Three‐dimensional coupled wind‐induced vibration calculation method for super high‐rise buildings based on high‐frequency force balance technology

High‐frequency force balance test is a major technical means to evaluate the wind effect of super high‐rise buildings. Most super high‐rise buildings have the characteristic that the first two‐order modal frequencies are close, and thus, considerable modal coupling effects (MCEs) may occur under wind load. For a balance model system (BMS), MCEs increase the difficulty of correcting aerodynamic distortion signals. For the wind‐induced vibration analysis of a structural system (PSS), the calculation results of the wind‐induced response and the equivalent static wind load (ESWL) may be significantly affected without considering MCE. Based on the above‐mentioned signal distortion of BMS and the modal coupling problem of PSS, this study proposes a wind‐induced vibration calculation method for the two coupled systems (BMS and PSS). The method uses the second‐order blind identification technique based on complex modal theory and the Bayesian spectral density method considering full aerodynamic characteristics to achieve effective correction of the distortion signal in BMS. In addition, it deduces the calculation method of the wind‐induced response and ESWL considering the three‐dimensional coupled vibration of a super high‐rise building. The wind effect calculation results of a 528‐m super high‐rise building confirm the necessity and effectiveness of the proposed method.     

Wind effect of a twin‐tower super high‐rise building with weak connection

An analysis and estimation method of multibalance synchronous test is established to study the wind effect of a complex super high‐rise building with weak connection. First, the frequency domain method is applied to deduce the calculation process of the wind effect of the multitower structure on the basis of the high frequency force balance (HFFB) technique. Then, the synchronous force test of HFFB is conducted on a twin‐tower super high‐rise building connected by a bridge. The wind‐induced response and loads and the interference effect between the two towers are analyzed based on the wind tunnel test data. The displacement correlation between the towers and the relative displacement of the multitower structure are investigated. Results show that the maximum and minimum relative displacements in the along‐bridge direction are 0.26 m in the along‐wind direction and ?0.26 m in the crosswind direction, respectively. The channeling effect formed by the surrounding buildings is the main cause of the maximum cross‐bridge displacement. The influence of the correlation between the two towers can be ignored for the along‐bridge relative displacement. The results of the HFFB and high‐frequency pressure integral test agree with each other, thereby indicating the reliability and effectiveness of the proposed method.     

Effects of grid curtains on the wind loads of a high‐rise building

The effects of grid curtains on the local and overall wind loads of a high‐rise building are investigated in detail according to a series of wind pressure and wind force tests on rigid model in a wind tunnel. The effects of grid curtains on the mean and fluctuating wind pressures on windward and sideward walls when the wind direction is parallel to the geometrical axes are investigated, along with the effects of the most unfavorable wind pressures for all wind directions. Furthermore, the effects of grid curtains on the mean and fluctuating aerodynamic forces on the entire building are also analyzed for various wind directions, along with the effects of grid curtains on the aerodynamic force spectra when the wind direction is parallel to the geometric axes. The test results indicate that grid curtains affect the mean and fluctuating windward pressure slightly but greatly influence the large sideward negative pressures. Grid curtains increase the mean and fluctuating windward aerodynamic forces and reduce the fluctuating aerodynamic torsions. According to the aerodynamic force spectra, grid curtains can mainly affect the wind forces in the low‐frequency range. Copyright © 2015 John Wiley & Sons, Ltd.     

An experimental study on the wind pressure distribution of tapered super high‐rise buildings

Studies on the effect of different shape strategies on wind‐induced responses of super tall buildings have been extensive. However, little systematic research on the influence of aerodynamic shapes on wind pressure distributions of super high‐rise building having a height more than 500 m is reported in the literature. In this paper, a series of wind tunnel tests are conducted on models simulating tapered buildings taller than 500 m with an aspect ratio of 9:1 by applying synchronous pressure measurement technology to investigate the influence of different shape strategies on the wind force coefficients of the cross section (C_s) and on the peak negative pressure distributions on surfaces. The shape strategies considered include tapering of the cross section of a building along its height, chamfered modification, and opening ventilation slots. It is found that the wind force coefficient C_s increase with an increase of the tapering ratio. It is shown that chamfered modification can effectively reduce most of the wind force coefficients C_s to less than 0.9. As for peak wind pressures, a zone having a higher negative pressure is found to locate at the bottom of the side faces of the model. With an increase of the tapering ratio, the peak negative pressure of side faces of the model slightly decreases. Chamfered modification can significantly increase the peak negative pressure at the chamfered location. Furthermore, it is demonstrated that opening ventilation slots had less effect on C_s, but the peak negative pressure can significantly increase at the area of opening ventilation slots and adjacent areas.     

Experimental study on wind load characteristics of high‐rise buildings with opening

For investigation of the wind load characteristics on high‐rise buildings with opening, a series of rigid rectangular high‐rise building models with opening were tested by synchronous multi‐pressure sensing system (SMPSS) in a boundary wind tunnel. Influence parameters including different opening heights, opening rates, opening patterns, and terrain categories are studied in detail. Based on the test results, the local wind force coefficients, base moment coefficients, and power spectral densities were discussed. The results indicated that the opening could affect the wind loads acting on high‐rise buildings to different extent. The distinct reduction of wind loads on high‐rise buildings was found at along‐wind direction, which could be evaluated by a proposed simplified expression accordingly. This study aims to provide useful information for the wind‐resistant design of high‐rise buildings with opening.     

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.     

Peak factor estimation of non‐Gaussian wind pressure on high‐rise buildings

A vast quantity of measurements of wind‐induced non‐Gaussian effects on buildings call for the burgeoning development of more advanced extrema estimation approaches for non‐Gaussian processes. In this study, a well‐directed method for estimating the peak factor and modeling the extrema distribution for non‐Gaussian processes is proposed. This method is characterized by using two fitted probability distributions of the parent non‐Gaussian process to separately fulfill the estimations of the extrema on long‐tail and short‐tail sides. In this method, the Johnson transformation is adopted to be the probabilistic model for fitting the parent distribution of the non‐Gaussian process due to its superior fitting goodness and universality. For each dataset, two Johnson transformations will be established by two parameter estimation methods to individually estimate the extrema on two sides. Then a Gumbel assumption is applied for conveniently determining the non‐Gaussian peak factor. This method is validated through long‐duration wind pressure records measured on the model surfaces of a high‐rise building in wind tunnel test. The results show that the proposed method is more accurate and robust than many existing ones in estimating peak factors for non‐Gaussian wind pressures.     

Evaluation of wind loads on super‐tall buildings from field‐measured wind‐induced acceleration response

With the nonstationary wind‐induced acceleration data from full‐scale measurements, an approach for estimation of the wind‐induced overturning bending moments for super‐tall buildings was proposed in this paper. The empirical mode decomposition was employed to decompose the measured acceleration data into a set of intrinsic mode functions and a residual component. To remove the baseline offset, the residual component and the intrinsic mode function components with long‐period were eliminated before their integrations into velocity and displacement components. Then, the intrinsic mode function components, which have the same dominant periods as the natural periods of the studied tall buildings, were extracted from the original signals, and the natural frequency and damping ratio for the first vibration mode of the building were identified. Finally, the wind‐induced overturning bending moments of the building were obtained from the generalized wind loads for the first vibration mode, which could be obtained from the time history analysis of dynamic equation. The Hilbert spectrum of wind‐induced overturning bending moments was utilized to observe its characteristics in both time and frequency domains, and the Strouhal number was thus identified. The proposed scheme and some selected results may be helpful for further understanding of wind effects on super‐tall buildings. Copyright © 2012 John Wiley & Sons, Ltd.     

Steady suction for controlling across‐wind loading of high‐rise buildings

To reduce across‐wind effects on high‐rise buildings, this paper introduces a new active aerodynamic control named steady suction. To test its effect, the control mechanism of steady suction is discussed first, and then, a synchronization pressure test was conducted in a wind tunnel to measure the across‐wind loading on a high‐rise model (Commonwealth Advisory Aeronautical Research Council standard high‐rise building model). A series of analytical methods were used to compare the different effects on across‐wind aerodynamic forces caused by different parameters. The results show that when the wind blows straight on the wide side of the model, steady suction arranged on the narrow side close to the leading edge can effectively reduce the fluctuating base moment. When the wind blows straight on the narrow side, steady suction arranged on the middle of the wide side effectively reduces the fluctuating base moment. Copyright © 2016 John Wiley & Sons, Ltd.     

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.     

Aerodynamic interference effects of a proposed taller high‐rise building on wind pressures on existing tall buildings

When a large super high‐rise building taller than the surrounding tall buildings is built in a dense urban area, the aerodynamic interference effects of the surrounding buildings on the proposed building attract much attention, while the interference effects of the taller high‐rise building on the nearby existing buildings are often ignored. Based on a series of wind tunnel tests, the interference effects of a proposed taller high‐rise building, an adjacent equal‐height partner building, and relatively short background buildings on the target building's local wind pressures are analysed in this paper. Two‐dimensional numerical simulation are carried out to further understand the interference mechanism in some cases. The test results show that the influence of a nearby proposed taller high‐rise building may lead to wind‐induced damage on the interfered shorter buildings' envelopes. The envelope structures of other surrounding buildings facing the side of the proposed building need to be given more attention.     

Experimental study of across‐wind aerodynamic damping of super high‐rise buildings with aerodynamically modified square cross‐sections

Across‐wind aerodynamic damping ratios are determined from the wind‐induced acceleration responses of 10 aeroelastic models of square super high‐rise buildings in an urban flow condition (exposure category C in the Chinese code) using the random decrement technique. Moreover, the influences of amplitude‐dependent structural damping ratio on the estimation of aerodynamic damping ratio are discussed. The validity of estimated damping is examined through a comparison with previous research achievements. On the basis of the estimated results, the characteristics of the across‐wind aerodynamic damping ratios of modified square high‐rise buildings are studied. The effects of aerodynamically modified cross‐sections, such as chamfered, slotted and tapered cross‐section, on the across‐wind aerodynamic damping ratio are investigated. The results indicate that modifications of cross‐sections are not always effective in suppressing the aeroelastic effects of super high‐rise buildings. Low corner‐cut ratios (chamfer ratios from 5% to 20% and slot ratios from 5% to 10%) and low taper ratio (1%) significantly decrease the magnitudes of absolute aerodynamic damping ratios. However, large modifications of cross‐sections (slot ratio of 20% and taper ratios from 3% to 5%) increase wind‐induced responses by changing the aerodynamic damping ratios. According to the database, empirical aerodynamic damping function parameters are fitted for high‐rise buildings with aerodynamically modified square cross‐sections. Copyright © 2013 John Wiley & Sons, Ltd.     

Optimal parameters for tall buildings with a single viscously damped outrigger considering earthquake and wind loads

Tall buildings suffer from low inherent damping and high flexibility. Therefore, a core-outrigger system is often used to stiffen such buildings. A modified form, known as the damped outrigger system, wherein vertically oriented dampers are installed between outriggers and perimeter columns, has been recently developed to supplement the damping. This paper studies the efficacy of a viscously damped outrigger system through dynamic analysis of a 60-story tall building subjected to nonconcurrent earthquake and wind excitations. Two ground motion sets (100 accelerograms) are used for the former and wind tunnel test data for the latter. Effects of three building parameters, namely, (i) the core-to-column stiffness ratio, (ii) the outrigger location, and (iii) the damper size, on the dynamic characteristics and seismic and wind responses are evaluated. Effects of damper nonlinearity on seismic and wind responses are also investigated considering energy-equivalent nonlinear viscous dampers. Finally, the optimum values of these parameters are determined. For example, the optimum outrigger location is found to be between $0.6H$ to $0.9H$, where $H$ is the height of the building. The results also show that the damped outrigger system significantly outperforms the conventional one for seismic excitation, and it is very effective in reducing the wind-induced floor accelerations, provided the parameters are chosen appropriately.     

深圳京基金融中心气动抗风措施试验研究

深圳京基金融中心高439m,风荷载是该超高层建筑的控制荷载。采用高频底座力天平方法对该建筑模型进行了风洞试验,考察了利用其顶部设备和避难层进行开敞形成不同的风走廊(气动措施)对结构风荷载和风致响应的影响。试验结果表明：在重现期100a敏感风向作用下结构漩涡脱落频率明显低于结构基阶固有频率;气动措施可显著抑制和削弱脱落漩涡的强度,当没有受到明显干扰影响时,气动措施显示出良好的抗风效果。不同气动措施可使重现期100a结构基底弯矩减少8.2%~21.2%,使重现期10a峰值加速度减少5.3%~16.0%;受到来自于地王大厦的干扰效应的影响,在所关注重现期风速范围内的结构风振响应为上游地王大厦的尾流所控制,影响了气动措施的控制效果,但在发生涡激共振的临界风速时气动控制措施效果显著。     

Wind‐induced torsion vibration of the super high‐rise building of Shenzhen Energy Center

The synchronous multipoint scanning system technique in wind tunnel tests and random vibration theory method were used to analyze the wind‐induced torsion vibration of some irregularly shaped super high‐rise buildings in downtowns. The torsion vibration modes and the spectra of torsion wind load were studied, and the proportions of mean wind torsion, inertia torsion and the mass eccentricity torsion caused by horizontal inertia forces are discussed. The following conclusions can be drawn. First, the third and fourth modes have torsion vibration shapes, and their frequencies are in the high‐energy area of the spectra of the torsion wind load; the third and fourth modes are included in the resonant component of the spectra of the top torsion angle of the building, and the third mode is dominant. Second, the torsion stiffness is weak in the high stories of the building, so the inertia torsion is dominant, whereas the torsion stiffness is strong in the low stories; the mean wind torsion is dominant. The proportion of the mass eccentricity torsion moment caused by horizontal inertia forces is small. Finally, the wind‐induced torsion moment at a 90° wind angle is the largest, whereas the torsion eccentricity is 46% of the radius of gyration and is much greater than the mass eccentricity; thus, the wind‐induced torsion should be considered. The wind‐induced torsion vibration of the building is sensitive to wind directions. Copyright © 2011 John Wiley & Sons, Ltd.     

Approximate method of estimating seismic performance of high‐rise buildings with oil‐dampers

When subjected to long‐period ground motions, many existing high‐rise buildings constructed on plains with soft, deep sediment layers experience severe lateral deflection, caused by the resonance between the long‐period natural frequency of the building and the long‐period ground motions, even if they are far from the epicenter. This was the case for a number of buildings in Tokyo, Nagoya, and Osaka affected by the ground motions produced by the 2011 off the Pacific coast of Tohoku earthquake in Japan. Oil‐dampers are commonly used to improve the seismic performance of existing high‐rise buildings subjected to long‐period ground motion. This paper proposes a simple but accurate analytical method of predicting the seismic performance of high‐rise buildings retrofitted with oil‐dampers installed inside and/or outside of the frames. The method extends the authors' previous one‐dimensional theory to a more general method that is applicable to buildings with internal and external oil‐dampers installed in an arbitrary story. The accuracy of the proposed method is demonstrated through numerical calculations using a model of a high‐rise building with and without internal and external oil‐dampers. The proposed method is effective in the preliminary stages of improving the seismic performance of high‐rise buildings.     

Dynamic wind response of tall buildings using artificial neural network

This paper presents an alternative approach for predicting the dynamic wind response of tall buildings using artificial neural network (ANN). The ANN model was developed, trained, and validated based on the data generated in the context of Indian Wind Code (IWC), IS 875 (Part 3):2015. According to the IWC, dynamic wind responses can be calculated for a specific configuration of buildings. The dynamic wind loads and their corresponding responses of structures other than the specified configurations in IWC have to be estimated by wind tunnel tests or computational techniques, which are expensive and time intensive. Alternatively, ANN is an efficient and economical computational analysis tool that can be implemented to estimate the dynamic wind response of a building. In this paper, ANN models were developed to predict base shear and base bending moment of a tall building in along‐ and across‐wind direction by giving the input as the configuration of the building, wind velocity, and terrain category. Multilayer perceptron ANN models with back‐propagation training algorithm was adopted. On comparison of results, it was found that the predicted values obtained from the ANN models and the calculated responses acquired using IWC standards are almost similar. Using the best fit model of ANN, an extensive parametric study was performed to predict the dynamic wind response of tall buildings for the configurations on which IWC is silent. Based on the results obtained from this study, design charts are developed for the prediction of dynamic wind response of tall buildings.     

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。     

地貌对高层建筑(群)风效应影响数值分析

高层建筑(群)风效应与地貌条件相关,分析掌握其内在关系是建筑布局规划和抗风设计的重要前提。基于雷诺时均模拟方法(RANS),引入具有分离流预测优势的SST k-ω湍流模型,以某高层建筑单体及群体风场为对象,模拟4类地貌条件下的风效应场,侧重分析人行高度(2m)风速场以及建筑立面的风压分布特性。分析结果表明,地貌除对人行高度的风速场影响明显外,对高层建筑表面风压系数影响也较为可观,实际工程应适当考虑地貌效应。     

高层建筑结构的风振阻尼控制分析与设计方法

本文首先分析了阻尼比对结构风振反应的控制效果,重点讨论了阻尼比对风振脉动增大系数的减小效果和具体计算方法,给出了便于工程实际应用的阻尼比为10%～30%的风振脉动增大系数随基本风压和结构基本周期变化的计算图表。结果表明,结构阻尼比增大,风振脉动增大系数明显减小。其次,分析了结构耗能减振系统的附加阻尼特性,给出了调频质量阻尼器(TMD)、调频液体阻尼器(TLD)和速度线性相关型耗能器附加给结构阻尼比的实用计算公式。最后给出了100层钢结构分别设置TMD和线性粘滞阻尼器的风振控制分析和设计实例。实例结果表明,两种被动阻尼控制系统对结构最大位移和最大加速度控制效果相同,可以达到40%～55%,同时说明了本文提出的方法可以方便地用于大型结构的风振阻尼控制分析和设计。