Classifications

• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02D—FOUNDATIONS; EXCAVATIONS; EMBANKMENTS; UNDERGROUND OR UNDERWATER STRUCTURES
  • E02D27/00—Foundations as substructures
  • E02D27/32—Foundations for special purposes
  • E02D27/52—Submerged foundations, i.e. submerged in open water
• • E—FIXED CONSTRUCTIONS
  • E02—HYDRAULIC ENGINEERING; FOUNDATIONS; SOIL SHIFTING
  • E02B—HYDRAULIC ENGINEERING
  • E02B17/00—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor
  • E02B17/02—Artificial islands mounted on piles or like supports, e.g. platforms on raisable legs or offshore constructions; Construction methods therefor placed by lowering the supporting construction to the bottom, e.g. with subsequent fixing thereto
  • E02B17/025—Reinforced concrete structures

Definitions

• the invention relates to the foundation for a marine building structure. More specifically, yet not exclusively, the invention relates to a pre- stressed foundation to support off-shore marine structures such as wind power generators.
• Patent No. 4,304,506 published on December 8, 1981 which describes a marine structure that has a base and foundation means projecting itself deep in the base to set itself in a deep marine bed, the foundation comprising a system of walls with means to hold it in both sides of the wall.
• U. S. Patent Application Publication No. US-2009/0191004 A1 describes a design method and construction of a cubic formed marine foundation structure.
• the method consists in: a first stage of a design phase and the second stage of an installation phase.
• design parameters are given relative to the weights set on the foundation structure, the profile of the grounds over its installation location, allowable tolerances in installation, what parameters utilized to calculate the minimum diameter and longitude of the cube's borders.
• the size of the cube is utilized to simulate load situations and penetration in the foundation terrain.
• Said foundation as the majority of the foundations of the prior art, relates to marine currents and therefore are designed to resist these currents.
• the pre-stressed (post-tensioned) concrete marine foundation of the invention due to its structural design and combination of materials of which it is made, provide a stronger resistance, durability and support than those concrete and steel marine foundations of the prior art.
• An object of the invention then is to provide a ring-shaped or annular pre-stressed concrete marine foundation structure.
• Another object of the invention comprises providing a marine foundation that resists marine currents.
• Another object of the invention is for the pre-stressed concrete marine foundation to offer a stronger resistance, settling, support to mount and/or place or mount different structural elements.
• the invention overcomes the drawbacks of the prior art, by providing a pre-stressed concrete marine foundation.
• a pre-stressed concrete marine foundation (10) comprising a concrete base (11) that is placed over the sea bed and that has a frusto-conical shape, with an inferior face that has a diameter D1 and an upper face that has a diameter D2, the diameter D1 being greater than the diameter of D2; a ring- shaped body (12) of triangular cross section, joined at the concrete base (1 1) over the upper face of diameter D2, the ring-shaped body (12) comprising a structure of alternated closed sections (13) and open sections (14), the closed sections (13) comprising a plurality of pre-stressed concrete columns (13a, 13b and 13c), each formed of vertically piled concrete segments; and the open sections (14) comprising beam frames (14a, 14b and 14c) spaced in between, wherein each frame comprises a plurality of structure beams 140, and wherein
• Figure 1 shows a perspective view of the pre-stressed concrete marine foundation in accordance with an embodiment of the invention.
• Figure 2 shows an elevated lateral view of the pre-stressed concrete marine foundation in accordance with the embodiment of the invention.
• Figure 3 shows an upper view of the pre-stressed concrete marine foundation in accordance with the embodiment of the invention.
• Figure 4 shows a lower view of the foundation.
• Figure 5 shows a view of a concrete segment.
• Figure 6 shows a view of the joint of the column with the beam frame.
• the pre-stressed concrete marine foundation 10 is a ring- shaped reinforced and post-tensioned concrete structure in combination with a framework of beams.
• the pre-stressed concrete marine foundation is design to support loads to which it is subject, such as the weight of the load, the movement of the waves and/or seismic events.
• the base comprises a body of frusto-conical shape, having a determined thickness.
• Base 11 has a diameter D1 that is reduced gradually to a diameter D2 from which rises a body 12 of the foundation.
• Diameter D1 of the base is greater that the diameter of the body, whilst diameters D2 of the base and the diameter of the body are substantially the same.
• the amplitude of the base provides stability to foundation 10 against frontal loads resulting from waves and marine currents.
• the shaped section of the base provides a surface 1 16 that has a slope, and said surface 116 has a double purpose:
• the slope of said surface has the purpose of deflecting upward the water currents that it faces, thus reducing the risk of horizontal displacement of the foundation; and
• surface 116 that is pressed by the weight of the water over this surface. Said weight assists in keeping the base on the marine bed, and counteracts the inertial moment that is caused by the superficial marine currents that tend to overturn the foundation.
• the surface of diameter D2 of base 11 preferably includes a step 118 that serves as a guide for the placement of the columns and frames of body 12.
• the base incorporates the necessary means to allow pre- stressing of concrete columns 14 of body 12 with base 11 , such that the base and the columns works as a monolithic structure.
• Foundation 10 of the invention comprises a base 11 , a body 12 and a platform 15 that are built and assembled in a wharf or at the coast and is taken assembled to the site where the construction will be set.
• the marine bed is cleaned and leveled, thereafter the foundation of the invention is sunk and set.
• the leveling of the terrain can be carried out by known methods in this matter, for example, with rocks.
• the marine foundation is equipped with a net of horizontal and vertical pipes, interconnected and embedded within the concrete base 1 , including nozzles in their ends for injecting a pressurized water jet to remove the sand under the footing and clean the marine bed. Such pressurized water jet is produced whilst the marine foundation of the invention is being sunk.
• base 1 1 has an aperture 117. Said aperture facilitates the sinking of the structure. In addition, the aperture permits the anchoring of the structure on the marine bed. Once the foundation has been place, concrete is strained over the base and the aperture to form a concrete layer thus providing an additional weight to the foundation 10 to ensure it does not move.
• the tower of the invention is composed of a body 12, whose purpose is to support a platform 15 that is placed above the sea level.
• body 12 is formed by three closed sections 13 -that comprise alternated reinforced and pre-stressed concrete columns (13a, 13b and 13c)-, with three open sections 14 -comprising beam frames (14a, 14b and 14c)-, that in combination form an annular structure, this is the body 12 which is hollow in its center.
• Body 12 as illustrated in the figures, has a transversal triangular section. Notwithstanding, any geometry can be used, that is, the body can comprise more than three columns forming a polygonal body. In addition, in the center of the body other columns could be incorporated. However, the triangular configuration is preferred since this configuration provides the best resistance against the lateral loads produced by the waves and marine currents. In addition, bode 12 of three columns offers a broader surface above base 11 for the circulation of water between the columns.
• polygonal geometric configurations of body 12 that have a larger number of columns are less preferred. Such configuration may provide a better resistance to the flow of marine currents, but results in a less efficient performance and its construction is more expensive.
• Body (12) of the foundation preferably incorporates three pre- stressed concrete columns (13a, 13b and 13c) spaced in between, that extend length and width wise on the marine pre-stressed concrete foundation on the apexes of the triangular transversal section of body 12 joined laterally to the beam frames (14a, 14b and 14c).
• Each pre-stressed concrete column (13a, 13b and 13c) is formed by concrete segments 130 that have a semicircular shape.
• Figure 4 shows a segment of concrete 130.
• segments 130 are explained as having the same dimension and shape, such that they can be fabricated in standardized formworks.
• Segments 130 have the shape of a cylindrical segment that has an arch of approximately 110°.
• Each concrete segment 130 has an external face 132 and an internal face 133 with two lateral faces 134a and 134b of a suitable thickness. These segments also have an upper side 135 and a lower side 136.
• each concrete column 13a, 13b and 13c whose structural properties are similar to one corresponding to a monolithic structure.
• the pre-stressing vertical tendons are introduced and secured by means and methods well known to those persons skilled in the art.
• each concrete column 13a, 13b and 13c comprising four segments.
• the segments are built at the sea coast or at workshops near to the docks and taken to the off-shore construction site.
• each column can be built from more or less concrete segments, the selection of which depends on the design and size of the foundation and construction as well as transport considerations.
• the concrete columns may also be manufactured in any geometry and not only in the shape of semicircular transversal section columns.
• the columns can have a circular, polygonal or triangular transversal section, including one in another shape such as one incorporation various lobes.
• columns 13a, 13b and 13c could be straight or could be shaped such that the upper segments would have a lesser diameter than the lower segments it forms, or could be a "bottle neck” type wherein and for example two lower segments have a greater diameter than the two upper segments in a same column.
• the pre-stressed semicircular concrete columns (closed sections 13) are joined laterally to the beam frames (open sections 14) by means of a union that allows them to work structurally as one unit.
• the body of the pre-stressed marine foundation (10) is preferably composed of three beam frames (14a, 14b and 14c) forming three sections named jointly open sections 14. Each of these frames comprises a plurality of structured beams 140.
• the beams 140 can be manufactured in steel or in concrete.
• the concrete beams have a better result when faced with the corrosion of sea water, while steel beams have an elasticity module that renders a better performance when faced with the efforts of traction and compression of water current and at the inertial moment generated by the structure when placed over the foundation, for example, an eolic generator that is exposed to the wind strain.
• beams can be pre-assembled sections, such as beam panels that are connected to the concrete segments as these are being placed.
• a steel metallic frame In the event of a steel metallic frame, it is assembled by welding and/or bolts and/or screws with or without reinforcement elements. As shown in Figure 6, preferably, it is joined by means of a welding of the metallic beams 140 to the reinforcement rods of concrete segments 130 of columns 13a, 13b and 13c, such that each of the segments 130 is joined to the beam frames 14a, 14 and 14c.
• the beams 140 can be structured of any well known manner to form a determined arrangement, for example, as a honeycomb structure or an included beam structure, while each element is joined to the upper module and/or lower adjacent module.
• the beams may also include internal ducts, to allow the introduction of horizontal or diagonal pre-stressing tendons, such that a same horizontal or diagonal pre-stressing tendon may hold the concrete segments as well as the beams.
• the beam frames have as purpose the structural support of the pre-stressed marine foundation and of joining the pre-stressed semicircular cement segments while it permits the flow of water through it.
• the concrete base 11 , and the body 12, comprising concrete segments 130 and beams 140, are assembled on a sea barge in the dock, and then transported the erection site, and finally sunk in the erection site.
• the body 12 of the marine foundation structure is placed and post-tensioned in site, then it is placed over the same one concrete platform 15, preferably of a circular form, that serves as a base for other structure, for example, a petroleum platform or an eolic generator, in particular, a pre-stressed concrete tower for a wind power generator.
• platform 15 comprises an upper circular concrete base that as a determined thickness. As shown in the figures, the diameter of platform 15 is greater than the diameter of body 12, and has accessories and protrusions necessary to support an installation. If the installation is a concrete tower for eolic generators, this includes means to anchor said tower to the foundation.
• the lower face could include means such as a step or grooves so that the platform may adapt to body 12 of the foundation.
• Said platform can also include ducts to introduce pre-stressing cables such that base 1 1 , body 12 and platform 15 are joined by means of pre-stressing cables and the whole structure functions as a monolithic structure.
• the pre-stressed concrete foundation is capable of supporting large forces in a lateral direction without collapsing, without inclining and without significant structural damages. Also, corrosion has a lesser effect on the concrete structure.
• the pre-stressed marine concrete foundation (10) is designed to operate in areas subject to seismic activity, the advantage and benefit shall be that of enduring principally two types of environmental forces. These are: the forces due to waves and the forces imposed over the base due to earthquakes.
• the referenced design to the body of the pre-stressed marine concrete foundation, particularly to the straight metallic frames (14a, 14b and 14c) upon existing a space between the beams 140 that form said spaces without impacting directly on the pre-stressed marine concrete foundation shall result in the structure not being weakened by the forces derived from waves and thereby the life span of said pre-stressed marine concrete foundation shall be greater than the foundations of the prior art.
• the marine foundation has a height between 10 -30 meters from the sea bed.
• ROCK BED COVERED BY A THIN LAYER OF SAND The foundation will be lowered to the sand bed level and a water pump from the barge will inject pressurized water through the pipe system to disperse the sand and lower the foundation to the rock bed. At this time, stone wedges are used to level the foundation (plumb). A trompe is lowered to the center bottom of the base 1 1 and concrete is pumped to fill all the opening 117 of the base. The amount of concrete can be as much as needed to use it as a bottom weight necessary to stand the forces created by the tower and/or other causes.
• IRREGULAR SOIL Such types of soils need stone to support the foundation. The process stands lowering the foundation in the marine bed and casting concrete in the opening 117 of the base, as mentioned before.
• the concrete base can be prepared with perforations to drill through micro piles anchored in deeper rock beds.
• the body of the foundation could include concrete blocks places between the concrete columns.
• the platform could be built in steel and it could not be held by pre-stressing to body 12 of the foundation 10. Said modifications are understood not to differ from the spirit and reach of the invention, and all those obvious modifications to one with ordinary skills in the pertinent art, are included within the reach of the claims.
• D1 greater diameter of the base.

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• 2011
  • 2011-06-10 EP EP11792010.8A patent/EP2576918A4/de not_active Withdrawn
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