Strength analysis of tripod jacket and skid frame structures during the loadout process

Offshore platforms are constructed worldwide for various needs, particularly in the oil and gas industry. Around 95% of offshore platforms used for oil and gas exploration and exploitation activities are supported by fixed jacket structures. This structure is constructed by the fabricator company and subsequently loaded out onto a barge to be transported to the installation site. The loadout process must be evaluated carefully considering the unpredictable quay side conditions that may cause the jacket structure to be overstressed. Therefore, loadout analysis of the tripod jacket structure using the skidding method was conducted in this research. Global analysis using SACS software was performed to assess the strength of the jacket structure through some loadout scenarios and ensure it satisfied the applied requirements. The results showed that the critical stress occurred at the mudmat member, which has UC (stress ratio) value of 0.91. Besides the jacket structure, a supporting loadout structure, namely the skid frame, also had been analysed. The complexity of the skid frame geometry makes it hard to model and analyse globally. Consequently, local stress analysis of skid frame structure was performed for the most critical conditions using ABAQUS software. Most local critical stress was obtained from this local analysis and had been compared to the allowable stress based on the applied requirements. It showed that there were four critical skid frame components which have von mises stress of 575.60 MPa, 522.20 MPa, 414.50 MPa, and 542.50 MPa. Those values were exceeded the allowable, even two of them exceeded the ultimate stress.