CHS X-joints strengthened by external stiffeners under brace axial tension

This paper presents an experimental and numerical investigation of the use of external stiffeners to reinforce circular hollow section (CHS) X-joints under brace axial tension. Six full-scale specimens with different brace to chord diameter ratios (β) of 0.25, 0.50, and 0.73 are tested, including three unreinforced X-joints and three reinforced X-joints. The experimental setup and detailed parameters are presented and results including failure modes, load-displacement curves, and ultimate capacity are compared. The experiment results show that the reinforced external stiffeners clearly increase the mechanical performance of joints in tension, supported by the improved ultimate strength and initial stiffness in comparison to the unreinforced specimens. Furthermore, the enhancement of ultimate strength increases along with the increase of brace to chord diameter ratio (β). Finite element (FE) modeling using SHELL181 element is also established and precisely describes the static behavior of the X-joints under brace tension with and without external stiffeners.