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Title: Wind effects on large-scale buildings and structures : field measurements, wind tunnel tests and numerical prediction
Other Titles: Da xing jian zhu jie gou feng xiao ying de yuan xing shi ce, feng dong shi yan yu shu zhi mo ni yan jiu
大型建築結構風效應的原型實測, 風洞試驗與數值模擬研究
Authors: Fu, Jiyang (傅繼陽)
Department: Dept. of Building and Construction
Degree: Doctor of Philosophy
Issue Date: 2007
Publisher: City University of Hong Kong
Subjects: Buildings -- Aerodynamics
Wind resistant design
Wind-pressure -- Design
Notes: CityU Call Number: TH891.F8 2007
Includes bibliographical references (leaves 264-282)
Thesis (Ph.D.)--City University of Hong Kong, 2007
xx, 286 leaves : ill. ; 30 cm.
Type: Thesis
Abstract: Modern large-scale buildings and structures, such as super tall buildings and large roof structures, are usually constructed with innovative structural systems and high strength materials; tend to be more flexible and lightly damped than those in the past. As a consequence, the sensitivity of these buildings and structures to dynamic excitations, such as strong wind, has increased. Therefore, the major objective of this research study is to further the understanding of wind effects on and structural behavior of modern large-scale buildings and structures under strong wind actions by means of field measurements, wind tunnel tests and numerical prediction in order to apply such knowledge to design. This study includes three closely related parts. The first part involves establishing and developing a comprehensive field measurement program to produce a highly valuable set of field data such as wind speed, wind direction and acceleration responses etc. Field 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, 78 floors) in Shenzhen, Citic Plaza Tower (391 m, 80 floors) in Guangzhou and Jin Mao Building (420.5 m, 88 floors) in Shanghai. Shenzhen, Guangzhou and Shanghai are located near 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 five 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 and comparative study were conducted to investigate the characteristics of typhoon-generated wind and wind-induced vibrations of these super tall buildings under typhoon conditions. On the other hand, a direct comparison of model test results with real structural performance is always desirable. The full-scale measurement results are thus compared with wind tunnel test results, which can aid in evaluating the accuracy of the model test results and the adequacy of the techniques used in the wind tunnel tests. Meanwhile, the wind tunnel tests can also provide detailed and additional results that are not available from the field measurements so that the understanding of dynamic behaviour of tall buildings can be improved. Wind tunnel testing is an effective method for investigating wind effects on buildings and structures. In part 2, detailed wind tunnel studies on the characteristics of wind loads and wind-induced response of three large roof structures are conducted. First, the characteristics of wind loads on a large cantilevered flat roof are presented and discussed on the basis of the wind tunnel measurements; furthermore, according to the characteristics of wind loads on the roof, an aerodynamic solution to minimize the peak suctions by venting the leading edges and corners of the roof is recommended, and the effectiveness of the strategy is demonstrated through the obtained wind tunnel test results. On the other hand, wind tunnel test is also conducted for a large gymnasium structure, special attention is paid to the characteristics of fluctuating wind pressures in different zones on the roof and the applicability of the quasi-steady approach is discussed in detail; furthermore, based on these results, an empirical formula for estimating the minimum pressure coefficients on the roof, using a peak factor approach, is presented, and the effectiveness of the proposed formula is demonstrated through comparison of the results determined by the formula and those obtained from the wind tunnel tests. Finally, part 2 presents a new description of the equivalent static wind loads (ESWLs) on long-span roof structures based on the load-response-correlation (LRC) approach. The ESWL for a given peak displacement response is expressed in terms of the mean and dynamic components; and the wind loading inputs are derived from multiple point pressure measurements on rigid structural models. It is noteworthy that in the proposed approach, the total dynamic response is directly calculated by the complete quadratic combination (CQC) approach, which is not separated into the background and resonant responses any longer; and the contributions of multimode response and modal response correlations are taken into consideration. Moreover, there is no need to directly calculate the correlation of the load and response, which is difficult to be determined by conventional methods. Meanwhile, an extra-long-span roof structure which is the world’s longest spatial lattice structure is considered to illustrate the determination of the ESWLs and to demonstrate its effectiveness in the design and analysis of long-span roof structures. It is shown through the example that the proposed approach can be used in conjunction with wind tunnel tests in predicting the response components not directly measured during the tests and providing the design loads accurately. The application of artificial neural networks (ANNs) to solve wind engineering problems has received increasing interests in recent years. Part 3, taking two typical large roof structures as examples, mainly focuses on the development of an effective tool to accurately estimate wind-induced pressures on large roof structures. A backpropagation neural network (BPNN) approach and a fuzzy neural network (FNN) approach are employed for this purpose. In order to achieve the expected objective, simultaneous pressure measurements are made on the large roof structures to obtain wind-induced pressure data for training, developing and testing the ANN models. Comparisons of the prediction results by the ANN approaches and those from the wind tunnel tests are made to examine the performance of the ANN models, which demonstrates that the ANN approaches can successfully predict the pressures on the entire surfaces of the large roofs on the basis of wind tunnel pressure measurements from a certain number of pressure taps. This part is concerned with not only the prediction of the wind-induced pressures on the large roof structures, but also the performance of the ANN approaches for solving wind engineering problems. It is shown through this study that the developed ANN approaches can be served as an effective tool for the design and analysis of wind effects on large roof structures. The field measurements can provide reliable but limited information. The wind tunnel tests can generate detailed and additional results that are not available from the field measurements. On the other hand, the ANN approach can be used as a supplement to wind tunnel tests to accurately estimate wind-induced pressures on buildings and structures. Furthermore, the ESWL approach can be used in conjunction with wind tunnel tests in predicting the response components not directly measured during the tests and providing the design loads accurately. Therefore, the field measurements, the wind tunnel tests, the ANN approach and the ESWL approach are complementary so that the understanding of wind effects on buildings and structures 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 large-scale buildings and structures.
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