蛇行波长取值方式对钢板梁桥横向振动的影响

随着我国既有线路的大规模提速,铁路货车提速后上承式钢板梁桥横向振幅超限现象日益突出,严重影响货车进一步提速.以轮对随机人工蛇行波为激励,就不同的蛇行波长取值方式对铁路钢板梁桥横向振动的影响进行了探讨.最后指出,20辆车各个轮对蛇行波波长均不同、轮对蛇行波波长随机选取时各速度对应的桥梁横向最大位移小于轮对蛇行波波长均相同时相应速度对应的桥梁横向最大位移值.     

普速铁路下承式大跨简支钢梁桥动载试验研究

通过在既有普速铁路下承式大跨简支钢梁桥的动载试验,得到其在不同速度试验列车作用下,梁体跨中截面动力变化及跨中挠度变化情况、桥墩和梁体的横向振动情况。试验研究结果表明:钢桁梁、钢板梁横向自振频率、振幅满足规范要求,钢板梁横向加速度不满足要求; 3号、4号墩墩顶横向振幅满足规范要求,横向自振频率不满足要求。建议定期对3号、4号墩进行横向振幅自振测试。     

上承式钢板梁横向振动控制的试验研究

随着列车速度的提高 ,上承式钢板梁横向振幅过大的问题日益突出 ,它直接威胁行车安全。提出用粘弹性阻尼器控制上承式钢板梁的横向振动 ,并在京广上行线羊楼司桥上进行现场试验。结果表明 ,粘弹性阻尼器能有效地减小上承式钢板梁的横向振幅 ,为进一步选择合适的粘弹性材料提供了试验依据。     

货运铁路扩能运输对桥梁动力性能的影响

随着铁路扩能运输的快速推进,列车编组增加、车辆轴重增大、运营密度提高,使得铁路桥梁承受的荷载与疲劳效应显著增加。为了分析重载运输对朔黄铁路桥梁运营性能的影响,文章通过对朔黄铁路7座桥梁进行运营性能相关试验,分析运营荷载作用下结构的动力系数、梁跨跨中振幅、横向加速度和梁跨自振频率等动态性能指标以及试验梁跨两端桥墩的墩顶振幅等参数变化规律,结合梁跨横向刚度等运营性能指标,分析不同车辆类型对桥梁结构动力性能的影响,为管理部门系统掌握该桥的技术状态、制定运行方案和养护维修提供技术依据。     

铁路提速工程T形简支梁横向加固设计

兰新线武嘉段电气化提速工程中,大量既有铁路混凝土梁存在横向振幅超限的问题。结合武嘉段提速工程实际,侧重介绍简支梁的横向加固方案。     

基础-墩-梁组合体系自振特性变化规律分析

铁路桥跨结构的横向振幅关系到桥梁的正常使用性能和行车安全性,它不仅与梁体本身特性有关,而且受到基础-墩-梁组合体系自振特性的影响。文中应用能量法推导考虑基础弹性约束的墩梁体系横向基频的解析公式,并将其和有限元软件的计算结果进行比较,验证解析公式的正确性。结果表明:在进行基础-墩-梁体系横向自振特性分析时可以忽略墩底承台的影响;墩梁质量比越大的体系,其横向基频对基础弹性约束越敏感。提出基础墩梁体系频率敏感性指标的概念,分别针对重力式桥墩、轻型墩桥梁,对比分析增加墩柱刚度和基础刚度对提高体系横向基频的有效性,为工程设计提供参考。     

铁路既有线上承钢板梁提速后的横向刚度及加固问题

通过既有线铁路提速试验，分析了上承钢板梁横向刚度的要求，提出合理的加固方案．     

铁路桥梁横向振动模拟及适应快速行车结构型式的研究

针对铁路提速后出现的上承式简支钢板梁桥跨中横向振幅过大的问题,以羊楼司桥(L=32m单跨上承式简支钢板梁桥)为例进行实桥检测和数值模拟,建立车辆、线路、桥梁三者的联合模型,考虑轮轨接触力,应用MSC/DYTRAN大型结构分析程序进行车线桥动力相互作用的仿真分析。研究揭示我国用量最多的C62型货车以70∽80km/h的速度空载通过时,该跨度的钢板梁桥发生横向谐振的机理。此外,用该方法对32m跨长的组合梁结构进行桥梁动力特性及列车走行性分析,表明该结构满足提速货车和高速电动旅客列车走行的要求。研究结果对我国高速铁路桥梁建设和既有桥梁的改造具有积极意义。     

铁路简支T梁运架施工作业安全风险分析及对策

铁路T梁主要采用简支结构和预制架设施工方案,铁路T梁由于结构重心较高,梁片的自稳性差,在运输过程中极易发生梁片倾斜失稳造成事故.DJ型无轨式架桥机架设铁路T梁过程中也容易发生纵向或横向失稳倾覆事故.本文结合目前采用的两种主要架梁工法,对铁路简支T梁运架施工潜在的主要安全风险进行深度剖析,从技术和管理角度提出相应的对策措...     

浅议预应力混凝土梁横向联结施工技术

介绍胶新铁路新型提速梁横向联结施工中的清孔、绑扎钢筋、支模、混凝土灌筑和梁横向张拉、压浆及封端的施工工艺.     

Development of fatigue test method and improvement of fatigue life by new functional steel plates for welding of trough rib and deck plate of orthotropic decks

Under heavy traffic conditions, some fatigue cracks have been found at welding joints between U-shaped ribs “trough ribs” and deck plates. Fatigue cracks along thickness direction of deck plate from root tip are important because visual crack detection from outside is limited. In this paper, new functional steel plates with initiation resistance of fatigue crack at weldment and propagation resistance at base material are applied to deck plate to evaluate improvement of fatigue life. We conducted fixed-point fatigue tests with real scale partial models consisted with one trough rib and a transverse girder, and the elastic FEM (Finite Element Method) analysis corresponding to the fatigue test specimen. Based on these results, we studied the fatigue properties which focused on the difference between conventional steel plates and newly developed steel plates, FCA (Fatigue Crack Arrester). Fatigue cracks were initiated from root tip of welded joints between a trough rib and a deck plate. It is clarified that FCA steel plates instead of conventional steel plates can improve the fatigue life under the same welding conditions. This improvement effect becomes much clearer in the high cycle region, which is noticeable at the operation and management stage of bridges.     

Measured behavior of a curved composite I-girder bridge

Current techniques for the rating of horizontally curved composite steel girder bridges often use approximate methods of linear elastic analysis based on the assessment of individual straight girders with altered properties to account for member curvature. This paper summarizes measured versus computed results from a field test with heavy live load conducted on a multi-span, horizontally curved composite steel I-girder bridge in Duluth, Minnesota. Eight 320 kN (72,000 lb) trucks were placed on the bridge in 43 static and 13 dynamic loading configurations, and the results were compared to those obtained from linear elastic grillage analyses. Stresses up to 75% of the girder yield stress were obtained in the bridge, whose design was controlled by strength, thus representing some of the largest stresses ever achieved in an instrumented curved steel girder bridge, and behavior is described in the girders, diaphragms, lateral wind bracing, deck, bearings, and fatigue details. Grillage analyses are developed and used to corroborate the results and assess the accuracy of these procedures for load rating of bridges.     

交叉梁体系桥面板荷载有效分布宽度试验研究

为探究源于肋梁体系的荷载有效分布宽度规定在斜拉桥交叉梁体系桥面板上的适用性，设计制作 1∶6的斜拉桥主梁节段缩尺模型，同时基于弹性薄板理论，建立考虑横梁弹性支承的连续板受力分析模型，利用荷载横向对称变位试验的相关静载数据验证计算模型的准确性，进一步开展考虑横梁变形影响的桥面板荷载有效分布宽度研究。算例分析表明：考虑横梁变形的桥面板荷载有效分布宽度总比不考虑横梁变形的情况要大，且荷载有效分布宽度从横梁侧往板中移动时逐渐减小，与桥梁规范的分布规律相反，同时桥面板在靠近主梁侧存在双向受力区域，若依然采用荷载有效分布宽度规范值则会低估活载响应，设计时应该引起注意。     

城轨钢箱梁U肋正交异性钢桥面板疲劳应力的 正交化计算方法

针对城轨钢箱梁正交异性桥面板关键构造疲劳应力问题,基于有限元方法提出正交化计算方法。首先计算典型正交异性钢桥面构造疲劳应力在城轨A型车和B型车作用下的纵向影响范围及最不利加载位置,并分析减振垫、吊点横隔板、轨下纵梁和道床板等参数的影响。然后根据大量工程实桥设计参数统计提出轨道交通桥梁正交异性板钢箱梁基准计算模型,并建立基准计算模型的空间有限元模型,通过数值计算得到顶板厚度、横隔板高度、横隔板间距、轨下纵梁高度及2种常见开孔形式等关键设计参数的影响系数,基于正交化方法提出不同设计参数条件下正交异性桥面板结构细节的疲劳应力计算公式。最后通过算例验证了正交化计算方法的可靠性和适用性。结果表明:城轨A型车在疲劳荷载作用下结构受力最不利; 轨下纵梁刚度对疲劳应力有显著影响。     

Lateral vibration of footbridges by synchronous walking

On the T-bridge (a cable-stayed footbridge) the girder vibrated laterally with a frequency of 0.93 Hz, the natural frequency of the first lateral mode, when a large number of people crossed the bridge. Some pedestrians felt uncomfortable and unsafe. The girder was excited by the lateral dynamic force which was produced by the zigzag movement of pedestrians. Once the bridge started to vibrate, some of the pedestrians synchronized with the girder vibration, which further increased the girder response. The same vibration occurred on the London Millennium Bridge and the M-bridge (a suspension footbridge), where field measurements were conducted. A dynamic model was then proposed to evaluate the pedestrians’ synchronized dynamic forces. Overall behavior of the girder response calculated by this dynamic model agreed with the measured values on the bridges. It was found by parametric studies that smaller bridge damping and smaller bridge mass produced larger girder response. Higher pedestrian density also increased the girder response unless they were too crowded to walk normally.     

A numerical investigation on the fire response of a steel girder bridge

The response of bridges subject to fire is an under researched topic despite the number of bridge failures caused by fire. Since available data shows that steel girder bridges are especially vulnerable to fire, this paper delves into their fire response by analyzing with a 3D numerical model the response of a typical bridge of 12.20 m span length. A parametric study is performed considering: (1) two possibilities for the axial restraint of the bridge deck, (2) four types of structural steel for the girders (carbon steel and stainless steel grades 1.4301, 1.4401, and 1.4462), (3) three different constitutive models for carbon steel, (4) four live loads, and (5) two alternative fire loads (the hydrocarbon fire defined by Eurocode 1 and a fire corresponding to a real fire event). Results show that restraint to deck expansion coming from an adjacent span or abutment should be considered in the numerical model. In addition, times to collapse are very small when the bridge girders are built with carbon steel (between 8.5 and 18 min) but they can almost double if stainless steel is used for the girders. Therefore, stainless steel is a material to consider for steel girder bridges in a high fire risk situation, especially if the bridge is located in a corrosive environment and its aesthetics deserves special attention. The methodology developed in this paper and the results obtained are useful for researchers and practitioners interested in developing and applying a performance-based approach for the design of bridges against fire.     

箱型连续梁桥复合加固效果动力特性评定

箱型桥梁复合加固的效果是工程中比较关注的课题。本文结合典型箱型连续梁桥-连霍高速公路仁存沟高架桥病害情况,采用复合加固手段提高桥梁承载能力。针对该桥复合加固的效果评定,采用了比较加固前后桥梁动力特性的变化方法进行。建立了该桥的数值模型,分别研究了体外预应力、铆粘钢板、增大截面及粘贴碳纤维布和复合加固法等多种加固措施对桥梁动力特性的影响。计算结果表明,铆粘钢板法、增大截面法等加固法明显影响了桥梁振动频率,可采用频率的变化来评估加固效果;体外预应力加固法、外贴碳纤维和复合加固方法对桥梁动力特性的影响比较复杂,可以通过联合动力特性和静力测试分析加固效果。     

行人导致侧力的试验研究

根据对几座斜拉索人行天桥的观测发现，当大量行人通过天桥时，可在桥支架上引起频率大约为1．0Hz的侧向振动。行人的曲线运动会导致侧向动力，从而引起桥支架的振动。一旦大桥开始振动，一些行人便开始与支架共振，从而进一步增加了支架反应。试验主要为寻找行人在振动桥面上所产生的动态力。行人走在振动台上专门设计的钢板上，振动台有着不同的频率和振幅。