Resistance factors for use in load and resistance factor design of driven pipe piles in sands

Abstract

Load and resistance factor design of foundations is done in the offshore industry and is now being done in bridge projects in the United States. Common methods used to establish resistance factors include calibration to assumed factors of safety and reliability analysis using field load test databases. Reliability analyses are the preferred tools for this work but the needed probabilistic information regarding design method uncertainty is difficult to obtain. Furthermore, field load test databases, while relatively attractive for assessing design uncertainty, are not able to discriminate between uncertainties caused by soil variability, test methods, and model design relationships. In contrast to previous efforts, this paper illustrates an approach to uncertainty assessment that seeks to isolate the various sources of uncertainty. Using this approach, reliability analysis is used to develop resistance factors for the design of driven pipe piles in sand. The resistance factor results are used to highlight some of the differences between design methods that are exposed by the proposed uncertainty assessment technique. A brief design example is also given that illustrates the use of the resistance factors.