BUCKLING OF BUILT-UP COLUMNS WITH OR WITHOUT STAY PLATES

A method of analysis for built-up columns is presented. The method is an extension of the classical Engesser method for columns and the Timoshenko shear-beam theory for beams. The two column chords are treated as beams connected by a shear panel simulating the web. The governing differential equation changes from a fourth- to a sixth-order equation with a corresponding increase in the number of boundary conditions. It then becomes possible to include the effect of stay plates on the buckling load in a rational manner. It is found that the stay plates have a very significant effect on the buckling load. It is also found that the buckling load depends not only on the bending and shear stiffness of the column but also on the relative value of the chords' bending stiffness to the overall column bending stiffness. The solution for a simply supported column is given. The classical Engesser solution is always conservative. © ASCE.