An incremental total Lagrangian formulation for general anisotropic shell-type structures
Based on the principle of virtual displacements, the incremental equations of motion of a continuous medium are formulated by using the total Lagrangian description. After linearization of the incremental equations of motion, the displacement finite element model is obtained, which is solved iteratively. From this displacement finite element model, four different elements, i.e. degenerated shell element, degenerated curved beam element, 3-D continuum element and solid-shell transition element, are developed for the geometric nonlinear analysis of general shell-type structures, anisotropic as well as isotropic. Compatibility and completeness requirements are stressed in modelling the general shell-type structures in order to assure the convergence of the finite-element analysis. For the transient analysis Newmark scheme is adopted for time discretization. An iterative solution procedure, either Newton-Raphson method or modified Riks/Wempner method, is employed to trace the nonlinear equilibrium path. The latter is also used to perform post-buckling analysis. A variety of numerical examples are presented to demonstrate the validity and efficiency of various elements separately and in combination. The effects of boundary conditions, lamination scheme, transverse shear deformations and geometric nonlinearity on static and transient responses are also investigated. Many of the numerical results of general shell-type structures presented here could serve as references for future investigations.