An optimization based approach for structural design considering safety, robustness, and cost

Structural systems are subject to uncertainties due to variability in many hard-to-control noise factors, which include external loads, material properties, and construction workmanship. Traditional structural design methodologies, although clearly recognizing the presence of uncertainty, omit robustness against the effects of uncertainty in the design process. First, if the actual uncertainties in the design process are underestimated, the design may fail to satisfy safety requirements. Second, to guarantee safety in the presence of high variability of the system response, the structural designer may be forced to choose an overly conservative, thus inefficient and costly design. When robustness against uncertainty is not treated as one of the design objectives, the trade-off between over-design for safety and under-design for cost-savings is exacerbated. This manuscript demonstrates that safe and cost-effective structural engineering designs maybe achieved by implementing Robust Design concepts originally developed in manufacturing engineering to consider robustness against uncertainty. This manuscript presents an optimization-based methodology for the application of Robust Design principles to structural design and demonstrates its application on an academic problem involving design of a reinforced-concrete frame.