Non-classical effects in FRP composite tubes

This paper presents a formulation of Generalised Beam Theory (GBT) developed to analyse the influence of non-classical effects on the structural behaviour of FRP composite circular hollow section members. Unlike other existing beam theories, the present GBT formulation incorporates non-classical effects comprising (i) elastic material couplings, (ii) deformation of cross-section contour, (iii) warping deformation and (iv) shear deformation. With the purpose of solving the GBT system of differential equilibrium equations, a finite element formulation is briefly presented. In order to clarify the concepts involved in the formulated GBT and illustrate its application and capabilities, the linear (1st order) behaviour of two composite members exhibiting elastic couplings is analysed and the results obtained are thoroughly discussed and compared with estimates available in the literature. It is shown that accurate solutions can only be achieved if these non-classical effects are incorporated in the analysis.