Strengthening Steel CHS X-Joints Subject to Compression by Outer Ring stiffeners

This study investigates the behavior of strengthened CHS X-joints by adding symmetrically two distant outer ring stiffeners to the chord on each side of the brace outside the brace-chord welding zone. Compared to previously utilized strengthening techniques, this new technique has the advantage of being external, thus can be used for strengthening of already erected joints. Also, it avoids welding to previously affected zones resulting from welding brace to chord; and utilizing minimum radius to ring stiffener keeping the aesthetic appearance of the structure unchanged. In this research, a parametric study is carried out to evaluate the impact of different geometric parameters for the stiffeners such as their diameters, thicknesses and spacing on the efficiency of such strengthening technique. The results provided guidelines for proper detailing of these stiffeners to significantly increase the joints strength up to double the strength of the original unstiffened joint.