ABSTRACT
Structural design is a process by which a structure required to perform a given function is proportioned to satisfy certain performance criteria in a safe and economic way. A designer's duty is to proportion the structure in such a way that the risk of its failing is acceptably small. The basic premise of the elastic design method is that the attainment of the yield stress at any point in a structure marks the end of acceptable behaviour, the argument being that any further increase in stress will lead to permanent strain in the material. A plastic design method was evolved which, taking account of the plastic extension of steel, was able to predict the load which would cause the structure to collapse. Element and component stability problems may arise at points where there is partial or complete compressive load on the cross-section, conditions which must occur somewhere in all practical structures.
