Experimental Investigation of Seismic Behavior of Traditional and Eccentric RHS X-Joints Under Brace Axial Cyclic Loading

This study investigates the seismic behavior of traditional and eccentric rectangular hollow section (RHS) X-joints through a comprehensive experimental program. Four X-joint specimens, including two traditional and two eccentric joints with brace-to-chord width ratios (beta) of 0.83 and 1.0, were subjected to quasi-static cyclic axial loading. Test results revealed that joints with beta = 0.83 primarily failed due to chord face tearing, while those with beta = 1.0 exhibited failure modes, including chord face tearing and significant sidewall buckling. Eccentric joints further experienced tearing of brace wall near the intersection. Increasing beta enhanced axial strength but reduced ductility, deformability, and energy dissipation capacity. Eccentric joints with beta = 0.83 showed improved strength, ductility, and energy dissipation compared to traditional joints, whereas eccentric joints with beta = 1.0 displayed superior ductility but comparable strength and energy dissipation. The findings that current design codes underestimate the compressive strength of traditional joints with medium beta and confirm that tensile strength exceeds compressive strength for all tested joints. Additionally, cyclic compressive strength closely static compressive strength.