A GEOMETRIC NONLINEAR FINITE ELEMENT ANALYSIS FOR 3D FRAMED STRUCTURES

For further studies on geometric nonlinearity of framed structures, a finite element method based on beam element is developed. To describe the changing status of incremental displacements and rotations, the curvatures in two directions and torsional angle are considered in the orientation matrix. The influence of higher order nonlinearity term is considered by introducing axial and torsional deformation nonlinear items into the stiffness matrix. A corresponding compter program of 3D beam, NL_Beam3D, using general displacement control method in iterative analysis, is presented. The accuracy of this method is verified by some examples.