Abstract
Although there is a perceptible trend of developing and adopting reliability-based design (RBD) in geotechnical engineering, geotechnical practitioners are used to safety factor-based design (SFBD) due to its simplicity. At the stage of transition from SFBD to RBD, geotechnical practitioners frequently compare RBD results with SFBD results that they get used to for cross-checking. Nevertheless, SFBD and RBD, in theory, may provide different design outcomes because they use different design methodologies and requirements. The equivalence between SFBD and RBD (i.e., with the same feasible designs) can only be achieved under some conditions. This study proposes sufficient conditions for achieving the equivalence between SFBD and RBD based on the probabilistic sufficiency factor (i.e., a fractile of the performance function at the target failure probability level PTE). Simplified verification methods of the proposed sufficient conditions in three simple cases are provided. The proposed sufficient conditions and their verification are illustrated using a gravity retaining wall example with a separable performance function and a deep excavation example with an inseparable performance function. Results demonstrate the validity of the proposed sufficient conditions, under which a unique mapping from the allowable factor of safety to PTE for a given design situation can be established.