Calibration of Model Uncertainties for Fixed Steel Offshore Platforms Based on Observed Performance in Gulf of Mexico Hurricanes
Publication: Journal of Geotechnical and Geoenvironmental Engineering
Volume 146, Issue 6
Abstract
Data obtained during and after major hurricanes in the Gulf of Mexico (GoM) in the past three decades provide valuable information about the design model uncertainties for fixed steel offshore platforms because multiple offshore platforms were loaded close to and/or beyond the predicted capacity and, in particular, because multiple damages/failures were observed in the jacket superstructures, and a three-pile jacket system was well documented and extensively studied in the postfailure stage. The objective of this paper is to extract information on the current fixed offshore platform design practice by comparing the predicted versus observed performance of 18 offshore platforms in five major GoM hurricanes using Bayes’ theorem. The Bayesian calibration indicates that the American Petroleum Institute design recipe, on average, (1) is close to being unbiased for assessing the safety margin for the jacket superstructure performance, (2) tends to be unbiased for the pile lateral capacity using the upper bound lateral bearing factor in curves with the mean yield strength of pile steel, (3) is slightly conservative by 5% for the pile axial capacity in clay, and (4) is conservative by close to 50% for the pile axial capacity in sand. It is concluded that a jacket system with four or more legs/piles is less likely to fail in the foundation system than in the superstructure.
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Data Availability Statement
The following data, models, or code generated or used during the study are available from the corresponding author by request: MATLAB codes for Bayesian calibration.
Acknowledgments
The majority of this work was completed when the first author was at The University of Texas at Austin. We acknowledge the Bureau of Safety and Environmental Enforcement and the American Petroleum Institute for providing financial support through the Offshore Technology Research Center for the projects upon which this paper is based. We also acknowledge our collaborator Energo Engineering, and acknowledge Shell Global Solutions (US), Inc. and Shell International Exploration and Production, Inc., for the permission to publish this paper. The views and opinions are those of the authors alone and do not necessarily reflect those of any of the sponsors or other contributors.
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©2020 American Society of Civil Engineers.
History
Received: Jun 13, 2019
Accepted: Nov 25, 2019
Published online: Mar 23, 2020
Published in print: Jun 1, 2020
Discussion open until: Aug 23, 2020
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