A thesis submitted in partial fulfillment of the requirements for the degree of Master of Engineering, School of Civil Engineering

Thesis (M.Eng.) - Asian Institute of Technology, 2003

In this study, a two-node finite element for geometrically nonlinear analysis of thin-walled structures is developed by using quasi-conforming element technique. Simple and economical procedures for large-deformation elasto-plastic analysis of frames, whose members can be characterized as XBEAM2Q beams, are presented. The element is degenerated from the three-dimensional field equations, using certain assumptions justified for thin-walled open sections, so that the effect of warping restrained conditions can be fully accounted. The quasi-conforming element technique is employed to derive the tangent stiffness matrix, subjected only to conservative (deformation-independent) systems. The formulation is derived using co-rotational approach for three-dimensional beams and the nonlinear analysis is referred to the updated Lagrangian configuration. Von Mises yield criterion has been used to account for material nonlinearity. It is shown that the formulation yield explicit form of stiffness matrix and nodal point force vectors. Several examples are given to illustrate the relative economy and efficiency of the method in solving large-deformation problems. The method is of considerable utility in analyzing large plane and space frames.