LINEAR ANALYSIS OF SCOURING EFFECT TO THE STRENGTH OF OFFSHORE PLATFORM STRUCTURE

• Main Author: Kiesin, Willy
• Format: Final Project
• Language: Indonesia
• Subjects: Teknik sipil
• Online Access: https://digilib.itb.ac.id/gdl/view/35884
• Institution: Institut Teknologi Bandung

Offshore platform becomes an important infrastructure in supporting eksploration and production activities in offshore area. Jacket type platform especially installed in Indonesia’s water territory which commonly consists of shallow and intermediate depth water. One of the common problem that occurs to this type of structure is scouring phenomenon, which is an erosion phenomenon around an offshore structure because the structure itself caused a disturbance of current flow around it. In designing and analyzing jacket type platform, a designer need to consider scouring phenomenon into account. One of a method that can be used to analyze the scour’s effect is sensitivity analysis. In the sensitivity analysis, changes in the strength parameter of structure, which obtained from linear analysis, is corelated with the depth of scour Linear analysis dan scour modelling conducted using SACS software. Linear analysis performed considering three conditions: inplace, fatigue, and seismic condition. From those analysis output of strength parameter obtained, which are members and joints’ unity check (UC), pile’s safety factor, and joint’s service life. scour modelling conducted by modify the mudline’s elevation below the structure, changing the pile’s coordinate, reducing the piles’ length beneath the mudline, and adjusting the soil characteristic data for each scour depth considered in the model. Sensitivity curves are the output produced from the sensitivity analysis conducted. These curves can be used to predict the change of strength parameter for each scour depth which occurs. The steepest tangent line in sensitivity curves can be used to make a concervative estimation to the change of structural’s strength parameter due to the scour. For inplace and seismic analysis performed, sensitivity analysis shows that with increasing of the scour’s depth on platform’s structure, the members’ and joint’s UC parameter tend to increase, especially in jacket part of the structure. On the contrary, there is a decrease in the pile’s axial safety factor due to the increase of the scour’s depth. Fatigue analysis also shows that there is a decrease in the platform’s joint service life for each feet of the scour’s depth.