Fixed offshore platform: assessment on the possibility of reuse of the jackets for offshore wind farms

Resumo

This paper focuses on the possibility of reusing (or not) a fixed offshore platform, with the purpose to
understand whether the removal of the deck from the platform (partial decommissioning) would be considered
including the replacement for a wind tower. Thus, the present research aims to verify the structural behaviour of
a fixed offshore platform (jacket) when subjected to the loading of a 10 MW wind tower. However, in addition
to the static loading coming from the wind tower, the environmental forces (variable loads) related to the waves
and wind acting on the platform were pondered. The loading related to the 10MW wind tower was considered
and distributed on top of the four legs of the jacket. The investigated structural system presents a 26 m height
jacket (from the mudline); the lower area presents dimensions of 9.97 m x 9.97 m and the upper area 6.10 m x
6.10 m. The structure presents eight legs and three deck elevations between the upper and lower deck. The
numerical model was developed based on the use of the SACS V12.0 computational software, and via the use of
the Finite Element Method (MEF). Therefore, the resistance analysis is performed on the fixed offshore platform
(jacket) considering the influence of the static and variable loadings in order to assess the current structural
behaviour.