Innovative Assessment Approach to Quantify the Impact of Load Additions and Mitigation Strategies on Existing Offshore Platform Structures

Abstract

Offshore structures usually experience many stages of alterations, modifications, load additions and strengthening work during its operational life to meet increased production plans and/or changes in process/safety philosophies. Significant load increases are likely accompanied with strengthening schemes to cater for such additions. Conventional design methods for assessing these modifications employ linear structural assessment that do not account for actual history of loading/strengthening. Conventional design practices and current design codes do not provide specific guidelines covering the effect of progressive loading and staged strengthening in a manner that ensures accurate distribution of loads into the supporting structural elements. This paper illustrates the benefits of employing progressive loading and staged strengthening over conventional approach. The benefits are highlighted through two case studies involving the Re-assessments of ADMA's Collector Separator Platform (CSP) and Bridge B5 connecting the CSP to Riser Platform. The assessment of these structures utilizing this innovative approach were carried out to demonstrate that these structures are meeting code (API WSD/ISO19902) compliance under the proposed additional loading.