ABSTRACT
The means by which a structural design evolves from some initial form to a final form can be described as an optimization process whereby attempts are made to minimize features or to maximize benefits while satisfying design criteria reflecting performance and fabrication requirements. Many researchers over many years have pursued the quest to produce optimal designs. As early as the 1600s, Leonardo da Vinci and Galileo conducted design optimization through planned trials of models or actual full-scale structures. In the 1700s and 1800s, researchers such as Newton, Lagrange and Euler produced optimal designs using numeric calculations based on an optimality criterion that specified the strength of the structure to be uniform throughout all its parts. Maxwell in the late 1900s and Michell in the early part of the twentieth century altered structural form to achieve optimum designs having minimum structure weight. Since the advent of the computer in the last half-century there has been a veritable explosion of studies concerned with the optimal design of structural systems. One recent survey estimates that the modern literature has some 150 books and monographs and over 2500 research papers that deal with the topic of structure design optimization (Cohn, 1991). While some may argue that this long and extensive history of research has resulted in disappointingly few applications of optimization theory in professional practise, one notable exception in this regard concerns the design of structural steel building frameworks. In fact, today, there are a number of commercial software packages based on member-by-member (Computers and Structures, 1989; Research Engineers, 1987) and/or whole-structure (Grierson and Cameron, 1991) optimization that the professional designer may use to produce economical designs of such structures.
