AN APPROXIMATE METHOD FOR CALCULATING CRITICAL STRENGTH OF THIN-WALLED STEEL FRAMES

Abstract

This paper proposes an approximate method, so-called modified P-δ method, for calculating the ultimate strength of thin-walled steel frames with box cross-section by the first order elastic analysis. The decrease of ultimate strength of frames due to the initial imperfection and P-δ effects of columns is estimated by assuming the initial rotational angle of columns in this method. The validity of modified P-δ method is checked through the parametric studies on the critical strength of several types of frames with variable cross-sections by the Finite Element Method based on the elasto-plastic finite displacement theory.