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.     

The Effect of Structure Form on Wind Resistance of Large Cantilevered Roof

On the background of grandstand cantilevered roofs of two aiding foreign stadiums, the wind resistance of two large cantilevered roofs with different structure forms is compared on the basis of pressure data acquired from wind tunnel test of rigid models, according to their models, frequencies, mean wind pressure coefficients and fluctuating wind pressure power spectrum densities. A conclusion is made that the arch on the front edge of the large roof can improve the wind resistance, and is validated by calculating wind induced responses of the two kinds of the large roofs. Finally, several reasons for that the arch on the front edge is beneficial to the wind resistance of the large cantilevered roof are concluded.     

Loading behavior analysis of an aluminum alloy roof structure system under wind loads

The numerical analysis of a conventional aluminum alloy roof system taken from an actual international airport under wind uplift is conducted. A two-step simulation analysis approach is proposed, which effectively overcomes the computational difficulties brought by the contact between panels and supports. Through numerical analysis of roof components, the failure mode of the roof connection and the load bearing capacity of the roof are obtained. And the efficiency of material strength in each component is evaluated as well. It can provide reference for the design and application of aluminum alloy roof structure.     

APPLICATION OF ARMA MODEL AND PARAMETER IDENTIFICATION TO SIMULATION OF PULSATING WIND

With the wide use of tall buildings,highrise structures,suspended structures and some other flexible structures,the analysis ofstructure responses under pulsating wind has been more and more valuedin the field of engineering.It is necessary to effectively give pulsatingwind records with certain stochastic characteristics for the analysis ofstructure responses under winds and the design of anti-vibration struc-tures.Using autoregressive moving average(ARMA)model and techoniqueof parameter identification,this paper studies the method to simulatingpulsating winds which are compatible with given factors(such as powerspectrum or other stochastic characteristics).The conclution shows thatit is an effective method.     

Analysis on Wind-induced Dynamic Response of Arched Corrugated Metal Roof

It is generally considered that the seismic response of arched corrugated metal roof is not the control factor of structure design because of its light dead weight, but the wind-induced dynamic response on the structure is significant, so more attention must be paid to it. First, the wind simulation of the structure by AR model is carried out. Then, the TRANS method in the ANSYS is used to calculate the dynamic responses in time domain to compare the results with those in frequency domain in order to verify the validity of the two methods.     

冬季自然条件下12种屋顶绿化木本植物抗寒性分析

为探索屋顶绿化木本植物的抗寒能力,筛选出耐寒强的屋顶绿化木本植物,在2010年12月、2011年1月和2月冬季自然降温条件下,结合实地观测屋顶和地面温度、风力、相对湿度等气象因子,采用电导法,分别对12种木本植物1年生休眠枝条细胞膜透性进行测定。结果显示,石家庄冬季屋顶比地面温度高、风速大、相对湿度低。构树、柳树、金银木抗寒能力强,‘金叶’榆、桑树、杠柳、白榆、小叶杨、‘金叶’女贞抗寒能力较强,珍珠梅、棣棠、红瑞木抗寒能力较弱。运用电导法评定屋顶绿化木本植物抗寒性是可靠的,为快速筛选抗寒性强的屋顶绿化木本植物提供了参考依据。     

New Iterative Method of Ventilation System'' s Wind Quantity for Electric Machines

Solving methods of wind quantity in complex ventilation meshes which includ wind pressure source are researched. A general matrix model of ventilation meshes and new iterative formulas are proposed. Two computing examples are given and the results shows that each branch' s wind quantity can converge the stable value by several times of iteration for any iterative initial value. The proposed model is suitable for wind quantity computation with complex ventilation structure of electric machines.     

Coupling Effect Analysis Between Background and Resonant Components for Equivalent Static Wind Loadings

Aimed at the limitations of total fluctuating wind-induced response with combination of background and resonant components using Square Root of the Sum of Squares (SRSS) method, the theoretical combination formulas of fluctuating wind-induced responses and ESWLs are derived based on structural dynamics and random vibration theory. Meanwhile, the refined analysis method is firstly presented by four components formula to compensate the coupling component between background and resonant modes. The proposed procedure avoids the integration process of calculating elastic restoring force and completely considers the modal coupling effects, which can be used to calculate the ESWL for any complex structures. Taking the steel grid roof structure of a large museum as an example, the new method was used to calculate its wind-induced response. Compared with results of complete quadratic combination (CQC), the effectiveness and accuracy of the present approach has been revealed.     

Simulation of nonstationary stochastic earthquake ground motion based on orthogonal Hilbert spectrum

A new method is proposed for the simulation of nonstationary stochastic earthquake ground motion based on orthogonal Hilbert-Huang transform (OHHT) spectra of its sample observations. Orthogonal EMD method is introduced to treat with IMF. OHHT avoids leakage of energy compared with conventional HHT, and it can be used for analysis of nonstationary signal. The average of the Hilbert spectra over the samples is defined as the Hilbert spectrum of the earthquake motion process and used as the target in the simulation of the process. Random Phase is also introduced to simulate nonstationary earthquake. The statistic characteristics function of stochastic process is given in the paper. Simulations of two earthquake ground motion are carried out. The results show that the samples can accurately reflect amplitude and frequency nonstationary of records. Samples and record of same earthquake ground motion process have same statistic characteristics.     

Wind Power Utilization Efficiency on Roof of Rectangular Buildings

Installing small wind turbines on the roof of buildings is a new way of wind power utilization in recently years. Based on the annual mean wind speed, the efficiency of wind power utilization on roofs of buildings was studied and the evaluation indexes for the utilization efficiency were proposed. With the help of CFD numerical analysis, the analysis on wind power utilization efficiency on flat roofs of rectangular buildings was carried out. The performance indexes of reference points under different windward angles were investigated. The best position and arrangement of wind turbines on the roof were also discussed. Furthermore, the utilization efficiency of four roofs with different shapes were analyzed and compared with that of flat roof.     

Small scale wind tunnel for high pressure and high energy discharge

A kind of small scale wind tunnel with low velocity is proposed according to the characteristics of strong ionization discharge chamber and the demands of discharge for flux, velocity and flow fields. On the precondition that the airflow field and velocity is satisfied, aerodynamic design and structural design are carried out. Key techniques are studied including overall structure, aerodynamic and structural design of airflow vent and collection vent, aerodynamic and structural design of power section, flow rate adjustment and control, and cooling system of motor. Based on the design scheme, a small scale wind tunnel with strong ionization discharge for an enterprise is developed. Application indicates that the small scale wind tunnel is a practical and effective airflow loop device for high pressure and strong ionization discharge with the features of stability and reliability.     

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.     

Open motion control architecture of wind turbineand main controller design

In this paper, we propose a method to solve the problems with stochastic nonlinear and point to point architecture of the wind turbines. The proposed method presents an open motion control architecture and a linearized torque control system based on power curve LUT. We reference the PLCopen motion control standard that is used to design the linearized torque and pitch systems of the wind turbines. This proposes a new methodology for the main controller design and the system integration of wind turbines.     

Junction stiffness analysis and vibration noise prediction of wind power speed-increase gearbox

In order to study the vibration characteristics and radiation noise of wind power speed-increase gearbox, a torsional vibration model of wind power speed-increase gearbox is established based on the analysis of supporting stiffness of bearing and contact stiffness of gear pairs. By solving the vibration differential equation with the help of Matlab, the frequency and corresponding vibration mode are obtained. With taking stiffness excitation, error exaction and meshing impact exaction into account, the dynamic finite element model of speed-increase gearbox is set up, and the dynamic response simulation is carried out. Regarding vibration displacement of the nodes on gearbox surface as boundary condition, an acoustic boundary element model of speed-increase gearbox is built. The surface acoustic pressure of gearbox and the radiation noise of field points are solved by the direct boundary element method. The results show that there is a great difference between torsion frequency and excitation frequency of wind power speed-increase gearbox, and so the resonance doesn't occur. The maximum structural noise and radiation noise mainly appear near the double octave of the gears meshing frequency of high-speed grade.     

Average surface roller pressure calculation method of roller mill

Hydraulic system pressure, contact surface between grinding roller and materials and grinding roller force of roller mill are analyzed. A new roller pressure calculation method named average surface roller pressure calculation method is proposed,and the corresponding theoretical formula is derived from three different perspectives, including roller pressure numerical calculation, stress and strain of main components and mill power through the calculation of real samples. The average surface roller and traditional average material roller pressure are compared to verify the correctness and accuracy of the proposed method. Design parameters such as the grinding roller structure, material maximum size, layer height and working pressure of the hydraulic system on the influence of roller are analyzed according to the formula of roller pressure. The research results provide theoretical basis for the selection of design parameters and the design calculation of structural strength for roller mill.     

The EME rules of composed coal and rock samples with hard roof failure and their application

The electric magnetic emission (EME) rules of deformation and failure of composed coal and rock samples are studied by lab experiments and fractal theory. The results show that at the initial stage of loading, EME signals increase, then decline slightly and stay at a stable level. Substantial increase appears when the composed coal and rock samples are close to the main fracture, and EME signals decline slowly when they are in the stage of residual deformation. The EME signals have a positive exponent relation to roof ratio in the composed coal and rock samples. The EME pulse count has the fractal characteristic, and the fractal dimensions increase with the process of loading. When the composed coal and rock samples are close to main fracture, the fractal dimensions decline suddenly, and it has a positive linear relation to the ratio of roof in the composed coal and rock samples. With the achieved rules, the burst danger has been forecasted successfully in face 7251.     

Simulation Analysis of Spatial Distribution of Roadway′s Surrounding Rock Stress

To get the spatial distribution characteristic of roadway's surrounding rock stress, circular section roadway was taken as a case study. The solution of stress was got by using complex function method, and roadway's surrounding rock stress field was analysed after the solution of mapping space was transformed into the solution of roadway space. As a result, the visual diagram of stress field distribution of roadway's surrounding rock was obtained, which could describe intuitively stress distribution of roadway's surrounding rock at any position. Considering the influence of different radius and side pressure coefficients on surrounding rock stress field, the following conclusions have been obtainded: the peak value and direction of circular roadway's surrounding rock stress has nothing to do with the radius; when side pressure coefficient is less than 1/3,the roof can produce tensile stress; when side pressure coefficient is more than 3, the surrounding rock in two sides can produce tensile stress. And the change rule of hoop stress, radial stress, shear stress and the maximum and minimum of stress have also been generated.     

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。     

Load Analysis of Butteting Bridges by CFD

An improved computational method for buffeting forces of long span bridges, which substitutes the traditional wind tunnel test with the bridge segment model for CFD method, is proposed. In the case study of Tsing Ma Bridge, the pressure distribution induced by the wind field of the bridge decks was simulated. The nodal buffeting forces were computed and the local stress responses were obtained according to the CFD simulation and the refined finite element model. Preparation for buffeting induced fatigue analysis of bridges and structural health monitoring are provided.     

风廓线雷达晴空大气返回信号功率谱特征分析

风廓线雷达谱参数是生成基本数据产品的重要参数,谱参数的正确估算是风廓线雷达运用的基础。基于晴空大气服从高斯分布的假设,本文给出了判断晴空大气返回信号功率谱服从高斯分布的2个判据,一是均方差值,二是面积相对比,利用这2个判据统计分析了风廓线雷达晴空探测资料服从高斯分布的情况,并分析了可能出现的带有杂波的大气返回信号以及杂波剔除方法,得出晴空大气返回信号功率谱服从高斯分布的结论,为快速估算晴空大气谱参数提供了新的方法,即功率谱的波峰位置对应多普勒频移,相对波峰位置的半功率点对应谱宽。