Harmonic coupled finite strip method applied on buckling-mode interaction analysis of composite thin-walled wide-flange columns

This paper presents an investigation of bifurcation buckling, buckling-mode interaction and post-buckling equilibrium of composite thin-walled wide-flange columns. The non-linear harmonic coupled finite strip method is used. As far as linear analysis is concerned, it takes advantage of the orthogonality properties of harmonic functions in the stiffness matrices formulation. However, in the case of geometric non-linear analysis all harmonics are coupled. In thin-walled sections the finite strips include the local and global buckling modes. When critical local and global stresses are close, new bifurcations appear due to buckling-mode interaction and failure stresses may be lower than both predictions. In this work, the existence of buckling-mode interaction is verified in H-section columns made of fiber reinforced plastic using the viscoelastic rheological–dynamical modulus and non-linear harmonic coupled finite strip method. Numerical examples showing the theoretical considerations are presented and agree with the experimental data.