ABSTRACT
The design approach based on the overall factor of safety has long been used by geotechnical engineers. More recent alternatives are the load and resistance factor design (LRFD) approach in North America, and the characteristic values and partial factors used in the limit state design approach in Eurocode 7 (EC7). Yet another approach can play at least a useful complementary role to LRFD and EC7, namely the design based on a target reliability index that explicitly reflects the uncertainty of the parameters and their correlation structure. Among the various versions of reliability indices, that based on the first-order reliability method (FORM) for correlated non-normals is most consistent. A special case of FORM is the earlier Hasofer and Lind index (1974) for correlated normal random variables. These reliability methods are described in Ditlevsen (1981), Ang and Tang (1984), Madsen et al. (1986), Haldar and Mahadevan (1999), Melchers (1999), and Baecher and Christian (2003), for example. In addition, Low and Tang (1997a, 2004, 2007) presented spreadsheet-based practical procedures for FORM reliability-based analysis and design, with the 2007 approach being an equally efficient alternative as the 2004 approach, and the 2004 approach being much more versatile and efficient over the 1997 prototype.
