US20120042585A1

US20120042585A1 - Prefabricated wall element for tower construction, and tower construction

Info

Publication number: US20120042585A1
Application number: US13/202,736
Authority: US
Inventors: Roger Ericsson
Original assignee: Individual
Current assignee: Individual
Priority date: 2009-02-27
Filing date: 2010-02-24
Publication date: 2012-02-23
Also published as: JP2012519244A; EP2401454A1; SE534051C2; SE0950105A1; WO2010098716A1

Abstract

The invention relates to a prefabricated wall element for a tower construction, essentially of concrete, arranged to form one of several wall portions of a building formed by circumferential shell portions of one of several shell portions stacked on each other, wherein the wall element is constituted by a substantially flat sheet portion comprising a pair of opposite sides intended to run substantially horizontally in the building and a pair of opposite sides intended to run in a direction forming a predetermined angle to the horizontal plane in the building, and along which sides the wall element includes compressive and tensile load absorbing pillar portions and is intended to be connected to adjacent wall elements. The invention also relates to a tower construction, a mobile antenna system and a wind power plant.

Description

TECHNICAL FIELD

The invention relates to a prefabricated wall element for a tower construction according to the preamble of claim 1. The invention also relates to a tower construction according to the preamble of claim 15. The invention also relates to a mobile antenna system. The invention also relates to a wind power plant.

BACKGROUND ART

Today a great number of variants of wind power plants exist. A wind power plant comprises a turbine connected to blades, and a tower arranged to support the turbine. One type of wind power plant is steal towers which may be cylindrical or have a grid structure or analogous. Steal towers have a number of disadvantages though. For example they are affected by weather and thus not suitable on the sea, they require a great deal of maintenance and thus high maintenance costs, they require very thick walls in order to withstand load of powerful wind power plants and are from a technical and economical point of view not suitable for towers higher than 70 meters due to material costs and the rigidity required. The compressive strength for steel is relatively poor in relation to weight. Production of steel towers also results in transportation problems, and requires much installation work due to e.g. many bolts.
The development of wind power plants is towards higher and higher power, higher positioning of the turbine blades and bigger turbine blades, and thus higher towers, up to and above 100 m. Hereby the loads are great and steel towers not suitable. Further, the desire to build wind power plants at sea has increased, where steel becomes difficult to handle and maintenance-demanding. Therefore reinforced concrete is used instead which is more weather proof and more cost efficient. Hereby according to a variant prefabricated concrete rings are used, which are stacked on top of each other by means of a lifting crane and are connected by means of tension ropes or the corresponding. This production technique though has the drawback that the large concrete rings are difficult to transport and complicated to manufacture, which results in high production costs. Another variant is to cast the tower on site, wherein mould is produced on site and the concrete is added. This has the disadvantages that the quality of the concrete and thus the strength becomes impaired, the production is weather dependent, the production of the tower is time consuming, it requires a big crane and ladder scaffolding, and dismantling/destruction of mould.
WO 03/069099 discloses a wind turbine with a tower being built up by prefabricated wall elements essentially of concrete, the wall elements forming a number of wall portions of circumferential shell portions of one of several shell portions stacked on each other. The prefabricated wall elements are equally thick solid wall elements being even on both the outside and the inside in order to provide structural rigidity and loading capacity. The wall elements have a curved cross section. The curved cross section is according to an embodiment V-shaped with obtuse angle in order to form a facet shaped cross section. A disadvantage with such wall elements is that they are relatively complicated to cast. They are further du to the shape relatively difficult to transport and due to the weight relatively difficult to handle during assembly. Further a lot of concrete is required which makes them relatively expensive to produce.
EP 1876 316 A1 discloses a wind turbine with a tower which is built up by prefabricated wall elements essentially of concrete, the wall elements forming a number of wall portions of circumferential shell portions of one of several shell portions of the tower stacked on each other. The prefabricated wall elements have according to variants reduced thickness reinforced with an internal structure of horizontal and vertical stiffeners, said wall elements having an arched cross section and being stretched both horizontally and vertically by means of flexible metal cables. A disadvantage with such wall elements is that they are relatively complicated to cast. They are further due to the shape relatively difficult to transport and due to the weight relatively difficult to handle during assembly.
Bracing cables, e.g. in high-tensile twisted steel, are used to reduce the amount of reinforcement and also to reduce the assembly time wherein concrete constructions such as towers for wind power plants according to above are stretched after casting. The stretching force provided gives deformations being counter directed to the influence from outer loads. This improves the static properties of the construction. It used to be common to provide post-tensioned constructions with a stretching force of such a magnitude that no tensile stresses arose, but now partial pre-stressing is most common, i.e. tensile stresses are allowed and are taken by non-tensioned reinforcement. One reason is that a construction with post-tensioned reinforcement is subjected to great concentrated compressive forces from the bracing cables to certain points that may provide unwanted deformations. When the bracing cable consists of twisted steel the bracing cables need to be pulled and further fastened by means of wedges, which causes anchor slip. The bracing cable thereto tends to creep by itself, particularly during the first year. The concrete both shrinks and creeps and all together causes forced forces in concrete and connections with resulting cracks. Bracing cable of thin twined steel is also more sensitive to temperature rises during fire wherefore securing of the construction is provided by non-tensioned reinforcement. The fact that the bracing cable also needs to be stretched with a dumb craft means that it may not be to heavily constructed since the dumb craft in that case becomes unwieldy. This means that the amount of cables needed to be pulled and stretched becomes extensive and demands both heavy equipment and professional competence to be performed correctly.
Conventional towers for mobile antennas are today built in steel constructions. A problem with such constructions is that communication equipment arranged in the steel tower is accessible in the tower, and such communication equipment is liable to be stolen. Steel towers quickly become expensive if they are to handle large pressure loads since the thickness of the goods increases strongly.
One solution to this problem is known through a tower construction with circular cylindrical shape in concrete, which is cast and reinforced in a ring-shaped section, where several rings are stacked on each other. In the bottom bracing cables are anchored, by means of which the construction is stretchable according to the compressive strength that the construction can handle such that it becomes stable. The rings are arranged to be locked such that a rigid tower is achieved. According to a variant the tower construction is about 40 m high. The tower construction is configured such that the central/communication equipment may be arranged uppermost in the tower where it is accommodated. This solution prevents theft, and simplifies wire laying and cooling of the entire system. The tower however becomes relatively expensive and demands relatively thick, about 7 cm, concrete rings in order to evenly distribute and withstand the compressive loads without to big a risk for local tensions and deformations running the risk of the occurrence of cracks and at the same time providing a covering layer on the reinforcement. The thick circular cylindrical concrete rings, which may be 10 m high and 2-3 m in diameter, are difficult to manufacture, heavy and unwieldy to transport. Alternatively the rings are segmented but that does not improve the situation to any appreciable extent. Masts for mobile systems are often placed in rough terrain such as jungle and mountain ground in order not to disturb the environment. Transporting the concrete rings/concrete segments to and then build up the tower construction in such terrain is complicated.

OBJECT OF THE INVENTION

An object of the present invention is to provide a wall element for a tower construction which facilitates easy manufacturing, easy transport and easy assembly, and which is cost efficient.
An additional object of the present invention is to provide a tower construction which facilitates easy manufacturing, easy transport and easy assembly, and which is cost efficient.
An additional object of the present invention is to provide a tower construction which is suitable for wind power plants with high loads and which demands towers with a height in the magnitude of 100 m which facilitates easy and cost efficient manufacturing and transport.
An additional object of the present invention is to provide a tower construction which is suitable for mobile antenna systems with demands on high rigidity and which require towers with a height in the magnitude of 40 m which facilitates easy and cost efficient manufacturing, transport and assembly.

SUMMARY OF THE INVENTION

These and other objects, apparent from the following description, are achieved by means of a wall element for a tower construction, a tower construction, a wind power plant, and a mobile antenna system, which are of the type stated by way of introduction and which in addition exhibits the features recited in the characterising clause of the appended independent claims 1, 15, 16 and 18. Preferred embodiments of the device are defined in appended dependent claims 2-14, 17 and 19.
According to the invention the objects are achieved by a prefabricated wall element for a tower construction, essentially of concrete, arranged to form one of several wall portions of a building formed by circumferential shell portions of one of several shell portions stacked on each other, wherein the wall element is constituted by a substantially flat sheet portion comprising a pair of opposite sides intended to run substantially horizontally in the building and a pair of opposite sides intended to run in a direction forming a predetermined angle to the horizontal plane in the building, and along which sides the wall element includes compressive and tensile load absorbing pillar portions and is intended to be connected to adjacent wall elements. Hereby easy and cost efficient production and transport of wall elements is facilitated. The flat configuration of the wall element is easy to cast and thus easy to manufacture. Further, the flat configuration results in transportation and handling of the wall elements becoming very easy, which reduces the costs. Thanks to the compressive and tensile load absorbing pillar portions the amount of concrete may be reduced which consequently reduces the material costs.
According to an embodiment the wall element further comprises a substantially horizontally running compressive and tensile load absorbing strut portions. Thanks to the compressive and tensile load absorbing strut portions the amount of concrete may be reduced which consequently reduces the material costs.
According to an embodiment of the wall element the pillar portions comprises pillar channel portions running in the longitudinal direction of the pillar portion. Hereby a simple and stable connection between circumferential shell portions for forming of the tower construction is facilitated.
According to an embodiment of the wall element the strut portions comprises strut channel portions running in the longitudinal direction of the strut portion. Hereby reinforcement by means of strut elements and individual post-tensioning of the strut portions of the wall element is facilitated.
According to an embodiment of the wall element said circumferential shell portions are connected by means of rigid bar elements running in the channel portions. This results in a stable connection.
According to an embodiment of the wall element said bar elements are stretchably arranged in the pillar channel portions. Hereby wall elements may be post-tensioned in a factory or after assembly of said shell portions.
According to an embodiment of the wall element a rigid bar element is stretchably arranged in the respective strut channel portion. Herby wall elements may be post-tensioned in a factory of after assembly of said shell portions.
According to an embodiment of the wall element the pillar portions of the wall element are arranged to be releasably locked to adjacent pillar portions of wall elements by means of locking elements for the formation of said building. Hereby dismantling of the wall elements of a tower construction is facilitated such that the wall elements may be reused for building up of a tower construction on e.g. a different location. This results in a construction suitable for towers of mobile antenna systems.
According to an embodiment the wall elements are arranged to be connected by means of cast concrete in the channel portions. Hereby a very stable and rigid connection with high structural strength is obtained in order to withstand great loads and which is suitable for supporting of a turbine of a wind power plant.
According to an embodiment of the wall element the concrete of the wall element is high performance concrete composed of cement and ballast with a weight ratio between amount of water and amount of cement, vct, being lower than 0,39. Hereby the sheet portion may be made water, salt and acid proof.
According to an embodiment of the wall element the composition of the high performance concrete comprises a mixture of 10-20% sharp sand, and/or 1-5 percentage by volume of aerogel and/or slag in glass phase and/or mineral fibres such as carbon, silicate and/or basalt fibre. With such an admixture a concrete with such properties is achieved that the tensile strength increases, almost doubled, which surprisingly results in the high performance concrete being fire proof.
With a vct lower than 0,39 and admixture of ballast in the cement according to above it is facilitated to provide a long-term constructive sheet with a thickness down to only about 20 mm, i.e. way below the norm for covering layers, served to protect the reinforcement steel from corroding through water, salt and acid penetration or quickly lose its strength during fire. Hereby the amount of concrete may be reduced considerably which results lighter and consequently more easily handled wall elements, and reduces the manufacturing costs. This consequently facilitates providing a thickness of the sheet portion being thinner than the norm for covering layers, i.e. thinner covering layers on the respective side of the reinforcement net than 30 mm, the reinforcement net being according to an embodiment about 10 mm, may be provided with maintained fire protection avoiding capsizing and maintained water resistance avoiding corrosion.
According to an embodiment of the wall element said high performance concrete has a flexural strength greater than 10 MPa. According to an embodiment of the wall element said high performance concrete has compressive strength greater than 90 MPa. The Pillar and strut portions may thanks to the good compressive and tensile strength be dimensioned to take all occurring vertical and horizontal compressive and tensile forces of the tower construction while the relative to the pillar and strut portion thin sheet portions may be made so thin that they only answer for bracing.
According to an embodiment of the wall element the pillar portions have an extension in the range of 5-15 metre, preferably in the range of 8-13 m. This is a suitable range for managing easy transport and handling and keeping the manufacturing time down.
According to the invention the objects are achieved with a tower construction according to any of the embodiments above.
According to the invention the objects are achieved with a mobile antenna system comprising a tower construction according to embodiments above, and communication equipment arranged in the upper part of the tower construction. By simple and cost efficient manufacturing and transport of wall elements the wall elements may be easily transported to rough terrain such as jungle and mountain ground in order not to disturb environment, wherein the mobile antenna system then, thanks to the wall elements being easy to handle, easily may be built up in the rough terrain.
According to an embodiment of the mobile antenna system the tower construction has a height in the range of 25-50 m. This is a suitable height of a tower construction for mobile antenna systems.
According to an embodiment the objects are achieved with a wind power plant comprising a turbine, turbine blades connected to the turbine, and a tower construction according to embodiments above, which tower construction is arranged to support said turbine. By easy and cost efficient manufacturing and transport of wall elements the wall element may be easily transported to a suitable location such as out at the sea by means of a boat, the tower construction advantageously being arrangeable there due to the fact that it is not sensitive to weather. The wind power plant may then, thanks to the wall elements being easy to handle, easily be built up in the rough terrain.
According to an embodiment of the wind power plant the tower construction has a height in the range of 60-140 m. this is today considered as being a suitable height of a tower construction for a wind power plant.

DESCRIPTION OF THE DRAWINGS

A better understanding of the present invention will be had upon the reference to the following detailed description when read in conjunction with the accompanying drawings, wherein like reference characters refer to like parts throughout the several views, and in which:

FIG. 1 schematically illustrates a side view of a portion of a wall element according to a first embodiment of the present invention;

FIG. 1 a-c schematically illustrate different cross sections of the wall element in FIG. 1;

FIG. 2 schematically illustrates a plan view of respectively one portion of two interconnected wall elements according to FIG. 1;

FIG. 3 a-b schematically illustrate side cross sections of portions of two wall elements according to FIG. 1 stacked on each other;

FIG. 4 schematically illustrates a plan view of wall elements according to FIG. 1 interconnected to a tower section;

FIG. 5 a schematically illustrates a tower construction according to an embodiment of the present invention during assembly;

FIG. 5 b schematically illustrates a tower construction according to FIG. 5 an interconnected;

FIG. 5 c schematically illustrates a part of a bar element for assembly of tower sections according to an embodiment of the present invention;

FIG. 6 schematically illustrates a side view of a portion of a wall element according to a second embodiment of the present invention;

FIG. 6 a-c schematically illustrate different sections of the wall element in FIG. 6;

FIG. 7 schematically illustrates a plan view of respectively one portion of two interconnected wall elements according to FIG. 6;

FIG. 8 a schematically illustrates a side cross section of a portion of the wall element according to FIG. 6;

FIG. 8 b schematically illustrates side cross sections portion of wall elements according to FIG. 6;

FIG. 9 schematically illustrates a tower section composed of wall elements according to FIG. 6; and

FIG. 10 a-d show different measured data of high performance concrete according to the present invention compared to conventional concrete.

DESCRIPTION OF EMBODIMENTS

FIG. 1 schematically illustrates a side view of a portion of a flat wall element 20 for a tower construction according to a first embodiment of the present invention, and FIG. 1 a-c schematically illustrate different cross sections A-A, B-B, C-C of the wall element in FIG. 1.
The flat wall element 20 is prefabricated. The flat wall element 20 is obtained by casting in a mould which mould has recesses for pillars and struts. The flat wall element 20 is consequently easy to produce since it may be cast in one piece with a simple mould.
The wall element has an outer side 20 a and an inner side 20 b. The wall element 20 is essentially constituted by a flat sheet portion 22, a pair of opposite sides of which one 20 c is shown, intended to run substantially horizontally in the tower construction and a pair of opposite sides 20 e, 20 f intended to run in a direction forming a predetermined angle to the horizontal plane in the tower construction. Said angle to the horizontal plane is according to an embodiment in the range of 90 degrees +/−30 degrees. According to an embodiment the opposite sides 20 e, 20 f of the wall elements are intended to run substantially vertically in the tower construction, i.e. perpendicular relative to the horizontal plane or with a certain inclination relative to the vertical plane.
The wall element 20 includes compressive and tensile load absorbing pillar portions 23 a, 23 b running along the sides 20 e, 20 f. The wall element is intended to be connected to adjacent wall elements. The wall element includes compressive and tensile load absorbing strut portions 24 a of which one is shown, and preferably at least one intermediate strut portion 24 b of which one is shown running between the pillar portions parallel to and at a distance from the strut portions running along the sides 20 c. Said strut portions 24 a, 24 b is referenced to below as the strut portions.
The wall element 20 consequently constitutes a flat tetragonal module or cassette with dimensions adapted to the purpose. According to this embodiment the tetragonal wall element is rectangular. According to another embodiment the tetragonal wall element is trapezoidal, preferably with equal angle on the respective inclined side, such that it receives the shape of a truncated equally sided triangle. The tetragonal wall element 20 has according to this embodiment a height being approximately three times its width. According to an embodiment the height of the wall element is in the range of 5-15 m, preferably 8-13 m. Other extensions of height of the wall element 20 are conceivable and depend among others on the application.
The wall element 20 comprises according to an embodiment a reinforcement configuration, not shown, which according to a variant comprises a reinforcement net or the corresponding which preferably has an extension or surface essentially corresponding to the surface of the mould, the reinforcement net according to an embodiment constituting the reinforcement in the flat sheet portion 22. The reinforcement net thus preferably has a substantially flat configuration. According to an alternative embodiment the sheet portion has no reinforcement/no reinforcement net, which is made possible by the pillar portions 23 a, 23 b and the strut portions being arranged to absorb the vertical and horizontal loads, wherein the bracing to be handled by the sheet portion 22 is highly insignificant. Preferably the sheet portion according to this embodiment without reinforcement comprises fibres.
The pillar portions 23 a, 23 b of the wall element 20 are internally cast in the wall element 20 and consequently arranged to run in a direction forming a predetermined angle to the horizontal plane in a tower construction, preferably arranged to run substantially vertically in a tower construction. The strut portions 24 a, 24 b are internally cast in the wall element 20 and consequently arranged to run in a direction substantially horizontally in a tower construction.
The wall element 20 comprising pillar portions 23 a, 23 b and strut portions 24 a, 24 b is cast according to the configuration of pillars and struts in the mould. The wall element 20 further comprises the casted flat sheet portion 22 reinforced with the reinforcement net. According to this embodiment the external side 20 a of the wall element is essentially even and the internal side has enhancements formed by the pillar and strut portions.
The pillar portions 23 a, 23 b have through channel portions 26 running in their longitudinal direction. According to an embodiment the pillar channel portions 26 are constituted by tubular bars. According to another embodiment the pillar channel portions are constituted by tubular channels formed during casting of pipes which are removed after casting.
The strut portions 24 a, 24 b have through channel portions 27 running in their longitudinal direction. According to an embodiment the channel portions 27 are constituted by tubular bars. According to another embodiment the pillar channel portions are constituted by tubular channels formed during casting of pipes which are removed after casting.
Removal of a tubular element from the formed pillar channel portion 26 and strut channel portion 27 is facilitated e.g. by the tubular element being waxed or lubricated prior to being cast.
Bar elements 44 are arranged to be inserted into the strut channel portions 27 for post-tensioning of the wall element 20. According to yet another embodiment the channel portion 27 is formed by means of a bar element 44 which is arranged to be embedded such that it may be post-tensioned, wherein the channel portion then already has a bar element introduced therein. According to an embodiment the post-tension of strut portions 24 a, 24 b of the wall element 20 is provided in factory, i.e. the post-tension is prefabricated. According to another embodiment the post-tension of strut portions 24 a, 24 b of wall elements 20 is arranged to be provided after assembly. The bar element 44 in the respective channel portion is preferably rigid. The bar element 44 is preferably of steel. The bar element is preferably straight, each strut channel portion consequently being straight.
According to this embodiment the bar element 44 is arranged in the respective strut channel portion 27. According to an alternative embodiment two or more bar elements are arranged in the respective strut channel portion 27, the bar elements being dimensioned for a certain load, wherein, according to a variant with several bar elements, the bar elements are thinner than if one bar element is used per strut channel portion. The bar elements may be arranged as an interconnected group or separately arranged in the respective channel portion.
According to an embodiment fasteners 46 a, 46 b for bar elements 44 are arranged at the respective pillar portion 23 a, 23 b, which fastener 46 a, 46 b according to a variant is an embedded sheet metal portion to which a bar element 44 is arranged to be fixed, wherein the bar element 44 according to an embodiment may be post-tensioned by means of e.g. a nut 44 a. This is more apparent in FIG. 2.
According to this embodiment the pillar portions 23 a, 23 b are bevelled externally, i.e. having a grade along its respective external side, which sides constitute the pair of opposite sides 20 e, 20 f of the wall element. Hereby each pillar portion increases gradually in width from its inside to its outside. The external grade or angle along the respective pillar portion 23 a, 23 b is adapted for the number of wall elements 20 to be interconnected side to side in order to form a ring-shaped section such as described in connection to FIGS. 2 and 3. The grade of each pillar portion is provided during casting in that the mould having a corresponding shape.
The casted pillar portions 23 a, 23 b and the strut portions 24 a, 24 b constitute reinforcements of the wall element 20 arranged to withstand compressive and tensile forces. The sheet portion 22 of the wall element 20 is according to this embodiment arranged to only handle smaller bracing forces and may therefore be made very thin such that the amount of concrete may be reduced considerably.
By means of the flat form of the wall element 20 easy transport is facilitated in that theses wall elements 20 easily may be stacked in a pile on top of each other and transported and be transported on e.g. a truck, boat or the like. They take up little space and are not unwieldy. Due to the fact that the amount of concrete is reduced thanks to the relative to the pillar and strut portions thin sheet portions 22 they become relatively light weight and thus easy to handle.
According to a preferred embodiment the wall element 20 is made of high performance concrete with such properties that the wall element 20 with a sheet portion 22 having a thickness thinner than the norm of covering layers, i.e. thinner than covering layers on the respective side of the reinforcement net 18 than 30 mm, the reinforcement net 18 according to an embodiment being about 10 mm, may be provided. According to an embodiment the sheet portion of the wall element 20 is thus thinner in thickness than 70 mm whereby a thickness of the sheet portion 22 of the wall element 20 down to 20 mm by be provided with maintained fire protection avoiding capsizing and maintained water resistance avoiding corrosion.
By using high performance concrete with the above mentioned properties a considerably lighter construction with maintained compressive and tensile strength properties which further simplifies transport and assembly in rough terrain and for manufacturing of towers for mobile masts.
FIG. 2 schematically illustrates a plan view of respectively one portion of two interconnected wall elements according to FIG. 1, FIG. 3 a-b schematically illustrate side cross sections of portions of two wall elements according to FIG. 1 stacked on each other, and FIG. 4 schematically illustrates a plan view of the wall element according to FIG. 1 interconnected to a ring-shaped tower section.
Each prefabricated wall element 20 is arranged to form one of several wall portions 20 of circumferential shell portions 30 of a tower construction formed of several shell portions 30 stacked on each other, as is shown in FIG. 5. The circumferential shell portions 30 form the ring-shaped tower section 30.
The wall elements 20 are arranged to be interconnected by arranging the external side of a pillar portion 23 a, 23 b of a wall element 20 to an external side of a pillar portion 23 b, 23 a of another wall element 20 such that they abut against each other according to FIG. 2 such that the internal sides of each wall element 20 are angled inwardly towards each other.
Additional wall elements 20 are interconnected according to above such that a ring-shaped section 30 or a circumferential shell portion is achieved. The prefabricated flat wall elements 20 are thus placed along each other such that a ring-shaped section 30 or a circumferential shell portion 30 is formed. The ring-shaped section is here constituted by identical flat wall elements 20 wherein a facet-shaped ring 30 is achieved. According to this embodiment the number of wall elements 20 in one section is six, wherein the ring-shaped section 30 has a hexagonal cross section in the horizontal plane. Hereby the external bevel or grade of the pillar portions is 15 degrees.
The number of wall elements 20 according to alternative embodiments may be more or fewer, more resulting in a more circular shaped section and thus more stable from a strength point of view and lighter wall elements 20, and fewer results in quicker assembly and fewer wall elements 20 to handle.
The wall elements 20 are arranged to be fixedly locked by means of releasable fasteners or locking elements 40 a such that said ring shaped section 30 or circumferential shell portion is achieved, see FIG. 2. The releasable fasteners 40 a are according to an embodiment constituted by fittings 40 a. The fittings 40 a is according to a variant arranged at the strut portions 24 a, 24 b in connection to the adjacent pillar portions 23 a, 23 b to releasably lock the wall elements 20. According to this embodiment the locking element is arranged to releasably lock the wall elements to each other by fixing the locking element 40 a to fasteners 46 b, 46 a of each wall element 20, here the embedded sheet metal portion 46 b, 46 a, illustrated in FIG. 2, by means of or corresponding. The locking element is arranged to extend substantially horizontally internally 20 b between two adjacent wall elements 20 for said locking.
The tower sections are arranged to be formed by stacking tower sections on each other, wherein wall elements in FIG. 3 a-b are stacked on each other, wherein a lower end of the respective pillar portion 23 a, 23 b of the respective wall element 20 of the upper section 30 rests on an upper end of the respective pillar portion 23 a, 23 b of the lower tower section 30 wherein upper and lower end of the respective pillar portion 23 a, 23 b according to a variant has a step such that they engage for preventing lateral sliding of the tower section, se FIG. 3 a. The pillar portions 23 a, 23 b of the lower tower section 30 are consequently arranged to support upper tower section 30. Further during stacking of wall elements according to above a lower strut portion 24 a of the wall element 20 of the upper tower section 30 is arranged to rest on an upper strut portion 24 c of the wall element 20 of the lower tower section 30 wherein upper and lower strut portions according to a variant have a step such that they engage for preventing lateral sliding of the tower sections, se FIG. 3 b.
The wall elements 20 of the upper tower section are arranged to be fixedly locked with the wall element of an underlying tower section by mends of releasable fasteners or locking elements 40 b. The releasable fasteners 40 b are according to an embodiment constituted of fittings 40 b. The fittings 40 a are according to a variant arranged at the strut portions 24 a, 24 c in connection to the adjacent pillar portions 23 a, 23 b to releasably lock the wall elements 20. According to this embodiment the locking element is arranged to releasably lock the wall element to each other by fixing the locking element 40 a to fasteners 46 a, 46 b of the respective wall element 20, here the embedded sheet metal portion 46 b, 46 a, illustrated in FIG. 2, by means of nuts or the corresponding. The locking element is arranged to extend substantially vertically internally 20 b between to wall elements 20 stacked on each other for said locking.
FIG. 5 a schematically illustrates a tower construction according to an embodiment of the present invention composed of wall elements 20 according to FIG. 1, and consequently tower section 30 according to FIG. 4, during assembly comprising tower sections according to FIG. 4, FIG. 5 b schematically illustrates the tower construction according to FIG. 5 a interconnected, and FIG. 5 c schematically illustrates a part of a bar element for interconnection of tower sections stacked on each other according to an embodiment of the present invention.
The tower section 50 is built up of ring-shaped tower sections 30 or circumferential shell portions as described in connection to FIG. 4, wherein tower sections 30 are arranged to be stacked on each other as described in connection to FIG. 3 a-b. The sections 30 are arranged to be connected to each other for forming of the tower construction 50 by aligning the respective pillar portion 23 a, 23 b of the respective tower section to each other such that a tower pillar with a through channel running in its longitudinal direction ay be formed.
The tower construction 50 comprises the bar elements 43. According to an embodiment of the tower construction said circumferential shell portions 30 stacked on each other are connected by means of bar elements 43, suitably of stainless steel, running in the pillar channels 26. The bar elements are according to this embodiment anchored at the top and bottom of the tower construction by means of anchorages 45 a, 45 b, or in portions thereof. The bar elements are preferably single rigid bar elements which have the advantage that they may be dimensioned and post-tensioned with greater forces and with a simpler method than a flexible bracing cable.
In the construction according to the invention a high performance concrete which among others has such properties that it does not shrink wherefore a rigid straight bar element 43, 44 is preferred in the channel portions 26, 27 of pillar portions 23 a, 23 b and strut portions 24 a, 24 b in the wall element 20 since fastening by means of a rigid bar element 43, 44 does not creep, which results in easy post-tensioning in pillar portion and strut portion. Such as mentioned above in connection to FIG. 1 the strut portion 24 a, 24 b is suitably post-tensioned prior to final assembly, either in factory or on the site.
The pillar portions 23 a, 23 b may according to an embodiment also be post-tensioned in each single wall element 20 in a factory combined with strong joints between the floor levels of the tower construction, the pillar portions 23 a, 23 b of the wall elements being releasably locked by means of the locking element 40 a. According to an embodiment bar elements 43 are therefore connectable in single positions or as a joint series of bars and finally lockable by threading devices, the threading device according to a variant being constituted by threads 43 a in the bar element 43 and nuts 43 b with threading adapted for the threads such as is apparent from FIG. 5 c. FIG. 8 a-b illustrate a variant for connecting bar elements in pillar channel portions which is applicable also in this embodiment. Preferably the pillar portions are post-tensioned on the site, preferably also from the bottom to the top, by bar elements 43 connected in series. Thereby work is made easier but above all it is facilitated to provide a final strain to the whole tower in an easy way, e.g. by means of a light weight and simple hydraulic tool, to a desired strain. No undesired lock creeping occurs, and for maximum rigidness after possible initial creeping of the bar element of steel during e.g. the first year, final strain may easily be achieved. This results in a considerably more stable connection and rigidness.
Hereby also dismantling of the wall elements of a tower construction 50 is facilitated such that the wall elements may be reused for building of a tower construction on e.g. a different location. This results in a suitable construction for towers of mobile antenna systems.
According to this embodiment three tower sections 30 are stacked on each other, wherein the respective tower section 30 is tapering upwardly such that the formed tower construction 50 is upwardly tapering. An advantage with an upwardly tapering tower construction is that it reduces moment and thereby dimensioned loads. Each wall element 20 of the tapering sections 30 has a trapezoidal shape with equal angle on the respective inclined side such that they get the shape of a truncated equally sided triangle. Alternatively the tower construction could be arranged to run vertically wherein the tower has straight section of which each wall element is rectangular. Alternatively the tower section could be formed by a mixture of tapered and straight tower sections, where a tapering tower section may be either upwardly or downwardly tapering. E.g. the lowermost tower section could be upwardly tapering and the uppermost tower section downwardly tapering and intermediate tower sections straight. The number of tower sections could be more of fewer than three. The height of the respective tower section may be the same or different.
By using releasable fasteners 40 a such as fittings the tower construction 50 may also be dismantled. According to an embodiment the tower construction has a height in the range of 25-50 m, e.g. about 40 m. Such a tower is suitable for mobile antenna systems. The tower construction may be constructed with any suitable height, i.e. also higher than 50 m if so desired. The tower construction has according to a variant a bottom diameter in the range of 3-7 m, preferably 4-6 m.
The tower construction is according to an embodiment configured such that the central/communication equipment of a mobile antenna system may be arranged uppermost in the tower construction, which prevents theft of the communication equipment, and simplifies wire laying and cooling of the entire system.
According to this embodiment such a bar element 43 is arranged in the respective pillar channel portion 26 or a bar element 43 arranged to run through two or more pillar channel portions 26. According to an alternative embodiment two or more bar elements are arranged in the respective strut channel portion 26, the bar elements being dimensioned for a certain load, wherein, according to a variant with several bar elements, the bar elements are thinner than if one bar elements would be used per pillar channel portion. The bar element may be arranged interconnected as a group or separately arranged in the respective channel portion.
FIG. 6 schematically illustrates a side view of a portion of a flat wall element 70 for a tower construction according to a second embodiment of the present invention, and FIG. 6 a-c schematically illustrate different cross sections A-A, B-B and C-C of the wall element in FIG. 6.
The flat wall element 70 is prefabricated. The wall element 70 is arranged to be cast in a mould which according to a variant is a reinforcement configuration. The mould has longitudinal recesses along the sides which in profile have a curved shape or loop-shape. By casting the reinforcement configuration in the mould a wall element 70 is obtained.
The wall element has an external side 70 a and an internal side 70 b. The wall element 70 is essentially constituted by a flat sheet portion 72, a pair of opposite sides of which one 70 c is shown, intended to run substantially horizontally in the tower construction and a pair of opposite sides 70 e, 70 f intended to run in a direction forming a predetermined angle to the horizontal plane in the tower construction. Said angle to the horizontal plane is according to an embodiment 90 degrees +/−30 degrees. According to an embodiment the opposite sides 70 e, 70 f of the wall elements are intended to run substantially vertical in the tower construction, i.e. perpendicular relative to the horizontal plane or with a certain inclination relative to the vertical plane.
The wall element 70 comprises compressive and tensile load absorbing pillar portions 73 a, 73 b running along the sides 70 e, 70 f. The wall element 70 is intended to be connected to adjacent wall elements. The wall element comprises compressive and tensile load absorbing strut portions 74 a running substantially horizontally along the sides 70 c of which one is shown, and preferably at least one intermediate strut portion 74 b, of which one is shown, running between the pillar portions and running substantially parallel to and at a distance from the strut portions 74 a running along the sides 70 c. Said strut portions 74 a, 74 b is referred to as the strut portions below.
The wall element 70 consequently constitutes a flat tetragonal module or cassette with dimensions adapted for the purpose. According to this embodiment the tetragonal wall element is rectangular. According to another embodiment the tetragonal wall element is trapezoidal-shaped, preferably with equal angle on the respective inclining side such that it gets the shape of a truncated equally sided triangle. The tetragonal wall element 70 has according to this embodiment a height being about three times its width. According to an embodiment the height of the wall element is in the range of 5-15 m, preferably 8-13 m.
The wall element 70 comprises a not shown reinforcement configuration which according to a variant comprises reinforcement net or the corresponding preferably having an extension or surface substantially corresponding to the shape of the mould, the reinforcement net constituting the reinforcement in the flat sheet portion 72. The reinforcement net thus has a substantially flat configuration.
The pillar portions 73 a, 73 b of the wall element 70 are internally cast in the wall element 70 and consequently arranged to run in a direction forming a predetermined angle to the horizontal plane in a tower construction, preferably arranged to run substantially vertically in a tower construction. The Strut portions 74 a, 74 b are internally casted in the wall element 70 and consequently arranged to run in a direction substantially horizontally in a tower construction.
The wall element 70 comprising pillar portions 73 a, 73 b and strut portions 74 a, 74 b is cast in accordance with the configuration of pillars and struts of the mould. The wall element 70 in addition comprises the casted flat sheet portion 72 reinforced with the reinforcement net. According to this embodiment the external side 70 a of the wall element 70 is essentially even and the internal side has enhancements formed by the pillar and strut portions.
The pillar portions 73 a, 73 b have through channel portions 76 a, 76 b running in its longitudinal direction. Said channel portions 76 a, 76 b are formed by the channel portions 73 a, 73 b having a loop-shaped cross section projecting from the sheet portion and having a curved portion outwardly from the long side of the sheet portion 72. Hereby the channel portion 76 a, 76 b running along the respective side of the wall element 70 is formed.
The reinforcement configuration comprises embedded reinforcement bars 78 running in the longitudinal direction of the pillar portions.
The reinforcement configuration comprises ring-shaped reinforcements 79 partly embedded in the pillar portions 73 a, 73 b transversally arranged along the respective pillar portion, a number of ring-shaped reinforcements 79 being arranged at a distance from each other along the pillar portion. The ring-shaped reinforcements 79 are arranged along the pillar portions in such a way that a pillar portion 79 a of the ring-shaped reinforcement projects over the channel portion wherein a projecting loop 79 a is formed which loop forms a circumferential opening with the channel portion 77. The embedded portion of the partly embedded ring-shaped reinforcement 79 is arranged to run around the reinforcement bar 78 running in the longitudinal direction of the pillar portion. The ring-shaped reinforcements 79 are vertically arranged in the pillar channel portions such that they form a series of loops with a c/c-measure varying depending on dimensioned loads.
The strut portions 74 a, 74 b have channel portions 77 running in the longitudinal direction. According to an embodiment the cannel portions 77 are constituted by tubular bars. According to another embodiment the channel portions are constituted by tubular channels formed during casting of tubes which after casting have been removed. This is explained in more detail below in connection to FIG. 7.
According to this embodiment the pillar portions 73 a, 73 b are bevelled, i.e. having grade along its respective external side, which sides constitute the pair of opposite sides 70 e, 70 f of the wall element. Hereby each pillar portion 73 a, 73 b increases gradually in width from its inner side to its outer side. The external grade or angle along the respective pillar portion 73 a, 73 b is adapted to the number of wall elements 70 being interconnected side to side in order to form a ring-shaped section as described in connection to FIGS. 7 and 9. The grade of the respective pillar portion is provided during casting by the mould having a corresponding shape.
The casted pillar portions 73 a, 73 b and strut portions 74 a, 74 b constitute reinforcements of the wall element 70 arranged to withstand compressive and tensile forces. The sheet portion 72 of the wall element 70 is according to this embodiment arranged to only handle smaller bracing forces and may therefore be made very thin such that the amount of concrete may be reduced considerably.
Easy transportation is facilitated by the flat shape of the wall element 70 in that these wall elements 70 easily may be stacked on each other and transported on e.g. a truck, a boat or the like. They take up little space and are not unwieldy. By the fact that the amount of concrete is reduced thanks to the thin sheet portions 72 they become relatively light weight and thus easy to handle.
According to a preferred embodiment each wall element 70 is made of high performance concrete with such properties that wall elements 70 with a sheet portion 72 with a thickness being thinner than the norm for covering layer, i.e. thinner covering layers on the respective side of the reinforcement net than 30 mm, the reinforcement net according to an embodiment being about 10 mm may be obtained. According to an embodiment the sheet portion of the wall element 70 is thus thinner in thickness than 70 mm.
The properties of the high performance concrete according to the present invention, the concrete of the wall element and tower construction 50, 100 according to the first and second embodiments of the present invention preferably being constituted thereof, are described in more detail in connection to FIG. 10 a-d below.
By using high performance concrete with the above mentioned properties a considerably lighter construction with maintained compressive and tensile strength properties, which further simplifies transport and assembly in rough terrain for manufacturing of towers for wind power plants is facilitated.
FIG. 7 schematically illustrates a plan view of a portion of two interconnected wall elements according to FIG. 6.
Each prefabricated wall element 70 is arranged to form one of several wall portions of circumferential shell portions 80 of one of several shell portions stacked on each other according to FIG. 9. The circumferential shell portions 80 form the ring-shaped tower section 80.
The wall elements 70 are arranged to be interconnected by arranging the external side of a pillar portion 73 a, 73 b of a wall element 70 to the external side of a pillar portion 73 b, 73 a of another wall element 70 such that they abut against each other such that the internal sides of the respective wall element 70 are angled towards each other.
The pillar portions 73 a, 73 b have a cross section such that when two long sides 70 a, 70 b of the wall element 70 abut against each other a through channel portion 76 is formed by the channel portions 76 a, 76 b facing each other by the thus interconnected pillar portions 73 a, 73 b.
The portion 79 a of the respective pillar portion projecting over the channel portion of the partly embedded ring-shaped reinforcements 79 transversely arranged along the respective pillar portion is arranged to overlap a corresponding projection portion 79 a of an abutting wall element 70 such that the respective loop 79 a overlaps the other loop 79 a, wherein a loop from the ring-shaped reinforcement 79 of a first wall element 70 extend inwardly towards the channel portion 76 a of the pillar portion 23 a of an adjacent second wall element 70 and the loop from the ring-shaped reinforcement 79 of the adjacent second wall element 70 extend inwardly towards the channel portion 76 b of the channel portion 73 b of the first wall element. Consequently ring-shaped reinforcements are transversely arranged along the respective wall element such that when two long sides 70 a, 70 b of the wall element 70 abut against each other several ring-shaped loops are formed of projecting portions of opposite reinforcements.
The pillar portions 73 a, 73 b is according to an embodiment dimensioned to withstand forces arising in tower constructions for wind power plants. Depending on size of aggregate and wings of wind power plants answering to dimensioned load (not weight of aggregate) the pillar dimensions varies with suitable measures normally between 200×200 mm to 300×300 mm. For mobile antenna towers they may naturally be dimensioned considerably slimmer as the most important thing for such towers is that they are rigid.
Removal of tubular element from the formed strut channel portion 77 is facilitated as in the first embodiment e.g. by the tubular element being waxed or lubricated prior to being embedded. Alternatively removal of the tubular element is facilitated by having the tubular element covered in plastic prior to being embedded.
Bar elements 94 are arranged to be inserted in the strut channel portions 77 for post-tensioning of wall elements 70. According to yet another embodiment the channel portion 77 is formed by means of a bar element 94 which is arranged to be embedded such that is post-tensioned, the channel portion already having a bar element inserted therein. According to an embodiment post-tensioning of strut portions 74 a, 74 b of wall elements 70 is obtained in a factory, i.e. the post-tensioning is prefabricated. According to another embodiment the post-tensioning of strut portions 74 a, 74 b of wall elements 70 is arranged to be provided after assembly. According to this embodiment the bar element is arranged to be tensioned/tightened by means of a nut 94 a. According to a variant the post-tensioning is provided by screwing by means of a hydraulic tool, which post-tensioning by the threading may be performed with less power than if corresponding struts are to be tightened. According to a variant the edge of the channel portion is arranged to resist the nut.
According to this embodiment a bar element 94 is arranged in the respective strut portion 77. According to an alternative embodiment two or more bar elements are arranged in the respective strut channel portion 77, the bar elements being dimensioned for a certain load, wherein, according to a variant with several bar elements, the bar elements are thinner than if one bar element is used per strut channel portion. The bar element may be arranged interconnected in a group or separately arranged in the respective channel portion.
FIG. 8 a schematically illustrates a side cross section of portions of wall elements according to FIG. 6, and FIG. 8 b schematically illustrates a side cross section of portion of two wall elements stacked on each other according to FIG. 6. FIG. 9 schematically illustrates a tower section 80 interconnected by wall elements according to FIG. 6.
The tower construction 100 is built up of tower sections 80 stacked on each other. Tower sections are obtained by interconnecting wall elements 70 according to above such that a ring-shaped section 80 is obtained. When two long sides 72 a, 72 b of the wall element 70 abut against each other a through channel portion is formed through the thus interconnected pillar portions as described above, i.e. that the respective channel portion 76 a, 76 b of the respective pillar portion 73 a, 73 b are facing each other such that said channel portion 76 is formed. Two pillar portions 73 a, 73 b arranged towards each other in that way form a pillar 73 with a through channel portion running in the longitudinal direction of the pillar. The prefabricated flat wall elements 70 are placed along each other such that a ring-shaped tower section 80 is formed. The ring-shaped tower section 80 is here constituted by identical flat wall elements 70 wherein a facet-shaped ring is obtained. According to this embodiment the number of wall elements 70 in a tower section is twelve, wherein the ring-shaped section has a dodecagonal cross section in the horizontal plane. Hereby the external bevel or grade of the sheet portion is 7,5 degrees.
Due to the fact that the respective wall element 70 is trapezoidal-shaped with equal angle on the respective inclining side such that they get the shape of a truncated equally sided triangle an upwardly tapering tower section is obtained, which reduces the moment and thereby dimensioned loads.
The number of wall elements 70 may according to alternative embodiments be more of fewer where more results in a more circular tower section and thus more stable from a strength point of view and lighter wall elements 70, and fewer results in fewer wall elements 70 which results in quicker assembly and fewer wall elements 70 to handle.
Due to the fact that the respective section 80 is tapering, the wall elements 70 of one section 80 to be stacked on another section is smaller in width than the wall element 70 of the section 80 below such that an upwardly tapering tower construction 100 is obtained.
The tower sections are arranged to be formed by stacking tower sections on each other, wherein wall elements according to FIG. 8 b are stacked on each other, wherein a lower end of the respective pillar portion 73 a, 73 b of the respective wall element 70 of the upper tower section 80 rests on an upper end of the respective pillar portion 73 a, 73 b of the lower tower section 70 wherein the upper and lower end of the respective pillar portion 73 a, 73 b according to a variant has a step such that they engage into each other for prevention of lateral sliding of the tower section, see FIG. 8 b. The pillar portions 73 a, 73 b of the lower tower section 80 are consequently arranged to support the upper tower section 80.
The sections 80 are thus arranged to be stacked on each other for forming of a tower construction 100 by aligning the respective pillar of the respective section with each other. Hereby each pillar of the respective section 80 forms a tower pillar such that the tower has a corresponding number of tower pillars, here twelve tower pillars, as the respective section. A through channel is thus formed running in the longitudinal direction of the respective tower pillar by means of the channel portion 76 formed in the pillars of the respective section by alignment of the pillars during stacking of the sections on each other.
The tower section further comprises bar elements 93 arranged to be inserted into the channel portions 76 for connecting the circumferential shell portions, i.e. the tower section 80 by means of the bar elements running in the pillar channel portions 76.
According to an embodiment bar elements 93 are of steel or other suitable material composition arranged to be lead through the respective through channel portion 76 extending in the longitudinal direction of the tower pillar. Thereafter concrete y1 is arranged to be filled in the respective channel portion such that a permanent locking of the wall element 70 and the sections 80 is provided with bar elements 93 and said ring-shaped reinforcements through which overlapping ring-shaped loops bar elements 93 are arranged to be introduced. In such a way the tower construction 100 is permanently locked and a very stable construction is obtained. Hereby no welding is required. Such a construction with tower pillars with through channels running in its longitudinal direction results in a simple solution which may be controlled from factory and where the tower construction then easily may be built on the site.
According to an embodiment each bar element is rotatably arranged in the respective channel portion. Hereby according to an embodiment a hollow tubular element is arranged to be embedded in the respective channel portion 76, forming a channel dimensioned such that bar elements may be introduced and rotated in the channel.
According to an embodiment the tubular element is removably embedded in the channel portion. According to an embodiment the tubular element is waxed, lubricated, or treated with another suitable agent which does not stick to or is locked by concrete prior to being embedded, which facilitates removal of the tubular element such that it may be removed such that a channel formed by the concrete cast in the pillar portion is formed, dimensioned such that the bar element may be introduced and rotated in the channel. Alternatively removal of the ring-shaped element is facilitated by having the tubular element covered in plastic prior to it being embedded. Any suitable means for providing. According to these embodiments the tubular element does not need to be hollow.
According to an embodiment an upper axially extending end portion and a lower axially extending end portion of the tubular element a bigger circumference, i.e. diameter, than the remaining portion of the tubular element running there between. Hereby a channel 77′ of the pillar portion is obtained when removing the tubular element which has a greater circumference along an upper portion 77′a and along a lower portion 77′b of the channel. Through this solution easy post-tensioning of introduced bar elements is facilitated.
Such a solution is advantageously used also during connection of tower construction by means of the bar elements according to the first embodiment of the present invention.
The pillar portions 73 a, 73 b are consequently according to an embodiment also arranged to be post-tensioned in each single wall element 70 in factory combined with strong joints between the different floor levels of the tower construction. According to an embodiment bar elements 93 are therefore in single positions or as an interconnected series of bar elements 93 connectable and finally lockable by threading devices, the threading devices according to a variant being constituted by threads 93 a in bar elements 93 and nuts 93 b with threading adapted for the threads such as is apparent from FIG. 8 a-b.
The threads of the respective bar element is preferably adapted such that when the bar element is arranged through a pillar portion 73 a, 73 b of a wall element, alternatively through two or several pillar portions of wall elements 70 of tower sections 80 stacked on each other, the thread has an extension corresponding to the wider part of the channel 77′ surrounded by concrete y1. A bar element may thus have a length corresponding to a one pillar portion, two pillar portions or several pillar portions, the respective end of the bar element having threads corresponding to the extension of the wider portion 77′a, 77′b of the channel 77.
The respective nut 93 b preferably has an extension corresponding to the double extension of the wider portion 77′a, 77′b in the channel 77. When a bar element is arranged in the channel portion, i.e. the channel such that the threads of the bar element are present at the level of the wider portion of the channel and the nut is screwed thereon, the nut 93 b will project corresponding to the length of a wider portion of the channel in a pillar portion. Hereby the projection portion of the nut 93 b is during stacking of an additional tower section arranged to be introduced in a wider portion of the channel of a pillar portion of the tower section stacked thereon, wherein a bar element may be introduced through it and threaded to the nut for post-tensioning.
Preferably the pillar portions are post-tensioned on the location, preferably also from the bottom to the top, by bar elements 93 connected in series. Thereby the work is made easier but above all it is facilitated to provide a final tensioning to the entire tower construction 100 in an easy way, e.g. by means of a light weight and simple hydraulic tool, to a desired tension. No lock creeping which is hard to handle occurs, and for maximum rigidity after possible initial creeping of the bar element of steel during e.g. the first year final strain may easily be obtained. This results in a considerably more stable connection and rigidity.
According to a variant some bar elements at the time are connectably strained, and by the fact that the forces decrease higher up in the tower construction the bar elements are adapted to the actual forces decreasing with height since the moment becomes less. According to an embodiment the bar elements, preferably comprising steel, are consequently dimensioned after the forces they are arranged to absorb such that the dimension of bar elements and/or the dimension on the pillars and struts higher up in the tower construction are dimensioned to absorb less force than bar elements in lower tower sections, which reduces the material consumption.
Hereby tower sections for forming of the tower construction may be connected by means of post-tensioned bar elements and/or by means of concrete added to the channel portions for fixing tower sections by casting.
According to an embodiment of the tower construction 100 according to the second embodiment, ten sections 80 are stacked on each other, wherein the respective section 80 is upwardly tapering. The respective wall element 70/section 80 is according to this embodiment 10 m high such that the tower construction 100 becomes 100 m high. The tower construction may of course be built to desired height.
The tower construction 100 is according to an embodiment configured such that it is arranged to support the turbine of a wind power plant and thus constitutes a tower for a wind power plant. According to an embodiment the height of the tower construction is in the range of 60-140 m, but higher towers are possible to obtain. The tower construction has according to a variant a bottom diameter in the range of 4-8 m, preferably 5-7 m.
According to this embodiment a bar element 93 is arranged in the respective pillar channel portion 76 or a bar element 93 is arranged to run through two or more pillar channel portions 76. According to an alternative embodiment two or more bar elements are arranged in the respective strut channel portion 76, the bar elements being dimensioned for a certain load, wherein, according to a variant with several bar element, the bar elements are thinner than if one bar element is used per pillar channel portion. The bar elements maybe arranged interconnected in a group or separately arranged in the respective channel portion.
Above different variants for tensioning strut portions 24 a, 24 b; 74 a, 74 b and pillar portions 23 a, 23 b; 73 a, 73 b of a tower section 50, 100 by means of bar elements 43; 93, 44; 94, and connecting tower section 30; 80 of tower constructions 50, 100 by means of bar elements, have been described. Post-tensioning of strut portions and pillar portions may, as mentioned, be provided in different ways. One way is that it is made in factory, both in pillar portion and strut portion. Another way is to leave post-tensioning in pillar portions to after assembly of a tower section 30; 80 and thus connect several tower sections stacked on each other. According to a variant some wall elements are stretched at a time and by the fact that the forces are reduced upwardly the bar elements are adapted to the actual forces reducing with height since the moment becomes smaller. According to another variant the bar elements have the same dimension and are stretched from the bottom to the top, which has the advantage that if then, e.g. after one year a need exists for additional stretching due to the steel of the bar element creeping and slacken. The bar element 44; 90 in the strut portions are straight and stretchably arranged in strut portions of the respective wall element 20; 70. The advantage with a straight bar element is that it reduces the number of tensions and stretches, it is possible to stretch easy and precise with nuts without creeping, and they may be post-tensioned by screwing.
Above wall elements 27, 70 for forming of tower constructions 50, 100 for mobile antenna systems and wind power plants have been described. By means of a wall element 20, 70 according to the present invention a waste silo or manure well could be constructed.
Above wall elements 20; 70 have been described arranged to form one of several wall portions of circumferential shell portions 30; 80 of a tower construction 50; 100 formed by several shell portions stacked on each other. However, any suitable building construction may be provided by means of the wall elements according to the present invention, such as the shell of a multi-story building, where the strut portions according to a variant may constitute beams for floor levels. The wall elements need not be of the same size. Any suitable tower shape or other building shape may be provided with the device, wherein the ring-shaped section may be a regular or irregular polygon. The ring-shape may have any suitable cross section such as triangular, square, rectangular, pentagonal, hexagonal, etc. or an irregular cross section.
FIG. 10 a-d show different measured data of high performance concrete y1 according to the present invention compared to conventional concrete y2.
The high performance concrete according to the present invention is composed of cement and ballast with a water-cement-number, vct, i.e. weight ratio between amount of water and amount of cement, being lower than 0.39, wherein all added water has been chemically bound during hardening into concrete and where all capillary pores vanished into the cement paste. A low vct-number results in the cement matrix becoming stronger and denser. By these improvements in properties the sheet portion may be made water, salt and acid proof.
According to a variant the cement constitutes 20-30% of the high performance concrete and ballast 55-75% of the high performance concrete. The high performance concrete is composed of 5-15% water, with vct<39.
Ballast comprises slag and/or stone and/or sand. According to a preferred embodiment the ballast comprises sharp sand which according to an embodiment constitutes 10-20% of the high performance concrete. The cement comprises according to an embodiment fine material such as micro silica, aerogel and similar materials. According to an embodiment the fine material constitutes 1-5% of the high performance concrete.
The high performance concrete according to an embodiment of the present invention is consequently composed of smaller admixtures of material with good grip zones, i.e. material having a rough configuration/surface, are uneven, e.g. with craters or the corresponding, such as aerosol and/or sharp sand and/or mineral fibre such as carbon fibre, silicate fibre, or basalt fibre, mixed in cement to a certain composition. According to an embodiment the high performance concrete y1 is according to the present invention composed with an admixture of 10-20% sharp sand, and/or 1-5 percentages by volume of aerogel and/or slag in glass phase and/or mineral fibres such as carbon fibre, silicate fibre, or basalt fibre. Hereby a high performance concrete is obtained with such properties that the tensile strength increases, at least doubled, which totally surprisingly means that the high performance concrete becomes fire proof.
All in all means that a long-term constructive sheet with a thickness down to only about 20 mm, i.e. far below the norm for covering layers may be created, serving to protect the reinforcement steel from corroding by water, salt and acid penetration or quickly lose its strength during a fire.
Fire tests have been performed on the high performance concrete y1 according to the present invention. The test was performed on the national testing laboratory in Borås, Sweden. Two pillars of the high performance concrete 71 were tested against fire according to SIS 02 48 20 during 122.5 minutes. Bothe pillars kept the load-bearing capacity during the entire test.
The properties of the concrete are improved by increasing the density of the cement paste and cooperation with ballast material. Thereby is obtained an increased compressive and tensile strength, good water-tightness but at the same time good diffusion-openness, higher aging durability, high carbonation and chloride resistance, high adhesiveness and that the concrete is shrink free during hardening.
The high performance concrete according to the present invention results in increased flexural strength from in the best case today 5-7 MPa to 10-15 MPa with possibility to doubling of compressive strength of normal concrete. By the fact the water cement number, vct, at the same time may be made low, the small amount of released steam is all of a sudden not able to split the material during fire.
Compressive and flexural strength tests were made on high performance concrete y1 according to the present invention and as a comparison normal concrete 72, the following results being obtained after 28 days.
High Performance Concrete y1 According to the Present Invention:
Compressive strength after 28 days 95 MPa

Flexural strength after 28 days 12.5 MPa

Normal Concrete y2:


	Compressive strength after 28 days	45 MPa
	Flexural strength after 28 days	12.5 MPa

FIG. 10 a-d show tests of high performance concrete according to the present invention, denoted y1, and conventional concrete, denoted y2 below.
FIG. 10 a shows tests of shrinking on 40×40×160 mm samples with dowels on both sides of high performance concrete according to the present invention and normal concrete y2. The length was measured with a Graf-Kaufman apparatus. After 6 months no notable shrinkage of the high performance concrete y1 according to the present invention was noted unlike normal concrete y2.
FIG. 10 b shows water absorption through capillary suction, where the test was performed according to Swedish standard on high performance concrete y1 according to the present invention and normal concrete y2. Hereby is apparent that the water-proofness of the high performance concrete y1 according to the present invention is substantially higher than normal concrete y2.
FIG. 10 c shows freezing and thawing in acid and chloride based solution where the test was performed according to ASTM 666, which is a standard test method for concrete resistance, on high performance concrete y1 according to the present invention and normal concrete y2. The test shows that the chloride resistance of the high performance concrete y1 according to the present invention is considerably higher than normal concrete y2.
FIG. 10 d shows a special test of freezing and thawing in a mixture of equal parts of formic acid, lactic acid and acetic acid with pH 3, on high performance concrete y1 according to the present invention and normal concrete y2. The test shows that the acid resistance of the high performance concrete y1 according to the present invention is considerably higher than normal concrete y2.
The degree of carbonation was measured by changing the test bodies in the tests above, wet them with water and spray a phenolphthalein solution over the surfaces. Carbonated surfaces do not become pink-coloured. The carbonation depth for y1 after 6 months was measured to 1-1.5 mm. This shows that the concrete has a very low permeability which explains the low water absorption and high ability to resist salt and acids.
By using high performance concrete in the wall element 20, 70 according to the present invention it is facilitated to obtain a thickness of the sheet portion 22, 72 of the wall element 20, 70 down to 20 mm with maintained fire protection avoiding capsizing and maintained waterproofness avoiding corrosion.
Due to the fact that the concrete of the wall elements 20, 70 according to the present invention are constituted by high performance concrete y1 according to above, and the compressive and tensile load absorbing pillar portions 23 a, 23 b; 73 a, 73 b thereby being produced in high performance concrete the pillar portions may absorb a considerably higher compressive load than conventional concrete, more than 70 MPa in pressure load. The pillar and strut portions may therefore be dimensioned to take all existing vertical and horizontal compressive and tensile forces of the tower construction 50, 100 while the relative to the pillar and strut portions thin sheet portions 22, 72 only answers for bracing.
The tower construction according to the present invention with high performance concrete according to the present invention thus gets a considerably better strength than with conventional concrete. In e.g. a wind power tower the total capacity needs to be calculated according to the ability of the tower construction to withstand tensile forces on one side and equal size of compressive forces on the opposite side.
A pillar portion 73 a, 73 b with a compressive strength of e.g. 80 MPa is post-tensioned by 40 MPa. The side of the tower construction 100 being subjected to tensile load is to be withstood by the tensile strength existing in the bar elements 93, preferably of steel, arranged in the pillar portion, while the compressively loaded opposite side of the tower construction 100 is to be withstood by the compressive forces remaining in the high performance concrete y1, i.e. 40 MPa. Consequently, if the high performance concrete y1 can withstand a compressive load of 140 MPa, 70 MPa remains when post-tensioning of the bar element 93 is performed.
All pillar portions in a tower construction withstands the same loads since tensile loaded and compressive loaded pillars respectively varies with the wind direction. The same naturally holds also for the strut portions.
The foregoing description of the preferred embodiments of the present invention has been provided for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Obviously, many modifications and variations will be apparent to practitioners skilled in the art. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications, thereby enabling others skilled in the art to understand the invention for various embodiments and with the various modifications as are suited to the particular use contemplated.

Claims

1. A prefabricated wall element for a tower construction, comprising:

a wall element essentially of concrete, arranged to form one of several wall portions of a building formed by circumferential shell portions of one of several shell portions stacked on each other,

the wall element being constituted by substantially a flat sheet portion comprising a pair of opposite sides intended to run substantially horizontally in the building and a pair of opposite sides intended to run in a direction forming a predetermined angle to the horizontal plane in the building, and along which sides the wall element includes compressive and tensile load absorbing pillar portions and is intended to be connected to adjacent wall elements.

2. A wall element according to claim 1, wherein the wall element further comprises a substantially horizontally running compressive and tensile load absorbing strut portions.

3. A wall element according to claim 1, wherein the pillar portions comprises pillar channel portions running in the longitudinal direction of the pillar portion.

4. A wall element according to claim 1, wherein the strut portions comprises strut channel portions running in the longitudinal direction of the strut portion.

5. A wall element according to claim 1, wherein said circumferential shell portions are connected by means of rigid bar elements running in the channel portions.

6. A wall element according to claim 5, wherein said bar elements are stretchably arranged in the pillar channel portions.

7. A wall element according to claim 4, wherein at least one rigid bar element is stretchably arranged in the respective strut channel portion.

8. A wall element according to claim 1, wherein the pillar portions of the wall elements are arranged to be releasably locked to adjacent pillar portions of wall element by means of locking elements for the formation of said building.

9. A wall element according to claim 3, wherein the wall elements are arranged to be connected by means of cast concrete in the channel portions.

10. A wall element according to claim 1, wherein the concrete of the wall element is high performance concrete composed of cement and ballast with a weight ratio between amount of water and amount of cement, vct, being lower than 0,39.

11. A wall element according to claim 10, wherein the composition of the high performance concrete comprises a mixture of 10-20% sharp sand, and/or 1-5 percentage by volume of aerogel and/or slag in glass phase and/or mineral fibres such as coal, silicate and/or basalt fibre.

12. A wall element according to claim 10, wherein said high performance concrete has a tensile strength greater than 10 MPa.

13. A wall element according to claim 10, wherein said high performance concrete has a compressive strength greater than 70 MPa.

14. A wall element according to claim 1, wherein the pillar portions have an extension in the range of 5-15 metre.

15. A tower construction comprising:

at least one prefabricated wall element comprising a wall element essentially of concrete, arranged to form one of several wall portions of a building formed by circumferential shell portions of one of several shell portions stacked on each other,

16. A mobile antenna system comprising:

a tower construction including at least one prefabricated wall element comprising a wall element essentially of concrete, arranged to form one of several wall portions of a building formed by circumferential shell portions of one of several shell portions stacked on each other,

the wall element being constituted by substantially a flat sheet portion comprising a pair of opposite sides intended to run substantially horizontally in the building and a pair of opposite sides intended to run in a direction forming a predetermined angle to the horizontal plane in the building, and along which sides the wall element includes compressive and tensile load absorbing pillar portions and is intended to be connected to adjacent wall elements,

and communication equipment arranged in the upper part of the tower construction.

17. A mobile antenna system according to claim 16, wherein the tower construction has a height in the range of 25-50 m.

18. A wind power plant comprising:

a turbine,

a plurality of turbine blades connected to the turbine, and

a tower construction arranged to support the turbine,

the tower construction including at least one prefabricated wall element comprising a wall element essentially of concrete, arranged to form one of several wall portions of a building formed by circumferential shell portions of one of several shell portions stacked on each other,

19. A wind power plant according to claim 18, wherein the tower construction has a height in the range of 60-140 m.

20. A wall element according to claim 14, wherein the pillar portions have an extension in a range of 8-13 m.