Influence of the side wall of RHS columns on the behavior of welded connections with I-beam sections

The assessment of moment resistance, stiffness, and failure modes of welded connections between I-beams and rectangular hollow section (RHS) columns is crucial to ensure the structural integrity and performance of steel structures. However, existing design codes and normative equations for estimating the moment resistance do not consider all geometric parameters that influence the behavior of the connections, such as the contribution of the side wall of the column. In this context, the present study aims to assess the influence of the selected parameter on the structural behavior and moment resistance of uniplanar T-type welded connections. To achieve this, an investigation was developed through finite element (FE) simulations, using a numerical model validated by experimental results. The analysis considered variations in the thickness (t0) and height (h0) of the hollow section side wall, as well as the thickness (t1), width (b1), and height (h1) of the beam, resulting in a total of 315 models. Furthermore, the predominant failure mode was identified, and the numerical results were compared with the analytical formulations presented in the design codes. The two failure modes observed were column frontal face plastification (β ≤ 0.85) and column side wall yielding (β = 1.0). Design codes such as EN 1993-1-8 and ISO 14346:2013 provide equations for determining the resistance capacity of connections when β ≤ 0.85 and β = 1.0, and suggest interpolation for results when 0.85 <β < 1.0. Comparing the analytical formulations with the numerical results, it was observed that the design equations tend to present a conservative estimate for the moment resistance of the connections. The results indicate that higher values of and ratios between the beam width and column width (β=b1/b0) lead to a greater influence of the column side wall on the connection behavior, resulting in higher moment resistance. Based on these observations, an equation was proposed that takes into account the influence of the side walls if the column on the moment resistance of the connection, particularly for higher values of β, leading to more consistent results.