The latest edition of this book a considerable amount of new material has been added. Throughout the text the latest references. have been inserted as well as new problems for solution and additional figures. The major changes in text material occur in the chapters on torsion plastic deformation and mechanical properties of materials: Each of these topics is important in the design of thinwalled structures such as the structural components of air- planes. In the chapter on plastic deformation the fundamental principles of limit design are discussed. Several examples of the .application of the method to structural analysis are presented. Major additions were made to the chapter on mechanical properties of materials so that this single chapter now contains over 160 pages.