Tests of X- and K-Joints in CHS Stainless Steel Tubes

This paper describes a test program on welded stainless steel X- and K-joints fabricated from circular hollow section (CHS) brace members and chords. The X-joints were tested in compression and tension using three different ratios of brace diameter to chord diameter. The K-joints were tested using three different ratios of brace diameter to chord diameter and three different angles between chord and brace members. A total of 15 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 structure and replacing the yield stress in these recommendations by a proof stress. It is shown that both the 0.2 and 0.5% proof stresses, as determined from the finished tube, can be used to determine the ultimate strength using the CIDECT strength rules. For K-joints, the serviceability limit state corresponding to joint deformations of 1% of the chord diameter will not be exceeded if the CIDECT strength rules are adopted. However, for less than full width X-joints, the deformations are likely to reach about 1.7 and 1.9% of the chord diameter if the design strength is based on the 0.2 and 0.5% proof stresses, respectively.