Modification to and Applications of the Guidelines for Assessment of Existing Platforms Contained in Section 17.0 of API RP 2A
Authors: Digre K.A. , Puskar F.J. , Aggarwal R.K. , Irick J.T. , Kreiger W.F. , Petrauskas C. 
Published: October 2008

On April 1, 1995 the API officially issued a draft Supplement I for both the WSD and LRFD versions of API RP 2A1,2. This draft will be open for review for a period of one year and contains a modified Section 14 plus two entirely new Sections, 17 and 18. This paper deals with Section 17, Assessment of Existing Platforms (previously released as a Working Draft) and describes the modifications incorporated into Section 17 (Section R in LRFD version) based on initial industry review and early feedback From a Joint Industry Project4 (JIP - including the Minerals Management Service [MMS] and 21 participating companies) involving a trial application of the draft guidelines.

Addressed herein are lessons learned during the JIP trial applications including recommendations for final guidelines, applicability of the assessment process, criteria and selected applicable results. Also included are data obtained in the "Benchmark" portion of the JIPS where 8 participants and 5 additional engineering firms applied the guidelines to the same structure. That effort involved not only determining theAPI RP 2A 20th edition 100-year load but also performing detailed analysis for appropriate Ultimate Strength Level loading..

BACKGROUND

The API Task Group 92-5 has been working on the development of a process for the assessment of existing platforms to determine their fitness-for-purpose since June of 1992. Their efforts were initially released to the public prior to the International Workshop on Reassessment and Requalification of Offshore Productions Structures, held in NewOrleans in December, 19936. The basis of TG 92-5's work, including details and justification for specific processes, criteria and methodology were presented at the 1994 0TC7,8,9,10,11,12,13and BOSS'94 14conferences.

While writing the noted papers, TG 92-5 was in the process of performing a major revision to the Working Draft version of Section 17. As planned, the revised draft would incorporate industry feedback received at the December '93 conference and later plus remove "commentary" now contained in the reference papers. TG 92-5 recognized that a "trial" application of the Section 17 process on a number of existingplatforms would be the best test or validation of the process and its underlying assumptions.

In early 1994, the MMS and a number of interested organizations funded a JIP to perform this trial application of Draft Section 17. There were two main parts to the Trials JIP. The first part was a trial application to a number of platforms. The second part was a comparison of results of nonlinearanalyses pardoned on a single "benchmark" platform by several organizations in order to determine the variability in results for ultimate strength analysis, a key to the Section 17 assessment process.

MODIFICATIONS TO SECTION 17 WORKING DRAFT

TG 92-5 received numerous comments regarding the Working Draft version of Section 173 from participants in the TrialsJIP, attendees at the 1993 Workshop and other users. All were discussed at length and appropriate modifications were made resulting in the final draft version contained in API Supplement 1 to API RP 2A1,2. Significant modifications made include.