Stability of Strain-Hardening Tubular Columns

The stability of elastic-linear strain-hardening tubular cantilever columns is analyzed by numerical integration of the nonlinear differential equation with the aid of parametric equations expressing the moment-thrust-curvature relationships. Equilibrium curves for cantilever columns subjected to arbitrary end loads are first constructed. The envelopes of these equilibrium curves are shown to be the interaction curves. Approximate equations for the latter are derived and used to analyze simply supported columns subjected to arbitrary end loads. Column curves are presented for aluminum columns of Alloy 6061-T6. The results obtained from this analysis are discussed in the light of the corresponding allowable loads given by suggested specifications for such structures.