Elastic critical buckling of steel flanged cruciform columns subject to uniform end moment

Abstract

Columns, vertical elements that support floors and roofs in structures, may be subjected to both bending and axial effects developing from external loads such as dead, live and wind loads. Generally, universal sections are the most common structural steel section used as columns in steel framed buildings. Cruciform columns are becoming more popular and are being used with good effect in high rise buildings, where the loads acting on the columns are large, and a two-way sway frame may be needed. Literature on the behaviour of flanged cruciform column sections is very limited, little has been done to understand the modes of failure and the bending behaviour of flanged cruciform members. The aim of this dissertation is to study the behaviour of a doubly symmetric steel flanged cruciform cross-section when subjected to uniform end moment with no axial loading. Therefore, the focus of this study is on only one extreme end of the beam-column interaction behaviour. This is done by performing finite element analysis, using LUSAS (2019), together with theoretical analysis of the section. The finite element analysis proved to be useful in understanding the local and overall buckling behavioural change of the column with respect to its length. Finite element analysis and theoretical analysis showed that a doubly symmetric flanged cruciform cross-section can buckle. By comparing finite element analysis and theoretical equations, it was possible to obtain an understanding of the different modes of buckling that occur with respect to the length of the column. This dissertation proposes three different equations to find the critical buckling stress according to the length of the column. Therefore, the elastic critical buckling moment of steel flanged cruciform columns can be evaluated.