TRANSITION ELEMENT FOR THE TRANSMISSION OF STRAINS BETWEEN A TOWER AND A SUB-STRUCTURE ON A FLOATING MONOLITHIC CONCRETE STRUCTURE FOR SUPPORTING MARINE WIND TURBINES

Abstract

The invention relates to the embodiment, by means of a pre-stressed concrete layer, on floating structures for supporting wind turbines, of the transition zone between the tower, of a lesser diameter, and the concrete float, of a greater diameter, whether the tower is made of metal or concrete. Said layer of revolution has the optimum geometry for the correct transmission of forces between the two parts, the tower and the float, with a reduced thickness and without the need for external rigidifying and reinforcing elements on the surfaces thereof, which would increase the weight and the cost of the structure.

Claims

1. A concrete transition element between an underwater sub-structure and a tower of floating structures for supporting marine wind-driven power generators, wherein the underwater sub-structure is made of hollow concrete, characterized by comprising a pre-stressed concrete revolution layer having an axisymmetric circular transition geometry from the radius of the float to the radius of the base of the tower, said pre-stressed concrete revolution layer having a thickness comprised between a thickness of the tower and a thickness of the sub-structure, dispensing with reinforcements or stiffeners on outer surfaces thereof.

2. The sub-structure/tower concrete transition element according to claim 1, wherein a surface of the pre-stressed concrete revolution layer transition is tangent to a generatrix of the base of the tower.

3. The sub-structure/tower concrete transition element according to claim 1, wherein said axisymmetric circular transition geometry is adjusted by means of two or more straight segments providing two or more frustoconical segments in the pre-stressed concrete revolution layer.

4. The sub-structure/tower concrete transition element according to claim 1, wherein said pre-stressed concrete revolution layer transition comprises: longitudinal steel prestressing tendons; and circumferential steel prestressing tendons.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a schematic elevational view of a floating structure for supporting marine wind turbines, where the location of the transition part according to the present invention is highlighted;

[0013] FIG. 2 is an elevational section view of the transition part, showing the either curved geometry or segmented geometry of the transition defining the transition length L depending on the radii of the tower and the float. Longitudinal steel prestressing tendons, as well as the main circumferential tendons handling the strains existing due to the change in geometry, can be seen. The circumferential reinforcement tendons distributed along the transition are also shown. Furthermore, it can be seen that the inner space is completely free of stiffening and/or reinforcing elements.

[0014] FIG. 3 shows a plan view of the transition, wherein the geometry of the circumferential prestressing tendons and of the longitudinal tendons providing continuity to those coming from the tower can be clearly seen.

DESCRIPTION OF THE INVENTION

[0015] By means of using a suitable geometry and steel tendons for longitudinal and circumferential prestressing, a smooth transmission of the strains generated in the tower to the float is achieved. It additionally helps improve other hydrodynamic aspects with respect to other solutions, as will be seen below.

[0016] Said transition comprises: [0017] an arc of circumference tangent to the generatrix of the tower joining both parts together, forming a toroid-shaped transition.

[0018] Should it be needed, the transition can be done in two or more frustoconical segments by adapting the transitions to the original curvature. This option involves higher concentrations of stresses, which can in turn be absorbed by means of the concentrated circumferential prestressing in each transition change.

[0019] By adopting this geometry, which is either torus-shaped or based on cone frustums, suitable distribution of the longitudinal and transverse stresses on the concrete is obtained, including the loads of the tower plus those loads due to the prestressing of the tendons embedded in the concrete, whether they are longitudinal or transverse.

[0020] The meeting point of the float and the transition is circumferentially pre-stressed to absorb the stresses generated by the change in geometry, by providing a set of tendons clustered in the zone where the change is located, and other reinforcing tendons distributed throughout the transition to assure a full state of compression.

[0021] This state of compression assures durability of the floating structure throughout the entire underwater body and splash zone.

[0022] The longitudinal tendons correspond to the existing prestressing tendons at the base of the tower, providing them with continuity to the float through the transition. In the case of towers made of metal, the longitudinal tendons start from the beginning of the concrete structure above the msl.

[0023] In addition to the structural advantage, it must be observed that the transition increases the radius in a non-linear manner such that it allows moving larger diameters away from the surface of the sea, where the effects of the waves are maximal and decrease exponentially with depth, while they proportionally increase with diameter. This greatly improves the hydrodynamic response of the structure, being more permeable on the surface of the sea.

[0024] The transition shape also helps to prevent possible adverse effects in movement under severe wave conditions, where a significant part of the transition is temporarily exposed, causing significant variations to hydrostatic rigidity with the use of typical linear transitions, which must be compensated for in the design by means of the length of the transition, increasing the depth and/or radius of the float.

[0025] Furthermore, the smooth transition at the tower base allows for a greater radius around the tower with minimal depth than by means of other types transitions, which favors the passage of ships.