Screwed connections in built-up cold-formed steel members at ambient and elevated temperatures

Screwed connections are commonly used in fabricating built-up cold-formed steel (CFS) members. However, the knowledge and understanding of their behaviour and design are limited. This research study investigated the shear behaviour and capacity of the screwed connections used in built-up CFS members. It included a series of shear tests of screwed connections between two single channel members as used in built-up back-to-back CFS members, failing by tilting and bearing. Tests were conducted at both ambient and elevated temperatures. Using the results from these tests and available literature, this study has shown that the design equations for the tilting and bearing capacity of screwed connections in the current CFS design standards are reliable for the screwed connections in built-up CFS members at ambient temperature. It has then shown that the same design equations can be used to predict the tilting and bearing capacity of these screwed connections at elevated temperatures if they are used in combination with the proposed reduction factor equations for elevated temperature capacities. Details of this research study, its results and findings are presented in this paper.

Automated summary

This research study investigates the shear behavior and capacity of screwed connections used in built-up cold-formed steel (CFS) members. The results indicate that the design equations for tilting and bearing capacity in current CFS design standards are reliable for screwed connections at ambient temperature. The study also proposes reduction factor equations for elevated temperature capacities.