【作者】 李胜利；

【导师】 欧进萍；

【作者基本信息】 哈尔滨工业大学 ， 土木工程， 2010， 博士

【摘要】 大跨径悬索桥施工期暂态结构刚度较低、工期较长、风环境复杂,成桥时不会发生的风效应存在发生的可能性。具有费时、费力、费财特点的风洞试验,主要针对影响施工安全的关键工况进行研究,对于影响小、工期短的工况不太适合,然而这些工况的施工在一定程度上是以牺牲时间或工作人员的安全性和舒适性为代价的。当前,随着大跨径悬索桥跨度不断增大,对施工要求愈来愈高,施工时间更加宝贵,施工人员的安全性和舒适性也越来越受到重视。同时,随着具有省时、省力、省财特点的数值技术日新月异,用理论知识和计算机来解决大跨径悬索桥施工抗风各种问题成为可能。因此,进行大跨径悬索桥施工期暂态结构的抗风性能和控制更加细致入微的理论分析和数值模拟研究具有一定的理论与实际意义。本文在综述大跨径悬索桥施工期抗风性能及控制和现场调研的基础上,针对存在的问题和不足,运用ansys、fluent、matlab等软件和现有的风洞试验结果相结合的研究方法,在多方面展开了深入研究,主要内容和成果如下:1.针对大跨径悬索桥施工期门型变截面桥塔考虑塔柱气动干扰效应影响的驰振性能问题,利用有限元和CFD相结合的方法,提出了一种变截面高耸结构驰振分析的实用数值方法,利用该方法系统分析了大跨径悬索桥桥塔施工期典型工况的驰振性能并研究了气动干扰效应对双塔柱驰振性能的影响。结果表明:本文提出的计算变截面高耸结构的数值方法和所采用的数值风洞湍流模型方法均正确。横桥向,由于塔柱间气动干扰效应的存在,双塔柱整体的驰振性能与不考虑气动干扰效应的单柱的驰振性能不同;与矩形截面柱相比,采用截面倒角的形式对桥塔的驰振性能并不有利。对于单塔柱,矩形截面柱和倒角截面柱的前柱驰振力系数均大于零,后柱均存在小于零的情况,并且后柱的驰振力系数绝对值大于双塔柱整体的驰振力系数绝对值。纵桥向,桥塔双塔柱整体和单塔柱均不存在驰振力系数小于零的情况。对于本文算例的混凝土桥塔施工期各工况方柱截面和倒角截面塔柱不存在驰振失稳的问题。2.针对大跨径悬索桥桥塔施工期风致抖振性能和施工人员舒适性的问题,采用了ANSYS的瞬态动力学研究方法,研究了某大跨径悬索桥砼桥塔施工期各工况的抖振响应以及组合框架结构形式的砼桥塔施工期的舒适性。研究结果表明:对于门型悬索桥桥塔的施工舒适性来说,最不利工况发生在没有施工横梁的工况,而不是施工的最终裸桥塔工况,传统上仅仅根据位移均方根和最大值来衡量桥塔施工可靠性是不科学的,应该同时考虑狄克曼指标对施工人员舒适性的影响。3.针对无抗风缆猫道动力特性缺乏理论研究的问题,采用理论建模和ANSYS有限元预应力索结构模态分析的研究方法,对大跨径悬索桥无抗风缆猫道动力特性进行了研究,理论推导了无抗风缆猫道1阶竖向、侧向和扭转振动频率公式,数值分析了各参数对猫道振动特性的影响。结果表明:桥塔对猫道自振频率影响很小;猫道的振动频率随着矢跨比的增加而呈减小的趋势;横向天桥的位置和个数对猫道低阶频率影响很小,对高阶频率有一定影响;平行索对猫道频率几乎无影响,交叉索对猫道低频影响很小,对扭转频率有一定提高;CFRP与钢承重绳猫道的自振频率差别不大,却能大大降低对卷扬机等施工机具的要求。4.针对大跨径无抗风缆猫道双重非线性静风稳定性问题,结合节段模型风洞试验结果,运用二次开发的ANSYS软件,建立东海某大跨径悬索桥无抗风缆猫道的有限元模型,综合考虑由有效风攻角和有效风速构成的静风荷载非线性和猫道几何非线性的双重影响,采用增量双重迭代搜索法,研究了猫道静风失稳的全过程以及各参数对猫道静风稳定性的影响。结果表明:大跨径猫道的失稳形态主要为空间弯扭耦合失稳,扭转变形对猫道的静风失稳有明显影响,升力和扭转力矩是猫道失稳的关键因素;大跨径猫道的静风稳定性计算必须同时考虑由有效风攻角和有效风速对静风荷载非线性和猫道的几何非线性的影响;不计入猫道结构变形的影响,则会高估猫道的抗静风稳定能力;适当减小横向天桥的间距和增大其刚度可以提高猫道的静风失稳临界风速;随着初始风攻角和猫道矢跨比的增大,猫道的静风稳定性有所下降;设置水平拉索会降低猫道静风失稳临界风速。5.针对施工期暂态主缆驰振稳定性问题,采用CFD数值模拟和有限元数值计算的研究方法,结合正在建设的东海某大跨径悬索桥,研究了施工期暂态主缆未采取抗风措施时两种常见的施工方案各工况截面的驰振力系数,比较了两种施工方案的优劣,然后针对较优的施工方案,计算了其驰振临界风速。结果表明:尖顶型方案的驰振性能优于平顶型方案并且该桥施工期尖顶型方案暂态主缆存在会发生驰振失稳的工况。6.针对施工期暂态主缆驰振控制的问题,基于预应力索结构的静动力和瞬态分析,对东海某大跨径悬索桥施工期暂态主缆的辅助索制振参数进行了研究,同时研究了用辅助索控制暂态主缆驰振失稳的具体方案,采用了考虑几何非线性影响的有限元数值分析研究方法,建立了该悬索桥施工期暂态主缆-猫道系统的有限元模型,研究了辅助索位置、布置方式和刚度大小对暂态主缆1阶竖向振动频率的影响;研究了辅助索阻尼、刚度和个数对暂态主缆面内等效阻尼比的影响;最后研究了辅助索控制暂态主缆驰振的具体方案。结果表明:为了提高暂态主缆1阶竖向振动频率,辅助索应该对称竖向布置,且增大辅助索的数目特别是跨中设置辅助索可以较大幅度地提高该频率值;增加辅助索的直径和个数可以较大地增加对暂态主缆的面内制振效果;在该悬索桥中跨12分点处对称竖向布置每组由1根直径为10mm的钢筋组成的11组辅助索时即可控制暂态主缆的驰振失稳。7.针对大跨径悬索桥迫切需要进行施工期吊梁颤振概率评价的问题。采用风洞试验和可靠性计算相结合的研究方法,结合东海某大跨径悬索桥,编制了可靠度计算程序,对大跨径悬索桥施工期吊梁颤振可靠性及影响参数进行了研究。结果表明:对称架梁初期颤振稳定性最差;施工期吊梁颤振稳定性失效概率随桥位设计风速的变化是非线性的,较大的设计风速对应较大的失效概率,极值风速变异系数对其影响效果有限;地表越粗糙,其失效概率越大;增大风攻角则增大了施工期吊梁颤振失稳的可能性;忽略流场的紊流性能得到的对称施工各阶段颤振失稳分析结果导致施工初期很不安全,施工后期非常保守;采用非对称施工比对称施工具有较好的抗颤振的性能;增大偏心质量比要比增大偏心距对施工阶段颤振失效概率影响明显得多;对称施工时施加竖向交叉式吊杆只能在施工末期提高其颤振可靠性,在施工中期反而会降低其颤振可靠性。更多还原

【Abstract】 The rigidity of the transient structure for the large span suspension bridge is low, the construction time is long, and the wind environment is complicated at the construction stages, so wind effects that cannot take place after construction to be finished may take place. The wind tunnel test whose some characteristics are time–consuming, vigour-squandering and costly is principally used to study the key cases that can affect the construction safety, but is not quite fit to research the cases having the fetures of the little influence on constructon and short construction period which sacrifice time or security and comfort of builders at great cost to some extent. With increasing span of the large span suspension bridge, the construction requirement is becoming higher and higher, time is more precious, and the security and comfort of builders get more and more attention. At the same time, as the numerical technique whose some characteristics are economical, less labor and time is changing quickly, it is possible to settle the all kinds of problems about wind resistance of the large span suspension bridge at the construction stages using the theoretical knowledge and computer. So it has theoretical and practical significance to proceed the theoretical analysis and numerical simulation of wind-resisted performance and control for transient structures of long-span suspension bridges during construction.Based on the review and prospect of wind performance and control for transient structure of large span suspension bridge under the construction stages and the on-site survey, applying the research method by combination of ANSYS, FLUENT, MATLAB and other software and results of wind tunnel tests, the thorough theoretical research of the problems and shortcomings existing in wind-resisted performance and control for transient structures of long-span suspension bridges during construction are carried out in many ways. The main contributions of the dissertation are given as follows:1. To solve the problem of galloping performance of erecting gate type variable section pylon of the large span suspension bridge considering the influence of aerodynamic interference effects, a practical numerical method for galloping analysis of variable section high-rise structure is advanced applying the research method by combination of finite element and CFD and is used to analyzed the galloping performance of key cases for the erecting typon of the large span suspension bridge and research the influence of aerodynamic interference effects on the galloping performance of twin columns. The results show that the numerical method of galloping analysis of variable section high-rise structure and the numerical wind tunnel method are both right. Beacause of aerodynamic interference effects between twin columns, the galloping performance of twin columns is different with single column and it is more disadvantageous for the galloping performance of twin columns to adopt chamfering section than rectangular section in the lateral direction. For the single column in the lateral direction, the galloping coefficients of anterior column with rectangular and chamfering section are greater than zero but those of later column exist the conditon less than zero, and absolute values of the galloping coefficients for the later column of single column are larger than those of twin columns. Beacause the galloping coefficients of twin columns and single column are both greater than zero, the galloping instability can not happen. The galloping critical wind speeds of all cases for the concrete typon in the example are larger than the design wind speed during construction, so the galloping instability of the erecting concrete typon can not happen.2. On the basis of methods of finite element ANSYS model, the wind-induced buffeting behaviour of four cases of concrete pylon at construction stage of long-span suspension bridge was studied. The wind-induced buffeting behaviour and the comfort assessment of four cases of concrete pylon at construction stage of long-span suspension bridge were researched using transient dynamic analysis of finite element ANSYS. Results show that the worst disadvantage state of the pylon at construction stage is not nude pylon ,but case without crossbeam for the comfort of the pylon for the suspension bridge at the construction stages, and so the judging method of the reliability for the pylon of suspension bridge at the construction stages to adopt the RMS and maximum value of the displacement is unscientific and the comfort for the pylon of the suspension bridge should use simultaneously the Dieke mann index.3. On the basis of methods of theoretical derivation and finite element ANSYS modelling, the dynamic behaviour of catwalks without wind-resistant cable of long-span suspension brdige was studied. The vibration frequencies of the first order vertical and side directions, and the first order torsional frequency are derived in theory. The influence of the related parameters was researched using theoretical calculation and model analysis of prestressing cable structures of finite element ANSYS. Results show that the vibration frequencies of the first order symmetry, antisymmetry side directions and antisymmetry vetical direction of the catwalks are independent of the tension of load bearing cables and quality of per-span-length; the influence of pylons on natural frequency of the catwalks without wind-resistant cable is little; the vibration frequencies of the catwalks submit the reduced trend with the increace of the ratio of rise to span; The influences of the positions and population of the transverse overbridges are trivial on low order frequencies and large on the high order frequecies; the parallel cables make almost no difference on the every frequencies and the across cables have no effect on low frequency and have to a certainty advance on the torsional frequencies; the natural frequencies of the catwalks with the bearing ropes made in CFRP and steel are nearly identical,but the catwalks with the bearing ropes made in CFRP reduce the require on the construction machinery such as winding machine.4. Referring to the results of sectional model test and using secondary developed ANSYS finite element software, the finite element modeling for catwalks without wind-resistant cable of a suspension bridge was established. The nonlinear aerostatic stability and the influences of nonlinearity for static wind load, the space between the transverse crossover and rigidity, the initial angle of incidence, the ratio of rise to span for catwalks and the horizontal coupling cables on the aerostatic stability of the catwalks were studied considering the nonlinear effects of catwalks and static wind load and adopting the incremental double iteration method. Results show that the buckling form for catwalk without wind-resistant cable is mainly coupled bending-torsional instability that the torsional deformation has obvious effect on the instability and the lift force and torsional moment are key factors for the instability, the calculation about the stability of the catwalk must be considered simultaneously the effect of the static wind load and the geometry nonlinearity and the aerostatic stability for the catwalk can be overestimated without the influence of structural deformation for the catwalk, the critical wind speed for aerostatic instability can be increased through minishing the spaces between the transverse crossbridges and augumenting the rigidity of those and reduced through augumenting the initial angle of incidence and the ratio of rise to span for catwalks and setting the horizontal coupling cables.5. To solve the problem of galloping instability of the transient main cables.The galloping coefficients of type sections for two construction projects of the transient main cables without wind-resistant measures were investigated for the first time by means of the CFD and finite element soft wares, referring to the erecting some large span suspension bridge, and the two projects were compared. The galloping critical wind speeds of the better construction project are computed. Results show that the galloping performance of the Jian-Ding project is better than that of the Ping-Ding project and the galloping instability can happen for the Ping-Ding project of the long-span suspension bridge during construction.6. On the basis of static, dynamic and transient analysis for the prestressing cable structures, the parametres of controlling the galloping vibration of the transient main cables of some long-span suspension bridge at the construction stages with the assistant cables and detailed scheme for controlling the galloping vibration of those with the assistant cables are investigated adopting the method of the finite element considering the geometry nonlinearity. The review and propect for the galloping vibration and controling vibration with assistant cables are summarized, the finite element modeling of the system for transient main cables and catwalk is established, and the influence of the position of the assistant cables, diposed fashion and the rigidities upon the first vertical bend vibration frequencies of the transient main cables is researched. At the same time, the effect of the damp and the rigidities of the assistant cables on the equivalent damping ratio of the transient main cables inside the plane is studied. In the end,the detailed scheme for controlling the galloping vibration of the transient main cables was studied. Results show that, to increase the 1st vertical vibration frequencies of the transient main cables, the assistant cables should be liad symmetrically and in the vertical direction and the frequency can be augmented through increasing the amount of the assistant cables and setting assistant cables in the middle of the bridge. To increase the diameter and amount of the assistant cables can improve the vibration of the transient main cables inside the plane. In the end, the computation show that the galloping instability for the long-span suspension bridge at construction stages can be controlled when the 11 ssistant cables groups are liad symmetrically and vertically at 12 qual division points of the suspension bridge and the assistant are made up of the reinforcing steel bar of 10mm diameters.7. The deterministic analysis of flutter for stiffening girders of long-span suspension bridges during construction can not meet the needs of actual situations and the probability analysis become the urgent problem to be solved. With a reference to some long-span suspension bridge, adopting the research methods of wind tunnel test and reliability analysis, the flutter reliabilities of stiffening girders for some long-span suspension bridge during construction were computed and meanwhile the effects of some factors on flutter reliability were investigated. Results show that the flutter stability is the worst at the construction early stages of the suspension bridge. There exists nonlinear relationship between the failure probability of flutter during construction and the design wind speeds, and the larger design wind speed is corresponding to the larger failure probability. The coefficients of variation have no effect on the failure probability. The increase of land surface roughness and the angle of attack results in the larger failure probability. It is dangerous for the initial construction to ignore the turbulent characteristics of wind and very conservative for the later construction. The flutter reliability of the non-symmetric construction for stiffening girders is better than that of the symmetric. It is more effective to increase the eccentric masses than to augment the eccentric distances for reducing the failure probability. In the end, the vertical cross suspenders can only increase the flutter reliability during later stages of construction for the symmetric construction of stiffening girders but reduce the flutter reliability during middle stages.更多还原