An Approximation of Yield Surface for Doubly Symmetrical Sections of Steel Structures

Abstract

The paper presents a new method to generate yield surfaces for the doubly symmetrical sections including thin-walled pipe, thin-walled box, and wide-flange I-shape under axial force combined with biaxial bending moments in nonlinear analysis of the steel frame. The yield surfaces are described by twenty parameters and all of them can be determined automatically by the computer program using the power and polynomial regressions of the interaction curves. The cutting plan algorithm (CPA) is adopted for internal force update to satisfy yield conditions in a plastic hinge. A computer code was designed to implement the proposed model and carry out nonlinear analyses on steel frames. Multiple computational examples have been executed to verify the proposed model's accuracy and efficiency, involving a comparison of results predicted by the proposed method with those obtained from alternative methods.