Comparative Research On The Wind Effects Of 90° Helical And Square Tall Buildings

With the rapid development of social productivity,high-rise buildings stand all over the world,and the wind load has become the main control load in the design of high-rise buildings.For the wind sensitive structures such as high-rise buildings with low frequency and small damping ratio,it is easy to couple with the wind and generate aero-elastic effects,and cause strong wind-induced response of the structure.In order to reduce the wind-induced response and not to reduce the height of the structure,it is useful to find a suitable building shape,which could not only achieve the pursuit of architectural aesthetics,but also could change the sensitivity of the structure to the wind.In this paper,the wind tunnel tests were carried out to study the wind load and aero-elastic effect of two types of buildings.The main works of this paper are showed detailedly as follows:Through the pressure measurement test of rigid model,the mean and fluctuating wind pressure distribution of each facade under different wind direction angles of the two models are compared,and the mean and fluctuating local wind coefficients of the X axis and the base bending moment coefficient caused by the wind force of the X axis are studied.The results show that the wind loads of the two types of buildings along the wind direction are consistent,and the wind loads of the helical model is better than that of the square model.Based on the analysis of the power spectrum,it is found that there is a narrow peak in the power spectrum of square model in the crosswind direction,which didn’t appear in the helical model.Based on the study of the vertical correlation and coherence of the fluctuating wind,it is found that the fluid movement of the helical building at different heights of the crosswind direction is more independent.90° helical and square section models with the same dynamic characteristics have been designed and fabricated,and the dynamic characteristics of two elastic models were identified successfully.Wind tunnel texts were carried out for the elastic models and the various conditions between the along-wind and crosswind aerodynamic damping ratio were identified by the random decrement technique.Wavelet transform was used to decouple modal to identify aerodynamic damping ratio of the working conditions with the phenomenon of beats.The result indicated that the change regulation between aerodynamic damping ratio and reduced wind velocity of square model in accordance with relevant research results;the cross-wind aerodynamic damping ratio of 90 ° helical model has a slight rise in the low reduced wind velocity range,being stable in the range of 0 with the increase of reduced wind speed,the along-wind aerodynamic damping ratio of 90°helical model shows the regulation which is similar to square model,but it is smaller at high reduced wind velocity.The RMS acceleration and peak acceleration measured by aero-elastic model are studiedand analyzed.The RMS acceleration is calculated based on the results of rigid model test by two methods,one is taking aerodynamic damping ratio into account and another is not.The results show that the response of helical building in crosswind direction is smaller than that of square building.The calculated results of square building by taking aerodynamic damping ratio into account are in good agreement with that measured by aero-elastic model.The results from various methods of helical building are similar.In this paper,the equivalent static wind loads of two types of buildings are also compared,its change rule with wind direction and.aerodynamic damping ratio is similar to acceleration response.