This comprehensive work presents an integrated and modern treatment of the energy principles of mechanics. An introductory chapter on the general concepts and principles of mechanics is followed by discussions of applications to dynamics of rigid bodies, analysis of elastic frames, general elastic theory, the theory of plates and shells, the theory of buckling, and the theory of vibrations. Geared toward advanced undergraduates and graduate students of engineering, the text's prerequisites include familiarity with the calculus of variations and vector theory as well as some knowledge of advanced strength of materials and the foundations of elasticity theory. The treatment is also suitable for independent study and reference purposes. In addition to a helpful Appendix on quadratic forms, this volume features a substantial section of answers to problems.