STRUCTURAL RELIABILITY BASED DESIGN AND ASSESSMENT ACCEPTANCE CRITERIA DEVELOPMENT FOR FIXED OFFSHORE PLATFORMS IN SOUTH CHINA SEA UNDER EXTREME STORM CONDITIONS

摘要

This paper presents a reliability based methodology to develop the design and assessment acceptance criteria for fixed offshore platforms in the northern South China Sea under extreme storm events. Firstly, the atmosphere, ocean and wave coupled numeric simulation model with site measurements verification is used to generate the time series directional waves, currents and winds for each refined grid point in the studied area during the past 40 years. Secondly, the storm and response based load statistics method is adopted to investigate the long term distribution of the extreme environmental load considering the joint occurrence of wave, current and wind. Thirdly a structural reliability method is proposed to quantify the probability of platform failure subjected to extreme storms. The environmental load factors for new design platforms in the northern South China Sea with different exposure categories are calibrated. Finally risk assessment is performed to develop the acceptance criteria for the exiting platforms in terms of reserve strength ratio based on the failure consequence and failure probability of platforms. Case studies are presented to illustrate the applications of the proposed method and how the reliability analysis results can be used in development of long term structural integrity management strategies.