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 (β) of 0.83 and 1.0, were subjected to quasi-static cyclic axial loading. Test results revealed that joints with β = 0.83 primarily failed due to chord face tearing, while those with β = 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 β enhanced axial strength but reduced ductility, deformability, and energy dissipation capacity. Eccentric joints with β = 0.83 showed improved strength, ductility, and energy dissipation compared to traditional joints, whereas eccentric joints with β = 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 β and confirm that tensile strength exceeds compressive strength for all tested joints. Additionally, cyclic compressive strength closely static compressive strength.

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