Structural Mechanics covers three different aspects of modern engineering: the foundation of structural mechanics, the solution to urgent industrial problems, and the reconstruction of major accidents. This book offers six case studies that teach how to identify the most important phase of the collapse or fracture of a complex system, develop a simple mathematically tractable model, and offer a discussion of the analytical and numerical solutions. This book originated from the lecture notes of Professor Tomasz Wierzbicki who taught at MIT and Stanford University. The notes were amended and improved many times over the years to provide a link between rigorous theoretical foundations with solutions to important engineering problems. The book discusses complex man-made structures under accidental impact or explosive loads, resulting in the loss of life and/or extensive property, infrastructural, and environmental damage. The book deals with reconstructing the sequence of events of such accidents from the structural point of view. The book is not restricted to the accident reconstruction only - concepts and solutions of the elasticity, advance plasticity and ductile fracture were used throughout the reconstruction of the accidents. The additional 17 lectures provide theoretical foundations for the elastic structures, plastic plates and shells, and ductile fracture. Not only is this an essential textbook for graduate students studying structural mechanics, it is also relevant to industry professionals, researchers, and academics in the field of engineering.