INTERACTIVE BUCKLING ANALYSIS OF FIBER-REINFORCED THIN-WALLED COLUMNS

An analytical approximate model, leading to a closed form solution, is presented to account for buckling mode interaction in composite I sec tion columns. Three buckling modes are considered in the analysis: a g lobal mode (Euler mode about the weak axis); a primary local mode (rot ation of the flanges and bending of the web); and a secondary local mo de (bending of the flanges), which are modeled using analytical functi ons and four degrees of freedom. The fundamental state is shown to be linear and the three critical states for the isolated modes are found to be stable symmetric bifurcations. Mode interaction analysis in term of the amplitudes of first order fields is carried out, for the first time, for prismatic sections of composite material. The tertiary (cou pled) path involves coupling between the two local modes and it descri bes the sensitivity to imperfections of the buckling behavior of the c omposite column. A salient feature of the model presented is the close d form of the resulting solution, which enables the designer to easily perform parametric studies. Also, this is the first buckling mode int eraction study for thin-walled composite columns. Numerical examples a re presented to validate the results and to show the influence of the geometry and properties of the composite on the interaction phenomenon .