Geometric nonlinear thermo-elastic analysis of thin-walled beams by high-order finite elements

Based on the Carrera Unified Formulation (CUF), geometrical nonlinear finite beam elements for the thermomechanical analysis of thin-walled structures are presented. The thermomechanical problem is described using a decoupled approach, in which a uniform overtemperature is applied to the beam. Notably, full 3D stress and strain tensor components are considered in the proposed approach as complex distorsions and post-buckling regimes are considered. The nonlinear equations are solved through the finite element method and a NewtonRaphson linearisation scheme. Numerical results include the analysis of Z- and C-section thin-walled metallic beams. After verification, comparisons are made between the full nonlinear and the linearised analyses. The impact of the adopted kinematic theory on the description of the beam nonlinear response and post-buckling is investigated. The analyses highlight that the accuracy of the nonlinear response strongly depends on the theory approximation order when torsional and local modes govern the response. In particular, refined higher-order models are required to obtain a coherent prediction of both the linearised critical modes and the post-buckling equilibrium path.