实测风场风速风向耦合的三维非平稳特征研究

为了获取考虑风速风向耦合效应的实测风场非平稳特征，在获取三维脉动风速时程的过程中，采用EMD方法建立了三维脉动非平稳风速模型，并推导出了脉动风速时程表达式，进一步发展了风速时变标准差、时变湍流强度的概念。以高层建筑实测台风数据作为算例，并与平稳风速模型进行对比分析，验证了非平稳风速模型的准确性和优越性：不需要选取基本时距；时变的物理量能反映微观特征，更能反映风速的非平稳性。通过平稳度指数检验了数据分析过程的平稳性特征，结果表明：风速在频域内的平稳性指数随着频率的增大而逐渐增大；不考虑风向时，风速的平稳性指数大小是与风速的变化速率相关的；非平稳风速模型所计算的脉动风速平稳性较平稳性模型方法所分析结果有所改善。     

Study on wind characteristics of a strong typhoon in near‐ground boundary layer

In order to solve the problems existing in predicting typhoon design wind speeds used for tall and special buildings, a 40‐m‐high meteorological tower, which is located near the coast of the East China Sea in Shanghai, was built to observe the strong winds. Based on the measurement data during Typhoon Muifa (2011), the characteristics of strong wind such as wind speeds and directions, turbulence integral scales, probability densities, power spectra, spatial correlation coefficients, and coherence coefficients were analyzed. The results revealed that the turbulence integral scales increased with height and averaging time interval. All three fluctuating wind components follow the Gaussian distribution, regardless of the measurement height and the time interval of the segment. The power spectra of longitudinal fluctuating wind velocity agreed with the von Karman spectrum. However, the power spectra of lateral and vertical fluctuating wind velocity are deviated from the von Karman model in high‐frequency region. The decay rate of the autocorrelation coefficients of the longitudinal and lateral fluctuating wind velocity decreased with height. The variations of cross‐correlation coefficients among three fluctuating wind display no clear regulation. The spatial cohesion coefficients follow the predictions made according to Davenport's empirical formula.     

Reliability analysis of wind turbines under non‐Gaussian wind load

Based on translation models, both Gaussian and non‐Gaussian wind fields are generated using the harmony superposition method for examining the reliability of a typical wind turbine at operational and parked conditions. Using the blade aerodynamic model and multibody dynamics, wind turbine responses are calculated and then probability characteristics are analyzed in details. The short‐term extreme response distribution is estimated by the average conditional exceedance rate method at each mean wind speed bin, and the long‐term extreme response distribution is then determined by further integrating the short‐term extreme response distribution conditional on wind speed with the distribution of mean wind speed. Additionally, crack initiation life and crack propagation life are evaluated using the linear cumulative damage theory and linear crack propagation theory, respectively. The results indicate that non‐Gaussian characteristics of wind inflows have a noticeably greater influence on both extreme response and fatigue damage, and the Gaussian assumption cannot suit wind turbine in complex terrain.     

温州地区近地强风特性实测研究

为研究我国沿海地区的近地强风特性,基于设置在温州大学的风场观测点(离地约30m高),对台风“海鸥”影响温州时的风场状况进行了监测,获取了台风期间近地风场的实测数据。通过对台风影响过程的风速和风向、湍流度、阵风因子、湍流积分尺度、脉动风速功率谱密度函数和空间相干性等参数的分析,研究了台风“海鸥”影响温州时的近地风场特性。结果表明：台风“海鸥”的湍流度和阵风因子较大,顺风向和横风向湍流度接近;顺风向与横风向湍流积分尺度的均值分别为70.4m和66.6m;实测风速谱与von Karman谱基本符合;实测两点的脉动风速空间相干系数在零频率处与Shiotami经验公式计算结果一致。     

Monitoring of structural modal parameters and dynamic responses of a 600m‐high skyscraper during a typhoon

This paper presents field measurement results of structural dynamic properties and wind‐induced responses of 600m‐high Ping‐An Finance Center in Shenzhen during the passage of Typhoon Haima. The field measurements included wind speed, wind direction, and structural acceleration responses during the typhoon. Analysis of the field measurements is carried out to investigate the wind‐induced structural vibrations and dynamic properties of the skyscraper under typhoon condition. In the analysis, natural frequencies and damping ratios of Ping‐An Finance Center are estimated using Peak‐Picking method, half‐power bandwidth method in frequency domain, and random decrement technique in time domain, respectively. Two band‐pass filtering methods, namely, elliptical filtering method and Kaiser‐window FIR filter, are adopted to deal with the measured acceleration signals. Consequently, the modal parameters identified with the Peak‐Picking, half‐power bandwidth, and random decrement technique methods are presented and discussed in detail. In addition, the probabilistic characteristics of the recorded acceleration responses are analyzed using the generalized extreme value distribution, and then the serviceability of the skyscraper during the typhoon is evaluated.     

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.     

Wind‐induced fatigue of large HAWT coupled tower–blade structures considering aeroelastic and yaw effects

An efficient approach for predicting wind‐induced fatigue in large horizontal axis wind turbine coupled tower–blade structures subject to aeroelastic and yaw effects is presented. First, aerodynamic loads under yaw conditions are simulated based on the harmonic superposition method and modified blade element momentum theory, in which wind shear, tower shadow, tower–blade interactions, aeroelastic, and rotational effects are taken into account. Then, a nonlinear time‐history of wind‐induced responses under simulated aerodynamic loads is obtained. Finally, based on these results, wind‐induced fatigue damage and lifespan are predicted according to linear cumulative damage theory. For completeness, the influences of mean wind speed, aeroelasticity, and yaw angle on horizontal axis wind turbine fatigue life are discussed. The results indicate that the aerodynamic loads and residual fatigue life can be estimated accurately by the proposed model, which can be used to simulate the 3D wind fields of wind turbines under given wind conditions. The wind energy of the wind turbine blade is mainly concentrated at its edge and is weaker at the hub. Estimation of wind turbine fatigue life is therefore suggested to be based on the component with the shortest life, being the blade root. Furthermore, yaw conditions significantly shorten fatigue life and should not be ignored. Fatigue life is also rather sensitive to mean wind speed.     

Dynamic performance evaluation of Shanghai Tower under winds based on full‐scale data

Shanghai Tower is the tallest building in China with a height of 632 m. This study aims to investigate the wind characteristics and its impact on Shanghai Tower so as to provide useful information for the wind‐resistant design of 600 m+ super‐tall buildings. By analyzing the data of wind speed during the occurrence of DeHong in June 2017, the relationship between turbulence intensity and mean wind speed is verified, and the correlation between gust factor and turbulence intensity is confirmed. Apart from that, it is also found that the von Karman spectrum fits well with the measured fluctuating wind speed spectrum. In addition, the 83rd and 117th acceleration data are analyzed to obtain the natural frequency by peak‐picking, frequency domain decomposition, stochastic subspace identification, and fast Bayesian fast Fourier transform methods. The amplitude‐dependence dynamic parameters of Shanghai Tower on the basis of the field measurements are studied as well. Finally, the wind‐induced vibration is investigated based on the acceleration data and wind speed data, which verifies that the responses along two main axes having a similar amplitude under wind effects. The occurrence of DeHong demonstrates that a gale equivalent to a typhoon may occur in urban areas without any urban warning.     

Peak factors of non‐Gaussian wind forces on a complex‐shaped tall building

This paper focuses on the development of peak factor formulas of non‐Gaussian wind pressure processes after reviewing the current estimation methods of non‐Gaussian peak factors. A skewness‐dependent peak factor is proposed by accounting for the contribution of skewness and kurtosis parameters in some existing Hermite moment‐based formulas. The possible correction on the upcrossing rate used in the translation process approach is also investigated. Wind tunnel pressure data on a practical 43‐story building with unusual shape is used to validate the accuracy of the skewness‐dependent peak factor by investigating various statistical properties of wind‐induced fluctuating pressure field on the complex‐shaped tall building example. Copyright © 2012 John Wiley & Sons, Ltd.     

Wind characteristics of a strong typhoon

The wind characteristics of a strong typhoon (Typhoon Maemi 2003) are analyzed on the basis of 10 min wind speed samples. The wind speeds were measured simultaneously by nine vane and seven sonic anemometers at a height of about 15 m. Turbulence intensity and scale, gust factor, peak factor, decay factor of the coherence function, probability distribution function, power spectrum, and their variations with wind speed are obtained. Wind-direction-dependent analysis is conducted on the wind characteristics. Turbulence intensity decreases with wind speed and remain almost constant when the wind speed becomes high. The averaged values of gust factor and peak factor are 1.6 and 3.3, respectively. The spatial cross correlation and decay factor of the coherence function increase slightly with wind speed. The probability density function of fluctuating wind speed of a strong typhoon follows a Gaussian distribution, and the power spectrum of strong wind can be expressed by a Karman-type spectrum at the low frequency. The wind characteristics of this strong typhoon are shown to be very similar to those of non-typhoon winds.     

Field measurements of wind and structural responses of a 70‐storey tall building under typhoon conditions

This paper describes the results obtained from the full‐scale measurements of wind effects on a 70‐storey tall building in Hong Kong. The objective of the experiment is to measure wind action on and wind‐induced response of the tall building. Simultaneous and continuous data of wind speeds, wind directions and acceleration responses have been recorded at the top of the tall building since 1995. The field data presented in this paper were measured during the passage of four typhoons—Typhoon Kent (1995), Typhoon Ryan (1995), Typhoon Sibyl (1995) and Typhoon Sally (1996). The characteristics of the typhoon wind and the structural responses of the building are investigated. The serviceability of this tall building under typhoon conditions is discussed on the basis of the field measurements. Copyright © 2000 John Wiley & Sons, Ltd.     

Non‐Gaussian characteristics and extreme distribution of fluctuating wind pressures on large cylindrical–conical steel cooling towers

Large cylindrical–conical steel cooling tower (SCT) represents a new configuration of cooling tower, and its wind load distribution pattern and forming mechanism are very different from those of the traditional hyperbolic cooling towers. Large eddy simulation was used for the numerical simulation on a superlarge cylindrical–conical SCT that exceeds the specification limit, which is also the highest (189 m) SCT under construction in Asia. The surface flow field and time history of 3‐D aerodynamic force were obtained for the cylindrical and conical parts, respectively. Comparison with the measurements of other large cooling towers and the results of wind tunnel test confirmed the validity of the numerical simulation. Then, based on the probability density distribution and spatial correlation of representative measuring points, regions of non‐Gaussian distribution were identified. The forming mechanism of non‐Gaussian wind pressure distribution was revealed from the perspective of the correlation of non‐Gaussian distribution versus flow separation and eddy motion. The criteria for classifying the region of non‐Gaussian distribution for the cylindrical and conical parts were analyzed, respectively. Research shows that the wind pressures in the windward regions of conical and cylindrical parts obey Gaussian distribution; however, the wind pressures from the region of extreme negative pressure to the region of flow separation are largely non‐Gaussian and the wind pressures of the conical part are generally non‐Gaussian in the leeward region. Finally, the three algorithms for calculating the extreme values of wind pressure were used, namely, peak factor method, improved peak factor method, and Sadek–Simiu method. The distribution patterns of peak factors and extreme values of wind pressure in SCT towers were analyzed comparatively. The 2‐D formulae for fitting the extreme values of wind values for the cylindrical and conical parts were derived by nonlinear least square method. Moreover, strategy for value determination was also presented. The present research aimed to strengthen the understanding of the fluctuating wind pressure distribution and its forming mechanism for large cylindrical–conical SCT towers.     

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.     

Field measurements and wind tunnel experimental investigations of wind effects on Guangzhou West Tower

The wind‐induced acceleration responses at the top of the Guangzhou West Tower (GZWT; 432 m) and the wind speed and direction at the top of Guangzhou Tower (532 m), which is located across the GZWT, were measured during the passage of Typhoon Mangkhut. The two buildings are separated by a river. The variation characteristics of the first two natural frequencies and damping ratios of the GZWT under strong vibrations are obtained by using random decrement technique (RDT) and modified Bayesian spectral density approach (MBSDA). Finally, field measurements of the maximum peak accelerations are compared with wind tunnel test results. The damping ratios identified by MBSDA are found to be greater than the results obtained by RDT. The natural frequencies decrease with increasing maximum acceleration of the corresponding acceleration segment. Besides, they decrease firstly and then increase with time elapses, reaching a minimum value at the maximum mean wind speed. The damping ratios are completely discrete, and no obvious linear correlation exists between the damping ratios and maximum acceleration of the corresponding acceleration segment. The peak accelerations at the top of the GZWT obtained from wind tunnel experiment agree well with that of full‐scale measurements.     

Identification of Wind Loads and Estimation of Structural Responses of Super‐Tall Buildings by an Inverse Method

This article presents a Kalman‐filter‐based estimation algorithm for identification of wind loads on a super‐tall building using limited structural responses. In practice, acceleration responses are most convenient to be measured among wind‐induced dynamic responses of structures. The proposed inverse method allows estimating the unknown wind loads and structural responses of a super‐tall building using limited acceleration measurements. Taipei 101 Tower is a super‐tall building with 101 stories and a height of 508 m. Field measurements and numerical simulations of the wind effects on Taipei 101 Tower are conducted. The wind loads acting on the super‐tall building are estimated based on the wind‐induced responses determined from the numerical simulations and the refined finite‐element model of the structure, which are in good agreement with the exact results. The stability performance of the proposed algorithm is evaluated. The influence of noise levels in the measurements and covariance matrix of noise on the identification accuracy are investigated and discussed based on the L‐curve method. Finally, the wind loads and structural responses are reconstructed based on the field‐measured accelerations during Typhoon Matsa. The accuracy of the identified results is verified by comparing the reconstructed acceleration responses with the field measurements. The results of this study show that the proposed inverse approach can provide accurate predictions of the wind loads and wind‐induced responses of super‐tall buildings based on limited measured responses.     

Comparison of wind‐induced dynamic property of super‐large cooling tower considering different four‐tower interferences

Dynamic amplification effects caused by tower‐group interference is the most critical causes of wind‐induced destructions of super‐large cooling tower (SLCT), and four‐tower combinations are the most common tower‐group combining form. However, the dynamic amplification effects of SLCT of different four‐tower arrangements have not been studied systematically so far. The highest (220 m) SLCT in the world was taken as the target to conduct SLCT wind pressure measurement under 320 wind tunnel test conditions. Firstly, the stability performance under the design wind loads was analyzed. Then, the dynamic time‐history analysis was carried out, and the distribution characteristics of peak factors and values of extreme response were discussed. Furthermore, with a new concept parameter “tower‐group wind vibration coefficient” for the wind‐resistance design of SLCT, the distribution laws of two‐dimensional (2D), one‐dimensional (1D), and global tower‐group wind vibration coefficient were revealed under different four‐tower interferences. On these bases, we recommend the design parameters for wind‐resistance study of SLCT and the priority of four‐tower combination forms. The study showed that the dynamic effects of SLCT under different four‐tower arrangements were significantly different from each other and the tower‐group wind vibration coefficients proposed in this paper can reflect the interference effects of tower‐group more efficient than traditional design method. The results may become a useful database for the wind‐resistance design of SLCT and provide clues for the optimization of four‐tower arrangements in power plants.     

台风 “鲇鱼”作用下厦门沿海某超高层建筑的风场和风压特性实测研究

为研究我国沿海地区超高层建筑的风场和风压特性,在2010年台风“鲇鱼”登陆前后对厦门沿海某超高层建筑的风场和建筑表面风压进行了同步监测。通过对实测风场和风压数据的深入分析表明：沿海地区超高层建筑风场的湍流度随风速增大变化平稳,阵风因子随湍流度的增大而增大;实测脉动风速功率谱密度与von Karman谱吻合较好;建筑各面内测点之间的瞬时风压、平均风压、平均风压系数和极值风压系数具有较强的相关性;实测平均风压和平均风压系数在迎风面较大,在背风面非常小;当风从角部吹向建筑时,随着风向角的变化,两迎风面的平均风压系数随着平均风速的增大变化规律相反;两背风面的平均风压系数随着平均风速的增大逐渐减小;迎风面的极值风压系数随着风向角的变化正负波动较大,背风面的极值风压系数分布较为均匀;迎风面的脉动风压系数较大且变化较大,背风面的脉动风压系数非常小且变化平稳;建筑各面的极值风压系数和脉动风压系数的幅值随着风速的增大逐渐减小。     

Wind field simulation and wind‐induced responses of large wind turbine tower‐blade coupled structure

Herein, by a case study on a 5‐MW wind turbine system developed by Nanjing University of Aeronautics and Astronautics, the wind field simulation and wind‐induced vibration characteristics of wind turbine tower‐blade coupled systems is analyzed. First, the blade‐nacelle‐tower‐basis integrated finite element model with centrifugal forces induced by rotational blades is established. Then, based on a harmony superposition method and the modified blade element‐momentum theory, the fluctuating wind field of tower‐blade coupled systems is simulated, which considers wind shear effect, tower shadow effect, rotational effect, blade‐tower dynamic and model interaction effects. Finally, the wind‐induced dynamic responses and wind vibration coefficients of the wind turbine tower‐blade coupled structure are discussed through the ‘consistent coupled method’ previously proposed by us. The results indicate that the wind‐induced responses of a large wind turbine tower‐blade coupled structure present complicated modal responses and multimode coupling effect. Additionally, the rotational effect would amplify aerodynamic loads on blades with high frequency, wind‐induced dynamic responses and wind vibration coefficients of wind turbine tower. The centrifugal force effect could also amplify natural vibration frequency of the tower‐blade coupled system and reduce the wind‐induced dynamic responses and wind vibration coefficients of wind turbine tower. The research could contribute to wind‐resistant design of structure for a large‐scale wind turbine tower‐blade system. Copyright © 2014 John Wiley & Sons, Ltd.     

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.     

Wind effects on a long-span beam string roof structure: Wind tunnel test, field measurement and numerical analysis

The Guangzhou International Convention & Exhibition Center (GICEC) with roof dimensions of 210 m wide and 457 m long is the largest exhibition center in Asia and the 2nd largest of this kind in the world. This paper presents results from a combined study of wind tunnel test, full-scale measurement, and numerical analysis of wind effects on the long-span beam string roof structure. In the wind tunnel test, wind-induced pressures including mean and fluctuating components were measured from the roof of a 1:300 scale GICEC model under suburban boundary layer wind flow configuration. The Proper Orthogonal Decomposition (POD) method and the quasi-steady approach as well as probability analysis were adopted to estimate the characteristics of the fluctuating wind pressures on the roof. On the other hand, full-scale measurements of wind actions and wind-induced structural responses of the roof were conducted during the passage of Typhoon Nuri. The field data such as wind speed, wind direction, and acceleration responses, etc., were continuously and simultaneously monitored from a wind and structural response monitoring system installed on the roof structure during the typhoon. Detailed analysis of the field data was performed to investigate the characteristics of the typhoon-generated wind and the wind-induced vibration of the long-span roof structure under typhoon condition. The dynamic characteristics of the roof were determined from the field measurements and comparisons with those calculated from the finite element model (FEM) of the structure were made. The damping ratios of the roof structure were estimated by means of the random decrement method and the amplitude-dependent damping characteristics were presented and discussed. Finally, the full-scale measurements were compared with the model test results to examine the accuracy of the wind tunnel test results and to identify possible modelling errors in the numerical study. The results presented in this paper are expected to be of considerable interest and of use to researchers and professionals involved in designing long-span roof structures.