Sleeve connections of cold-formed steel sigma purlins

Cold-formed steel sigma purlins normally possess advantageous structural features such as an enhanced web buckling resistance and a location of shear centre closer to the web. In modern roof construction, typical connections for sigma purlins include butt, continuous and sleeve systems. The sleeve connection is often favoured due to ease of installation and lack of restriction on the length of connected purlins. The inherent characteristic of this type of connection is an important factor affecting the structural behaviour of the entire purlin system. As the rotational stiffness and moment resistance will directly influence the stiffness and ultimate load of the purlin system, the determination of these quantities is therefore imperative for purlin design. This paper reports on an experimental study into the sleeve connection of sigma purlins. A series of laboratory tests were carried out to determine the moment–rotation behaviour as well as the moment resistance of this type of connection. Engineering models were then developed to predict these connection behaviours and results matched the experimental observations well. The experimental results reported in this paper provide a well-documented first-hand data for sleeve connections of cold-formed steel sigma sections in terms of moment resistance, rotational stiffness and typical failure modes. The proposed analytical models provide rational engineering methods that can be used in the design practice. Such design methods are not available in any design codes or specifications.

► Structural characteristics of sleeve connections of sigma purlins.
► Experimental data of moment resistance, rotational stiffness and typical failure modes reported.
► Design models for the M-theta relationship and moment resistance of sleeve connections proposed.
► Sleeve connections exhibit typical features of a semi-rigid joint.