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PROCEEDINGS OF THE ELEVENTH INTERNATIONAL CONFERENCE ON CIVIL, STRUCTURAL AND ENVIRONMENTAL ENGINEERING COMPUTING
Edited by: B.H.V. Topping
Dynamic Analysis of Cable Domes
J. Song and Q.L. Zhang
Department of Building Engineering, Tongji University, Shanghai, China
J. Song, Q.L. Zhang, "Dynamic Analysis of Cable Domes", in B.H.V. Topping, (Editor), "Proceedings of the Eleventh International Conference on Civil, Structural and Environmental Engineering Computing", Civil-Comp Press, Stirlingshire, UK, Paper 155, 2007. doi:10.4203/ccp.86.155
Keywords: spatial structure, cable dome, initial pre-stress, dynamic property, mode, frequency.
The cable dome is a space structure, which consists of tension cables, compression struts and membrane. As an effective structural system to withstand the external forces, it has the perfect property of new material and technology. It is the highest level of spatial type. The concept of 'tensegrity' was first conceived by Fuller , which reflected his idea that 'nature relies on continuous tension to embrace island compression elements'. Tensegrity consists of discontinuous bars or compression members suspended by a continuous network of cables or pure tension members. Nowadays the cable dome has been applied in many well-known long-span structures in the world, such as the 1986 Korean Gymnastics and Fencing Arenas, the 1988 American Redbird Arena in Illinois State University, the Atlanta Georgia Dome and so on [1,2,3]. All these large span gymnasiums and exhibit halls built in cable dome form show their grand appearance and indicate wide application and favorable future.
The current research within the country is mainly focused on statics and geometric stability of cable domes, and relatively little attention has been paid to the property of dynamics. The cable dome is a typical long period flexible structure. Because of the characteristic of long span, light self-weight and obvious geometric nonlinear behaviour, the dynamic property of the cable dome is very complex.
In this study, the dynamic property of the cable dome, a typical flexible structure system, has been analysed in detail through two 50-meter span dome models. The aim of this analysis mostly focuses on the factors influencing the natural frequencies and modes. Useful conclusions can be drawn from this paper as following. First, as a typical flexible self-balanced structure system, the cable dome has very small natural frequencies, which are closely distributed and varying little with the different parameters. Because natural frequencies are determined by the geometrical configuration and mass of the structural system, the property of members and the ratio of height to span have a remarkable influence on frequency. Keeping the other conditions fixed, natural frequencies diminish with the cross-section area of struts increasing and increase with the area of cable sections. But the ratio of height to span has a dual influence on them. Thirdly, enlarging the initial pre-stress can increase the structural natural frequency, but this effect only influences the low order frequencies obviously. Generally speaking, as to natural frequencies the effect of initial pre-stress is very small. The selection of rational initial pre-stress is very important for such tensegrity system. The result of calculation has revealed that the stiffness of the Levy cable dome is more rigid than the Geiger cable dome, which distributes evenly and fits well in every direction. Because of this cause, the first order frequency of the Geiger cable dome is less than the Levy cable dome. And the mode shape of the former shows torsional vibration, while the latter shows horizontal vibration mode as whole.
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