MX2007009456A

MX2007009456A - Pre-stressed concrete tower for wind power generators.

Info

Publication number: MX2007009456A
Application number: MX2007009456A
Authority: MX
Inventors: Alejandro Cortina Cordero
Original assignee: Alejandro Cortina Cordero
Priority date: 2007-08-03
Filing date: 2007-08-03
Publication date: 2009-02-02

Abstract

This application relates to a pre-stressed concrete tower for wind-power generators, which is characterised in that it comprises a foundation and a mixed structure (concrete and steel) having a triangular transversal section, this latter section including (a) a metallic shield (30) with three spaced straight sections (31, 32, 33) located at the flat surfaces of the mixed structure that has a round edge triangular transversal section, the straight sections being extended lengthwise the tower, the metallic shield comprising a plurality of structured metallic beams (35); and (b) a concrete structure (20) that consists of three concrete sections (21, 22, 23) located at the edge portions of the mixed structure, said concrete sections including a plurality of circular segments (25) manufactured out of reinforced concrete, which are vertically stacked and attached together, arranged between the straight portions (31, 32, 33) of the metallic shield (30) and joined together and to the foundati on by means of prestressing elements.

Description

CONCRETE TOWER POSTENSED FOR WIND GENERATORS BACKGROUND. 1. Field of the invention. This description refers to post-tensioned concrete towers. In particular, it refers to the construction of segmented concrete towers post-tensioned to support wind generators. More particularly, the invention relates to a mixed structure of reinforced and post-tensioned concrete in combination with a steel structure. 2. General background of the invention. Different towers for wind generators have been proposed. For example, various towers have been constructed with reinforced metal structures consisting of a plurality of crosspieces and metal poles. In addition, tubular steel structures have been constructed for the same purposes. Said structures have several drawbacks, the main one of said drawbacks being the permissible height limitation and the cost of the steel. Because wind generators offer a resistance to wind currents, significant vertical and horizontal loads are generated that produce torsion of the structures. In some cases, these metal structures collapse due to the wind and the weight of the generators.

Concrete towers are also known in the prior art. US Patent 2,826,800 refers to segments that include tensioners to form columns and other structures.

In addition, the German utility model DE 29809541 U describes a segmented tower of post-tensioned concrete for wind generators. According to this publication, frustoconical concrete segments are manufactured that subsequently they are mounted. According to this publication, it is possible to mount towers of two hundred meters or more.

For its part, the publication of the international patent application No. WO2004007955 also describes a system for building segmented towers. This publication describes the use of molds to manufacture each concrete segment of the tower in a workshop. Before casting the concrete, tubular ducts that are immersed in the concrete are introduced into the mold, through which the tensors are subsequently introduced - the tubes.

The segmented concrete tower systems described above have several drawbacks. According to this construction technique, the segments that form the columns are manufactured in some suitable facility for this, and later the segments are transported to the site where the tower is erected. Subsequently, each of the tower segments is mounted by means of a crane. Such transport of the tower segments increases the manufacturing costs of the towers.

The towers are generally tapered. That is, they have a progressive narrowing, such that the base generally has a larger diameter than the upper end of the tower where the electric generator is mounted. Such a characteristic results in the need to build a particular mold to manufacture each frustroconical segment of concrete. The need to produce a mold to manufacture each segment of concrete results in an additional disadvantage of said constructive systems. On the other hand, the adjustment of the cast tubes within said system also results in a problem. Patent WO2002004766 addresses said problem.

In addition, the segments with which the concrete towers are manufactured are very heavy, consequently, the towers must be manufactured with large amounts of concrete to be able to support their own weight. Under the weight of said concrete segments, assembly of them requires heavy equipment, resulting in high construction costs.

SUMMARY OF THE INVENTION A first object of the invention is to provide a mixed tower of post-tensioned concrete and steel Another object of the invention is to provide a tower with better use of the characteristics of the materials, which give the tower adequate resistance to winds and earthquakes.

Another object of the invention is to provide a tower that uses only one type of mold for all the concrete segments used in the tower.

A further object of the invention is to provide an improved method for constructing and assembling a post-tensioned concrete column segmented in the same place where the tower is erected.

Still another object of the invention is to provide a method of construction of a tower that does not require the use of heavy construction equipment.

Still another object of the invention is to provide an improved system for manufacturing and assembling a post-tensioned concrete tower.

The above objects of the invention are achieved by providing a post-tensioned concrete tower for wind generators, characterized in that it comprises a foundation and a mixed structure having a section triangular cross-section of rounded corners composed of (a) a metal reinforcement (30), comprising three spaced apart portions (31, 32, 33), on the flat faces of the mixed structure of triangular cross-section, extending along of the tower, the metallic armor consists of a plurality of metallic beams (35) structured; and (b) a concrete structure (20) consisting of three concrete sections (21, 22, 23) at the vertices of the mixed structure of triangular cross section, consisting of a plurality of segment-circular modules (25) manufactured in reinforced concrete, vertically stacked and joined together, disposed between said straight portions (31, 32, 33) of the metallic reinforcement (30) and linked to the foundation by pre-stressing elements.

BRIEF DESCRIPTION OF THE DRAWINGS By way of example, reference is now made to the accompanying drawings.

FIG. 1 illustrates the post-tensioned concrete tower according to the invention.

FIG. 2 illustrates a top plan view of the tower of the present invention.

FIG. 3 illustrates a side elevational view of the tower according to the invention.

FIG. 4 illustrates a modality of the concrete tower with extension.

DETAILED DESCRIPTION OF THE INVENTION The design and construction of a support tower for a wind energy generation system is described, its original constructive development, designed to perform in a quick, economical and reliable way, a mixed tubular structure of reinforced and post-tensioned concrete in combination with structural steel. The tower has aesthetics and the necessary slenderness to support the loads to which it will be subjected, such as its own weight, the weight of the generator, the weight and movement of the blades, the push of winds and seismic forces.

The height of the structure above the ground level can be variable depending on the type of generator to be used. The geometry of the tower is dimensioned and modulated to meet all the service limit states and ultimate limit states of the various current construction regulations.

According to the present invention, a tower is described comprising a body formed by a mixed structure of reinforced and post-tensioned concrete in combination with structural steel. The section of the tower is variable and decreases depending on its height.

In an embodiment of the invention, there is also described a tower that in elevation has two sections distinguishable by their geometry: a body having a variable cross section from its base to approximately two thirds of its height; and an extension having a constant cylindrical section in its upper part that is approximately one third of the total height of the tower.

As illustrated in FIGS. 1 and 2, the body (12) of the tower (10) has an axisymmetric cross section whose perimeter can be assimilated to a triangle with straight parts (16) and rounded vertices (14), hereinafter referred to as the triangular cross section . The triangular cross-section of the body (12) of the tower (10) decreases as a function of the height of the tower, to form in elevation a tapered structure, that is to say, that it thins as it goes gaining height.

The metal framework (30) of the body (12) consists of a metal structure forming an open core section (reinforcement). The metal framework (30) comprises three spaced-apart straight portions (31, 32, 33) that extend along the tower in the straight part of the triangular cross section, between the vertices and form the flat faces of the tower . Each of the straight portions (31, 32, 33) consists of a plurality of structured beams (35), preferably made of steel.

The mixed structure of the tower (10) includes a concrete structure (20) consisting of three sections of concrete (21, 22, 23), spaced from each other, which extend along the tower at the corners of the tower. triangular cross section between the straight portions (31, 32, 33) of the metal frame (30) and attached thereto. Each of the concrete sections (21, 22, 23) consists of a plurality of segment-circular modules (25) manufactured in reinforced concrete, vertically stacked and post-tensioned.

Thus, in the vertices (14) of the triangular cross section of the tower, the concrete structure (20) is defined, while in the straight parts (16) of the triangular cross section, the metal framework (30) is defined. , which extend along the body (12) of the tower (10).

The decrease of the triangular cross section of the tower (10) is achieved by reducing the dimensions of the beams (35) forming the corresponding straight portions (31, 32, 33) of the metallic reinforcement (30) until the segment modules - Circular (25) converge to become a circular ring. According to FIGS. 1, 2 and 3, the tower also includes a ring (27) that has the function of flange for connection with the wind generator.

The segment-circular modules (25) that form the structure of concrete of the mixed structure, they are prefabricated and mounted on the site. The continuity of the concrete modules (25) is achieved through pre-stress elements, such as cables or prestressing strands that are anchored in the foundation of the tower and are subsequently placed and post-tensioned inside the modules.

Laterally, the segment-circular modules (25) are joined to the metal framework (30) by means of a union that allows them to work structurally as a single section.

According to the present invention, it is provided that the segment -circular modules (25) that make up the concrete structure (20) have the same dimensions and shape. These have the shape of a cylindrical segment of 120 °. In this way, unlike the towers of the prior art, a special mold is not required to manufacture each segment of the tower (10). According to the preferred embodiment of the present invention, only one type of mold is used to manufacture all segment-circular modules (25). As will be evident to a person skilled in the art, not only a physical mold is used, but also a plurality of molds having the same characteristics, ie the same type of mold.

The metal armor is assembled by welding and / or screws, with or without reinforcement elements. So that each and every module (25) is attached to the metal framework. The beams can be structured to form a particular arrangement, for example a honeycomb structure or a structure of inclined beams as shown in the figures. As shown in FIGS. 1, 3 and 4, the beams are inclined and join alternating segment modules -circular (25). In addition each segment-circular module (25) is connected to the adjacent upper and / or lower module.

During the construction of the tower the metal armor is first assembled on the site of the tower. The metal reinforcement then serves to support the prefabricated concrete modules, for this purpose it is enough to use a light crane, it should be mentioned that the weight of the segment-circular modules 25 is approximately 1/6 of the weight of a frustroconical segment of a segment. to tower of the prior art. So its handling is simple.

Optionally the molds can be fastened to the metal framework so that the segment-circular modules (25) are successively cast in their final position.

Once the tower is built and in use, the metal armor provides resistance to vertical and horizontal loads, mainly the loads derived from the movement of the blades, the push of winds and seismic forces. In this way, the metallic reinforcement fulfills a double purpose: to form a support for the placement of the molds and the casting of the segment-circular modules (25) and to provide structural support for the tower during its operation.

The metal hollow core armor (30) allows the passage of air through it and therefore offers a lower resistance to wind currents and is therefore more resistant to wind force. Optionally, closure plates may be included to close the open spaces of the straight portions (31, 32, 33) of the metal framework.

For its part, the concrete structure provides the tower with the necessary strength to support the weight of the generator and the same weight of the tower.

According to one embodiment of the invention, illustrated in FIG. 4, the tower includes an extension (19). Preferably, the extension (19) of the tower consists of a cylindrical portion. The cylindrical portion may consist of a metal tube, a cylindrical concrete section of a single piece, or a cylindrical section of segmented concrete that joins the ring (27). Furthermore, according to the invention, the upper end of the cylindrical extension section includes a ring (28) which serves as a flange for the placement of the wind generator.

Said extension (19) consists of a cylindrical member having a constant diameter up to the maximum height of the tower. The materials used in the design are: reinforced and post-tensioned concrete and / or structural steel. According to a preferred embodiment of the invention, illustrated in FIG. 4, the extension (19) consists of a plurality of cylindrical modules (29) of post-tensioned concrete joined together by means of pre-stressing elements, such as cables or strands that are placed and post-tensioned (embedded) into the walls of the walls. modules (not illustrated).

According to the embodiment of the invention described above, it is provided that the cylindrical modules (29) that make up the extension (19) have the same dimensions. In this way, only one type of mold, cylindrical, is required. As will be apparent to a person skilled in the art, not only a physical mold is used, but a plurality of molds having the same characteristics. According to the present invention, while the tower is being assembled, the cylindrical segments may be being fabricated and, in turn, hoisted by means of a crane, placed and attached to the tower by means of pre-stressing elements, such as cables or strands. which are placed and post-tensioned (ducted) into the walls of the modules in a manner well known to a person skilled in the art.

The molds are conditioned by incorporating the tubes for the post-tensioning and accessories, and later a vertical casting is carried out and they can be unmoulded the next day, so that the molds are used every third day. The number of molds is unlimited and the number of units to be used depends on the size of the work and its construction program.

In accordance with the present invention, a considerably lower number of molds is used than in those used in the construction methods of the chimney-type towers of the prior art.

The molding and casting of the segment-circular modules (25) of concrete and the assembly and assembly of the tower (10) is carried out on the site according to the following process: to. Manufacture of the mold for the manufacture of the modules: Given the precision required for the prefabricated parts, the mold to manufacture the circular sector of concrete is made in the workshop following the design and established tolerances, the mold is preferably manufactured based on profiles, plates and steel sheets and responds to a pre-established modular design according to the height of the tower, in general, the height of the tower is designed in modules whose height varies between 3 and 4 m. b. Manufacture of metal parts: The entire metal structure is enabled in the workshop and transported in ready parts to be assembled on site. That is to say, the segments of beams are cut in the necessary measures, they are drilled for the introduction of screws or bolts, as well as other accessories, such as electrical accessories, reinforcement elements are incorporated, etc. c. Construction of the tower's substructure: The substructure or foundation of the tower is built on the site. This element is made of reinforced concrete and is dimensioned according to the mechanical characteristics of the ground. In general, this element functions as a "pedestal" of the tower and transmits to the ground the reactions of the tower that are produced by seismic and wind stresses. All the inserts and necessary steps are included in this element to later include the prestressing cables that will achieve the continuity of the structure. d. Installation of the metallic structure: The metallic structure is assembled with the appropriate equipment, moving it on the foundation and joining its parts to complete the pyramid formed by its parts. and. Construction of the tower modules: Once the foundation is constructed, the molding, assembly and casting of the segment-circular modules (25) that make up the tower is proceeded. Included within the segment-circular modules (25) are the inserts and connection elements necessary to achieve the union and continuity of the same.

F. Assembly and post-tensioning of the concrete structure of the tower: Once the setting and demolding of the concrete modules is verified, they are assembled with the help of cranes of adequate capacity for this task. The assembly is carried out by raising and superimposing the modules and simultaneously supporting them in the metallic structure and joining them to it by welding, the post-tensioning of the concrete modules (20) is carried out. A part of the post-tensioning is continuous from the foundation and through the entire height of the tower. The joints between modules are based on welded metal connections. The metal framework (30) is mounted on the site by successively ligating a plurality of beams with the circular concrete modules. g. Assembly of the extension (19) of the tower: Since this section of the upper part of the tower is of constant cross section, it can be prefabricated on site if the decision is to make it in post-tensioned concrete and in plan, to later be transported and assembled on the site, in case it was steel. h. Injection and protection of post-tensioning anchors: Finally and after the total post-tensioning of the tower, the injection of the pre-tensioning ducts is carried out.

I force using an epoxy cement based grout with a volume stabilizer. This grout is also continuous over the entire length of the tower and forms part of the system of connection between modules.

The towers for wind generators of the present invention are constructed with greater speed of assembly and with simpler means in comparison with the towers of the prior art. The above advantages result in a tower with quality characteristics similar to the towers of the prior art, but built with lower production costs.

A feature of the invention is that the amount of the materials is used more efficiently. Thanks to the metallic parts that are assembled in the first instance with light equipment, it is possible to obtain the geometry and the resistance necessary to mount the concrete modules Having thus described the invention, it will be obvious that it may be varied in many ways. Such variations should not be considered as departing from the spirit and scope of the invention, and all modifications that are apparent to a person skilled in the art, are considered to be included within the scope of the following claims.

Claims

1. - A post-tensioned concrete tower for wind generators, characterized in that it comprises: a foundation and a mixed structure, anchored to the foundation, having a triangular cross section composed of: (a) a metal framework (30), comprising three straight portions ( 31, 32, 33), on the flat faces of the mixed structure of triangular cross section, extending along the tower, the metal framework consists of a plurality of metal beams (35) structured; and (b) a concrete structure (20) consisting of three concrete sections (21, 22, 23) at the vertices of the mixed structure of triangular cross section, consisting of a plurality of segment-circular modules (25) manufactured in reinforced concrete, vertically stacked and joined together, disposed between said straight portions (31, 32, 33) of the metallic reinforcement (30) and linked to the foundation by pre-stressing elements.

2. - The post-tensioned prefabricated concrete tower according to claim 1, characterized in that the body of the tower has a triangular cross section that is progressively reduced in the direction of the upper end of the tower until the segment-circular modules (25) converge to join with a circular ring (27).

3. - The post-tensioned prefabricated concrete tower according to claim 1, characterized in that the segment-circular modules (25) have the same shape and dimensions.

4. - The post-tensioned prefabricated concrete tower according to claim 1, characterized in that the joining of the segment -circular modules (25) in the concrete sections (21, 22, 23) is achieved through pre-stress elements, which are placed and post-tensioned inside the walls of the modules (25).

5. - The post-tensioned prefabricated concrete tower according to claim 1, characterized in that the beams of the metallic reinforcement are made of steel.

6. - The post-tensioned prefabricated concrete tower according to claim 1, characterized in that it also comprises an extension, on the body of the tower, consisting of a cylindrical portion.

7. - The post-tensioned prefabricated concrete tower according to claim 1, characterized in that the cylindrical portion consists of a plurality of post-tensioned cylindrical concrete modules (29) joined together by means of pre-stressing elements, which are placed and post-tensioned inside the the walls of the modules (29).

8. - A method for manufacturing a post-tensioned prefabricated concrete tower comprising a) providing a metal mold for manufacturing the segment -circular modules (25); b) building on the site a substructure of the tower, including a plurality of pre-stressed cables anchored; c) erecting a metal framework (30) on the substructure; d) molding, assembling and casting a plurality of segment-circular modules (25) of concrete, including the inserts and connection elements necessary to achieve the union and continuity of the adjacent upper and / or lower modules, supported on the metallic reinforcement; e) assembling a plurality of segment-circular modules (25) to form concrete sections (21, 22, 23), joined to the straight portions (31, 32, 33) of the metal frame (30); and f) post-tensioning the concrete sections (21, 22, 23) of the structure of concrete (20).

9. - The method for manufacturing a post-tensioned prefabricated concrete tower according to claim 8, characterized in that it further comprises: g) Injecting an epoxy cement-based slurry with a volume stabilizer into the pre-stress ducts over the entire length of the tower .

10. - The method for manufacturing a post-tensioned prefabricated concrete tower according to claim 8, characterized in that it further comprises: h) mounting a tower extension (19).

11. - The method for manufacturing a post-tensioned prefabricated concrete tower according to claim 10, characterized in that the extension consists of a cylindrical portion selected from a plurality of cylindrical modules (29) of post-tensioned concrete joined together by means of pre-stressing elements, a continuous cylindrical segment and a continuous or segmented cylindrical body of steel.