How to determine a value of the bifurcation shortening of real thin-walled laminated columns subjected to uniform compression?

Abstract In the present paper, a methodology for determination of a value of the bifurcation shortening and the corresponding bifurcation load of the real thin-walled laminated column under compression with initial imperfections, using an axial shortening versus squared deflection amplitude plot, is presented. A plate model of the column has been assumed. It has been shown that the post-buckling state is described with a linear relationship on this plot, whereas a value of the bifurcation shortening corresponds to a free term of the straight line approximating the post-buckling state on the plot and is proportional to the bifurcation load. Detailed calculations have been conducted for short composite angle columns under uniform compression. The eigenvalue problem and the non-linear post-buckling problem have been solved with the semi-analytical method (SAM) based on Byskov-Hutchinson’s method and the finite element method (FEM). The bifurcation shortening and the corresponding bifurcation load have been determined. An effect of the imperfection amplitude on the post-buckling behaviour of laminated thin-walled angle columns has been analysed. General configurations of laminate plies have been selected. All columns have been simply supported at both ends. A very good agreement between the results attained with both the methods for solving the non-linear problem has been obtained.