Strength of internally ring-stiffened tubular DT-joints subjected to brace axial loading

•Failure mechanism of internally ring-stiffened DT-joints was identified.•Theoretical models and equations for stiffener strength prediction were proposed.•A chord stress function was proposed to consider the effect of chord axial stress.•A strength equation for internally ring-stiffened DT-joints was proposed.

This paper presents the results of numerical and theoretical studies to obtain static strength equations for internally ring-stiffened circular hollow section (CHS) tubular DT-joints. An extensive study of 1264 unstiffened and ring-stiffened DT-joints subjected to brace axial compression or tension was conducted. The numerical analysis shows that failure mechanism of crown- and saddle-stiffened DT-joints under brace axial loading is formation of plastic hinges in the stiffener and chord wall yielding near the brace-chord intersection. Based on the identified failure mechanism, theoretical models and corresponding equations for predicting the stiffener strength in crown- and saddle-stiffened DT-joints subjected to brace axial compression or tension were proposed. The accuracy of the proposed stiffener strength equations was evaluated by an error analysis. A chord stress function was proposed to consider chord axial stress effect on the stiffened DT-joint strength. In conjunction with existing unstiffened DT-joint strength formulae and considering chord axial stress effect, a strength equation for crown- and saddle-stiffened DT-joints subjected to brace axial loading was proposed.