elucidates the various problems associated with attaining stability, and provides the results for practical use by the design engineer. By presenting a simple and visual description of the physical phenomena, the authors show how to determine the critical loads of various structures, such as frames, arches, building structures, trusses and sandwiches. Special emphasis is given to the post-critical behaviour - essential for assessing the safety of structures - and furthermore to the summation theories that make the solution of complicated stability problems relatively simple.