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Identifying aerodynamic damping based on the stochastic vibration responses of aero elastic building models can be performed using appropriate system identification techniques, which include frequency domain methods, time domain methods, and frequency-time domain methods. Among these methods, the random decrement method, one of the time domain methods, is broadly adopted to identify the aerodynamic damping of tall buildings and structures. Jeary introduced the random decrement technique to identify structural damping. Marukawa et al. employed the random decrement method to identify along-wind and across-wind aerodynamic dampings of tall buildings with rectangular sections. They analyzed the effects of building aspect ratio, side ratio, and structural damping on aerodynamic damping. Tamura et al. conducted a detailed study on the application of random decrement technique to identify the aerodynamic damping of super-tall buildings. Quan and Quan et al. adopted RDT to identify across-wind aerodynamic damping of the square-section tall buildings with different structural dampings in different wind fields and derived an empirical formula. These research results have been adopted into the related China Codes . Qin and Gu were the first researchers to introduce stochastic sub-space identification method into identification of aerodynamic parameters including aerodynamic stiffness and damping of long-span bridges, obtaining satisfying results. Compared with random decrement method, the stochastic sub-space identification method has more merits than RDT and MRDT and can overcome their main shortcomings i.e. weak noise-resistantce ability and need for large experimental data. Qin adopted this method to identify the aerodynamic damping of tall buildings.
Application to the codes
As stated above, although researchers have been focusing on across-wind loads on tall buildings for over 30 years now, the widely accepted database of across-wind loads and computation methods of equivalent static wind loads have not been developed yet. Moreover, only a few countries have adopted related contents and provisions in their codes.
Compared with the codes of other countries, the Architectural Association of Japan provides the best method for across-wind loads for structural design of tall buildings. Nevertheless, the formula for PSD of the across-wind force in the code can only be applied to tall buildings with aspect ratios of less than six, which seems difficult to meet the actual needs. Moreover, aerodynamic damping has not been considered in the method
. In the present load code for the design of building structures (GB50009-2001) of China, only a simple method for calculating vortex-induced resonance of chimney-like tall structures with a circular section is provided, which is not applicable to the wind-resistant design for tall buildings and structures in general. In the design specification titled “Specification for Steel Structure Design of Tall Buildings” , our related research results have been adopted.
Concluding remarks
With the continuing increase in the height of buildings, across-wind loads and effects have become increasingly important factors for the structural design of super-tall buildings and structures. The current paper reviews researches on across-wind loads and effects of super-tall buildings and structures, including the mechanism of across-wind loads and effects, across-wind aerodynamic forces, across-wind aerodynamic damping, and applications in the code. Consequently, some of our research achievements involving across-wind forces on typical buildings, across-wind aerodynamic damping of typical buildings, and applications to the Chinese Codes are presented. Finally, a case study of a real typical tower, where strong across-wind loads and effects may be observed, is introduced. The recent trend in constructing higher buildings and structures implies that wind engineering researchers will be faced with more new challenges, even problems they are currently unaware of. Therefore, more efforts are necessary to resolve engineering design problems, as well as to further the development of wind engineering.超高层建筑结构的横向风荷载效应摘要：随着建筑高度的不断增加，横向风荷载效应已经成为在超高层建筑结构设计中越来越重要的影响因素。高层建筑结构的横向风荷载效应被认为是由空气湍流、尾流以及空气流体结构相互作用所引起的，这些因素都是非常复杂的。虽然许多研究人员已经研究这个难题30多年了，但是横向风荷载效应的数据库以及等效静力风荷载的计算方法都还没有被发展出来，大多数国家在荷载规范里还没有相关的规定。超高层建筑结构的横向风荷载效应的研究成果主要包括横向风荷载的空气动力的确定以及气动阻尼的测定，数据库的开发和等效静力风荷载的理论方法等。在本文中，我们将首先审查目前国内外关于超高层建筑结构风荷载效应的研究。然后我们将阐述我们的研究成果。最后，我们会列举我们研究成果在超高层建筑结构中应用的的案例。