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Title: Field measurements and numerical study of wind effects on tall buildings
Other Titles: Gao ceng jian zhu feng xiao ying de shi ce yu ji suan fen xi
Authors: Wu, Jiurong (吳玖榮)
Department: Dept. of Building and Construction
Degree: Doctor of Philosophy
Issue Date: 2006
Publisher: City University of Hong Kong
Subjects: Tall buildings -- Aerodynamics
Notes: CityU Call Number: TA654.5.W8 2006
Includes bibliographical references (leaves 266-280)
Thesis (Ph.D.)--City University of Hong Kong, 2006
xxi, 284 leaves : ill. ; 30 cm.
Type: Thesis
Abstract: This thesis describes a combined experimental and numerical investigation of wind effects on tall buildings. The major objective of this research study is to further the understanding of wind effects on and dynamic characteristics of tall buildings through field monitoring and numerical analysis as well as correlation study between the full-scale measurements and the simulation results. This study includes three closely related parts. The first part involves establishing and developing a comprehensive field measurement program, which is the basis of this study, to produce a highly valuable set of field data including wind speed and direction, wind-induced displacement and acceleration responses. Full-scale measurement is considered to be the most reliable method for evaluating wind effects on buildings and structures. This project aims to obtain reliable field data that represents the real-time wind loading and wind-induced vibrations of three super tall buildings: Di-Wang Tower (384 m high with 79 floors) in Shenzhen, CITIC Plaza (382.5 m, 80 floors) and Guangdong International Building (200 m, 63 floors) in Guangzhou. Shenzhen and Guangzhou are located at the edge of the most active typhoon generating area in the world. Hence, these super tall buildings that are among the highest in the world may be susceptible to severe wind actions induced by typhoons. This makes a comprehensive field study of wind effects on the super tall buildings under typhoon conditions particularly important and necessary. Significant field data have been measured from the instrumented tall buildings over the last three years, including measurements made during the passage of several typhoons. Analysis techniques and computer programs to deal with the field data were developed. Detailed analysis of the field data was conducted to investigate the characteristics of typhoon-generated wind and wind-induced vibrations of these super tall buildings under typhoon conditions. The dynamic characteristics were determined from the field measurements. In addition, time-frequency analysis was carried out by Hilbert-Huang Technique to investigate the non-stationary features of the signals which were simultaneously and continuously measured from Di Wang Tower with anemometers, accelerometers and Global Position System (GPS) during a typhoon. The field study conducted provides useful information on wind effects and structural responses as well as on the dynamic characteristics of the instrumented super tall buildings. In part 2, a detailed study on correlating the dynamic characteristics from the field measurements and numerical analysis was carried out. In parallel with the field study, 3D finite element models were established to model the structural behavior of the super tall buildings. The measurements and calculations of the dynamic characteristics were then compared to identify possible modelling errors and where the numerical models need to be improved. Furthermore, an eigensensitivity-based Finite Element (FE) model updating procedure was presented in this study. The developed method was further applied to FE model updating of a high-rise structure and was used for structural parameter identification and damage detection of a steel frame structure based on ambient vibration measurements. Comparisons between the FE model updated results and the experimental data were made to verify the effectiveness of the developed eigen-sensitivity based FE model updating procedure. Part 3 involves developing efficient and practical computational framework for estimation of wind-induced vibrations of tall buildings. Several methods have been developed in literature for calculating the responses of tall buildings under winds. However, very few of these have been calibrated against reliable data from actual buildings. Reliable measurements of the responses of the three tall buildings to a large range of wind speeds and directions have been made, which allowed us to use the data to assess the accuracy of various existing computational methods, in particular the empirical formulas adopted in several well-known wind loading codes for predicting the across-wind and torsional responses of tall buildings, which provides an excellent opportunity to evaluate the adequacy of codes of practice. Moreover, simplified analytical formulas were derived in this study to estimate windinduced across-wind response of tall buildings. Good agreements were found between the results by the proposed formulas with the experimental data and those by the wind loading codes. Wind-induced lateral-torsional coupled response of a representative tall building was numerically evaluated by setting various parameters such as eccentricities in centers of mass and/or rigidity and adopting different torsional to lateral stiffness ratios. The eccentricity effects on the lateral-torsional motions were studied comprehensively in both frequency and time domain. The computational results and associated comparative study show that the proposed simplified analytical formulas and the developed computational framework for the lateral-torsional coupled response analysis will enable structural engineers in the preliminary design stage to assess the serviceability of tall buildings, potential structural vibration problems and the need for a detailed wind tunnel test. The full-scale measurements provided very useful information on wind loading and responses of the instrumented super tall buildings. Furthermore, the experimental results were used to refine the numerical models for structural analysis and design. The field data also provided essential information for developing computational methods and design standards or guidelines for super tall buildings. On the other hand, the numerical simulation generated detailed and additional results that were not available from the field measurements, so that the understanding of wind effects on the super tall buildings can be improved. The outcome of this study is expected to be of considerable interest and practical use to professionals and researchers involved in the design of super tall buildings.
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