EP3553243B1

EP3553243B1 - Laminated log structure, method and use

Info

Publication number: EP3553243B1
Application number: EP19167747.5A
Authority: EP
Inventors: Jukka Rintamäki
Original assignee: Honkarakenne Oyj
Current assignee: Honkarakenne Oyj
Priority date: 2018-04-09
Filing date: 2019-04-08
Publication date: 2023-06-07
Anticipated expiration: 2039-04-08
Also published as: EP3553243C0; EP3553243A1; FI20185329A1; FI129236B

Description

TECHNICAL FIELD

The invention relates to a laminated log structure, such as a laminated log wall, and to construction using laminated logs.

BACKGROUND

A laminated log is a solid log manufactured from several lamellas and widely used in log construction. Assembling laminated logs into a laminated log structure, such as a laminated log wall, typically requires the use of one or more support structures in order to obtain sufficient stability for the structure to carry several superposed laminated logs. Such support structures include various types of wood pegs, metal tubes and metal clamping bolts, which may all be used to support a single laminated log structure. When capacity of the pegs alone is not sufficient, steel tubes must be used. Typically, one or more support structures, such as metal tubes, must be laid in the vertical direction through the whole laminated log structure, so that the stability of the structure becomes sufficient for the laminated logs.
The use of several support structures makes the laminated log structure complex, which has direct implications on the materials being used and the time needed for installation and manufacture, as well as on the likelihood of mistakes during these operations.
As an example, EP0226567A2 discloses a built-up sectional beam for the erection of load-bearing or non-load bearing walls. EP3098360A1 discloses a non-settling log structure.

OBJECTIVE OF THE INVENTION

The objective of the invention is to remedy or alleviate at least some of the deficiencies mentioned above.
Specifically, the objective is to provide a laminated log structure which may be installed without pegs, support tubes and clamping bolts, but which may still give sufficient stability for the laminated log structure.

SUMMARY

In the invention, laminated logs including both vertical- and horizontal-grain-direction lamellas are utilized. The laminated log may be a rectangular, i.e. a square laminated log. A horizontal-grain-direction lamella refers herein to a lamella, i.e. a wood plate, in which the wood grain runs substantially horizontally when the laminated log lies in a horizontal plane. Specifically, the grain may in this case run in the longitudinal direction of the laminated log, which is also the longitudinal direction of the raw material timber. A vertical-grain-direction lamella refers, correspondingly, to a lamella in which the wood grain runs substantially vertically when the laminated log lies in a horizontal plane. The vertical-grain-direction lamella may be produced by fastening several vertical-grain-direction pieces of wood side by side, for example directly to each other by gluing. This allows the vertical-grain-direction lamella to be equally long as the horizontal-grain-direction lamella, notwithstanding that the length of the raw material timber is to a significant extent greater than its width. The structural parts of logs, and specifically of laminated logs, are defined for example in standard SFS 5973. The advantage of a laminated log, for example compared to a solid planed log, is the possibility to provide very dry and uniform-quality timber. This in turn reduces reshaping of the final structure due to humidity, i.e. changes in the width and height of the structure. Also, cracking and settling of the structure may be reduced. By means of gluing, the structure may also be rendered substantially non-warping and non-twisting.
The laminated log structure according to the invention may be, for example, a laminated log wall. The height of the laminated log structure may be more than 1 meter, for example the room height, i.e. at least 2 meters, or more specifically at least 2.4 meters. The height of the laminated log structure may also be at least the floor-to-floor height, i.e. 3 meters or more. The height may thus also comprise the height of the floor base and/or roof structures, in addition to the wall height. The laminated logs may be pressed against each other for example by hammering.
In the solution according to the invention, the laminated log structure is formed by stacking the laminated logs one on top of the other, the laminated logs comprising one or more vertical-grain-direction lamellas. When the vertical lamellas are this way arranged one on top the other, they form a vertical load-bearing line that may extend substantially along the centre line of the laminated logs. In addition, the structure is substantially non-settling compared, for example, to a structure that only includes horizontal-grain-direction logs because, as the wood dries, significantly less shrinkage occurs in the vertical direction than in other directions. The laminated logs themselves are arranged horizontally in the structure, i.e. their longitudinal direction lies substantially in a horizontal plane. The laminated logs comprise at least two horizontal-grain-direction lamellas, one located, in the cross direction of the laminated log, on one side of the vertical-grain-direction lamella, and another one located on its other side. One or both of the horizontal-grain-direction lamellas may form the lateral outer face of the laminated log, for example so that the heartwood of the horizontal-grain-direction lamella opens to the outside. This may improve surface durability of the structure.
The laminated log is produced by fastening two or more separate lamellas to each other. One laminated log typically includes at least two layers of lamellas in the horizontal direction, but also more than one layer may be provided in the vertical direction. The lamellas may be fastened to each other by gluing, whereby twisting and/or cracking of the logs may be reduced. By gluing horizontal-grain-direction and vertical-grain-direction lamellas together in the laminated log, a cross-bonded laminated log is provided. The advantage of the structure is reduced settling, or substantially non-settling, which facilitates the desired outcome. As a natural material, wood also reshapes after installation, and reduced settling in the structurally essential vertical direction is in many ways relevant, not only in terms of design of the laminated log structure and special fasteners needed in the installation stage, but also in terms of the final structure and its permeability. The non-settling property of the laminated logs is important so that other materials may be joined to them directly without sliding joints. However, it is not necessarily sufficient that the laminated log alone is non-settling, but it is also important that the joint between the laminated logs is non-settling, too.
In the solution according to the invention it has been observed that it is possible to provide a laminated log structure suited for building use, such as for house building use, by fastening the superposed cross-bonded laminated logs to each other by first screws which, together with the vertical lamellas, are arranged to bear the load of the whole laminated log structure. The first screws are thus load-bearing screws that are also arranged to bind the superposed laminated logs to each other. The load-bearing screws and the vertical lamellas may together be arranged to provide a sufficient load-bearing capacity in different directions of the laminated log structure when there are several superposed laminated logs. Unlike in the laminated log structures used for years in the art, the separate load-bearing support structures such as wood pegs, metal tubes or clamping bolts are thus not needed. In other words, it may be stated that the laminated log structure according to the invention makes screw-pegging possible. The load-bearing screws and the load-bearing line formed by the vertical-grain-direction lamellas may be arranged so that the load-bearing capacity of the laminated log structure exceeds a threshold. The load-bearing screws fasten the laminated logs to each other by pairs, whereby the length of one screw is smaller than the height of two superposed laminated logs. The load-bearing screws may also receive bending moment of the laminated log structure and/or shear forces in the longitudinal direction of the laminated log. The load-bearing screw on one side of the vertical-grain-direction lamella may receive compression and on the other, opposite side it may receive tension.
The load-bearing screws are arranged to fasten to one another said at least one horizontal-grain-direction lamella of the superposed laminated logs on both sides of the one or more vertical-grain-direction lamellas. The laminated logs are thus fastened one on top of the other so that said aligned horizontal-grain-direction lamellas of the upper and lower laminated log are fastened to each other by the load-bearing screws. Arranging the load-bearing screws at the horizontal-grain-direction lamellas forms, in the laminated log structure, a vertical load-bearing line on both sides of the superposed vertical-grain-direction lamellas. There are thus at least three vertical load-bearing lines in the cross direction of the log structure: one line formed by the vertical-grain-direction lamellas, and two lines formed by the load-bearing screws. This may specifically improve the buckling capacity of the laminated log structure. The load-bearing lines may be arranged so that the buckling capacity of the laminated log structure exceeds a threshold.
In one embodiment, one or more tongue-and-groove joint elements are provided in the horizontal-grain-direction lamellas, and the load-bearing screws are arranged on or adjacent to the inner edge of the tongue-and-groove joint element. The tongue-and-groove joint element may be a tongue or a groove. Arranging the load-bearing screw adjacent to the joint element allows the screw to be hidden within the structure as far away as possible from the load-bearing line formed by the vertical-grain-direction lamellas, which may improve the buckling capacity. Fastening the screw adjacent to the inner edge of the tongue-and-groove joint element may also facilitate the manufacture and/or installation.
In one embodiment, the load-bearing screws are full-thread screws. This may improve the load-bearing capacity of the laminated log structure, which also makes it possible to form log structures extending, for example, up to the room height.
In one embodiment, the load-bearing screws on opposite sides of said one or more vertical-grain-direction lamellas are arranged by pairs along a same line substantially in the cross direction of the laminated log. This not only makes it possible to evenly distribute the load applied on the laminated log structure, but also facilitates and speeds up installation, and may also reduce mistakes during installation. In addition, pre-drilled holes may be provided for the screws by one drill unit comprising two or more bits according to the number of screws being installed, the drill unit being directed to the laminated log such that the bits are simultaneously drilled into the laminated log, so as to form said holes at the same time. There may be several pairs as described above in the longitudinal direction of the laminated log, and they may be, for example, substantially evenly spaced. The load-bearing screws of one pair may be substantially equally spaced from the vertical-grain-direction lamella and/or from the centre line of the laminated log. In one embodiment, said vertical-grain-direction lamellas of the superposed laminated logs are clamped together by second screws arranged on said line or spaced from the closest of said lines in the longitudinal direction of the laminated log by at most 50 centimetres. The second screws are thus clamping screws. By arranging the clamping screws in line with the load-bearing screws, alignment of the superposed laminated logs may be improved at the load-bearing screws so as to provide, in these specific areas, a tight laminated log structure. On the other hand, this streamlines and speeds up forming the laminated log structure, because the holes for all the aligned screws may be made by the same drill unit and at the same drilling time. One drill unit may thus comprise three or more bits according to the number of screws being installed, and it may be directed to the laminated log such that the bits are simultaneously drilled into the laminated log, so as to form said holes at the same time.
In one embodiment, the load-bearing screws are arranged, in the longitudinal direction of the laminated logs, at a spacing of 60-300 centimetres. This has been observed to provide, in many cases, a good load-bearing capacity for the laminated log structure. The load-bearing capacity may be further improved by arranging the load-bearing screws for example at a spacing of 60-90 centimetres. The load-bearing screws may also be substantially equally spaced.
In one embodiment, the load-bearing screws are arranged, in the longitudinal direction of the laminated logs, in one or more groups of 2-6 screws. This may further significantly improve the buckling capacity of the laminated log structure, and it has been observed that even a group of 2-3 screws may provide remarkable benefits. The clamping screws as mentioned above may be arranged within the groups, or for example at a distance of no more than 50 centimetres from the groups in the longitudinal direction of the laminated log. It has been observed that in many cases it is sufficient to provide one clamping screw per one group. In one group, spacing of the successive load-bearing screws may preferably be at least 7 times the diameter of one load-bearing screw, which may be for example about 8 millimetres plus/minus 0-2 millimetres. The distance between successive groups of screws may be, in the longitudinal direction of the laminated logs, for example 60-300 centimetres as measured from the centre point of the groups of screws. The groups may also be substantially equally spaced. The groups allow the buckling capacity of the laminated log structure to be increased also locally. The laminated log structure may, for example, comprise one or more groups of the load-bearing screws arranged to locally improve the buckling capacity of the laminated log structure. Thus, the laminated log structure may comprise, in the longitudinal direction of the laminated log, separate load-bearing screws as well as groups of several load-bearing screws.
In one embodiment, said one or more vertical-grain-direction lamellas of the superposed laminated logs are clamped together by second screws. The second screws are thus clamping screws, as also mentioned above. This allows the superposed vertical-grain-direction lamellas to be brought tightly together, such that the space for settling, such as installation clearances, in the vertical direction of the laminated log structure is substantially reduced, or even substantially removed. On the other hand, the clamping screws prevent the load-bearing screws from tending, during installation, to lift the upper laminated log off from the lower log. This may be particularly essential when the load-bearing screws are full-thread screws that do not clamp the joint naturally. The clamping screws clamp the laminated logs to each other by pairs, whereby the length of one screw is smaller than the height of two superposed laminated logs. The clamping screws do not necessarily need to be as densely arranged as the load-bearing screws. It has been observed that in many cases it is sufficient to provide a clamping screw at a distance of no more than 50-100 centimetres from each load-bearing screw or group of the load-bearing screws. In some cases, the distance may be up to 150 centimetres. Specifically, it should be noted that for a group of the load-bearing screws, it may be sufficient to provide one clamping screw at the above-mentioned distances at least from either edge of the group. The clamping screws may be arranged to remove the clearance, i.e. empty space, between the laminated logs. The clearance may form during installation of the laminated logs, for example if the laminated logs are not accurately installed down to the base. The clearance may also be created if the laminated log is curved in the longitudinal direction. In the solution according to the invention, the clearance may be removed or its removal ensured by the clamping screws, such that separate clamp bolting is not needed. The clamping screws may be arranged to bind the superposed laminated logs together, whereby other structures are not necessarily needed for this purpose. The clamping screws may alone produce the necessary binding effect, whereby the binding effect is not even required of the load-bearing screws.
In one embodiment, said second screws are partial-thread screws. This facilitates the clamping effect. The partial-thread screws may be fastened so that the threaded part of the screw sinks entirely into the lower one of the superposed laminated logs.
In one embodiment, the clamping screws are arranged, in the longitudinal direction of the laminated logs, at a spacing of 60-300 centimetres. Because the clamping screws do not necessarily need to be as densely arranged as the load-bearing screws, their spacing may be longer, such as 150-200 centimetres or 150-300 centimetres. The clamping screws may be located relative to the load bearing-screws or groups of the load-bearing screws as mentioned above. The clamping screws may also be substantially equally spaced.
In one embodiment, the laminated logs are formed, in the cross direction, from three or more lamellas, with the horizontal-grain-direction lamellas on the sides and the vertical-grain-direction lamella in the middle. This enables an advantageous structure in which the durable, solid horizontal-grain-direction lamellas are arranged at the outer faces of the laminated log and the vertical-grain-direction lamella forms the load-bearing line in the middle. Either one or both of the horizontal-grain-direction lamellas at the outer face of the laminated log may be arranged such that their heartwood opens to the outside. This may improve durability of the outer face.
In one embodiment, the laminated logs are formed, in the vertical direction, from two or more lamellas. This way the laminated logs can be made massive also along the height direction, even in the typical case of laminated logs where the size of the raw material is limited, for example to a height of less than 20 centimetres.
In one embodiment, pre-drilled holes are provided in the laminated logs for the screws. This may not only speed up and streamline installation, but it may also be ensured that the laminated log structure will be correctly assembled and the screws will be arranged at suitable positions to guarantee sufficient load-bearing capacity and/or clamping effect. The holes may be arranged for the load-bearing and/or the clamping screws. The diameter of the holes may be wider than the screw diameter, but it may also be wider than the screw head. In the laminated log including more than one layer in the vertical direction, the holes may be limited to the uppermost layer, whereby the screw sunk in the hole also supports gluing between the layers. The holes may be substantially equally sized for the load-bearing and for the clamping screws.
The solution according to the invention also relates to a method for forming a laminated log structure according to independent claim 14. In the method, horizontal laminated logs are arranged one on top of the other, the logs including one or more vertical-grain-direction lamellas for limiting the settling of the laminated log structure, and at least one horizontal-grain-direction lamella on both sides of the one or more vertical-grain-direction lamellas. The laminated logs are fastened to each other by first screws which, together with the vertical-grain-direction lamellas, are arranged to bear the load of the laminated log structure. The first screws are thus load-bearing screws. With the load-bearing screws, the laminated logs may be fastened together by pairs, whereby the length of the load-bearing screw is smaller than the height of two superposed laminated logs. Said one or more vertical-grain-direction lamellas of the superposed laminated logs may also be clamped together by second screws, which are thus clamping screws.
The solution also relates to the use of screws for fastening laminated logs of a laminated log structure to each other, the laminated logs including one or more vertical-grain-direction lamellas for limiting the settling of the log structure, and at least one horizontal-grain-direction lamella on both sides of the one or more vertical-grain-direction lamellas, the screws together with the vertical-grain-direction lamellas being arranged to bear the load of the laminated log structure. The screws are thus used not only to bind the logs of the laminated log structure to each other, but also to provide the load-bearing capacity of the log structure together with the vertical-grain-direction lamellas. For this purpose, specifically load-bearing screws such as full-thread screws may be used. Screws, especially when positioned at the vertical-grain-direction lamellas, may also be used to clamp the logs of the laminated log structure together. For this purpose, specifically clamping screws such as partial-thread screws may be used.
Generally, the invention enables the laminated log structure to be formed more efficiently than before, with a sufficiently high load-bearing capacity and buckling capacity of the laminated log structure, for example exceeding certain thresholds. It is also possible to form the laminated log structure quickly and efficiently because erecting the structure does not require large-scale drilling work to be performed, such as drilling work for tubes to be laid through the structure. All drill holes in the laminated log structure, and/or specifically in the vertical-grain-direction lamellas, may thus be less than 30 millimetres in diameter, for example drill holes of less than 20 millimetres. This applies specifically to drilling needed for erecting the laminated log structure, as various kinds of connection drill holes may naturally still be made in the structure, such as drill holes for electric cabling, which may even be relatively large. The drilling needed by the laminated log structure as such may only include the pre-drilling facilitating installation of the screws, extending through part of the height of the laminated logs only, for example less than 50% of the height. In practice, this may mean drill holes of, for example, 11 plus/minus 0-5 centimetres. The lack of large drill holes may significantly improve the bending, shear and/or even to a small degree the compression capacity of the laminated log structure. In case some of the drill holes are missing, they may also be made afterwards on site, which may reduce the need to return the laminated logs to factory.
Generally, the invention also facilitates installation of the laminated log structure, as it is sufficient to install only a limited number of different screw types as the fastening elements. For example, no more than two types of screws need to be used: one type of load-bearing screws and/or one type of clamping screws. This also reduces the possibility of errors during installation, and may thus improve the uniformity of the final laminated log structure.
The embodiments described above may be applied in any combination with the laminated log structure according to the invention. Several embodiments may be combined to form a new embodiment. Specifically, the laminated log structure according to the invention, as such or combined with any embodiment, may be applied in connection with the method and/or use as described above. Likewise, the steps of forming the laminated log structure according to the invention may also be carried out in connection with the above-described method and/or use.

LIST OF FIGURES

The invention will now be described in detail by way of examples of its embodiments, with reference to the accompanying drawing, in which

Fig. 1 shows one example of a laminated log in a cross-sectional view depicted in the longitudinal direction of the laminated log,
Fig. 2 shows one embodiment of a laminated log structure according to the invention in a cross-sectional view depicted in the longitudinal direction of the laminated log,
Fig. 3a illustrates examples of fastening of screws in a cross-sectional top view of the laminated log structure, and
Fig. 3b shows one embodiment of a laminated log structure according to the invention in a cross-sectional side view.

In the figures, the same reference numbers are used to indicate corresponding, or at least functionally corresponding components.

DETAILED DESCRIPTION

Fig. 1 illustrates an example of a laminated log 100. The figure shows a cross-sectional plane in the cross direction of the laminated log 100, as seen in the longitudinal direction of the laminated log 100. The laminated log 100 is formed from several lamellas 110a, 110b, 120a, 120b fastened together for example by gluing. The lamellas 110a, 110b, 120a, 120b may be substantially entirely wooden. They may be planed such that their side surfaces are substantially vertically straight. Alternatively, especially the lamella 110a arranged at the outer face of the laminated log 100 may have a curved side surface.
The laminated log 100 comprises, in the cross direction, cross-bonded such as cross-glued lamellas 110a, 120a. This means that some of the lamellas 110a, 110b are horizontal-grain-direction lamellas, and some of the lamellas 120a, 120b are vertical-grain-direction lamellas. The horizontal-grain- direction lamellas 110a, 110b are arranged substantially along the longitudinal direction of the laminated log 100, such that the wood grain of the horizontal-grain- direction lamellas 110a, 110b runs substantially in the longitudinal direction of the laminated log 100. The horizontal-grain- direction lamella 110a, 110b may be formed from one piece of wood. The vertical-grain- direction lamella 120a, 120b, on the other hand, may be formed from several pieces of wood fastened side by side for example by gluing. The horizontal-grain- direction lamellas 110a, 110b and the vertical-grain- direction lamellas 120a, 120b may thus be substantially equally long. They may also be substantially equally high, such that their upper and lower faces are substantially flush with each other. They may further be substantially equally wide, as shown in the figure, but especially in the cross direction of the laminated log 100, also many other structures are possible.
The laminated log 100 may comprise, in the vertical direction, several layers of lamellas. Fig. 1a illustrates an example of the laminated log 100 comprising two layers of lamellas, but there may also be one layer, or even more than two layers. The layers may be substantially equally high. The structures formed at the upper and/or lower face of the laminated log 100, such as tongue-and-groove joint elements 140, 142, may respectively be formed at the upper surface of the uppermost lamella 110a, 120a and/or at the lower surface of the lowermost lamella 110b, 120b. The boundary surface between the layers may be arranged to be substantially horizontally straight to facilitate fastening of the layers to each other, for example by planing. The superposed layers of one laminated log 100 may be fastened to each other for example by gluing.
The laminated log 100 comprises, in the cross direction, one or more vertical-grain- direction lamellas 120a, 120b. Fig. 1 illustrates an example of one vertical-grain- direction lamella 120a, 120b in one layer, but there may also be two or more of them, in which case there may also be other structures between them, such as one or more horizontal-grain-direction lamellas. The vertical-grain- direction lamellas 120a, 120b may be arranged symmetrically relative to a vertical line dividing the laminated log 100 in the middle. Specifically, one vertical-grain- direction lamella 120a, 120b may be situated on this centre line of the laminated log 100. If there are several layers of lamellas 100 in the laminated log 100, the vertical-grain- direction lamellas 120a, 120b of the superposed layers may be aligned to form a vertical load-bearing line. If there is only one layer in the laminated log 100, then the one or more vertical-grain-direction lamellas 120a of this layer may as such be arranged to form one or more vertical load-bearing lines in the laminated log 100.
The laminated log 100 comprises, in the cross direction, two or more horizontal-grain- direction lamellas 110a, 110b. Fig. 1 illustrates an example of two horizontal-grain- direction lamellas 110a, 110b in one layer, but there may also be three or more of them. In any case, on both sides of the vertical-grain-direction lamella of the vertical-grain- direction lamella 120a, 120b of the laminated log 100, in the cross direction of the laminated log 100, there is at least one horizontal-grain- direction lamella 120a, 120b. Either one or both of them may be arranged at the outer face of the laminated log 100. Specifically, the horizontal-grain- direction lamella 110a, 110b may be arranged at one or both of the outer faces of the laminated log 100, such that the heartwood of the horizontal-grain- direction lamella 110a, 110b opens substantially horizontally outwards from the laminated log. This may strengthen wear resistance of the outer face. Either one or both of said horizontal-grain- direction lamellas 110a, 110b may be directly fastened to the vertical-grain- direction lamella 120a, 120b, for example by gluing.
One or more tongue-and-groove joint elements 140, 142 may be provided in the laminated log 100 for aligning the superposed laminated logs 100. The tongue-and-groove joint element 140, 142 may be arranged to substantially prevent relative movement of the superposed laminated logs 100 in the cross direction of the laminated log 100. The tongue-and-groove joint element 140, 142 may extend substantially along the whole length of the laminated log 100. The tongue-and-groove joint element 140, 142 may be a tongue 140 or a groove 142. For example, one or more tongues may be provided at the upper face of the laminated log 100, and one or more grooves 142 corresponding to the tongue 140 may be provided at the lower face of the laminated log 100. The tongue-and-groove joint element 140, 142 may be arranged for example at the horizontal-grain- direction lamella 110a, 110b. For example, the horizontal-grain- direction lamellas 110a, 110b on both sides of the vertical-grain-direction lamella 120, 120b may both be provided with the tongue-and-groove joint element 140, 142. These horizontal-grain- direction lamellas 110a, 110b with the tongue-and-groove joint elements may further be arranged at the outer face of the laminated log 100, as in the solution shown in Fig. 1. However, the tongue-and-groove joint elements 140, 142 may be located, in the cross direction of the laminated log 100, towards the inner side from the outer face, so that they are arranged to be hidden between the superposed laminated logs 100. A space 150 for a seal may further be provided in the tongue-and-groove joint elements 140, 142, such as a slot arranged along the longitudinal direction of the laminated log. The seal space 150 may extend substantially along the whole length of the laminated log 100.
The laminated log 100 may be formed from solid wood pieces joined together and may thus be substantially solid. However, one or more holes 130 for screws may also be provided in the laminated log 100. The hole 130 may be pre-drilled. The vertical-grain-direction lamella 120a may be provided with its own hole 130, and/or the horizontal-grain-direction lamellas 110a may be provided with their own holes. The holes 130 may be substantially equally wide and/or high. However, in the vertical-grain-direction lamella 120a the hole 130 may be higher than the holes 130 of the horizontal-grain-direction lamellas 110a for a shorter screw. The diameter of the hole 130 may be, for example, 14 millimetres plus/minus 0-6 millimetres. The hole 130 may be a drill hole, and thus it may also be relatively large, for example 30 millimetres plus/minus 0-10 millimetres in diameter. The size of the hole 130 may also be adapted for laying cables such as electric wires in the laminated log 100. The depth of the hole 130 may be less than 100% of the height of the lamella, even when the laminated log 100 is formed from several layers of lamellas. For example in a structure with two layers, the hole may be made in one or more lamellas 110a, 120a of the upper layer, whereby the hole 130 may be for example 80% plus/minus 0-10% of the height of the upper lamella.
The length of the laminated log 100 may be several meters. The width of the laminated log 100 may be less than half a meter, for example about 20 centimetres plus/minus 0-10 centimetres. The total height of one laminated log 100 may be for example about 27 centimetres plus/minus 0-10 centimetres, which may consist, for example, of two layers of lamellas. The total height also includes the tongue-and-groove joint elements 140, 142 which are arranged to be interlocked within each other in the superposed laminated logs 100. The elevation of the laminated log 100 may be slightly smaller than the total height, for example 26 centimetres plus/minus 0-10 centimetres.
Fig. 2 illustrates an example of a laminated log structure 200 according to the invention. The figure shows a cross-sectional plane in the cross direction of two superposed laminated logs 100, as seen in the longitudinal direction of the laminated logs 100. The laminated log structure 200 may be solid, such that no separate support structures extending through the laminated log structure 200 are needed. In addition to the solid laminated logs 100, the laminated log structure 200, as it is substantially solid, may only comprise screws 210, 220 as well as the holes 130 possibly made for the screws. The laminated log structure 200 may further be provided with structures for connections, such as passages for electrical wires or edge fastening, without substantially reducing the load-bearing capacity of the structure 200. However, the laminated log structure 200 may also include one or more horizontal continuous wood surfaces extending along the whole length and width of the laminated log structure 200.
The laminated log structure 200 comprises a number of superposed laminated logs 100, for example up to the room height. The elevation of one laminated log 100 may be for example 20-30 centimetres, whereby there may be more than five, or even more than ten superposed laminated logs 100 in the laminated log structure 200. The laminated logs of the laminated log structure 200 may be substantially similar. For example, they may be equally high and/or equally long. The laminated logs 100 may also be equally wide, as the load-bearing capacity of the structure 200 is provided, on the one hand, by means of the vertical-grain- direction lamellas 120a, 120b of the superposed laminated logs 100 and, on the other hand, by means of load-bearing screws 210 used for fastening the laminated logs 100.
In the laminated log structure 200, the one of more vertical-grain- direction lamellas 120a, 120b of the superposed laminated logs 100 are aligned one on top of the other, such that they form one or more substantially vertical load-bearing lines. The load-bearing line may extend substantially along the whole height of the laminated log structure 200. The laminated logs 100 are fastened to each other by load-bearing screws 210 which, together with the load-bearing line, are arranged to bear the load of the laminated log structure 200. The load-bearing screws 210 are arranged at the horizontal-grain- direction lamellas 110a, 110b. They may further be arranged, in the superposed laminated logs 100, in alignment so that they form a substantially vertical load-bearing line. The load-bearing line of the load-bearing screws 210 may extend substantially along the whole height of the laminated log structure 210. Thus, also the horizontal-grain- direction lamellas 110a, 110b may be aligned one on top of the other substantially along the whole height of the laminated log structure 200. The load-bearing line of the load-bearing screws 210 is formed on both sides of the load-bearing line of the vertical-grain- direction lamellas 120a, 120b, such that three or more load-bearing lines may be provided in the laminated log structure 200. This may specifically improve the buckling capacity of the laminated log structure 200.
The load-bearing screws 210 may be wood screws. Specifically, they may be full-thread screws. In full-thread screws, the thread extends substantially along the whole length of the screw 210 to produce the load-bearing effect for both of the laminated logs of two superposed laminated logs 100. The load-bearing screws may be arranged to engage, through their threads, both of the laminated logs of the superposed laminated logs 100 in the laminated log structure 200, whereby one load-bearing screw 210 supports with its thread both of the superposed laminated logs 100. Each load-bearing screw 210 thus includes a threaded part for both of the laminated logs of two superposed laminated logs 100 for bearing the load of the superposed laminated logs 100 in the laminated log structure 200. The thread of the load-bearing screws 210 may be continuous, for example along the whole length of the screw. However, the thread does not need to be continuous in the load-bearing screws 210 such as full-thread screws, because the essential feature of the load-bearing screws 210 such as full-thread screws, and their thread, is their load-bearing effect in the laminated log structure 200. To produce the load-bearing effect, there must be thread on both sides of the joint. The extent and measure of the length of thread to be needed depends on the load applied on the joint, which the screw and its threaded part are arranged to receive. A person skilled in the art may size the screws by calculating the load carried by a certain length of the threaded part. To produce the load-bearing effect, the load-bearing screw 210 may thus have a thread extending for example at least through 70-80 per cent of the length of the screw. Another important advantage is provided when the load-bearing screws 210 are arranged to fasten to one another said at least one horizontal-grain- direction lamella 110a, 110b of the superposed laminated logs 100 on both sides of the one or more vertical-grain- direction lamellas 120a, 120b. This is because such load-bearing screws 210 at the edges of the laminated log also stabilize the wall structure. After installation, a laminated log structure such as a laminated log wall is always subject to a bending moment as well, whereby one of such load-bearing screws 210 receives compression while the other one receives tension. The middle lamella of the laminated log 100 may then lie on the neutral axis.
The load-bearing screws 210 may be cone-headed, such that the head may sink in the wood, specifically in the horizontal-grain-direction lamella 110a. The length of the load-bearing screws 210 may substantially correspond to the height of the laminated log 100, for example it may be 50-150% of the height of the laminated log 100. The length may be for example about 30 plus/minus 0-10 centimetres. If no pre-drilling 130 is provided, the screw 220 may need to be longer, for example such that the necessary length is about 150 plus/minus 0-25 per cent of the height of the laminated log 100. In practice, this may be about 40 plus/minus 0-10 centimetres. Specifically, when two layers are provided in the laminated log 100, the length of the load-bearing screws 210 may be slightly larger than the height of the laminated log 100, such that the screws extend, after installation, from the lamella 120a of the upper layer of the upper laminated log 100 to the lamella 120b of the lower layer of the lower laminated log 100. Thus, the screws 210 may also bind the lamellas 110a, 110b of the laminated log 100 to each other.
In the cross direction of the laminated log 100, the load-bearing screws 210 may be arranged to be hidden within the laminated log structure 200. However, the load-bearing screws 210 may be arranged over an area as wide as possible. If the tongue-and-groove joint element 140, 142 is provided in the laminated log 100, the load-bearing screw 210 may be arranged for example on or adjacent to the inner edge of the tongue-and-groove joint element 140, 142, for example directly or no further than 1-2 centimetres.
The laminated logs 100 may be clamped together by clamping screws 220 arranged at the one or more vertical-grain- direction lamellas 120a, 120b. The clamping screws 220 may be arranged, in the superposed laminated logs 100, in alignment such that they form a substantially vertical line that may extend substantially along the whole height of the laminated log structure 200.
The clamping screws 220 may be wood screws. Specifically, they may be partial-thread screws. In partial-thread screws, the thread only extends for a part of the length of the screw 220, for example for a distance of about 50 plus/minus 0-25 per cent. The essential feature of the clamping screws 220 is their clamping effect by which the clearance can be removed from the load-bearing line of the vertical-grain- direction lamellas 120a, 120b. The clearance may be removed by the clamping screw 220 in which the threaded part of the screw applies a supporting force only on either one, but not both, of the laminated logs 100 to be clamped together, typically on the lower laminated log 100 of the pair of laminated logs to be clamped together. The non-threaded part of the clamping screw 220 is thus arranged on one side of the joint between the superposed laminated logs 100, for example on the upper side, and the threaded part of the clamping screw 220 is arranged entirely on the other side of the joint, for example on the lower side. The pitch of the thread of the clamping 220 screw may be larger than in the thread of the load-bearing screw 210, for example 200 plus/minus 0-50 per cent of the pitch of the thread of the load-bearing screw 210. The clamping screws 220 may be flat-headed, specifically the lower surface of the head may be flat for sinking the clamping screw 220 into the surface of the vertical-grain-direction lamella 120a. The clamping screws 220 may also be large-headed, specifically their head may be larger in diameter than in the load-bearing screws 210. The head of the clamping screw 220 may be for example 18 plus/minus 0-3 millimetres. The clamping screws 220 may be shorter than the load-bearing screws 220, specifically when the laminated log 100 is provided with the holes 130 for the clamping screws 220 and optionally also for the load-bearing screws 210. The length of the clamping screw 220 may be for example smaller than the height of the laminated log 100, for example it may be 40-90% of the height of the laminated log 100. The length may be for example 18 plus/minus 0-10 centimetres. If no holes 130 are provided, the screw 220 may need to be longer, and the clamping screws 220 may in this case be substantially equally long as the load-bearing screws 210.
Fig. 3a illustrates several examples of arrangement of the screws 210, 220 in the laminated log structure 200. The figure is a cross-sectional top view of the laminated log structure 200. The figure illustrates various positioning configurations for the screws 210, 220, which may be used in the same or different embodiments of the invention. The load-bearing screws 210 are indicated in the figure by circles (o) and the clamping screws 220 are indicated by crosses (x).
All the load-bearing screws 210 needed to bear the load of the laminated log structure 200 may be located at the horizontal-grain- direction lamellas 110a, 110b. All the clamping screws 220 needed for clamping the vertical-grain- direction lamellas 120a, 120b of the laminated log structure 200 may, in turn, be located at the vertical-grain- direction lamellas 120a, 120b. The load-bearing screws 210 may be arranged by pairs in the cross direction of the laminated log 100, such that two load-bearing screws 210 are in a pair along a same line 310 in the cross direction but on different sides of the vertical-grain- direction lamella 120a, 120b. There may be several such pairs in the longitudinal direction of the laminated log 100, and they may be specifically arranged to improve the buckling capacity of the laminated log structure 200, for example so that the buckling capacity exceeds a threshold.
In the longitudinal direction, the load-bearing screws 210 may be arrayed either singly or arranged in a group 320 of several load-bearing screws. Also, some or all of the load-bearing screws 210 in the group 320 may have a pair arranged on the opposite side of the vertical-grain- direction lamella 120a, 120b, for example substantially along line 310. This may substantially improve the buckling capacity of the laminated log structure 200 even further. For example, 1-5 load-bearing screws 210 may be arranged in the array along the longitudinal direction of the laminated log 100, whereby the group 320 comprising several screws may include for example 2-3 or 2-5 screws 210. The load-bearing screws 210 belonging to the same group 320 may be substantially evenly spaced. Within the group 320, the distance between the load-bearing screws 210 is smaller than between the successive groups in the longitudinal direction of the laminated log 100. Their spacing may be for example 5-10 centimetres, such that the full length of the group 320 may be for example 5-40 centimetres when there are several screws 210 in the group 320.
A distance 330 between the successive arrays may be, in the longitudinal direction of the laminated log 100, for example 60-300 centimetres or 60-90 centimetres, wherein, in the case of the group 320, its position is determined based on the centre point. A distance 340 between the successive clamping screws 220 may be longer than the distance between the arrays 340, because for the clamping screws 210 it is sufficient that at least one clamping screw 210 is spaced no further than a threshold distance from each array of the load-bearing screws 210, so that the clamping screw 220 can clamp the superposed laminated logs 100 together also at the load-bearing screws 210. This threshold distance may be for example 50-100 centimetres, but in some cases it may be up to 150 centimetres. The threshold distance is measured in the longitudinal direction of the laminated log 100, and in the case of the groups 320, it is measured relative to the outermost load-bearing screw 210, i.e. the one closest to the clamping screw 220. If the laminated log structure 200 comprises one or more groups 320, all or some of the groups 320 may include a clamping screw 220, also within the group, i.e. in the longitudinal direction of the laminated log 100 at the first or the last load-bearing screw 210 or between the first and the last load bearing screw 210 of the group 320.
A clamping screw 220 may also be arranged on the cross-line 310 of the load-bearing screws 210, or at the above-mentioned threshold distance from this line 310. This ensures that the superposed laminated logs 100 are abutted also at the load-bearing screws 210, but specifically, installation in line 310 also makes it possible that the holes may be made for both of the clamping screw 220 and the load-bearing screws 210 by one drilling operation using one drill unit with multiple bits. However, the clamping screws 220 may also be spaced from the line 310.
Fig. 3b illustrates an example of the laminated log structure 200 in a cross-sectional view depicted in a plane along the longitudinal direction and the vertical direction of the laminated logs 100. It is possible to position the load-bearing screws 210 and/or the clamping screws 220 in the vertical direction of the laminated log structure 200 in line 350a, 350b, 360a, 360b or lines. Specifically, as to the load-bearing screws 210, this allows one or more load- bearing lines 350b, 360b to be formed. The verticallines 350a, 350b, 360a, 360b are indicated in the fig- ure by dashed lines, which are not drawn at the screws 210, 220 for clarity purposes.
As shown in the figure, the vertical line, herein a first vertical line 350a, 350b, may be formed so that, along the first vertical line 350a, 350b, each laminated log 100 is only provided with one screw 210, 220. Superposed laminated logs 100b, 100c may this way be connected into pairs by one screw 210, 220, so that each of the laminated logs 100b, 100c is connected by the screw 210, 220 along the first vertical line 350a, 350b in one direction only, i.e. either downwardly or upwardly. The pair may be arranged on top of one or more pairs of laminated logs 100d, 100e, which are likewise connected into pairs by the screw 210, 220 along the first vertical line 350a, 350b. However, the upper pair 100b, 100c is not connected to the lower pair 100d, 100e along the first vertical line 350a, 350b; instead, the superposed pairs are connected to each other by screws 210, 220 located on a second vertical line 360a, 360b that is offset from the first vertical line 350a, 350b. The second vertical line 360a, 360 may be offset from the first vertical line 350a, 350b at least in the longitudinal direction of the laminated log 100, which may also improve the buckling capacity of the laminated log structure 200. Also the laminated logs 100 on the second vertical line 360a, 360b may be connected into pairs so that, along the second vertical line 360a, 360b, each laminated log 100 is only provided with one screw 210, 220. The fastening arrangement illustrated in Fig. 3b may also be described by the superposed laminated logs 100 in the laminated log structure 200 being connected to each other by pairs along two separate vertical lines, i.e. the first vertical line 350a, 350b and the second vertical line 360a, 360b, such that the screws 210, 220 are alternately disposed along these vertical lines in the vertical direction of the laminated log structure 200. In principle, it is also possible to arrange the screws 210, 220 alternately in more than two vertical lines. In one vertical line, the screws 210, 220 are always the same type, i.e. load-bearing screws 210 or clamping screws 220.
The distance between the first vertical line 350a, 350b and the second vertical line 360a, 360b may be, for example, less than 60-150 centimetres. It may be at least for example 7 times the diameter of one load-bearing screw 210, which may be for example about 8 millimetres plus/minus 0-2 millimetres. The first vertical line 350a, 350b and/or the second vertical line 360a, 360b may extend substantially along the whole height of the laminated log structure 200. The second vertical line 360a, 360b may be arranged substantially along a longitudinal line of the laminated log 100 with the first vertical line 350a, 350b.
In Fig. 3b it is also shown that if holes 130, such as pre-drilled holes, are provided in the laminated logs 100, the holes 130 may be arranged in different positions in the superposed laminated logs 100, for example at the vertical lines such as the first vertical line 350a, 350b and/or the second vertical line 360a, 360b.
Generally, the clamping screws 220 may be installed in one laminated log 100 before the load-bearing screws 210 to ensure that there will be no clearance at the load-bearing screws 210 either. This may be done for example by installing all the clamping screws 220 of one laminated log 100 before any of the load-bearing screws 210, or at least by installing each array of the load-bearing screws 210 for the laminated log 100 only after the clamping screw 220 has been installed in the laminated log 100 no further than the threshold distance from the position configured for the array.
The invention is not limited exclusively to the above-described examples of its embodiments; instead, many modifications are possible within the scope of the inventive idea defined by the claims.

Claims

A laminated log structure (200) comprising a number of horizontal superposed laminated logs (100), wherein the laminated logs (100) include one or more vertical-grain-direction lamellas (120a, 120b), in which the wood grain runs substantially vertically when the laminated log lies in a horizontal plane, for limiting the settling of the laminated log structure (200), and
at least one horizontal-grain-direction lamella (110a, 110b), in which the wood grain runs substantially horizontally when the laminated log lies in a horizontal plane, on both sides of the one or more vertical-grain-direction lamellas (120a, 120b),

characterized in that the laminated logs (100) are fastened to each other by first screws (210) which, together with the vertical-grain-direction lamellas (120a, 120b), are arranged to bear the load of the laminated log structure (200), wherein said first screws (210) are arranged to fasten to one another said at least one horizontal-grain-direction lamella (110a, 110b) of the superposed laminated logs (100) on both sides of the one or more vertical-grain-direction lamellas (120a, 120b).
The laminated log structure according to claim 1, wherein one or more tongue-and-groove joint elements (140, 142) are provided in said horizontal-grain-direction lamellas (110a, 110b), and said first screws (210) are arranged on or adjacent to the inner edge of the tongue-and-groove joint element (140, 142).
The laminated log structure (200) according to claim 1 or 2, wherein said first screws (210) are full-thread screws.
The laminated log structure (200) according to any of claims 1-3, wherein said first screws (210) on opposite sides of said one or more vertical-grain-direction lamellas (120a, 120b) are arranged by pairs on a same line (310) substantially in the cross direction of the laminated log (100).
The laminated log structure (200) according to claim 4, wherein said vertical-grain-direction lamellas (120a, 120b) of the superposed laminated logs (100) are clamped together by second screws (220) which are arranged on said line (310), or the distance of which from the closest one of said lines (310) in the longitudinal direction of the laminated log (100) is no more than 50 centimetres.
The laminated log structure (200) according to any of claims 1-5, wherein said first screws (210) are arranged, in the longitudinal direction of the laminated logs (100), at a spacing of 60-300 centimetres.
The laminated log structure (200) according to any of claims 1-6, wherein said first screws (210) are arranged, in the longitudinal direction of the laminated logs (100), in one or more groups (320) of 2-6 screws.
The laminated log structure (200) according to any of claims 1-4, wherein said one or more vertical-grain-direction lamellas (120a, 120b) of the superposed laminated logs (100) are clamped together by the second screws (220).
The laminated log structure (200) according to claim 5 or 8, wherein said second screws are partial-thread screws (220).
The laminated log structure (200) according to any of claims 5, 8 or 9, wherein said second screws (220) are arranged, in the longitudinal direction of the laminated logs (100), at a spacing of 60-300 centimetres.
The laminated log structure (200) according to any of claims 1-10, wherein the laminated logs (100) are formed, in the cross direction, from three or more lamellas, with the horizontal-grain-direction lamellas (110a, 110b) on the sides and the vertical-grain-direction lamella (120a, 120b) in the middle.
The laminated log structure (200) according to any of claims 1-11, wherein the laminated logs are formed, in the vertical direction, from two or more lamellas (110a, 110b, 120a, 120b).
The laminated log structure (200) according to any of claims 1-12, wherein pre-drilled holes (130) are provided in the laminated logs (100) for the screws (210, 220).
The laminated log structure (200) according to any of claims 1-13, wherein said first screws (210) are cone-headed.
A method for forming a laminated log structure (200), in which method horizontal laminated logs (100) are arranged one on top of the other, wherein the laminated logs (100) include
one or more vertical-grain-direction lamellas (120a, 120b) for limiting the settling of the laminated log structure (200), and

at least one horizontal-grain-direction lamella (110a, 110b) on both sides of the one or more vertical-grain-direction lamellas (120a, 120b),

characterized in that the laminated logs (100) are fastened to each other by first screws (210) which, together with the vertical-grain-direction lamellas (120a, 120b), are arranged to bear the load of the laminated log structure (200), wherein said first screws (210) are arranged to fasten to one another said at least one horizontal-grain-direction lamella (110a, 110b) of the superposed laminated logs (100) on both sides of the one or more vertical-grain-direction lamellas (120a, 120b).