Structure Analysis of Deep Water Spar Platform

In order to study calculation technology of global structure strength for the deep water typical Spar platform its global structural strength analysis is completed. The dynamic-part and a low frequency-part loads are considered in this analysis. First, according to the 100-year return storm design wave parameters are obtained through search. wave loads with design wave parameters are calculated, and are applied to the structural model built. The stresses of global structure are gotten by finite element structural analysis. Then, low frequency-part loads which include wind, current and mooring forces also are applied to the structural model. The stresses produced by low frequency-part loads are gotten by finite element structural analysis. Finally the stresses produced by dynamic-part and a low frequency-part loads are combined to form total stresses of structure of Spar, and evaluation of structural strength of Spar is made in term of the rule. Analysis method for the structural strength of the deepwater typical Spar platform can be used as reference for relative technical people.

Hydrodynamic Analysis of Floating Docks With Alternative Geometries for Floating Wind Turbine Installation

Installation of spar floating wind turbine offshore is a challenging task. Usually, the spar platform is upended first, and mating of the tower assembly with the spar platform is assisted by a crane vessel. Due to motions of the spar platforms and of the crane vessel, such an operation often takes place in shielded areas with relatively small wave heights and wind speed. The floating dock concept has been recently proposed to expand the weather window for installing spar floating wind turbines. The idea is to use a cylindrical dock to shield the spar platform from wave excitations. However, because of the trapped internal fluid, the cylindrical geometry is subjected to piston mode and sloshing mode excitations, and these modes may fall in the wave periods and cause unfavourable response characteristics. This paper investigates the influence of floating dock geometries on the piston and sloshing modes. We assumed a homogeneous mass distribution of the floating dock and changed the geometry of the cylindrical dock by expanding or reducing the neck area. Then, hydrodynamic analysis of the alternative geometries was carried out using a potential flow code. By comparing the system’s piston modes and sloshing modes, we identified the trend of variation and found that an expanded neck area can lead to increased sloshing period and piston mode. This indicates a potential improvement of the dock responses in operating sea states. The results of this analysis can be used in the shape design optimisation in a future work.

Damage Monitoring of a Catenary Moored Spar Platform for Renewable Energy Devices

Structural performance of renewable energy device platforms is central to their power generation in a reliable and competitive manner. However, there is a gap in research in the conceptual and experimental stages of such devices at lower technological readiness levels in terms of understanding of their structural responses. Uncertainties around knowledge related to damage conditions of such structures are under-researched and experimental investigations into the monitoring of performance of such structures are significantly needed. This research addresses this need and investigates various damage conditions in a scaled catenary moored spar platform in an ocean wave basin, exposed to typical wave conditions for the west coast of Ireland. A comparison of the monitored structural responses was carried out with respect to the undamaged experimental model. It was observed that while free decay tests were not useful to distinguish between various damage levels, a characterisation of the distribution of the responses can be relevant in identifying damages or significant structural changes. The work contributes to the much-needed experimental evidence base around structural health monitoring of renewable energy device platforms.