渝铁路木寨岭隧道岭脊核心段施工为例,通过现场试验和数据分析,得到如下主要结论:1)提出了"先放后抗,抗放结合,锚固加强"的变形控制理念;2)得出了该隧道岭脊核心段"超前导洞应力释放+圆形4层支护结构+径向注浆+长锚杆+长锚索"综合变形控制方案;3)超前导洞应力释放效果明显,正洞累计变形减小幅度约为34%;4)得到了圆形多层支护结构变形规律;5)累计变形均控制在设计预留变形量内,保证了该隧道岭脊核心段大变形控制效果。     

约束对隧道二次衬砌早期温度应力分布的影响

为了解决隧道工程渗水问题,基于某隧道工程,采用MIDAS-GEN对其二次衬砌早期模筑混凝土进行非稳定温度应力场以及周围约束进行研究。研究结果表明:约束可以改变隧道的早期拉应力场的分布,具有外围约束的隧道二次衬砌的拉应力为隧道厚度中间最大,无约束隧道的拉应力为外部最大,约束可以减小隧道外部区域的拉应力,使得远离约束区域的拉应力变大,而无约束隧道的拉应力分布与之相反。根据温度应力分布特点,建议在设计方面适当增大二次衬砌中间与外侧的配筋,在施工方面减小初期支护与二次砌衬之间约束等。