Static capacity of collar plate reinforced tubular X-connections subjected to compressive loading: study of geometrical effects and parametric formulation

In the present paper, the effect of joint geometry and collar plate size is investigated on the structural behavior of the strengthened X-joints subjected to compression. In the first step, the developed finite element (FE) model is verified using experimental data of six collar plate strengthened and un-strengthened X-joints conducted in the present authors' previous study. After that, a total of 138 collar plate strengthened and un-strengthened FE models of tubular X-joints was conducted and analysed. Results show that the propagation of the plastic zone in strengthened connections with a big collar plate length is larger than the propagation of the plastic zone in strengthened connections with a small collar plate length. Finally, a theoretical equation is proposed based on the yield volume model to predict the ultimate capacity of X-connections strengthened with collar plates under brace compression.