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The objective of this paper is to assess the impact of soil axial resistance on initiation of the buckles on sleepers. It also covers the effects of history of pressure and temperature increase on effective axial force as well as the incorporation of external pressure in the Finite Element (FE) models. This is carried out for 6″, 8″, 10″ and 12″ pipelines laying on sleepers with different heights for a range of axial soil frictions and mobilisations. Knowing the sensitivity of buckle initiation to soil parameters can help in simplifying engineering analysis by avoiding repetitive simulations for parameters with less importance. To carry out the above, a series of FE models including normal and bi-linear axial contacts between pipeline and sleeper / seabed were built in Abaqus FE package and at the point of initiation of the buckles, the effective axial force was extracted by a Python script. FE models were validated by comparison of the simulation results with analytical solutions and experimental results from published literature.

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Design by Analysis (DBA) based on nonlinear finite element analysis provides an efficient method to design subsea pipeline components. This approach is widely used in oil and gas industry for subsea pipeline components design and pressure vessels. In contrast to linear analysis and stress linearization/categorization, the nonlinear finite element analysis approach provides a more accurate and efficient design route. The design codes encourage the use of the nonlinear analysis approach especially for components with complex geometry. In this paper, the Design by Analysis approach of ASME VIII D2 and BS-EN-13445-3 using nonlinear finite element method are compared and discussed. These two codes are widely used standards for design of pipeline components and pressure vessels. The philosophy of both codes is limit state involving load and resistance factors. In this paper, emphasis is given to component design in ultra-deep water condition and its significant effect on design during operational cyclic loads. For comparison purpose, a subsea inline Tee is designed to both codes and subsequently the design outcomes are compared and discussed.