超高层建筑风荷载的试验研究

超高层建筑的风致振动是结构设计的主要控制因素之一。但目前对横风向风荷载的研究远不能满足工程应用和规范制定的需要。本文应用高频动态测力天平技术,对常见的１３种典型断面的超高层建筑模型进行了不同风场条件下的风洞试验,研究了其风荷载,特别是横风向风荷载。结果表明,外形和风场对风荷载有很大的影响,而长细比对无量纲风荷载的影响甚微。本文最后给出的一阶横风向广义风力系数谱的拟合公式,可供规范修订参考。     

基于大涡模拟的三维高层建筑结构气弹响应数值模拟

以宽高比为1∶6的方形截面高层建筑为研究对象,采用弱耦合分区交错算法,流体域采用大涡模拟方法,进行了紊流边界层风场内三维高层建筑结构多自由度模型的气弹数值模拟,计算中考虑了来流紊流,以及结构的顺、横风向响应。将结构静止时大涡模拟结果与刚性模型测压风洞试验进行比较,验证了该方法在准确预测结构风荷载方面的可行性。通过与气弹模型风洞试验结果的比较表明,本文数值分析方法可用于求解风与结构的相互作用,且具有较高的精度。进行了高折减风速下的气弹数值模拟,研究了结构顶部顺、横风向位移响应随折减风速的变化规律。结果表明：结构风振气弹响应主要为来流紊流引起的顺风向抖振和旋涡脱落引起的横风向涡激振动;折减风速较小时,结构顺、横风向位移振幅相当,且位移响应均相对较小;随着折减风速的增加,结构位移响应增大,横风向涡激振动逐渐占据主导地位,并经历了从“拍”到“涡激共振”的转化。     

矩形截面高层建筑的横风向基底弯矩系数均方根值研究

利用高频天平技术,在4种不同风场中对71种不同外形尺寸的矩形截面高层建筑刚性模型进行风洞试验,测得高层建筑横风向基底弯矩系数,考察建筑厚宽比、长细比及所处风场类型对高层建筑横风向基底弯矩系数均方根值的影响。试验结果表明,厚宽比的影响效果最显著,长细比的影响可以忽略不计,风场类型的影响随着厚宽比的不同而不同。基于这些风洞试验数据,给出基底弯矩系数均方根值的拟合公式并对拟合公式进行误差分析,通过与国内外相关研究成果的比较,验证拟合公式的精度与合理性,可以为荷载规范的修订和补充提供很好的参考。     

高层建筑的横风向激励特性和计算模型的研究

将高层建筑的横风向激励分解为横风向紊流和涡激力激励。根据10个典型高层建筑模型的风洞试验结果,分别研究了两种激励的特性和计算模型,给出典型建筑的横风向紊流激励力系数、涡激力系数和相应的形状系数。特别着重研究涡激力功率谱函数和相干函数,总结出的结果可加深对高层建筑横风向荷载特性的认识,所建立的典型高层建筑的横风向荷载计算模型可用于实际工程。     

Control of wind-induced vibration of long-span bridges and tall buildings

With the rapid increase in scales of structures, research on controlling wind-induced vibration of large-scale structures, such as long-span bridges and super-tall buildings, has been an issue of great concern. For wind-induced vibration of large-scale structures, vibration frequencies and damping modes vary with wind speed. Passive, semiactive, and active control strategies are developed to improve the wind-resistance performance of the structures in this paper. The multiple tuned mass damper (MTMD) system is applied to control vertical bending buffeting response. A new semiactive lever-type tuned mass damper (TMD) with an adjustable frequency is proposed to control vertical bending buffeting and torsional buffeting and flutter in the whole velocity range of bridge decks. A control strategy named sinusoidal reference strategy is developed for adaptive control of wind-induced vibration of super-tall buildings. Multiple degrees of freedom general building aeroelastic model with a square cross-section is tested in a wind tunnel. The results demonstrate that the proposed strategies can reduce vibration effectively, and can adapt to wind-induced vibration control of large-scale structures in the uncertain dynamic circumstance.     

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。     

Characteristics of aerodynamic forces and pressures on square plan buildings with height variations

Many studies on reducing across-wind responses of tall buildings have been investigated, mainly focusing on the effect of corner shape. And it is also known that changing section along the height through tapering or set-back could reduce across-wind responses of tall buildings. In this paper, to investigate the mechanism of aerodynamic force reduction, the wind tunnel tests for fluctuating pressure and fluctuating force were carried out. Two models with different tapering ratio of 5% and 10%, one set-backed model and one prototype square prism with side ratio of unity were employed under two typical boundary layers which represent suburban and urban flow condition. It is concluded that tapering or set-back helps to reduce the mean drag force and the fluctuating lift force. Reduction ratio increases as tapering ratio increases, and the set-backed model is more effective to reduce the fluctuating lift force than the tapered model with identical surface area, reducing the coefficients about 40% in suburban flow condition. And by tapering and set-back, the power spectra of wind pressures at sideward surface become wideband and the peak frequencies depend on height, which makes the correlation near the Strouhal component low or even negative.     

大高宽比方形截面高层建筑的横风向风荷载及风致响应研究

基于一栋高层建筑的刚性模型表面压力测量风洞试验数据,分析了高宽比较大且截面为方形的高层建筑横风向风效应的共同特征。得到如下结论:高层建筑横截面为方形时,其横风向风荷载主要由规则性旋涡脱落导致的尾流激励构成,为窄带随机激励;当高层建筑的高宽比较大时,基阶固有频率相对较低;当高层建筑兼具方形截面和大高宽比这两个特征时,其基阶固有频率可能接近其尾流的旋涡脱落频率,从而发生剧烈的横风向涡激共振。建筑结构截面的小幅增大可使这种剧烈的横风向涡激共振得到有效控制。上部外形的适当处理,也可能有效降低高层建筑的横风向等效风荷载。低矮群楼的出现将在一定程度上影响高层建筑的风荷载。     

矩形截面超高层建筑风致脉动扭矩的数学模型

利用风洞试验结果,对矩形截面超高层建筑风致脉动扭矩数学模型进行研究。以厚宽比和风场类别为基本变量,采用最小二乘法得到了风致脉动扭矩系数根方差、功率谱密度、竖向相关性系数以及横风向基底弯矩-基底扭矩相干函数闭合计算公式。这些公式的计算结果与原始试验数据吻合较好,说明计算公式具有较高精度。此外,利用结构随机振动方法,用提出的公式以及直接采用试验风压数据计算一栋实际超高层建筑的扭转动力响应,对比了扭转广义力谱、顶层扭转响应谱以及扭转响应根方差等计算结果,对比结果表明两者吻合较好,从而验证了公式的适用性。     

Interference excitation of twin tall buildings

The enhanced dynamic response of a tall square building under interference excitation from neighbouring tall buildings has been studied in a series of wind-tunnel model tests. In a low-turbulence wind environment and under normal strong wind conditions, the dynamic loads on the upstream of an identical pair of tall buildings may increase by a factor of up to 4.4. The dynamic loads on the downstream building of the pair may increase by a factor of up to 3.2 due to “resonant buffeting”. Measurements of along-wind and cross-wind force spectra and a number of wake spectra provide an explanation for the observed behaviour. Possible excitation mechanisms are discussed and critical building arrangements presented. The large interference loads found in this study indicate that interference excitation should be carefully considered in the design of tall buildings.     

锥形超高层建筑脉动风荷载特性

采用同步测压技术,进行了具有不同锥率的超高层建筑刚性模型风洞试验,对该类建筑物的脉动风荷载特性进行了研究。结果表明：超高层建筑采用锥形轮廓后,延长了来流在建筑物侧风面漩涡脱落的卓越频率,横风向升力系数功率谱谱峰小幅下降,有利于缓解风荷载作用下建筑物横风向风荷载及其风致效应,这对横向风风致效应起控制性作用的超高层建筑十分重要。对比分析表明：随着建筑物锥率的增加,横风向升力系数归一化功率谱谱峰下降,功率谱带宽增大,升力系数根方差减小。但是,超高层建筑锥率的变化对顺风向阻力及扭转向扭矩影响较小。锥形超高层建筑的相关系数、相干函数的变化规律与普通棱柱形超高层建筑基本一致,但其升力以及升力与扭矩之间的相关性有所减弱,相干系数小幅增加。     

Cross-wind response of tall buildings

A design procedure was developed using random vibration theory and uses mode-generalized cross-wind force spectra and aerodynamic data to calculate the cross-wind displacement and acceleration responses of tall buildings. The force spectra of a number of building shapes and sizes in both suburban and city centre type wind flow are presented. The proposed design procedure gives reasonable estimates of the cross-wind response, compared with wind tunnel measurements, at reduced wind velocities and at structural damping values consistent with modern habitable tall building design. This allows assessment of the structural requirements of tall buildings to be made at an early design stage, and also allows the designers to assess the need for more detailed and expansive wind tunnel model tests.     

高耸塔架横风向动力风效应

在现行的荷载规范、高耸结构设计规范以及能源部颁发的《架空送电线路杆塔结构设计技术规定》（ＳＤＧＪ９４－９０）中,对格构式塔架的横风向风振力均未作考虑。作者通过对气动弹性模型风洞试验和国外现场实测资料的分析,论证格构式塔架具有几乎与顺风向等同的横风向风振力,以期在设计中引起足够的重视,并且根据试验结果提出了横风向风振力的简化计算公式。     

矩形高层建筑横风向风振响应简化计算

基于风洞试验数据和随机振动理论,本文提出了矩形高层建筑横风向风振响应简化计算公式,这些简化公式的提出将求高层建筑横风向风振响应的复杂积分变为方便的代数运算。本文应用这些简化公式对大量的矩形高层建筑实例进行了计算、分析。将本文提出的简化公式计算结果与积分计算结果比较,相对误差基本上在5%以内,因此本文提出的公式有较高的精度。用本文简化公式计算得到的高层建筑横风向风振响应与日本建筑荷载规范、加拿大国家建筑规范计算得到的横风向风振响应比较,总体上差异较小。由于本文提出的简化公式所依据的风洞试验模型和数据较为精细,因此本文简化公式有相当高的可靠性与合理性。     

山地风场中超高层建筑风荷载幅值特性试验研究

针对山地风场中超高层建筑风荷载特点,在1.4m×1.4m风洞中进行了11个不同高宽比、厚宽比矩形截面和圆形截面超高层建筑表面测压风洞试验,分析了阻力系数平均值、均方根值和升力、扭矩系数均方根值受来流风湍流度、建筑高宽比、厚宽比和层相对高度等因素的影响。结果表明：矩形截面建筑各气动力幅值特性明显随湍流度、建筑高宽比、厚宽比、层相对高度的改变而变化,而圆形截面建筑各气动力幅值特性仅随湍流度、层相对高度的改变而变化。根据风洞试验结果,建立了正方形截面和圆形截面风荷载幅值特性的数学模型,通过比较说明与风洞试验结果吻合较好,可为山地风场中的超高层建筑风致响应计算提供依据。图11表5参10     

Integrated wind‐induced response analysis and design optimization of tall steel buildings using Micro‐GA

This paper presents an integrated procedure for wind‐induced response analysis and design optimization for rectangular steel tall buildings based on the random vibration theory and automatic least cost design optimization technique using Micro‐Genetic Algorithm (GA). The developed approach can predict wind‐induced drift and acceleration responses for serviceability design of a tall building; the technique can also provide an optimal resizing design of the building under wind loads to achieve cost‐efficient design. The empirical formulas of wind force spectra obtained from simultaneous measurements of surface pressures on various rectangular tall building models in wind tunnel tests are verified testified using a published example. Upon the known wind force spectra, the equivalent static wind loads for every storey, such as along‐wind, across‐wind and torsional loads, are then determined and applied for structural analysis including estimation of wind‐induced responses. An improved form of GAs, a Micro‐GA, is adopted to minimize the structural cost/weight of steel buildings subject to top acceleration and lateral drifts constraints with respect to the discrete design variables of steel section sizes. The application and effectiveness of the developed integrated wind‐induced response analysis and design optimization procedure is illustrated through a 30‐storey rectangular steel building example. Copyright © 2009 John Wiley & Sons, Ltd.     

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.     

基于完全气弹模型风洞试验输电塔风荷载识别

按照基本缩尺律,设计、制作了输电塔完全气弹模型,并通过大气边界层风洞试验,测试了多种风速、风向条件下输电塔的位移与加速度响应。通过加速度响应功率谱识别出结构的固有频率,并采用Hilbert-Huang变换结合随机减量法识别出包含结构阻尼和气动阻尼的结构总阻尼。利用虚拟激励法建立了由测点位移响应来识别结构顺风向、横风向风荷载的方法。由识别出的风荷载谱曲线,利用非线性最小二乘法拟合得到输电塔顺风向、横风向风荷载经验公式。研究结果表明：风洞试验设计、制作的输电塔气弹模型,测试得到的模型第1阶自振频率与有限元计算结果吻合较好;横风向荷载谱形态与顺风向的相比有较大的区别,其能量分布在一个更宽的频带上,其峰值频率是顺风向的3～4倍。     

典型超高层建筑风荷载频域特性研究

在边界层风洞中对10个典型超高层建筑模型进行了测压试验,获得了测点层的顺风向、横风向和扭转风荷载,对风荷载的功率谱、相关系数和水平、竖向相干函数进行了细致分析。得出以下结论:方形建筑阻力系数谱的峰值频率基本上与来流纵向风谱保持一致,升力系数谱的频带随着地面粗糙度的增大而变宽,能量减小,扭矩系数功率谱的能量随紊流度的增加而增加;矩形建筑长边迎风时,升力和扭矩系数谱均表现出很强的旋涡脱落特征,斯特罗哈数约为0.11,短边迎风时,升力和扭矩系数谱的频带明显变宽,峰值频率降低;升力和扭矩系数的相关性比较强,而阻力系数和升力系数、扭矩系数之间的相关性则相对小些;在旋涡脱落频率附近,升力系数和扭矩系数的相干性都明显增强。     

Wind engineering challenges of the new generation of super-tall buildings

The new generation of tall buildings is going much higher than before. This poses new challenges for wind engineering. The boundary layer models in many building codes and standards have served well for buildings less than about 300 m but more realistic models need to be used above 300 m. The statistics of upper level winds need also to be known with better certainty. New tools such as the archived global re-analysis data coming from weather forecast models can help shed more light on the upper level wind statistics. There are also questions to be answered about the effects on all tall buildings of non-synoptic wind profiles such as occur in thunderstorm downbursts and the Shamal winds of the Middle East. For the super-tall buildings wind tunnel testing is often commenced much earlier in the design than for lesser buildings. This permits the results to be used in a pro-active way to shape both the architectural design and structural design. The wind tunnel methods used include the force balance technique, aeroelastic modeling, high frequency pressure integration tests, as well as the traditional pressure model and pedestrian wind studies. A super-tall building pushes the limits of the force balance method due to difficulties in maintaining sufficient model stiffness and in accounting for the influence of higher modes of vibration. Since the impact of wind on people using terraces and balconies increases with building height, it is an issue needing particular attention for super-tall buildings.