Study On Wind-induced Response And Wind Codes Of The High-rise Building

Generally, high-rise buildings have three important characteristics that are lowquality of unit volume (density), low base-frequency and low damping. As a result,they are more vulnerable to wind-induced damage, sometimes making the wind loadbe the critical factor in design of high-rise building. In July2011, China Academy ofBuilding Research completed the draft amendment for the “Load code for the designof building structures”(GB50009-201x). As it is known, loading code is the basicguidance of structural design, so it is of great importance to analyze and evaluate thenewly revised code. Based on this purpose, this thesis compares the draft of the newcode with the so-called old code, and other codes abroad. Besides, the effect of highermodes on wind-induced response of high-rise building is analyzed with considering ofsome primary dynamic parameters. In summary, the following tasks were completed:(1)The draft for the “Load code for the design of building structures”(GB50009-201x) was introduced and compared with the Chinese code(GB50009-2001), the US code (ASCE7-10), the Australian code (AS1170.2),and theCanadian code (NBC2005) in average wind speed profiles, turbulence intensity, peakfactor and wind vibration coefficient. Especially, the along-wind vibration coefficientin the draft for the “Load code for the design of building structures”(GB50009-201x)was deduced in detail. First, in the draft for the newly revised code, the gradient windheight of the C-class and D-class landforms increase to450m and550m respectivelywhile the landform index value changes to0.15, making the wind speed profile morereasonable. Second, the turbulence intensity has been increased to some extent, but itis still less than the corresponding value in corresponding foreign codes. Third, thespecified peak factor is2.5, however, in major codes abroad this value is generallybetween3.0and5.0. As a result, if we calculate the wind-induced dynamic responseaccording to our Chinese code, the result is prone to be smaller. Fourth, windvibration coefficient is divided into two parts: the resonance component and thebackground component, which makes our standards more international.(2)The along-wind maximum acceleration of vertex formula was driven byadopting the new wind vibration coefficient that is in the form of the resonancecomponent factor and the background component factor. An example was given in thethesis, and it was found that the calculation result was larger than that when referring to the “Technical specification for steel structure of tall buildings”, and closer to thatreferring to the load code abroad.(3)The thesis analyzed the effect of higher modes on the wind-induced dynamicresponse of super-high-rise building with consideration of a number of parame-ters(peak factor, damping ratio, the first vibration mode index, the fundamental fre-quency and the density).The impacts of these parameters on the wind-induced dy-namic response were investigated.The results showed that for hybrid structure ofsteel-steel concrete and steel high-rise buildings, the displacement response is able tomeet the engineering requirements by only taking the first vibration mode into con-sideration while the higher modes effects can be ignored. However, when it comes tothe acceleration response, higher modes are generally accounted for the first mode of5%-20%that should necessarily be taken into consideration.