A Comparison of Reliability Based Optimum Designs and AISC Code Based Designs

A comparison of designs of steel frames using a reliability optimization procedure and the deterministic AISC code procedure is presented. The reliability based optimization procedure utilizes an iterative method to produce designs for each structure at various prescribed risk levels. The optimum risk level, expressed in terms of the probability of failure of the structural system, is then obtained as that value which results in the minimum total expected cost. The results indicate that there are significant differences in designs obtained by the two methods for the five and ten story steel frames considered. The AISC design results in a structure with lower initial cost than the reliability based method. However, the reliability based method produces designs with lower total expected cost. It is also found that designs based on the AISC specifications do not result in a consistent system failure probability. This article is from Proceedings of the International Symposium on Optimum Structural Design, AD-A119 989. Prepared in cooperation with Union Carbide Corp., South Charleston, WV.