Investigation into the structural performance of passing-through plate-to-HSS 3D-cut welded joints

Hollow Structural Sections (HSS) are widely used members in the construction sector due to their strength, efficiency, and versatility. However, their complex connections require considerable construction effort and resources. To promote the application of these sections, a new fabrication approach, i.e., Laser Cutting Technology (LCT), has recently facilitated the production of HSS passing-through joints. This research investigates the influence of different welding techniques on the structural performance and failure mechanisms of HSS LCT passing-through welded joints (HSS-LCT-W). Accordingly, a comprehensive material characterization analysis, 35 monotonic tensile tests, and over 40 Finite Element (FE) simulations were conducted on a wide range of HSSLCT- W joints covering different weld configurations and fabrication procedures. The findings highlight that HSS LCT full-strength fillet-welded joints (HSS-LCT-FSFW) represent an efficient solution under monotonic tensile loading. In addition, Circular Hollow Section (CHS) joints outperform Rectangular Hollow Section (RHS) joints due to their arching resistance mechanism against tensile loading. Additional fabrication procedures, such as surface oxidation removal before welding, were found to have minimal influence. In the final section, a surrogate model, incorporating the weld effective length concept, was developed to derive a reliable closed-form capacity equation for RHS LCT fillet-welded joints (RHS-LCT-FW). The proposed design equation is valid within the investigated geometric ranges and should not be extrapolated to thick columns exhibiting fully effective weld lengths. Within the parameter ranges, the results indicate that the optimal design of HSS fillet-welded joints can be achieved by reducing the width of the passing-through plate or increasing the HSS wall thickness.