Non-linear behaviour of thin-walled open section composite beams in lateral stability

An analytical study along with a numerical investigation is conducted to determine the lateral buckling strength of thin-walled open-section I shape composite beams. Based on Vlasov-type linear hypothesis beam stiffness coefficients, which account for a cross section geometry and material anisotropy of the section, are obtained. In this study the axial and bending coupling terms ( A(13), A(23), D-13, D-23) and the coupling between bending and twisting terms (B-ij), which refer to anisotropic structural behaviour of the beam are also considered. In order to drive a better estimate of load capacity of composite beams, the transverse shear strain effect on the lateral buckling is included in calculations. To verify the analytical manipulations, the finite element software, ANSYS, is used to present a numerical solution for prediction the buckling load As a parametric study, different boundary conditions, laminate sequences, fiber orientations are tested in order to find their sensitivity and optimum values to improve the lateral buckling strength of open-section laminated beams. Uniformly distributed, transverse concentrated and end moment loads, being popular loading systems are applied. The results reveal the non-linearity behaviour of general orthotropic beams in flexural torsion instability mode.