分离式套拱加固带裂缝衬砌的变形规律试验研究

文章基于1∶10的相似比制作拱顶带单条纵向裂缝且裂缝深度为原衬砌厚度1/3的隧道二次衬砌模型,采用弹簧模拟地层抗力,进行了分离式套拱加固衬砌(原衬砌与新增套拱之间增设防水板)的径向加载试验,得出了带裂缝衬砌经分离式套拱加固后的变形规律与破坏模式。结果表明,在松动荷载作用下,分离式套拱加固结构的受力过程分为"初期加载—预制裂缝径向贯通、预制裂缝径向贯通—套拱拱顶裂缝径向贯通、套拱拱顶裂缝径向贯通—试件破坏"三阶段,破坏荷载由原衬砌拱腰截面控制,关键部位破坏顺序为拱顶开裂—拱腰断裂—拱顶破坏,整体破坏性质为脆性破坏。     

搭载不同型号发动机的车身结构碰撞优化

同一车型搭载多种发动机是汽车常见的技术之一,但由于不同型号发动机在质量和体积上各异,会影响整车的碰撞性能.结合CAE有限元分析,利用LS-DYNA软件分别对4种结构优化设计方案碰撞结果进行验证.与采用加强纵梁后端或弱化纵梁前端等方案相比,采用优化上边梁方案在不对原车型做大改动的前提下,使汽车得到更好的碰撞性能,解决了由于发动机质量和体积增加所引起的车身碰撞安全问题,为后续类似问题提供了新的设计方法.     

高速公路新老路基相互作用分析与处理技术研究

利用弹塑性有限元的方法分析了在高速公路建设中路基加宽部分对原有路基竖向变形的特征,并对其原因展开了定性分析,最后提出了新老路基的衔接处理与纵向裂缝控制的措施。     

Changes to commute mode: The role of life events,spatial context and environmental attitude

It has been suggested that commuting behaviours become habitual and that changes to commute mode are more likely at the time of major life events. However, evidence to support this has so far been limited to analyses of small-scale samples. To address this evidence gap, we use two waves of panel data from the UK Household Longitudinal Study (2009/10 and 2010/11) to identify and explain the prevalence of individual change in commute mode from year to year amongst a representative sample of the English working population (n = 15,200). One third of those that cycle or get the bus to work, and one quarter of those that walk to work, are shown to change commuting mode by the following year. Car commuting is more stable, with only one in ten car commuters changing mode by the following year. Commute mode changes are found to be primarily driven by alterations to the distance to work which occur in association with changing job or moving home. Switching to non-car commuting becomes much more likely (9.2 times) as the distance to work drops below three miles. High quality public transport links to employment centres are shown to encourage switches away from car commuting and mixed land uses are shown to encourage switches to active commuting (walking and cycling). Switches away from car commuting are found to be more likely (1.3 times) for those with a pro-environmental attitude. The attitude orientation is shown to precede the behaviour change, demonstrating evidence of ‘cause and effect’. Overall, the study shows that changes in commuting behaviour are strongly influenced by life events, spatial context and environmental attitude.     

Evaluation of ultimate strength of stiffened panels under longitudinal thrust

A series of collapse analyses is performed applying nonlinear FEM on stiffened panels subjected to longitudinal thrust. MSC.Marc is used. Numbers, types and sizes of stiffeners are varied and so slenderness ratio as well as aspect ratio of local panels partitioned by stiffeners keeping the spacing between adjacent longitudinal stiffeners the same. Initial deflection of a thin-horse mode is imposed on local panels and that of flexural buckling and tripping modes on stiffeners to represent actual initial deflection in stiffened panels in ship structures. On the basis of the calculated results, buckling/plastic collapse behaviour of stiffened panels under longitudinal thrust is investigated. The calculated ultimate strength are compared with those obtained by applying several existing methods such as CSR for bulk carriers and PULS. Simple formulas for stiffened panels, of which collapse is dominated fundamentally by the collapse of local panels between longitudinal stiffeners, are also examined if they accurately estimate the ultimate strength. Through comparison of the estimated results with the FEM results, it has been concluded that PULS and modified FYH formulas fundamentally give good estimation of the ultimate strength of stiffened panels under longitudinal thrust.     

Reliability analysis of ship hulls made of composite materials under sagging moments

An approach is presented to assess the reliability of ship hulls made of composite materials under sagging moments. Buckling, first-ply failure, and ultimate collapse are regarded as the three possible failure modes of ship hulls of composite materials under sagging moments. Reliability estimates were carried out by a combination of the first-order second-moment method and the response surface methodology. A ship hull of composite materials under sagging moments was evaluated and the results showed that the effects on reliability estimates of the model uncertainty in the longitudinal strength of the ship hull, the model uncertainty of the sagging moments, and the sagging moments were significant, whereas the influences of the stochastic characteristics of material elastic moduli were relatively unimportant.     

基于响应面方法的车钩缓冲器特性曲线优化分析

为了更加真实地反映车钩缓冲器实际工作状态和进行缓冲器特性曲线优化,提出采用列车纵向动力学系统对缓冲器的特性曲线进行分析。在优化方面,从响应面方法的基本原理出发,建立响应面的子区域构造方法,运用凝聚函数和惩罚技术处理约束的遗传算法求解加约束条件的二次响应面最优解。以大秦线实际线路、列车编组以及列车纵向动力学性能为优化计算的条件,结合缓冲器数值模型建立缓冲器特性曲线的优化模型,运用所提出基于遗传算法的响应面方法对重载列车缓冲器特性曲线进行优化求解。结果说明所提方法对求解缓冲器特性曲线的优化问题非常有效。     

对教学秘书的"横向"与"纵向"协调功能的认识

教学秘书是教学管理和协调的重要环节,同时也是处于教学各种资源整合的最前沿。因此,该环节的作用能否得到充分的发挥和利用,影响到教学管理的质量和趋势。本文试从教学秘书所涉及的“横向”与“纵向”两个不同的角度和线路,结合自己几年来的工作实际和体会,对教学秘书的在教学资源整合、协调与发挥资源的最大优势方面作了一些分析和思考。     

长大坡道上梯形轨道稳定性研究

根据梯形轨道的结构特点,建立梯形轨道在长大坡道上的叠合梁计算模型。长大坡道上梯形轨道在制动力作用下其沿线路方向的荷载增加,垂向荷载相应减少,对梯形轨道纵向稳定性而言,是不利的。分析长大坡道上梯形轨道的纵向力传递机理,扣件的纵向阻力、凸挡台的抗剪强度、凸挡台侧壁缓冲垫的刚度是梯形轨道纵向力传递的控制因素。采取控制变量的方法,研究三者参数变化对轨道的内力和位移的影响。结果表明:在外在荷载作用下,长大坡道上梯形轨道钢轨爬行大于水平线路,凸挡台抗剪强度满足要求,并提供不同扣件纵向阻力和缓冲垫刚度对结构的影响。     

斜拉桥上无缝线路纵向相互作用理论及试验研究

运用梁轨纵向相互作用机理,建立斜拉桥上无缝线路纵向力计算模型,以一座铁路常用双塔钢桁斜拉桥为例,对斜拉桥上无缝线路纵向相互作用规律进行理论和试验研究。分析结果表明:在主桥左右两端各铺设一组单向伸缩调节器,主桥上钢轨纵向力可得到有效的控制,现场试验测试的桥面纵向位移及钢轨伸缩力分布规律与理论计算基本相同,所建立模型可用于斜拉桥上无缝线路纵向相互作用分析;钢轨挠曲力计算时,可在斜拉桥主跨及其邻跨上布置荷载,且不必考虑列车入桥方向的变化;钢轨伸缩调节器可有效减弱列车制动荷载下的梁轨相互约束作用,减小线路受力变形。