New LRFD-Based Design Criteria for Mobile Offshore Units and Floating Production Installations

Abstract

A new set of Load and Resistance Factor Design (LRFD) based structural design criteria that is compatible to the existing Working Stress Design (WSD) criteria in the ABS classification rules for mobile offshore units (MOUs) and floating production installations (FPIs) has recently been developed. This paper presents an overview of the new LRFD-based structural design criteria with a primary focus on their applications, the load combinations, and the partial safety factors. The paper also presents a summary of the verification case studies for typical MOUs and FPIs. The case study results provide a direct comparison between the new LRFD-based design criteria and the current ABS WSD criteria, which have been used for designing numerous MOUs and FPIs. The verification case studies demonstrate the suitability of the LRFD-based design criteria. The new LRFD-based design criteria are expected to provide an alternative method to designers, owners and operators, who can choose their preferred design approach that meets the local national requirements and better utilizes their experience and resources.