Fixed Offshore Platform Design

Author(s):  
I. Karsan Demir
2015 ◽  
Vol 776 ◽  
pp. 313-318
Author(s):  
Muhammad Zubair Muis Alie ◽  
Y.R. Palentek ◽  
D.G. Sesa

One of the most important criterion in the design of fixed offshore platform is to have strength from applied loads which is acting perpendicular to jacket leg section such as axial compression.The axial compressive load acts vertically downward to jacket legs and the deformation on the jacket legs in horizontal direction due to this load is called buckling. In the present study, buckling analysis on pechiko field of fixed offshore platform is performed using Finite Element Analysis (FEA). The fixed jacket platform namely tripod and tetrapod are taken as the object of the analysis. Only the axial compressive load is used in the analysis and the boundary conditions are assumed to be fixed both tripod and tetrapod at the bottom seabed. As a fundamental case, buckling analysis is carried out in plane-section (2D analysis), then the result obtained by FE analysis is compared with the analytical solution.It is found that the result obtained by FE analysis for the critical buckling load is in good agreement with the analytical solution, and the applicability of FE analysis is further used to investigate the deformation of 3D model.


Author(s):  
Dong Cheol Seo ◽  
Tanvir Sayeed ◽  
M. Hasanat Zaman ◽  
Ayhan Akinturk

Offshore oil and gas operations conducted in harsh environments such offshore Newfoundland may pose additional risks due to collision of smaller ice pieces and bergy bits with the offshore structures, including their topsides in the case of gravity based structures particularly in extreme waves. In this paper, CFD (Computational Fluid Dynamics) prediction for wave loads acting on a bergy bit around a fixed offshore platform is presented. Often the vertical column of a gravity based structure is designed against ice collisions, if operating in such an environment. In practices, topsides are usually protected by being placed sufficiently high from the still water level, away from the reach of the bergy bits. This vertical clearance between the still water level and the topside deck is known an air gap. Hence, the amount of the air gap planned for such an offshore structure is an important factor for the safety of the topsides at a given location. In this study a CFD method is applied to estimate the dynamic response of the bergy bit and provide a reliable air gap to reduce the potential risk of the bergy bit collision. In advance of more complex collision simulations using a free-floating ice for the airgap design, CFD analysis of wave load prediction on a stationary bergy bit is carried out and reported in this paper. In the experiments and CFD simulations, the location of the bergy bit is changed to quantify the change of wave load due to the hydrodynamic interaction between the bergy bit and the platform. Finally, the results of the CFD simulations are compared with the relevant experiment results to confirm the simulation performance prior to the free floating bergy bit simulations.


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