Research on the load-bearing capacity of welded aluminum K-joints

This study addresses the limited research on the load-bearing capacity of welded aluminum joints, specifically focusing on square hollow-section (SHS) K-joints. Existing literature has primarily examined welded steel joints and the effects of welding on aluminum alloys without establishing clear design rules for these specific connections. This research develops a numerical model to assess the load-bearing capacity of aluminum SHS K-joints, accounting for peculiarities such as the heat-affected zone (HAZ). Experimental investigations were conducted on nine SHS K-joints integrated into three lattice girders. These tests examined the failure mechanisms and characterized the HAZ using micro-hardness testing to determine yield strength variations across the fusion zone and base material. A numerical model was then developed and validated using experimental results, achieving a difference of less than 8% between the numerical and experimental findings. This model employed the finite element method (FEM) using ANSYS software and considered a refined HAZ model with two subzones, HAZ 1 and HAZ 2, based on micro-hardness testing. Parametric analysis highlighted the influence of the brace-to-chord width ratio (beta) and the double thickness of chord wall to chord width (gamma) on joint performance. An increasing beta ratio was associated with a higher load-bearing capacity, while the impact of the gamma ratio was less definitive. Comparison with theoretical models from EN 1993-1-8 and prEN 1999-1-1 indicated that the existing expressions are conservative and do not fully capture the behavior of aluminum SHS K-joints. This study proposes a less conservative numerical approach that offers more realistic predictions.