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Title: Dynamic characteristics and wind-induced responses of a super tall building
Other Titles: Chao gao ceng jian zhu de dong li te xing ji feng zhi zhen dong yan jiu
Authors: Liu, Pengfei (劉鵬飛)
Department: Dept. of Building and Construction
Degree: Master of Philosophy
Issue Date: 2007
Publisher: City University of Hong Kong
Subjects: Tall buildings -- Aerodynamics
Notes: CityU Call Number: TH891.L58 2007
Includes bibliographical references (leaves 97-103)
Thesis (M.Phil.)--City University of Hong Kong, 2007
x, 104 leaves : ill. ; 30 cm.
Type: Thesis
Abstract: This thesis describes a combined experimental and numerical investigation of wind effects on a super tall building, Di Wang Tower (325m high with 79 floors) located in downtown Shenzhen, China. The major objective of this research study is to further the understanding of dynamic characteristics and wind-induced responses of the tall building through full-scale measurements and numerical simulation. First, the optimal placements of sensors for vibration measurements of super tall buildings were investigated in this study. An effective approach based on the uniform design method is developed to seek the possible optimal locations of sensors for obtaining the dynamic characteristics of tall building structures. The proposed approach is different from conventional methods. Di Wang Tower in Shenzhen was considered as an example to illustrate the application and effectiveness of the proposed method. It was shown through the example that this method can dramatically reduce the computational efforts for determining the optimal locations of sensors. Meanwhile, it was also demonstrated that the developed method is simple and effective. Second, full-scale measurements of wind effects on Di Wang Tower were conducted during the passage of Typhoon Chanzhu on 16-17, May 2006. The field data such as wind speed, wind direction and acceleration responses were simultaneously measured from this super tall building during the typhoon. The full-scale measurements were compared with those from wind tunnel tests. The amplitude-dependent damping ratios were obtained by the random decrement technique based on the measured acceleration data. It was found from the full-scale measurement results that the von- Karman spectrum could describe the energy distribution of fluctuating wind speed fairly well above typical urban areas. It was also found that there is a tendency for both the turbulence intensity and the gust factor to decrease with increase in mean wind speed. The field measured acceleration responses were found to be consistent with the model test results, thus verifying the accuracy of the wind tunnel test techniques. Actual damping values of a building can only be determined through full-scale tests. Therefore, an empirical model of amplitude-dependent damping ratio for Di Wang Tower was proposed in the third part of this research study. This damping model was established based on our long term full-scale measurements of the wind-induced responses of the tall building. In order to evaluate the wind effects on the tall building, the wind-induced responses of the super tall building were numerically estimated in both time domain and frequency domain. Computational results showed that the effects of amplitude-dependent damping on the along-wind and across-wind responses of the building are significant. Constant damping ratios as recommended in current design codes and standards for the analysis of wind-induced vibrations of tall buildings may lead to significant under-estimation of the responses. Through numerical studies of the wind-induced vibration of this tall building under several wind loading cases, the research work in this part concentrated on investigation of the effects of amplitude-dependent damping on the wind-induced responses of Di Wang Tower. Through the three integrated research parts, identification of dynamic characteristics and evaluation of wind effects on the super tall building (Di Wang Tower) were conducted comprehensively in this research study. The outcome of this study is expected to be of interest and practical use to professionals and researchers involved in the analysis and design of tall building structures.
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