大跨径斜拉桥施工过程中无应力状态控制法

为了满足大跨径斜拉桥目标成桥状态,得到大跨径斜拉桥在施工过程中拉索的张拉力,提出了大跨径斜拉桥在施工过程中的拉索索力计算调整拉索无应力长度的降温法。倒退分析法和传统无应力状态控制法在计算大跨径斜拉桥施工过程中存在缺陷,在传统无应力状态控制法的基础上,提出了调整拉索无应力长度的降温法。该方法可用于计算大跨径斜拉桥且计算方法简单,计算结果精度较高,能够满足工程要求。     

世界第一大斜拉桥——苏通大桥

世界上规模最大、技术难度最高的斜拉桥———苏通长江大桥近日在南通进行奠基仪式 ,这是江苏省又一座跨越浩浩长江、连接南通和苏州 (常熟 )的特大型长江大桥。万里长江的入海口———南通将动工兴建主跨度达 1 0 88米的双塔斜拉桥 ,这是继日本主跨度为 890米的多多罗大桥后 ,世界上跨径最大的斜拉桥 ,也比正在设计中的香港昂船洲大桥主跨 1 0 1 8米还宽出 70米 ,被称作“万里长江第一”(离长江入海口最近的一座大桥 )。大桥主塔高 2 98米 ,为世界第一高桥塔 ,比日本明石大桥高近 2 0米 ,比目前国内最高桥塔高出近 1 0 0米。大桥基础埋置深…     

强震作用下独塔斜拉桥抗震性能分析

以某跨径为110 m的独塔异形斜拉桥为工程背景,通过非线性有限元分析对斜拉桥在强震作用下的地震响应特性及减震措施进行了研究,得出如下结论:相比Lander-amboy波,卓越周期与桥梁固有周期较为接近的Cerro Prieto波能够引起结构较大的地震响应。行波效应能够显著增大工程背景斜拉桥的地震响应,且随着视波速的增大,桥梁的加速度响应明显增大。阻尼系数25 000 kN·s/m为工程背景斜拉桥的最优粘滞阻尼器设计参数,且在塔梁连接处安装该参数粘滞阻尼器后,斜拉桥减震效果显著,尤其能明显减小结构的位移响应。     

斜拉桥施工技术探讨

斜拉桥是当代桥梁世界里的一颗新星,是一种更有效地利用结构材料和较好适应大跨径桥梁的新桥型.本文就斜拉桥施工技术进行了深入的探讨,具有一定的参考价值.     

《千米级斜拉桥结构体系、设计及施工控制关键技术》项目简介

“千米级斜拉桥结构体系、设计及施工控制关键技术”由中交公路规划设计院有限公司张喜刚等完成,属土木建筑领域。本项目在国际上首创了千米级斜拉桥结构体系技术、新型结构及特殊设计方法、大型深水群桩基础施工控制技术、千米级斜拉桥塔梁索施工控制技术,一举攻克了斜拉桥跨径突破千米的技术瓶颈,     

科技简讯

飞跨上海浦江两岸的南浦大桥于1991年11月19日建成通车.该桥为一跨过江的双塔双索面叠合梁结构的斜拉桥,全长8346米,净高46米,桥下可通行5.5万吨级巨轮.主桥全长846米,主孔跨径823米,这个跨径规模在世界已建成的同类桥梁中列第二位.主     

人间彩虹——斜拉桥图解

斜拉桥,又称斜张桥,是将主梁用许多斜拉索直接拉在桥塔上的一种桥梁,是由承压的塔、受拉的索和承弯的梁体组合起来的一种结构体系.如横跨浦江两岸设计精巧、犹如彩虹的杨浦大桥,全长32.4公里、主跨1088米的苏通大桥,是当今世界最大跨径斜     

以和谐发展促教育公平

经过不懈的努力,浙江教育实现了"两大跨越":一是实现了由普及九年义务教育到普及十五年教育的跨越;二是实现了由高等教育精英化到高等教育大众化的跨越.进入新时期,随着一系列新情况、新要求的出现,浙江教育需要思考和解决的问题比以往有所增加.     

天堑变通途——访中铁大桥局集团有限公司总工程师、中国工程院院士秦顺全

武汉天兴洲公铁两用长江大桥是中国铁路客运专线第一座跨越长江的特大型公铁两用桥梁。是世界上第一座按四线铁路修建的公铁两用桥梁，在当今世界同类型大桥中拥有“跨度、荷载”两项第一的桂冠：斜拉桥主跨504米为世界公铁两用桥梁跨度之首；     

气泡上升中的学问(初二、初三)

1.质量变小的气泡给烧杯里的水加热,随着水温的升高,水中有越来越多的气泡从烧杯底部升起.在水沸腾前,气泡在上升过程中体积逐渐变小,乃至消失,这是为什么呢?原来水是热的不良导体,在水沸腾前,烧杯中上部的水温比底部的水温低,底部的水最先汽化产生气泡.在浮力的作用下,气泡不断上升.由于上部水温低些,气泡中的水蒸气又会液化成水,气泡中的水蒸气就越来越少.因此,水沸腾前,气泡在上升过程中质量变小,体积也逐渐变小.     

斜拉桥主梁施工底板局部承压安全验算方法

混凝土斜拉桥采用挂篮施工主梁时,挂篮底部行走轮对主梁底板产生巨大的竖向反力.混凝土底板、肋板可能在此反力作用下发生局部承压开裂破坏,需进行安全验算.行走轮与底板的接触区域是未知的,混凝土的受力变形均由接触区域决定.为寻求简单适用的计算方法,采用弹性接触Hertz理论,求解行走轮与混凝土板接触区域大小及应力分布,在此基础上应用规范推荐公式进行底板及肋板的抗裂安全验算.算例表明,该方法是可行的,可以简便地进行主梁底板的局部承压安全验算.     

桥梁建筑美学特征与结构设计

从统一和谐、均衡稳定、比例协调、韵律优美等基本要素方面探讨了桥粱建筑的美学特征；以粱桥、拱桥、斜拉桥、悬索桥等桥型为例，研究了桥梁美学在结构设计中的表现手法。     

双塔单索面人行钢斜拉桥的设计与受力分析

以某双塔单索面人行钢斜拉桥为对象,采用Midas Civil建立全桥空间杆系有限元模型,进行恒载、活载和承载能力极限状态作用下结构受力性能分析,同时开展该桥的动力特性分析。研究表明:对于该异形斜拉桥,活载引起的主梁和主塔弯矩效应较恒载作用下的结果更加显著;承载能力极限状态作用下,该桥主梁、主塔、斜拉索等主要承重构件的最大应力均小于材料容许应力,满足规范要求;动力特性分析结果表明主梁面内刚度和主塔面外刚度较小,此外遮阳棚的局部振动在高阶振型中所占比例较大,在地震作用下可能发生破坏;该桥的一阶竖向自振频率为1.92 Hz,不满足现行规范要求,建议采取有效的减振措施来控制人致振动响应。     

混凝土独塔斜拉桥主梁裂后结构性能

针对一座主梁存在裂缝的混凝土独塔斜拉桥,考虑混凝土裂缝对材料本构关系的影响,对设计荷载作用下桥梁的整体与局部响应进行分析以评估其承载能力。结果表明,在最不利的工况中,开裂后主梁顶板、底板和斜腹板、直腹板上未开裂区域的主拉应力和主压应力都小于规范给出的强度标准值;裂缝法向和切向的压应力均小于规范强度标准值,裂缝切线和法线方向的拉应力在局部很小的范围内略高于规范的抗拉强度标准值。开裂区域局部承载力有所降低,但车辆荷载作用下裂缝不会进一步扩展。     

Theoretical and experimental study on shear lag effect of partially cable-stayed bridge

INTRODUCTION The Lanzhou Xiaoxihu Yellow River Bridge is one of few partially cable-stayed bridges. It is con-sidered a partially cable-stayed bridge because beams are under both axial loads and flexure loads. The cables are arranged in semi-fan configuration in a single plane so that they can be easily anchored to the tower. The cable-stayed portion is a 136 m center span with two 81.2 m side spans. The width of box girder’s top flange is 27.5 m, and the bottom flange’s width is 15.…     

Nonlinear Dynamic Reliability of Coupled Stay Cables and Bridge Tower

Nonlinear vibration can cause serious problems in long span cable-stayed bridges.When the internal resonance threshold is reached between the excitation frequency and natural frequency,large amplitudes occur in the cable.Based on the current situation of lacking corresponding constraint criteria,a model was presented for analyzing the dynamic reliability of coupling oscillation between the cable and tower in a cable-stayed bridge.First of all,in the case of cable sag,the d'Alembert principle is applied to studying the nonlinear dynamic behavior of the structure,and resonance failure interval of parametric oscillation is calculated accordingly.Then the dynamic reliability model is set up using the JC method.An application of this model has been developed for the preliminary design of one cable-stayed bridge located on Hai River in Tianjin,and time histories analysis as well as reliability indexes have been obtained.When frequency ratio between the cable and tower is approaching 1∶2,the reliability index is 0.98,indicating high failure probability.And this is consistent with theoretical derivation and experimental results in reference.This model,which is capable of computing the reliability index of resonance failure,provides theoretical basis for the establishment of corresponding rule.     

Dynamic responses of cable-stayed bridges to vehicular loading including the effects of the local vibration of cables

Stay cables, the primary load carrying components of cable-stayed bridges (CSBs), are characterised by high flexibility which increases with the span of the bridge. This makes stay cables vulnerable to local vibrations which may have significant effects on the dynamic responses of long-span CSBs. Hence, it is essential to account for these effects in the assessment of the dynamics CSBs. In this paper, the dynamic responses of CSBs under vehicular loads are studied using the finite element method (FEM), while the local vibration of stay cables is analyzed using the substructure method. A case study of a cable-stayed steel bridge with a center span of 448 m demonstrates that stay cables undergo large displacements in the primary mode of the whole bridge although, in general, a cable’s local vibrations are not obvious. The road surface roughness has significant effects on the interaction force between the deck and vehicle but little effect on the global response of the bridge. Load impact factors of the main girder and tower are small, and the impact factors of the tension of cables are larger than those of the displacements of girders and towers.     

Aerodynamic stability of cable-supported bridges using CFRP cables

To gain understanding of the applicability of carbon fiber reinforced polymer (CFRP) cable in cable-supported bridges, based on the Runyang Bridge and Jinsha Bridge, a suspension bridge using CFRP cables and a cable-stayed bridge using CFRP stay cables are designed, in which the cable’s cross-sectional area is determined by the principle of equivalent axial stiffness. Numerical investigations on the aerodynamic stability of the two bridges are conducted by 3D nonlinear aerodynamic stability analysis. The results showed that as CFRP cables are used in cable-supported bridges, for suspension bridge, its aerodynamic stability is superior to that of the case using steel cables due to the great increase of the torsional frequency; for cable-stayed bridge, its aerodynamic stability is basically the same as that of the case using steel stay cables. Therefore as far as the wind stability is considered, the use of CFRP cables in cable-supported bridges is feasible, and the cable’s cross-sectional area should be deter-mined by the principle of equivalent axial stiffness.     

基于三角模糊数的悬索桥梁状态评估研究

基于三角模糊数判断矩阵的模糊层次分析法,提出利用模糊数比较大小原理,获得确定元素的权重值,较好解决了三角模糊数无法获得确定元素权重值的问题。并以福州市鼓山大桥悬索桥为工程背景,利用三角模糊数模糊层次分析法建立该桥状态评估指标体系模型,确定评估指标的权重及最终的状态评估值。该评估方法简单易行,精度较高,可以为大跨度悬索桥的养护管理及健康状态预警提供科学依据。