Experimental study of the axial compressive strength of CHS T-joints reinforced with external stiffening rings

• A new reinforcement method that uses an external stiffening ring welded to a circular hollow section (CHS) T-joint is investigated.
• An axial compressive experiment involving six T-joints (three unreinforced and three reinforced) is conducted to verify the reinforcement effect.
• The failure modes of the unreinforced and reinforced T-joins are compared.
• The external stiffening ring significantly increases the joint strength, and the ultimate capacity of the joint can be calculated according to the plastic bending of the crown section.

This paper studies circular hollow section (CHS) T-joints by conducting experiments on the comparative axial compressive strength of unreinforced and reinforced T-joints. Three pairs of unreinforced and reinforced T-joints, a total of six specimens with the ratio of brace to chord diameter equal to 0.26, 0.51, and 0.74 respectively, were tested to determine their compressive load capacity. The specimen parameters, experimental setup, and test results are presented. The failure modes of the unreinforced and reinforced T-joints were compared. The unreinforced joints failed due to chord plastification, while the reinforced joints failed due to chord bending. The experiment indicated that the external stiffening ring significantly increased the axial compressive strength of the T-joints. Every reinforced joint behaved like a beam when loaded by concentrated force at the brace end; the strength of the reinforced joint can be predicted by calculating the plastic bending moment at the crown section.