BUCKLING OF THIN-WALLED LONG STEEL CYLINDERS UNDER BENDING

The present paper investigates structural response and buckling of long unstiffened thin-walled cylindrical steel shells, subjected to bending moments, with particular emphasis on their stability design. The cylinder response is characterized by cross-sectional ovalization, followed by buckling (bifurcation instability), which occurs on the compression side of the cylinder wall. Using a nonlinear finite element technique the bifurcation moment is calculated, the post-buckling response is determined, and imperfection sensitivity with respect to the governing buckling mode is examined. The results show that the buckling moment capacity is affected by cross-sectional ovalization. It is also shown that buckling of bent elastic long cylinders can be described quite accurately through a simple analytical model, which considers the ovalized pre-buckling configuration and results in closed-form expressions. Using this analytical solution, the incorporation of the ovalization effects in the design of thin-walled cylinders under bending is discussed, in the framework of the provisions of the new European Standard EN 1993-1-6.