Deterministic Design, Reliability-Based Design and Robust Design

Due to the inherent uncertainties or variabilities in loads, materials and manufacturing quality, variabilities are unavoidable in structural responses. To ensure the reliability of a structure, these uncertainties or variabilities must be considered during structural design. Through a simple cantilever box beam example, the concepts and practices of three design methodologies: deterministic design, reliability-based design, and robust design, are examined in this paper. Particular attention is given to the meaning of robust design and its definition in the context of reliability-based design. Several robustness criteria are studied and proposed in an attempt to search for a proper objective function in a reliability-based design framework. The stress analysis is carried out using both MSC/ NASTRAN and an analytical formula.