Design method for fireproof coating beam

Abstract

To reduce weight and construction costs while ensuring fire resistance with a fireproof coating thickness equal to or less than that of conventional products.SOLUTION: In a design method for a fireproof coating beam, a yield strength of an H-shaped steel beam is set to 440 N / mm2 or more. The fireproof coating material 3 is provided in a box-type coating on the H-shaped steel beam, excluding an upper surface of an upper flange 21. The box-type coating has a pair of vertical sections positioned at a position connecting ends of the upper flange 21 and a lower flange 22, and corresponding to a length of the beam, and a horizontal section positioned along a lower surface of the lower flange 22 and connected to a lower end of the vertical section, and is provided with a heating circumference consisting of the pair of vertical sections and the horizontal section. A design method for the fireproof coating beam is provided for the H-shaped steel beam which has a sectional secondary moment equivalent to that of the H-shaped steel beam, a yield strength of 235 N / mm2 and a web width-to-thickness ratio of 100 or more, and a thickness of the fireproof coating is set to 10 mm or more and 55 mm or less for a 1-hour fireproof specification, 20 mm or more and 115 mm or less for a 2-hour fireproof specification, or 40 mm or more and 130 mm or less for a 3-hour fireproof specification.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for designing a fire-resistant coated beam. [Background technology]

[0002] It has been known that the strength and rigidity of steel materials rapidly decrease at high temperatures. When steel materials are used as structural members of a building, it is necessary to ensure fire resistance so that the building does not collapse while residents, users, etc. are evacuating. Therefore, when H-shaped steel beams are used as structural members, the outer surface of the H-shaped steel is conventionally covered with a fire-resistant covering material (see, for example, Patent Documents 1 to 3). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6409396 [Patent Document 2] Patent No. 4198292 [Patent Document 3] Japanese Patent Application Publication No. 2019-90212 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the fire-resistant coated beams disclosed in the above-mentioned Patent Documents 1 to 3 have the following problems. That is, when used as a beam, for example, there is a demand for cost reduction by reducing the weight. One possible solution to reduce the weight is to make the web thinner, but a thin web tends to heat up easily, so it is necessary to make the fire-resistant covering thicker. In other words, reducing the weight of components means making them thinner, but this reduces the heat capacity and therefore the fire resistance, which is a problem, and there is room for improvement in this regard.

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a design method for fire-resistant coated beams that can reduce weight and construction costs and ensure fire resistance performance with a fire-resistant coating thickness that is equal to or less than that of conventional beams. [Means for solving the problem]

[0006] In order to achieve the above object, the design method of the fire-resistant covered beam according to the present invention is directed to a H-shaped steel beam that has an upper flange, a lower flange, and a web and supports a floor slab from below, and the web width-thickness ratio (H-2 × t2) / t1, which is the ratio of the web height (beam height H-2 × flange thickness t2) (mm) to the web thickness t1 (mm), is set to 100 or more, and the entire exposed surfaces of the upper flange, the lower flange, and the web are covered with a fire-resistant covering material, and the yield strength of the H-shaped steel beam is set to 440 N / mm 2 The fire-resistant covering material is provided as a box covering on the H-shaped steel beam excluding the upper surface of the upper flange, and the box covering has a pair of vertical surface portions arranged at a position connecting the ends of the upper flange and the lower flange and corresponding to the length of the beam, and a horizontal surface portion arranged along the lower surface of the lower flange and connected to the lower end of the vertical surface portion, and is provided with a heating perimeter consisting of the pair of vertical surface portions and the horizontal surface portion, and the thickness of the fire-resistant covering material has a moment of inertia equivalent to that of the H-shaped steel beam and a yield strength of 235 N / mm 2 In the case of H-shaped steel beams with a web width-thickness ratio of 100 or more, the thickness is set to 10 mm or more and 55 mm or less for 1-hour fire resistance specifications, 20 mm or more and 115 mm or less for 2-hour fire resistance specifications, or 40 mm or more and 130 mm or less for 3-hour fire resistance specifications. The design method for a fire-resistant covered beam according to the present invention is directed to a method for designing an H-shaped steel beam that has an upper flange, a lower flange, and a web and supports a floor slab from below, in which the web width-thickness ratio (H-2 × t2) / t1, which is the ratio of the web height (beam height H-2 × flange thickness t2) (mm) to the web thickness t1 (mm), is set to 100 or more, and the entire exposed surfaces of the upper flange, the lower flange, and the web are covered with a fire-resistant covering material, and the yield strength of the H-shaped steel beam is reduced to 440 N / mm. 2The fire-resistant covering material is directly attached to the H-shaped steel beam except for the upper surface of the upper flange, and the directly attached material has a pair of vertical surface portions arranged along both side surfaces of the web and horizontal surface portions arranged along the lower surface of the upper flange and the upper and lower surfaces of the lower flange, and is provided with a heating perimeter that covers the pair of vertical surface portions and the horizontal surface portions, and the thickness of the fire-resistant covering material has a moment of inertia equivalent to that of the H-shaped steel beam and a yield strength of 235 N / mm 2 In the case of H-shaped steel beams with a web width-thickness ratio of 100 or more, the thickness is set to 10 mm or more and 60 mm or less for 1-hour fire resistance specifications, 25 mm or more and 120 mm or less for 2-hour fire resistance specifications, or 45 mm or more and 135 mm or less for 3-hour fire resistance specifications. The design method for a fire-resistant covered beam according to the present invention is directed to a H-shaped steel beam that has an upper flange, a lower flange, and a web and supports a floor slab from below, and is characterized in that the web width-thickness ratio (H-2 × t2) / t1, which is the ratio of the web height (beam height H-2 × flange thickness t2) (mm) to the web thickness t1 (mm), is set to 100 or more, and the exposed surfaces of the upper flange, the lower flange, and the web are entirely covered with a fire-resistant covering material by spraying rock wool, and the yield strength of the H-shaped steel beam is reduced to 440 N / mm. 2 The fire-resistant covering material covers the H-shaped steel beam except for the upper surface of the upper flange, and the rock wool spraying has a pair of vertical surface portions arranged along both side surfaces of the web and horizontal surface portions arranged along the lower surface of the upper flange and the upper and lower surfaces of the lower flange, and is provided with a heating perimeter that covers the pair of vertical surface portions and the horizontal surface portions, and the thickness of the fire-resistant covering material has a second moment of area equivalent to that of the H-shaped steel beam and a yield strength of 235 N / mm 2 In the case of H-shaped steel beams with a web width-thickness ratio of 100 or more, the thickness is set to 10 mm or more and 45 mm or less for 1-hour fire resistance specifications, 20 mm or more and 70 mm or less for 2-hour fire resistance specifications, or 30 mm or more and 90 mm or less for 3-hour fire resistance specifications.

[0007] In the present invention, a predetermined fire resistance performance can be achieved in an H-shaped steel beam in which the entire exposed surface of the beam is covered with a fire-resistant coating material and the web width-thickness ratio (H-2 × t2) / t1 is set to 100 or more. In other words, by using an H-shaped steel beam with high yield strength, even if the web width-thickness ratio (H-2 × t2) / t1 of the fire-resistant coated beam is set to 100 or more, it is possible to reduce the thickness of the fire-resistant coating while ensuring sufficient fire resistance, and fire resistance performance can be ensured with a fire-resistant coating thickness equal to or less than that of conventional beams. Therefore, in the present invention, by using high-strength steel with thin webs as the beam material, it is possible to suppress the decline in fire resistance performance due to temperature rise, and the coating thickness of the fire-resistant coating material can be kept at or below the conventional level, thereby achieving weight reduction and reduction in construction costs.

[0008] In addition, in the design method of a fire-resistant covered beam according to the present invention, it is preferable that the web width-thickness ratio (H-2×t2) / t1 is set in the range of 100 or more and 160 or less.

[0009] In the present invention, the web width-thickness ratio (H-2×t2) / t1 is set in the range of 100 or more and 160 or less, thereby more reliably ensuring the fire resistance of the H-shaped steel beam.

[0010] In addition, in the design method of a fire-resistant covered beam according to the present invention, it is preferable that the web width-thickness ratio (H-2×t2) / t1 is set in the range of 100 or more and 160 or less.

[0011] In addition, the design method of the fire-resistant covered beam according to the present invention is to provide the H-shaped steel beam with the heating circumference ratio Hs / As (m -1 ) may be characterized in that it satisfies the range of 228 to 394 in the case of box pasting, and satisfies the range of 5775 272 to 496 in the case of direct pasting.

[0012] In the present invention, the heating perimeter Hs (mm) and the cross-sectional area As (mm 2 ) and the heating perimeter ratio Hs / As(m -1) is within the range of 228 to 496, the fire resistance of the H-shaped steel beam can be more reliably ensured. [Effects of the Invention]

[0013] According to the design method of the fire-resistant coated beam of the present invention, it is possible to reduce the weight and construction costs, and to ensure fire resistance performance with a fire-resistant coating thickness equal to or less than that of conventional beams. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a perspective view showing, in vertical section, the configuration of a fire-resistant coated beam that supports a concrete slab from below according to an embodiment of the present invention. FIG. [Figure 2] FIG. 2 is a longitudinal cross-sectional view of the fire-resistant coated beam shown in FIG. [Figure 3] 1 is a graph showing the relationship between the temperature of a steel material and the stress at 1% strain. [Figure 4] FIG. 10 is a diagram showing the fire resistance performance according to the examples, and is a diagram showing the relationship between the heating circumference ratio and the coating thickness in an H-shaped steel beam. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, a method for designing a fire-resistant covered beam according to an embodiment of the present invention will be described with reference to the drawings.

[0016] As shown in Figures 1 and 2, the fire-resistant coated beam 1 of this embodiment has a fire-resistant structure in which an H-shaped steel beam 2 (H-shaped steel beam) that supports a concrete slab 10 from below is covered with fire-resistant coating material 3 around the entire periphery.

[0017] The beam 2 has an upper flange 21, a lower flange 22, and a web 23. The beam 2 has a yield strength σ y is 235N / mm 2 The beam 2 is covered with a fire-resistant covering material 3 on the entire exposed surfaces of the upper flange 21, the lower flange 22, and the web 23. Here, the yield strength σ of the beam 2 isy As a result, it is 295N / mm 2 It is preferable that the load is equal to or greater than 325 N / mm 2 More preferably, 385N / mm 2 Above 440N / mm 2 That is all.

[0018] The beam material 2 of this embodiment employs a web width-thickness ratio (H-2×t2) / t1, which is the ratio of the web height (H-2×t2) (mm) of the web 23 to the thickness t1 (mm) of the web 23, set to 100 or more, where H (mm) is the beam thickness and t2 (mm) is the flange thickness of the upper flange 21 and the lower flange 22. Furthermore, the web width-thickness ratio (H-2×t2) / t1 is set in the range of 100 or more and 160 or less. Specific dimensions of the beam material 2 may be, for example, a beam height H of 700 mm, a flange width B of the upper flange 21 and the lower flange 22 of 175 mm, a web thickness t1 of 4.5 mm, and a flange thickness t2 of 9 mm.

[0019] Here, the X direction in the drawing is the longitudinal direction of the beam 2, the Y direction is the width direction of the beam 2, and the Z direction is the vertical direction of the beam 2.

[0020] A concrete slab 10 having a predetermined slab thickness (for example, a slab thickness of about 100 mm to 300 mm) is joined to the beam 2 above the upper flange 21. In other words, the beam 2 is used as a floor beam, which is a structural member that supports the concrete slab 10. This concrete slab 10 is a slab-like component that is poured above the beam material 2 and hardened after mixing cement, fine aggregate, coarse aggregate, water, admixtures, additives, etc. to achieve a specified design standard strength.

[0021] The fire-resistant covering material 3 covers the entire periphery of the beam 2, except for the upper surface 21a of the upper flange 21 to which the concrete slab 10 is joined, with a predetermined covering thickness t0. The fire-resistant coating material 3 is applied by, for example, spraying, painting, molded plate, or wrapping. For example, wrapped rock wool is a type of dry fire-resistant coating material, and is a two-layer structure made by melting inorganic materials such as steel slag or basalt at high temperature and blowing them away using centrifugal force to turn them into fibrous rock wool, with a nonwoven fabric attached to prevent dust from scattering. Furthermore, inorganic plate-shaped materials such as gypsum board, calcium silicate board, ALC, and cement board can be used as the fire-resistant coating material for molded plates.

[0022] The fire-resistant covering material 3 used in this embodiment is set to satisfy the following ranges. Beam 2 (H-shaped steel beam) heating perimeter Hs (mm) and cross-sectional area As (mm 2 ) and the heating perimeter ratio Hs / As(m -1 ) is set to satisfy the range of 228 to 496. Here, the heated perimeter Hs is the perimeter of the surface area of the beam 2 covered with the fire-resistant covering material 3.

[0023] In addition, the heating circumference ratio Hs / As (m -1 ) and preferably satisfies the range of 228 to 394 in the case of box pasting, and satisfies the range of 272 to 496 in the case of direct pasting.

[0024] Here, the thickness of the fire-resistant covering material 3 varies depending on the fire-resistant time, the yield strength of the beam material 2, and the covering method of the fire-resistant covering material. For example, in the fire-resistant coated beam 1 of this embodiment, the yield strength of the beam material 2 is 235 N / mm 2 In this case, for box pasting, the thickness is set to 10mm or more and 55mm or less for 1-hour fire resistance, 20mm or more and 115mm or less for 2-hour fire resistance, and 40mm or more and 130mm or less for 3-hour fire resistance. On the other hand, for direct pasting, the thickness is set to 10mm or more and 60mm or less for 1-hour fire resistance, 25mm or more and 120mm or less for 2-hour fire resistance, and 45mm or more and 135mm or less for 3-hour fire resistance. In addition, the yield strength of beam 2 is 440N / mm 2In this case, for box pasting, the thickness is set to 5mm or more and 50mm or less for 1-hour fire resistance, 15mm or more and 110mm or less for 2-hour fire resistance, and 35mm or more and 125mm or less for 3-hour fire resistance. On the other hand, for direct pasting, the thickness is set to 5mm or more and 55mm or less for 1-hour fire resistance, 20mm or more and 115mm or less for 2-hour fire resistance, and 40mm or more and 130mm or less for 3-hour fire resistance. Furthermore, when the fireproof coating beam 1 is sprayed with rock wool, the yield strength of the beam material 2 is 235N / mm 2 When the yield strength of beam 2 is 440N / mm, the thickness is set to 10mm or more and 45mm or less for 1-hour fire resistance, 20mm or more and 70mm or less for 2-hour fire resistance, and 30mm or more and 90mm or less for 3-hour fire resistance. 2 In this case, the thickness is set to 5mm or more and 40mm or less for 1-hour fire resistance, 15mm or more and 65mm or less for 2-hour fire resistance, and 25mm or more and 85mm or less for 3-hour fire resistance.

[0025] Next, the operation of the fire-resistant covered beam 1 described above will be described in detail with reference to the drawings. In this embodiment, as shown in Fig. 2, the entire exposed surface of the beam 2 is covered with the fire-resistant coating material 3, and the beam 2 has a web width-thickness ratio (H-2 x t2) / t1 set to 100 or more, so that it can exhibit a predetermined fire resistance performance. In other words, by using a beam 2 with high yield strength, even if the web width-thickness ratio (H-2 x t2) / t1 of the fire-resistant coated beam 1 is set to 100 or more, it is possible to reduce the thickness of the fire-resistant coating while ensuring sufficient fire resistance, and it is possible to ensure fire resistance with a fire-resistant coating thickness equal to or less than that of conventional ones.

[0026] Here, the relationship between the strength of the steel material used for the beam and the temperature will be described. The graph shown in Figure 3 shows the relationship between the temperature of the steel material and the stress of the steel material at 1% strain at each temperature. The horizontal axis of this graph represents the temperature of the steel material, and the vertical axis represents the stress of the steel material at 1% strain. Of the two graph lines L1 and L2, the solid graph line L1 (with a circle) represents the steel material with a tensile strength of 600 MPa (yield strength 440 N / mm 2 ) steel material, and the dashed graph line L2 (legend: △) represents the 400 MPa class (yield strength 235 N / mm 2) steel materials. As is clear from comparing the graph lines L1 and L2 in this figure, the greater the tensile strength and yield strength of the steel material, the more it can maintain high tensile strength and yield strength even in high temperature ranges, and the higher its fire resistance performance. Therefore, if the beam has the same cross-sectional shape (H-shaped cross section), increasing the yield strength will also improve the fire resistance. In other words, if a beam with high yield strength is used, even if the web is thinner within a certain range, it will still achieve fire resistance equal to or greater than that of a beam with low yield strength. As a result, even if the heat capacity of the beam decreases due to the thinner web, the fire resistance of the beam actually increases, making it possible to reduce the thickness of the fire-resistant coating.

[0027] In this way, in this embodiment, by using high-strength steel with a thin web 23 as the beam material 2, it is possible to suppress the deterioration of fire resistance performance due to temperature rise, and the coating thickness t0 of the fire-resistant coating material 3 can be kept at or below the conventional level, thereby achieving weight reduction and reduction in construction costs.

[0028] In addition, in the embodiment, the web width-thickness ratio (H-2×t2) / t1 is set in the range of 100 or more and 160 or less, thereby more reliably ensuring the fire resistance of the beam material 2.

[0029] In this embodiment, the heating perimeter Hs (mm) and the cross-sectional area As (mm 2 ) and the heating perimeter ratio Hs / As(m -1 ) is in the range of 228 or more and 496 or less, the fire resistance of the beam material 2 can be more reliably ensured.

[0030] Furthermore, in this embodiment, the heating perimeter Hs (mm) and the cross-sectional area As (mm 2 ) and the heating perimeter ratio Hs / As(m -1 ) is in the range of 228 or more and 496 or less, the fire resistance of the beam material 2 can be more reliably ensured.

[0031] Furthermore, in this embodiment, compared to H-shaped steel beams whose fire-resistant covering thickness is certified according to each certification specification in accordance with predetermined fire resistance conditions, the covering thickness of the fire-resistant covering material 3 can be made relatively thinner than the covering thickness of each certification specification. Therefore, the material cost of the fire-resistant covering material 3 can be reduced, and construction costs can be reduced. In addition, in this embodiment, H-shaped steel beams certified according to the above-mentioned certification specifications are the target of application, but at least H-shaped steel beams with certified specifications at the time of application are certainly the target of application.

[0032] The fire-resistant coated beam 1 according to the present embodiment described above can reduce weight and construction costs, and can ensure fire resistance with a fire-resistant coating thickness equal to or less than that of conventional ones.

[0033] Next, an example will be described below to support the configuration of the fire-resistant covered beam 1 according to the above-described embodiment.

[0034] (Example) In the example, the application range shown in the above-mentioned embodiment is the case of the fire-resistant coated beam 1 shown in Table 1 (yield strength 440 N / mm 2 ) and the comparison case of the conventional wrapping coating shown in Table 2 (yield strength 235 N / mm 2 The web width-thickness ratio (H-2 × t2) / t1 and the heating circumference ratio Hs / As were calculated and compared in both cases. The symbols H, B, t1, and t2 in Tables 1 and 2 are shown in Figure 2.

[0035] [Table 1]

[0036] [Table 2]

[0037] The experimental case shown in Table 1 has six cross-sectional dimensions for beams made of high-strength, thin-walled, welded H-shaped steel beams with a web width-thickness ratio (H-2 × t2) / t1 in the range of 100 to 160. Table 1 also shows the web width-thickness ratio (H-2 × t2) / t1 and the heated circumference ratio Hs / As for each experimental case. The specifications for the fire-resistant coating material were set to be equivalent to the coating thickness for the required fire resistance time and shape combination in the comparative case shown in Table 2. That is, the coating thickness of the fire-resistant coating material in the experimental case is set to 20 mm for a 1-hour fire resistance time and 65 mm for a direct-applied coating with a 2-hour fire resistance time, for example.

[0038] The comparative case shown in Table 2 was made using nine members of different dimensions, with fire-resistant coating certification specifications for Makibee (registered trademark, manufactured by Nichias Corporation). The fire-resistant coating certification specifications were for beams, with three fire-resistance patterns of 1 hour, 2 hours, and 3 hours, two coating patterns for box-attached and direct-attached coating, and thicknesses of 20 to 105 mm for a total of nine members. Table 2 also shows the web width-thickness ratio H / t1 and heating circumference ratio Hs / As for each member in the comparative case.

[0039] Figure 4 shows the heating perimeter ratio (m -1 ) and box cladding thickness (mm) at a fire resistance time of 2 hours. Graph P is the result of plotting the heated perimeter ratio for box cladding thicknesses of 40mm, 65mm, and 80mm at a fire resistance time of 2 hours for the comparison cases shown in Table 2. In other words, Graph P shows the previous certified specifications. The certified specifications are the fire resistance structure certification based on Article 107, Item 1 of the Enforcement Order of the Building Standards Act. The first range F1 on the left side of graph P indicates the range assumed to be possible with previous certification (comparison case). On the other hand, the range plotted for the heated perimeter ratio in the implementation case shown in Table 1 is the second range F2 on the right side of graph P.

[0040] In this example, as shown in Figure 4, the coating thickness can be reduced by decreasing the heating circumference ratio Hs / As. Therefore, a coating thickness of 40 mm is possible for the range of Hs / As ≤ 122. On the other hand, while there is no existing certification for the range of Hs / As > 197, the high-strength, thin-walled fire-resistant coated beams targeted in this example are included in this range. In other words, based on Figure 4, although a coating thickness of 80 mm or more is required, the high-strength, thin-walled fire-resistant coated beams also have high residual strength at high temperatures, so a coating thickness of 80 mm or less is possible. Therefore, in the example, even if the web width-thickness ratio (H-2 × t2) / t1 is larger than in the comparative case, the coating thickness can be equal to or less than that of the comparative case.

[0041] Furthermore, the coating thickness of the experimental case is similar to that of the comparative case of box-applied and direct-applied fire-resistant coatings with a 1-hour fire resistance time, the comparative case of box-applied and direct-applied fire-resistant coatings with a 3-hour fire resistance time, and the comparative case of direct-applied fire-resistant coatings with a 2-hour fire resistance time. That is, even though the web width-thickness ratio (H-2 × t2) / t1 of the experimental case is larger than that of the comparative cases, the coating thickness can be made equal to or less than that of the comparative cases under the same fire resistance time and the same coating form (box-applied or direct-applied).

[0042] In addition, in the above examples, the certified specifications for box- or direct-applied fire-resistant coating materials are used as comparative cases, as shown in Table 2. However, in the practical cases, regardless of the coating method of the fire-resistant coating material, under the same fire resistance time, same coating method, etc., the coating thickness can be made equal to or less than the certified specifications. In other words, the fire-resistant coating certification specifications for spraying rock wool onto beams are 25 mm for a one-hour fire resistance time, 45 mm for a two-hour fire resistance time, and 60 mm for a three-hour fire resistance time, regardless of the cross-sectional dimensions of the beam (H-shaped steel). However, in the practical case, under the same fire resistance time conditions, the high-strength, thin-walled fire-resistant coated beams have higher residual strength at high temperatures than the beams used in previous certifications, so as with the practical case in Table 2 above, the coating thickness can be made equal to or less than the previous certification specifications.

[0043] The above describes an embodiment of the design method for fire-resistant coated beams according to the present invention, but the present invention is not limited to the above embodiment and can be modified as appropriate within the scope of the spirit of the present invention.

[0044] For example, in the above-described embodiment, it is sufficient that the web width-thickness ratio (H-2 × t2) / t1 is set to 100 or more and the entire exposed surface of the beam 2 is covered with the fire-resistant covering material 3. However, the upper limit of the web width-thickness ratio (H-2 × t2) / t1 and the heating circumference ratio Hs / As (m -1 ), the range of the coating thickness, etc. is not limited to the above-described embodiment.

[0045] That is, the web width-thickness ratio (H-2×t2) / t1 is not limited to 160 or less as in the above embodiment.

[0046] In addition, as in the above embodiment, the heating circumference ratio Hs / As (m -1 ) is not limited to being in the range of 228 to 496.

[0047] Furthermore, as in the above embodiment, the heating perimeter ratio Hs / As (m -1 ) is not limited to satisfying the range of 228 to 394 in the case of box pasting, and 272 to 496 in the case of direct pasting.

[0048] Furthermore, the coating thickness of the fire-resistant coating material 3 is not limited to less than 20 mm as in the above embodiment.

[0049] In addition, the components in the above-described embodiments can be replaced with well-known components as appropriate, without departing from the spirit of the present invention. [Explanation of symbols]

[0050] 1 Fireproof coated beam 2 Beam material (H-shaped steel beam) 3 Fireproof coating 10 Concrete slab (floor slab) 21 Upper flange 22 Lower flange 23 Web

Claims

1. In an H-shaped steel beam that has an upper flange, a lower flange, and a web and supports a floor slab from below, the web height (beam height H-2 × flange thickness t ２ ) (mm) and the thickness t of the web １ The web width-thickness ratio (H-2×t ２ ) / t １ is set to 100 or more, The upper flange, the lower flange, and the entire exposed surface of the web are covered with a fire-resistant coating material, and the yield strength of the H-shaped steel beam is set to 440 N / mm ２ That is all, The fire-resistant covering material is provided in a box-like manner on the H-shaped steel beam except for the upper surface of the upper flange, The box liner has a pair of vertical surface portions that are arranged at a position connecting the ends of the upper flange and the lower flange and correspond to the length of the beam structure, and a horizontal surface portion that is arranged along the lower surface of the lower flange and is connected to the lower end of the vertical surface portions, and is provided with a heating perimeter consisting of the pair of vertical surface portions and the horizontal surface portions, The thickness of the fire-resistant coating material is It has the same moment of inertia as the H-shaped steel beam and a yield strength of 235 N / mm ２ In H-shaped steel beams with a web width-thickness ratio of 100 or more, A method for designing fire-resistant coated beams, characterized in that the thickness is set to 10 mm or more and 55 mm or less for a 1-hour fire resistance specification, 20 mm or more and 115 mm or less for a 2-hour fire resistance specification, or 40 mm or more and 130 mm or less for a 3-hour fire resistance specification.

2. In an H-shaped steel beam that has an upper flange, a lower flange, and a web and supports a floor slab from below, the web height (beam height H-2 × flange thickness t ２ ) (mm) and the thickness t of the web １ The web width-thickness ratio (H-2×t ２ ) / t １ is set to 100 or more, The upper flange, the lower flange, and the entire exposed surface of the web are covered with a fire-resistant coating material, and the yield strength of the H-shaped steel beam is set to 440 N / mm ２ That is all, The fire-resistant covering material is directly attached to the H-shaped steel beam except for the upper surface of the upper flange, The direct attachment has a pair of vertical surface portions arranged along both side surfaces of the web, and horizontal surface portions arranged along the lower surface of the upper flange and the upper and lower surfaces of the lower flange, and is provided with a heating perimeter that covers the pair of vertical surface portions and the horizontal surface portions, The thickness of the fire-resistant coating material is It has the same moment of inertia as the H-shaped steel beam and a yield strength of 235 N / mm ２ In H-shaped steel beams with a web width-thickness ratio of 100 or more, A method for designing fire-resistant coated beams, characterized in that the thickness is set to 10 mm or more and 60 mm or less for a 1-hour fire resistance specification, 25 mm or more and 120 mm or less for a 2-hour fire resistance specification, or 45 mm or more and 135 mm or less for a 3-hour fire resistance specification.

3. In an H-shaped steel beam that has an upper flange, a lower flange, and a web and supports a floor slab from below, the web height (beam height H-2 × flange thickness t ２ ) (mm) and the thickness t of the web １ The web width-thickness ratio (H-2×t ２ ) / t １ is set to 100 or more, The upper flange, the lower flange, and the entire exposed surface of the web are covered with a fire-resistant coating material by spraying rock wool, and the yield strength of the H-shaped steel beam is increased to 440 N / mm ２ That is all, The fire-resistant covering material covers the H-shaped steel beam except for the upper surface of the upper flange, The rock wool spraying has a pair of vertical surface portions arranged along both side surfaces of the web, and horizontal surface portions arranged along the lower surface of the upper flange and the upper and lower surfaces of the lower flange, and is provided with a heating perimeter that covers the pair of vertical surface portions and the horizontal surface portions, The thickness of the fire-resistant coating material is It has the same moment of inertia as the H-shaped steel beam and a yield strength of 235 N / mm ２ In H-shaped steel beams with a web width-thickness ratio of 100 or more, A method for designing fire-resistant coated beams, characterized in that the thickness is set to 10 mm or more and 45 mm or less for a 1-hour fire resistance specification, 20 mm or more and 70 mm or less for a 2-hour fire resistance specification, or 30 mm or more and 90 mm or less for a 3-hour fire resistance specification.

4. The web width-thickness ratio (H-2×t ２ ) / t １ The design method for a fire-resistant covered beam according to any one of claims 1 to 3, characterized in that is set in the range of 100 to 160.

5. The heating circumference Hs (mm) and cross-sectional area As (mm ２ ) and the heating perimeter ratio Hs / As (m －１ 5. The design method for a fire-resistant coated beam according to claim 1, wherein the value of the cross section of the beam is in the range of 228 to 496.

6. The heating circumference ratio Hs / As(m －１ )teeth, In the case of a box, the range is 228 to 394. The design method for a fire-resistant coated beam according to claim 5, characterized in that the range of 272 to 496 is satisfied in the case of direct attachment.

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