An integrated production complex includes a gravity-based structure (GBS) accommodating topside modules with process equipment. The GBS has rectangular top and base slabs, an intermediate horizontal slab, internal vertical walls, at least one compartment with a tank to store hydrocarbons and/or respective processed products, and ballast compartments. The top slab has supports, on which the topside modules are installed. The GBS has a rectangular prism central part including the top slab, and a protruding part disposed along the sides of the central part around its entire perimeter and having external vertical walls. Protruding and central parts share the base slab, with the protruding part height less than the central part. The central part has longitudinal and transverse walls forming compartments for tanks and ballast compartments. The protruding part has internal walls that are perpendicular to its external walls and form compartments, some of which are ballast compartments.

A perforated structure mountable onto a seabed for establishing a deep-water port or an artificial island comprises: a plurality prefabricated perforated modules integratable into said structure; and at least one connector interconnecting corner portions of said prefabricated perforated modules. Each prefabricated perforated module has a corner portion comprising a concave surface such that said corner portions being integrated together into said structure form a cavity to be filled with a concrete. The connector comprises a crosspiece having three arms orthogonal to each other; each arm has a cross-like cross section. The crosspiece has reinforcing members at least partially mechanically connectable to said corner portions.

An apparatus for installation and protection of subsea cables comprises at least a first tubular member (1) and at least a second tubular member (2). Both these are arranged to be installed subsea with a subsea foundation (3). This allows passage of cable (29) through it. The first tubular member (1) is arranged telescopically within the second tubular member (2) so as to extract outwardly towards seabed (5) from an end portion (7), with respect to the second tubular member (2), only up to a prefixed length. This ensures that a continuous conduit for the cable is obtained through the scour protection of the foundation (3). The present invention also includes a methodology for installation of the apparatus and a method for installing a cable through the scour protection of the foundation, by using the apparatus.

A gravity-based structure (GBS) includes central and protruding parts having a common base slab. For the central part, outer and inner walls and a top slab are cast in concrete so that the GBS forms a rectangular prism. As casting of individual outer wall sections is completed, a reinforcement cage is assembled, formwork is installed, and protruding part outer and inner walls are cast, the outer walls being formed along the base slab perimeter with a height lower than the central part outer wall height. As separate protruding part wall sections are cast, a reinforcing cage is assembled, formwork is installed for a protruding part top slab, and then cast. Post-tensioning of central part base and top slabs and central and protruding part outer and inner walls is done as central and protruding part top slab casting is completed and the concrete is cured, increasing buoyancy and reducing submersion.

A transition piece for use in a foundation of an offshore wind turbine including a tubular concrete support structure for supporting the wind turbine. The concrete support structure has a first end arranged to receive an end portion of a pile for mounting the transition piece on the pile and a second end distal from the first end for supporting the wind turbine. The transition piece may form part of the foundation for the offshore wind turbine in which the transition piece is mounted on the end of the pile extending from the sea floor. The end of the pile on which the transition piece is mounted is below the surface of the water and the transition piece protrudes above the surface of the water such that the wind turbine may be mounted thereon.

In the assembly of an offshore support structure for a wind turbine, tubular braces are interconnected or connected to a tower support in casted connections where an end part of the corresponding brace is inserted into a cavity of a concrete-casted shell unit that is fixed onto the outer surface of the inter-connecting brace or on the outer surface of the tower support, and the volume in the cavity is filled by a hardening fixation material, typically grout, after insertion of the corresponding brace.

An offshore wind energy system comprising a foundation having a first hollow structural element with a longitudinally extending, circumferential first wall. A cable bushing penetrates through the first wall and is arranged in the first wall. At least one cable guide arrangement extends in a radial direction and is arranged at an outer shell surface of the first wall of the first hollow structural element. The cable guide arrangement is configured to guide a submarine cable exiting the cable bushing from the cable bushing to a submarine bottom surface.