Reliability-based design and assessment for lifetime extension of ageing offshore structures

Abstract

The methodology for Reliability-Based Design and Assessment (RBDA) of an ageing fixed steel offshore structure was established to support detailed re-assessment applied to the management of the structure's safety, integrity analysis and reliability by evaluating the loading acting on the structure. It is a tool for the high-end analysis of the structure for risk-based design assessment and has been succesfully implemented in the North Sea under Shell operating company. The main purposes of RBDA are to manage a structure's risk level over its remaining service life and to initiate the cost-efficient inspection or mitigation actions (if required). This method consists of Type I and II uncertainties used to determine the probability of failure for the structure over its remaining service life. However, limited work has been done so far on its application at many different regions, particularly in the South East Asia. Therefore, this paper investigates the robustness of the RBDA methodology applied to fixed offshore structures at shallow waters of Malaysia by considering the native environmental criteria, local authorities' obligation and company requirements. It is shown that this procedure can efficiently assist in understanding the structure's failure mechanism and correctly define the relevant type of mitigations required.