DESIGN AND ANALYSIS OF NON-LINEAR INELASTIC SEISMIC PUSHOVER OF FOUR LEG OFFSHORE PLATFORM IN THE NORTH JAVA SEA

• Main Author: Auliya, Alfiza
• Format: Final Project
• Language: Indonesia
• Subjects: Teknik (Rekayasa, enjinering dan kegiatan berkaitan)
• Online Access: https://digilib.itb.ac.id/gdl/view/84972
• Institution: Institut Teknologi Bandung

Offshore platforms are structures or facilities built and operated offshore. These structures are the upstream part of oil and gas production. The assessment of platform structures is carried out to ensure sustainability, safety, structural performance, and to maximize the potential of existing oil and gas. In this final project, the methods include prequalification analysis for platforms that are already in operation. The feasibility study of the platform is evaluated using structural modeling software in accordance with the standards of API RP 2A 22nd Edition and AISC - Steel Construction Manual 15th Edition. The study begins with an in-place analysis to ensure the structure can withstand loads during operation, including gravity loads, environmental loads, and loads during extreme environmental conditions. Next, the structural evaluation is carried out with seismic analysis under ELE and ALE conditions to determine the structure’s strength against ground movements at the installation site. Then, a fatigue analysis is conducted to estimate the damage and lifespan of the structure due to cyclic loads. In the seismic ductility analysis, where some members have capacities below the design, further analysis is conducted to determine the integrity of the platform, namely pushover analysis with earthquake loads under nonlinear inelastic material conditions on the offshore structure model. This analysis results in the Reverse Strength Ratio or the highest/reserve strength of the structure when subjected to earthquake loads. Modeling and structural analysis are carried out using modeling software (Structural Analysis Computer System) and finite element method analysis software. Based on the results of in-place, seismic, and fatigue analyses, the structure meets the API RP 2A criteria with the condition of continued checks for ductility, thus categorized as fit for operation. In the pushover analysis, it is found that the Reserve Strength Ratio (RSR) in the lateral X+ direction is 3.48, in the lateral X- direction is 4.06, in the lateral Y+ direction is 4.39, and in the Y- axis is 4.95. Thus, the structure has a high reserve capacity during an earthquake and meets the API RP SIM criteria.