Fire-resistant construction of structural timber

Abstract

To provide a fire-resistant structure for structural timber that can dramatically increase the effect of reducing heat reaching the support layer. [Solution] The structural lumber comprises a support layer (52) and a covering layer (53) disposed on its outer side. The covering layer is composed of multiple layers of non-combustible LVB (10) clad with non-combustible decorative veneers attached to the outer side of the support layer. The non-combustible LVB comprises an infrared-reflecting layer (41) such as aluminum foil on the front and back of a siding board (11) that is a semi-combustible LVB. The siding board comprises front and back veneers (21) that form the front and back of the board, and a core veneer layer (31) laminated between the front and back veneers. The veneer fiber direction of the front and back veneers is approximately parallel to the length direction of the siding board. The core veneer layer is a layer in which multiple core veneers (32) are stacked in the thickness direction, and the veneer fiber direction of all these core veneers is approximately perpendicular to the length direction of the siding board. Reverse cracks and fissures are exposed on the grain surfaces of all the front and back veneers, and an aqueous solution of a non-combustible chemical agent penetrates through these.

Description

[Technical Field]

[0001] This invention relates to fire-resistant construction of structural timber. [Background technology]

[0002] The inventor has completed the invention of semi-non-combustible or flame-retardant wood, and has proposed it in Patent Documents 1 and 2. The invention of Patent Document 1 aims to provide semi-fireproof or fire-retardant wood that can exhibit uniform fire resistance and a manufacturing method thereof. It aims to provide semi-fireproof or fire-retardant wood made solely from sapwood of conifers such as cedar or diffuse-hole hardwoods. Injection holes of a predetermined depth are formed at appropriate intervals in the wood, and the pieces of wood are laminated together with adhesive, with the overlapping surfaces facing inward. By injecting a water-soluble or other fire-retardant agent under reduced pressure or pressure into the laminated wood processed in this way, semi-fireproof or fire-retardant wood with uniform and stable fire resistance throughout can be obtained.

[0003] The invention described in Patent Document 2 aims to improve the reliability of fire resistance for wood containing fire-retardant treatment agents, such as semi-fire-retardant wood, while also improving the ease of raw material procurement and mass production. The siding board described in Patent Document 2 comprises front and back veneers that form the front and back sides of the board, and a core veneer layer laminated between the front and back veneers. The veneer fiber direction of the front and back veneers is approximately parallel to the length direction of the siding board. The core veneer layer is a layer of multiple rotary veneers stacked in the thickness direction, and the veneer fiber direction of all these core veneers is approximately perpendicular to the length direction of the siding board. The front and back veneers are 1.5 mm to 4.0 mm thick, and the core veneer layer is thicker than the total thickness of the front and back veneers. In this case, the sapwood, white band, mature heartwood, and unaged heartwood can be used without distinction. The tangential surfaces of all front and back veneers have exposed cracks and fissures, through which an aqueous solution of fire-retardant agent penetrates.

[0004] In Patent Document 2, a quasi-fireproof siding board can be obtained without selecting parts of the tree by using a new layered veneer structure that includes a core veneer layer containing a fireproofing agent that has migrated through back cracks in the veneer that have developed along the vessels and tracheids, and front and back veneers that are located above and below the core veneer layer and contain a fireproofing agent that has infiltrated from the tangential grain of both the top and bottom surfaces.This veneer proposes a structure that allows the fireproofing agent to be distributed over the entire veneer, and it is currently difficult to achieve even greater fireproofing.

[0005] On the other hand, for structural timber such as beams and pillars, it has been proposed to form a fire-retardant layer using materials that are fire-retardant (such as fire-retardant-injected wood, which is wood that has been treated by injecting a fire-retardant agent into it) or materials that can absorb heat (inorganic materials with high heat capacity such as mortar, stone, glass, fiber-reinforced cement, gypsum, and various metal materials; calcium silicate boards, rock wool, and glass wool, which have high insulating properties; and woods such as Selangan Batu, Jarrah, and Bongosi, which have high thermal inertia).However, because the insulating effect is proportional to the thickness of the fire-retardant layer, it has been difficult to make the product thinner. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2020-89978 [Patent Document 2] International Publication No. 2022 / 130727 Brochure Summary of the Invention [Problem to be solved by the invention]

[0007] The objective of this invention is to provide a fire-resistant structure for structural timber that can dramatically reduce the amount of heat reaching the supporting layer. [Means for solving the problem]

[0008] This invention solves the problem by dramatically improving the fire resistance of semi-fireproof LVB by placing an infrared-reflecting layer such as aluminum foil on at least one of the front and back sides of the semi-fireproof LVB containing the fire-retardant treatment agent developed by the inventor, and by providing a fire-resistant structure for structural wood in which this is placed on the outside of multiple surrounding support layers. [Effects of the Invention]

[0009] In the structural lumber of this invention, the reflective effect of the infrared-reflecting layer in the coating layer accumulates, allowing for an exponential reduction in the heat reaching the lumber. As a result, in addition to the fire resistance provided by the chemicals uniformly distributed in the core veneer layer, the infrared-reflecting layer dramatically reduces the heat reaching the support layer. This means that the same fire resistance can be achieved even if the coating layer that protects the support layer from heat is thinner than in conventional products. [Brief explanation of the drawings]

[0010] [Figure 1] (A) is an explanatory diagram of the cross-sectional structure of structural lumber relating to an embodiment of the present invention, and (B) is a perspective view of non-combustible LVB with non-combustible decorative veneer used in the same structure. [Figure 2] Plan view of each layer of the non-flammable LVB. [Figure 3] (A) An explanatory diagram of the cross-sectional structure of a log for obtaining lumber for non-combustible LVB semi-combustible lumber according to an embodiment of the present invention, (B) An explanatory diagram of the cross-sectional structure of a log for obtaining lumber for semi-combustible lumber according to another embodiment. [Figure 4] (A) An explanatory diagram of the cross-sectional structure of a non-combustible LVB used in structural lumber in an embodiment of the present invention, (B) An explanatory diagram of the cross-sectional structure of a non-combustible LVB used in structural lumber in another embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

[0012] In this embodiment, structural timber 51 for pillars, beams, etc. comprises a support layer 52 and a plurality of covering layers 53 (three layers in Figure 1(A)) arranged around the outside of the support layer 52 without any gaps and fixed with adhesive or the like. The covering layer 53 in this embodiment uses non-combustible LVB 10 with non-combustible decorative veneer as shown in Figure 1(B), and the non-combustible LVB 10 with non-combustible decorative veneer on the wood support layer 52 is composed of an infrared reflective layer 41 arranged on the front and back surfaces 12 of the siding board 11, which is a quasi-non-combustible LVB. As shown in Figures 1 and 2, the siding board 11 has front and back surfaces 12, front and rear end surfaces 13, and left and right side surfaces 14. The front and back surfaces 12 of the siding board 11 are composed of front and back veneers 21. A core veneer layer 31 is disposed between the front and back veneers 21, and a plurality of core veneers 32 are laminated. These front and back veneers 21 and core veneer 32 are bonded together by a water-resistant adhesive or the like in accordance with a standard method. Since this non-combustible LVB 10 is flat, it is cut to an appropriate length, and the cut surfaces or the cut surfaces and the flat surface are brought into surface contact with each other without any gaps to form the covering layer 53.

[0013] (About front and back veneer 21) The grain direction of front and back veneer 21 (arrow S in Figure 2) is approximately parallel to the length direction of siding board 11, and like a normal LVL siding board, its butt faces (end faces approximately perpendicular to the grain direction of the wood) are arranged at front and rear end faces 13 of siding board 11. The thickness of front and back veneer 21 is 1.5 mm to 4.0 mm.

[0014] (21 fire retardant veneers) In the front and back veneers 21, an aqueous solution of the fire retardant agent is present, which has soaked in through cracks and crevices on the back surface of the plain grain surface exposed on the front and back surfaces. Specifically, a solution of non-combustible, semi-non-combustible, or fire-retardant treatment agent is injected into the siding board 11, which has been finished to a predetermined size, using a reduced pressure injection can. In this case, the front and back veneers 21 are exposed on four surfaces, namely the front and back surface 12 of the siding board 11, as well as the front and back end surfaces 13 and the left and right side surfaces 14. Therefore, although the aqueous solution of chemicals is injected from these surfaces, the distance the aqueous solution of chemicals travels from the four surfaces, namely the front and back end surfaces (i.e., butt surfaces) 13 and the left and right side surfaces (i.e., edge surfaces) 14, is shorter than the total length of the siding board 11. However, because one surface of the front and back surface (i.e., cross grain surface) 12 of the siding board 11 is exposed entirely, the aqueous solution of chemicals from the front and back surface 12 seeps into the interior from that entire surface, passing through cracks and crevices in the wood.

[0015] (Regarding core veneer layer 31) All of the core veneers 32 constituting the core veneer layer 31 have a veneer fiber direction (arrow T shown in FIG. 2) that is substantially perpendicular to the length direction of the siding board 11. Unlike ordinary LVL siding, the butt end faces (the end faces that are approximately perpendicular to the direction of the wood grain) are exposed on the left and right side surfaces 14 of the siding 11. The thickness of the core veneer layer 31 is equal to or greater than the combined thickness of the two front and back veneers 21.

[0016] (Retardant agent for core veneer layer 31) All core veneers 32 have a fire-retardant treatment agent present throughout them, which has migrated via the back cracks of the veneer that have developed along the tracheids or vessels. Specifically, a solution of non-combustible, semi-non-combustible, or fire-retardant treatment agent is injected into the siding board 11, which has been finished to a predetermined size, using a reduced pressure injection can. At this time, the core veneer 32 is exposed on four surfaces: the front and rear end faces 13 and the left and right side faces 14. Therefore, although the aqueous solution of chemicals is injected from these surfaces, the movement distance of the aqueous solution of chemicals from the front and rear end faces 13 is shorter than the movement distance from the left and right side faces 14, because the fiber direction of the veneer (arrow T) is aligned with the width direction of the siding 11. However, the aqueous solution of non-combustible, semi-non-combustible, or fire-retardant treatment chemicals injected from the left and right side faces 14 can move a certain distance along the fiber direction of the veneer (arrow T). Specifically, preliminary tests by the inventor have confirmed that if the core veneer 32 is a veneer made from cedar sapwood, the chemical agent will penetrate for a length of 150 mm or more in the direction of the veneer fibers (arrow T), if it is a veneer made from cedar sapwood and core wood, the chemical agent will penetrate for a length of 150 mm to 200 mm in the direction of the veneer fibers (arrow T), and if it is a veneer made from poplar sapwood and core wood, the chemical agent will penetrate for a length of 80 mm to 200 mm in the direction of the veneer fibers (arrow T). In this way, by limiting the width of the siding 11 to within twice the distance that the aqueous solution of chemicals can move in the veneer fiber direction (arrow T) in the core veneer 32, the aqueous solution of chemicals injected from the left and right end faces of the core veneer 32 exposed on the left and right side surfaces 14 of the siding 11 can reach the entire width. Therefore, the aqueous solution of the drug can be uniformly distributed over the entire core veneer 32 with certainty.

[0017] (Wood 11 Production) Generally, wood is roughly divided into sapwood and heartwood, with sapwood referring to the whitish outer periphery of a log's cross section and heartwood referring to the reddish central portion of a log's cross section. More specifically, heartwood can be divided into two regions: the immature and mature central regions. A white band may also be present at the boundary between the sapwood and heartwood. Therefore, as shown in Figure 3, wood can be divided into four regions from the outside: sapwood A, white band B, mature heartwood C, and immature heartwood D. In this invention, the term "heartwood" refers to the region including white band B, mature heartwood C, and immature heartwood D.

[0018] In the present invention, as shown in FIG. 3(A), the chemical penetrates not only into the sapwood A where fluid movement is good, but also into the heartwood where fluid movement is relatively poor, by 80 mm to 200 mm or more, as described above. Therefore, by selecting and using the optimal tree species and areas to be used depending on the desired width of the veneers 21, 32 of the siding board 11, it is possible to manufacture a siding board 11 in which the non-flammable, semi-non-flammable, and flame-retardant treatment agents are well distributed throughout the entire siding board 11. Of course, as shown in Figure 3(B), it is also possible to use only the sapwood part A, where the liquid moves well in the direction of the fiber inside the wood, or to use both parts without making any distinction.

[0019] For example, if a veneer made of cedar sapwood is used for the core veneer 32, if a veneer made of cedar sapwood and a veneer made of cedar heartwood are used together without distinction, or if a veneer made of poplar sapwood and a veneer made of poplar heartwood are used together without distinction, then regardless of the tree species or the distinction between sapwood and heartwood, for rotary veneers, it is appropriate that the overall thickness of the siding board 11 be 12mm to 30mm, the width be 100mm to 310mm, and the length be 2000mm to 4500mm.

[0020] (Drug injection) Chemical impregnation is the process of creating a siding board material of a specified size by laminating veneers with water-soluble adhesives, etc., as described above, and then injecting a fire-retardant chemical into the siding board material. Specifically, a vacuum / pressure injection tank is used to inject an aqueous solution of fire-retardant, semi-fire-retardant, or fire-retardant chemicals into the siding board material, completing the semi-fire-retardant wood. The amount of chemicals injected can be set depending on the dimensions of the front and back veneers 21 and the core veneer layer 31, the type of tree, and the region where it grew. In the case of Japanese cedar, the guideline is about 150 kg / m for a wood 11 with a thickness of 18 mm. 3 It is appropriate to do so.

[0021] Since the state of impregnation of the chemical solution varies depending on the type of wood and its growth condition, it is preferable to confirm the decompression conditions and time, pressurization conditions and time, and number of repetitions in preliminary experiments using a water-soluble colorant. In addition, it is preferable that the injection amount for process control is controlled by measuring the weight before and after injection and taking the difference as the average injection amount for the lot.

[0022] (Post-injection process) Curing: It is preferable to carry out curing including drying in order to level the inside of the wood of the injected chemicals, and the curing period is determined in a preliminary experiment. Drying: The moisture content is controlled to meet the product quality determined through agreements with the seller. Artificial drying is preferable to improve quality.

[0023] Finishing process: To meet the specified requirements for the product, the board width is finished with a rip saw, the length with a cross-cut saw, and the surface is finished with a sander or molder. Inspection: Carry out inspections necessary to ensure product quality. For example, thickness and width are measured with a vernier caliper, length with a steel tape measure, and appearance and surface texture are checked visually and by touch. Packaging: Semi-non-combustible wood products are bundled together and wrapped on six sides to block moisture from the outside air, and are wrapped in plastic sheets and secured with tape to prevent damage to the cargo.

[0024] The siding 11 used in the non-combustible LVB 10 of this embodiment is a quasi-non-combustible wood, exhibiting uniform and excellent fire resistance throughout the material. When wood material with insufficient chemical impregnation is heated, it reaches a high temperature of approximately 260°C or higher, generating flammable gases from the wood structure in the insufficient areas, which then ignite. This results in a significant loss of fire resistance. However, the siding 11 used in this invention is impregnated almost entirely with a sufficient amount of fire-resistant chemical, thereby suppressing the generation of flammable gases from the wood structure and providing stable fire resistance. While chemicals have limitations in improving fire resistance, this invention overcomes these limitations by providing an infrared-reflective layer 41 on at least one of the front and back sides of the siding 11, thereby achieving a non-combustible LVB with fire resistance equivalent to certification for structural methods, special structural methods, etc., under the Building Standards Act.

[0025] As shown in Fig. 4(A), the infrared reflective layer 41 comprises an aluminum foil 42 containing aluminum or an alloy thereof, and supporting paper 43. Note that Fig. 4 is for explaining the laminated structure, and does not accurately depict the thickness. The infrared reflective layer 41, particularly the aluminum foil 42, reflects infrared rays that would otherwise penetrate into the semi-non-combustible LVB, thereby enhancing the non-combustibility of the siding board 11. Even with a thickness of 20 μm, the aluminum foil 42 can achieve a high infrared reflection effect of 95 to 98%, and by reflecting infrared rays that would otherwise penetrate into the interior of the siding board 11, the non-combustibility of the siding board 11 is dramatically enhanced, resulting in the production of a non-combustible LVB 10.

[0026] As shown in Figure 4(B), it is also possible to use multiple siding boards 11. The infrared reflective layer 41 is disposed on at least one of the front and back sides of the siding board 11, and can also be disposed between multiple siding boards 11.

[0027] Regardless of which of the siding panels 11 in Figure 4 is used as the covering layer 53, by arranging multiple layers on top of each other, there are multiple aluminum foils 42, and the reflective effect accumulates, making it possible to exponentially reduce the heat reaching the wood.

[0028] As a result, in addition to the fire resistance provided by the agent distributed almost uniformly in the core veneer layer 31, the infrared reflective layer 41 provided with the aluminum foil 42 can dramatically increase the effect of reducing the heat reaching the support layer 52. This means that the same fire resistance can be achieved even if the covering layer 53 that protects the support layer 52 from heat is made thinner than in conventional products.

[0029] Traditionally, inorganic materials such as mortar, gypsum board, and diamite have been used to provide insulation, and since the insulating effect is proportional to the thickness of the insulating material, it has been difficult to make the product thinner. In the embodiment of the present invention, sufficient heat resistance can be obtained with a relatively thin coating layer 53 as described above, the use of inorganic materials is eliminated, and the production process for structural fire-resistant wood components can be simplified, thereby reducing costs. Furthermore, standards for structural fire-resistant wood are set at fire resistance times of 30, 60, 90, 120, 180, and 240 minutes, with the longer the fire resistance time, the more suitable it is for use in high-rise buildings. The fire resistance time can be extended by adjusting the laminated structure and number of turns of the non-combustible LVB10 used in the covering layer 53, which simplifies the production process and reduces costs.

[0030] As such, conventional fire-resistant structural wood products use insulating materials such as mortar, gypsum board, and inorganic materials like dilite to block heat, so the insulating effect is proportional to the thickness of the insulating material.However, in the case of an infrared reflective layer 41 using aluminum foil 42 or the like, the heat reflective effect accumulates and exponentially reduces the amount of heat that reaches the wood.Therefore, by using non-combustible LVB 10 with multiple infrared reflective layers 41 as the covering layer 53 of structural fire-resistant wood, the effect increases exponentially.

[0031] As mentioned above, it is effective to layer non-combustible LVB with aluminum foil multiple times on top of semi-combustible LVB as a fire-resistant covering material, and the necessity and mechanism behind this are explained below. 1. The fire-resistant structure of structural timber of this invention is used as fire-resistant covering for the column and beam structures of large wooden buildings. 2. It is generally said that when wood is exposed to temperatures above 260°C, it releases gaseous components and ignites. 3. Aluminum foil has a heat-blocking effect, reflecting more than 90% of radiant heat. 4. When a fire breaks out and the temperature exceeds 260°C, the gases released from the wood will ignite, but if there is aluminum foil between the fire source and the wood, more than 90% of the heat is blocked, making the wood fireproof. 5. The melting point of aluminum is said to be 660°C. If the temperature at a fire site rises above this level, the aluminum will melt, exposing the surface of the fire-resistant wood to the heat source. 6. In chemically injected fireproof wood, the dehydrating action of the flame retardant forms a dehydrated carbonized foam layer, which blocks the supply of oxygen to the interior of the wood, suppressing heat penetration and inhibiting combustion. The insulating effect of this carbonized layer prevents heat from penetrating into the interior. 7. If long-term fire resistance is required, the number of layers of non-combustible aluminum foil-coated LVB can be increased to repeat the effect. 8. The combined effect of the heat-shielding aluminum foil sheet and the repeated insulation provided by the carbonized layer of the semi-fireproof wood prevents heat from penetrating into the structural wood in the event of a fire. [Explanation of symbols]

[0032] 10…Nonflammable LVB 11...Washboard 12...Front and back 13...Left and right sides 14…Front and rear end faces 21...Single-ply front and back 31...Core veneer layer 32...Solid core 41...Infrared reflective layer 42...Aluminum foil 43...Paper 51…Structural wood 52…Support layer 53…Covering layer A…Sapwood part B: White line C…Heartwood ripening section D... Heartwood unripened part S...Veneer grain direction of front and back veneers T: Core veneer fiber direction

Claims

1. A structural timber structure comprising: a structural timber; and a covering layer disposed on the exterior of the structural timber; The covering layer is formed by attaching multiple layers of non-combustible LVB with non-combustible decorative veneer to the outside of the structural timber, The non-combustible LVB comprises a semi-non-combustible LVB and an infrared reflective layer, The quasi-noncombustible LVB is a siding board in which a plurality of veneers are laminated one above the other with adhesive, and the veneers are laminated without distinguishing between sapwood and heartwood, The veneer is a rotary veneer of a low specific gravity wood species, A front and back veneer constituting the front and back of the semi-non-combustible LVB; A core veneer layer is laminated between the front and back veneers, The fiber direction of the front and back veneers is approximately parallel to the length direction of the siding board, The core veneer layer is a layer in which a plurality of core veneers are stacked in the thickness direction, The fiber direction of all of the core veneers is approximately perpendicular to the length direction of the semi-noncombustible LVB. The thickness of the core veneer layer is equal to or greater than the total thickness of the front and back veneers; All of the above-mentioned front and back veneers are coated with a fire-retardant agent that has penetrated from the grain side through the cracks on the back of the veneer or the tiny cracks that occurred during veneer processing with a water solution. All of the core veneers are entirely coated with fire retardant treatment chemicals that have migrated along the fiber direction of the veneer through cracks formed along vessels or tracheids. A fire-resistant structure for structural wood, characterized in that the infrared reflective layer comprises a metal foil containing aluminum or its alloy and is arranged on at least one of the front and back sides of the semi-fireproof LVB, and the infrared reflective layer is configured to accumulate heat reflection effect and exponentially reduce the amount of heat reaching the structural wood.

2. A structural timber structure comprising: a structural timber; and a covering layer disposed on the exterior of the structural timber; The covering layer is made of a non-combustible LVB laminated with a non-combustible decorative veneer attached to the outside of the structural timber, and The quasi-noncombustible LVB is a siding board in which a plurality of veneers are laminated one above the other with adhesive, and the veneers are laminated without distinguishing between sapwood and heartwood, The veneer is a rotary veneer of a low specific gravity wood species, A front and back veneer that constitutes the front and back of the siding board; A core veneer layer is laminated between the front and back veneers, The fiber direction of the front and back veneers is approximately parallel to the length direction of the semi-noncombustible LVB, The core veneer layer is a layer in which a plurality of core veneers are stacked in the thickness direction, The fiber direction of all of the core veneers is approximately perpendicular to the length direction of the semi-noncombustible LVB. The thickness of the core veneer layer is equal to or greater than the total thickness of the front and back veneers; All of the above-mentioned front and back veneers are coated with a fire-retardant agent that has penetrated from the grain side through the cracks on the back of the veneer or the tiny cracks that occurred during veneer processing with a water solution. All of the core veneers are entirely coated with fire retardant treatment chemicals that have migrated along the fiber direction of the veneer through cracks formed along vessels or tracheids. A fire-resistant structure for structural wood, characterized in that the infrared reflective layer comprises a metal foil containing aluminum or its alloy and is arranged on at least one of the front and back sides of the semi-fireproof LVB, and the infrared reflective layer is configured to accumulate heat reflection effect and exponentially reduce the amount of heat reaching the structural wood.

3. The rotary veneer of the low specific gravity tree species is a veneer of cedar or poplar, A fire-resistant structure of structural wood as described in claim 1 or 2, characterized in that the non-combustible LVB has non-combustible performance equivalent to certification of structural methods, etc. based on the Building Standards Act or certification of special structural methods, etc.

4. The thickness of the semi-non-combustible LVB is 12 mm to 30 mm, The thickness of the front and back veneers is 1.5 mm to 4.0 mm, The rotary veneer of the low specific gravity tree species is a veneer of cedar or poplar, 3. A fire-resistant structure for structural timber according to claim 1, wherein the adhesive is a thermosetting phenolic adhesive.

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