ON THE EFFECTIVE STIFFNESS OF SLENDER STEEL SECTIONS FOR DEFLECTION CALCULATIONS

The paper is concerned with the reduced stiffness of slender (Class 4) cross-sections due to the increased in-plane deformability of buckled panels. The main purpose is to underline that the effective width for stiffness is not the same as that for strength on principle, and to g ive a theoretical evaluation of this fact. The analysis is carried out using an analytical large deflection solution based on reasonable ass umptions with account taken of the initial imperfections, The results shown that the theoretical effective width for stiffness is always lar ger than that for strength, and therefore, as a rule, a separate desig n equation should be provided. In this context, a new, Winter-type exp ression is proposed On this basis, an extension of the effective-width concept for stiffness is suggested. The conclusions drawn are of prac tical interest especially in the case of design limited by deflections . Copyright (C) 1996 Elsevier Science Ltd.