ON THE ELASTIC STABILITY OF SLEEVE STIFFENED HOLLOW COLUMNS; FOCUSING ON DETERMINATION OF OPTIMAL DESIGN CURVES (TECHNICAL NOTE)

The stability analysis of sleeve stiffened pin-ended slender hollow columns of pipe or box section is performed in the present study. This is accomplished by using energy method, employing three terms in the assumed approximate deflection function. The lengthy and tedious algebraic manipulations involved in solving the relevant eigenvalue problem, necessitates employing the "MATHEMATICA" software. Nevertheless, the final result for the critical load can not be presented in a closed from equation, as it is too long and may occupy several pages. The critical loads are determined for many different box and pipe sizes. A total of 144 design curves are determined and plotted showing the critical load for different lengths and thickness of the stiffening sleeve. The curves show an increasing trend in buckling load-carrying capacity up to 90 percent. Minimizing the material volume of the sleeves, the optimal portions of the design curves are determined. It is also found that sleeve stiffening beyond 70 percent of the length of the column is a waste of material, as it does not significantly contribute to increasing the load carrying capacity. The possibility of local shell buckling is also considered.