Title of Invention: VERTICAL STRUCTURE FOR SUPPORTING

LOADS

Technical Field

[1] This invention relates to vertical structures for supporting loads, more particularly to vertical structures such as towers or the like utilized for wind turbine generators, electric power transmission lines, telecommunications, and other applications.

Background Art

[2] Vertical structures for supporting loads such as towers or the like utilized for

supporting wind turbine generators , power transmission lines, telecommunications, and other applications are well know in the prior art. The structural designs, components and materials of such vertical structures vary depending upon the application.

[3] One type of vertical structure that has been receiving special attention in the last decades are the vertical structures for wind turbine generators or other heavy loads.

[4] Wind energy has become a very attractive source of energy, both due to an increase in efficiency of the generators and an increase in market demand for clean and renewable sources of energy.

[5] The increase of the efficiency of the wind energy generators is related to a great effort in enhancing several aspects of the technology, including many issues related to the design and manufacturing of the wind energy generator components including, among others, the rotor blades, the electrical generator, the tower and the control systems.

[6] One of the factors related with the increase in efficiency is the increase of the height of the towers and the increase of the aspect ratio of the rotor blades; however, the increase of aspect ratio of the rotor blades usually involves heavier and larger rotors and the increase of the height of the tower may involve the use of additional material, for instance, steel, for manufacturing the tower.

[7] Hence, as a tower usually represents about fifteen to thirty percent of the cost of the wind energy generator, there is a great need to obtain higher and more robust towers at lower costs.

[8] Most large wind turbines manufactured in the last two decades with a power output higher than one megawatt adopt tubular steel towers, commonly referred to as 'monopoles', as the preferred choice. The monopoles usually tapper from the base to the top or close to the top, having sections connected together with bolted flanges. A restriction related with monopoles are the road transportation limitations that restrict the diameter of the segments. For instance, tubular segments with diameters higher than about 4 meters (about 13.12 feet) may not be transported on roads in many countries.

[9] Lattice towers usually need less material (e.g. less steel) than monopoles, but require a higher number of components and bolted connections. These bolted connections are subject to the varying fatigue loads, hence, they have the disadvantage of higher maintenance needs.

[10] There are many attempts in the prior art that try to address these issues, such as the Patent Applications US 2007/0095008 A 1 (ARSENE) and US 2009/0249707 A 1 (CURME).

Disclosure of Invention

Technical Problem

[11] One particular technical problem regarding vertical structures such as towers or the like utilized for supporting heavy loads such as large wind turbine generators, including the prior art documents cited herein, is the lack of compromise between the stress and strain distribution of the vertical and horizontal loads vectors along the extension of the vertical structure. Due to this lack of compromise, the tower segments are designed with significant losses of materials in some segments or with assemblies that result in complex manufacturing, transportation and installations requirements. Technical Solution

[12] To overcome the drawbacks and problems described above and other disadvantages not mentioned herein, in accordance with the purposes of the invention, as described henceforth, one basic aspect of the present invention is directed to a vertical structure for supporting loads comprising three oblique frustoconical metallic legs arranged in a triangular transversal section configuration; and a plurality of bracing members interconnecting the legs.

Advantageous Effets

[13] The present invention has several advantages over the prior art. In comparison with the vertical structures of the prior art, the present invention enables a surprising reduction in the weight of the structure of about 30%, reaching, in some cases, more than 60%, depending on the design requirements of the case. One of the reasons for such expressive reduction in the total weight of the structure is that each leg of the vertical structure has a stress and strain behavior similar to a monopole, without having the restrictions of the large diameter of the single monopole vertical structures.

[14] The advantage of weight reduction is accompanied by further manufacturing, transportation and installation advantages, as well as availability of a new class of vertical structures for heavy and critical applications, such as wind energy turbines with a power output higher than 3 MW with towers higher than 100 meters (higher than 328 feet).

Description Of Drawings

[15] The accompanying drawings are not necessarily drawn on scale. In the drawings, some identical or nearly identical components that are illustrated in various figures may be represented by a corresponding numeral. For purposes of clarity, not every component may be labeled in every drawing.

[16] Fig.Ol illustrates a perspective view of one exemplary vertical structure according to one embodiment of this invention.

[17] Fig.02 illustrates a top view of one exemplary vertical structure according to one embodiment of this invention.

[18] Fig.03 illustrates a side view of two legs of one exemplary vertical structure

according to one embodiment of this invention.

[19] Fig.04 illustrates a side view of two legs of one exemplary vertical structure

according to one embodiment of this invention.

Mode for Invention

[20] This invention is not limited in its application to the details of construction and the arrangement of components set forth in the following description or illustrated in the drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. Also, the phraseology and terminology used herein is for the purpose of description and should not be regarded as limiting. The use of 'including', 'comprising', 'having', 'containing' or 'involving', and variations thereof herein, is meant to encompass the items listed thereafter and equivalents thereof as well as additional items.

[21] Fig.Ol illustrates a perspective view of one exemplary vertical structure according to one embodiment of this invention. In the example shown in Fig.Ol, which is on an approximate scale, the vertical structure (101) for supporting loads comprises three oblique frustoconical metallic legs (102, 103, 104) arranged in a triangular transversal section configuration; and a plurality of bracing members (105) interconnecting the legs (102, 103, 104).

[22] The legs are preferentially manufactured with a metallic material and formed in substantially hollow frustoconical oblique shells, adopting outside diameter to thickness (D/t) ratios preferentially between 30 and 150. The legs shells may be fabricated by forming a rolled pipe, resulting in an essentially circumferential perimeter. Alternatively, the legs may be manufactured with folding metallic plates, for example, using cold or hot bending processes, and welding together the lateral ends, resulting in an essentially multi-sided polygonal cross-sectional area, with any suitable number of sides. The legs may also have an essentially oblong or elliptical shape cross-section, provided that the oblique frustoconical shape is kept.

[23] It is to be understood that the oblique frustoconical shape of the leg may be alternatively obtained by manufacturing a right frustoconical leg, which is inclined during installation in order to obtain the oblique frustoconical shape of the leg. This solution may be advantageous due to manufacturing issues, such as limitations in some machinery that fabricates only right cones.

[24] Legs may be fabricated by any suitable metallic material, for instance, steel. A high strength low-alloy structural steel, with yield strength higher than 370 MPa, is preferred. The legs may include composite materials. For instance, the legs metal shells may be internally reinforced by ceramics, fibers and any other suitable material. Alternatively, as the legs are hollow shells, they may be filled with any suitable material, whether for reinforcing the structure or providing a damping effect for reducing the stresses over the foundation. For example, the legs may be filled with concrete for reinforcing the structure. As the vertical structures for the preferred applications, such as multi-megawatt wind energy generators, are usually very high, for instance higher than 70 meters (higher than 230 feet), or even higher than 120 meters (higher than 394 feet), each leg will usually be fabricated in separated segments that are joined together during installation on the site.

[25] In the embodiment shown in Fig.01, the bracing members (105) include a plurality of diagonals (106) and beams (107). The number, type, dimensions and geometry of the bracing members will depend on the particular application and case. In some cases, the beams or the diagonals may not be necessary. In some cases, the beams and/or the diagonal members may have similar dimensions and geometry for the entire vertical structure, which results in significant efficiency gains in the manufacturing of the bracing members.

[26] The diagonals and beams may have any available standard or special section

(profile), such as an angle section, channel sections, tubular or conical sections, among others. For instance, the bracing members may have a conical section with varying D/t ratio.

[27] The bracing members may be constituted by metallic materials, composite materials or combinations thereof. For instance, a tubular diagonal may be reinforced with a concrete composite. Other sections, including opened sections, may also be reinforced with composite materials.

[28] Fig.02 illustrates a top view of one exemplary vertical structure according to one embodiment of this invention. As shown in this figure, the vertical structure (101) for supporting loads includes a central longitudinal axis (111) defined along the length of the vertical structure (101). The distance between the central longitudinal axis (111) of the vertical structure (101) and the central axis (122, 123, 124) of each leg (102, 103, 104) on the base of the vertical structure (101) is substantially the same. The distance between the central longitudinal axis (111) of the vertical structure (101) and the central axis (132, 133, 134) of each leg on the top of the vertical structure (101) is substantially the same. Furthermore, in the example shown in Fig. 02, the central axes (122, 132; 123, 133; 124, 134) of the legs (102, 103, 104) are inclined towards the central longitudinal axis (111) of the vertical structure (101) at substantially equal angles.

[29] The moment of inertia of each leg (102, 103, 104) in at least one segment of the

vertical structure (101) is preferentially substantially higher than the moment of inertia of the bracing members (105) that interconnect the corresponding legs (102, 103, 104) of this segment. Preferentially, the moment of inertia of each leg (102, 103, 114) along the length of the vertical structure varies between approximately 35 times in the top of the structure and 600 times at the bottom of the structure in relation to the moment of inertia of the bracing members (105) that interconnect the legs (102, 103, 104).

[30] In the example shown in Fig.03, the central axes (222, 232; 223, 233) of the legs (212, 213) are inclined towards the central longitudinal axis (211) of the vertical structure (201) and the internal generatrices (218, 219) of the legs (212, 213) are in a right angle in relation to the base plane of the legs (213, 213). In this example, the third leg is not shown in the figure for purposes of clarity.

[31] In the example shown in Fig.04, the central axes (322, 332; 323, 333) of the legs

(312, 313) are inclined in the opposite direction to the central longitudinal axis (311) of the vertical structure (301) and the external generatrices (318, 319) of the legs (312, 313) are in a right angle in relation to the base plane of the legs (312, 313). In this example, the third leg is not shown in the figure for purposes of clarity.

[32] The vertical structure may be specifically configured to support a wind turbine.

Based on this specification, a person skilled in the art would be able to define particular and/or additional components and/or accessories that may be suitable for each type of wind turbine. For instance, the design of the wind turbine nacelle may require a specially designed transition piece between the top of the tower and the base of the nacelle.

[33] In the case of power transmission lines, a person skilled in the art would be able to define particular braces for supporting the lines.

[34] The vertical structure may be used in combination with additional structures, for instance, at least one additional vertical structure arranged in a portico configuration. For example, this portico configuration may be useful for test base stations.

[35] While the invention has been disclosed by this specification, including its accompanying drawings and examples, various equivalents, modifications and im- provements will be apparent to the person skilled in the art. Such equivalents, modifications and improvements are also intended to be encompassed by the following claims.