采用小阻力扣件的单线连续梁桥墩纵向刚度限值研究

基于梁轨相互作用原理,建立桥上无缝线路线桥墩一体化模型,研究主桥铺设小阻力扣件下单线连续梁桥墩纵向水平刚度的限值。研究结果表明:在主桥铺设小阻力扣件下,钢轨伸缩附加应力最大值与连续梁温度跨度及桥墩刚度近似呈线性关系;轨道结构稳定性和钢轨断缝对桥墩刚度限值均不起控制作用,桥墩刚度限值仅由钢轨强度控制;连续梁温度跨度较大时,桥墩刚度限值与温度跨度近似呈线性关系,对于温度跨度为240 m的连续梁,轨温变化幅度为50℃、40℃和30℃时,连续梁固定支座处桥墩刚度限值分别为1 282、522、226 k N/(cm·线)。     

CRTSⅠ型板式无砟轨道梁端凸形挡台纵向力分析

针对近几年大跨桥上CRTSⅠ型板式无砟轨道梁端半圆凸形挡台的剪切破坏现象,参考国内某连续刚构桥实际参数,根据桥梁梁端半圆形凸形挡台的配筋计算出凸形挡台的设计承载力,基于有限元方法,建立线-板-桥-墩一体化计算模型,计算分析在不同扣件阻力,桥梁温度跨度和桥墩线刚度等因素下的梁端半圆形凸形挡台受力。结果表明:扣件纵向阻力是梁端凸台剪切破坏的主要影响因素,随着扣件纵向阻力的增大,梁端半圆形凸形挡台所受纵向力也随之增大,当扣件纵向阻力达到17.0k N/m/轨时,凸形挡台所受纵向力将会超过凸形挡台的抗剪承载力,即发生破坏;桥梁温度跨度、桥墩线刚度、有无起制动力对梁端半圆形凸台所受纵向力影响很小。     

某大跨度钢桥纵向约束体系锚固结构设计与优化

大跨度钢桥常采用弹性索体系作为大桥的纵向约束,其锚固结构的局部应力较大、传力路径复杂,设计中需要针对其进行专门的计算分析,以保证锚固结构的可靠性。对某大跨度异型拱桥的弹性索锚固结构建立有限元模型,计算分析了钢锚箱结构在最大索力作用下各板件的应力分布。计算结果表明,钢锚箱在最大索力作用下各板件的各项应力值均满足规范要求,结构处于弹性工作状态。同时,针对钢锚箱各板件的布置情况进行优化计算分析,得到合理的锚箱加劲板布置形式。     

纵向轨枕式无砟轨道界面裂缝对轨道力学性能的影响

纵向轨枕轨道结构改用预制混凝土纵梁连续支撑的结构设计,故预制轨枕与道床板的新旧混凝土界面是结构稳定分析不可回避的因素。为了分析新旧混凝土界面对整体结构的影响,并为纵向轨枕式无砟轨道设计提供相关参考,通过建立纵向轨枕式无砟轨道的二维有限元计算模型进行研究。结果表明:纵向轨枕式无砟轨道在列车荷载和温度变化作用下,轨枕与道床板界面附近会出现纵向裂缝,并裂缝加快扩展。界面裂缝对轨道内部应力分布影响很大,对钢轨扭转有一定影响。     

Plastic mechanism analysis of structural performances for stiffeners on bottom longitudinal web girders during a shoal grounding accident

A theoretical model is introduced in this paper for structural performance of stiffeners on double-bottom longitudinal girders in a shoal grounding accident. Major emphasis is placed on establishing the characteristic deformation mechanism of stiffeners and identifying major energy dissipation patterns. Numerical simulations using the LS-DYNA nonlinear finite-element program were carried out to examine thoroughly the progressive deformation process during sliding deformation. Stiffener deformations were observed to fall into two categories: stiffeners fully contacted with the indenter, and stiffeners subjected to indirect deformation due to energy transfer from attached girders. Grounding performance of stiffeners is substantially influenced by that of the attached plating, and therefore a review of the existing deformation models of longitudinal girders (i.e. Simonsen 1997, Midtun 2006 and Hong 2008) was included. Hong's model of bottom girders was found not capable of representing the effects of stiffeners, and a new model of girders was thus developed. Based on observation of the numerical deformation process and the new analytical girder model, a kinematically admissible model of stiffeners on bottom longitudinal girders was built. Using the methods of plastic mechanism analysis, simplified analytical expressions for energy dissipation by girder-attached stiffeners, both fully contacted and noncontacted, were formulated, and equations for grounding resistance were subsequently obtained. The theoretical expressions agree favorably with results from nonlinear finite-element simulations and capture two significant characteristics of the problem: that energy varies little with indentation for stiffeners that fully contacting the indenter, and that energy is independent of slope angle for indirectly deformed stiffeners. The proposed theoretical model helps to predict analytically shoal grounding performance of stiffeners on longitudinal girders with reasonable accuracy.     

Statistical properties of bulk carrier longitudinal strength

The paper focuses on time-variant longitudinal strength of bulk carriers under corrosion wastage, applying both Taylor series expansion method and Monte Carlo simulation. Hull girder section modulus and ultimate bending moment capacity are determined, by classical beam theory and the commonly applied incremental-iterative approach, respectively. Two main aspects are fully discussed and investigated, according to the final recommendations of last ISSC Report. The former regards the covariance between annual corrosion rates of individual structural members, commonly assumed as uncorrelated. Really, as it is conceivable that a certain correlation exists, three different cases are investigated: uncorrelated variables, fully correlated variables, full correlation between structural members belonging to the same category of compartments. The latter investigates the probability density function of both hull girder section modulus and ultimate bending capacity, because the Central Limit Theorem cannot be applied when correlation among random variables exists. Finally, as a test example, the bulk carrier section, presented in the last ISSC benchmark study, is analysed.     

轻卡车架纵梁及车架总成性能研究

文章首先对通过对某轻卡车架进行模态分析,结果显示仿真与试验吻合,验证仿真模型准确;然后,对YC系列纵梁截面的车架总成进行对比分析并选出性能优越的方案,可为工程实践提供有效参考。     

手动变速器换挡过程纵向冲击问题研究

某款自主研发的匹配6MT手动变速器的国六SUV车型,在1挡加速过程中,松油门快踩离合器时,车辆产生明显的纵向冲击现象,且发生频率较高,严重影响了乘客地主观感受和乘车舒适性。通过对故障车辆进行实车诊断测试,对纵向冲击现象分析,发现发动机扭矩突变是导致整车产生纵向冲击的原因,最终通过优化发动机EMS标定策略的方法解决了该问题,以较低的成本达到了改善整合NVH性能的目的。     

城市轨道交通桥梁纵向制动力传递分析

以城市轨道交通桥梁为对象,分析制动力作用于轨道面上的传递过程。将轨道、扣件、桥跨结构、支座、墩身及基础划成有限元,建立平衡方程,分析当列车制动时,纵向力的传递与分配。由于无缝线路的联系作用,制动力将分配至较广范围,每一桥墩承受的最大制动荷载只相当于有缝线路制动力的39 6%～56 8%。制动过程中,纵向制动力对钢轨引起的应力不大。当采用扭矩为60N·m的扣件,墩身高度超过10m时,制动过程中局部区段的扣件可能出现滑动现象。     

无缝道岔受力与变形的影响因素分析

基于有限单元法,建立了无缝道岔纵向力与位移的计算模型,根据纵向力、线路阻力、钢轨及岔枕位移的相互关系建立平衡方程组,并采用牛顿迭代法求解。分析了轨温变化幅度、道岔号码、辙叉型式、辙跟型式、道岔群的联结方式、焊接型式、扣件阻力、道床阻力、限位器阻力、间隔铁阻力、线路爬行、铺设锁定轨温差、岔枕抗弯刚度等因素对无缝道岔受力及变形的影响。轨温变化幅度越大、线路爬行量越大、与相邻线路及道岔的铺设轨温差越大,对无缝道岔各部件的受力及变形越不利。而其它因素对无缝道岔位移及纵向力分布各有不同程度的影响,应综合分析,优化设计,才能确保无缝道岔各部件的受力及变形均在容许限度内。