Detailed engineering design was carried out in 2011-2012 for structural strengthening of an offshore tower to accommodate additional loading caused by higher metocean criteria.

The Client

Woodside Energy Ltd.

The Scope

Analysis and Design of Strengthening for Offshore Flare Tower, Goodwyn A-Platform. The engineering works involved the assessment of load capacity increase by grouting of tower leg using Ultra High Performance grout.

The Challenges

About 30 scenarios were investigated to assess the load carrying capacity of the offshore tower. The scenarios considered a composite case as well as various non-composite cases with different steel-grout interface bonds. Also, different frictional coefficients and shrinkage effects were investigated. Finally, the analysis considered different grouting heights and their corresponding load capacity improvements.The engineering analysis was vetted in consultation with DNV and preparation for offshore implementation was then initiated.

The Services

The entire offshore tower was modelled with ABAQUS based on as-built structural drawings. FEA was carried out using concrete damage material model for grout to understand the cracking or crashing of grout. Steel was modelled as elastic-plastic material model. Steel-grout interface was modelled as frictional bond. The engineering approach also included a comparison of the analysis results derived from ABAQUS with those obtained from USFOS.

Client Benefit

The analysis highlighted the load transfer mechanic between the steel and grout in the offshore tower. It was found that the load capacity of the tower may be increased up to 200% depending on the scenarios.

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