Reliability Concepts in LRFD Design - or What is a Reasonable Factor of Safety?

by Julian Seidel, Foundation QA, Melbourne, Australia.

published in Deep Foundations, Summer 2002, pp 29-32.

Summary

The subject of reliability concepts in Load Resistance Factor Design (LRFD) would seem to be a pretty dry subject – perhaps the domain of academics and code writers – and it is. But it is also a subject which has very real and practical implications for all foundation projects. There are many projects in which achieving the specified factor of safety can cause major difficulties, and allowing some rational evaluation of the design requirements and some flexibility in the application of acceptance criteria might be very helpful to the progress of the contract. This paper presents some of the author’s current thoughts on the application of reliability principles to foundation acceptance. The paper is developed around the LRFD approach, however as will be shown, the conversion between LRFD load and resistance factors and global factor of safety is simple and direct.

The included link is to a paper (#240) on analysis of static pile load tests by Fellenius. His Unisoft Ltd web site includes many interesting papers, as well as information about Unisoft software.