Abstract
An investigation is made of the instability of thin-walled sections. A versatile computer program based on the finite element method of structural analysis is developed which is capable of determining the critical loads and buckling modes of arbitrarily shaped closed or open thin-walled sections under arbitrary loading. The effectiveness and validity of the program is checked against some classical problems and then applied rigorously to the study of the local buckling of box columns and the overall stability, of thin-walled box girders in cantilever. An experimental programme is performed on the buckling of thin-walled plastic box-columns for comparison with the analysis.