Simplified Second‐Order Elastic‐Plastic Analysis of Frames

Abstract

A simplified nonlinear computer algorithm that calculates the elastic‐plastic response of plane frames including the P‐Delta effects as well as the reduction in the plastic moment capacity due to axial forces is presented. The proposed algorithm consists of a simplified second‐order elastic‐plastic analysis in which the effects of bowing and the incremental part of the stiffness matrix in each member are neglected. The NONLIN algorithm, as it is called in this paper, is particularly useful in the plastic design of steel frames. FORTRAN and BASIC versions of NONLIN are available for use in microcomputers. The validity of the proposed algorithm is checked against available experimental and analytical results.