A beam having a body of a wood-based material

Abstract

The present disclosure provides a method of installing a beam (1) comprising a longitudinal body of a wood-based material (3), the longitudinal body extending in a longitudinal direction (5) and having a first longitudinal end (11) and an opposite second longitudinal end (13) in the longitudinal direction (5); a top face (15) and an opposite bottom face (17). The beam further comprises a channel (23) in the form of a curved tubular channel (23) extending through the beam (1) in the longitudinal direction (5) to be closer to the bottom face (17) in an intermediate position (29) than at the first longitudinal end (11) and the second longitudinal end (13), and a tension element (31) extending through the channel (23). The tension element (31) is fastened at at least one of the first end (25) and the second end (27) of the channel (23) by an adjustable means (37) for adjusting a pull provided by the tension element (31). The method comprises a step of applying a load to the beam and a step of post tensioning the beam (1) by applying a pull in the tension element by the adjustable means (37), while the load is applied.

Description

[0001] A BEAM HAVING A BODY OF A WOOD-BASED MATERIAL

[0002] Field of the disclosure

[0003] The present disclosure relates to a method of installing a beam comprising a longitudinal body of wood-based material, the longitudinal body extending in a longitudinal direction and having a height dimension, a width dimension perpendicular to the height dimension, and a longitudinal dimension perpendicular to the height dimension and the width dimension, the longitudinal body having a first longitudinal end and an opposite second longitudinal end in the longitudinal direction; a top face and an opposite bottom face, the top face being uppermost in an intended position of installation; and two side faces opposite to each other, the top face, the bottom face and the two side faces extending between the first longitudinal end and the second longitudinal end. The present disclosure further relates to the beam. The present disclosure further relates to a method of adjusting the beam. The present disclosure further relates to a method of manufacturing the beam.

[0004] Description of the disclosure

[0005] The disclosure thus relates to a beam comprising a body of wood-based material. The woodbased material may e.g. be lumber, structural timber, or laminated wood, e.g. such as glulam, laminated veneer lumber (LWL), Glue-laminated timber (GLT), Cross-laminated timber (CLT).

[0006] Using beams of wood-based material for a construction rather, than concrete beams, may reduce the CO2 footprint of such construction.

[0007] However, the span possible for beams of wood-based material having given cross-sectional dimensions may not suffice for a given construction.

[0008] Accordingly, it is an object of the present disclosure to provide a beam having a body of wood-based material allowing a larger span than a corresponding wood-based beam per se.

[0009] French patent No. FR 1 213 358, published 31 March 1960, discloses a curved and reinforced wooden beam, for all uses requiring light and economical beams at the same time resistant to bending when they rest on two supports, and particularly for light roofs, for example for shelters or exhibition stands. The curved wooden beam makes it possible to form roofs using concave cylindrical surface elements. The curved wooden beam is provided in its lower side with shallow grooves accommodating tension members extending lengthwise through the beam and being tightened by means of nuts at the ends of the beam by application of prestress.

[0010] Russian patent No. RU 2 728 058 discloses a prestressed wooden floor beam for buildings. To increase the overall load-bearing capacity of the prestressed wooden beam, the compression zone is strengthened. This is achieved by a wooden beam comprising a monolithic insert and longitudinally prestressed reinforcing rods.

[0011] D'Aveni et al. describes in "Post-tensioned timber structures: New perspectives" from Construction and Building Materials, Elsevier, vol. 153 from 18 July 2017 prestressed GL beams, where the prestress is applied by means of a set of tendons made of carbon fibre composite material. The proposed technology leads to structural elements of prestressed engineered wood entirely made in factory. Prestressing is obtained by means of posttensioning technique.

[0012] It is an object of the present disclosure to provide an improved and more versatile beam comprising a body of wood-based material.

[0013] It is an object of the present disclosure to provide an improved method of installing a beam comprising a body of wood-based material.

[0014] In a first aspect, the disclosure provides a method of installing a beam in a construction, the beam comprising : a longitudinal body of a wood-based material, the longitudinal body extending in a longitudinal direction and having a height dimension, a width dimension perpendicular to the height dimension, and a longitudinal dimension perpendicular to the height dimension and the width dimension, the longitudinal body having a first longitudinal end and an opposite second longitudinal end in the longitudinal direction; a top face and an opposite bottom face, the top face being uppermost in an intended position of installation; and two side faces opposite to each other, the top face, the bottom face and the two side faces extending between the first longitudinal end and the second longitudinal end, a channel in the form of a curved tubular channel extending through the longitudinal body in the longitudinal direction, said channel extending curved from a first end of the channel to a second end of the channel to be closer to the bottom face in an intermediate position between the first longitudinal end and the second longitudinal end than at the first longitudinal end and the second longitudinal end, and a tension element extending through the channel, said tension element being a longitudinal element having a first end and a second end, said first end and second end of the tension element being fastened respectively at the first end and the second end of the channel, the tension element being fastened at at least one of the first end and the second end of the channel by an adjustable means for adjusting a pull provided in the tension element the method comprising the steps of:

[0015] - providing a first support element and a second support element, the first and second support elements being arranged at a distance from each other in a horizontal direction,

[0016] - positioning the beam in a first configuration on the first and second support element, where the first longitudinal end is arranged closer to the first support element than the second longitudinal end, and where the second longitudinal end is arranged closer to the second support element than the first longitudinal end,

[0017] - applying a load to the beam; and

[0018] - subsequently post tensioning the beam by applying a pull in the tension element by the adjustable means bringing the beam into a second configuration, while the load is applied.

[0019] Providing the tension element in a tubular channel which thereby is embedded in the material of the longitudinal body at least provides for enhanced aesthetic appearance of the beam and provides protection for the tension element compared to the beam according to the above- mentioned French patent. Thus, by the term tubular channel should in the present context be understood a channel fully encircling the tension element provided in the tubular channel. Hereby the beam of the present disclosure in more versatile in terms of possible applications relative to the French prior art beam.

[0020] The wood-based material may e.g. be lumber, structural timber, or laminated wood, e.g. such as glulam, laminated veneer lumber (LWL), Glue-laminated timber (GLT), Crosslaminated timber (CLT).

[0021] The beam according to the present disclosure is preferably straight in its installed condition making the beam even more versatile, where the installed condition is to be understood as the second configuration where a pull is applied to the tension element after positioning of the beam and subsequent application of a load. The load may be the permanent load, which is applied to the beam, when installed in a building construction, such as a building or a bridge. In a first step, a first support element and a second support element are provided. As an example, the support elements may be columns, pillars, poles, wall elements, bridge bearings, or the like, it should be understood, that the first and second support element may be of the same type. However, in an alternative embodiment, the first and second support element may be of different types, e.g. by providing a first support element in the form of a column and the second support element in the form of a wall element.

[0022] The first and second support elements are arranged at a distance from each other in a horizontal direction. Subsequently, the beam is positioned in a first configuration on the first and second support elements. The first longitudinal end of the longitudinal body of the beam is arranged closer to the first support element than the second longitudinal end of the longitudinal body. The second longitudinal end of the longitudinal body is arranged closer to the second support element than the first longitudinal end of the longitudinal body.

[0023] In one embodiment, the first longitudinal end of the longitudinal body of the beam is arranged at the first support element whereas the second longitudinal end of the longitudinal body is arranged at the second support element, whereby the opposite first and second ends are supported at the first and second support elements, respectively.

[0024] In an alternative embodiment, the beam may be arranged with a least one end extending beyond a support element so that at least one of the first and second longitudinal ends is not arranged at the respective support element. Thus, at least one of the first and second support elements may support the beam at the bottom face in an area at a distance from the first and / or second longitudinal ends.

[0025] When positioning the beam in the first configuration on the first and second support element, stress may occur in the beam, particularly stress in the wood fibres in the upper part and the lower part of the wood-based longitudinal body. Thus, the first configuration may be characterized by stresses in the upper and lower parts of the body which may at least partly occur due to the self-weight of the beam.

[0026] Subsequent to the step of positioning the beam in the first configuration on the first and second support elements, a load is applied to the beam. The load may be a permanent load of building construction parts carried by the beam, such as deck for an upper floor. It should be understood that the load may be applied to more than one beam, e.g. by positioning a deck on two substantially parallelly arranged beams each being positioned on a first and a second support element, where two adjacent beams may share at least one of a first and a second support element. When applying the load, the stresses in the beam may change, which may bring the beam into an intermediate configuration. Subsequent to the step of applying the load to the beam, the beam is post tensioned, while the load is still applied. The beam is post tensioned by applying a pull to the tension element by the adjustable means to thereby adjust the pull provided by the tension element. The applied pull in the tension element may create compression of the longitudinal body. The applied pull in the tension element brings the beam into a second configuration.

[0027] The applied pull may create compression of the longitudinal body which may balance stresses in the beam to thereby counteract the applied load to the beam and the load of the selfweight of the beam. Thus, the applied pull may result in compression being equivalent to the applied load and the self-weight load of the beam, however, opposite hereto.

[0028] In addition to apply a pull to balance the load and the self-weight, the applied pull may additionally generate a significant axial force along the tension element, which may create a more stiff and rigid structure and a have a dampening effect, and an increased natural frequency (Hz).

[0029] Thus, the method provides installation of a beam where a pull is applied after positioning of the beam on the first and second support elements and after applying a load to the beam to thereby provide a post-tensioned beam.

[0030] Compared to prior art pre-stressed beams, post-tensioning provides several advantages. As an example, pre-stressing does not provide the ability of balancing the stress in the beam due to permanent loads. Pre-stressing cannot be carried out with the same amount of tension as post-tensioning. If trying to pre-stress a beam with the same amount of tension as applied by post-tensioning a beam arranged on a first and a second support structure and exposed to a load, the pre-stressed beam would at least partly break. A pre-stressed beam is prestressed to a specific design load, whereas post-tensioning allows for accommodation of building tolerances, as post-tensioning is carried out on-site after application of the load. Post-tensioning further allows for connection of a plurality of beam sections sharing a common tension element extending through the plurality of beam sections.

[0031] The cross-section of the curved tubular channel may be circular, but other cross-sections are possible, e.g. square, elliptical, etc.

[0032] By the term "beam" as used herein should be understood an element whose longitudinal dimension is substantially larger than the height dimension and the width dimension, preferably the longitudinal dimension is more than 10 times the width dimension, preferably more than 20 times the width dimension, and further preferably more than 30 times the width dimension. The longitudinal body may form a downwardly deflecting shape between the first and second support elements in the first configuration, at least partly occurring due to the self-weight of the beam. As a result, stresses in the upper and lower parts of the body may occur.

[0033] In the second configuration, the top face of the longitudinal body may form a substantially plane surface in the second configuration. Thus, post tensioning of the beam may change the shape of the longitudinal body from a downwardly deflecting shape to a substantially straight shape, while at the same time at least partly counteracting stresses in the longitudinal body.

[0034] In one embodiment, the step of post tensioning the beam by applying a pull to the tension element by the adjustable means is carried out by applying a pull in the tension element at at least one of the first and second ends. In one embodiment, a pull is applied at only one of the first and second ends. Alternatively, a pull is applied at both the first and second end.

[0035] Applying a pull at both ends may be carried out simultaneously at both ends, however, a pull may be applied at one end at a time, e.g., alternating at the first and the second end. If a pull is only applied at one end, the specific end may as an example be selected based on accessibility of the respective end. In one embodiment, the application of a pull at one end or at both ends may depend on the length of the beam.

[0036] The method of installing the beam in a building may comprise a further step of providing an additional support element, where the step of positioning the beam on the first and second support element may comprise positioning the beam on the additional support element. The additional support element, which may be a temporary support element, may be positioned between the first and second support element prior to positioning the beam in the first configuration on the first, second, and additional support elements. The use of an additional support element may decrease the downward deflection of the longitudinal body in the first configuration and may decrease stress occurring in the beam, particularly in the upper and the lower parts of the wood-based longitudinal body.

[0037] The method may comprise a further step of removing the additional support element after the step of post tensioning the beam, as the subsequent post-tensioning of the tension element may make continued use of the additional / temporary support element superfluous. The use of an additional / temporary support element may further allow for beams of a greater span.

[0038] In another aspect, the disclosure provides a method of adjusting the beam. The method may comprise a step of applying an additional pull in the tension element after installation of the beam in accordance with the above-described method. The step of applying an additional pull may be carried out after a predetermined period of time, such as a predetermined period of 1 year, two years, or another period. The predetermined period may be determined based e.g. on the size of the beam, the span of the beam, the load applied, and other features. The method of adjusting the beam may be carried out in response to changed use of the construction in which the beam is installed. As an example, if changing the use of the building from an office building to a storage facility, a permanent part of the live load may be increased from e.g. 3 kN / m2to 10 kN / m2. By increasing the pull provided by the tension element by the adjustable means for adjusting the pull, the beam may be adjusted to the changed configuration.

[0039] In a second aspect, the disclosure provides beam comprising a longitudinal body of a wood-based material, the longitudinal body extending in a longitudinal direction and having a height dimension (h), a width dimension (w) perpendicular to the height dimension (h), and a longitudinal dimension (I) perpendicular to the height dimension and the width dimension (w), the longitudinal body having a first longitudinal end and an opposite second longitudinal end in the longitudinal direction; a top face and an opposite bottom face, the top face being uppermost in an intended position of installation; and two side faces opposite to each other, the top face, the bottom face, and the two side faces extending between the first longitudinal end and the second longitudinal end, a channel in the form of a curved tubular channel extending through the body in the longitudinal direction, said curved tubular channel extending curved from a first end of the channel to a second end of the channel to be closer to the bottom face in an intermediate position between the first longitudinal end and the second longitudinal end than at the first longitudinal end and the second longitudinal end, and a tension element extending through the channel, said tension element being a longitudinal element having a first end and a second end, said first end and second end of the tension element being fastened respectively at the first end and the second end of the channel, the tension element being fastened at at least one of the first end and the second end of the channel by an adjustable means for adjusting a pull provided in the tension element.

[0040] It should be understood, that a skilled person would readily recognise that any feature described in combination with the first aspect of the disclosure could also be combined with the second aspect of the disclosure, and vice versa.

[0041] The beam according to the second aspect of the disclosure is very suitable for performing the method steps of the method of installing a beam in a construction according to the first aspect of the disclosure. The remarks set forth above in relation to the beam are therefore equally applicable in relation to the method, and vice versa.

[0042] The height dimension can be larger than the width dimension. It is also possible that the width dimension is larger than the height dimension or the width dimension and the height dimension are equal. The ratio between the width and the height may depend on the specific application of the beam, such as the length, the distance between the first and second support elements, the load applied, etc.

[0043] In an embodiment the longitudinal element has a substantially constant cross-section from the first longitudinal end to the opposite second longitudinal end thereof. In an embodiment the two side faces are substantially parallel and plane.

[0044] The curve through which the channel is extending may be a parabolic curve at least along a part of the channel. This provides for improved physical capabilities, thus gaining increased span while keeping the same cross-section.

[0045] The tension element may be formed by a steel wire or steel rod or similar structure being capable of being tensioned. It should be understood that the tension element may comprise a plurality of tension component each extending from the first end of the tension element to the second end of the tension element. In one embodiment, each of the tension components may be steel wire or rod. As an example, the tension element may comprise two, three, four, five, six, or even more tension components which in one embodiment may be twisted to form the tension element. The tension element may be arranged in a cover, before arranging the tension element in the channel. This may also be applicable to a tension element comprising a plurality of tension components.

[0046] The diameter of the tension element may as an example be in the range of 16-64 mm, such as in the range of 20-60 mm. In an embodiment, where the tension element comprises a plurality of tension components, each of the tension components may have a diameter in the range of 8-20 mm. The diameter may depend on the cross-sectional size of the longitudinal body, the length of the beam, the applied load, the required span of the beam, etc.

[0047] The cross-section of the curved tubular channel may be circular having a diameter being at least 2% larger than the diameter of the tension element. In an embodiment, where the cross-sectional shape of the curve tubular channel is non-circular, but e.g. oval, square, or elliptical, the diameter may denote the largest dimension of the channel being at least 2% larger than the diameter of the tension element. The tension element may be supported by an anchor plate at least at one of the first end and the second end of the channel. This provides for fixing and / or tensioning the end of the tension element at the end of the channel.

[0048] In an embodiment, elongated elements extend transverse to the channel. The elongated elements may extend transverse to the channel above the channel, when the beam is installed; i.e. between the channel and the top face of the longitudinal body. The elongated element may extend tangentially to the channel which may provide contact between the elongated elements and the tension element. This may provide for enhanced support for the tension element along the channel and may ensure that the tension element is kept in place when applying a pull to the tension element. Thereby, such elongated elements arranged transverse to the channel may provide relief for the wood-based material bordering the channel to allow for greater post-tensioning of the beam.

[0049] As an example, the elongated elements may be studs or bolts or elements of a similar structure. The elongated elements may be made of steel and may have a diameter in the range of 8-36 mm, such as in the range of 12-20 mm. It should be understood that the elongated element may have a cross-sectional shape being circular, an oval shape, a triangular shape, or other shape. In one embodiment, the beam comprises at least 5 elongated elements extending transverse to the channel. The number of elongated elements may depend on the length of the beam.

[0050] In an embodiment the anchor plate comprises flanges extending along the side faces of the longitudinal body. Such flanges may provide for fixation of the anchor plate and may protect the beam adjacent the anchor plate.

[0051] In a practical embodiment the longitudinal body at outmost ends in the longitudinal direction comprises a first end face and a second end face respectively at the first longitudinal end and the second longitudinal end, wherein at least one of the first end and the second end of the channel is placed respectively in the first end face and the second end face.

[0052] A first opening into the channel at the first end of the longitudinal body may be arranged with a first distance to the top face and a second distance to the bottom face. To minimize torque at the first end of the longitudinal body when applying post tensioning the tension element, the first distance and the second distance may be substantially equal.

[0053] A second opening into the channel at the second end of the longitudinal body may be arranged with a third distance to the top face and a fourth distance to the bottom face. To minimize torque at the first end of the longitudinal body when applying post tensioning the tension element, the third distance and the fourth distance may be substantially equal.

[0054] In one embodiment, the first, second, third, and fourth distance may all be equal, thereby providing a centrally arranged first and second opening in the channel at the first and second ends of the body relative to the height of the longitudinal body. It should be understood that at least one of the first and second opening may additionally or alternatively be centrally arranged relative to the width of the longitudinal body.

[0055] In a further embodiment the end face(s) in which the end(s) of the channel is placed are covered by the anchor plate. Hereby the relevant end faces are armed and protected to withstand the tension from the tension element.

[0056] In a further embodiment the anchor plate is part of a capsule element comprising the anchor plate and flanges extending along at least one of the top face, the bottom face, and the two side faces, preferably the capsule element circumscribing the respective one of the first longitudinal end and the second longitudinal end of the longitudinal body adjacent the end face thereof. Thus, the capsule element may circumscribe the end of the longitudinal body as an unbroken band. Hereby a box-like structure may be obtained to achieve an enhanced transfer of tension or tendon forces from the tension element and retain a possible elastic element or an elastomeric pad, and the wood-based material or timber in the zone where the stress at the end of the channel is more localized. Hereby an increased tension capacity may be obtained by avoiding bursting of materials and directing compression-forces into the beam material inside the box-like structure.

[0057] Thus, in a further embodiment an elastic element with a higher elasticity than the anchor plate may be inserted between the end face and the anchor plate covering said end face. Thereby a distribution of forces around the end of the channel may be obtained.

[0058] In a practical embodiment the longitudinal body comprises two body parts provided on respective sides of a vertical longitudinal plane extending in the longitudinal direction, said body parts having respective engaging faces engaging each other, the channel being recessed into at least one of the engaging faces. Hereby a practical method of obtaining the channel through the beam is provided. The channel may be recessed by carved, e.g. by milling into the material of the body part.

[0059] In an embodiment a part of the channel is recessed into each of the engaging faces. Hereby is obtained a symmetry of production and the distance into the material of the body parts that the channel needs to be carved is minimized. In an embodiment the two body parts are interconnected by at least one of: adhesive applied to the engaging faces, and mechanical penetrating elements, such as screws, bolts, nails. Hereby transverse elongated elements, such as studs or bolts, which may extend tangentially relative to the channel, above the channel may assist in interconnecting and securing the two body parts.

[0060] Additionally, or alternatively, the longitudinal body may comprise two body sections provided on respective sides of a vertical longitudinal plane extending perpendicular to the longitudinal direction, where the body sections have respective engaging section faces engaging each other. By providing the longitudinal body in sections, transportation of the longitudinal body to the construction site may be facilitated, as assembling of the longitudinal body may be carried out on the construction site.

[0061] The curved tubular channel extends through the body from a first end of the channel to a second end of the channel to be closer to the bottom face in an intermediate position between the first longitudinal end and the second longitudinal end than at the first longitudinal end and the second longitudinal end. In one embodiment, the curved tubular channel may comprise two downwardly extending curved sections, two upwardly extending curved sections and two positions where the channel is closer to the bottom face than at the first and second longitudinal ends of the longitudinal body. Thus, the curved channel may have the shape of a curved W. In one embodiment, the first part of the curved channel may extend through the first body section, whereas the second part of the curved channel may extend through the second body section.

[0062] The first and second openings into the channel at the first longitudinal end and at the second longitudinal end of the longitudinal body may be arranged substantially centrally relative to the height of the longitudinal body to minimize torque at the first and second ends of the longitudinal body when post tensioning the beam. In an embodiment comprising a curved channel having the shape of a curved W, the intermediate top section of the channel in the W may be arranged closer to the top face than at the first longitudinal end and the second longitudinal end. This may provide the ability to take-up a higher load at the position of the intermediate top section leading to longer possible spans, and leading to CO2 and cost savings.

[0063] It should be understood that that the two body sections may be of the same longitudinal size. However, in an alternative embodiment, one body section may be longer than the other body section. It should further be understood that the longitudinal body may comprise more that two body sections, such as three, four, or even more body sections. By a longitudinal body comprising a plurality of body sections, it may further be possible to implement longer beams in a building construction. In this case, the additional step of providing at least one additional / temporary support element may advantageously be included.

[0064] Dependent on the length of the final beam comprising a plurality of body sections, one or more additional support elements may be applied, where at least one of the additional support elements may be a stationary support element which may not be removed after post-tensioning the beam by applying tension to the tension element. The additional stationary support element may be arranged in the area of the intermediate top section of the channel in the W. Furthermore, elongated elements extending transverse to the channel above the channel along at least a part of the channel, may in the area of the of the intermediate top section of the channel in the W be arranged below the channel to better transfer load to the beam and to the stationary additional support element.

[0065] The tension element extends through the channel having a first end and second end fastened at the first end and the second end of the channel, respectively. The tension element may extend through the plurality of body section and may be fastened at the first end and / or at the second end of the channel by adjustable means for adjusting a pull provided in the tension element.

[0066] In an embodiment an additional longitudinal compression element is applied at the top face. A portion of the beam at the top face, especially a central longitudinal portion of the beam at the top face may be subject to significant compression stresses arising from the prestressing force or tension of the tension element. In certain cases, such as in case of a beam providing a very long span, or in case of a beam intended for a very heavy load, whereby the prestressing force or tension of the tension element need to be very high, the material of the beam at the top face, especially a central longitudinal portion of the beam at the top face may be subject to excessive compression stresses arising from the prestressing force or tension of the tension element relative to strength of compression of the material. In such case providing an additional longitudinal compression element applied at the top face will provide the extra strength needed by the circumstances.

[0067] In an embodiment the additional longitudinal compression element may be provided by additional material added to the side faces, preferably to flush with the top face, thereby providing a generally T-shaped cross-sectional profile for the thus reinforced longitudinal part of the beam. In an embodiment the longitudinal compression element is provided in a recess at or in the top face, said recess preferably having a width smaller than the width dimension of the longitudinal body, and said recess extending a distance from the top face towards the bottom face. Hereby a part of the timber section of the beam, i.a. a part of the wooden or woodbased material of the longitudinal body, is replaced by a stronger i.e. a more compression resistant material.

[0068] By "compression resistance" should be understood ability to withstand compressing pressure i.e. force per area. In general, whether such reinforcement is needed may be determined by calculation.

[0069] In a further embodiment the longitudinal compression element is in the longitudinal direction extending a shorter distance than the length of the tension element. Thus, the longitudinal compression element may in the longitudinal direction be extending a distance shorter than 90% of the length the tension element, shorter than 80% of the length the tension element, shorter than 70% of the length the tension element, or shorter than 60% of a length the tension element.

[0070] In an embodiment the longitudinal compression element is extending a distance of approx. 40-80% of the length of the tension element. In an embodiment the longitudinal compression element is extending a distance of approx. 50-60% of the length of the tension element.

[0071] By providing the longitudinal compression element to extend a distance shorter than the length of the tension element is i.a. obtained a freedom of designing the ends of the channel and their position since a risk of the channel interfering with the longitudinal compression element is minimized.

[0072] The longitudinal compression element may comprise a metal element e.g. a steel element possibly including a jack for adjustment of the actual or current length of the longitudinal compression element and the pressure exerted by the compression element in the longitudinal direction during operation.

[0073] The longitudinal compression element may comprise or may be made of a material having a higher compressive strength than the wood-based body. In an embodiment the longitudinal compression element comprises a cured or set moulding material, preferably concrete. Hereby it is possible to e.g. carve or machine a recess extending into the material of the beam from the top face and pour, cast, or mould a curable or settable material into the recess for said settable material to fill the recess and set as a longitudinal compression element. In an alternative embodiment, the longitudinal compression element may comprise at least one of epoxy, resin, wood, steel, or another material having a higher compressive strength than the wood-based body.

[0074] In another embodiment the longitudinal compression element is pre-formed and inserted in a recess provided in the beam, the recess preferably extending into the material of the beam from the top face.

[0075] In a further embodiment the longitudinal compression element is penetrated by at least one mechanical fastening element, preferably extending perpendicular to the longitudinal direction, and further preferably extending parallel to the height dimension. The at least one mechanical fastening element may alternatively extend parallel to the width dimension. Hereby a better coherence with the beam can be obtained for the longitudinal compression element thereby enhancing the strength of the beam and the span obtainable for the beam.

[0076] The beam may comprise more than one tension element extending through a tubular channel through the wood-based longitudinal body. In one embodiment, the beam comprises an additional channel extending substantially parallel to the channel through the longitudinal body. The additional channel may extend at a channel distance to the channel, where an additional tension element may extend through the additional channel. In one embodiment, the channel distance may substantially correspond to half the width of the longitudinal body. The additional channel and the channel may each be arranged at a distance from a side face of the longitudinal body, where the distance from one side face to the channel may be equal to the distance from the other side face to the additional channel. In one embodiment, the distance from the side face to the channel maybe half the channel distance.

[0077] To facilitate arranging of the tension element and the additional tension element in the longitudinal body, the longitudinal body may comprise three longitudinal body parts provided on respective sides of vertical longitudinal planes (p) extending in the longitudinal direction, where a first and a second body part are provided on respective sides of a first vertical plane and where the second body part and a third body part are provided on respective sides of a second vertical plane, the first and second vertical planes being substantially parallel. Thus, the second body part may be provided between the first and the second vertical planes. In this embodiment, the body parts have respective engaging faces engaging each other. The channel and the additional channel may each be recessed into at least one of the engaging faces. As an alternative, to the second body part may arranged between the first and second vertical planes, two separate body parts may be arranged adjacent to each other between the first and second vertical planes. Thus, the beam may comprise two tension elements and four body parts, where the four body parts together form the longitudinal body. If each of the four body parts comprises a part of the channel or the additional channel, the four body parts may be identical thereby providing symmetry of production.

[0078] As described above, the method of installing a beam, comprises providing a beam as disclosed above, installing the beam in a non-vertical, preferably substantially horizontal position in which the longitudinal dimension of the beam is in a non-vertical, preferably substantially horizontal position, and subsequently applying a pull in the tension element. By this method is obtained that prior to installation a pull in the tension element will not excessively deflect an otherwise unloaded beam. After the beam has been installed i.e. placed in the position of installation and gravity act on the beam tending to stress the beam, and adding a load, applying a pull in the tension element will provide for balancing the forces thereby providing an intended shape, e.g. a substantially rectilinear shape of the beam, even when subsequently loaded by a non-permanent load in use of a construction in which the beam is a part. Thus, the beam according to the present disclosure is a post-tensioned beam rather than a pre-stressed beam.

[0079] A beam according to the embodiments of the present disclosure may involve a number of benefits. Relative to ordinary wood-based beams a beam according to the present disclosure provides for increased span while keeping the same cross section, and while reducing the need for support structures and foundations.

[0080] Thus, according to calculations performed by the inventors, a beam according the disclosure may provide for an increased span of at least 30%. However, dependent on the tension element applied, the span may be increased up to 60%, such as up to 70%, such as up to 80%, or even more.

[0081] As a supplement to the increased span with retained cross-section, a beam according to the present disclosure may have improved capabilities when exposed to fire and / or increase in vibration-damping abilities.

[0082] The resistance to fire is not determined by the charring of the wood as in conventional woodbased beams in the fibres.

[0083] A critical temperature of the tension element, when the tension element loses strength during a fire-situation is the main determining factor in the fire-documentation of the beams fireresistance and capabilities.

[0084] Thus, for a beam according to the present disclosure, during exposure to fire, the charring of the wood is not the determining factor of the fire resistance. While wood is exposed to fire from three directions, i.e. from below and from the sides, the charring I scorching of the intact wood is charring at a temperature of approximately 200-300 degrees Celsius and a rate of approx. 0,65mm / min.

[0085] The charring of the beam according to the disclosure may be resulting in a cooling effect due to gasses evaporating during the charring process and due to so-called High- and Low Temperature Charring Phenomena

[0086] The fire resistance of an embodiment of the beam according to the present disclosure is determined as a combination of minimum required wood in the cross section during charring in a compression-zone at the top face, the critical temperature of the tension element according to design load, and calculated permanent and reduced live loads applied to the beam in the fire situation.

[0087] Due to the interior placement of the tension element and an inherent wooden shellconstruction surrounding the interior, a great improvement in the fire rating of an embodiment of the present disclosure compared to traditional wooden beam structures may be documented.

[0088] In another aspect, the disclosure provides a method of determining the position of the curved tubular channel in the wood-based longitudinal body of the beam according to the second aspect of the disclosure, where the curved tubular channel extend curved from a first end of the channel to a second end of the channel to be closer to the bottom face in an intermediate position between the first longitudinal end and the second longitudinal end than at the first longitudinal end and the second longitudinal end, where a vertical distance from the bottom face of the longitudinal body to the channel in the intermedial position is determined based on fire resistance requirements for the construction where the beam is to be installed.

[0089] Regarding increase in vibration-damping abilities, wooden massive traditional structures is substile towards vibrations due to the low rate of natural Frequency (Hz). During serviceability the extreme fibres in the bottom flange of a wooden beam is not optimal for absorbing dynamic loads from pedestrians, footfall etc. resulting in acceleration and vibration of the wooden structure, globally and locally. Traditionally in order to obtain and increase the wooden systems frequency, locally and globally, more permanent loads are added to the system.

[0090] The own natural frequency (Hz) of wood structures is often the most dominant factor in determining the maximum span of the beam. The wood-based beam according to the present disclosure is under constant pressure due to the post tensioned system applied in the structure of the beam. In a preferred embodiment, no fibre in the beam-structure is in tension, during the serviceability, creating a more stiff and rigid structure and a dampening effect.

[0091] This results in a greatly increased natural frequency (Hz) compared to traditional wooden structures.

[0092] In yet another aspect, the disclosure provides a method of manufacturing the beam according to the second aspect of the disclosure, the method comprising the steps of:

[0093] - providing a longitudinal body of a wood-based material, the longitudinal body comprising two body parts,

[0094] - arranging a curved channel in the longitudinal body by recessing a part of the curved channel into each of the two body parts,

[0095] - arranging a tension element in one of the two recessed parts of the curved channel,

[0096] - interconnecting the two body parts.

[0097] The step of interconnecting the two body parts may comprise a step of adhesively connecting the body parts and / or a step of connecting the body parts by transversely extending engagement elements. The tension element may alternatively be arranged in the channel after the two body parts are interconnected. The latter allows for arrangement of the tension element on-site after transporting the longitudinal body and the tension element to the construction site before final assembling of the beam.

[0098] It should be understood, that a skilled person would readily recognise that any feature described in combination with the first and second aspects of the disclosure could also be combined with the aspect of manufacturing the beam.

[0099] In a third aspect, the disclosure provides a building construction comprising at least one beam and at least a first and a second support element, the beam comprising a longitudinal body of a wood-based material, the longitudinal body extending in a longitudinal direction and having a height dimension (h), a width dimension (w) perpendicular to the height dimension (h), and a longitudinal dimension (I) perpendicular to the height dimension (h) and the width dimension (w), the longitudinal body having a first longitudinal end and an opposite second longitudinal end in the longitudinal direction; a top face and an opposite bottom face, the top face being uppermost in an intended position of installation; and two side faces opposite to each other, the top face, the bottom face, and the two side faces extending between the first longitudinal end and the second longitudinal end, a channel extending through the body in the longitudinal direction from a first end of the channel at the first longitudinal end to a second end of the channel at the second longitudinal end, where the first end of the channel is closer to the bottom face than the second end of the channel, and a tension element extending through the channel, said tension element being a longitudinal element having a first end and a second end, said first end and second end of the tension element being fastened respectively at the first end and the second end of the channel, the tension element being fastened at at least one of the first end and the second end of the channel by an adjustable means for adjusting a pull provided in the tension element, and wherein the beam at the first longitudinal end is supported by the first support element, and wherein the beam is supported by the second support element at a cantilever distance from the second longitudinal end.

[0100] In a fourth aspect, the disclosure provides a method of erecting a construction according to the third aspect of the disclosure, the method comprising the steps of:

[0101] - providing a first support element and a second support element, the first and second support elements being arranged at a distance from each other in a horizontal direction,

[0102] - positioning the beam in a first configuration on the first and second support element, where the first longitudinal end is arranged at the first support element, and where the second longitudinal end is arranged at a cantilever distance to the second support element,

[0103] - applying a load to the beam; and

[0104] - subsequently post tensioning the beam by applying a pull in the tension element by the adjustable means bringing the beam into a second configuration, while the load is applied. It should be understood, that a skilled person would readily recognise that any feature described in combination with the first and second aspects of the disclosure could also be combined with the third and fourth aspects of the disclosure.

[0105] When positioning the beam in the first configuration on the first and second support element, stress may occur in the beam, particularly stress in the wood fibres in the upper part and the lower part of the wood-based longitudinal body. Thus, the first configuration may be characterized by stresses in the upper and lower parts of the body which may at least partly occur due to the self-weight of the beam, both in the part supported between the first and second support elements, and the cantilevered part.

[0106] Subsequent to the step of positioning the beam in the first configuration on the first and second support elements, a load is applied to the beam. The load may be a permanent load of building construction parts carried by the beam. When applying the load, the stresses in the beam may change, which may bring the beam into an intermediate configuration.

[0107] Subsequent to the step of applying the load to the beam, the beam is post tensioned, while the load is still applied. The beam is post tensioned by applying a pull in the tension element by the adjustable means to thereby adjust the pull provided by the tension element. The applied pull brings the beam into a second configuration.

[0108] The cantilever distance may as an example be in the range of 0.5-9 m, or even longer, dependent on the specific project requirements.

[0109] Brief description of the drawinqs

[0110] In the following the disclosure will be further illustrated by means of non-limiting examples having reference to the accompanying schematic drawings, in which

[0111] Fig. 1 is an exploded view of a beam according to the present disclosure;

[0112] Fig. 2 is a longitudinally sectioned side view of the beam of Fig. 1;

[0113] Fig. 3 is a schematic top view of the lower half of the beam;

[0114] Fig. 4 is a schematic top view of the upper half of the beam;

[0115] Fig. 5 is a cross-sectional view of the beam: Fig. 6 is a vertically sectioned view of a capsule element;

[0116] Fig. 7 is a sectional view as indicated by line VII-VII in Fig. 6;

[0117] Fig. 8 is a sectional view as indicated by line VIII-VIII in Fig. 6;

[0118] Figs. 9A-9D illustrate embodiments of a beam comprising a plurality of tension elements;

[0119] Fig. 10 illustrates an alternative embodiment of a beam comprising a plurality of beam sections; and

[0120] Fig. 11 illustrates a further alternative embodiment of a beam.

[0121] Detailed ion of the

[0122] Figs. 1-4 show a beam 1 comprising a longitudinal body 3 of wood-based material. The wood-based material may e.g. be lumber, structural timber, or laminated wood, e.g. such as glulam, laminated veneer lumber (LWL), Glue-laminated timber (GLT), Cross-laminated timber (CLT). The beam comprises a longitudinal body 3 extending in a longitudinal direction 5. The longitudinal body 3 has a height dimension h, a width dimension w perpendicular to the height dimension h, and a longitudinal dimension I perpendicular to the height dimension h and the width dimension w. The longitudinal body 3 has a first longitudinal end 11 and an opposite second longitudinal end 13 in the longitudinal direction 5. Further the longitudinal body has a top face 15 and an opposite bottom face 17, wherein the top face 15 is uppermost in an intended position of installation; and two side faces 21 opposite to each other. The top face 15, the bottom face 17, and the two side faces 21 are extending between the first longitudinal end 11 and the second longitudinal end 13 of the longitudinal body 3.

[0123] A channel in the form of a curved tubular channel 23 is extending through the longitudinal body 3 in the longitudinal direction 5. Thus, the curved tubular channel 23 is extending curved from a first end 25 of the channel 23 to a second end 27 of the channel 23 to be closer to the bottom face 17 in an intermediate position 29 between the first longitudinal end 11 and the second longitudinal end 13 than at the first longitudinal end 11 and the second longitudinal end 13.

[0124] A tension element 31 is extending through the channel 23. The tension element 31 is a longitudinal element having a first end 33 and a second end 35, wherein the first end 33 and the second end 35 of the tension element 31 is fastened respectively at the first end 25 and the second end 27 of the channel 23. The tension element 31 is at least at the first end 25 or the second end 27 of the channel 23 fastened by an adjustable means 37 for adjusting a pull provided by the tension element 31.

[0125] The tension element 31 is in the embodiment shown a long slim body and may e.g. be a steel rod or a steel wire. The tension element 31 is in the embodiment shown provided with an externally threaded part at either end 33 and 35 (not shown in detail) and the adjustable means 37 are, in the embodiment shown, provided as a nut with internal threads whereby tension of the tension element 31 can be adjusted by rotating the adjustable means 37, as it will be appreciated by the skilled person.

[0126] The curve through which the channel 23 is extending may e.g. be a parabolic curve.

[0127] At the first end 25 and / or the second end 27 of the channel 23 the tension element 31 is supported by an anchor plate 39. The anchor plate 39 is provided with a hole 39a and the adjustable means 37 and / or the tension element 31 extend through the hole 39a for the adjustable means 37 to abut against the anchor plate 39 on the far side thereof relative to the longitudinal body 3, possibly by means of a flange on the adjustable means 37 (not shown in particular detail) whereby the tension element 31 is supported by the anchor plate 39 through the adjustable means 37. Thus, the adjustable means may comprise flange forming a wedge-like structure configured to engage the opening 39a into an anchor plate 39. The opening 39a may have a conical shape configured to provide geometrical locking of the wedge-like structure.

[0128] Transverse elongated elements 41, especially mechanical penetrating elements, preferably studs or bolts, are extending tangentially relative to the channel 23, above the channel 23. The transverse elongated elements 41 are e.g. shown in Figs 1 and 5 as bolts with nuts 41a. The bolts are penetrating thought the material of the longitudinal body 3 to receive the nuts 41a by means of which the bolts are tightened about the longitudinal body 3. In addition, the transverse elongated elements 41 provide relief for the wood-based material of the longitudinal body 3 bordering the channel 23 to allow for greater tension of the tension element 31.

[0129] At its outmost ends in the longitudinal direction 5 the longitudinal body 3 comprises a first end face 45 and a second end face 47 respectively at the first longitudinal end 11 and the second longitudinal end 13. In the embodiment shown, the first end 25 and the second end 27 of the channel 23 is placed respectively in the first end face 45 and the second end face 47. The end faces 45, 47 where the ends 25, 27 of the channel 23 are placed are covered by the anchor plates 39.

[0130] In the embodiment shown, the anchor plate 39 is part of a capsule element 49 comprising the anchor plate 39 and flanges 50 extending along the top face 15, the bottom face 17, and the two side faces 21, whereby the flanges 50 are provided as parts of a tubular section with a rectangular cross-section as shown especially in Fig. 8. This provides a box-like structure of the capsule element 49 that provides good protection of the end 11, 13 of the longitudinal body 3 and provides an enhanced transfer of tension or tendon forces from the tension element towards the ends 11, 13 of the longitudinal body 3. The tubular section circumscribes the end of the longitudinal body as an unbroken band. In the embodiment shown the capsule element 49 also retain an elastic element 51 or elastomeric pads together with the wood-based material or timber in the zone where the stress at the end 25, 27 of the channel 23 is more localized. Thus, an elastic element 51 with a higher elasticity than the anchor plate 39 is inserted between the end face 45, 47 and the anchor plate 39 covering said end face.

[0131] Hereby an increased tension capacity may be obtained by avoiding bursting of materials and directing compression-forces into the beam material inside the box-like structure.

[0132] To provide the channel 23, the longitudinal body 3 comprises two body parts 53 provided on respective sides of a vertical longitudinal plane p extending in the longitudinal direction 5. The body parts 53 each has an engaging face 57 and in the completed beam 1 the engaging faces are engaging each other. The channel 23 is recessed into at least one of the engaging faces 57.

[0133] In the embodiment shown, a part of the channel 23 is recessed into each of the engaging faces 57, whereby the channel 23 is completed when the two body parts 53 are connected to each other.

[0134] The two body parts 53 may be interconnected by diffident means, such as by adhesive applied to the engaging faces 57; transverse elongated elements or mechanical penetrating elements, such as screws, bolts, nails; etc. In the present embodiment glue applied to the engaging surfaces is envisaged together with the transverse elongate elements 41 or bolts and nuts 41a that, as mentioned above, will have the function of participating in securing the two body parts 53 to each other.

[0135] In the shown embodiment an additional longitudinal compression element 59 is applied at the top face 15. A portion of the beam 1 at the top face 15, especially a central longitudinal portion of the beam 1 at the top face 15 may be subject to significant compression stresses arising from the prestressing force or tension of the tension element 31. In certain cases, such as in case of a beam 1 providing a very long span and has a large longitudinal dimension I, or in case of a beam 1 intended for a very heavy load, whereby the prestressing force or tension of the tension element 31 need to be very high, the material of the longitudinal body 3 at the top face 15, especially a central longitudinal portion of the longitudinal body 3 at the top face 15 may be subject to excessive compression stresses arising from the prestressing force or tension of the tension element 31 relative to strength of compression of the material. In such case providing an additional longitudinal compression element 59 is applied at the top face 15 will provide the extra strength needed by the circumstances.

[0136] The longitudinal compression element 59 is provided in a recess 61 in the top face 15. The recess 61 and the longitudinal compression element 59 have a width 63 smaller than the width dimension w of the longitudinal body 3 and are extending a distance 65 from the top face 15 towards the bottom face 17. Hereby a part of the timber section of the longitudinal body 3, i.a. a part of the wooden material of the beam 1, is replaced by a stronger i.e. a more compression resistant material.

[0137] In the shown embodiment, in the longitudinal direction 5 the longitudinal compression element 59 is extending a distance 67 shorter than a length of the tension element 31 in the longitudinal direction 5. In the embodiment shown the longitudinal compression element 59 is extending a distance of approx. 50-60% of the length of the tension element 31. Hereby a freedom of design relating to the ends 25, 27 of the channel 23 and their position is provided since a risk of the channel interfering with the longitudinal compression element is minimized. In the embodiment shown the ends 25, 27 of the channel 23 are provided centrally in the end faces 45, 47 of the longitudinal body 3. It is however possible e.g. to shift the position of the ends 25, 27 of the channel 23 towards the top face 15 without the channel 23 thereby interfering with the recess 61 and the longitudinal compression element 59.

[0138] In the embodiment shown, the longitudinal compression element 59 comprises concrete, e.g. concrete C60 / 75.

[0139] As indicated by arrow 69 (see Fig. 5) the longitudinal compression element 59 may be penetrated by at least one mechanical fastening element similar to the transverse elongate elements 41, preferably extending perpendicular to the longitudinal direction 5, and further preferably extending parallel to the width dimension w. When producing the beam 1 it is possible to mount e.g. bolts with nuts like the transverse elongate elements 41 and the nuts 41a at one or more places as indicated by the arrow 69 after the recess 61 has been provided but prior to casting or pouring concrete into the recess 61. Thereby the transverse elongate elements 41 will in a convenient way be provided to extend through the longitudinal compression element 59 and adhesion between the transverse elongate elements 41 and concrete of the longitudinal compression element 59 will be provided to enhance the overall stability of the beam 1.

[0140] In a method of installing the beam 1, the beam 1 placed in its intended non-vertical, preferably substantially horizontal position in which the longitudinal dimension of the beam 1 is non-vertical, preferably substantially horizontal position. After the beams has been positioned, and a load has been applied, a pull is provided in the tension element 31 to posttension of the beam 1. Thereby it is avoided that a pre-stress of the tension element 31 deforms the beam 1 in an unintended manner prior to installation and loading of the beam 1.

[0141] Figs. 9A-9D illustrate four different embodiments of a beam 1 comprising a plurality of tension elements 31, 31A. Each of Figs. 9A-9D illustrates a cross-sectional view of the beam 1 comprising more than one tension element extending through a tubular channel through the wood-based longitudinal body.

[0142] In the embodiment illustrated in Figs. 9A, 9B, and 9C, the beam 1 comprises a channel 23 and an additional channel 23A extending substantially in parallel through the longitudinal body. The additional channel 23A extend at a channel distance dl to the channel. In the embodiment illustrated in Fig. 9D, the beam 1 comprises two additional channels 23A.

[0143] A tension element 31 extends through the channel 23, and an additional tension element 31A extends through the additional channel 23A.

[0144] In the embodiments illustrated in Figs. 9A and 9B, the channel distance dl are equal and correspond substantially to half the width of the longitudinal body 3. The additional channel 23A and the channel 23 are each arranged at a distance d2 from the side face 21 of the longitudinal body 3, where the distances d2 is half the channel distance dl.

[0145] The embodiments illustrated in Figs. 9A and 9B are identical with the exception, that the beam 1 illustrated in Fig. 9A comprises four longitudinal body parts 53, whereas the beam 1 illustrated in Fig. 9B comprises only three longitudinal body parts 53, the longitudinal body parts provided on respective sides of vertical longitudinal planes (p) extending in the longitudinal direction.

[0146] An additional longitudinal compression element 59 is arranged in a recess in the top face 15 of the longitudinal body 3. And a plurality of transversely extending elongated elements 41 are arranged in contact with the channel 23 and the additional channel 23A above the channel 23 and the additional channel 23A.

[0147] The embodiment of the beam 1 illustrated in Fig. 9C is similar to the embodiment of Fig. 9B with the exception that the width of the longitudinal body 3 is smaller and that the channel distance dl is smaller than in Fig. 9B.

[0148] The embodiment of the beam 1 illustrated in Fig. 9D comprises a total of three tension elements 31, 31A.

[0149] Fig. 10 illustrates an alternative embodiment of a beam 1 having a longitudinal body comprising two body sections 71 provided on respective sides of a vertical longitudinal plane pl extending perpendicular to the longitudinal direction, where the body sections 71 have respective engaging section faces engaging each other.

[0150] The curved tubular channel 23 extends through the longitudinal body 3 formed by two body sections 71 from a first end 25 of the channel to a second end 27 of the channel to be closer to the bottom face 17 at two intermediate positions between the first longitudinal end 11 and the second longitudinal end 13 than at the first longitudinal 11 end and the second longitudinal end 11. Thus, the curved tubular channel 23 comprises two downwardly extending curved sections 23', two upwardly extending curved sections 23" and two positions 23b where the channel 23 is closer to the bottom face 17 than at the first and second longitudinal ends 11, 13 of the longitudinal body 3, whereby the curved channel 23 has the shape of a curved W.

[0151] The first and second openings 25', 27' into the channel 23 at the first longitudinal end 11 and at the second longitudinal end 13 of the longitudinal body are arranged substantially centrally relative to the height of the longitudinal body 3. The intermediate top section 23t of the W- shaped channel 23 is arranged closer to the top face 15 than the openings 25', 27' at the first and the second longitudinal ends 11,13.

[0152] The tension element 31 extends through the channel 23 through both body sections 71 and is fastened at the first end 25 and / or at the second end 27 of the channel 23 by adjustable means (not shown in Fig. 10) for adjusting a pull provided in the tension element. A plurality of transversely extending elongated elements 41 are arranged in contact with the channel 23 to provide enhanced support for the tension element 31 along the channel 23. Along most of the length of the tension element 31, the elongated elements 41 are arranged above the channel 23 to take into account the tension provided by post-tensioning the beam 1. However, in the area of the intermediate top section 23t of the W-shaped channel, the elongated element 41 are arranged below the channel, to thereby take into account the tension provided in this area.

[0153] The beam 1 is supported by a first and a second support element 75, 77 at opposite ends 11, 13 of the beam. In the illustrated embodiment, an additional support element 79 supports the beam 1 at the interface between the two body sections 71. Two additional longitudinal compression elements 59 are applied in a recess at the top face 15, one in each body section 71.

[0154] Fig. 11 illustrates a further alternative embodiment of a beam 1. The beam 1 comprises a longitudinal body 3 of a wood-based material and being formed by two body sections 71. The longitudinal body 3 extends between a first longitudinal end 11 and an opposite second longitudinal end 13.

[0155] A channel 23 extends through the body 3 in the longitudinal direction from a first end 25 to a second end 27. The first end 25 of channel is closer to the bottom face 17 than the second end 27 of the channel. A tension element 31 extending through the channel 23 and is fastened respectively at the first end 25 and the second end 27 of the channel 23. At the first end 25 and / or at the second end 27, tension element 31 is fastened by adjustable means (not shown in Fig. 11) for adjusting a pull provided in the tension element (31).

[0156] The beam 1 is at the first longitudinal end 11 is supported by a first support element 75. The beam 1 is supported by a second support element 77 at a cantilever distance d3 from the second longitudinal end 13. The cantilever part of the beam 1 may be supported by one or more temporary support element while applying the load, until a pull has been provided in the tension element 31 to thereby post-tension the beam 1.

[0157] A plurality of transversely extending elongated elements 41 are arranged in contact with the channel 23 to provide enhanced support for the tension element 31 along the channel 23.

Claims

27CLAIMS1. A method of installing a beam (1) in a construction, the beam (1) comprising a longitudinal body (3) of a wood-based material, the longitudinal body extending in a longitudinal direction (5) and having a height dimension (h), a width dimension (w) perpendicular to the height dimension (h), and a longitudinal dimension (I) perpendicular to the height dimension (h) and the width dimension (w), the longitudinal body (3) having a first longitudinal end (11) and an opposite second longitudinal end (13) in the longitudinal direction (5); a top face (15) and an opposite bottom face (17), the top face (15) being uppermost in an intended position of installation; and two side faces (21) opposite to each other, the top face (15), the bottom face (17), and the two side faces (21) extending between the first longitudinal end (11) and the second longitudinal end (13), a channel (23) in the form of a curved tubular channel (23) extending through the body (3) in the longitudinal direction (5), said curved tubular channel (23) extending curved from a first end (25) of the channel (23) to a second end (27) of the channel (23) to be closer to the bottom face (17) in an intermediate position (29) between the first longitudinal end (11) and the second longitudinal end (13) than at the first longitudinal end (11) and the second longitudinal end (13), and a tension element (31) extending through the channel (23), said tension element (31) being a longitudinal element having a first end (33) and a second end (35), said first end (33) and second end (35) of the tension element (31) being fastened respectively at the first end (25) and the second end (27) of the channel (23), the tension element (31) being fastened at at least one of the first end (25) and the second end (27) of the channel (23) by an adjustable means (37) for adjusting a pull provided in the tension element (31), the method comprising the step of:- providing a first support element and a second support element, the first and second support elements being arranged at a distance from each other in a horizontal direction,- positioning the beam (1) in a first configuration on the first and second support element, where the first longitudinal end (11) is arranged closer to the first support element than the second longitudinal end (13), and where the second longitudinal end (13) is arranged closer to the second support element than the first longitudinal end (11),- applying a load to the beam (1); and- subsequently post tensioning the beam (1) by applying a pull in the tension element by the adjustable means (37) bringing the beam (1) into a second configuration, while the load is applied.

2. The method according to claim 1, wherein the longitudinal body (3) forms a downwardly deflecting shape between the first and second support elements in the first configuration.

3. The method according to claim 1 or 2, wherein the top face (15) of the longitudinal body forms a substantially plane surface in the second configuration.

4. The method according to any of the preceding claims, wherein the step of post tensioning the beam (1) by applying a pull in the tension element by the adjustable means (37) is carried out by applying a pull in the tension element at at least one of the first and second ends (33, 35).

5. The method according to any of the preceding claims, further comprising a step of providing an additional support element, wherein the step of positioning the beam (1) on the first and second support element comprises positioning the beam (1) on the additional support element, the method comprising a further step of removing the additional support element after the step of post tensioning the beam.

6. A beam (1) comprising a longitudinal body (3) of a wood-based material, the longitudinal body (3) extending in a longitudinal direction (5) and having a height dimension (h), a width dimension (w) perpendicular to the height dimension (h), and a longitudinal dimension (I) perpendicular to the height dimension (h) and the width dimension (w), the longitudinal body (3) having a first longitudinal end (11) and an opposite second longitudinal end (13) in the longitudinal direction (5); a top face (15) and an opposite bottom face (17), the top face (15) being uppermost in an intended position of installation; and two side faces (21) opposite to each other, the top face (15), the bottom face (17), and the two side faces (21) extending between the first longitudinal end (11) and the second longitudinal end (13), a channel (23) in the form of a curved tubular channel (23) extending through the body (3) in the longitudinal direction (5), said curved tubular channel (23) extending curved from a first end (25) of the channel (23) to a second end (27) of the channel (23) to be closer to the bottom face (17) in an intermediate position (29) between the first longitudinal end (11) and the second longitudinal end (13) than at the first longitudinal end (11) and the second longitudinal end (13), anda tension element (31) extending through the channel (23), said tension element (31) being a longitudinal element having a first end (33) and a second end (35), said first end (33) and second end (35) of the tension element (31) being fastened respectively at the first end (25) and the second end (27) of the channel (23), the tension element (31) being fastened at at least one of the first end (25) and the second end (27) of the channel (23) by an adjustable means (37) for adjusting a pull provided in the tension element (31).

7. The beam (1) according to claim 6, wherein the tension element (31) is supported by an anchor plate (39) at least at one of the first end (25) and the second end (27) of the channel (23).

8. The beam (1) according to claim 6 or 7, wherein the tension element (31) comprises a plurality of tension components each extending from the first end (33) to the second end (35).

9. The beam (1) according to any of claims 6-8, wherein a diameter of the channel (23) is at least 2% larger than a diameter of the tension element (31).

10. The beam (1) according to any of claims 6-9, wherein at least a part of the channel (23) forms a parabolic curve.

11. The beam (1) according to any of claims 6-10, wherein elongated elements (41) extend transverse to the channel (23), above the channel (23).

12. The beam according to claim 11, wherein the elongated elements (41) extend tangentially to the channel (23).

13. The beam according to claim 11 or 12, comprising at least 5 elongated elements (41).

14. The beam (1) according to any of claims 6-13, wherein the longitudinal body (3) at outmost ends in the longitudinal direction (5) comprises a first end face (45) and a second end face (47) respectively at the first longitudinal end (11) and the second longitudinal end (13), and wherein at least one of the first end (25) and the second end (27) of the channel (23) is placed respectively in the first end face (45) and the second end face (47).

15. The beam according to claim 14, wherein a first opening into the channel at the first end (25) is arranged with a first distance to the top face (15) and a second distance to the bottom face (17), the first distance and the second distance being substantially equal.

16. The beam according to claim 14 or 15, wherein a second opening into the channel at the second end (27) is arranged with a third distance to the top face (15) and a fourth distance to the bottom face (17), the third distance and the fourth distance being substantially equal.

17. The beam (1) according to claim 16, wherein the end face(s) in which the end(s) of the channel (23) is placed are covered by the anchor plate (39).

18. The beam (1) according to claim 17, wherein the anchor plate (39) is part of a capsule element (49) comprising the anchor plate (39) and flanges (50) extending along at least one of the top face (15), the bottom face (17), and the two side faces (21)19. The beam (1) according to claim 18, wherein the capsule element (49) circumscribes the respective one of the first longitudinal end (11) and the second longitudinal end (13) of the longitudinal body (3) adjacent the end face thereof.

20. The beam (1) according to any of claims 17-19, wherein an elastic element (51) with a higher elasticity than the anchor plate (39) is inserted between the end face and the anchor plate (39) covering said end face.

21. The beam (1) according to any one of claims 6-20, wherein the longitudinal body (3) comprises two body parts (53) provided on respective sides of a vertical longitudinal plane (p) extending in the longitudinal direction (5), said body parts (53) having respective engaging faces (57) engaging each other, the channel (23) being recessed into at least one of the engaging faces (57).

22. The beam (1) according to claim 21, wherein a part of the channel (23) is recessed into each of the engaging faces (57).

23. The beam (1) according to claim 21 or 22, wherein the two body parts (53) are interconnected by at least one of: adhesive applied to the engaging faces, and mechanical penetrating elements.

24. The beam (1) according to any of claims 6-23, wherein an additional longitudinal compression element (59) is applied at the top face (15).

25. The beam (1) according to claim 24, wherein the longitudinal compression element (59) is provided in a recess (61) at or in the top face (15), said recess (61) having a width (63)31 smaller than the width dimension (w) of the longitudinal body (3) and extending a distance (65) from the top face (15) towards the bottom face (17).

26. The beam (1) according to claim 24 or 25, wherein the longitudinal compression element (59) in the longitudinal direction (5) is extending a distance (67) shorter than a length of the tension element (31).

27. The beam (1) according to any of claims 24-26, wherein the longitudinal compression element (59) comprises a material having a higher compressive strength than the woodbased body.

28. The beam (1) according to any of claims 24-26, wherein the longitudinal compression element (59) is penetrated by at least one mechanical fastening element extending into the wood-based body.

29. The beam (1) according to any of claims 6-28, comprising an additional channel (23A) extending substantially parallel to the channel (23), the additional channel (23A) extending at a channel distance to the channel (23), and comprising an additional tension element (31A) extending through the additional channel (23A).

30. The beam (1) according to claims 29, wherein the longitudinal body (3) comprises three body parts (53) provided on respective sides of vertical longitudinal planes (p) extending in the longitudinal direction (5), said body parts (53) having respective engaging faces (57) engaging each other, the channel (23) and the additional channel (23A) each being recessed into at least one of the engaging faces (57).

31. A building construction comprising at least one beam (1) and at least a first and a second support element, the beam (1) comprising a longitudinal body (3) of a wood-based material, the longitudinal body (3) extending in a longitudinal direction (5) and having a height dimension (h), a width dimension (w) perpendicular to the height dimension (h), and a longitudinal dimension (I) perpendicular to the height dimension (h) and the width dimension (w), the longitudinal body (3) having a first longitudinal end (11) and an opposite second longitudinal end (13) in the longitudinal direction (5); a top face (15) and an opposite bottom face (17), the top face (15) being uppermost in an intended position of installation; and two side faces (21) opposite to each other, the top face (15), the bottom face (17), and the two side faces (21) extending between the first longitudinal end (11) and the second longitudinal end (13),32 a channel (23) extending through the body (3) in the longitudinal direction (5) from a first end (25) of the channel (23) at the first longitudinal end (11) to a second end (27) of the channel (23) at the second longitudinal end (13), where the first end of the channel is closer to the bottom face (17) than the second end of the channel, and a tension element (31) extending through the channel (23), said tension element (31) being a longitudinal element having a first end (33) and a second end (35), said first end (33) and second end (35) of the tension element (31) being fastened respectively at the first end (25) and the second end (27) of the channel (23), the tension element (31) being fastened at at least one of the first end (25) and the second end (27) of the channel (23) by an adjustable means (37) for adjusting a pull provided in the tension element (31), and wherein the beam at the first longitudinal end is supported by the first support element, and wherein the beam is supported by the second support element at a cantilever distance from the second longitudinal end.

32. A method of erecting a construction according to claim 31, the method comprising the steps of:- providing a first support element and a second support element, the first and second support elements being arranged at a distance from each other in a horizontal direction,- positioning the beam (1) in a first configuration on the first and second support element, where the first longitudinal end (11) is arranged at the first support element, and where the second longitudinal end (13) is arranged at a cantilever distance to the second support element,- applying a load to the beam (1); and- subsequently post tensioning the beam (1) by applying a pull in the tension element by the adjustable means (37) bringing the beam (1) into a second configuration, while the load is applied.

Images