Comparison of the reliability-based and safety factor methods for structural design

Reliability-based design optimization theory has been widely acknowledged as an advanced and advantageous methodology for complex structural system design. Comparatively, the traditional safety factor design method has fallen out of favor with designers since it is simply just a comprehensive expression of all the uncertainties existing in a practical engineering structure, which has been verified to be unreasonable. Moreover, there is no description of the method for searching for the optimal design. In this paper, a comparison of the two approaches is performed for the optimization results and process. It is demonstrated that the weight of the designed structure by the reliability-based optimization is not heavier than that by the safety factor design method under the same reliability requirements. The time efficiency, error estimates and sensitivity analysis are also compared to discuss the advantages and disadvantages of the two approaches. Eventually, the advancement of the reliability-based design optimization is illustrated with optimization designs of a two-bar truss and one practical supersonic wing.