Fire-resistant structural material and method for producing the same

Abstract

To provide a fire-resistant structural material that has adequate fire resistance.SOLUTION: A fire-resistant structural material including: a load-supporting part 11 formed of wood or steel; a fire-resistant covering layer 12 composed of solid wood covering the load-supporting part 11; and a delaminating covering layer 13 composed of solid wood covering the fire-resistant covering layer 12, the delaminating covering layer burning, carbonizing, and delaminating when exposed to flames, the delaminating covering layer 13 and the fire-resistant covering layer 12 being joined by dry jointing. In a combustion test of 90 minutes or 120 minutes under standard heating in accordance with ISO834-1, it is preferable that, at the end of heating, the ratio of the mass of the delaminated delaminating covering layer to the total mass of the delaminating covering layer 13 is 80% or more.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a fire-resistant structural material and a method for manufacturing the same. [Background technology]

[0002] Various techniques have been proposed to provide fire-resistant components by providing a fire margin on the surface of wood or a composite material of wood and other materials. For example, Patent Document 1 proposes a structural material that includes a load-bearing layer and a fire margin layer that is arranged outside the load-bearing layer and is made of wood with a lower thermal inertia than the load-bearing layer. Patent Document 2 also proposes a structural material that includes a load-bearing layer, a fire-stop layer that is arranged outside the load-bearing layer and has a heat insulating material, and a fire margin layer that is arranged outside the fire-stop layer and is made of wood with a predetermined thickness. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2005-36457 [Patent Document 2] Japanese Patent Application Laid-Open No. 2005-48585 Summary of the Invention [Problem to be solved by the invention]

[0004] In wooden structural materials such as those described in Patent Documents 1 and 2, red heat may remain in the non-burning layer or the burned-out layer when allowed to cool after heating, and combustion may continue. When wooden materials are heated by a fire or the like, the surface layer burns and a carbonized layer is formed. In wooden materials, cracks may occur in the carbonized layer or parts of the carbonized layer may be missing, forming irregularities on the surface of the carbonized layer. In such cases, red heat may remain inside the carbonized layer, such as in the cracks that have occurred in the carbonized layer. As such, the wooden structural materials described in Patent Documents 1 and 2 may remain red heat and continue burning even after heating has been completed, and their fire resistance was insufficient.

[0005] An object of the present invention is to provide a fire-resistant structural material having sufficient fire resistance. [Means for solving the problem]

[0006] The present invention provides a fire-resistant structural material comprising a load-bearing section made of wood or steel, a fire-resistant coating layer made of pure wood that covers the load-bearing section, and a sheddable coating layer made of pure wood that covers the fire-resistant coating layer and burns, carbonizes, and sheds when exposed to flames, and the sheddable coating layer and the fire-resistant coating layer are dry-bonded together. [Effects of the Invention]

[0007] According to the present invention, a fire-resistant structural material having sufficient fire resistance can be provided. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a cross-sectional view schematically showing a fire-resistant structural material according to a first preferred embodiment of the present invention. [Figure 2] FIG. 2 is a partially cutaway side view schematically showing the fire-resistant structural material shown in FIG. [Figure 3] FIG. 3 is a cross-sectional view schematically showing a fire-resistant structural material according to a second preferred embodiment of the present invention. [Figure 4] FIG. 4 is a cross-sectional view schematically showing the fire-resistant structural material of Example 1. As shown in FIG. [Figure 5] FIG. 5 is a diagram showing the measurement positions of temperature changes when a combustion test was conducted on the fire-resistant structural material of Example 1, and is a schematic side view of the fire-resistant coating layer. [Figure 6] 6(a) and (b) are diagrams showing the measurement positions of temperature changes when a combustion test was conducted on the fire-resistant structural material of Example 1, where FIG. 6(a) is a cross-sectional view taken along line VIa-VIa in FIG. 5, and FIG. 6(b) is a cross-sectional view taken along line VIb-VIb in FIG. 5. [Figure 7] 7(a) and (b) are graphs showing the results of measuring the temperature of the fire-resistant structural material of Example 1 when a combustion test was conducted on the fire-resistant structural material of Example 1. [Figure 8]FIG. 8 is a photograph showing the state of the fire-resistant structural material of Example 1 after the combustion test. [Figure 9] FIG. 9 is a cross-sectional view schematically showing the fire-resistant structural material of Example 2. As shown in FIG. [Figure 10] FIG. 10 is a diagram showing the measurement positions of temperature changes when a combustion test was conducted on the fire-resistant structural material of Example 2, and is a schematic side view of the fire-resistant coating layer. [Figure 11] FIG. 11 is a diagram showing the measurement positions of temperature changes when a combustion test was conducted on the fire-resistant structural material of Example 2, and is a schematic cross-sectional view of the fire-resistant coating layer and the load-bearing portion. [Figure 12] 12(a) to 12(c) are graphs showing the results of a combustion test conducted on the fire-resistant structural material of Example 2, measuring the temperature of the north side of the fire-resistant structural material (the part where cedar laminated wood was used as the detachable coating layer). [Figure 13] Figures 13(a) to (c) are graphs showing the results of a combustion test conducted on the fire-resistant structural material of Example 2, measuring the temperature of the southern part of the fire-resistant structural material (the part where larch laminated timber was used as the detachable coating layer). [Figure 14] Figures 14(a) and (b) are photographs showing the condition of the fire-resistant structural material of Example 2 after the combustion test. Figure 14(a) is a photograph of the northern part of the fire-resistant structural material (the part where cedar laminated timber is used as the detachable coating layer), and Figure 14(b) is a photograph of the southern part of the fire-resistant structural material (the part where larch laminated timber is used as the detachable coating layer). DETAILED DESCRIPTION OF THE INVENTION

[0009] The present invention will be described in detail below based on preferred embodiments thereof. A fire-resistant structural material 1, which is a first preferred embodiment of the fire-resistant structural material of the present invention, is shown in Figures 1 and 2. Figure 1 schematically shows a cross section perpendicular to the axial direction of the fire-resistant structural material 1. The fire-resistant structural material 1 of this embodiment is a structural square timber used as a beam or column in a building. As shown in Figure 1, the fire-resistant structural material 1 comprises a load-bearing portion 11 made of wood or steel, a fire-resistant coating layer 12, and a detachable coating layer 13.

[0010] The cross-sectional design of the load-bearing portion 11 is such that the load-bearing portion 11 alone is structurally safe against long-term loads (long-term loads) such as dead loads, live loads, and snow loads. Such cross-sectional designs are well known. The cross-sectional shape of the load-bearing portion 11 is rectangular, and the vertical and horizontal lengths of the load-bearing portion 11 in the cross-section of the fire-resistant structural material 1 can be changed as appropriate depending on the shape or size of the beams or columns.

[0011] The fire-resistant coating layer 12 covers the load-bearing portion 11. In this embodiment, the fire-resistant coating layer 12 covers four axial side surfaces of the load-bearing portion 11. If the fire-resistant structural material 1 is a beam, the fire-resistant coating layer 12 may cover three axial side surfaces of the load-bearing portion 11. The side of the fire-resistant structural material 1 on which the fire-resistant coating layer 12 is not formed may be covered by placing a floor or the like thereon to cover the upper side of the load-bearing portion 11.

[0012] The deciduous coating layer 13 covers the fire-resistant coating layer 12. The deciduous coating layer 13 and the fire-resistant coating layer 12 are dry-bonded together. Specifically, the deciduous coating layer 13 and the fire-resistant coating layer 12 are bonded together by a plurality of fixing members 14 that penetrate the deciduous coating layer 13 and are inserted into the fire-resistant coating layer 12. Various known fixing members 14 can be used as the fixing members 14. It is preferable that the tips of the fixing members 14 do not reach the load-bearing portion 11 to prevent the fixing members 14 from forming a thermal bridge. In this embodiment, a countersink 16 is formed in the deciduous coating layer 13, and the heads of the fixing members 14 do not protrude from the deciduous coating layer 13. Furthermore, a filler 17 is placed in the countersink 16 to close the countersink 16. Note that in Figures 1, 3, 4, and 9, the heads of the fixing members 14, the countersink 16, and the filler 17 are greatly exaggerated in size.

[0013] The shedding coating layer 13 is designed to burn, carbonize, and fall off when exposed to flames. The shedding of the shedding coating layer 13 allows the fire-resistant structural material 1 to exhibit sufficient fire resistance. As with the wooden structural materials of Patent Documents 1 and 2, the carbonized layer formed by the combustion of the shedding coating layer 13 may also leave red heat inside the carbonized layer, for example, in cracks that have developed in the carbonized layer. However, because the shedding coating layer 13 falls off, even if red heat remains inside the carbonized layer formed by the combustion of the shedding coating layer 13, the carbonized layer is removed from the fire-resistant structural material 1. This prevents red heat from remaining in the fire-resistant structural material 1, and prevents the fire-resistant structural material 1 from continuing to burn even after heating has been completed.

[0014] It is preferable that the removable coating layer 13 does not fall off for a certain period of time after the start of heating of the fire-resistant structural material 1, and falls off after the certain period of time has elapsed. By not allowing the removable coating layer 13 to fall off for a certain period of time after the start of heating of the fire-resistant structural material 1, the removable coating layer 13 covers the fire-resistant coating layer 12 for that certain period of time after the start of heating, and the fire-resistant coating layer 12 can be prevented from being directly exposed to flames. From the viewpoint of preventing the fire-resistant coating layer 12 from being directly exposed to flames, it is preferable that the removable coating layer 13 does not fall off until 66% of the heating time from the start to the end of heating of the fire-resistant structural material 1 has elapsed, more preferably until 75% of the heating time has elapsed, and even more preferably until 90% of the heating time has elapsed.

[0015] When the fire-resistant structural material 1 is subjected to a 90-minute or 120-minute combustion test using standard heating in accordance with ISO834-1, it is preferable that the ratio of the mass of the detachable coating layer 13 that has fallen off to the total mass of the detachable coating layer 13 is 80% or more at the end of heating.

[0016] When a 90-minute combustion test is performed, the time when the ratio of the mass of the detachable coating layer 13 to the total mass of the detachable coating layer 13 reaches 80% is preferably 70 minutes, more preferably 80 minutes, and even more preferably 90 minutes after the start of heating.

[0017] When a combustion test is carried out for 120 minutes, the time when the ratio of the mass of the detached detachable coating layer 13 to the total mass of the detachable coating layer 13 reaches 80% is preferably 90 minutes, more preferably 105 minutes, and even more preferably 120 minutes from the start of heating.

[0018] The thickness T1 of the deciduous coating layer 13 is preferably 70 mm or less, more preferably 60 mm or less, and even more preferably 40 mm or less, from the viewpoint of facilitating the deciduous coating layer 13 to be easily removed when red heat remains in the deciduous coating layer 13. The thickness T1 of the deciduous coating layer 13 is preferably 15 mm or more, more preferably 20 mm or more, and even more preferably 30 mm or more, from the viewpoint of preventing the fire-resistant coating layer 12 from being directly exposed to flames.

[0019] The ease with which the removable coating layer 13 falls off can also be adjusted by the pitch of the fixing members 14 in the axial direction Z (see FIG. 2). Specifically, narrowing the distance D between adjacent fixing members 14 in the axial direction Z makes the removable coating layer 13 less likely to fall off, while widening the distance D makes the removable coating layer 13 more likely to fall off. Note that in FIG. 2, the fixing members 14 and the countersunk holes into which the fixing members 14 are inserted are greatly exaggerated.

[0020] To facilitate the detachable coating layer 13 to fall off when it remains red-hot, the distance D is preferably 300 mm or more, more preferably 400 mm or more, and even more preferably 500 mm or more. To prevent the fire-resistant coating layer 12 from being directly exposed to flames, the distance D is preferably 1200 mm or less, more preferably 900 mm or less, and even more preferably 600 mm or less.

[0021] When the deciduous coating layer 13 on the surface of the fire-resistant structural material 1 is damaged, such as cracked, by a fire, for example, a small fire, it is possible to replace only the deciduous coating layer 13. It is also possible to replace the deciduous coating layer 13 depending on the fire resistance time desired for the fire-resistant structural material 1 and the thickness desired for the deciduous coating layer 13 for the fire-resistant structural material 1. Because it is possible to replace only the deciduous coating layer 13 of the fire-resistant structural material 1, the cost required for repairing the fire-resistant structural material 1 can be reduced.

[0022] Next, a second preferred embodiment of the fire-resistant structural material of the present invention will be described with reference to Fig. 3. Regarding the second embodiment, differences from the first embodiment will be described, and the description of the first embodiment will be applied appropriately to points not specifically described.

[0023] In the fire-resistant structural material 1B of the second embodiment, the load-bearing portion 11 is an H-beam. The fire-resistant structural material 1B also includes a burn-off coating layer 15, which burns and is burned away when exposed to fire, between the fire-resistant coating layer 12 and the non-burn-off coating layer 13. In the fire-resistant structural material 1B, the fixing member 14 penetrates the non-burn-off coating layer 13 and the non-burn-off coating layer 15 and is inserted into the fire-resistant coating layer 12.

[0024] The fire-resistant structural material 1B has a burn-resistant coating layer, which prevents the fire-resistant coating layer 12 from becoming red-hot. After the fire-resistant structural material 1 having the burn-resistant coating layer is heated and the detachable coating layer 13 falls off, the combustion of the fire-resistant structural material 1 is thought to proceed in the following order:

[0025] When the exfoliating coating layer 13 falls off and the exposed burn-resistant coating layer 15 is exposed to flames, a pyrolysis reaction primarily occurs in the burn-resistant coating layer 15, resulting in carbonization of the burn-resistant coating layer (first stage). In the first stage, the temperature of the fire-resistant coating layer 12 rises. Then, the pyrolysis reaction of the burn-resistant coating layer 15 ends, and an oxidation reaction of the burn-resistant coating layer 15 primarily occurs, turning the burn-resistant coating layer 15 to ash and beginning to burn (second stage). In the second stage, a pyrolysis reaction primarily occurs in the fire-resistant coating layer 12, resulting in carbonization of the fire-resistant coating layer 12. Then, the burn-resistant coating layer 15 is completely burned (third stage). In the fourth stage, an oxidation reaction occurs in the fire-resistant coating layer 12 along with the pyrolysis reaction. Then, the pyrolysis reaction of the fire-resistant coating layer 12 ends, and an oxidation reaction of the fire-resistant coating layer 12 primarily occurs (fourth stage). Thereafter, the oxidation reaction of the fire-resistant coating layer 12 is completed, and the fire-resistant structural material 1B stops burning (fifth stage).

[0026] As described above, in the fire-resistant structural material 1B of this embodiment, the pyrolysis reaction of the fire-resistant coating layer 12 occurs some time after the start of combustion. Therefore, the surface of the fire-resistant coating layer 12 can be kept smooth for some time after the start of combustion. Furthermore, the time during which the pyrolysis reaction and oxidation reaction of the fire-resistant coating layer 12 occur can be shortened while the fire-resistant structural material 1B is burning. Due to these factors, the fire-resistant structural material 1B of this embodiment is less likely to develop cracks or the like in the fire-resistant coating layer 12, and can be prevented from continuing to glow red.

[0027] Furthermore, even if cracks or the like occur in the burn-resistant coating layer 15 due to a thermal decomposition reaction or an oxidation reaction, and red heat is generated in the cracks, the burn-resistant coating layer 15 is burned away and does not continue to red-heat. Therefore, the red heat of the burn-resistant coating layer 15 can be prevented from being transmitted to the fire-resistant coating layer 12. This also contributes to suppressing the red heat of the fire-resistant coating layer 12.

[0028] The thickness T2 of the burn-resistant coating layer 15 is preferably less than 25 mm, more preferably less than 20 mm, from the viewpoint of making the burn-resistant coating layer 15 more likely to burn when the fire-resistant structural material 1B burns. A thickness of 25 mm or more is undesirable because it increases the burning time until the component itself burns down, thereby prolonging the burning of the component itself. The thickness of the burn-resistant coating layer 15 is preferably 5 mm or more, more preferably 10 mm or more, from the viewpoint of delaying the onset of the thermal decomposition reaction and oxidation reaction of the fire-resistant coating layer 12.

[0029] Next, the constituent materials of the fire-resistant structural materials 1 and 1B will be described. As described above, the load-bearing portion 11 is made of wood or steel. When the load-bearing portion 11 is made of wood, materials such as laminated lumber, lumber, cross-laminated timber (CLT), laminated veneer lumber (LVL), and parallel strand lumber (PSL) can be used as the load-bearing portion 11. When the load-bearing portion 11 is made of wood, the load-bearing portion 11 may be a laminate in which a plurality of laminas are stacked and bonded in a direction perpendicular to one direction, and the laminate is arranged in the same direction to form a rectangular cross section. When the load-bearing portion 11 is made of steel, a square steel pipe, an H-shaped steel, a square steel, a flat steel, a channel steel, etc. can be used as the load-bearing portion 11. Shapes other than these can also be used as the load-bearing portion 11 as long as the fire-resistant coating layer 12 can be configured around them.

[0030] The fire-resistant coating layer 12, the shedding-resistant coating layer 13, and the burn-off coating layer 15 are made of wood materials made of pure wood. In this specification, pure wood means wood that does not contain non-combustible materials, inorganic materials, etc.

[0031] Examples of pure wood that can form the fire-resistant coating layer 12 include laminated lumber, lumber, cross-laminated timber (CLT), laminated veneer lumber (LVL), parallel strand lumber (PSL), and plywood. CLT and laminated lumber may be formed by stacking multiple lamina with rectangular cross sections in the short direction, with the vertices of the rectangles overlapping. Examples of pure wood species that can form the fire-resistant coating layer 12 include larch, Douglas fir, red pine, spruce, white birch, cypress, Japanese cypress, zelkova, Scots pine, and radiata pine, with larch being preferred.

[0032] Examples of pure wood that constitutes the shedding coating layer 13 and the burn-off coating layer 15 include laminated lumber, lumber, cross-laminated timber (CLT), laminated veneer lumber (LVL), parallel strand lumber (PSL), and plywood. CLT and laminated lumber may be formed by stacking multiple lamina with rectangular cross sections in the short direction, with the vertices of the rectangles overlapping. Examples of pure wood species that constitute the shedding coating layer 13 include larch, Douglas fir, red pine, spruce, Japanese white birch, cypress, Japanese cypress, zelkova, Scots pine, Radiata pine, cedar, fir, SPF, and balsa. Among these, cedar is preferred from the viewpoint of making the shedding coating layer 13 more likely to fall off when red heat remains.

[0033] The bonding between the load-bearing portion 11 and the fire-resistant coating layer 12, and the bonding between the lamina constituting each of the load-bearing portion 11, the fire-resistant coating layer 12, and the removable coating layer 13, can be performed using various known adhesives conventionally used in the manufacture of fire-resistant structural materials, such as resorcinol resin adhesives, resorcinol-phenol resin adhesives, aqueous polymer isocyanate resin adhesives, polyurethane adhesives, and vinyl acetate adhesives. Of these, resorcinol-phenol resin adhesives are preferred from the viewpoint of further suppressing red heat.

[0034] Next, a preferred embodiment of the method for manufacturing a fire-resistant structural material of the present invention will be described, taking as an example the method for manufacturing the fire-resistant structural material 1. The manufacturing method of this embodiment includes a first step of covering the load-bearing portion 11 with a fire-resistant coating layer 12, and a second step of covering the fire-resistant coating layer 12 with a detachable coating layer 13.

[0035] In the first step, the fire-resistant coating layer 12 is bonded, for example, via an adhesive, to four side surfaces of the load-bearing portion 11 along the axial direction Z. If the fire-resistant structural material 1 is a beam, the fire-resistant coating layer 12 may be bonded to three side surfaces of the load-bearing portion 11 along the axial direction Z in the first step.

[0036] In the second step, the removable coating layer 13 is dry-bonded to the fire-resistant coating layer 12. Specifically, fixing members 14 such as screws are inserted through the removable coating layer 13 and into the fire-resistant coating layer 12, thereby bonding the removable coating layer 13 to the fire-resistant coating layer 12. In this manner, the fire-resistant structural material 1 is manufactured.

[0037] When the fire-resistant structural material 1 is used as a beam or column of a wooden building, the first step may be carried out in a factory or the like, and the material may be transported to a construction site with the fire-resistant coating layer 12 joined to the load-bearing portion 11, and the second step may be carried out at the construction site.

[0038] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to these examples. [Example]

[0039] Example 1 A fire-resistant structural material having the cross-sectional configuration shown in Figure 4 was manufactured. H-shaped steel was used for the load-bearing portion 11. Glued laminated larch lumber was used for the fire-resistant coating layer 12. Glued laminated cedar lumber was used for the shedding coating layers 13a, 13b, and 13c. The shedding coating layers 13a, 13b, and 13c were joined to the fire-resistant coating layer 12 with screws 14. Resorcinol-phenolic resin adhesive was used for all joints in the fire-resistant structural material, except for the joint between the shedding coating layer 13 and the fire-resistant coating layer 12. The dimensions of each part of the fire-resistant structural material in Example 1 are as shown in Figure 4. The distance between the screws 14, 14 in the axial direction of the fire-resistant structural material was 500 mm.

[0040] (evaluation) (90-minute combustion test) The fire-resistant structural material of Example 1 was placed horizontally in a test furnace. The fire-resistant structural material was positioned so that the 30 mm-thick deciduous coating layer 13a was on the west side and the 40 mm-thick deciduous coating layer 13b was on the east side. Each of the three sides coated with the deciduous coating layers 13a, 13b, and 13c and the fire-resistant coating layer 12 was heated for 90 minutes using the ISO 834-1 standard heating method, which simulates a typical fire. After heating, the material was allowed to cool in the furnace for 330 minutes. Temperature changes were measured at each position indicated by black dots in Figure 5 and Figures 6(a) and (b), and the temperature changes over time at each position were recorded. Figure 5 schematically shows the side of the fire-resistant structural material of Example 1 after removing the deciduous coating layers 13a, 13b, and 13c to expose the fire-resistant coating layer 12. In Figures 6(a) and (b), the deciduous coating layers 13a, 13b, and 13c are not shown. Hereinafter, the positions indicated by black dots in Figures 5 and 6(a) and (b) will be referred to as Position 1, Position 2, etc., using the numbers shown in Figures 5 and 6(a) and (b). The results of measuring the temperature change at each position are shown in Figures 7(a) and (b). A camera was also installed in the test furnace, and the condition of the heating surface of Example 1 was visually confirmed over time. Figure 8 shows the condition of the fire-resistant structural material of Example 1 after the combustion test. Figure 8 shows the east side of the fire-resistant structural material of Example 1.

[0041] In Example 1, the 30 mm-thick deciduous coating layer 13a on the west side began to fall off between 45 and 52 minutes after the start of heating, while the 40 mm-thick deciduous coating layer 13b on the east side began to fall off 58 minutes after the start of heating. The deciduous coating layer 13c on the underside of the fire-resistant structural material suddenly fell off 66 minutes after the start of heating. In Example 1, at the end of heating, only small portions of the deciduous coating layers 13a, 13b, and 13c were still attached to the screws 14 used to join the deciduous coating layers 13a, 13b, and 13c to the fire-resistant coating layer 12, and almost all of the deciduous coating layers 13a, 13b, and 13c had fallen off. In Example 1, no residual smoke or red heat was observed on any of the three heated sides after the end of cooling in the furnace. The results of Example 1 show that the fire-resistant structural material of the present invention has fire resistance that can withstand heating for 90 minutes.

[0042] Example 2 A fire-resistant structural member with the cross-sectional configuration shown in Figure 9 was manufactured. The load-bearing portion 11 and the fire-resistant coating layer 12 were made of larch glued lumber. The shedding coating layers 13a, 13b, and 13c were made of both cedar glued lumber and larch glued lumber. Specifically, when the fire-resistant structural member was axially divided into two equal parts, cedar glued lumber was used for the shedding coating layers 13a, 13b, and 13c on one side, and larch glued lumber was used for the shedding coating layers 13a, 13b, and 13c on the other side. The shedding coating layers 13a, 13b, and 13c were joined to the fire-resistant coating layer 12 with screws. The screw pitch in the axial direction of the fire-resistant structural member was 300 mm. Resorcinol-phenolic resin adhesive was used for all joints in the fire-resistant structural member, except for the shedding coating layers 13a, 13b, and 13c and the fire-resistant coating layer 12.

[0043] (evaluation) (120-minute combustion test) The fire-resistant structural material of Example 2 was placed horizontally in a test furnace. The side of the fire-resistant structural material using larch laminated timber as the deciduous coating layers 13a, 13b, and 13c faced south, while the side using cedar laminated timber as the deciduous coating layers 13a, 13b, and 13c faced north. The fire-resistant structural material was also positioned so that the 50 mm-thick deciduous coating layer 13a faced west, and the 60 mm-thick deciduous coating layer 13b faced east. Each of the three sides covered with the deciduous coating layers 13a, 13b, and 13c and the fire-resistant coating layer 12 was heated for 120 minutes using the ISO 834-1 standard heating method, which simulates a typical fire. After heating, the material was allowed to cool in the furnace for 10.5 hours. Temperature changes were measured at each of the locations indicated by black dots in Figures 10 and 11, and the temperature changes over time at each location were recorded. Figure 10 shows a schematic side view of the fire-resistant structural material of Example 2 after removing the sheddable coating layers 13a, 13b, and 13c to expose the fire-resistant coating layer 12. Figure 11 omits the sheddable coating layers 13a, 13b, and 13c. Hereinafter, the positions indicated by black dots in Figures 10 and 11 will be referred to as positions 1 and 2, respectively, using the numbers shown in Figures 10 and 11. The results of measuring the temperature changes at each position are shown in Figures 12(a)-(c) and Figures 13(a)-(c), respectively. Because visual observation of the inside of the test furnace was difficult, the subsequent shed time was estimated based on the temperature. Figures 14(a) and 14(b) show the state of the fire-resistant structural material of Example 2 after the combustion test. Both Figures 14(a) and 14(b) show the western side of the fire-resistant structural material of Example 2.

[0044] First, we will explain the deciduous coating layers 13a, 13b, and 13c on the north side of the fire-resistant structural material of Example 2, i.e., the deciduous coating layers 13a, 13b, and 13c made of cedar laminated wood. The 50 mm thick deciduous coating layer 13a on the west side fell off 60 minutes after the start of heating, and the 60 mm thick deciduous coating layer 13b on the east side fell off 70 to 90 minutes after the start of heating.

[0045] Regarding the deciduous coating layers 13a, 13b, and 13c on the south side, i.e., the deciduous coating layers 13a, 13b, and 13c made of laminated larch wood, the 50 mm thick deciduous coating layer 13a on the west side fell off 80 to 100 minutes after the start of heating, and the 60 mm thick deciduous coating layer 13b on the east side fell off 90 to 120 minutes after the start of heating.

[0046] In Example 2, at the end of heating, only a small portion of the deciduous coating layer was still attached to the screws used to join the deciduous coating layer and the fire-resistant coating layer, and almost the entire deciduous coating layer had fallen off. In Example 2, when the condition of the fire-resistant structural material was checked 710 minutes after the start of heating, no residual smoke or red heat was observed on any of the three heated sides. The results of Example 2 show that the fire-resistant structural material of the present invention has fire resistance sufficient to withstand 120 minutes of heating. [Explanation of symbols]

[0047] 1,1B Fireproof structural material 11 Load support part 12 Fire-resistant coating layer 13 Deciduous coating layer 14 Fixing member 15 Burnable coating layer

Claims

1. a wooden or steel load bearing section; a fire-resistant coating layer made of solid wood that covers the load-bearing portion; a shedding coating layer made of pure wood that covers the fire-resistant coating layer and burns, carbonizes, and falls off when exposed to flames; The fire-resistant structural material, wherein the detachable coating layer and the fire-resistant coating layer are dry-bonded.

2. 2. The fire-resistant structural material according to claim 1, wherein, when a standard heating combustion test is carried out for 90 minutes or 120 minutes in accordance with ISO 834-1, the ratio of the mass of the detachable coating layer that has fallen off to the total mass of the detachable coating layer is 80% or more at the end of heating.

3. The wood species constituting the fire-resistant coating layer is larch, 3. The fire-resistant structural material according to claim 2, wherein the wood species constituting the detachable coating layer is cedar.

4. 4. The fire-resistant structural material according to claim 3, wherein the thickness of the detachable coating layer is 15 mm or more and 70 mm or less.

5. the removable coating layer and the fire-resistant coating layer are joined by a plurality of fixing members that penetrate the removable coating layer and are inserted into the fire-resistant coating layer, 5. The fire-resistant structural material according to claim 4, wherein the distance between adjacent fixing members in the axial direction of the fire-resistant structural material is 300 mm or more and 1200 mm or less.

6. 2. The fire-resistant structural material according to claim 1, further comprising a burnable coating layer made of pure wood between the fire-resistant coating layer and the sloughable coating layer, the burnable coating layer being burned up when exposed to a flame.

7. A method for producing a fire-resistant structural material according to any one of claims 1 to 6, a first step of covering the load-bearing portion with the fire-resistant covering layer; a second step of covering the fire-resistant coating layer with the detachable coating layer, In a second step, the detachable coating layer is dry-bonded to the fire-resistant coating layer.

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