ABSTRACT
The lowest natural frequencies of the unloaded column are ω0v =ω0w =ω0γ = 3.5161. Figure 2 illustrates the influence of the static axial load on the frequencyamplitude relation. The unloaded column exhibits a small degree of geometric nonlinearity with hardening behavior. As the axial load increases, the degree of nonlinearity decreases due to increasing inertial nonlinearity and, at a certain load level, the curve starts to bend to left. For high load levels, it shows a strong softening behavior.
