Aerodynamic Load Characteristics And Strategy Of Reguction Of A Class Of Tapered Super-tall Buildings

With the development of economic construction and science technology, super high-rise buildings have been growing rapidly in the developed countries around the world. These super high-rise buildings are characteristic of high flexibility, light weight, small damping and so on, which make the wind load of such buildings play a key role in the structural design. Generally speaking, there are two measures to control the wind load of super high-rise buildings: aerodynamic strategy and Tuned Mass Damper. In our country, because of the ultralimit inspection, it is difficult to add Tuned Mass Damper to concrete engineering practice. As a result, aerodynamic strategy appears extraordinary important.First, based on the experiment of synchronous pressure measurement, this paper gives a thoroughgoing study about the effect of the three aerodynamic strategies on changing the features of the wind loads and lowing wind-induced response. The three aerodynamic strategies are as follows: cross-section tapered, cross-section bevel cornered, and opening corridor ventilation. Second, through the experiment of high frequency force balance, it applies openning corridor ventilation to the two practical high-rise buildings (Guangzhou West tower and Tianjin Gaoyin 117 Building)to investigate the effect of reducing wind-induced response.The main conclusions of this study can be summarized as follows:1) In the test, there are two vortex sheddings on the squared cross-section, named major and minor vortex shedding, and it excludes the cause of the height of the building. Major vortex shedding is the traditional vortex shedding of squared cross-section, and the frequency and power of minor vortex shedding was lower than the major one.2) Tapering of the cross-section (i.e. increasing Taper ratio) abates the energy of major vortex shedding, attenuating the coherence around the convert frequency of such shedding. However, the frequency of major vortex shedding is magnified, so the peak of it moves towards right, which makes the power spectum desitinies of base bending moment around major vortex shedding of tapered structrue bigger than the standard one. When we compute response of base bending moment and peak acceleration, we should realize that if the fundamental frequency is nearby the frequency of major vortex shedding, the response of tapered structure will be larger than before.3) Cross-section bevel cornered weakens the major vortex shedding, and coherence around whose frequency is reduced . Thus the aerodynamic strategy can reflect good aerodynamic effect at a wide range of period ratio variation, especially remarkable when the frequence of computing the wind effect being quite close to the frequence of major vortex shedding.4) Opening corridor ventilation at the corner of different floors brings down the strength of power spectum desitinies of base bending moment at all ranges of frequency in defferent degree, the frequency around the major vortex shedding gets most reduced. The aerodynamic strategy performs the best in reducing wind-induced responses when cross-section is square, also the effect is a little bit poorer when cross-section is bevel cornered, because cross-section bevel cornered weakens the major vortex shedding. Comprehensively compared, the open corridor ventilation in the middle part of model is the best, then the upside and underpart of the model.5) As the vortex shedding frequency in 50~100-year return period being nearly to the fundamental frequency of Guangzhou West Tower, opening corridor ventilation at the refuge and equipment storey could obtain absolutely good effect. The appearance of Tianjin Gaoyin 117 Building is tapered and cross-section bevel cornered, whose effect of opening corridor ventilation is poorer than Guangzhou West Tower's, which further evidences the 4th conclusion above.