Design-independent calculation in FEM-based optimization programs

In recent years, much effort has been directed towards developing efficient FEM-based optimization/CAD software. Computational efficiency is of vital importance in optimal design of large scale structural systems. The main reason for this is that the iterative design process involves repeated analysis of the structure, which is quite expensive. At every iteration, the design variables are updated until a satisfactory design is obtained. There are many computations, however, which are independent of design variables and therefore need to be performed only once. Such computations can also be looked upon as computations based on unit values for the design variables. The unit design concept does not directly apply to structures which are modeled using beam finite elements. This paper presents a discussion of the unit design concept so as to include applications with beam elements. Some related questions on future developments of FEM software are discussed.