LRFD for Helical Anchors: An Overview

There is a trend for design of foundation elements using Load and Resistance Factor design (LRFD) in place of Allowable Stress Design (ASD). The ASD method accounts for design uncertainties in the form of a factor of safety, whereas the LRFD method assigns various factors to account for each uncertainty in the load and resistance. The 2004 NCHRP study on LRFD developed load and resistance factors for drilled and driven piles. The question is how does this methodology carry over to the design of helical anchors? The determination of regional load and resistance factors can be a daunting challenge for the practicing geotechnical engineer and is one of the reasons why the geotechnical industry fails to fully embrace LRFD. This paper presents a summary of what is required to develop resistance factors for helical anchors. Additionally, the First-Order Second Moment (FOSM) method is applied to a previous helical anchor study to determine resistance factors for an ultimate tension capacity strength limit state