Characterization of Model Uncertainty in the Static Pile Design Formula
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 137, Issue 1
Abstract
Level 1 reliability methods have been internationally accepted as the basis for development of the new generation of geotechnical design codes. A key requirement of this design approach is the identification and quantification of uncertainties associated with the geotechnical design under consideration. This paper presents four load test databases from South Africa for driven piles in noncohesive soils (29 tests), bored piles in noncohesive soils (33 tests), driven piles in cohesive soils (59 tests), and bored piles in cohesive soils (53 tests). The capacity model factor is defined as the ratio of the interpreted capacity (Chin-Davisson approach) and the predicted capacity (static pile design formula). The uncertainty in the capacity model factor is modeled as a lognormal random variable. The model factor statistics reported in this study are required for reliability-based ultimate limit state design. The uncertainty in the load-settlement behavior is characterized by fitting measured load-settlement data to a hyperbolic equation and then normalizing the hyperbolic curve with the interpreted capacity. The resulting exercise reduces uncertainties in a set of nonlinear continuous curves to uncertainties in two hyperbolic curve-fitting parameters. This approach is practical and grounded realistically on the load test database with minimal assumptions. The hyperbolic parameter statistics reported in this study are required for reliability-based serviceability limit state design.
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Acknowledgments
The writers are grateful to South African companies who helped in providing pile load test data. These included Franki Africa, Dura Piling, Jones and Wagener, Stefanutti and Bressan, and Gauteng Piling.
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Information & Authors
Information
Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 137 • Issue 1 • January 2011
Pages: 70 - 85
Copyright
© 2011 ASCE.
History
Received: Jul 23, 2008
Accepted: Jun 7, 2010
Published online: Jun 10, 2010
Published in print: Jan 2011
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