Wind Tunnel Tests Research On Turbulence Effects Of Wind Acting On Tall Buildings

Wind load is one of the control loads of tall building,and the characteristics of incoming flow have a great influence on the wind loads and wind-induced response of tall building,especially,turbulence intensity has a huge impact on the fluctuating wind effect of structure.Hence,researching the turbulent influence on the wind effects of tall buildings can be a better understanding of the wind loads and wind-induced response,which improves the wind-resistant behavior of tall buildings,it can be used as a reference for the wind-resistant design of tall buildings.Wind tunnel test is the most effective way to study the wind resistance of structures,however,the four categorie terrains of Load code in which the turbulence intensity hardly reached 20% at 1m high above the wind tunnel floor were mostly simulated in domestic studies,there are few studies on wind effects of high-rise buildings under high turbulence intensity,and therefore,further research about the turbulent influence on the wind effects of tall buildings is needed.A total of five flows,which were uniform flow,category B,category C,category D and flow D+,were simulated.The flow D+ which had almost the same mean wind profile of the category D and only the turbulence intensity was increased at each height,the turbulence intensity of 0.1m and 1.0m height were 26.2% and 8.3% in the category D terrain,and in the flow D+ the turbulence intensity of 0.1m and 1.0m height were 33.3% and 20.2%.Then the wind pressure and force tests of 6 rigid models(the breadth × length × height were 15 cm × 15 cm × 40 cm,15cm × 15 cm ×70cm,15cm×15cm×100cm,12cm×24cm×40cm,12cm×24cm×70cm,12cm×24cm×100cm)under the 5 flows have been carried out to study the influence of turbulence on the wind effects of tall buildings.The main work and achievements are as follows:First,the wind pressure tests of 6 rigid models under the 5 flows have been carried out,the turbulent effects on amplitude characteristics of wind pressure on tall buildings have been researched by analysing the distribution law of the wind pressure coefficient of typical measuring points on the facades of each model.The results show that when turbulence intensity of incident flow is obvious lager than that of category D,the maginitude of mean wind pressure coefficients which were obitained from all sides of any model in this flow becomes larger than that in the category D,and even a little positive pressure occurs on the side and backward surface in the flow D+.The mean along-wind drag of any model,which is one of the 4 models with 100 cm or 70 cm high,decreases with the turbulence intensity increasing,but the mean drag of the two 40 cm high models is increasing.Second,after the frequency-domain analysis of the test data has been done,the turbulent effects on frequency characteristics of wind pressure on tall buildings have been researched by analyzing the horizontal and vertical correlation coefficients,coherence function and power spectrum of the fluctuating wind pressure.With the increase of turbulence intensity,the horizontal and vertical correlation coefficient s of the measuring points on the windward surface decrease and that on the leeward surface increase,while there are two kinds of situation on the side surface: t he horizontal and vertical correlation coefficient s decrease if the reattachment of separated shear layers not oucurr;these correlation coefficients decrease in the separation section and increase in the reattachment section when the reattachment happens.In addition,an increase of turbulence intensity causes that the spectrum peak of measuring points on the side surface becomes more and more lower and the energy of pressure fluctuations occurs over a more broader range of frequency.Third,in order to research the turbulent effects on extreme value of wind pressure measured on the facades of tall buildings,the relationship between extreme wind pressure coefficients of the typical points and wind direction and the most unfavorable wind pressure coefficient s of typical point layers have been analyzed after the extreme wind pressure on the model is calculated in the peak factor method.When the magnitude of turbulence intensity in the wind field reaches that in the flow D+,not only the most unfavorable negative pressure coefficient s but also the most unfavorable positive pressure coefficient s should be focused on for the design of enclosure structures.Fourth,the effects of turbulence on the base moment response of tall builds have been studied through analyzing the base moments of 6 models obitained by high frequency force balance under the five flow conditions.The mean along-wind drag of body for any 100 cm or 70 cm high model in the flow D+ is smaller than that of terrain category D,but the results of two 40 cm high models are just the opposite,so it is emphasized that the influence of model height should be considered to determine the scale ratio in the wind tunnel tests of high-rise buildings.There still is a peak in the across-wind spectrum of any model under the flow D+,but the peak value is the smallest in the five flows,and the spectral peak is much smoother than that of the other four flows,the energy of high frequency becomes significantly greater as well.The results indicate that vortex shedding on the side surface is reduced as the intensity of incident turbulence has increased and the energy of base moment fluctuations is shifted to high frequency.Fifth,the basic theory of numerical simulation has been relatively detailed,three flows,category B category D and flow D+,ha ve been simulated by FLUENT,then steady simulation of six models and transient simulation of the two 100 cm modes have been carried out to study the influence of turbulence on the wind effects of tall buildings.The mean and fluctuating wind pressure coefficients of numerical simulation agree well with the wind tunnel test results,and the numerical simulation results can explain some phenomena of the wind tunnel test,which is a high-rise building in high turbulence intensity flow,to a certain extent.Sixth,it has been studied that how to determine the optimal sensor locations in full-scale measuring on tall buildings,and a new method based on data fusion is proposed in this paper.The measurement on a tall building was used as an example to illustrate the application of this method in practice,and the efficiency and accuracy of the data fusion method are verified by comparing with the fitness method.Finally,the main conclusions of this paper are summarized,and the further research on the turbulent influence of the wind effect of tall buildings is prospected.