PLASTIC-ZONE AND GEOMETRIC NONLINEARITY ANALYSIS OF PLANAR STEEL FRAMES USING FINITE ELEMENT METHOD

Abstract

This paper presents a method of the large-displacement analysis of planar steel frames taking into account the effects of inelastic material behaviour and beam-column connection flexibility. A finite element is formulated to model the spread of plasticity through the member cross section and along the member length instead of the common assumption on discrete plastic hinge. This element is also capable of including residual stresses, initial imperfections and shift of the neutral axis of the elastic core in yielding. The Foley’s quadrilinear model is used to represent nonlinear moment rotation relationship of semi-rigid connections. The simple Euler incremental-iterative algorithm and the constant work-control technique are applied to solve a set of nonlinear equations. Results of some numerical examples are derived from the computer program written by C++ programing language to verify the validity of proposed method.