POSTCRITICAL BEHAVIOR OF THIN-WALLED COMPOSITE BEAMS

The nonlinear dynamic equations for axially compressed anisotropic thi n-walled beams are discretized by means of Fourier expansion and Galer kin procedure obtaining a set of nonlinear ordinary differential equat ions. Based on these ordinary differential equations the buckling and initial post-buckling behavior is analysed. The formulas for initial p ost-buckling slope and curvature are derived. In the case where the co mpressed force is a harmonic function of time, the frequency range and amplitudes of the parametric resonance (instability) are calculated.