American Society of Civil Engineers

Reflections on LRFD for Geotechnical Applications

by George G. Goble, Ph.D., P.E., M.ASCE, (Consulting Engineer, LLC; 5398 Manhattan Circle Suite 100; Boulder, CO 80303)
Section: LRFD and Reliability-Based Design for Deep Foundations, pp. 1-9, (doi:

     Access full text
     Purchase Subscription
     Permissions for Reuse  

Document type: Conference Proceeding Paper
Part of: Contemporary Issues in Foundation Engineering
Abstract: Load and Resistance Factor Design (LRFD) has now been in use for structural element design for more than 40 years. In facilities where the structure is routinely designed by LRFD, the foundation will be designed based on Allowable Stress Design (ASD). This lacks consistency and does not take advantage of the desirable features of LRFD. In the process of developing resistance factors for deep foundations using a probabilistic analysis some puzzling results have been obtained. Why are the probabilities of failure for typical ASD designs so large? A similar condition does not exist for structural elements. What is being overlooked? Is there something wrong with the data? There is no point in performing extensive probabilistic analyses to determine resistance factors if unrealistic failure probabilities are used.

ASCE Subject Headings:
Load and resistance factor design
Geotechnical engineering
Deep foundations