Tests of X- and K-joints in SHS stainless steel tubes

Abstract

This paper describes a test program on welded stainless steel X- and K-joints fabricated from square hollow section (SHS) brace members and chords. The X-joints were tested in compression and tension using different ratios of brace width to chord width. The K-joints were tested by varying the ratio of brace width to chord width, the angle between chord and brace members, and the preload applied to the chord. A total of 23 tests were performed. Design rules are proposed for X- and K-joints by adopting the rules of the Comité International pour le Developpement et l'Etude de la Construction Tubulaire (CIDECT) recommendations for carbon steel tubular structures and replacing the yield stress in these recommendations by a proof stress. It is shown that the 0.2% proof stress, as determined from the finished tube, can be used to determine the ultimate strength using the CIDECT design rules and that the serviceability limit state corresponding to joint deformations of 1% of the chord width will not be reached if the CIDECT strength rules are adopted. It is also shown that the CIDECT strength rules produce unconservative design strengths when using the 0.5% proof stress in cases of high compressive forces in the chord. However, the serviceability limit state will generally not be reached if the 0.5% proof stress is used.