Roles of FORM, System-FORM, SORM, and RSM in Geotechnical Reliability Analysis

Abstract

This paper examines the complementary roles and interconnections among the first-order reliability method (FORM) for single failure modes, the system FORM for correlated multiple failure modes, the second-order reliability method (SORM) for curved limit state surfaces, and the response surface methods as a link between reliability methods and stand-alone numerical packages. Geotechnical examples of reliability-based design and analysis will be provided to illustrate the principles, merits and limitations of each, and to explain the connections and evolutionary relationships among FORM, system-FORM and SORM. Comparisons will be made with other probabilistic methods in recent geotechnical literature. Apart from elucidating efficient and practical procedures for reliability-based design and analysis with the hope of engaging more practitioners to consider the probabilistic approach, the paper also aims to provide some discussions and a more balanced perspective of other probabilistic approaches (different from FORM, system-FORM, SORM, RSM) published by various researchers in recent geotechnical papers.