Experimental and Analytical Study of High-Strength Steel RHS X-Joints under Axial Compression

AbstractThe use of high-strength steels for tubular structures has been forbidden or permitted with some joint-strength reduction in most representative international standards. Six rectangular hollow section (RHS) X-joint specimens were tested under axial compression to investigate inelastic joint behavior. The key test parameters included brace-to-chord width ratio and grade of steels. All high-strength steel specimens exhibited sufficient strength compared with current European standards’ strength criteria; their strengths were even higher than the standard’s prescribed unreduced nominal strength. Significantly different postyielding behavior was observed depending upon the brace-to-chord width ratio and the grade of steels. It was also observed that the formulation of sidewall buckling strength in the current European standard tends to predict overly conservative results and requires further examination. A new design formula for RHS X-joints subjected to sidewall buckling was proposed in this paper based on a more realistic buckling shape. When the normalized plate slenderness ratio newly defined in this study is used in conjunction with the column curve c of the European standard, both accuracy and consistency of strength predictions were significantly improved compared with those of the strength formulas currently available.