Expanded Reliability-Based Design Approach for Drilled Shafts
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 137, Issue 2
Abstract
This paper develops a more general reliability-based design approach for drilled shafts that formulates the design process as an expanded reliability problem in which Monte Carlo simulations (MCS) are used in the design. Basic design parameters, such as the shaft diameter and depth , are formulated as discrete uniform random variables. Then the design process becomes one in which failure probabilities are developed for various combinations of and [i.e., conditional probability ] and are compared with a target probability of failure . Equations are derived for this expanded reliability-based design approach, and criteria are established for the minimum number of MCS samples to ensure a desired level of accuracy. Its usefulness is illustrated using a drilled shaft design example. This approach has the following advantages: (1) it gives results that agree well with current RBD designs, but it improves the resolutions of the designs; (2) it offers design engineers insight into how the expected design performance level changes as and change; (3) it gives design engineers the ability to adjust , without additional calculation effort, to accommodate specific needs of a particular project; and (4) it is transparent and “visible” to design engineers who are given the flexibility to include uncertainties deemed appropriate. Finally, the effects of uncertainties in the at-rest horizontal soil stress coefficient and allowable displacement are illustrated using this approach.
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Acknowledgments
The work described in this paper was supported by a grant from the Research Grants Council of the Hong Kong Special Administrative Region, China [Project No. UNSPECIFIED9041260 (CityU 121307)] and a grant from City University of Hong Kong (Project No. UNSPECIFIED7002568). The financial supports are gratefully acknowledged. The writers would also like to thank the anonymous reviewers for their valuable comments, which certainly helped to improve the quality of the manuscript.
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© 2011 ASCE.
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Received: Jan 14, 2010
Accepted: Jul 24, 2010
Published online: Jan 14, 2011
Published in print: Feb 2011
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