Optimum Design of Structures at Elevated Temperatures

Abstract

This paper describes optimum design techniques for structures where high temperatures are important design considerations. An improved variant of fully stressed design (FSD), denoted thermal fully stressed design (TFSD), is described which converges significantly faster than FSD for problems where thermal stresses are comparable in magnitude to mechanical stresses. Also, an optimali ty criterion is described for sizing structures subjected to temperature constraints. Simultaneous requirements on strength and temperatures are handled by two different techniques: 1) state-of-the-art mathematical programming method and 2) the optimality criterion technique for temperature constraints combined with FSD for strength constraints. Finally, a method is described to optimize the insulation and ply thickness of an insulated composite panel with a time-varying temperature applied to the outer surface of the insulation and a general set of in-plane loads applied to the panel. Temperature and strength constraints are satisfied at a specified number of times. Only a small number of such discrete times are necessary for adequate results for an example contained herein.