Performance of CFS trusses self-drilling screws connections under extreme loads

Cold-Formed Steel (CFS) roof trusses often use self-drilling screws for efficient on-site assembly. Premature screw connection failures can significantly compromise truss integrity under static and dynamic loads. Connection failures included individual screw failures under shear, bearing damage of connected parts at screw interfaces, and screw/material separation. Additionally, screw tilting impacts behavior significantly. In this paper, an experimental study of sixteen self-drilling screwed connections used in typical CFS roof trusses was performed. Connections varied in screws count from 2 to 12, sheet thickness of 0.89 mm, 1.17 mm, and 1.45 mm, and the sheet order. Increasing the number of screws to six improved the peak capacity and stiffness of the connection by 60 % and 255 %, respectively. Moreover, additional screws beyond six had minimal effect on capacity and stiffness and reduced ductility. Reversing the sheet thickness decreased initial stiffness by 30 % and peak load by 15 %, but increased energy absorption. Additionally, energy absorption of the connections increased by 45 % when increasing the number of screws from two to six screws.