Design Method for Axially Compressed Members Reinforced with Sleeves

Abstract This study presents a comprehensive investigation into a novel prefabricated sleeved retrofit technique for enhancing the global stability of steel compression members in grid structures that are interconnected through joints, such as space grids, latticed shells, and trusses. The research systematically examines the effects of key parameters, including material constitutive laws, yield strengths, outer sleeve geometries (diameter, wall thickness, and moment of inertia), and initial geometric imperfections, on the buckling behavior of reinforced members. A simplified yet accurate finite element modeling strategy, validated against experimental tests, was employed for parametric analysis. The results demonstrate that the retrofit significantly improves the buckling factor, with enhancement governed primarily by the outer sleeve’s moment of inertia rather than its material strength. Notably, the yield strength of the inner tube has a negligible effect, while the amplitude of initial imperfections significantly influences the postretrofit performance. Based on these findings, a modified column curve is proposed. For welded sleeves, the curve aligns closely with the standard column curve a, enabling straightforward design. Further, a practical and efficient design methodology is established, which determines the required sleeve dimensions by first calculating the target moment of inertia based on load demands, thereby streamlining the engineering design process. This work provides theoretical insight and a practical design framework for the application of this efficient retrofit technique.