80 KAZI"CZY CRITICAL SURVEY OF THE THEORY OF PLASTICITY*

idea that the determination of the true load capacity of hyperstatic structures had to reckon "with the residual steel strains. This true load capacity exceeding that according to the theory of elasticity, the residual strain might be reckoned with in the practical design of structures. In the meantime this problem had been discussed, expounded from several aspects, and experimentally tested. Let us have now a critical survey of the domain as a whole. There are different denominations for the new design method. Theory of plasticity means a design method taking also residual deformations into consid-eration, as against the theory of elasticity relying on elastic deformations alone. It is also called ultimate load method (theory of plastic equilibrium), a term other than unambiguous, namely some authors e.g. STUSSI mean by ulti-mate load the maximum load carried by the structure,,,,-hile others such as F. BLEICH, lVlAIER-LEIBNITZ and the Author himself in an earlier publication, have meant the maximum load allowed in practice. The approach to this pro-blem depends on certain fundamental principles. What is the goal of design