Geometry nonlinear analysis of composite thin walled beams

A new geometry nonlinear finite element model for composite thin walled beams has been developed based on the complex deformation characteristic of the composite thin walled beams. Supposed the strain quadratic varies along the thin-walled, introducing the complex cross-section of beam was simulated by 9-node plane element and the out-of-plane warping displacement was simulated by 27-node solid element. Based on the Hamilton principle, nonlinear finite element theory and the Total Lagrange formulation, the geometry stiffness matrix was formed. The analytical model is proved correct through several examples. The model can be used in analysis of thin-walled composite beams, the warping deformation has evidently affected on composite thin walled beams, compared with related literatures numerical results, the advantage of this model has been showed.