Fire-resistant structural material and method for producing the same

Abstract

To provide a fire-resistant structural material that has adequate fire resistance while being provided with a penetration part and having excellent aesthetic appearance.SOLUTION: A fire-resistant structural material 1 of the present invention has an elongated shape in one direction and includes: a load-supporting part 11 formed of steel; a flame-stopping layer 12 composed of solid wood covering the load-supporting part 11; and a sacrificial layer 13 covering the flame-stopping layer 12, the sacrificial layer 13 burning to protect the flame-stopping layer 12 when exposed to flames. The fire-resistant structural material 1 includes a penetration part 20 that penetrates the load-supporting part 11, the flame-stopping layer 12, and the sacrificial layer 13, and a tubular penetration-part covering layer 21 that covers an inner peripheral surface of the penetration part 20 is provided in the penetration part 20. Both ends of the penetration-part covering layer 21 are in contact with the sacrificial layer 13 and do not reach the surface of the sacrificial layer 13.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 fire-resistant structural materials have been proposed that have penetrations formed therein for passing facility piping, wiring, etc. For example, Patent Document 1 proposes a fire-resistant structural material with penetrations that includes a load-supporting layer, a fire-retardant fire-retardant layer that is disposed on the outside of the load-supporting layer, and a burn-in layer that is disposed on the outside of the fire-retardant layer and is made of wood. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2013-113060 Summary of the Invention [Problem to be solved by the invention]

[0004] It is desirable that a fire-resistant structural material having a penetration portion has sufficient fire resistance and also has an excellent appearance. However, in conventional fire-resistant structural materials with penetrations, it is difficult to ensure sufficient fire resistance at the penetrations, and there are cases where combustion spreads from the penetrations to the surrounding areas. On the other hand, when an attempt is made to provide a penetration coating layer on the penetrations to improve the fire resistance of the penetrations, there is a problem in that the aesthetic appearance of the fire-resistant structural material is impaired. The fire-resistant structural material described in Patent Document 1 also has room for improvement in terms of providing sufficient fire resistance and improving aesthetics.

[0005] An object of the present invention is to provide a fire-resistant structural material that has sufficient fire resistance and excellent aesthetics while having a penetration portion. [Means for solving the problem]

[0006] The present invention provides a fire-resistant structural material that is elongated in one direction and includes a steel load-bearing section, a fire-retardant layer made of pure wood that covers the load-bearing section, and a burn margin layer that covers the fire-retardant layer and burns when exposed to flames to protect the fire-retardant layer, the fire-resistant structural material having a penetration that penetrates the load-bearing section, the fire-retardant layer, and the burn margin layer, the penetration having a tubular penetration coating layer that covers the inner peripheral surface of the penetration, and both ends of the penetration coating layer contacting the burn margin layer but not reaching the surface of the burn margin layer.

[0007] The present invention also provides a method for manufacturing a fire-resistant structural material, comprising: a first step of covering a steel load-bearing-part-forming member having a first penetration that will become the load-bearing part, with a wooden fire-retardant layer-forming member having a second penetration that will become the fire-retardant layer; a second step of attaching a penetration covering material that will become the penetration covering layer to the inner surface of the second penetration; and a third step of covering the surface of the fire-retardant layer-forming member with a wooden fire-retardant layer-forming member having a third penetration that will become the fire-retardant layer, wherein in the first step, the fire-retardant layer-forming member is positioned so that the first penetration and the second penetration overlap, and in the third step, the fire-retardant layer-forming member is positioned so that the second penetration and the third penetration overlap, and both ends of the penetration covering material are in contact with the fire-retardant layer-forming member but do not reach the surface of the fire-retardant layer-forming member. [Effects of the Invention]

[0008] According to the present invention, it is possible to provide a fire-resistant structural material that has sufficient fire resistance and excellent aesthetics while having a penetration portion. [Brief explanation of the drawings]

[0009] [Figure 1] FIG. 1 is a side view schematically showing a preferred fire-resistant structural material of the present invention. [Figure 2] Fig. 2(a) is a cross-sectional view taken along line AA in Fig. 1. Fig. 2(b) is a cross-sectional view taken along line BB in Fig. 1. [Figure 3] FIG. 3 is a perspective view schematically illustrating each step of forming a preferred fire-resistant structural material of the present invention. [Figure 4] 4A to 4C are cross-sectional views schematically showing the through-holes in the steps of FIG. [Figure 5] 5(a) and 5(b) are cross-sectional views showing another preferred embodiment of the present invention, and correspond to FIG. 2(b). [Figure 6] 6(a) to 6(c) are cross-sectional views showing another preferred embodiment of the present invention, and correspond to FIG. 2(b). DETAILED DESCRIPTION OF THE INVENTION

[0010] The present invention will be described in detail below based on preferred embodiments thereof. A fire-resistant structural material 1, which is a preferred embodiment of the fire-resistant structural material of the present invention, is shown in Figures 1 and 2. Figures 2(a) and 2(b) schematically show cross sections perpendicular to the axial direction of the fire-resistant structural material 1. The fire-resistant structural material 1 of this embodiment is elongated in one direction and is a structural member used as a beam or pillar in a building. As shown in Figures 1 and 2, the fire-resistant structural material 1 comprises a steel load-bearing portion 11, a fire-stopping layer 12, a burnable layer 13, a penetration portion 20, and a penetration portion coating layer 21.

[0011] 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 H-shaped, 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.

[0012] The fire-retardant layer 12 covers the load-bearing portion 11. In this embodiment, the fire-retardant layer 12 covers three axial side surfaces of the load-bearing portion 11. The side of the fire-resistant structural material 1 on which the fire-retardant 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. Furthermore, if the fire-retardant structural material 1 is a pillar, the fire-retardant layer 12 may cover four axial side surfaces of the load-bearing portion 11.

[0013] The burnable layer 13 covers the fire-retardant layer 12. The burnable layer 13 and the fire-retardant layer 12 are dry-bonded. Specifically, the burnable layer 13 and the fire-retardant layer 12 are bonded together by a plurality of fixing members 14 that penetrate the burnable layer 13 and are inserted into the fire-retardant 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 counterbore 16 is formed in the burnable layer 13, and the heads of the fixing members 14 do not protrude from the burnable layer 13. Furthermore, a filler 17 is placed in the counterbore 16 to close the counterbore 16. Note that in Figures 2, 5, and 6, the sizes of the heads of the fixing members 14, the counterbore 16, and the filler 17 are greatly exaggerated.

[0014] The burn margin layer 13 covers the fire-stopping layer 12. The burn margin layer 13 burns when exposed to a flame, thereby protecting the fire-stopping layer 12. The fire-resistant structural material 1 of this embodiment has the burn margin layer 13, which prevents the fire-stopping layer 12 from becoming red-hot.

[0015] The fire-resistant structural material 1 is formed with a through-hole 20 having a circular cross section that penetrates from one surface to the other surface of the load-bearing portion 11, the fire-stopping layer 12, and the burn-in layer 13. The through-hole 20 is provided for the purpose of passing, for example, piping or wiring.

[0016] The penetration part 20 is provided with a tubular penetration part coating layer 21 that covers the inner peripheral surface of the penetration part 20. The penetration part coating layer 21 is intended to effectively prevent the fire resistance of the fire-resistant structural material 1 from being lost at the penetration part 20, which would affect the supporting force of the load-bearing part 11 of the fire-resistant structural material 1. The penetration part coating layer 21 is non-combustible, and is made of, for example, calcium silicate, mortar, gypsum, rock wool, or the like. The penetration portion coating layer 21 is disposed so that both ends thereof are in contact with the burnable layer 13 but do not reach the surface of the burnable layer 13 (see FIG. 2(b)).

[0017] The fire-resistant structural material 1 of the present invention is provided with a penetration coating layer 21 at the penetration part 20, so even in the event of exposure to fire, the influence of flames and heat that have penetrated the penetration part 20 on the load-bearing part 11 can be suppressed by the penetration coating layer 21. Therefore, the fire-resistant structural material 1 has sufficient fire resistance despite having the penetration part 20. Furthermore, in the fire-resistant structural material 1 of the present invention, both ends of the penetration coating layer do not reach the surface of the burnable layer 13, and both ends of the penetration coating layer 21 do not appear on the outer surface of the fire-resistant structural material 1, which prevents the penetration coating layer 21 from spoiling the aesthetic appearance of the fire-resistant structural material 1. For example, if you want to make the most of the appearance of the wood pattern that makes up the burnable layer 13, you can make use of that appearance. Furthermore, in the fire-resistant structural material 1 of the present invention, both ends of the penetration portion coating layer 21 are in contact with the burnable layer 13, so that the penetration of fire into the fire-stopping layer 12 through the gap between the penetration portion coating layer 21 and the burnable layer 13 is suppressed. Thus, the fire-resistant structural material 1 of the present invention has a penetration portion, has sufficient fire resistance, and is also aesthetically pleasing.

[0018] The inner diameter L2 of the penetration coating layer 21 is preferably equal to or greater than the diameter L1 of the opening of the penetration 20, from the viewpoint of improving the aesthetic appearance of the fire-resistant structural material 1 and imparting sufficient fire resistance to the fire-resistant structural material 1. In this way, the penetration coating layer 21 cannot be seen from the outside of the fire-resistant structural material 1, which further improves the aesthetic appearance of the fire-resistant structural material 1 and also makes it possible to suppress the penetration of flames and heat into the penetration 20. From the above viewpoint, the inner diameter L2 of the through-hole covering layer 21 is preferably larger than the diameter L1 of the opening of the through-hole 20 by 10 mm or more, and more preferably by 20 mm or more.

[0019] From the viewpoint of imparting high fire resistance to the fire-resistant structural material 1, the burnable layer 13 is preferably a shedding coating layer that burns, carbonizes, and falls off when exposed to flames. The shedding of the burnable layer 13 allows the fire-resistant structural material 1 to exhibit sufficient fire resistance. Although red heat may remain in cracks in the carbonized layer formed by the combustion of the burnable layer 13, the burnable layer 13 falls off, so even if red heat remains inside the carbonized layer formed by the combustion of the burnable 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 ended.

[0020] It is preferable that the burnable layer 13 does not fall off for a certain time after the start of heating of the fire-resistant structural material 1, and falls off after the certain time has elapsed. By not letting the burnable layer 13 fall off for a certain time after the start of heating of the fire-resistant structural material 1, the burnable layer 13 covers the fire-stopping layer 12 for a certain time after the start of heating, and the fire-stopping layer 12 can be prevented from being directly exposed to flames. From the viewpoint of preventing the fire-stopping layer 12 from being directly exposed to flames, it is preferable that the burnable 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.

[0021] The thickness T1 of the marginal burn 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 detachment of the marginal burn layer 13 when red heat remains in the marginal burn layer 13. The thickness T1 of the marginal burn 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-stop layer 12 from being directly exposed to flames.

[0022] The ease with which the burnable layer 13 falls off can also be adjusted by the pitch of the fixing members 14 in the axial direction Z. Specifically, if the distance D between adjacent fixing members 14 in the axial direction Z is narrowed, the burnable layer 13 becomes less likely to fall off, and if the distance D is widened, the burnable layer 13 becomes more likely to fall off.

[0023] To facilitate the detachment of the burnable layer 13 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-stop 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.

[0024] When damage such as cracks occurs in the surface burnable layer 13 of the fire-resistant structural material 1 due to a fire or the like, it is possible to replace only the burnable layer 13. Because it is possible to replace only the burnable layer 13 of the fire-resistant structural material 1, the cost of repairing the fire-resistant structural material 1 can be reduced.

[0025] Next, the constituent materials of the fire-resistant structural material 1 will be described. As described above, the load-bearing portion 11 is made of steel. Square steel pipes, H-shaped steel, square steel, flat steel, channel steel, etc. can be used as the load-bearing portion 11, but H-shaped steel is particularly preferable from the viewpoint of providing sufficient fire resistance to the fire-resistant structural material. Also, any shape other than these can be used as the load-bearing portion 11 as long as it can be surrounded by the fire-retardant layer 12.

[0026] The fire-stopping layer 12 and the burning margin layer 13 are made of wood material made of pure wood. In this specification, pure wood means wood that does not contain non-combustible materials or inorganic materials.

[0027] Examples of pure wood that can form the fire-retardant 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 made 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-retardant layer 12 include larch, Douglas fir, red pine, spruce, white birch, cypress, Japanese cypress, zelkova, Scots pine, and Radiata pine, with larch being preferred.

[0028] Examples of pure wood that constitutes the burn layer 13 include laminated lumber, lumber, cross-laminated timber (CLT), laminated veneer lumber (LVL), parallel strand lumber (PSL), and plywood. CLT and laminated lumber may be made 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 burn 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 burn layer 13 more likely to fall off if red heat remains.

[0029] The load-bearing portion 11 and the fire-retardant layer 12 can be joined using known fasteners such as bolts, nuts, and drift pins, for example, a method using a lag screw bolt. The laminae that make up the fire-retardant layer 12 and the burning margin layer 13 can be joined together using, for example, various known adhesives that have traditionally been used in the manufacture of fire-resistant structural materials.Specific examples include 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 perspective of further suppressing red heat. The load-bearing portion 11 and the fire-retardant layer 12 can be joined to the penetration portion coating layer 21 by, for example, a method using a known adhesive such as a calcium carbonate-based adhesive, a gypsum-based adhesive, or a sodium silicate-based adhesive, or by a method using fasteners such as screws, bolts, or nails.

[0030] Next, a preferred embodiment of the method for manufacturing a fire-resistant structural material of the present invention will be described using as an example the method for manufacturing fire-resistant structural material 1. The manufacturing method of this embodiment includes a first step of covering a steel load-bearing-part-forming member 11A having a first penetration part 20A that will become load-bearing part 11 with a wooden fire-retardant-layer-forming member 12A having a second penetration part 20B that will become fire-retardant layer 12; a second step of attaching a penetration part coating material 21A that will become penetration part coating layer 21 to the inner peripheral surface of second penetration part 20B; and a third step of coating the surface of fire-retardant-layer-forming member 12A with a wooden fire-retardant-layer-forming member 13A having a third penetration part 20C that will become fire-retardant layer 13.

[0031] In the first step, fire-retardant layer-forming members 12A are arranged on three axial side surfaces of load-supporting portion-forming member 11A (see FIGS. 3(A) and 4(A)) so that the first penetration portion 20A and the second penetration portion 20B overlap, and the load-supporting portion-forming member 11A and the fire-retardant layer-forming member 12A are joined together, for example, with lag screw bolts (not shown), and the fire-retardant layer-forming members 12A are joined together, for example, with an adhesive (see FIGS. 3(B) and 4(B)). If the fire-resistant structural material 1 is a pillar, in the first step, fire-retardant layer-forming members 12A may be joined to four axial side surfaces of load-supporting portion-forming member 11A along the axial direction Z.

[0032] In the second step, the penetrating part covering material 21A that will become the penetrating part covering layer 21 is inserted into the inner peripheral surface of the second penetrating part 20B and bonded via, for example, an adhesive (see FIGS. 3(C) and 4(C)).

[0033] In the third step, the burnable layer-forming member 13A is positioned so that the second penetration portion 20B and the third penetration portion 20C overlap. At this time, the penetration portion covering material 21A is positioned and joined so that both ends of the burnable layer-forming member 13A are in contact with the burnable layer-forming member 13A but do not reach the surface of the burnable layer-forming member 13A. Examples of joining methods include dry joining (see FIGS. 3(D) and 4(D)). Examples of dry joining include methods using fixing members 14 such as screws. Specifically, fixing members 14 such as screws are used to penetrate the burnable layer 13 and insert them into the fire-stopping layer 12, thereby joining the burnable layer 13 to the fire-stopping layer 12. In this manner, the fire-resistant structural material 1 is manufactured.

[0034] The present invention is not limited to the above-described embodiments and can be modified as appropriate. The above-described embodiments may also be combined.

[0035] For example, the penetration covering layer 21 may contain a fire-resistant material 25 from the viewpoint of imparting high fire resistance to the fire-resistant structural material 1. Specifically, as shown in Figures 5(a) and (b), the penetration covering layer 21 may have a fire-resistant material-accommodating penetration 24 that penetrates the penetration covering layer 21 in its thickness direction, and the fire-resistant material 25 may be accommodated inside the fire-resistant material-accommodating penetration 24. The fire-resistant material-accommodating penetration 24 may be a groove that is continuous all around the circumferential direction of the penetration covering layer 21, or may be through-holes that are arranged intermittently in the circumferential direction of the penetration covering layer 21. In this way, when the fire-resistant structural material 1 is exposed to flame, the fire-resistant material 25 foams and / or expands, filling all or part of the inner surface of the penetration portion coating layer 21, thereby exerting a flame and heat blocking effect, thereby further suppressing the impact of flame and heat that has entered the penetration portion 20 from the outside on the load-bearing portion 11. When the fire-resistant structural material 1 has the fire-resistant material 25, the fire-resistant material 25 may be fixed to the load-supporting portion 11 before the load-supporting portion 11 is covered with the fire-retardant layer 12, or may be fixed to the load-supporting portion 11 after the load-supporting portion 11 is covered with the fire-retardant layer 12. Furthermore, when the fire-resistant material 25 is disposed after the load-supporting portion 11 is covered with the fire-retardant layer 12, the fire-resistant material 25 may be fixed before, after, or simultaneously with the attachment of the penetration covering layer 21. As an example of a mode in which the fire-resistant material 25 is fixed simultaneously, the fire-resistant material 25 may be fixed in advance to the side of the penetration covering layer 21 on the side of the fire-resistant material-accommodating penetration 24.

[0036] Examples of the fire-resistant material 25 include an intumescent fire-resistant tape, an intumescent fire-resistant sheet, an intumescent caulking material, an intumescent fire-resistant paint, etc. Among these, it is preferable to use an intumescent fire-resistant tape from the viewpoint of being able to be applied easily in a short time. As the foam fireproof tape, commercially available products can also be used, such as Sleeve Tasuke (product name) manufactured by Nippon Insulation Co., Ltd. The intumescent fire-resistant tape and intumescent fire-resistant sheet each foam when exposed to heat to form a heat insulating layer. The intumescent fire-resistant tape and intumescent fire-resistant sheet each contain resin as their main constituent material. Examples of the resin that is the main constituent material of the intumescent fire-resistant tape and intumescent fire-resistant sheet include butyl rubber, epoxy resin, vinyl chloride resin, and thermally expandable graphite. The intumescent fire-resistant sheet can be fixed to one or more of the side of the fire-resistant material housing penetration 24, the load support portion 11, and the fire-retardant layer 12 using, for example, adhesive, staples, or the like. Since the intumescent caulking material and intumescent fire-resistant paint can be applied by coating or spraying them onto the application area, they can be easily applied even to areas where it is difficult to apply intumescent fire-resistant tape or intumescent fire-resistant sheet. Examples of resins that are the main constituent materials of the intumescent caulking material and intumescent fire-resistant paint include silicone resins, acrylic resins, vinyl acetate resins, epoxy resins, and urethane resins.

[0037] Furthermore, for example, the inner diameter L2 of the penetration part covering layer 21 of the fire-resistant structural material 1 is constant, but as shown in Figures 6(a) to 6(c), the inner diameter L2 does not have to be constant. In this case, the inner diameter of the penetration part covering layer 21 is defined as the inner diameter L2 of the penetration part covering layer 21 at the part where the thickness of the penetration part covering layer 21 is the largest, i.e., the part where the inner diameter of the penetration part covering layer 21 is the smallest.

[0038] The marginal layer 13 may be a marginal layer based on a known marginal layer design. Such a marginal layer has a thickness according to the required fire resistance time. For example, a marginal layer having a thickness of 45 mm or more is designed to provide a quasi-fire resistance performance of one hour. Furthermore, the burnable layer 13 may be the burnable coating layer described in JP 2022-112906 A instead of the removable coating layer in the above-described embodiment. The descriptions regarding the various dimensions of the embodiment having the removable coating layer can also be applied appropriately to other burnable layers.

[0039] Furthermore, the manufacturing method of the fire-resistant structural material 1 may include a step of attaching fire-resistant material 25 to the inner peripheral surface of first penetration portion 20A. The manufacturing method of the fire-resistant structural material 1 may include, for example, a step of fixing fire-resistant material 25 to load-supporting portion-forming member 11A before covering load-supporting portion-forming member 11A with fire-retardant layer-forming member 12A, or a step of fixing fire-resistant material 25 to load-supporting portion-forming member 11A after covering load-supporting portion-forming member 11A with fire-retardant layer-forming member 12A. [Explanation of symbols]

[0040] 1 Fireproof structural materials 11 Load support part 11A Load support portion forming member 12 Fire-retardant layer 12A Fire-retardant layer forming material 13 Burning layer 13A Burning margin layer forming material 14 Fixing parts, screws 20 Penetration 20A First penetration 20B Second penetration 20C Third penetration 21 Penetration coating layer 21A Penetration part covering material 24 Fireproofing material containing penetration 25 Fireproof materials

Claims

1. a steel load bearing portion; a fire-retardant layer made of solid wood covering the load-bearing portion; A fire-resistant structural material having a long shape in one direction, the fire-retardant layer being covered with a burn-in layer that burns when exposed to a flame to protect the fire-retardant layer, a penetration portion that penetrates the load support portion, the fire-retardant layer, and the burn-in layer; A fire-resistant structural material in which a tubular penetration coating layer is provided on the penetration portion to cover the inner peripheral surface of the penetration portion, and both ends of the penetration coating layer are in contact with the burnable layer but do not reach the surface of the burnable layer.

2. 2. The fire-resistant structural material according to claim 1, wherein the burnt margin layer is a sloughable coating layer that burns and falls off when exposed to a flame.

3. 2. The fire-resistant structural material according to claim 1, wherein the inner diameter of the penetration covering layer is equal to or greater than the diameter of the opening of the penetration.

4. 2. The fire-resistant structural material according to claim 1, wherein the load-bearing portion is an H-shaped steel.

5. The species of wood constituting the fire-retardant layer is larch, 2. The fire-resistant structural material according to claim 1, wherein the wood species constituting the burn layer is cedar.

6. 2. The fire-resistant structural material according to claim 1, wherein the thickness of the burnt margin layer is 15 mm or more and 70 mm or less.

7. A method for producing a fire-resistant structural material according to any one of claims 1 to 6, a first step of covering a steel load-bearing-portion-forming member having a first penetration portion, which serves as the load-bearing portion, with a wooden fire-retardant layer-forming member having a second penetration portion, which serves as the fire-retardant layer; a second step of attaching a penetration portion coating material that will become the penetration portion coating layer to an inner circumferential surface of the second penetration portion; and a third step of covering the surface of the fire-retardant layer-forming member with a wooden fire-retardant layer-forming member having a third penetration portion, which becomes the fire-retardant layer. In the first step, the fire-retardant layer-forming member is arranged so that the first penetration portion and the second penetration portion overlap each other, In the third step, the burnable layer forming member is arranged so that the second penetration portion and the third penetration portion overlap, and both ends of the penetration portion covering material are arranged so that they are in contact with the burnable layer forming member but do not reach the surface of the burnable layer forming member.

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