Implementation of combined approximations in structural optimization

Some approximation concepts, intended to reduce the computational effort du ring optimization of structural systems, are presented. High quality approx imations of the response functions are introduced and used to evaluate both the constraint values and constraint derivatives. The various approximatio ns are then integrated into an effective procedure for structural optimizat ion. The solution is carried out by selecting a sequence of direction vecto rs in the design space. For each selected direction, optimization is carrie d out in a corresponding two-dimensional design plane, with only a single i ndependent variable. As a result, the number of directions needed to reach the optimum, and the overall computational effort involved in the solution process are significantly reduced. Assuming second-order approximations in some typical examples, it has been found that only two to three exact analy ses are needed to achieve the optimum. Moreover, for higher-order approxima tions, a single exact analysis is sufficient for the whole design process. (C) 2000 Civil-Comp Ltd. and Elsevier Science Ltd. All rights reserved.