LRFD Calibration of the Ultimate Pullout Limit State for Geogrid Reinforced Soil Retaining Walls
Publication: International Journal of Geomechanics
Volume 12, Issue 4
Abstract
The results of load and resistance factor design (LRFD) calibration are reported for the pullout limit state in geogrid reinforced soil walls under self-weight loading and permanent uniform surcharge. Bias statistics are used to account for the prediction accuracy of the underlying deterministic models for load and pullout capacity and the random variability in the input parameters. The paper shows that the current AASHTO simplified method to calculate reinforcement loads under operational conditions is overly conservative leading to poor prediction accuracy of the underlying deterministic model used in LRFD calibration. Refinements to the load and default pullout capacity models in the AASHTO and Federal Highway Administration guidance documents are proposed. These models generate reasonable resistance factors using a load factor of 1.35 and give a consistent probability of pullout failure of 1%. A comparison with the allowable stress design (ASD) past practice shows that the operational factors of safety using a reliability-based LRFD approach give factors of safety greater than 1.5. Regardless of the design approach (ASD or LRFD), the analysis results demonstrate that the current empirical minimum reinforcement length criteria will likely control the design for pullout.
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Acknowledgments
Financial support for this study was provided by the Natural Sciences and Engineering Research Council (NSERC) of Canada, grants from the Department of National Defence (Canada), the Ministry of Transportation of Ontario, and the following U.S. State Departments of Transportation: Alaska, Arizona, California, Colorado, Idaho, Minnesota, New York, North Dakota, Oregon, Utah, Washington, and Wyoming.
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© 2012. American Society of Civil Engineers.
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Received: Aug 4, 2011
Accepted: Apr 4, 2012
Published online: Apr 11, 2012
Published in print: Aug 1, 2012
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