Effect of the actual distribution of applied stresses on global buckling of isotropic and transversely isotropic thin-walled members: Numerical examples

Thin-walled members made of fiber-reinforced polymer (FRP) composites are increasingly being used for structural applications, due to the advantageous material properties such as low weight, high tensile strength and insensitivity to corrosion. When manufactured by “traditional” pultrusion, these members display a transversely isotropic constitutive behavior, with plane of isotropy perpendicular to the fiber direction. Previous research showed that, considering a thin-walled member subjected to two arbitrary distributions of applied stresses on the extreme faces, the state of stress and the global buckling load (moment) of the member may be influenced by the actual distribution of the applied pressures, to an extent depending on the values of the elastic constants. The reduction in buckling load (moment) due to this effect was shown to be possibly not negligible for transversely isotropic material behavior, and particularly for low ratios of transverse to longitudinal elastic constants. In order to evaluate how significant this weakening effect can be for design purposes, this work aims at quantifying it as a function of various influential parameters. The influence of symmetry properties of the cross-section on results is also studied. In particular, the I-section and the semicircular sections are taken as examples of a doubly symmetric and a singly-symmetric open cross-section, respectively.