大跨径斜拉桥斜拉索静风荷载计算方法比较

针对大跨径斜拉桥对风荷载作用十分敏感的特点，分析了斜拉索风荷载的不同计算方法的差异，并以苏通长江公路大桥为例比较了不同计算方法对关键截面响应的影响．分析表明，对于大跨径斜拉桥，斜拉索上的风荷载计算方法对关键截面的响应影响较大；横桥向风作用下，在不考虑斜拉索设计风速的误差的前提下，可将斜拉索上风荷载平均分配到其端部；顺桥向风荷载作用下，则斜拉索上风荷载应直接作用在拉索分段的节点上。     

Aerodynamic problems of cable stayed bridges spanning over one thousand meters

The elongating of cable-stayed bridge brings a series of aerodynamic problems. First of all,geometric nonlinear effect of extreme long cable is much more significant for cable-stayed bridge spanning over one thousand meters. Lateral static wind load will generate additional displacement of long cables,which causes the decrease of supporting rigidity of the whole bridge and the change of dynamic properties. Wind load,being the controlling load in the design of cable-stayed bridge,is a critical problem and needs to be solved. Meanwhile,research on suitable system between pylon and deck indicates fixed-fixed connection system is an effective way for improvement performance of cable-stayed bridges under longitudinal wind load. In order to obtain aerodynamic parameters of cable-stayed bridge spanning over one thousand meters,identification method for flutter derivatives of full bridge aero-elastic model is developed in this paper. Furthermore,vortex induced vibration and Reynolds number effect are detailed discussed.     

自锚式斜拉-悬吊协作体系桥静风响应分析

自锚式斜拉-悬吊协作体系是一种新型桥梁结构形式,存在着抗风稳定性等技术难题.采用计算缆索承重桥静风响应的方法,研究了金州海湾大桥方案桥在静风作用下,主梁初始攻角与附加攻角、桩基础刚度、缆索体系风荷载和拉索分段对主梁和桥塔静风位移的影响.研究结果表明:附加攻角对方案桥的静风位移影响不大;如果不考虑桩基础刚度的影响会严重低估结构的侧向位移;在缆索体系风荷载作用下的侧向位移占总体位移的20%左右.     

斜拉桥气弹模型拉索振动数字摄影测量技术

利用数字摄影测量的方法,在斜拉桥全桥气弹模型风洞试验中对拉索结构实现振动位移的动态测量.介绍了该方法的基本原理,并通过某斜拉桥进行了实测研究,获得了该桥气动失稳状态时的拉索振动形态,为桥梁颤振发散机理的研究提供了直接依据.讨论了拉索位移测量方法的误差,并提出改进测量精度的对策.     

基于变形协调原理的多塔斜拉桥非边塔纵向抗推刚度

为深入探寻多塔斜拉桥刚度特征,将斜拉索对桥塔的约束比作弹簧刚度这一理念引入多塔斜拉体系.选取多塔斜拉桥的最典型形式——三塔斜拉桥建立弹簧刚度等效模型,基于变形协调原理,求解多塔斜拉桥非边塔纵向抗推刚度,对推导的公式进行算例验证,并分析结构主要参数对桥塔纵向抗推刚度的影响.研究结果表明:对非边塔左跨施加均布荷载时,本文推导公式的非边塔塔顶偏位解与已有文献有限元解间的误差在6.82%以内,说明本文推导的非边塔纵向抗推刚度公式能够反映多塔斜拉桥桥塔的刚度特征,符合多塔斜拉桥概念设计的要求;非边塔纵向抗推刚度与桥塔自身刚度、主梁刚度、拉索与主梁夹角、拉索线刚度和桥塔拉索锚固间距等因素有关.     

大跨径中承式钢箱系杆拱桥施工阶段稳定性分析

为明确大跨径中承式钢箱系杆拱桥施工阶段稳定性,以西双版纳澜沧江黎明大桥为研究对象,建立全桥空间有限元模型对该桥进行施工阶段全过程稳定性分析,研究考虑初始缺陷的几何非线性、材料非线性、风撑、临时风撑、吊杆非保向力和抗风缆索对结构施工阶段稳定的影响。结果表明：施工全过程中结构的稳定系数满足相应规范要求,考虑初始缺陷的几何非线性分析,结构的稳定系数降低7%～8%;考虑几何与材料双重非线性时,结构的稳定系数降低49.67%～52.05%,材料非线性对结构稳定性有显著影响。增加永久风撑数量能有效提高缆索吊装最不利施工阶段及拱肋合拢后施工阶段的稳定性,布设临时风撑能显著提升结构缆索吊装最不利施工阶段的稳定性,非保向力效应对中承式钢箱系杆拱桥稳定性有较大的影响,布设抗风缆索显著提升拱肋合拢后施工阶段稳定性。由此可见,施工阶段稳定性的影响因素较多,本研究可为同类型桥梁的施工与设计提供参考。     

Line shape calculation method for suspension bridge catwalk considering different states of bearing cables

The line-shape of catwalk of long-span suspension bridge is obtained by using the segmental catenary method to carry out the iterative calculation, where all the bearing cables are considered as one cable, and transversal passages and gantry are treated as nodes which divide the catwalk into several segments. The difference of line-shape and force between catwalk bearing cable and gantry bearing cable is not usually considered, but the line-shape of two kinds of cables is actually inconsistent because of the constraints from gantries. Based on the segmental catenary method, considering the different states of bearing cables (DSB calculation method), fine calculation is carried out. This method is applied to the design of a suspension bridge’s catwalk, and is compared with the traditional calculation method. It is obtained that the result is more reasonable and accurate by the coordination calculation method considering different states for two kinds of load-bearing cables, which is worth considering in the process of design and optimization for catwalk.     

Aerostatic Stability of Long-Span Cable-Stayed Bridges: Parametric Study

The increasing span of cable-stayed bridges has focused more attention on the aerostatic stability of the design and construction of such bridges. This paper presents a new method to analyze the nonlinear aerostatic stability of cable-stayed bridges including all three components of the wind load and the geometric nonlinearity. The analysis was used to investigate the effects of the wind angle of incidence, the wind load of individual bridge elements, the sagging of cable elements, the changes of tower height and the changes of side span length on the aerostatic stability of cable-stayed bridges. The results show that the wind angle of incidence and the wind loads on the cables have an important effect on the aerostatic stability of cable-stayed bridges.     

石家渡漓江大桥索力计算与施工差异探讨

从石家渡漓江大桥索力计算与实际施工差异着手，探讨钢管混凝土拱桥吊装斜拉扣挂系统中扣索力计算的方法，并针对计算假设与实际施工方法的差异提出对计算方法修正的建议，可使实际施工节省扣索，并减少施工量．     

Parametric Study on Cable-Stayed and Knee-Braced Steel Portal Frames

To improve wind resistance capacity of cable-braced steel portal frames,a double-braced portal frame was proposed by adding two pre-stressed knee braces to a cable-braced portal frame. To study the reasonable range of application and method of cable parameter determination for this novel structure,the influences of load condition, span, base constraint, and cable parameters on structural performance were investigated by using the finite element code SAP2000. The results show that pre-stressed knee braces can effectively resist both uplifted and lateral wind loads,so this cablestayed and knee-braced steel portal frame is suitable for large wind.When the vertical load is comparable with the wind load,this novel type of portal frames is suitable for a medium span( 21-48 m). The cables in the cable brace can be determined by structural vertical stiffness,and the cables in the knee brace can be designed as the same as those in the cable-stayed part for the reason that their cross sectional area has only a weak effect on the structure. If no cable fails,the pretension variation of the cable does not affect the stiffness of the portal frame. The cable in the cable brace,working together with the cables in the knee braces,can ease uneven distribution of internal force,and their pretensions can be determined according to actual engineering projects.     

静风荷载下的大跨度斜拉桥稳定性分析

由于风荷载对斜拉桥的作用比较敏感,尤其是对于柔性大跨度斜拉桥。文章基于伯努利方程推导整个断面的3方向静风荷载原理,并采用内外增量双重迭代以及发散机理的数学描述给出静风稳定性计算过程;结合斜拉桥本身特性,分析了某跨江大跨度斜拉桥的横桥向风荷载和竖桥向风荷载的影响;使用大型有限元软件MIDAS/Civil建立桥梁模型,并进行成桥状态静风荷载下的特性分析,据此来评估该桥的静力抗风性能,为相关桥梁的抗风性能分析与设计提供依据。     

腐蚀对风车联合作用下斜拉桥拉索 疲劳可靠性的影响分析

为探讨腐蚀对随机交通和风载联合作用下斜拉索疲劳可靠性的影响规律和机理,通过拉索高强钢丝的加速腐蚀和疲劳试验,提出了考虑腐蚀的斜拉索疲劳抗力模型;基于线性累积损伤准则,建立了考虑腐蚀影响的风车联合作用下拉索疲劳可靠性的分析方法和流程;依托工程实例,分析了腐蚀等级和时变腐蚀对拉索疲劳可靠性的影响.结果表明:随腐蚀加剧拉索动态疲劳可靠指标下降速率增大;等级达到Ⅲ级及以上的腐蚀对拉索疲劳可靠寿命影响显著,尤其对于靠近桥塔及辅助墩处拉索;Ⅳ级和Ⅴ级腐蚀时拉索疲劳寿命相对无腐蚀状况降幅最大分别达24%和44%;相对完好状况,时变腐蚀影响下拉索的动态疲劳可靠指标下降更为迅速,且降幅明显大于仅考虑腐蚀分级的状况.     

Research on key technologies in design of middle pylon of Taizhou Bridge

At the middle pylon of a three-pylon two-span suspension bridge, the effect of unbalanced loads on the adjacent spans may result in a series of technical bottlenecks in design, such as stability and anti-slippage between saddles and main cables. This article presents the researches conducted on structure selection and behavior characteristics of middle pylon, interaction mechanism between main cables and saddles and their anti-slippage safety performance, elastic and plastic stability analysis and safety assessment of steel middle pylon, and fatigue design load and method for steel pylon of Taizhou Bridge. According to the research results, a longitudinal inverted Y shape steel middle pylon is used in design, effectively solving many technical difficulties, and this type of pylon has become a suitable middle pylon structural form for many three-pylon two-span suspension bridges.     

高速铁路斜拉桥上无缝线路断缝值研究

为探明斜拉桥上无缝线路钢轨断缝值的规律特点,采用一种可靠的非线性梁轨相互作用模拟方式,建立了塔-索-轨-梁-墩-桩一体化的斜拉桥有限元模型,以中国高速铁路线上某（32＋80＋112）m单塔斜拉桥为例,分析讨论了线路纵向阻力模型、斜拉桥纵向约束方式、断缝出现位置、列车活载以及主梁和拉索温度变化等因素对断缝值的影响,得出以下结论：可根据《铁路无缝线路设计规范》（送审稿）选取纵向阻力模型;塔梁刚结或以固定支座相连时可有效减小断缝值;断缝出现在桥塔处时,断缝值最小（1.0cm）,伸缩调节器应设置在桥塔处;制挠力及主梁温度变化对断缝值影响较大,分析时应予以考虑.     

近断层斜拉桥弹塑性索与阻尼器组合横向减震

研究了近断层地震条件下,使用弹塑性减震索和黏滞阻尼器组合体系进行横向减震的斜拉桥的地震响应和减震规律.采用等效脉冲模型对实际近断层地震进行最小二乘拟合.人工合成Ⅱ类场地下的模拟近断层地震波3组,以永宁黄河大桥为工程背景,对人工近断层地震输入进行非线性时程分析,得到在不同脉冲周期的近断层地震作用下,减震措施设计参数对于塔梁相对位移等响应的影响.结果表明,拟合近断层地震下结构响应与实际地震相差较小,可以满足工程计算需求;近断层地震易造成大位移响应,弹塑性索参数设计时应使结构周期避开脉冲周期;容许减震索进入塑性与保持弹性相比,塔梁相对位移并不会明显增加,甚至在一些情况下会减小.     

基于ANSYS的主塔施工阶段静风受力分析

帆型桥体造型优美,倒映在水中的桥影恰似一艘帆船,给人以简约大方,迎风前行的感觉。某斜拉桥在横向桥采用单柱式塔型,纵桥向采用了帆型桥塔,主塔迎风面积较大,风对帆型结构产生的侧向推力也较大,有必要对桥塔施工过程进行抗风分析。为验算某斜拉主塔施工过程中,桥塔抗风是否符合安全要求,本文利用有限元程序ANSYS对其中三个工况进行分析计算。在模型中设置横撑和拉杆,对比有无横撑和拉杆对桥塔的影响,为工程施工提供参考依据。验算不均匀风速对帆型桥塔的影响,为结构设计提供参考依据。     

全混凝土无背索斜拉桥的运营安全分析

为研究全混凝土无背索斜拉桥结构在超载运营时的安全状态,以某桥为背景,采用空间结构有限元数值分析方法,基于双重非线性理论对无背索斜拉桥进行极限承载力分析。在设计车道荷载作用下,通过迭代计算多倍活荷载分析了桥梁结构首次出现开裂、斜拉索应力超过安全限值直至结构形成机构而进入破坏阶段的全过程结构安全系数,并得到结构应力、变形、索力等主要力学参数的变化规律。研究表明,此桥在主跨区域满布荷载时,截面的最不利开裂荷载为2.22倍的活荷载;拉索应力满足规范要求时最不利为6.14倍的活荷载;结构破坏时的最不利荷载为12.10倍的活荷载,且车辆偏载时的安全系数均小于中载。因此,该桥在运营过程中,应重视长索的索力状态,并尽量避免主跨区域重载车辆偏载停滞。     

运营状态下南京长江二桥拉索索力测试与分析

为准确获取运营状态下拉索索力,采用动测法对南京长江二桥进行了拉索索力测试,讨论了车辆荷载、阻尼器以及环境温度对索力测试的影响,并对运营状态下的索力测试结果进行了对比与分析.研究结果表明:相对于面外振动,拉索面内振动更容易受车辆荷载影响,利用面外振动可以较好的确定拉索的自振频率;阻尼器和温度对拉索自振频率影响较小.通过对比成桥状态的拉索索力测试值和本次索力测试值,可看出个别拉索索力变化较大,大部分拉索索力变化较小.     

斜弯独塔混合梁斜拉桥参数敏感性分析

为研究斜弯独塔混合梁斜拉桥在成桥状态下受结构设计参数的影响程度,对结构设计、施工监控和关键控制量制定等提供参考,以张家口纬二桥为工程背景,建立有限元模型。基于结构参数敏感性分析的摄动原理,引入敏感度分析指标,选取塔梁固结处弯矩值、桥顶纵向位移值、背索索力、主梁最大挠度为控制目标,对桥梁钢混结合段位置、桥塔局部温度荷载、斜拉索初拉力和背索竖向倾斜角度等结构参数进行敏感性研究。分析结果表明：桥梁钢-混结合段位置、斜拉索初拉力、背索竖向倾斜角度对斜弯独塔混合梁斜拉桥主梁挠度和桥塔线形影响较大。其中,混凝土梁和钢梁的跨度比变化15.73%,塔顶纵向位移、主梁最大挠度将分别变化30.3%和29.4%;桥塔局部温度荷载主要影响此类桥塔的纵向变形,对桥塔受力敏感度较低;背索竖向倾斜角度对斜弯独塔混合梁斜拉桥影响最为显著,背索竖向倾斜角度变化7%,塔顶纵向位移较初始位置最大变化也达到205.8%。     

广东江顺大桥抗风性能试验研究

采用风洞试验和CFD数值模拟相结合的方法对主跨700m的广东江顺大桥主桥结构抗风性能进行研究,包括主梁、桥塔气动参数试验与CFD模拟、主梁1/60几何缩尺比节段模型测振试验、主梁1/25几何缩尺比节段模型涡振试验、全桥气弹模型试验研究等.结果表明:该桥在成桥状态和施工状态具有足够的抗风稳定性,在设计风速下涡振性能和抖振响应性能均满足规范要求;大比例主梁节段模型得到的涡振振幅小于常规比例节段模型得到的涡振振幅,表明采用常规比例模型进行桥梁主梁涡振性能评估是偏于保守的.