Fatigue analysis of FAST cable-net structure under long-term active shape-changing work

Structural fatigue property of the adaptive cable-mesh reflector of Five-hundred-meter Aperture Spherical radio Telescope (FAST) was analyzed. According to the active shape-changing working pattern (longtime sky survey and independent random tracing observation) of FAST, the required times of continuously running all year daily in design reference period of 30 years was computed, and the corresponding random fatigue stresses of FAST cable-net structure were analyzed, then the typical fatigue stress piece was put forward based on simple sampling and was decomposed by real-time rain-flow counting algorithms. Subsequently, the fatigue lives of each cable were computed by Miner linear accumulative damage criterion, which was based on the S-N curve of Chinese steel strand (1860 N/mm²) and Smith fatigue limited diagram for equivalent life. Taking the minimum fatigue life of all cables as the fatigue life of the overall structure, the life with a guaranteeing probability of 99.9% was analyzed statistically after many stochastic simulations of the typical fatigue stress piece, and a suitable service life factor which is 2.0 was applied in order to take into account the variability of fatigue life. The results show that the fatigue life of FAST cable-net structure can meet the safety requirement in design reference period, and the structural fatigue dangerous region is located in the central part of the cable-net.