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Title: Static and dynamic analysis of a long-span spatial lattice roof structure
Other Titles: Da kua du wang jia jie gou de jing li yu dong li fen xi
Authors: Yeung, Ngai Hung Maggie (楊藝紅)
Department: Dept. of Building and Construction
Degree: Master of Philosophy
Issue Date: 2007
Publisher: City University of Hong Kong
Subjects: Roofing
Roofs -- Design and construction
Notes: CityU Call Number: TH2391.Y48 2007
Includes bibliographical references (leaves 126-134)
Thesis (M.Phil.)--City University of Hong Kong, 2007
xv, 134 leaves : ill. (some col.) ; 30 cm.
Type: Thesis
Abstract: The 486m-long roof structure of the Shenzhen Citizens Center is the longest spatial lattice structure in the world. The design criteria of the extra-long-span roof are not fully covered by any code or standard in the world. Shenzhen is close to the most active typhoon generating area in the world and frequent typhoon attack is likely to occur. All these facts make a detailed study to investigate its structural behavior under static and dynamic loads of particular importance and necessity. This study is thus concerned with the static and dynamic analysis of the roof structure. This dissertation is divided into four parts. First, a wind tunnel experiment was conducted to investigate wind effects on the roof structure. It was found that the design of the extra-long-span roof structure was dominated by negative wind pressures (suctions). Larger mean pressure coefficients were measured at the windward eaves of the roof, and the pressure level decreased rapidly with going downwind to the rear edges of the roof. The distribution characteristics of the worst rms and minimum pressure coefficients were similar to those of the mean pressure coefficients. The second part presents the static analysis of the roof under the action of the equivalent static loads (ESWLs). The loads on the structure caused by the buffeting action of wind were analyzed using the gust loading factor (GLF) approach. Eight directions of incident wind were considered in the static analysis based on the wind tunnel test results. Comprehensive results such as nodal displacements, support reaction forces and member stress were presented and discussed. It was found that, due to the structural geometry of the roof, large uplifting deformation may be induced on the windward part of the roof. And the vertical structural deformation would be the severest under the approaching wind direction which is perpendicular to the longitudinal direction of the roof. The third part is concerned with the free vibration analysis of the roof structure. Dynamic modal analysis with consideration of 30 mode shapes was carried out for the roof. Small differences of natural frequency between each mode indicate that there was a significant amount of coupling vibration. Thus, the complete quadratic combination (CQC) method for predicting the dynamic responses of the roof was recommended. The dominant vibration modes in longitudinal direction x or transverse direction y were found to be concentrated on lower modes while those in the vertical direction z were focused on higher modes. Furthermore, an increase in roof surface loading led to a decrease in the natural frequencies of the roof structure. Due to errors in the numerical model of the structure, there are noticeable differences between the natural frequencies obtained from full-scale measurements and those predicted by the finite element method (FEM). The final part presents seismic analysis of the structure. By comparing the base shear coefficient and the ratios of effective mass to total mass with consideration of 15 and 30 modes, respectively, it was concluded that the CQC method should be adapted in the seismic analysis. From the displacement distribution analysis, it was found that the front face of the middle part of the roof has higher vertical displacement responses than those at the rear face. The computational results show that comparing with the roof’s selfweight and the design earthquake forces, both the vertical displacement responses and axial forces were dominated by the design wind loads. Moreover, the seismic responses of the structure due to the wave passage effect were investigated in detail. It was shown from the computational results that the wave passage effect has a significant influence on the seismic responses of the extra-long span structure. The wind tunnel experiment provides very useful information on wind effects on the long-span structure. Furthermore, the available field measurement results were used to examine the accuracy of the numerical analysis of the structure. On the other hand, the numerical analysis generated detailed and additional results that were not available from the wind tunnel test and the full-scale measurements, so that the understanding of wind effects on the long-span roof structure can be improved. Furthermore, the detailed seismic response analysis of the structure provided very useful information and results. Therefore, the outcome of this combined experimental and numerical study is expected to be valuable for design and construction of other large complex long-span structures in the future.
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