Purpose:

Pythagoras Engineering is in exponential improvement to widen the variety of analyses with different trending products in respective industries. The purpose of this presentation is to provide an insight of technical requirements and the numerical calculations performed using FEA techniques to evaluate the nonlinear buckling capacity of the Suction Anchors. ANSYS mechanical was used for the FEA simulation. 

Scope:

The objective of this FEA is to determine the nonlinear buckling capacity (GMNIA) of the suction anchor under the application of suction pressure. Nonlinear buckling analysis is performed as per EN 1993-1-6 and safety factors as per DNVGL-RP-C208. The utilization ratio is checked against the required suction pressures to penetrate into the sediment. 

Background:

The suction anchors are a form of an open-bottomed tube embedded into the sediment and sealed at the top. Suction Anchor acts as foundation support for Manifolds, UTA/UTH, Jackets, Moorings, Wind Turbines etc. Today’s suction anchor is known with quicker to install and de-commission. It is installed by pumping-out water trapped inside after self-penetration, and it is de-commissioned by pumping-in the water.

Methodology:

The FE model was generated using ANSYS mechanical. The suction anchor is a cylindrical shell with a higher D/t ratio. The component is meshed with higher-order SHELL elements. Shared topology is maintained for beams welded to top plate.  The sediment boundary support is modelled with the help of radial springs with nonlinear stiffness values. As per DNVGL-RP-C208, Elastic-plastic calculations, the multilinear kinematic material model was used to account for the material non-linear behavior. The suction pressure loads are applied to a component. The analyses follows Pre-Stress Analysis (unit load analysis), Eigenvalue Buckling Analysis (Linear Buckling Analysis) and then Nonlinear Buckling Analysis (GMNIA) with incremental steps to evaluate the collapse load. The repetitive analysis procedure is performed at different instantaneous penetration depths during its complete installation into the sediment. Applicable safety factors are applied as per DNVGL-RP-C208 and verified against the required installation suction pressures. The design is acceptable and meets the required industrial requirements.

Results Outcome:

FEA results are used to evaluate the suction anchor design as per the EN 1993-1-6, DNVGL-RP-C208 industrial codes and the utilization ratios are found to be acceptable.