Experiments and finite element modelling of screw pattern of self-drilling screw connections for high strength cold-formed steel

Abstract

Cold-formed steel (CFS) self-drilling screw connections are popular due to rapid fastening and ease of installation. However, limited research is available in the literature to investigate the effect of screw patterns on the connection, where the individual screws can undergo different failure modes including bearing, tilting, pull-out and shear failure, particularly for Grade 550 CFS plates. This issue is addressed herein through a combination of experimental and numerical tests. In total, 25 new experimental tests are reported that investigate the effect of screw patterns, number of screws, and screw spacing on the connection strength; in the tests, 12 and 14 gauge screws are considered. A nonlinear explicit dynamic finite element (FE) model was then developed which includes a fracture criterion for the steel sheets. The FE model was validated against the experimental test results and showed good agreement in terms of connection strength and failure modes, including bearing, tilting, pull-out and shear failure.