Calibration of resistance factors for reliability-based design of driven steel piles considering separate factors for toe and shaft resistances

ABSTRACT

The LRFD method employs the geotechnical resistance factor (GRF) to design pile foundations. Different resistance mechanisms at the end and side of the pile lead to the requirement of separate GRF values for the shaft and toe capacities. The main aim of this study is to establish regionally separate GRFs for the toe and shaft resistances of pile foundations using different reliability analysis methods. A comprehensive database was gathered from field tests conducted in Alberta, Canada, involved 623 Pile Driving Analyzer (PDA) tests and 28 static load tests. Two criteria called ‘70% rule’ and ‘R ratio’ were used to evaluate the results. Due to certain limitations in the definition of the ‘70% rule’, the ‘R ratio’ method yielded more realistic results. The results indicated that employing separate GRFs for shaft and toe resistances can lead to a significant increase in the factored pile resistance when compared to the values suggested by the Canadian Foundation Engineering Manual (CEFM) in the case of redundant piles.

KEYWORDS:

• Pile bearing capacity
• PDA test
• toe and shaft resistance factors
• regionally calibration
• reliability methods

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The financial support for this investigation was provided by Mitacs Accelerate Program, joint with General Construction Improvement Co.