The behavior of cold-formed steel and Belian hardwood self-tapping screw connections

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Cold-Formed Steel Research Consortium (CFSRC) Colloquium
Cold-formed steel has been widely used to retrofit and restore buildings, especially timber buildings. This is because the material is readily available, flexible, and lightweight. However, limited research is available with little assessment concerning cold-formed steel and hardwood connection performance. This paper experimentally studies the behavior of connections composed of self-tapping screws, cold-formed steel, and Belian hardwood. Five connection configurations were investigated, where the ultimate load-carrying capacity of the connection was determined through a sequence of shear and tension tests. The results showed that the connection failed by screw withdrawal under tension load. However, when loaded in shear, the failure mode of the connection changed from screw failure when the screw head was at the Belian side to screw rotation when the screw head was at the cold-formed steel side. The performance of current design guidance in Eurocode 5 was assessed by comparing the strengths obtained from the experiments. The comparison results showed that Eurocode 5 is conservative in predicting the performance of self-tapping screw connection composed of cold-formed steel and Belian hardwood in tension. However, it was overly conservative in predicting the shear strength of the connection as the design strengths are overestimated by around 60%.