Resistance Factors for Use in Shallow Foundation LRFD
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 132, Issue 9
Abstract
In shallow foundation design, the key improvements offered by LRFD over the traditional working stress design (WSD) are the ability to provide a more consistent level of reliability between different designs and the possibility of accounting for load and resistance uncertainties separately. In the development of LRFD, a framework for the objective, logical assessment of resistance factors is needed. Additionally, in order for LRFD to fulfill its promise for designs with more consistent reliability, the methods used to execute a design must be consistent with the methods assumed in the development of the LRFD factors. In this paper, a methodology for the estimation of soil parameters for use in design equations is proposed that should allow for more statistical consistency in design inputs than is possible in traditional methods. Resistance factors for ultimate bearing capacity are computed using reliability analysis for shallow foundations both in sand and in clay, with input parameters obtained from both the cone penetration test and the standard penetration test, and for both ASCE-7 2000 and AASHTO 1998 load factors. Resistance factor values are dependent upon the values of load factors used. Thus, a method to adjust the resistance factors to account for code-specified load factors is also presented.
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Acknowledgments
This work was supported by the Joint Transportation Research Program administered by the Indiana Department of Transportation and Purdue University. The contents of this paper reflect the views of the writers, who are responsible for the facts and the accuracy of the data presented herein. The contents do not necessarily reflect the official views or policies of the Federal Highway Administration and the Indiana Department of Transportation, nor do the contents constitute a standard, specification, or regulation.
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Published In
Journal of Geotechnical and Geoenvironmental Engineering
Volume 132 • Issue 9 • September 2006
Pages: 1208 - 1218
Copyright
© 2006 ASCE.
History
Received: Feb 7, 2003
Accepted: Jan 31, 2005
Published online: Sep 1, 2006
Published in print: Sep 2006
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