An improvement of Southwell's method for determining buckling loads

Abstract

If an elastic bar with some initial imperfection is subjected to increasing compressive axial load, the lateral deflection, measured anywhere along its length, increases monotonically; the primary buckling mode becoming more and more dominant in the deflected shape. A classical approximate technique, due to R.V. Southwell, correlates axial load and lateral deflection for determination of the primary buckling load of the bar. However, Southwell's approximation may be inaccurate is the primary mode does not predominate in the deflected shape. The present thesis proposes a technique which employs axial loading, but also transverse loading to insure dominance of the primary mode in the deflected shape. The technique allows experimental determination of the second buckling load, again using appropriate transverse loads to insure dominance of that mode in the deflected shape.