Performance optimization analysis of FAST reflector supported cable-net based on initial baseline state
Luo Bin1, 2, Guo Zhengxing1, 2, Wang Kai3, Xiao Quandong1, 2
1. The Key Laboratory of C & PC Structures of the Ministry of Education, Southeast University, Nanjing 210096, China; 2. National Prestress Engineering Research Center, Southeast University, Nanjing 210096, China; 3. Architects & Engineers Co., Ltd., Southeast University, Nanjing 210018, China
Abstract：FAST (Five-hundred-meter-Aperture Spherical Telescope) reflector supported cable-net structure consists of geodesic surface cable-nets and adjust cables, which are high-strength prestress strand. Active deflection is the most prominent feature of the cable-net structure. As the cable-net structure is shape controlled, the standard spherical baseline state optimization analysis method is proposed with the use of allowable stress method. At first, the initial tension value of adjust cables and stress limit of surface cables are determined by the basic requirements of active deflection work and certain amplitude strain change. Through force-finding analysis, the initial tension value of surface cables are found, surface cable sectional specifications are determined with the principle that initial stress is close to the upper limit. Effect analysis of several key factors on performance of the cable-net structure are conducted. To avoid low tension value of adjust cables at work state, the initial tension value of cables can only be increased by maintaining surface cable stress level and increasing the surface cable sectional specification under certain elastic modulus and allowable stress. Sliding bearing and low stiffness will be appropriate for circumferential steel truss, which may be partially installed along the radial direction. And also, the edge adjust cable will not be involved in active deflection after tension. The allowable stress and initial stress upper limit will be improved since cable safety coefficient reduced from 2.5 to 2.0, which can also reduce material amount and improve the internal force. In addition, through the comparison of mechanical properties of carbon fiber cable and steel cable, carbon fiber cable with high strength, low elastic modulus, light weight and fatigue resistance is suitable for FAST cable-net structure.
