Calibration of Load and Resistance Factors of API RP 2A-LRFD, Second Edition, for Fixed Offshore Platforms
Publication: Journal of Structural Engineering
Volume 147, Issue 2
Abstract
Fixed offshore platforms in the Gulf of Mexico (GoM) are traditionally designed following the working stress design (WSD) format, that is, the factor of safety approach. In 1993, the first reliability-based design standard for offshore platforms using the Load and Resistance Factor Design (LRFD) format was published by the American Petroleum Institute (API) called Recommended Practice for Planning, Designing, and Constructing Fixed Offshore Platforms—Load and Resistance Factor Design, which is commonly abbreviated as API RP 2A-LRFD 1st edition. API RP 2A-LRFD 1st edition has had a significant influence in developing the LRFD format of the ISO for fixed offshore structures (i.e., ISO 19902), but it was not commonly used in the United States, and it was withdrawn in 2012 due to a lack of maintenance. The API RP 2A-LRFD format was reintroduced in 2014 as a draft 2nd edition. This study was carried out in the context of the plan to prepare the API RP 2A-LRFD 2nd edition under the effort to align and merge the API and ISO standards as a single global standard. The objectives of this study are to assess the fixed offshore platform component reliability with the accumulated experience in the last several decades, and to evaluate the suitability of the load and resistance factors in API RP 2A-LRFD 1st edition for the 2nd edition of API LRFD given the updated metocean characteristics after Hurricane Katrina in the GoM. The key findings of this study are that the LRFD format with the load and resistance factors from API RP2A-LRFD 1st edition gives slightly higher reliability levels for component checks than the WSD format, but lower reliability level with the updated new metocean criteria comparing to the criteria in the 1980s. A list of recommendations on the load and resistance factors was provided to facilitate the preparation for the API RP2A-LRFD 2nd edition.
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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 component reliability calculations and statistics for component capacity model uncertainty.
Acknowledgments
The majority of this work was completed when the first author was at the University of Texas at Austin. We acknowledge the American Petroleum Institute (API) for providing the financial support to conduct this work. We also acknowledge the continuous support from the Bureau of Safety and Environmental Enforcement. We specially acknowledge Dr. Albert Ku and Dr. JY Chen formerly with Energo Engineering for providing the data and damage assessments for the case study platforms, the access and training with SACS software, and the technical guidance. Without their help, this study would not be completed. We benefited significantly from the discussions with Dr. Peter Marshall, and Mr. Vul Thang from Bentley Systems, Inc. We also acknowledge Shell Global Solutions (US) Inc. and Shell International Exploration and Production Inc. for the permission to publish this paper. The views and opinions contained in this paper are those of the authors alone and do not necessarily reflect those of the sponsors or other contributors.
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Published In
Journal of Structural Engineering
Volume 147 • Issue 2 • February 2021
Copyright
© 2020 American Society of Civil Engineers.
History
Received: Jun 12, 2019
Accepted: Sep 10, 2020
Published online: Dec 2, 2020
Published in print: Feb 1, 2021
Discussion open until: May 2, 2021
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