EP3356611A1

EP3356611A1 - Fibre composite section and assembly

Info

Publication number: EP3356611A1
Application number: EP16852191.2A
Authority: EP
Inventors: David OLIVEGREN
Original assignee: Modvion AB
Current assignee: Modvion AB
Priority date: 2015-10-02
Filing date: 2016-09-30
Publication date: 2018-08-08
Also published as: EP3356611A4; WO2017058095A1

Abstract

Fibre composite section for a self-supporting assembly, where the fibre composite section comprises a plurality of laminated fibre composite layers, where a fibre composite section comprises an upper part and a lower part, where the edges of the upper and lower part comprises rabbets directed in different directions, where the rabbets of the upper part are adapted to cooperate with rabbets of the lower part of another fibre composite section when a plurality of fibre composite sections are assembled to an assembly. The advantage of the invention is that a self-supporting assembly can be obtained in an easy and cost-effective way.

Description

FIBRE COMPOSITE SECTION AND ASSEMBLY TECHNICAL FIELD

The present invention relates to a fibre composite section adapted to be used in a self-supporting assembly, comprising a plurality of fibre composite sections. The self-supporting assembly may e.g. be a wooden tower or a wooden wall. Each fibre composite section comprises a plurality of laminated layers, where each layers may be a block board made from a plurality of wooden boards and where the layers are cross laminated, or where a layer is a fibre composite layer, preferably a fibre composite layer having a single fibre direction.

BACKGROUND ART

High towers are used for a number of different purposes. They may e.g. be used as transmitter masts or for wind power installations. A typical wind power installation is provided with a tower made of steel or concrete. The tower is attached to the ground by a foundation and the tower is provided with a nacelle at the top of the tower, holding the generator, the transmission and the rotor blades. A steel tower is normally assembled by steel rings either bolted together or welded to each other. A concrete tower may be assembled from concrete parts joined together or may be made by sliding form casting.

These conventional towers work well but have some disadvantages. One disadvantage is that they are heavy. A heavy tower requires a very stable foundation, which in turn requires a lot of e.g. concrete. Due to efficiency, the wind power installations are often built in areas lacking roads, which complicate the transport of material to the site. Since large amounts of material are required for a tower, extensive transportation is required. A further disadvantage is when the life time of a tower is reached and the tower must be pulled down. In this case, all material must be handled and transported again.

A wooden tower has been proposed in WO2010121733. The proposed tower is built by using an inner frame, to which plane elements are attached using connection means. The plane elements are made from laminated plywood and/or wood composite materials.

There is further an increased interest in building higher and larger buildings using wood. A normal wooden building usually comprises a wooden frame made from wooden beams, which are thereafter covered with e.g. panels or plasterboards. A wooden beam may be a solid wooden piece or may be made from glued laminated timber, which allows for longer and thicker wooden beams. By using glued laminated timber beams, it is possible to build buildings having more than six floors. However, it is time consuming to assemble all the beams and cross beams and then to attach the covers on the inside and the outside of the frame.

A practice that is becoming more and more popular is to use engineered wood products for larger buildings. Engineered wood is comprised of wood veneers, lumber, panels, fibres or strands bound together with an adhesive. Generally, engineered wood is more dimensionally stable and consistent than solid wood. Common engineered wood products are laminated veneer lumber (LVL), oriented strand board (OSB), plywood (both hardwood and softwood), parallel strand lumber (PSL), finger-jointed lumber and cross-laminated timber (CLT).

Especially parallel strand lumber and cross-laminated timber are well suited for larger constructions. Parallel strand lumber is well suited for beams and columns in post-and-beam construction, and for beams, headers, and lintels in light framing. Cross-laminated timber is well suited for long spans in floors, walls or roofs, and may also be made as wide as practical. Cross-laminated timber is thus also suitable for self-supporting walls.

One problem with all these techniques is to join two or more wood elements to each other without losing strength and stability. The joint between two wood elements may reduce the strength of a wooden construction considerably. One way of avoiding joints is to produce the wooden construction in one piece, which may lead to a complicated and expensive transport of the wooden construction. Another way is to use e.g. metal support structures at the joint between two wooden parts.

These and other known solutions may work well in some circumstances, but there is still room for an improved self-supporting wooden assembly made from a plurality of wooden sections. DISCLOSURE OF INVENTION

An object of the invention is therefore to provide an improved fibre composite section for a self-supporting assembly. A further object of the invention is to provide an improved fibre composite assembly comprising a plurality of such fibre composite sections. A further object of the invention is to provide an improved fibre composite tower comprising a plurality of such fibre composite sections. A further object of the invention is to provide a method for assembling an improved fibre composite tower.

The solution to the problem according to the invention is described in the characterizing part of claim 1 for the fibre composite section, in claim 13 for the fibre composite tower and in claim 15 for the method of assembling a fibre composite tower. The other claims contain advantageous embodiments and further developments of the fibre composite section, the fibre composite tower and the method. In a fibre composite section for a self-supporting assembly, where the fibre composite section comprises a plurality of laminated fibre composite layers, the object of the invention is achieved in that a fibre composite section comprises an upper part and a lower part, where the edges of the upper and lower part comprises rabbets, where the rabbets of the upper part are directed in a first direction relative the outer surface of the fibre composite section, and where the rabbets of the lower part are directed in the opposite direction relative the outer surface of the fibre composite section, and where rabbets of the upper part of a fibre composite section are adapted to cooperate with rabbets of the lower part of another fibre composite section when a plurality of fibre composite sections are assembled to a circular assembly.

The fibre composite sections are intended for building purposes, such as towers, cisterns, floor framings, walls and other building designs, where the complete building structure cannot be assembled at one place and transported to the building site, since the complete building structure is too large for transportation on roads or trains. Instead, the building structure is manufactured in sections that are assembled at the building site. Due to the inventive joints, the assembled building structure will have the same strength as a building structure built on site.

A fibre composite material is formed by a matrix (resin) and a reinforcement of fibers. Preferably, bio composite fibers are used. They are divided into two groups: non-wood fibers or natural fibers and wood fibers. Wood fibers comprise cellulose and lignin. Wood, and especially spruce or pine, is a cheap and strong material suitable to be used for cross lamination.

Other fibers may also be used, such as bamboo fibers, which may be laminated into larger sheets. They are preferably laid out with the fibers in one direction, such that cross laminated sections may be obtained. Other bio fibers may also be used. When wood is used, a wood section comprises a plurality of cross laminated wooden layers, where a wooden section comprises a plurality of longitudinal wooden layers directed in the longitudinal direction of the wooden section, and a plurality of cross wooden layers, where each wooden layer comprises a block board made from a plurality of wooden boards. Sections made from other fibre composite materials preferably also comprise laminated layers, where each layer comprises fibres directed substantially in one direction. By using such layers, cross lamination will provide a strong section. In this description, wood will be used as an example of a fibre composite. Other fibre composite materials, and especially fibre composite materials having a single fibre orientation, may also be used. Even fibre composite materials having a non-singular fibre orientation are suitable for assembling e.g. a tower from a plurality of fibre composite sections. By this first embodiment of the wooden section according to the invention, a wooden section adapted to be used in a self-supporting wooden assembly such as a tower is provided. By mounting a plurality of wooden sections to each other, where the rabbets of the upper part of a wooden section cooperates with the rabbets of the lower part of an adjacent wooden section, the wooden sections will lock to each other. By joining the rabbets to each other with glue and screws, a self-supporting wooden tower is provided. Due to the cross lamination with relatively thick wood layers made from block boards, the wooden tower will be able to withstand loads acting from any direction. The longitudinal wooden layers will mainly handle vertical loads, both pushing and pulling loads. The cross wooden layers will help to handle twisting loads acting on the tower. Since all layers are securely joined to each other, the wooden sections will be able to handle high loads. A wooden section is produced by joining several layers with block boards to each other using a suitable adhesive. The layers are pressed together in a press, where the wooden section is further shaped to the required shape in the same pressing step. The rabbets of the wooden section are thereafter shaped by a precision router, such that relatively small tolerances are obtained. The small tolerances help to improve the stiffness and rigidity of an assembled wooden assembly.

The wooden sections may divide the circumference of the wooden assembly in four, six, eight or more parts, depending mainly on the size of the assembly. It is preferred to use as few sections as possible for a wooden tower, which means that the maximal size of a wooden section will be limited by the possibility to transport the wooden sections to the building site. A wooden section may thus be up to thirty meters long. A further limiting factor is the handling of the wooden sections. It is more practical to use wooden sections with a length between fifteen to twenty meters. Wooden towers of different sizes may be constructed with the inventive method. However, the inventive method is mainly advantageous for wooden tower of 50 meters and more, and is well suited for wind power towers of up to 150 meters and more. Also the width of a wooden section may be limited by the transportation of the wooden sections. It may thus be of advantage to divide the circumferential in more than four parts. The wooden tower may be straight or may be provided with tapered walls, such that the wooden tower is shaped as a truncated cone.

A wooden section will comprise an odd number of wooden layers. The outermost and innermost wooden layer will be longitudinal wooden layers, and every second layer will also be a longitudinal wooden layer. Between the longitudinal wooden layers, cross wooden layers are arranged. The cross wooden layers are angled between 30 to 90 degrees relative the longitudinal wooden layers, and are preferably angled between 45 to 60 degrees. Preferably, a first cross wooden layer is directed to the left, and the next cross wooden layer is directed to the right. A wooden section preferably comprises at least five wooden layers.

Each wooden layer is made from a block board, which comprises a plurality of boards. A longitudinal wooden layer may be between 20 - 80 mm thick, and is preferably between 40 - 60 mm thick. A cross wooden layer may be between 10 - 40 mm thick, and is preferably between 15 - 30 mm thick. The cross wooden layer is thinner since it must be bent against the fibre direction of the wooden boards. A wooden section is preferably thicker than 160 mm or more, depending on the height of the wooden assembly and on the loads that will act on the wooden assembly.

A wooden tower will be self-supporting. There is thus no need for a frame or any stabilizers inside the wooden tower. This means that the inner room of the wooden tower can be used for a lift or stairs. At the bottom of the wooden tower, the wooden tower is attached to a foundation. The foundation may be e.g. a steel construction to which the lowermost wooden sections are attached by hexagon head wood screws. Preferably, a climate system is installed inside the wooden tower, which will control the humidity of the wood. Any other equipment such as sensors or cable shafts can easily be installed by using wood screws. In another embodiment of a wooden section according to the invention, a wooden section adapted to be used in a self-supporting flat wooden assembly is provided. By mounting a plurality of wooden sections to each other, where the rabbets of the upper part of a wooden section cooperates with the rabbets of the lower part of an adjacent wooden section, the wooden sections will lock to each other. By joining the rabbets to each other with glue and screws, a self-supporting wooden assembly is provided. Due to the cross lamination with relatively thick wood layers made from block boards, the wooden assembly will be able to withstand loads acting from any direction. The longitudinal wooden layers and the cross wooden layer will be able to handle loads in all directions. Due to the novel way of joining several wooden sections to each other, both in a longitudinal direction and in cross direction, the complete wooden assembly will be able to handle loads in all directions in a secure way.

A wooden section is produced by joining several layers with block boards to each other using a suitable adhesive. The layers are pressed together in a press in a known manner. The rabbets of the wooden section are thereafter shaped, preferably by a precision router, such that relatively small tolerances are obtained. The small tolerances help to improve the stiffness and rigidity of an assembled wooden assembly. It would also be possible to use a saw to form the rabbets.

In one example of the inventive wooden section, the end edge of the upper part comprises a rabbet directed in the first direction and that the end edge of the lower part comprises a rabbet directed in the second direction. In this way, all rabbets of an upper or lower part are directed in the same direction. This will simplify the assembly of a wooden assembly, since a wooden section can be mounted to another wooden section from one direction. In another example of the inventive wooden section, the end edge of the upper part comprises a tongue and the end edge of the lower part comprises a groove. In this way, an improved end joint is provided which will simplify the mounting of several wooden sections to each other.

In another example of the inventive wooden section, the rabbets of the side edges comprise an additional rabbet, such that a double or stepped rabbet is obtained. In this way, the contact surface between two adjacent rabbets will increase, which will improve the strength of an assembled joint

A wooden section will comprise an odd number of wooden layers. In one example, an inventive wooden section comprises three wooden layers. The outermost and innermost wooden layer will be longitudinal wooden layers, and the middle layer will be a cross wooden layer arranged with an angled of 90 degrees relative the longitudinal wooden layers. It is also be possible to use more than three layers, such as five layers or seven layers for very large wooden constructions. When more than three layers are used, it is possible to have an angle differing from 90 degrees between the longitudinal layers and the cross layers, such as an angel between 45 to 60 degrees. In this case, the first cross wooden layer is directed to the left, and the next cross wooden layer is directed to the right. Each wooden layer is made from a block board, which comprises a plurality of boards. A longitudinal wooden layer may be between 20 - 80 mm thick, and is preferably between 40 - 60 mm thick. A cross wooden layer preferably has the same thickness, but may be somewhat thinner or thicker. A wooden section is preferably thicker than 80 mm or more, depending on the size of a wooden assembly and on the loads that will act on the wooden assembly.

The wooden assembly will be self-supporting. There is thus no need for a frame or any other stabilizers supporting the wooden assembly.

BRIEF DESCRIPTION OF DRAWINGS The invention will be described in greater detail in the following, with reference to the embodiments that are shown in the attached drawings, in which

Fig. 1 shows an outer side view of a first embodiment of a fibre composite section according to the invention, Fig. 2 shows an inner side view of a fibre composite section according to the invention,

Fig. 3 shows a schematic view of the different layers of a wooden section according to the invention, Fig. 4 shows an example of a wooden tower comprising a plurality of wooden sections according to the invention,

Fig. 5 shows an example of a wind power tower according to the invention,

Fig. 6 shows another example of a fibre composite section according to the invention,

Fig. 7 shows a further example of a fibre composite section according to the invention, and

Fig. 8 shows an example of a fibre composite assembly according to the invention.

MODES FOR CARRYING OUT THE INVENTION

The embodiments of the invention with further developments described in the following are to be regarded only as examples and are in no way to limit the scope of the protection provided by the patent claims. The directional references used refer to directions of a wooden section when used in a wooden tower. Wood will be used as an example of a fibre composite. Other fibre composite materials, and especially fibre composite materials having a single fibre orientation, may also be used. Even fibre composite materials having a non-singular fibre orientation are suitable for assembling e.g. a tower or a wall from a plurality of fibre composite sections.

Fig. 1 shows an outer side view of a wooden section according to the invention, and Fig. 2 shows an inner side view of a wooden section according to the invention. The wooden section is in this embodiment semi-circular in a radial direction and straight in a longitudinal direction. A projection of a wooden section from the outer surface will resemble a rectangle where the long sides are either parallel or are somewhat inclined. Straight wooden sections are preferred for straight wooden assemblies, and inclined wooden sections are preferred when a wooden tower having a shape of a truncated cone is to be obtained. By assembling a plurality of wooden sections, a self-supporting wooden tower is obtained. A wooden section is made from relatively thick wood layers made from block boards which are cross laminated. In this way, a strong and rigid wooden section is obtained. An assembled wooden tower will be able to withstand loads acting from any direction. In the shown example, the wooden section is straight with somewhat inclined or tapered side edges. The wooden section may also be provided with parallel side edges, such that a straight wooden tower will be obtained. In the shown examples, a wooden tower will be used as an example of a wooden assembly.

A wooden section 1 is provided with an outer surface 2 and an inner surface 3. The wooden section comprises an upper part 4 and a lower part 5. The wooden section is provided with rabbets 6 along the side edges 9, the upper edge 12 and the lower edge 13 of the wooden section. The upper part 4 is provided with rabbets 6 pointing in one direction, and the lower part 5 is provided with rabbets 6 pointing in an opposite direction. In the shown example, the rabbets of the upper part are directed outwards, and the rabbets of the lower part are directed inwards. The height of the upper part equals the height of the lower part. The size of the rabbet, i.e. the width and the thickness of the rabbet, of the upper part equals the size of the rabbet of the lower part. Rabbets of two adjacent wooden sections will thus provide a half joint where the inner and outer surfaces will correspond to each other, such that a smooth surface is obtained. A rabbet is provided with a rabbet edge 7, which is the side of the rabbet being parallel to the outer or inner surface of the wooden section. A rabbet is further provided with a rabbet bottom 8, which is the side perpendicular to the rabbet edge. A wooden section may also be provided with other types of joints. The upper edge 12 and lower edge 13 may e.g. be provided with a tongue or a groove, such that a tongue and groove joint is obtained between a lower edge of one wooden section and an upper edge of another wooden section. Other joints are also possible. It would be possible to provide the side edges with other types of joints as well. It is e.g. possible to provide the side edges with a double or stepped rabbet, such that a rabbet will be provided with two rabbet edges provided at different heights, and two rabbet bottoms provided at different widths. Other joints are also possible, but it is preferred to have a joint that is open in one direction, such that a wooden section can be mounted to another wooden section from an outer direction.

A wooden section will comprise wooden layers oriented in different directions, i.e. the wood fibres are directed in different directions. This is often referred to as cross lamination or cross laminated timber. Glued laminated timber is well known and is used for larger structural wooden members, where all wood fibres are parallel. In cross lamination, every other wooden layer will be directed in another direction, normally 90 degrees when flat boards are manufactured. Preferably, the cross lamination in the inventive wooden section will be angled at an angle differing from 90 degrees. The longitudinal wooden layers will mainly handle vertical loads, both pushing and pulling loads. The cross wooden layers will help to handle twisting loads acting on the tower. Since all layers are securely attached to each other, the wooden sections will be able to handle high loads in different directions.

A wooden section is produced by joining several layers of block boards to each other using a suitable adhesive. The layers are pressed together in a press, where the wooden section is further shaped to the required semicircular shape in the same pressing step. By inclining the cross wooden layer with an angle differing from 90 degrees, it will be easier to bend the cross wooden layers in the press. After the adhesive has hardened, the rabbets of the wooden section are shaped by a precision router, which will allow relatively small tolerances to be obtained. The small tolerances help to improve the stiffness and rigidity of an assembled wooden tower. The wooden sections may divide the circumference of a wooden tower in four, six, eight or more parts, depending mainly on the size of the tower. A wooden section will thus extend over 90, 60 or 45 degrees, or less.

A wooden section will preferably comprise an odd number of wooden layers. The outermost and innermost wooden layer will be longitudinal wooden layers, and every second layer will also be a longitudinal wooden layer. Between the longitudinal wooden layers, cross wooden layers are arranged. The cross wooden layers are angled between 30 to 90 degrees relative the longitudinal wooden layers, and are preferably angled between 45 to 60 degrees. Preferably, a first cross wooden layer is directed to the left, and the next cross wooden layer is directed to the right. A wooden section preferably comprises at least five wooden layers.

Each wooden layer is made from a block board, which comprises a plurality of wooden boards. A longitudinal wooden layer may be between 20 - 80 mm thick, and is preferably between 40 - 60 mm thick. A cross wooden layer may be between 10 - 40 mm thick, and is preferably between 15 - 30 mm thick. A cross wooden layer is thinner than a longitudinal wooden layer, since it must be bent against the fibre direction of the wooden boards. A wooden section is preferably thicker than 160 mm or more, depending on the height of the wooden tower and on the loads that will act on the wooden tower. The width of a wooden board in a wooden block board is preferably wider than 100 mm, and more preferably wider than 160 mm, depending on the thickness of the wooden board. A wooden board is always wider that the thickness of the wooden board. The wooden tower will be self-supporting. There is thus no need for a frame or any stabilizers inside the wooden tower. It is preferred to use as few sections as possible for a wooden tower, which means that the maximal size of a wooden section may be limited by the possibility to transport the wooden sections to the building site. A wooden section may thus be up to thirty meters long. A further limiting factor is the handling of the wooden sections. It is more practical to use wooden sections with a length between fifteen to twenty meters. Wooden towers of different sizes may be constructed with the inventive method. However, the inventive method is mainly advantageous for wooden tower of 50 meters height and more, and is well suited for wind power towers of up to 150 meters and more. The width of a wooden section may also be limited by the transportation of the wooden sections. It may thus be of advantage to divide the circumferential in more than four parts. Fig. 3 shows a schematic view of a wooden section comprising seven layers. Here, it can be seen that the boards, and thus the wooden fibres, of the longitudinal wooden layers are vertical. The shown wooden section comprises a first outer longitudinal wooden layer 31 , a first cross wooden layer 32, a second longitudinal wooden layer 33, a second cross wooden layer 34, a third longitudinal wooden layer 34, a third cross wooden layer 36 and a fourth inner longitudinal wooden layer 37. Each layer is made from a block board, which in turn is made from separate wooden boards. The thickness of a board and thus of a block board depends on which layer it is intended for. A board of a longitudinal wooden layer is thicker than a board of a cross wooden layer. The shown wooden section is also provided with an outer protective coating 30, which may be a plastic foil adapted to protect the wooden section. The protective coating is preferably mounted to the wooden section when the wooden tower is assembled, such that there is no gaps or slits in the protective coating. The boards of the first cross wooden layer 32 are here angled with 45 degrees to the right in relation to the longitudinal wooden layers, the second cross wooden layer 34 is angled with 45 degrees to the left in relation to the longitudinal wooden layers, and the third cross wooden layer 36 is angled with 45 degrees to the right in relation to the longitudinal wooden layers. By alternating the angles of the cross wooden layers, a stronger wooden section is obtained. It is also possible to let all cross wooden layers be perpendicular to the longitudinal wooden layers, i.e. being angled with 90 degrees. The used angle for a cross wooden layer may depend on the required strength of a wooden tower and on the production setup of the wooden sections.

Fig. 4 shows a simplified example of a wooden tower 20 comprising only six straight wooden sections 1 , here shown as two first wooden sections 14, two second wooden sections 15, and two third wooden sections 16, and four end sections, two lower end sections 10 and two upper end sections 1 1. A lower end section 10 is equal to an upper part 4 of a wooden section 1 , and an upper end section 1 1 is equal to a lower part 5 of a wooden section 1 . The assembly of the wooden tower starts with placing two lower end sections 10 on the foundation and placing two first wooden sections 14 in between the lower end sections. Thereafter, two second wooden sections 15 are placed on the upper edges of the lower end sections 10, such that the lower rabbet of the lower part of a second wooden section 15 interacts with the upper rabbet of a lower end section 10. At the same time, the side rabbets of the lower parts of the second wooden sections 15 will interact with the side rabbets of the upper parts of the first wooden sections 14. The first wooden sections are now locked in position by the lower end sections and the second wooden sections. In the shown example, the rabbets of an upper part of a wooden section points outwards, and the rabbets of a lower part points inwards. In this way, a wooden section can easily be mounted to other wooden sections from the outside, by positioning a wooden section in the void between two other wooden sections and by pushing it inwards such that the rabbets bear on each other.

Two third wooden sections 16 are now placed on the upper edges of the first wooden sections 14, such that the lower rabbet of the lower part of a third wooden section 16 interacts with the upper rabbet of a first wooden section 14. At the same time, the side rabbets of the lower part of the third wooden section 16 will interact with the side rabbets of the upper parts of the second wooden sections 15. The second wooden sections are now locked in position by the first wooden sections and the second wooden sections. To complete the wooden tower, two upper end sections 1 1 are placed on the upper edges of the second wooden sections 15, such that the lower rabbet of the lower part of an upper end section 1 1 interacts with the upper rabbet of the second wooden section 15. At the same time, the side rabbets of the upper end sections 1 1 will interact with the side rabbets of the upper parts of the third wooden sections 16. The third wooden sections are now locked in position by the second wooden sections and the upper end sections.

The rabbets of the different wooden sections form half joints. The joints are preferably provided with glue of some kind, e.g. a glue based on polyurethane, and thereafter fixed by using screws. In this way, the joints will be at least as strong as a wooden section, and the tower will withstand the estimated loads. The joints could also comprise e.g. a groove and tongue joint or another suitable joint. However, other joints may be difficult to join if the wooden tower is not straight. Preferably, the joints of each wooden section are glued and screwed together when that wooden section is mounted. The joints are preferably screwed together from the inside of the wooden tower.

A wooden section may be lifted to its position by the use of a crane, but it is also possible to lift a wooden section to its position by using a lift arrangement attached to the upper part of the previously mounted wooden sections. By attaching the lift arrangement to the middle portion of a wooden section, preferably somewhat below the middle of the wooden section, the wooden section can be slid up along the already mounted wooden sections to the position in which the actual wooden section is to be mounted. Since the rabbets of the upper part of a wooden section are directed outwards, and the rabbets of the lower part of a wooden section are directed inwards, the wooden section can easily be pushed inwards when it is in the right position. In this way, a wooden tower can be mounted in an easy way without the need of heavy mounting equipment. Fig. 5 shows an example of a wind power tower 20. The shown wind power tower may be up to 100 meters and more, and is in the shown example tapered somewhat towards the top of the tower. The tower is fixed to a foundation 21 , e.g. comprising steel bars extending up in the tower, to which the lower wooden sections are attached with screws. A door is provided in one of the lower wooden sections. On top of the tower, a nacelle 22 comprising a rotor 23 and a generator is provided. Depending on the type of generator used, a transmission may also be installed.

Since the wooden tower is self-supporting, the inner room of the wooden tower can be used for different installations, such as a lift or stairs and cable racks. Since the inside is made of wood, any installation is easily fastened by using wood screws. At the bottom of the wooden tower, the wooden tower is attached to a foundation. The foundation may be e.g. a steel construction to which the lowermost wooden sections are attached by hexagon head wood screws. Preferably, a climate system is installed inside the wooden tower, which will control the humidity of the wood.

The wooden tower is preferably covered by a protective layer comprising a suitable film or foil, such as a PVC film after it is erected. This will help to protect the wooden tower from environmental influences, such as humidity, which will simplify the control of the humidity balance in the wooden tower. The protective film will also reduce the need to paint the tower after it is assembled.

A wooden section is assembled from a plurality of wooden block boards. The wooden block boards are preassembled from wooden boards before the wooden section is produced. In order to be able to bend the longitudinal layers of block boards without ripping the wood in the block board, the inner side of the block board is preferably provided with a number of longitudinal slots before the block board is placed in the mould that will form the wooden section. The size of the slots, i.e. the depth and the width, depends on the size of the block board, but the depth of a slot may be approximately half of the thickness of the block board, and the width of a slot may e.g. be the same as the width of a saw blade that cuts the slots, and may be e.g. 4 mm. All longitudinal layers are to be provided with slots. A first longitudinal layer is placed in the mould. A layer of glue is applied on the layer, and a first cross layer is placed on the first longitudinal layer. A layer of glue is applied on the cross layer, and a second longitudinal layer is placed on the first cross layer. This is repeated until all layers are placed in the mould. Thereafter, the mould is closed by pressing the two sides of the mould together. When the glue has dries or hardened, the mould is opened and the wooden section is removed. Preferably, the outer and inner surfaces will be ready and will not require any additional work. The side edges of the wooden section are preferably shaped by a router controlled by a computer. In this way, both the outer shape and the rabbets can be shaped, either at the same time or in consecutive runs.

An inventive wooden section may also be used for other types of wooden assemblies. It is e.g. possible to provide a circular tank or cistern by mounting a plurality of semi-circular wooden sections to each other. Such a circular tank may e.g. be used to hold water or other liquids. By placing a plastic foil on the inner surface of the tank, the wooden sections are protected from the stored liquid. One use for such a tank could be a heat storage, where a large quantity of heated water is stored for later use. Such a tank may have a diameter of more than 50 meters, but due to the use of semi-circular cross laminated wooden section, the tank will be able to handle the loads. Another use for semi-circular wooden sections could be an avalanche-protected house, where the part of the house directed to the mountain could be a half circle made from semi-circular wooden sections.

In another embodiment of the invention, a fibre composite section is flat. Also in this embodiment, wood will be used as an example of a fibre composite.

Fig. 6 shows a first example of a wooden section according to another embodiment of the invention. The wooden section is flat and rectangular. By assembling a plurality of wooden sections, a self-supporting wooden assembly is obtained. A wooden section is made from relatively thick wood layers made from block boards which are cross laminated. In this way, a strong and rigid wooden section is obtained. An assembled wooden assembly will be able to withstand loads acting from any direction. In the shown example, the wooden section is rectangular. The wooden section may also be square or may have other shapes.

A wooden section 101 is provided with a first or outer surface 102 and a second or inner surface 103. Outer and inner only refers to an example of the use of a wooden section, e.g. in a self-supporting wall, where one side will point outwards and one side will point inwards. The wooden section comprises an upper part 104 and a lower part 105. The upper part comprises two longitudinal side edges 107, 108 and an end edge 109. The lower part comprises two longitudinal side edges 1 10, 1 1 1 and an end edge 1 12. The wooden section is provided with rabbets 106 along the side edges. The upper part 104 is provided with rabbets 106 pointing in one direction, and the lower part 105 is provided with rabbets 106 pointing in an opposite direction. In the shown example, the rabbets of the upper part are directed outwards in a first direction, towards the outer surface, and the rabbets of the lower part are directed inwards, in a second direction. The height of the upper part equals the height of the lower part. The size of the rabbet, i.e. the width and the thickness of the rabbet, of the upper part equals the size of the rabbet of the lower part. Rabbets of two adjacent wooden sections will thus provide a half joint where the inner and outer surfaces will correspond to each other, such that a smooth surface is obtained. A rabbet is provided with a rabbet edge 1 13, which is the side of the rabbet being parallel to the outer or inner surface of the wooden section. A rabbet is further provided with a rabbet bottom 1 14, which is the side perpendicular to the rabbet edge.

In the example shown in Fig. 6, the end edge 109 of the upper part also comprises a rabbet 106 directed outwards in the first direction, and the end edge 1 12 of the lower part comprises a rabbet 106 directed inwards in the second direction. In the example shown in Fig. 7, the upper end edge 109 of the upper part comprises a tongue 1 15 and the lower end edge 1 12 of the lower part comprises a groove 1 16. In this way, a tongue and groove joint is obtained between a lower edge of one wooden section and an upper edge of another wooden section. It is also possible to provide the upper end edge 109 of the upper part with a groove 1 16 and to provide the lower end edge 1 12 of the lower part with a tongue 1 15.

In the example shown in Fig. 7, the rabbets 106 of the side edges 107, 108, 1 10, 1 1 1 comprise an additional rabbet 1 19. The additional rabbet 1 19 comprises a second rabbet edge 1 17 and a second rabbet bottom 1 18. The additional rabbet increases the contact surface between two adjacent wooden sections, which will increase the glued area and in turn will increase the strength of the joint between two wooden sections. Other joints are also possible. A wooden section will comprise wooden layers oriented in different directions, i.e. the wood fibres are directed in different directions. This is often referred to as cross lamination or cross laminated timber. Glued laminated timber is well known and is used for larger structural wooden members, where all wood fibres are parallel. In cross lamination, every other wooden layer will be directed in another direction, normally 90 degrees when flat boards are manufactured. The longitudinal wooden layers will mainly handle vertical loads, both pushing and pulling loads. The cross wooden layers will help to handle cross loads and twisting loads acting on a wooden assembly. Since all layers are securely attached to each other, the wooden sections will be able to handle high loads in different directions. The example shown in Fig. 6 comprises a first outer longitudinal wooden layer 130, a first cross wooden layer 131 and a second inner longitudinal wooden layer 132. A wooden section is produced by joining several layers of block boards to each other using a suitable adhesive. The layers are pressed together in a press. After the adhesive has hardened, the rabbets of the wooden section are shaped, e.g. by a precision router, which will allow relatively small tolerances to be obtained. The small tolerances help to improve the stiffness and rigidity of an assembled wooden assembly.

A wooden section will preferably comprise an odd number of wooden layers. The outermost and innermost wooden layer will be longitudinal wooden layers. Between the longitudinal wooden layers, cross wooden layers are arranged. The cross wooden layers are preferably perpendicular to the longitudinal wooden layers, but may also be angled with an angle differing from 90 degrees relative the longitudinal wooden layers. If at least two cross layers are used, a first cross wooden layer is directed to the left, and the next cross wooden layer is directed to the right. A wooden section preferably comprises at least three wooden layers. Each wooden layer is made from a block board, which comprises a plurality of wooden boards. A longitudinal wooden layer may be between 20 - 80 mm thick, and is preferably between 40 - 60 mm thick. A cross wooden layer preferably has the same thickness, even though it is possible that the cross layer is somewhat thinner or thicker. A wooden section is preferably thicker than 80 mm or more, depending on the size of the wooden assembly and on the loads that will act on the wooden assembly. The width of a wooden board in a wooden block board is preferably wider than 100 mm, and more preferably wider than 160 mm, depending on the thickness of the wooden board. A wooden board is always wider that the thickness of the wooden board.

A wooden assembly comprising a plurality of wooden sections will be self- supporting. It is preferred to use as few wooden sections as possible for a wooden assembly in order to reduce the number of joints. This means that the maximal size of a wooden section may be limited by the possibility to transport the wooden sections to the building site. A further limiting factor is the press in which the wooden section is produced. A wooden section may thus be up to thirty meters long. A further limiting factor is the handling of the wooden sections. It is more practical to use wooden sections with a length between fifteen to twenty meters. Wooden assemblies of different sizes may be constructed by using the inventive wooden section. The inventive section is equally suitable for wooden assemblies comprising only two wooden sections, as for wooden assemblies comprising more than ten wooden sections. The width of a wooden section may also be limited by the transportation of the wooden sections.

Fig. 8 shows an example of a part of a wooden assembly 129 comprising six wooden sections 101 . The wooden sections are joined to each other one by one. A wooden section is mounted to another wooden section by the use of glue and screws. The glue is applied to the rabbets before two wooden sections are joined, and the joint is then secured by a number of wooden screws. Depending on the type of wooden assembly and on how the wooden sections are assembled, the screws may be omitted. The rabbets of the different wooden sections form half joints. The joints are preferably provided with glue of some kind, e.g. a glue based on polyurethane or PVA, and may thereafter be fixed by using screws. In this way, the joints will be at least as strong as a wooden section, and the wooden assembly will withstand the estimated loads. The joints are preferably screwed together from one side of the wooden assembly. A wooden assembly may be used as self-supporting walls in a building or other construction. A wooden assembly may also be used as a self- supporting ceiling joist or floor joist. By using a plurality of wooden sections, self-supporting buildings can be obtained in an easy and cost- effective way, which are strong and rigid. The invention is not to be regarded as being limited to the embodiments described above, a number of additional variants and modifications being possible within the scope of the subsequent patent claims. A fibre composite section may be used for other flat or circular objects, e.g. walls, floors, wooden tubes, and may have various sizes. The fibre composite section is intended for use in buildings.

REFERENCE SIGNS

1 : Wooden section

2: Outer surface

3: Inner surface

4: Upper part

5: Lower part

6: Rabbet

7: Rabbet edge

8: Rabbet bottom

9: Edge

10: Lower end section

1 1 : Upper end section

12: Upper edge

13: Lower edge

14: First wooden sections

15: Second wooden sections

16: Third wooden sections

20: Wind power tower

21 : Foundation

22: Nacelle

23: Rotor

30: Protective coating

31 : First longitudinal wooden layer

32: First cross wooden layer

33: Second longitudinal wooden layer

34: Second cross wooden layer

35: Third longitudinal wooden layer

36: Third cross wooden layer

37: Fourth longitudinal wooden layer

101 : Wooden section

102: Outer surface

103: Inner surface

104: Upper part

105: Lower part

106: Rabbet : First upper side edge

: Second upper side edge

: Upper end edge

: First lower side edge

: Second lower side edge

: Lower end edge

: Rabbet edge

: Rabbet bottom

: Tongue

: Groove

: Second rabbet edge

: Second rabbet groove

: Additional rabbet

: Wooden assembly

: First outer longitudinal wooden layer: First cross wooden layer

: Second longitudinal wooden layer

Claims

Fibre composite section (1; 101) for a self-supporting assembly (20; 129), where the fibre composite section (1; 101) comprises a plurality of laminated fibre composite layers (31, 32, 33, 34, 35, 36, 37; 130, 131, 132), characterized in that the fibre composite section comprises an upper part (4; 104) and a lower part (5; 105), where the edges (9, 12, 13; 107, 108, 109, 110, 111,

112) of the upper and lower part comprises rabbets (6; 106), where the rabbets (6; 106) of the upper part (4; 104) are directed in a first direction relative the outer surface (2; 102) of the fibre composite section, and where the rabbets (6; 106) of the lower part (5; 105) are directed in the opposite direction relative the outer surface (2; 102) of the fibre composite section, and where rabbets (6; 106) of the upper part (4; 104) of a fibre composite section (1; 101) are adapted to cooperate with rabbets of the lower part (5; 105) of another fibre composite section when a plurality of fibre composite sections are assembled to a self-supporting assembly (20; 129).

Fibre composite section according to claim 1, characterized in that the upper part (4; 104) and the lower part (5; 105) have the same length.

Fibre composite section according to any of the preceding claims, characterized in that the longitudinal rabbet edges (7;

113) of the upper and the lower part are positioned in the same plane.

Fibre composite section according to any of the preceding claims, characterized in that the longitudinal rabbet bottoms (8;

114) of the upper and the lower part are positioned in the same plane.

5. Fibre composite section according to any of the preceding claims, characterized in that a fibre composite layer comprises fibres directed in substantially one direction.

6. Fibre composite section according to any of the preceding claims, characterized in that a fibre composite layer is a wooden sheet block board layer made from a plurality of wooden boards.

7. Fibre composite section according to claim 8, characterized in that the fibre composite section comprises a plurality of longitudinal wooden layers (31 , 33, 35, 37; 130, 132) directed in the longitudinal direction of the fibre composite section, and at least one cross wooden layer (32, 34, 36; 131).

8. Fibre composite section according to any of claims 6 or 7, characterized in that the longitudinal wooden layers are at least twice as thick as the cross wooden layer.

9. Fibre composite section according to any of claims 6 to 8, characterized in that the angle between the longitudinal fibre composite layers and the cross fibre composite layers is in the range between 30 to 90 degrees.

10. Fibre composite section according to any of the preceding claims, characterized in that the fibre composite section is flat.

11. Fibre composite assembly, comprising a plurality of fibre composite sections according to any of claims 1 to 10.

12. Fibre composite section according to any of claims 1 to 10, characterized in that the fibre composite section is semicircular in the width direction.

13. Fibre composite tower, comprising a plurality of fibre composite sections according to claim 12.

14. Fibre composite tower according to claim 13, where the tower further comprises a lower end section (10) and an upper end section (1 1 ).

15. Method for assembling a fibre composite tower using a plurality of fibre composite sections according to claim 12, where the method comprises the following steps of; placing a plurality of lower end sections on a foundation, placing a plurality of fibre composite section between the lower end sections such that a circle is formed, placing the lower part of a fibre composite section on the upper edge of a lower fibre composite section and between the upper parts of two other fibre composite sections, repeating this step until all fibre composite sections are used, and placing a plurality of upper end sections in the remaining voids between upper parts of fibre composite section, and applying glue to the edges of each fibre composite section before it is mounted, and securing each joint by using wooden screws and glue.