Slenderness limits for filled circular steel tubes

Abstract

This paper presents a theoretical study of the local and post-local buckling of thin-walled circular steel tubes that contain a rigid infill, with the motivation being an investigation of the cross-sectional behaviour of concrete-filled steel tubes used as columns in composite construction. An analysis is undertaken to determine a closed form solution for the elastic buckling of a circular tube with a rigid infill, and a model of the post-local buckling response is proposed. This generic approach is calibrated against test data, and a cross-section slenderness limit is proposed that delineates between a fully effective cross-section and a slender cross-section. A simple prescriptive equation is proposed for the buckling strength of the steel cross-section that is consistent with many design codes, and illustrates that the presence of an infill may enhance the cross-sectional strength, not only by the added strength of the infill itself, but by delaying the buckling of the steel tube. © 2002 Published by Elsevier Science Ltd.