Elastic stability of built-up columns using the spline finite strip method

The aim of the work presented in the paper is to contribute to the elastic stability analysis of axially compressed battened columns composed of U shaped channels. The spline finite strip method is used to model the channels whereby the connecting batten plates are represented by a beam finite element with six degrees of freedom at each node. The beam stiffness matrix had to be modified in order to ensure complete compatibility with the finite strips, which have only four degrees of freedom at their nodal sections. First, the behaviour of long battened columns, which fail by overall buckling, has been examined. The number of batten plates along the columns has been varied and the resulting critical loads compared to the theoretical predictions obtained by the classical theory of Engesser. Then, the behaviour of short columns connected by only three batten plates has been compared with that of struts composed of only the channels. The results show that the batten plates have an influence on the critical loads and the failure modes of the short built-up columns.