EP2857614A1

EP2857614A1 - Concrete tower formed with precast pieces

Info

Publication number: EP2857614A1
Application number: EP13187277.2A
Authority: EP
Inventors: Francisco Jose Saenz Saenz
Original assignee: Individual
Current assignee: Individual
Priority date: 2013-10-03
Filing date: 2013-10-03
Publication date: 2015-04-08
Also published as: WO2015049362A1

Abstract

Hollow tower (11) comprising a plurality of vertical sections (13) formed by several concrete precast pieces (15), being the precast pieces (15) of two contiguous vertical sections (13) arranged staggered so that each precast piece (15) of the upper section rests on at least two adjacent precast pieces (15) of the lower section; and the attachment means of the precast pieces (15) comprise tensor cables (17) which are arranged inside the tower (11) linking in zigzag each precast piece (15) of a vertical section (13) with the adjacent precast pieces (15) of the lower section and forming tensioning rings that join them together.

Description

FIELD OF THE INVENTION

The present invention relates to hollow concrete towers formed with precast pieces, especially but not exclusively, such as those that are used in wind turbines.

BACKGROUND

Nowadays there are numerous industrial applications which require the building of tall concrete towers structured with precast pieces.
Thus, for example, in the wind power industry there is a strong demand for towers as the ones described in the paragraph above to support the nacelle and the blades of high power wind turbines.
In addition, in this technical field, there is a growing tendency of increasing the tower's height for improving the performance of the wind turbines, in such a way that some of the more modern towers reach heights between 120 m and 150 m.
Concrete towers with said features are known in the art.
WO 2006/111597 describes a tower structured by a set of precast pieces of reduced thickness stiffened by an internal structure of horizontal and vertical ribs where horizontal and vertical tensor cables are used as attachments means of the precast pieces. During the mounting operation of a tower according to WO 2006/111597 , tensor cables are inserted in through-tubes (attached to the inner wall of the tower) and are subsequently filled with mortar. Consequently, according with this invention, the re-tensioning and/or replacement of cables during a maintenance operation is considerably complex or even impossible.
Moreover, in order to obtain a proper attachment of the prefabricated pieces comprising the tower, tensor cables described in WO 2006/111597 are also subjected to considerably high tensions, usually in the range of 100 - 300 ton-force (tf) for a 100m long standard tower, which can only be obtained by using special and expensive machinery.
WO 03/069099 describes a tower structured by a set of sections formed by several precast pieces where vertical tensor cables are used as primary attachments means of the precast pieces. Said vertical cables need to be attached to the foundations of the tower, which increases the difficulty of the mounting and maintenance operations. As in the preceding case, tensor cables are also subjected to considerably high tensions, usually in ranges similar to the one mentioned above. Moreover, large cranes are required for putting the vertical tensor cables in place.
In view of the above, the basic problems of such towers are: the mounting complexity, which frequently makes necessary the use of big cranes (and/or unconventional machinery), and the difficulty of performing maintenance operations, which often leads to high associated costs.
On the other hand, the presence of wind can make complicate both tasks, especially if they are performed in the upper part of the tower located, as previously discussed, at considerable height from the floor.
As is well known, wind turbine towers can be located in places difficult to be accessed by trucks and cranes, which are capable of transporting and/or lifting heavy loads to great heights.
The present invention is directed to solving those problems.

SUMMARY OF THE INVENTION

The basic object of the present invention is to provide a hollow tower structured in a plurality of vertical sections formed by several concrete precast pieces configured with outer and inner walls, upper and lower horizontal bases and side walls having sufficient strength to withstand the loads foreseen, facilitating its mounting and the maintenance tasks.
This object is met by a hollow tower where the precast pieces of two contiguous vertical sections are disposed staggered so that each precast piece of the upper section rests on at least two precast pieces of the lower section and where the attachment means of the precast pieces comprise tensor cables which are arranged inside the tower linking in zigzag each precast piece of a vertical section with the adjacent precast pieces of the lower section and forming tensioning rings that join them together.
This particular arrangement of tensor cables in a zigzag pattern makes possible for a single tensor cable to compress concrete precast pieces simultaneously in a vertical direction and a horizontal direction, resulting in a more effective use of the tension applied to said cable, as compared with prior art (in which tension is only applied either in a vertical direction or in a horizontal direction).
In fact, according to calculations made by the applicant, with one of the abovementioned zigzag cable arrangements which are part of the present invention, cable tensions in the range of 25 to 50 tf can lead to stiffness substantially similar to those obtained with the arrangement of tensor cables disclosed in WO 2006/111597 subjected to tensions in the range of 100- 300 ton-force (tf).
Thus, in the assembly of a tower according to the invention is possible to use, as compared with prior art, a cable tensioning machinery of significantly reduced technical requirements, which usually has a lower cost.
Another consequence is that, since tower stiffness is increased by means of the tensioning rings comprising tensor cables arranged in a zigzag pattern, towers according with the invention can reach higher heights than the prior art towers.
Said tensioning rings can have zigzag patterns of different forms, for example, a sawtooth zigzag pattern or a straight ends zigzag pattern. On the other hand, as the attachment means of the precast pieces of the present invention are disposed in the interior face of the tower, operators can easily access to the tensor cables and are less exposed to the wind (and other potentially negative external climatologic factors) during the mounting and maintenance tasks, which results in simplified mounting operations, increased security and less interruptions due to the excessive wind and/or adverse climatology (and consequently, in quicker mounting and maintenance procedures).
Moreover, review operations in the tower of the invention can be easily performed, for example by applying extensiometric gauges to the tensor cables. Maintenance and reparation operations can be also performed easily.
Preferably each vertical section of the tower is formed by equal precast pieces.
In one embodiment, the precast pieces comprise an anchoring element for said tensor cables having an upper conduit and a lower conduit for the passage thereof, said upper and lower conduits being located at a different distance from the inner wall of the precast pieces, and the cables that join each precast piece of a vertical section with the adjacent precast pieces of the lower section are arranged so that they pass, respectively, by their upper and lower conduits.
It is envisaged that the precast pieces also comprise interlocking means constituted by female recesses in their lower base and male inserts in its upper base configured to form joint arrangements between two precast pieces of two contiguous vertical sections that are sealed with grout. These joint arrangements constitute vertical attachment means of the precast pieces in addition to the tensioning rings mentioned above.
In an alternative embodiment of the invention, female recesses are disposed in the upper base of the precast pieces and male inserts in their lower base.
Other characteristics and advantages of the present invention will be clear from the following detailed description of embodiments illustrative of its object in relation to the attached Figures, in which identical or similar elements are identified with the same reference numbers.

BRIEF DESCRIPTION OF THE FIGURES

Figures 1a and 1b are respectively a plan view and a perspective view of an embodiment of a concrete precast piece used to form the tower of the invention.
Figure 2a is a view of Figure 1b along the plane A-A illustrating the interlocking means of the precast piece.
Figure 2b is a view of Figure 1b along the plane B-B illustrating the anchoring element of the tensor cables which link together the precast pieces.
Figure 3a is a perspective view of a second embodiment of a concrete precast piece used to form the tower of the invention.
Figure 3b is a view of Figure 3a along the plane A-A illustrating the interlocking means of the precast piece.
Figure 3c is a view of Figure 3a along the plane B-B illustrating the anchoring element of the tensor cables which link together the precast pieces.
Figure 3d is a perspective view of a third embodiment of a concrete precast piece used to form the tower of the invention.
Figures 3e and 3f are a plan view and a perspective view, respectively, of a fourth embodiment of a concrete precast piece used to form the tower of the invention. Figures 4a and 4b are schematic views illustrating two embodiments of the tower of the invention.
Figure 5 is a perspective view illustrating a first possible arrangement of the precast pieces of the concrete tower of the invention and of the tensor cables used to form tensioning rings.
Figure 6 is a perspective view illustrating a second possible arrangement of the precast pieces of the concrete tower of the invention and of the tensor cables used to form tensioning rings.
Figure 7 is a plan view illustrating the joint of contiguous precast pieces (according to the embodiment shown in Figures 3e and 3f), to form a vertical section of the tower, and also including an enlarged detail of said joint.

DETAILED DESCRIPTION OF THE INVENTION

The tower 11 of the invention is a tower structured in vertical sections 13, each section being formed by several precast pieces 15 (see figures 4a and 4b).
The precast pieces 15, configured with outer and inner walls 51, 53, upper and lower horizontal bases 57, 55 and side walls 59, 61, have, preferably, a dowel shape as illustrated in Figures 1a, 1b, 3a, 3d and are made with high strength concrete and inner steel bars 16.
The terms exterior, interior, upper and lower and lateral applied to the precast pieces 15 shall be understood in reference to their position in the tower 11.
Using dowel-shaped precast pieces 15, the tower 11 may have a frusto-conical or cylindrical shape as illustrated in Figures 4a and 4b. In the second case, all the vertical sections 13 have the same diameter while in the first case they have different diameters and different number of precast pieces 15 at different vertical sections 13, for example 6 precast pieces in the first vertical section and 2 precast pieces in the last vertical section.
Preferably, the height of the precast pieces 15 is comprised between 1.2 - 3 m and the ratio width/height is greater than 2. They are therefore precast pieces 15 of a relatively small size, and consequently easier to transport, compared with the sizes of other pieces known in the art (which are frequently between 15 and 25 m).
Precast pieces 15 may also have shapes that allow to build a tower 11 with a polygonal base.
On the other hand, precast pieces 15 may also have an outer wall 51 which is slightly longer, in the range of tens of cm, than the inner wall 53. As shown in Figure 7, this particular arrangement makes the gap 90, defined between the inner walls of two contiguous precast pieces 15 of a same vertical section 13 (and traditionally of 1-2.5 cm in size), to be slightly bigger than the gap 91, defined between the outer walls of two contiguous precast pieces 15 of a same vertical section 13 (and traditionally of 3-5 cm in size), thereby easing the assembly of said precast pieces 15 to form a tower 11.
In the embodiments illustrated in the Figures, the tower 11 is structured with the precast pieces 15 of each vertical section 13 mounted staggered with respect to the pieces of the lower section (see Figure 5) and joined by two attachment means: on the one hand, interlocking means as vertical attachment means between the precast pieces 15 of a vertical section 13 with the precast pieces of the lower vertical section; on the other hand tensor cables 17 to link together in zigzag by the inside the tower 11 the precast pieces 15 of a vertical section with the adjacent precast pieces of the lower section and to form a tensioning ring that joins them together.
The interlocking means comprise two female recesses 31, 33 and two male inserts 35, 37 which can be located respectively on the lower and upper bases 55, 57 of the precast pieces 15 (embodiment shown in Figures 1a, 1b, 2a, 2b) or, alternatively, in the opposite configuration (embodiment shown in Figure 3d). Preferably the male inserts 35, 37 are made of steel and configured with a cross-shaped head 36 and a shank 40 which is screwed into a sheath 41 embedded in the precast pieces 15. The joints between male inserts 35, 37 and female recesses 31, 33 are filled with a slurry of high strength concrete which is poured through holes 39 (see Figure 2a). This particular configuration (i.e., the embodiment in the form of a cross-shape head) gives the male insert 36 a bigger contact surface with the grout, which results in a more cohesive connection.
In addition, male inserts 35, 37 absorb part of the shear stress to which the tower 11 is subjected and the staggering of the precast pieces 15 of a vertical section 13 of the tower 11 with respect to the precast pieces 15 of the lower vertical section implies that the two female recesses 31, 33 of a precast piece 15 engage with the male inserts 37, 35 of two different precast pieces 15 of the lower vertical section thereby enhancing the strength of the tower 11.
Alternatively, EPDM (Ethylene Propylene Diene Monomer) rubber profiles can be interposed between the precast pieces 15 of a vertical section 13 and the precast pieces of the lower vertical section, being said EPDM rubber profiles intended to improve the rest of the vertical section on the lower vertical section as well as the tightness.
In the embodiments illustrated in Figures 1a, 1b, 2a, 2b, and 3d the precast pieces 15 comprise anchoring elements 21 for tensor cables 17 which are embedded in the precast pieces 15 by their inner wall 53. These anchoring elements 21 comprise an upper conduit 23 and a lower conduit 25 for the passage of tensor cables 17.
In the embodiment illustrated in Figure 5 a tensor cable 17 passes through the upper conduits 23 of the precast pieces 15 of the central vertical section 13 and through the lower conduits 25 of the precast pieces 15 of the lower section and another tensor cable 17 passes through the lower conduits 25 of the precast pieces 15 of the central vertical section 13 and by upper conduits 23 of the precast pieces 15 of the upper section. To avoid crossing of cables 17, the upper and lower conduits 23, 25 are located at a different distance from the inner wall of the precast pieces 15 (contrary to the embodiment shown in Figure 2b). With this provision, the tensor cables 17 allow "tying" two vertical sections 13 of the tower 11 in a more efficient manner. In this particular configuration, the tensioning ring created by tensor cables 17 has the form of a sawtooth zigzag pattern.
In the embodiment illustrated in Figure 6 the tensioning ring has, in turn, the form of a straight ends zigzag pattern.
In an alternative embodiment shown in Figures 3a, 3b, 3c, anchoring elements for tensor cables 17 comprise U shaped bars 71, whose end parts (or legs) are embedded in the precast pieces 15 by their inner wall 53, while the central part of said U shaped bars 71 slightly protrude from the inner wall 53, forming an eye through which tensor cables 17 can be passed. Recesses 72 can be also optionally provided in the area surrounding said U shaped bars.
Once tensioned the tensor cables 17 by means of, for example, a portable electric tensioning pump or a portable mono-cable tensor they are arranged in the form of a ring which starts and ends at the same point in which is placed a double cone terminal (a cone for the start of the cable and other for the ring closure).
On the other hand, side walls 59, 61 of the concrete precast pieces 15 can be optionally provided of slots 80, 81, shown in figure 3d, and intended to reinforce the horizontal attachment of two contiguous precast pieces 15 in the same vertical section 13. To this end, the space defined by said contiguous slots 80, 81 is sealed with grout.
Optionally at least one corrugated bar is held in such space.
As shown in Figures 3e and 3f, precast pieces 15 can also be provided with housings 73, disposed on the peripheral areas of the upper horizontal base 57 closer to side walls 59, 61, being each housing 73 intended to house one of the ends of an U shaped staple 75 and being each one of said staples 75 intended, in turn, to join two contiguous precast pieces15 belonging to the same vertical section 13. Optionally, the space between housings 73 and the U shaped staples 75 can be sealed with grout.
Grooves 74, intended to ease the housing of staples 75 in housings 73, can be optionally provided.
The foundation of the tower 11 can be done by, for example, a reinforced concrete footing 62.
Although the present invention has been described in connection with various embodiments, it will be appreciated from the specification that various combinations of elements, variations or improvements therein may be made, and are within the scope of the invention.

Claims

Hollow tower (11) comprising a plurality of vertical sections (13) formed by several concrete precast pieces (15), configured with outer and inner walls (51, 53), lower and upper horizontal bases (55, 57) and side walls (59, 61), and attachment means of them, characterized in that:
- the precast pieces (15) of two contiguous vertical sections (13) are arranged staggered so that each precast piece (15) of the upper section rests on at least two adjacent precast pieces (15) of the lower section;

- the attachment means of the precast pieces (15) comprise tensor cables (17) which are arranged inside the tower (11) linking in zigzag each precast piece (15) of a vertical section (13) with the adjacent precast pieces (15) of the lower section and forming tensioning rings that join them together.
Hollow tower (11) according to claim 1, wherein the height of each vertical section (13) is comprised between 1.2-3m.
Hollow tower (11) according to any of claims 1-2, wherein each vertical section (13) is formed with equal precast pieces (15).
Hollow tower (11) according to any of claims 1-3, wherein the tensioning rings formed by tensor cables (17) have the form of sawtooth zigzag patterns and/or of straight ends zigzag patterns.
Hollow tower (11) according to any of claims 1-3, wherein:
- the precast pieces (15) comprise an anchoring element (21) of said tensor cables (17) having an upper conduit (23) and a lower conduit (25) for the passage thereof, said upper and lower conduits (23, 25) being located at different distances from the inner wall (53) of the precast pieces (15);

- the tensor cables (17) linking each precast piece (15) of a vertical section (13) with the adjacent precast pieces (15) of the lower section are arranged to pass, respectively, through the upper and lower conduits (23, 25) of the anchoring elements (21).
Hollow tower (11) according to any of claims 1-4, wherein: the anchoring elements for tensor cables (17) comprise U shaped bars (71), whose end parts are embedded in the precast pieces (15) by their inner wall (53), while the central part of said U shaped bars (71) slightly protrude from the inner wall (53), forming an eye through which tensor cables (17) can be passed.
Hollow tower (11) according to claim 6, wherein recesses (72) are provided in the area surrounding said U shaped bars (71).
Hollow tower (11) according to any of claims 1-7, wherein:
- the precast pieces (15) of each vertical section (13) comprise, except in the first section, two female recesses (31, 33) in its lower base (55) and, except in the last section, two male inserts (35 , 37) on its upper base (57) to form joint arrangements between the precast pieces (15) of two contiguous vertical sections (13);

- said female recesses (31, 33) and said male inserts (35, 37) are configured so that the male inserts (35, 37) of the lower section can be arranged with play within the female recesses (31, 33) of the upper section;

- the space between male inserts (35, 37) and female recesses (31, 33) of the precast pieces (15) of two contiguous vertical sections (13) is sealed with grout which is poured through a hole (39) disposed on the precast pieces (15).
Hollow tower (11) according to any of claims 1-7, wherein:
Precast pieces (15) of each vertical section (13) comprise except in the first section, two female recesses (31, 33) in its upper base (55) and, except in the last section, two male inserts (35 , 37) on its lower base (57) to form joint arrangements between the precast pieces (15) of two contiguous vertical sections (13);
- said female recesses (31, 33) and said male inserts (35, 37) are configured so that the male inserts (35, 37) of the upper section can be arranged with play within the female recesses (31, 33) of the lower section;

- the space between male inserts (35, 37) and female recesses (31, 33) of the precast pieces (15) of two contiguous vertical sections (13) is sealed with grout which is poured through a hole (39) disposed on the precast pieces (15).
Hollow tower (11) according to any of claims 8 and 9, wherein male inserts (35, 37) are configured with a cross-shaped head (36) and a shank (40) which is screwed into a sheath (41) embedded in the precast pieces (15).
Hollow tower (11) according to any of claims 1-10, wherein:
- the precast pieces (15) are dowel-shaped pieces;

- each vertical section (13) of the tower (11) is cylindrical-shaped.
Hollow tower (11) according to claim 11, wherein:
- the tower (11) comprises vertical sections (13) of a lesser diameter than their contiguous lower sections;

- the tower (11) comprises vertical sections (13) with a lesser number of dowel-shaped pieces (15) than their contiguous lower sections.
Hollow tower (11) according to any of claims 1-12, wherein precast pieces (15) also have an outer wall (51) which is slightly longer than the inner wall (53).
Hollow tower (11) according to any of claims 1-13, wherein side walls (59, 61) of the concrete precast pieces (15) are provided of slots (80, 81), intended to allow the horizontal attachment of two contiguous precast pieces (15) in the same vertical section (13).
Hollow tower (11) according to any of claims 1-13, wherein precast pieces (15) are provided with housings (73), disposed on the peripheral areas of the upper horizontal base (57) closer to side walls (59, 61), being each housing (73) intended to house one of the ends of an U shaped staple (75) and being each one of said staples (75) intended, in turn, to join two contiguous precast pieces(15) belonging to the same vertical section (13).