A STUDY ON THE INSTABILITY PROBLEM FOR 2D-FRAMES

This paper presents large deflection, post-buckling analysis of the tw o-dimensional elastic frame from a dynamic point of view. A co-rotatio nal formulation combined with small deflection beam theory with the in clusion of the effect of axial force is adopted. An increment iterativ e method based on the modified Newton-Raphson method and extrapolation techniques for improving the convergence behaviour combined with a co nstant are length control method is employed for the solution of the n on-linear equilibrium equations before the limit point. A non-linear d ynamic analysis based on the average acceleration of the Newmark algor ithm with a slow rate of load incrementation is carried out to trace t he load-deflection path beyond the limit point. As a result, the snap through problem is overcome without down loading. The efficiency of th e method proposed in this study is demonstrated by typical two-dimensi onal frames which show snap-through behaviour in static analysis with any increment of load after the limit point.