Post-fire shear strengths of drilling screws and post-fire transitions of failure modes for screwed connections

PurposeThis study was aimed at clarifying the post-fire shear strength of self-drilling screws and the load-bearing capacity of single overlapped screwed connections using steel sheets and self-drilling screws. The self-drilling screws for shear tests were made of high-strength, martensitic-stainless and austenitic stainless-steel bars.Design/methodology/approachShear loading tests were conducted on self-drilling screws to obtain basic information on post-fire shear strength. Tensile tests were conducted on the screwed connections to examine the transition of failure modes depending on the test temperature after experiencing the heating and cooling procedures.FindingsThe post-fire shear strengths and reduction factors of self-drilling screws of each steel grade were quantified. Furthermore, heated temperature-dependent sheet bearing failure, net sheet failure and screw shear failure modes were observed for the screwed connections.Originality/valueThe transition of the failure modes of the screwed connection could be explained using the equations of the post-fire shear strength proposed in this study. The basic experimental data required to evaluate the post-fire shear strength of screws were obtained.