Non-linear Geometrical Analysis of Space Trusses with Member-Length Imperfection Developing Mixed Finite Element Method

Since space trusses commonly have a significant number of members, several elements of trusses inevitably have imperfections, mainly in the form of length imperfections. In this article, the author proposed the mixed finite element method for non-linear geometrical analysis of space trusses. The mixed FEM is developed to deal with the length imperfections in the tangential matrix of stiffness and the non-linear equation of equilibrium of the system. The solutions of non-linear equations of equilibrium are found by applying an incremental-iterative solution procedure according to the arc-length method. The proposed method allows dealing with the length imperfections in an elastic analysis of the space trusses with large deflections. A code list written in programming software predicts the post-buckling behaviour of space trusses with length imperfections. The numerical results of this research show that when the value of the length imperfection approaches zero, the results converge with the results obtained in the various studies for standard trusses. These obtained results verify the correctness of the proposed method.