Research on the Torsional Capacity of Polygonal Tubular Main Beams for Flat Single-Axis Solar Trackers

The flat single-axis photovoltaic （PV） tracker is a wind-sensitive structure， in which wind loads induce significant torsional moments in the main tubular beam. Current design codes， such as the AISC code， provide guidelines only for rectangular and circular tubular sections. However， they lack explicit calculation methods for polygonal tubular sections and offer no specific provisions for torsion design in steel structures （e.g.， in Chinese codes）. This study analyzed and compared the torsional capacity of thin-walled closed sections using shell buckling theory， standardized design principles， and numerical simulation. The results indicated that provided the width-to-thickness ratio requirements were satisfied， the theoretical predictions showed good agreement with the simulation results， based on which corresponding torsional capacity calculation formula was proposed. Accordingly， the cross-sectional optimization design strategies tailored to the characteristics of the flat single-axis tracker’s main tubular beam were explored.