Design equation for overlap tubular K-joints under axial loading

Using a previously presented finite-element study of axially loaded overlap tubular K-joints as a platform, this paper presents further work that aimed at extending and enhancing the strength estimation equation already presented. The current work includes extending the a (brace angle) validity range to 30 degrees less than or equal to theta less than or equal to 60 degrees; investigating the effects of the yield stress/ultimate tensile strength ratio and the brace/chord yield stress ratio; exploring the influence of loading reversal; and quantifying the reduction in strength caused by the absence of the hidden weld. The end result of these studies is a new, extended capacity equation. The accuracy of the proposed equation to predict the axial capacity of test joints was established by assessing it using an experimental database. The applicability of the proposed equation for design practice was further ascertained by investigating strength sensitivities to material curve variations, different chord end support conditions, and joints with unequal brace inclinations. The proposed design equation is found to be both accurate and conservative and is therefore recommended to be used in practice.