Research on the Body Coefficient of Complicated Tall Buildings

Considering the complication of the coefficient of wind-induced vibration for tall buildings,the scale 1:300 model test of Ying Li Building is completed in the second wind tunnel of Beijing University.Based on the calculation and analysis of the test results,the static and dynamic wind pressure acting on the building can be obtained and the value of the coefficient of wind-induced vibration for this tall building can be solved directly,thus a new way is laid for the research of complicated tall buildings.     

Analysis of wind load spectrum of super tall buildings with round section in hilly terrain wind field

In order to get wind load and wind induced response of super tall buildings in hilly terrain wind field, effect of changing of turbulent intensity on wind loads must be known. 4 kinds of turbulent wind field are simulated, and 3 super tall building models with round section of different aspect ratio are manufactured. Effects of turbulent intensity, aspect ratio and layer height on along-wind and across-wind load are discussed. Different models are used in fitting of wind load spectrum on each direction. Parameters of load spectrum models are secondary fitted based on turbulent intensity and aspect ratio. Mathematical models of wind load spectrum of super tall buildings with round section in hilly terrain are preliminarily established. At last, an example is provided. According to vertical profile of mean velocity, turbulent intensity and mathematical model of wind load spectrum, wind induced dynamic response of super tall buildings in hilly terrain and flat terrain are compared.     

三边形桅杆风荷载谱模型试验研究

对三边形格构式桅杆进行了均匀流和两种紊流下的高频测力天平风洞试验,得到了顺风向、横风向和扭转向的气动力系数以及脉动风荷载谱。采用基于风速谱的数学模型对顺风向脉动风荷载谱进行拟合,验证了该经验公式在不同流场下的适用性。根据试验所得横风向和扭转向脉动风荷载功率谱曲线的特点,建立由紊流激励和旋涡脱落激励两部分组成的谱函数数学模型,最小二乘法拟合结果与风洞试验结果吻合良好。横风向脉动风荷载谱以紊流激励为主,紊流强度15%时旋涡脱落激励贡献仅占10%,扭转向脉动风荷载谱中旋涡脱落激励贡献明显增大,达到40%。     

Analysis on drag coefficients of bundled conductors under wind load

Drag coefficients of quad-bundled conductor under different wind speeds and attack angles are firstly determined by means of wind tunnel test. Meanwhile, the drag coefficients are obtained by numerical simulation method and the results are consistent with those by the wind tunnel test. Furthermore, cross flows around six-bundled and eight-bundled conductors are numerically investigated, and the drag coefficients are then determined. Compared with the determination method of wind load on conductor in current Chinese code and the IEC code for the design of transmission line, the drag coefficients defined in the Chinese code may be too large for bundled conductors, and may need to be adjusted based on further theoretical and wind tunnel test investigation.     

龙卷风作用及核电站结构极端风荷载相关问题研究综述

在结构荷载规范中一般均不考虑龙卷风荷载,但对于某些设防要求极高的重要工程设施,如核电站,则需要考虑可能的龙卷风荷载作用。从龙卷风风场理论模型的研究发展入手,对直接风压荷载的确定、风致飞射物间接作用以及特种工程结构核电站抗龙卷风设计的研究现状进行了归纳总结,指出了龙卷风直接风压计算中考虑轴吸力作用、风场平移运动及风致扭转作用的必要性以及飞射物冲击作用应区别弹体相对刚度及端部形态对作用效果的影响。     

Wind Vibration Analysis on the Large -span Curtain Wall

The large-span structure requires wind vibration analysis when computing the wind load;however,the formula in current code on wind vibration coefficient can hardly be applied in large-span structure,making its computation difficult and troublesome.This paper makes wind vibration analysis on the large-span curtain wall combined with certain engineering background in the methods of both time domain and frequency domain,and then the derived results are compared.The analytical results demonstrate identical distribution and contiguous numerical value of wind vibration coefficient concluded from the two varied methods;furthermore,even if the method in time domain is higher in computational complexity,more data on the response of structure under wind can be obtained,which provides reference for the theoretical analysis and engineering design.     

Arrangement and design of main bearing for wind turbine

The wind turbine bearing runs under complicated loading and vibration condition and its design and analysis is a developing and crossing discipline. The typical main bearing arrangements for wind turbine are compared, including the 3-point arrangement with spherical roller bearing, double-row tapered roller bearing and cylindrical roller bearing, two single-row tapered roller bearings. The various factors including the wind turbine type, loading, cost and weight are considered in the design of wind turbine drive train. The influencing factor of bearing reliability and the relationship between wind load, drive train and bearing are studied. Based on an example of bearing reliability, the influence of complicated topography on wind load and bearing life is analyzed. The commonality of the wind farms with wind turbine failure is found, i.e. the topology and the wind condition of most wind turbine sites are very unfavorable, e.g. with sleep slope, not enough distance between adjacent wind turbines. Such factors can cause abnormal wind shear and turbulence, which can bring unexpected load onto the bearing. The key factors in the analysis procedure of topography and wind resource are discussed.     

Experimental Technology on Dynamic Wind Loads on a Tall Building

The wind load is a major load on tall buildings from side directions. It is of considerable necessity to building engineering that the static and dynamic wind load and the dynamic wind response can be achieved accurately. Therefore, the model of a tall building in Chongqing is made and tested in wind tunnel by using the high frequency balance used widely home and abroad at present. The characteristics of wind load are studied. This paper gives the coefficients of base force of the building produced by wind load in different wind directions, and offers reference for wind-resistant design of the building.     

Analysis of accelerated fatigue test technology for wind turbines gearbox

In order to satisfy the high reliability requirements of wind turbines gearbox, a method of accelerated fatigue test is proposed to verify the fatigue reliability of the gearbox. According to the design load spectrum, the equivalent load and the number of stress cycles of parts in gearbox are deduced. Based on Miner linear cumulative damage theory, the fatigue degree of the gears and bearings are calculated. A linear accelerated load spectrum with the equivalent fatigue ratio of design load spectrum is provided to check the reliability of the gearbox. The results show that this method can verify the reliability of wind turbine gearbox within about 800 h.     

Gear-bearing coupling dynamics characteristics of wind turbine planetary gear transmission system under variable load

Considering that the transmission system of wind turbine works in complex and changing load environment caused by stochastic wind speed,this paper uses sparse least squares support vector machine(SL-SVM) to simulate wind speed of true wind field,and obtains time-varying wind load caused by stochastic wind speed. The lumped-parameter method is used to develop a dynamic model of planetary gear transmission system of wind turbine coupled with bearing. The model includes the varying wind load,time-vary mesh stiffness of gear pair and time-vary stiffness of rolling element bearing. The numerical method is used to simulate the dynamic performance of planetary gear system of Multibrid Technology Wind Turbine with 1.5 MW rated power. The vibration displacement responses of the transmission system are obtained as well as dynamic meshing force each pair of gear and nonlinear bearing forces. The research can provide a foundation for optimizing dynamic performance and reliable design of gear transmission system of wind generator.     

Load modling and analysis of wind turbine under consideringthe space coordinate transformation

Based on coordinate transformation and mechanical analysis, load transformation between blade root and rotor coordinate system for wind turbine is derived.And an analysis model closer to actual working condition is established.Taking a 5 MW wind turbine as analysis object, analyzing results of the new model, traditional simplified model and GH Bladed model are compared, and results are good enough to validate this new model has higher reliability and accuracy.In addition, based on analyzing to load component, through access to instance data of each factor in process of coordinate transformation, the impact of each factor can be accurately analyzed, which is of great significance to control and reduce load.     

热风与远红外组合加热式蔬菜脱水机的改进设计与试验

针对现有远红外蔬菜脱水机存在的易将表层物料烤黄、水分排除不及时及干燥物料厚度有限等问题,采用热风与远红外辐射相结合的组合干燥技术方案,对现有设备进行改造。改进后的设备引风管和供风管的连接管直径自上而下依次减小,即供给各层干燥箱的热风量和从各层干燥箱的引风量自上而下也相应地减小,满足了各层干燥箱对风量的不同需求。对比试验结果表明,采用热风与远红外组合干燥技术,解决了现有设备存在的问题,提高了脱水速率、干燥质量和能源利用率。     

Wind Loads Distribution on Typical Vaulted Shells

The distribution characteristics of shape factors and fluctuating wind pressure coefficients on two vaulted shells were investigated by simultaneous measurement of external and internal wind pressures on static models in wind tunnel. The effects of orifices on bottom and blocking at ends on wind loads distribution are discussed. It is shown that the wind pressure distribution is significantly affected by changes on orifices at bottom and blocking at ends. Wind pressure on ends decrease effectively and wind pressure on surface is distributed smoothly by blocking ends with highly curved surface shell. Small orifices at bottom not only contribute to degreasing negative pressure because of count acting effects of internal and external pressures, but also to extending the positive pressures region and increasing positive pressures. Wind loads suggestions on these structures are described at end.     

Influence Factors on Wind induced Fatigue Life of Steel Circular Antenna with Asymmetric Brace

Wind induced responses of a single steel circular antenna with an asymmetric brace were computed considering wind speed and direction joint distribution function at location of the structure, and then wind induced fatigue life of the structure was estimated in frequency domain and time domain, respectively. Some parameters, including wind direction, surface roughness, vortex induced resonance and mean wind speed, which would have effects on the wind induced fatigue life of the structure,were discussed. It is found that 1) wind direction has great effects on wind induced fatigue damage, that is, significant fatigue can occur in wind direction of high probability; 2) the more roughness the surface of structure is, the shorter the wind induced fatigue life is; 3) the effects of vortex resonance on wind induced fatigue life should not be neglected; 4) the mean velocity has slight impact on the wind induced fatigue life of the structure.     

Performance simulation of high-power wind turbine under the action of wind and wave

In order to research the offshore wind turbine which operates in harsh environment with transient and variable working conditions, the system is simulated and analyzed by simulation technology. The aerodynamic load of wind turbine is calculated by applying GDW theory and wave load is calculated by applying Airy wave theory. The drive chain is programmed in Matlab/ simulink and the flexible multi-body model of the wind turbine is built in Adams. The combined simulation of the wind turbine is carried out. The results of a 5 MW offshore wind turbine show that the method has excellent ability to simulate the performance almost the same as software Bladed result.     

Approaches to enhance power density of gearboxes for wind turbines

Based on pitting strength, some approaches to enhance power density of gearboxes for wind turbines are discussed. The calculation load is greatly reduced by power division. Allowable stress numbers are effectively increased by improving property of quality materials, precision heat treatment or shot peening. Load capacities can be also obviously enhanced by improving the tooth shape of morphology optimization of tooth root, tooth correction or superfinishing of tooth surface. The center distance is effectively decreased by minishing minimum allowable safety factor or enlarging face width. The power density of gearbox can be further improved by means of structure optimization of planet carrier or uniform load of planetary gear transmission.     

AN EXPERIMENTAL RESEARCH FOR THE WIND BEHAVIOR OF A HIGH-RISE WOODEN PAGODA IN CHINA

In this paper,a wind tunnel model test for a wooden pagoda to be con-structed is described,which imitates a Tan-dynasty Buddha tower.It puts special emphasis on the wind effect of the pagoda,the upwind direction,the form factor,the behavior of the flying eaves,etc.A comparison between the test results in uniform and gradient wind field is made.     

Wind Tunnel Test for Section Model of Caiyuanbai Bridge Over Yangtse River

With the development of modern construction technique and the application of new material,arch bridges which progress towards small rigidity,long span and light weight,what's more is that long span bridge's rigidity under construction is much less than that in use stage.So it is very necessary to study the aerodynamic characteristics of long span bridge.The regularity of the three dimensional static component forces coefficient varying with attack angle and the girder's flutter properties of Caiyuanbai Bridge over Yangtse River are investigated with segmental molding's static wind-tunnel test and segmental molding's dynamic wind-tunnel test.Eight derivatives of the girder are also identified from the segmental molding's dynamic wind-tunnel test.Finally the assessment to wind resistant properties of the bridge is given based on detailed analysis of the test results.The conclusion which gets from analysis can provide an suggestion to design and construction this kind bridge.     

通辽市固日班花风电场风能储量分析

为了开发科尔沁沙地的风能资源,为其治理提供便捷、安全的能源,利用科尔沁沙地最典型地区奈曼旗固日班花风电场测风塔和奈曼气象站的风向、风速资料,对固日班花风电场的风能储量进行分析。结果表明,固日班花风电场塔高10、60、65、70、80 m处的年平均风速订正后分别为4.9、6.8、7.0、7.2、7.3 m/s;相应风功率密度分别为136.5、315.4、341.3、365.6、382.1 W/m2。逐月风速与逐月风功率密度年内变化规律基本一致。风电场风能资源较为丰富,达到了建设大型风电厂的要求。     

Dynamic Responses of the High Slender Structure Under Non-Gaussian Model of Wind Load

With reference to the effect of the quadratic component of turbulent-wind fluctuation, the statistical moments of wind load up to the 4~(th) order are derived and the spectrum densities are given based on the Fourier transformation. By means of the Gram-Charlier series, the first-order probability densities of the structure responses are then constituted with the former 4~(th) order central moments of responses. Under the independent hypothesis of the structural displacement and its derivative, whose applicability is verified by the correlation between the two signals, the joint probability density function is developed and a numerical scheme for the analysis of the dynamic behaviors of the high-slender structure under wind excitation is obtained. Parametric analysis on dynamic responses and reliability under both Gaussian and non-Gaussian models of wind load are then investigated.