Abstract
The paper is in support of the effort by the Marine Renewable Energy (MRE) Committee of the ASCE Coasts, Oceans, Ports, and Rivers Institute (COPRI) for setting up a guide document for offshore renewable energy foundations. The guide would use standard design codes for fixed foundations and mooring anchors in API, ISO and DNV. This paper focuses on specific aspects of design of offshore wind turbines that distinguish them from oil and gas installations. Emphasis is placed on the source of loading and the corresponding response of soil resistance.
The paper also how soil investigation for offshore windfarms differ from oil and gas and economic procedures for carrying out such investigation.
Foundation design of offshore structures requires identifying the critical loads. In the case of oil and gas foundations, the source of the load is the wind or wave or a combination of both. For offshore wind towers on fixed foundations, an additional source of dynamic load is the turbine blade rotation during operation. The frequencies of the rotor revolution and that of the blade passing the tower, need to be checked in relation to the resonance frequency of the foundation. The foundation dynamic response therefore depends largely on the stiffness and dampening characteristics.
Most offshore wind turbines tend to be located in relatively shallow water depth where difficult multi-layered soils tend to be dominate. This paper also discussion installation suction buckets of fixed foundation in difficult multi-layered soils.
