Alongwind static equivalent wind loads and responses of tall buildings. Part II: Effects of mode shapes

The reconsideration of the alongwind responses of tall buildings in part I is continued in the present paper. According to the literature to date, the effects of mode shape on the alongwind responses of tall buildings are taken to be negligible. In this paper, it is pointed out that only the effect of the first-mode displacement response has been included in the previous literature. Closed form expressions for the mode-shape correction are provided. The factor for the first-mode displacement response is in good agreement with that in the literature, and it can be neglected; but the factors for some other wind-induced responses, such as the base shear force, cannot be neglected. Finally a new correction procedure, which provides directly the static equivalent wind load, is developed.     

大跨度铁路站房屋盖结构风洞试验与等效静风荷载研究

以哈尔滨西客站站房屋盖结构为研究对象,采用刚性模型同步测压风洞试验对建筑表面的平均及脉动风荷载进行测定,结合本征正交分解技术对风压场进行重构及预测,解决了风压测点与结构有限元模型节点的不匹配问题。分别建立整体结构和屋盖结构有限元模型,利用时程分析方法考察了下部结构对风致响应的影响,研究表明下部结构会导致屋盖结构的刚度弱化,建模中忽略下部结构可能导致对屋盖结构位移和内力响应的低估。引入多目标等效静风荷载分析方法,以结构在风荷载作用下的最大动力响应为控制指标获得针对多个等效目标的静风荷载分布,并对等效结果进行了验证,结果表明该方法可以实现以少量静风荷载分布形式实现所有响应均与动力极值响应等效。     

高层建筑风荷载相干性研究

利用高层建筑刚性模型测压风洞试验结果,对顺风向风荷载竖向、水平相干性,迎背风面相干性以及横风向、扭转方向风荷载相干性的主要特征进行研究。利用算例说明了迎背风面相干性以及横-扭风荷载相干函数对于风振响应的影响。从计算结果来看,迎背风面全相干假定将使顺风向风振响应计算结果偏于保守;当结构刚心和质心偏离时,假定横扭风荷载相干性等于零会低估横风向和扭转方向风振响应。     

基于风洞试验的对称截面高层建筑三维等效静力风荷载研究

基于刚性模型表面测压风洞试验建立高层建筑三维风荷载模型,进而运用振型加速度法求解风振响应动力方程,得到了包含拟静力项和惯性力项的弹性力响应解,并推导了对称截面高层建筑顺风向、横风向和扭转向风致随机内力响应。在此基础上提出了基于内力响应等效的可考虑高阶振型贡献的对称截面高层建筑顺风向、横风向和扭转向等效静力风荷载计算方法。结合某一对称截面高层建筑工程实例,对采用上述方法计算得到的结构三维等效静力风荷载进行分析并与我国规范方法顺风向等效静力风荷载计算结果进行比较。结果表明,高层建筑结构抗风设计应该考虑三维等效静力风荷载,且二阶振型对高层建筑等效静力风荷载的贡献不可忽视。     

大跨空间结构的多目标等效静风荷载分析方法

针对大跨空间结构风荷载空间分布复杂、多振型参与结构风振以及等效静风荷载中存在多等效目标等特点,以作者提出的单目标(即等效目标)等效静风荷载分析方法为基础,提出多目标等效静风荷载的分析方法,该方法的基本思想是:根据结构风振响应特性,选择风荷载的主要本征模态和结构主导振型惯性力作为构造多目标等效静风荷载的基本向量;根据最小二乘法,得到基本向量的最优组合系数,从而得到针对多个等效目标的等效静风荷载。该分析方法的优点是:能够再现风振响应特点,又能解决工程中的多等效目标问题。最后,将该方法应用于一单层球面网壳,结果表明:一个等效静风荷载分布形式就可以实现某一类响应(如所有节点的位移)都与动力极值响应等效,验证了本文方法的有效性和精度。     

Multi-hazard loss analysis of tall buildings under wind and seismic loads

This paper presents a framework for life-cycle loss estimation for non-structural damage in tall buildings under wind and seismic loads. Life-cycle cost analysis is a useful design tool for decision- makers, aimed at predicting monetary losses over the lifetime of a structure, accounting for uncertainties involved in the problem definition. For tall buildings, sensitive to dynamic excitations like earthquake and wind, it can be particularly suitable to base design decisions not only on initial cost and performance but also on future repair expenses. The proposed approach harmonises the procedures for intervention costs evaluation of structures subjected to multiple-hazards, taking into account the peculiar differences of wind and earthquake, in terms of load characterisation, type and evolution of damage. Relative effect of the two hazards on damage to drift- and acceleration-sensitive non-structural elements are examined. The influence of uncertainty in structural damping is also taken into account. It is shown that, although it is commonly believed that the design of a given structure is usually dominated by either winds or earthquakes, when LCC-based design is performed, both winds and earthquakes may be important.     

基于Ritz-POD的大跨屋盖结构风振响应分析和风效应静力等效方法

大跨屋盖风振响应中的多振型参与特性,及由此导致的多目标等效静风荷载问题,一直是大跨屋盖结构风工程研究和工程应用十分关注的问题。对作者及合作者近年来在该方面的研究工作所取得的进展进行了总结,并加以发展。利用POD分解得到本征模态表达的脉动风荷载空间分布形式,确定与荷载分布形式对应的Ritz向量,即主导模态;推导脉动风响应中背景响应和共振响应的数学表达式,给出背景响应与共振响应间的相关性分析方法;根据结构风振响应特性,以风荷载主要本征模态和结构主导振型惯性力构造多目标等效静风荷载的基本向量,利用最小二乘法得到基本向量的最优组合系数,从而得到针对多个等效目标的等效静风荷载。并通过对跨度40m的K6型单层球面网壳结构的计算验证本文方法的有效性和准确性。     

大跨屋盖结构多目标等效静风荷载分析方法

针对大跨屋盖结构多振型参与风振的特点,提出一种多目标等效静风荷载确定方法。其基本思想是,分别建立多目标等效方程组和约束方程组,前者可获得与各等效目标吻合程度最好的解,后者是根据风荷载作用方向为垂直于建筑物表面的钝体空气动力学原理得到的风荷载各方向分量的关系,限制某些奇异荷载作用模式的出现,从而解决了大跨屋盖结构等效静风荷载研究中突出存在的多目标等效问题。结合两个典型大跨屋盖结构的风洞试验,对不同类型的结构响应进行了等效静风荷载分析,并将分析结果与采用单目标方法所得的结果进行对比,结果表明该方法得到的等效静风荷载作用下各类响应均与动力极值响应吻合良好,达到了以少量的等效静风荷载模式实现所有目标等效的目的,并且所得等效静风荷载分布较符合实际风荷载作用规律。     

基于利通广场的等效静力风荷载对比分析

目前计算高层建筑的方法主要有GLF法、IWL法和LRC法,但在具体工程中如何选用合适的方法,常是困扰结构工程师的问题.首先基于计算原理阐述了3种方法的特点,然后以广州珠江新城303m高的利通广场为例,对比了3种方法得到的等效静力风荷载分布和等效基底力.研究表明,GLF法和IWL法得到的等效静力风荷载分布形式近似,顺风向IWL法的值较大,而扭转方向GLF的值较大,LRC法得到的等效风荷载分布与以上两者完全不同,荷载取值偏于保守.LRC法得到的等效基底力也比其他方法高出约20%.     

多风向多目标等效静风荷载分析方法及应用

针对大跨空间结构中多振型参与风振响应特点和工程应用需要,提出针对多个风向的多目标等效静风荷载分析方法。根据所有风向的平均风荷载（或者风振响应极值）分布之间的相似性指标,将所有风向分为若干个风向区,计算各风向区的风振包络响应;在每个风向区内,选择平均风荷载分布和结构主导振型惯性力作为构造多目标等效静风荷载的基本向量,根据最小二乘法,得到基本向量的最优组合系数,从而得到针对多个风向、多个等效目标的等效静风荷载。将该方法用于某大型科技新馆,分析结果表明：根据各风向下屋面平均风压系数分布间的相关系数,36个风向角仅需分成3个风向区,且各风向区等效静风荷载作用下的静力响应与实际动力响应包络响应吻合较好,验证了所提方法的计算精度和工程应用的便利性。     

Distribution of background equivalent static wind load on high-rise buildings

In this paper, the along-wind and cross-wind fluctuating load distributions along the height of high-rise buildings and their correlations are obtained through simultaneous pressure measurements in a wind tunnel. Some typical methods proposed in some relative literatures, i.e., load-response correlation (LRC), and quasi-mean load (QML) and gust load envelope (GLE) methods, are verified in terms of their accuracy in describing the background equivalent static wind load distribution on high-rise buildings. Based on the results, formulae of the distribution of background equivalent static load on high-rise buildings with typical shapes are put forward. It is shown that these formulae are of high accuracy and practical use.     

Distribution of background equivalent static wind load on high-rise buildings

In this paper, the along-wind and cross-wind fluctuating load distributions along the height of high-rise buildings and their correlations are obtained through simultaneous pressure measurements in a wind tunnel. Some typical methods proposed in some relative literatures, i.e., load-response correlation (LRC), and quasi-mean load (QML) and gust load envelope (GLE) methods, are verified in terms of their accuracy in describing the background equivalent static wind load distribution on high-rise buildings. Based on the results, formulae of the distribution of background equivalent static load on high-rise buildings with typical shapes are put forward. It is shown that these formulae are of high accuracy and practical use. __________ Translated from Journal of Tongji University (Natural Science), 2008, 36(3): 285–290 [译自: 同济大学学报(自然科学版)]     

An experimental technique for distribution of dynamic wind loads on tall buildings

An experimental technique to determine the distribution of wind loads along the height of a slender and tall building has been presented using an aeroelastic model which simulates the correct mode shape of the prototype. The dynamic pressures acting on the model have been measured simultaneously from two pressure tappings at a time to compute the auto and cross power spectral densities, from which the modal force and, hence, the acceleration at any height is computed to determine the distribution of dynamic shear and moment. The technique could also be implemented using a rigid model when the motion of the building is not expected to modify the pressure distribution significantly. Since simultaneous measurements of pressures from all the tappings are not required, the proposed technique can be easily implemented in any wind tunnel laboratory.     

联体型双塔建筑静力风荷载的数值模拟

基于Fluent软件,采用雷诺应力模型RSM对六种不同体型的联体型双塔建筑物的静力风荷载进行了数值计算。研究了不同体型双塔间的静力干扰效应,顺、横风向和扭转方向的无量纲荷载系数等问题。分析表明,当风向角为0°且间距较近时,下游建筑位于上游建筑的尾流边界内,抑制了上游建筑尾流的发展,因此上游建筑的平均风荷载较单体时有所减小,而下游建筑的"遮挡效应"则非常显著。由于角部的处理,延缓了上游建筑气流的分离和再附,上游建筑的平均弯矩干扰因子IFm均小于尖角模型的相应值,而下游建筑的IFm均大于尖角模型的相应值。     

Across-wind loads of typical tall buildings

Previous studies have indicated that the across-wind dynamic responses of super-tall buildings are usually larger than the along-wind ones. With the increase of heights, the across-wind dynamic response of super-tall buildings has been a problem of great concern. In this paper, 15 typical tall building models are tested with high-frequency force balance technique in a wind tunnel to obtain the first-mode generalized across-wind dynamic forces. New formulas for the power spectra of the across-wind dynamic forces, the coefficients of base moment and shear force are then derived. Parametric analyses of the effects of factors on the across-wind loads of the buildings are performed. Besides, a SDOF aeroelastic model of a square tall building with an aspect ratio of 6 is selected from the above buildings and is tested to investigate its across-wind dynamic response and aerodynamic damping characteristics. The power spectrum of the across-wind force of the square building is employed to compute its across-wind dynamic responses with and without considering the effect of the aerodynamic damping. The computed responses are then compared with the corresponding responses from the aeroelastic model test to verify the present formulas of the across-wind loads of buildings.     

Wind‐induced inter‐story drift analysis and equivalent static wind load for multiple targets of tall buildings

In super high‐rise buildings with varying story heights, the wind‐induced inter‐story drifts might violate the specified limit. However, these effects have seldom been concerned in wind‐induced response analysis. The theory and application of equivalent static wind load (ESWL) for wind‐induced inter‐story drifts of super high‐rise buildings were studied in this paper. A spectral decomposition method suitable for multi‐point excitation problems was firstly proposed. The formula of ESWL targeting for largest inter‐story drift was derived. For more reasonable structural design, the ESWL for multiple targets including displacement atop of building and inter‐story drifts at all story levels is put forward, in which the dominant modal inertial forces are adopted as the based load vectors. The presented methods were finally verified by its application for the wind‐induced response analysis for a tallest super tall building in Guangzhou. The researched results showed that the proposed spectral decomposition method not only has the same precision as the complete quadratic combination method but also possesses higher computation efficiency. The ESWL for multiple targets produces the same static responses for all the specified wind‐induced response, so it is much more rational for wind‐resistant structural design. Meanwhile, it is more reasonable to select the wind‐induced responses in the same direction simultaneously as the targeted values for obtaining the required ESWLs; however, the ESWL targeting for the wind‐induced responses in all degrees of freedom would generate more queer and unrealistic ESWLs distribution. Copyright © 2015 John Wiley & Sons, Ltd.     

高层建筑的等效设计风荷载与风振响应研究

基于某典型高层建筑详细的风洞试验结果,计算分析了该结构的基础等效静风荷载及结构顶部峰值加速度响应,与前期的风洞试验结果相对比,评估了不同风洞试验条件和周边建筑对试验结果的影响,获得的结果可以用于此结构的抗风设计以及居住者舒适度评估。     

Effects of tuned mass damper on correlation of wind‐induced responses and combination coefficients of equivalent static wind loads of high‐rise buildings

Tuned mass dampers (TMDs) are employed to control the wind‐induced responses of tall buildings. In the meantime, TMD may have an impact on the correlation of wind‐induced responses and combination coefficients of equivalent static wind loads (ESWLs). First, the mass matrix and stiffness matrix were extracted in this paper in accordance with the structural analysis model of two high‐rise buildings, and on that basis, the wind‐induced vibration responses analysis model with and without TMD was established. Second, the synchronous multipoint wind tunnel test to measure the pressure was performed for two high‐rise buildings, and the time history of wind‐induced vibration responses with and without TMD was studied. Finally, the impact of TMD on the correlation of wind‐induced responses and combination coefficients of ESWLs was discussed. The results of two examples suggest that after the installation of TMD, the increase of ρ_xy was 2.1% to 35.0% and ρ_yz was 2.8% to 45.6% at all wind directions for Building 1, and the increase of ρ_xy was 3.9% to 17.1% and ρ_yz was 6.8% to 38.3% for Building 2. The combination coefficients of ESWLs of two buildings were 3% to 6% larger than that of the original structure. The conclusion of this paper can be referenced by the wind resistant design of high‐rise buildings with TMD.     

错列布置超高层建筑群的干扰效应研究

对实际超高层建筑群进行群体和单体塔楼两次同步测压风洞试验。通过两次试验测量结果,考察风向及塔楼位置对顺风向、横风向和扭转方向的主体结构承受风荷载以及围护结构的极值风压的影响,并结合风压试验结果及CFD流场计算结果对干扰机理进行说明。研究结果表明,处于中间位置的2号塔楼的扭转干扰放大作用非常显著,较为不利的风向为110°风向,该风向下扭转方向的静力干扰因子达到1.53;沿弱轴Y方向和扭转方向的动力放大因子达到1.32和1.37。