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%。     

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.     

Simulation study of stochastic fluctuating wind field for wind turbine blades

The differences of the wind field model between wind turbines and common architectures are investigated. It is indicated that substantial frequency contents are transferred to rotor rotation frequency and its harmonics due to the periodic motions of blade. According to standard von Karman power spectral density (PSD) model and rotationally sampled PSD model, the PSD matrix for turbulence on blades of wind turbine is setup. The longitudinal turbulence’s time serials is simulated based on the superimposition of harmonic waves.     

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.     

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.     

The input load and its influence factors of wind turbine based on variational wind speed

The auto regressive (AR) method is applied to build the model of wind speed in wind field,and with the model, the wind time-history is obtained. The Glauert method is used to calculate time-varying input load,such as the time histories of thrust and torque of the wind turbine under the condition of variational wind speed. Based on statistical analysis,the design loading spectrum and rain flow histogram of the loads are obtained. The effects of wheel blade parameters on the input load under the condition of variational wind speed are analyzed,and the average loads of thrust and torque are obviously affected by the pitch angle. When the pitch angle increases,the loads of thrust and torque both decrease,meanwhile the amplitude of thrust first increases then decreases,while the amplitude of torque decreases monotonously. The thrust is obviously affected by twist and attack angles of blade while the torque is less affected by the twist and attack angles of the blade. The results lay foundations for reliability design,load control of the wind turbine as well as the parameter optimum of the wheel blade aerofoil under the real wind condition.     

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。     

Research of Wind Load on the Surface of YingLi Building in Chongqing

Considering the complicated distribution of wind load on the surface of the tall building, the 1:300 scale model test of YingLi building is completed in the No.2 environment wind tunnel, which belongs to the State Key Lab of Environmental Engineering College, Beijing University. Based on the calculation and analysis of the test results, this paper discusses the coefficient of wind-induced vibration and shape coefficient of wind load , gives the maximum and minimum value of surface wind load, which can be used for the wind resistant design and insure the security of the building under 100 years return period wind load.     

Evaluation and analysis on the extreme load of wind turbine blade

According to the international standard of German GL 2010, a wind turbine of 850 kW is applied to the corresponding wind power generation unit and its situation of pneumatic rated power and sympathetic vibration is analyzed with Bladed software. The result verifies the reliability of wind turbine in operation. Further, after all the wind regimes in GL standard are calculated and analyzed comparatively, the extreme wind regimes which mainly influence the aerodynamic performance of the wind blade are obtained, namely, Dlc4.2b, Dlc1.3a, etc. Later on, the evaluation criteria of wind turbine blade taking the load of blade root as standard are established and implemented with the built-in demo data of Bladed software to testify its generality. Then based on the above evaluation criteria, extreme loads of the 850 kW’s blade root is computed and it’s found the extreme swing load is 353 663 N·m, which is 2.5% lower than its designed value. The result verifies the security of the blade in operation and the reliability of the evaluation criteria.     

Kinematic displacements control simulation and configuration optimizing of six DOFs parallel mechanism for wind tunnel experimental platform

6PUUS parallel mechanism for wind tunnel experimental platform is studied,and its operational principle and movement requirements are analyzed. According to the theory of inverse kinematics and spatial Descartes coordinate transformation of 6PUUS parallel mechanism,kinematic positions of pull rods and kinematic interpolation paths of sliders are derived base on Euler angle of any experimental pose. The detailed algorithm for spatial position interpolation is summarized and its validity is proved by a simulation case in the end. Key factors of nonoccurrence of sliders collision at work are concluded by means of simulation analysis,and combined with the variety of mechanism parameters,optimized size parameters of pull rods and movable platform are also found. It is proved that this method and the simulation algorithm are useful and helpful for the optimizing design and singularity poses analysis of the parallel mechanism.     

Influence Threshold Analysis on Railway Over-Cross Tunnels

Double-track railway over-cross tunnels were stuied by numerical simulation and regression analysis. A series of research on the influence of the construction of newly built tunnel to the existing one in different surrounding rock grades was carried out. According to the numerical simulation, 48 mechanical models were established, which considered various clearance, rock conditions and different construction sequences（building above or beneath existing one）. Based on regression analysis on the calculation results from the 48 models, the deformation prediction formulas for the existing tunnel's surrounding rocks and ballast bed were deduced. According to the high-speed rail allowed standard of roadbed deformation during operation, the minimum clear distance value by which the existing tunnel's operation would not be affected was recommended. Some analysis on the surrounding rock pressure's variation of the existing tunnel caused by new tunnel construction was done. Taking the variation amplitude as the evaluation criteria, a critical value of influenced clearance for railway over-crossing tunnels project is provided. Meanwhile, the results found that the tunnel cross the building had a smaller impact on itself compared with that of the tunnel which goes through the building.     

Characteristics of Interference Effects on Local Pressure of Two Square Tall Buildings in Tandem Arrangement

Wind tunnel tests were carried out to study the wind pressure on principal square building adjacent to another one in tandem. The interference effects on local pressure of the principal building were analyzed with different positions and heights of interfering building. It is shown that as height ratio is fixed, mean pressures on windward face are suctions when spacing ratio is less than 3, otherwise they are positive. The magnitudes of mean suctions on the side and leeward faces and fluctuating pressures on each face all get their maximums when spacing ratio is 3. As height ratios change, the magnitudes of mean suction on windward face increase with height ratio, meanwhile, the magnitudes on other faces obtain their minimums as the height ratio is 1.0 and the spacing ratio is less than 3. The fluctuating pressures on the windward and side faces get their maximums and that on the leeward face reaches its minimum as the height ratio is 1.0. When the spacing ratio is greater than 3, mean pressures on each face decrease, while fluctuating pressures on the windward and side faces increase as the height ratio increases, and the fluctuating pressures on the leeward face get the minimum when the height ratio is 1.0.     

Calculation and Analysis of Basic Wind Pressure Value Based on Gumbel Distribution

In order to find out the current basic wind pressure in China, the parameters were estimated based on Gumbel distribution by statistically analyzing the annual maximum values of wind speed of 159 typical cities in China between 1951 and 2008. The basic wind pressure values for 10-year, 50-year and 100-year return periods were calculated based on moment method and Gumbel method, respectively. The distribution function was tested by the Kolmogorov criterion. Finally, the calculation results were compared with those in current design codes and the results of the correlative literature. The results show that basic wind pressure values worked out by Gumbel method are better than those by moment method in most cases when the statistic of the annual maximum values of wind speed is conducted and analyzed by Gumbel distribution. There are significant differences between the basic wind pressure values for 10-year, 50-year and 100-year return periods in Loading Code for Design of Building Structures and the results calculated with the annual maximum values of wind speed in recent decades, which shows that the sample data in Loading Code for Design of Building Structures are relatively insufficient and cannot reflect the present true condition in China. Therefore, basic wind pressure value should be revised accordingly.     

Analysis on the moisture migration of subgrade soil under effect of temperature gradient

A moisture migration test for unsaturated clayey loess along the SHERFPL is done to understand the water migration of soil under a closed system in freezing condition. The experimental data shows that the temperature decreases with the slope degrading and eventually reaches a stable temperature gradient. Temperature potential has little effect on soil’s moisture migration. The formation of the gradient of soil’s water content is mainly caused by temperature gradient. With temperature decreasing to the freezing temperature of soil, the unfrozen water content decreases quickly in frozen zone. Such decrease results in the great drop of matric potential, making unfrozen water migrate toward the lower temperature zone. Based on the model test, a coupled heat-fluid transport equation is built and simulated by a two-dimensional finite element model, from which the temperature and moisture field of the specimen under closed system are obtained. It is found that the obtained results are closely agreed with the experimental data. Therefore, the model is adapted to simulate the variations of temperature and moisture of subgrade soil during freezing process in seasonal frozen ground, which can provide the basis for inhibiting frost heave.     

Parametric Analysis of the Cable''s Vortex-Induced Vibration of Submerged Floating Tunnel

The cable's motion was modeled by a spring-mass-damper system. The flow field was calculated by RSM combined with the enhanced wall function model and the vibration equation of the cable was solved by the Four Step Runge-Kutta Algorithm, which was written into FLUENT software to be analyzed. It was adopted to analyse the factors influencing vortex-induced vibration of submerged floating tunnel cable, such as mass ratio, damping ratio of the cable and whether to consider streamline movement. The main conclusion included: mass ratio has little influence on the transverse vortex induced vibration amplitude of the cable, but has a big influence on the region of the reduced velocity; damping ratio almost has little influence on the region of the reduced velocity of cable's viv, but has an influence on the cable's vibration amplitude significantly; In the case of low-mass ratio, considered the impact of the cable streamline movement, the transverse vortex-induced vibration amplitude is bigger than not considered the case.     

Earth Pressure on Retaining Structure of Round Deep Foundation Pit in Sand-cobble Soils

In recent years, the round deep foundation pits engineering gradually appears in Chengdu Plain whose strata are mainly sand-cobble soils. However, there are no proper calculation methods of earth pressure in retaining structure like this and distribution mode of the pressure is unknown. With the use of elastoplastic numerical simulation method involved in interaction between retaining piles and soil, the distribution law of earth pressure of the round deep foundation pit retaining structure is determined. The result shows that distribution of earth pressure on a pile is triangular and the maximum lies in the location of pit bottom, but the average value of the pressure is less than Rankine active earth pressure. Model tests have also been carried out so as to verify the distribution mode. As for the test model, the values obtained by the numerical simulation method are approximately similar to the experimental results in the distribution law as a whole, which to some degree suggests the rationality of the numerical simulation results.     

Finite Element Analysis on Interaction of Neighboring Highway Tunnels under Construction

Recently, the construction of neighboring highway tunnels with small interval gets more and more in China. The construction of such tunnels proceeds usually by excavating one after another. The second tunnel is constructed with the surrounding rock disturbed by the first one. And the construction of second tunnel also has effect on the first excavated one. For revealing the interaction laws of such tunnel construction in combination with the engineering practice of Lanfeng tunnel at Jinshan Road in Chongqing, The FE numerical simulation analysis was used to study the characters of surrounding rock deformation, stress field, and plastic zone of the tunnel. From this analysis, it clearly shows that the excavation of second tunnel has significant influence on the first one. This study provides a scientific basis for design and excavation of neighboring highway tunnels.     

Optimization of Helix Intake Port Based on Numerical Simulation

With numerical simulation, an analysis is done on the three-dimension air flow in the helix intake port of a diesel engine. The anthors acquire the distribution of characteristic parameters of air in the port, such as velocity, pressure, turbulence kinetic energy, as well as the flow coefficient and rotate moment around the erect axes at the outlet. The results of simulation indicate that the negotiability of the port is very good while the ability of forming eddy can be enhanced, so several improve measures have been put forward. Comparing with simulation results of these measures, it finds out that the method of combining increase the distance between the definition curve of volute cavity and central line of valve protruding support as well as increase the eddy shell angle can obviously enhance the ability of forming eddy, which is an efficient and rational method.