At the 10th edition of the International Pipeline Conference (IPC2014), our senior pipeline consultant Filip Van den Abeele will present a paper on structural reliability of free spanning pipelines. The paper covers a risk based evaluation of free spans, by applying the principles of structural reliability theory to the problem of long free spanning pipelines subjected to vortex induced vibrations.

Abstract: Structural Reliability of Free Spanning Pipelines

Filip Van den Abeele, Frédérique Boël and Jean-François Vanden Berghe, Fugro GeoConsulting Belgium

When installing subsea pipelines on an uneven seabed, the free spans can be vulnerable to fatigue damage caused by vortex induced vibrations (VIV). Indeed, even moderate currents can induce vortex shedding, alternately at the top and the bottom of the pipeline, at a rate determined by the flow velocity. Each time a vortex sheds, a force is generated in both the in-line and cross-flow direction, causing an oscillatory multi-mode vibration. This vortex induced vibration can give rise to fatigue damage of submarine pipeline spans, especially in the vicinity of the girth welds. Traditional design for VIV is recommended in DNV-RP-F105, which limits the allowable free span length and implies whether (and when) seabed interventions are required.

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SAGE Profile, the market leader software suite for offshore pipeline analysis, is used worldwide for on-bottom roughness analyses, free span evaluation and on-bottom stress analyses. The latest versions of the software are increasingly being used to tackle more complex pipeline problems, like upheaval buckling, pipeline walking and lateral buckling. Recently, the pipeline engineering students at Cranfield University have demonstrated the ability of SAGE Profile to predict susceptibility to lateral buckling

During their research assignment for the M.Sc. in Ocean and Offshore Technology, the pipeline engineering students at Cranfield University performed SAGE Profile simulations of lateral buckling on a full 3D Digital Terrain Model. The SAGE Profile results compared well with analytical approximations (Hobbs theory) and the Abaqus benchmark.

Different methods to fire an engineered buckle were explored, like introducing (dual) sleepers, adding buoyancy modules, locally reducing seabed friction factors, or performing snake lay simulations. The results indicated that SAGE Profile can be used to evaluate the susceptibility to lateral buckling for high pressure, high temperature pipelines and flowlines.

Lateral buckle triggered at sleeper location in SAGE Profile 3D Viewer

Cranfield students with Filip Van den Abeele

The SAGE Profile team will be present at the 37th edition of the Offshore Pipeline Technology Conference (OPT) (26th and 27th February 2014, Amsterdam) and preceding Focus Day on Offshore Pipeline Buckling (25th February).

On February 25th, Jean-Christophe Ballard, a senior consultant of Fugro’s Geotechnical Consultancy Services, will make a presentation focussing on the ultimate uplift capacity of offshore pipelines in undrained clay.

During the conference, we will also present, together with Shell UK Ltd., a paper discussing soil structure interaction analyses performed to aid in the design of a rock berm to provide restraint to a surface laid pipeline in the case of full bore rupture of the line.

Join us at the Fugro booth for a Live Demo of SAGE Profile, and to meet our geotechnical engineers and pipeline consultants. We look forward to meeting you at OPT in Amsterdam!