模态综合理论在斜拉桥抖振时域分析中的应用

在桥梁随机风场数值模拟的基础上,提出一种斜拉桥抖振时域分析的模态综合方法,建立了斜拉桥时域抖振分析计算模型.该方法简化了自激力时域化过程,并在计算中全面考虑了气动阻尼、气动刚度和气动耦合作用的影响,提高了斜拉桥抖振时域分析的效率.通过对一座大跨斜拉桥的抖振时域分析,验证了方法的正确性和可行性.     

桥梁抖振反应谱的实用计算方法

以R.H.Scanlan抖振理论为框架,并引入了气动导纳函数予以修正,给出了大跨桥梁抖振反应谱理论的基本公式.通过比较详细的参数分析,给出了类似于地震反应谱分析的抖振反应谱实用计算方法.最后,以汕头海湾悬索桥和上海杨浦斜拉桥为例,进行了工程实例分析,结果表明:与精确分析方法相比,抖振反应谱实用计算方法有足够的精度.     

桥塔自立状态下抗风性能的比较研究

首先介绍了桥塔的材料及其构造形式,列表说明了目前大跨度悬索桥以及斜拉桥在桥塔的材料、构造形式以及塔高等方面的选取;阐述了桥塔在自立状态下可能发生的风致振动,包括抖振、驰振以及涡激共振;分析了某大桥桥塔在自立状态下风洞模型试验的现象及其结果,并且与其他桥塔在自立状态下风洞模型试验结果相比较,根据它们各自材料与构造形式所决定的不同气动特性作出分析,得出了一些有意义的结论;最后提出有效的减振对策.     

地基变形对斜拉桥施工双悬臂结构风致抖振反应的影响

探讨了地基变形对桥塔沉井基础位于土层之中的斜拉桥施工双悬臂结构风致抖振反应的影响。在建立了桥塔沉井基础位于土层之中的斜拉桥施工双悬壁结构考虑地基变形的风致抖振反应分析方法的基础上，以海口世纪大桥为工程背景计算分析了地基变形对结构风致抖振反应的影响，得出了地基变形对施工双悬臂结构风致抖振位移反应影响较大，而对桥塔根部纵向抖振弯矩反应影响不大的重要结论。     

大型斜拉桥风致振动机理及分析方法

本文从空气作用力引起斜拉桥各种风致振动的机理出发,探讨斜拉桥颤振、驰振、涡激振动、抖振的分析方法,为大型斜拉桥空气动力稳定性分析提供参考。     

开槽断面斜拉桥的随机抖振数值分析

以中央开槽箱梁断面斜拉桥-上海长江大桥为工程背景,首先通过格栅紊流场节段模型测力和测压风洞试验,研究了中央开槽箱梁断面的非定常随机抖振力频谱特性和跨向相关特性;然后,借助于最小二乘拟合方法,提出了同时考虑来流紊流和特征紊流的中央开槽箱梁断面的非定常随机抖振力谱经验数学模型和抖振力跨向根方相干函数经验数学模型;其次在此基础上,建立了开槽断面斜拉桥的非定常随机抖振响应有限元频域数值分析方法,并应用于上海长江大桥的非定常随机抖振响应分析;最后,把数值分析结果与气弹模型风洞试验结果进行了对比,以检验所建立方法的可行性和可靠性。     

悬索桥抖振分析中计入背景分量的实用方法

Scanlan方法是目前大跨桥梁抖振分析的常用方法.从应用角度出发,该方法计算抖振时仅计入了抖振的共振分量,而忽略了其背景分量.作者在对多座斜拉桥、悬索桥分析的基础上,认为对于日趋轻柔的大跨桥梁而言,考虑背景分量是必要的.本文着重对悬索桥的抖振背景分量情况作一分析,并提出了一种计入背景分量的抖振计算实用方法.     

钢管-钢管混凝土复合桥塔抗风性能试验研究

采用钢管-钢管混凝土复合桥塔可减轻桥塔自重,设计出更轻盈多样的结构造型,为分析桥塔抗风自立状态的抗风性能,采用MIDAS软件对该桥塔进行了抗风性能数值分析,并制作1:100的缩尺气弹模型进行风洞试验,研究桥塔的涡振、驰振和抖振响应.结果表明:在该桥塔自立状态风洞试验中未发现明显的涡振和驰振现象,紊流场中桥塔抖振响应也很...     

钢-混叠合梁非对称独塔斜拉桥风致响应性能研究

为了研究钢-混叠合梁非对称独塔斜拉桥的抗风性能,文章以某主跨200 m的斜拉桥为背景,通过节段模型风洞试验测试了断面在成桥态和施工态下的颤振临界风速和颤振导数,采用三维颤振分析方法计算了断面的颤振临界风速,最后采用CQC抖振分析方法计算了该桥的抖振位移响应。结果表明:三维颤振分析与风洞试验得出的颤振临界风速均远大于颤振检验风速,表明桥梁具有良好的颤振稳定性;断面在成桥态和施工态下的抖振响应很小,且最大抖振位移对应的峰值加速度满足舒适度要求。     

模态间气动耦合效应对调谐质量阻尼器最优参数的影响

基于多模态耦合抖振理论,导出带有被动调谐质量阻尼器(TMD)的桥梁多模态耦合抖振系统运动微分方程,采用随机振动理论求解系统运动微分方程,并编制了桥梁多模态耦合抖振TMD控制和参数分析程序。以一座斜拉桥为算例,着重分析了模态间气动耦合效应对TMD最优参数和控制效率的影响。     

三塔斜拉桥不同位置设置A形索塔的刚度分析

简述了三塔斜拉桥提高刚度的方法,提出A形索塔对提高三塔斜拉桥刚度的重要作用,用midas civil建立主跨为360 m的三塔斜拉桥模型,对索塔采用普通索塔、中塔A形索塔、边塔A形索塔和全部采用A形索塔的活载竖向挠度进行对比分析,得出A形索塔设置在三塔斜拉桥的不同位置对提高结构刚度的影响。     

独塔双索面双跨式斜拉桥主塔施工技术

斜拉桥是将主梁用许多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。文章介绍了徐葛大桥独塔双索面双跨式预应力混凝土斜拉桥索塔施工方案,索塔施工采用的主要设备和施工中采用的新工艺、新技术。     

矮塔斜拉桥主梁施工技术

结合某大桥施工实际,介绍了矮塔斜拉桥索塔和主梁设计,并从支撑体系的布置和模板支设要点控制矮塔斜拉桥主梁的施工,为以后矮塔斜拉桥施工提供了一定指导。     

Safety and serviceability assessment for high-rise tower crane to turbulent winds

Tower cranes are commonly used facilities for the construction of high-rise structures. To ensure their workability, it is very important to analyze their response and evaluate their condition under extreme conditions. This paper proposes a general scheme for safety and serviceability assessment of high-rise tower crane to turbulent winds based on time domain buffeting response analysis. Spatially correlated wind velocity field at the location of the tower crane was first simulated using an algorithm for generating the time domain samples of a stationary, multivariate stochastic process according to some prescribed spectral density matrix. The buffeting forces applied to the structure were computed according to the above-simulated wind velocity fluctuations and the lift, drag, and moment coefficients obtained from a CFD computation. Those spatially correlated loads were then fed into a well calibrated finite element model and the nonlinear time history analysis was conducted to compute structural buffeting response. Compared with structural onsite response measurement, the computed response using the proposed method has good precision. The proposed method is then adopted for analyzing the buffeting response of an in-use tower crane under the design wind speed and the maximum operational wind speed for safety and serviceability assessment.     

三官汉江矮塔斜拉桥索塔节段模型试验研究

通过有限元分析与索塔模型试验相结合的方法,对武汉市三官汉江公路矮塔斜拉桥索的塔锚固区进行受力分析及验证索塔锚固区带单侧双向抗滑装置的静载抗滑性能研究,通过试验模拟实桥运营阶段的单根钢绞线换索过程,为设计和施工提供技术支持。试验结果表明,该桥索塔锚固区结构受力安全、索塔锚固区抗滑构造及单根钢绞线换索工艺满足设计和规范要求。     

金马大桥抖振响应的时域分析

金马大桥是一座独塔斜拉桥与两侧T构相连接的大跨度协作体系桥梁,该桥结构形式新颖且桥位处于台风多发区,因此,对该桥进行抖振响应分析是非常必要的。首先利用谐波合成法将脉动风速模拟为多个互相关的随机过程,接着给出抖振力和自激力的时域表达式,据此对金马大桥进行了抖振响应分析。结果表明,尽管该协作体系斜拉桥采用抗扭能力较差的边主梁形式,但其抗风能力是有保证的。     

Parametric study on buffeting performance of a long-span triple-tower suspension bridge

The triple-tower suspension bridge is a brand new type of structural form that is equipped with a dominant mid-tower. The dynamic characteristics of this multiple main-span suspension bridge present a significant difference with that of the conventional single main-span suspension bridge. Hence, taking the Taizhou Yangtze River Bridge as an example, the buffeting performance of a long-span triple-tower suspension bridge under strong winds is comprehensively investigated via finite element method. Specifically, the sensitivity of structural buffeting performance to some major structural parameters, aerodynamic parameters as well as parameters of turbulence inputs is analysed in time domain. It was found that the structural buffeting performance heavily depends on the dead load of the main girder, sag-to-span ratio of the main cable, longitudinal stiffness and structural type of the mid-tower. Also, appropriate selection of aerodynamic admittance function, power spectrum model of fluctuating wind and the spatial coherence coefficient is important in the buffeting analysis. Besides, the self-excited forces have small impact on the calculation of buffeting responses of such a bridge. The analytical results can provide references for the buffeting analyses and wind-resistant design of similar long-span triple-tower suspension bridges.     

不对称斜塔斜拉桥的受力和设计分析研究

斜塔斜拉桥是一种概念较新的桥梁结构形式,其独特之处在于倾斜的桥塔、轻盈的主梁、优美的外形,但是结构的不对称性导致其受力复杂、施工难度大。本文结合一有背索、跨径不对称、拉索不对称的斜拉桥的工程实例,通过对其静力力学模型分析,可知此类斜拉桥既要关注桥梁的整体平衡,也要关注主梁、主塔结构的局部平衡。通过对张拉索力和施工阶段分析的总结,可知刚性支撑连续梁法初估索力时只顾及了梁的受力,而忽略了塔的受力,要结合主梁、主塔的平衡条件对成桥索力进行调整才能得到合理的成桥状态。通过主塔、主梁的设计分析,得出桥梁的预应力布置、主梁截面形式、拉索的施工步序应依据施工阶段分析中主梁与主塔的受力情况最终确定。该桥目前已施工完毕,该桥的设计经验可以为同类桥梁的设计与施工提供参考。     

Simulation of support settlement and cable slippage by using a long-span suspension bridge testbed

Support settlement and cable slippage of a long-span suspension bridge may occur when it is subjected to extreme events. The evaluation of effects of support settlement and cable slippage on the remaining capacity then becomes important before making a retrofitting decision. However, it is difficult to conduct such an evaluation on the prototype bridge. This paper therefore presents experimental and numerical studies to examine the effects of support settlement and cable slippage on the structural performance of a long-span suspension bridge through a testbed, which include a laboratory-based model and an updated finite-element (FE) model. Four support settlement cases are experimentally studied with two on anchorage settlements and two on tower settlements. Main cable slippage at the top of towers is then investigated experimentally in two opposite directions. Both support settlement cases and cable slippage cases are also simulated using the corresponding FE model, and results are compared with those from the tests. Finally, numerical studies are conducted to investigate cable slippage caused by large support settlement. The results show that the experimental and numerical simulation using the testbed is an effective way to assess the effects of support settlement and cable slippage on long-span suspension bridges.