The main purpose of this book is to introduce the reader to the fundamental analytical concepts of the design of minimum-weight structures. This subject, more broadly termed structural optimization, is currently enjoying great interest in the engineering research. The goal of structural optimization is to create finite-element based iterative modeling systems, which will enable the establishment early in any design of the structural layout required for minimum-weight design. Once this layout is known, the remaining detailed design engineering can follow well established steps. To emphasize that the difficult task of layout, or topology is being undertaken, the topic is often referred to as topological structural optimization (TSO). It is likely to become a very important tool as TSO methods develop and the desire to reduce the material content and weight of new products continues to increase. The subject of structural optimization was established at the turn of the last century by an Australian engineer A.G.M. Michell. This work has received new attention over the last two decades because it serves as the theoretical base for numerical approaches to improved structural design.