A floating support structure for supporting a windmill system includes a windmill tower, a windmill nacelle, and windmill blades. The support structure includes an aft main section, a transverse main section, and a connecting flange. The aft main section includes a horizontal aft part with a first horizontal aft end and a second horizontal aft end, a vertical aft part with a first vertical aft end at least indirectly connected perpendicular to the first horizontal aft end and a second vertical aft end, and an aft damping structure connected to the second vertical aft end. The vertical and the horizontal aft parts are oriented in a common vertical aft plane. A horizontal cross sectional area of the aft damping structure is larger than a horizontal cross-sectional area of the second vertical aft end. The transverse main section includes a horizontal transverse part with a first horizontal transverse end and a second horizontal transverse end, two vertical transverse parts, each having a first vertical transverse end and a second vertical transverse end, wherein the first vertical transverse ends of the vertical transverse parts are at least indirectly connected perpendicular to the first and second horizontal transverse ends, and two transverse damping structures connected to the second vertical transverse ends of the respective two vertical transverse parts. The two vertical transverse parts and the horizontal transverse part are oriented in a common vertical transverse plane. A horizontal cross sectional area of each of the transverse damping structures is larger than a horizontal cross sectional area of the second vertical transverse end. The connecting flange is for connecting a coupling end of the windmill tower distal to the windmill nacelle vertically onto the floating support structure. The second horizontal aft end of the aft main section is connected to the horizontal transverse part of the transverse main section such that the vertical aft plane is oriented perpendicular to the vertical transverse plane.

A method and system for tensioning a hyperstatic system involves two structures connected to each other, including: a) connecting, by at least one non-adjustable tendon and at least one adjustable tendon which is formed by a tendon coupled to a cylinder in an initially retracted position, an upper structure to a lower structure which is positioned below the upper structure while maintaining zero tension in the tendons; step b) applying a force to the upper structure and/or the lower structure in order to tension each adjustable tendon and to deploy the respective cylinder thereof, the tension of each non-adjustable tendon remaining at zero; and step c) progressively increasing the force until the tension of each non-adjustable tendon reaches a threshold value which brings about a load transfer from the lower structure to the upper structure to allow the lower structure to be supported by the upper structure.

A method and system for tensioning a hyperstatic system involves two structures connected to each other, including: a) connecting, by at least one non-adjustable tendon and at least one adjustable tendon which is formed by a tendon coupled to a cylinder in an initially retracted position, an upper structure to a lower structure which is positioned below the upper structure while maintaining zero tension in the tendons; step b) applying a force to the upper structure and/or the lower structure in order to tension each adjustable tendon and to deploy the respective cylinder thereof, the tension of each non-adjustable tendon remaining at zero; and step c) progressively increasing the force until the tension of each non-adjustable tendon reaches a threshold value which brings about a load transfer from the lower structure to the upper structure to allow the lower structure to be supported by the upper structure.

A method for constructing a floater for a floatable wind energy power plant includes providing a first pre-assembled part with at least one first connection arrangement, providing a second pre-assembled part with at least one second connection arrangement, arranging the at least one first connection arrangement of the first pre-assembled part proximate to the at least one second connection arrangement of the second pre-assembled part so as to form a connection site which includes at least a part of the at least one first connection arrangement and at least a part of the at least one second connection arrangement, sealingly arranging an enclosure about the connection site so as to seal the enclosure against an ingress of water, and connecting the first pre-assembled part and the second pre-assembled part at the connection site. Each of the first pre-assembled part and the second pre-assembled part are floatable.

A method for constructing a floater for a floatable wind energy power plant includes providing a first pre-assembled part with at least one first connection arrangement, providing a second pre-assembled part with at least one second connection arrangement, arranging the at least one first connection arrangement of the first pre-assembled part proximate to the at least one second connection arrangement of the second pre-assembled part so as to form a connection site which includes at least a part of the at least one first connection arrangement and at least a part of the at least one second connection arrangement, sealingly arranging an enclosure about the connection site so as to seal the enclosure against an ingress of water, and connecting the first pre-assembled part and the second pre-assembled part at the connection site. Each of the first pre-assembled part and the second pre-assembled part are floatable.

A method of installing a wind turbine generator onto a floating foundation. The floating foundation has variable buoyancy and is pre-ballasted to float at a predetermined vertical position before installation of a wind turbine generator component onto the floating foundation. A wind turbine generator component supported by lifting equipment is brought towards the floating foundation until contact is made with the floating foundation. Ballast is removed from the floating foundation to increase the buoyancy of the floating foundation such that weight of the wind turbine generator component supported by the floating foundation is increased from substantially zero to substantially the entire weight of the wind turbine generator component. The vertical position of the floating foundation is substantially unchanged during transferring weight of the wind turbine generator component onto the floating foundation.

In a general aspect, suction anchors are presented for securing structures to an underwater floor. The suction anchors include a tubular body formed at least in part of cementitious materials and having a closed end and an open end. The tubular body includes an edge defining an opening for the open end. The edge is configured to penetrate the underwater floor. The suction anchors also include a port configured to fluidly-couple a cavity within the tubular body to an exterior of the tubular body. The suction anchors additionally include a pad eye extending from an outer surface of the tubular body and configured to couple to a mooring line. In another aspect, methods of manufacturing the suction anchors are also presented.

A jack-up platform is described having a horizontal working deck that may be jacked up out of the water by moving its legs to a position wherein they take support on an underwater bottom. The jack-up platform further includes a higher level deck and a lower level deck that define a receiving space for a barge, optionally suitable for carrying parts for construction of a wind turbine, and further a deballasting system configured to bring the floating hull between a receiving position at which the hull is ballasted to a receiving draft in which the lower level deck is submerged underwater and the barge may be received in the receiving space through an opening in the hull, and an operational smaller draft where substantially no water can flow on either of the lower and higher level decks. The receiving space has a centralizing system configured to substantially centralize the received floating barge in the receiving space. A method for facilitating the offshore installation of a wind turbine using the jack-up platform is also described.

System for transporting an offshore structure, the system comprising: a transport apparatus, in particular a vessel or a vehicle, which is configured to receive an offshore structure and to form a slip joint with a slip joint section of a received offshore structure, wherein the system is configured to enter a releasable state, from a fixing state, wherein, in the releasable state, the slip joint formed by the transport apparatus and the offshore structure is smaller than that force in the fixing state.

System for transporting an offshore structure, the system comprising: a transport apparatus, in particular a vessel or a vehicle, which is configured to receive an offshore structure and to form a slip joint with a slip joint section of a received offshore structure, wherein the system is configured to enter a releasable state, from a fixing state, wherein, in the releasable state, the slip joint formed by the transport apparatus and the offshore structure is smaller than that force in the fixing state.