Fireproof beam, floor structure, and fireproof coating material construction method

Abstract

To provide a fireproof beam which prevents a covering material from falling off during construction and suppresses a temperature rise of a lower flange during a fire.SOLUTION: A fireproof beam 15 includes a steel beam 16 having an upper flange 17, a lower flange 18, and a web 19 joined to the upper flange and the lower flange, a lower covering material 21 made of a dry fireproof covering material and covering at least a portion of the lower flange, an upper middle covering material 36 made of at least one of a dry fireproof covering material and a wet fireproof covering material and covering at least a portion of the upper flange and the web, and an air layer 41 formed between the lower flange and the lower covering material.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a fireproof beam, a floor structure, and a method for installing a fireproof covering material. [Background technology]

[0002] Conventionally, in floor structures including a floor slab and beams supporting the floor slab from below, the beams have been covered with a covering material made of a fire-resistant covering material to increase the fire resistance of the beams (see, for example, Patent Documents 1 to 4). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 07-40824 [Patent Document 2] JP 2016-211356 A [Patent Document 3] JP 2013-227752 A [Patent Document 4] Japanese Unexamined Patent Publication No. 1754 / 1983 Summary of the Invention [Problem to be solved by the invention]

[0004] For example, if the fire-resistant coating material is composed of a wet-type fire-resistant coating material made by drying a binder such as inorganic fibers and cement, there is a risk that the applied fire-resistant coating material (coating material) will fall off the beam before it dries. As a result of the inventors' investigation, it was found that the falling off of the fire-resistant covering material mainly occurs from the bottom flange of the beam. In addition, it is desirable for the fire-resistant covering material to further suppress the temperature rise of the bottom flange during a fire. In addition, the cross-sectional dimensions of the bottom flanges of the multiple beams may differ from one another. Even in such a case, it is desirable to easily cover at least a portion of the bottom flange with the covering material while preventing the covering material from falling off during construction.

[0005] The first object of the present invention has been made in consideration of these problems, and aims to provide a fire-resistant beam that prevents the covering material from falling off during installation while suppressing the temperature rise of the lower flange in the event of a fire, and a floor structure equipped with this fire-resistant beam. In addition, a second object of the present invention is to provide a method for installing a fire-resistant coating material that can easily cover at least a portion of the lower flange with the coating material while preventing the coating material from falling off during installation, even when the cross-sectional dimensions of the lower flanges of multiple beams are different from one another. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention proposes the following means. (1) Aspect 1 of the present invention is a fire-resistant beam comprising a steel beam having an upper flange, a lower flange, and a web joined to the upper flange and the lower flange, respectively; a lower covering material made of a dry fire-resistant covering material and covering at least a portion of the lower flange; an upper / middle covering material made of at least one of a dry fire-resistant covering material and a wet fire-resistant covering material and covering at least a portion of the upper flange and the web; and an air layer formed between the lower flange and the lower covering material.

[0007] In this invention, as a result of extensive research by the inventors, at least a portion of the bottom flange of the beam, which is most likely to fall off, is covered with a lower covering material made of a dry fire-resistant covering material that does not need to be dried during construction. This increases the fire resistance of the bottom flange and prevents the lower covering material from falling off during construction. And, because at least a portion of the top flange and web is covered with an upper / middle covering material made of at least one of a dry fire-resistant covering material and a wet fire-resistant covering material, the fire resistance of at least a portion of the top flange and web can be increased. Furthermore, as a result of intensive research, the inventors have found that by forming an air layer between the lower flange and the lower covering material, the temperature of the lower flange is less likely to rise in the event of a fire. Therefore, it is possible to suppress the temperature rise of the lower flange in the event of a fire.

[0008] (2) In the second aspect of the present invention, a housing portion for housing the lower flange is formed in the lower covering material, and the vertical length of the housing portion is h a (mm) satisfies formula (1), and the length b of the beam in the width direction in the housing portion a The fireproof beam may be the one described in (1), in which (mm) satisfies formula (2). However, t f is the thickness of the lower flange (mm), and B is the width of the lower flange (mm). 1.1t f ≦h a ≦1.75t f (1) B≦b a ≦1.25B (2) In this invention, when there is a gap between the lower flange and the lower covering material in both the vertical and width directions and formulas (1) and (2) are satisfied, the temperature rise of the lower flange in the event of a fire can be more reliably prevented.

[0009] (3) In the third aspect of the present invention, the lower covering material is formed with a receiving portion for receiving the lower flange, and the lower covering material contacts the lower flange from both sides in the width direction of the beam, and the length h of the receiving portion in the vertical direction is a The fireproof beam may be the one described in (1), in which (mm) satisfies formula (3). However, t f is the thickness of the lower flange (mm). 1.1t f ≦h a ≦3t f (3) In this invention, when there is a gap between the lower flange and the lower covering material in the vertical direction relative to the lower flange, the temperature of the lower flange can be more reliably prevented from rising in the event of a fire.

[0010] (4) A fourth aspect of the present invention may be a fire-resistant beam described in any one of (1) to (3), wherein the lower covering material has a first covering piece and a second covering piece connected to the first covering piece by a connection part formed by engagement or fitting. In the present invention, the first covering piece and the second covering piece can be detachably connected by a connection part that is formed by engagement or fitting.

[0011] (5) Aspect 5 of the present invention may be a fire-resistant beam described in any one of (1) to (4), having a first lower covering material and a second lower covering material as the lower covering material, and the longitudinal end of the beam in the first lower covering material is positioned within the second lower covering material. In this invention, for example, the first lower covering material and the second lower covering material can be connected without placing a joint material such as cement between the first lower covering material and the second lower covering material in the longitudinal direction.

[0012] (6) A sixth aspect of the present invention may be a fire-resistant beam described in any one of (1) to (5), in which the upper and middle covering material is made of the wet fire-resistant covering material, is provided on the upper surface of the lower covering material, and has an uneven portion or an indicator indicating the thickness at which the wet fire-resistant covering material is provided. In this invention, for example, the thickness of the wet fire-resistant coating material required when applying the wet fire-resistant coating material is indicated by an uneven portion or an indicator, so that the wet fire-resistant coating material can be applied efficiently.

[0013] (7) A seventh aspect of the present invention is a floor structure comprising a floor slab and a fire-resistant beam described in any one of (1) to (6) arranged below the floor slab and having an upper flange joined to the floor slab. In this invention, a floor structure can be constructed using fire-resistant beams that prevent the covering material from falling off during construction while suppressing the temperature rise of the lower flange in the event of a fire.

[0014] (8) Aspect 8 of the present invention is a method for installing a fire-resistant coating material, in which when a first beam and a second beam are defined as steel beams having an upper flange, a lower flange, and webs joined to the upper flange and the lower flange, and the cross-sectional dimensions of the lower flanges perpendicular to at least the longitudinal direction of the first beam and the second beam are different from each other, the lower flange of the first beam and at least a portion of the lower flange of the second beam are covered with a lower coating material made of a dry fire-resistant coating material and having the same cross-sectional dimensions perpendicular to the longitudinal direction, and at least a portion of the upper flange and the web of the first beam and at least a portion of the upper flange and the web of the second beam are covered with an upper / middle coating material made of at least one of a dry fire-resistant coating material and a wet fire-resistant coating material.

[0015] In this invention, as a result of extensive research by the inventors, at least a portion of the bottom flanges of the first and second beams, which are most likely to fall off, is covered with a lower covering material made of a dry fire-resistant covering material that does not need to be dried during construction. This increases the fire resistance of the bottom flanges and prevents the lower covering material from falling off during construction. And, because at least a portion of the top flanges and webs of the first and second beams are covered with an upper / middle covering material made of at least one of a dry fire-resistant covering material and a wet fire-resistant covering material, the fire resistance of at least a portion of the top flanges and webs can be increased. In addition, at least a portion of the bottom flanges of the first beam and the second beam, which have different cross-sectional dimensions, are covered with lower covering materials that are made of dry fire-resistant covering materials and have the same cross-sectional dimensions perpendicular to the longitudinal direction. This makes it possible to easily cover at least a portion of both bottom flanges with the lower covering material by using a common lower covering material to cover both bottom flanges. Effect of the Invention

[0016] In the fire-resistant beam and floor structure of the present invention, the covering material can be prevented from falling off during construction, while suppressing the temperature rise of the lower flange during a fire. Furthermore, in the construction method of the fire-resistant covering material of the present invention, even if the cross-sectional dimensions of the lower flanges of multiple beams are different from each other, the covering material can be easily used to cover at least a portion of the lower flange with the covering material while preventing the covering material from falling off during construction. [Brief description of the drawings]

[0017] [Figure 1] FIG. 1 is a cross-sectional view showing a floor structure according to a first embodiment of the present invention as viewed from the front. [Diagram 2] FIG. [Diagram 3] FIG. 4 is a cross-sectional view illustrating a construction method for the floor structure. [Figure 4] FIG. 4 is a cross-sectional view illustrating a construction method for the floor structure. [Diagram 5] FIG. 4 is a cross-sectional view illustrating a construction method for the floor structure. [Figure 6] FIG. 13 is a diagram showing an analytical model of the floor structure. [Figure 7] FIG. 1 shows the standard heating curve of ISO-834. [Figure 8] FIG. 13 is a graph showing changes in each temperature with respect to heating time. [Figure 9] FIG. 13 is a graph showing the change in beam temperature versus coefficients kh and kb. [Figure 10] 1 is a cross-sectional view of a main part of a fireproof beam according to a first modified example of the first embodiment of the present invention, seen from the front. FIG. [Figure 11] 13 is a cross-sectional view of a main part of a fireproof beam according to a second modified example of the first embodiment of the present invention, seen from the front. FIG. [Figure 12] 13 is a cross-sectional view of a main part of a fireproof beam according to a third modified example of the first embodiment of the present invention, seen from the front. FIG. [Figure 13] FIG. 11 is a cross-sectional front view of a fireproof beam according to a fourth modified example of the first embodiment of the present invention. [Figure 14] FIG. 13 is a cutaway perspective view of a fireproof beam according to a fifth modified example of the first embodiment of the present invention. [Figure 15]13 is a cross-sectional view of a main part of a fireproof beam according to a sixth modified example of the first embodiment of the present invention, seen from the front. FIG. [Figure 16] 13 is a cross-sectional view of a main part of a fireproof beam according to a seventh modified example of the first embodiment of the present invention, seen from the front. FIG. [Figure 17] FIG. 4 is a side view of a floor structure according to a second embodiment of the present invention. [Figure 18] 18 is a cross-sectional view taken along line A2-A2 in FIG. 17. [Figure 19] 13 is a cross-sectional front view of a second beam used in a method for installing a fire-resistant covering material according to a third embodiment of the present invention. FIG. [Figure 20] FIG. 11 is a cross-sectional view illustrating a construction method for a floor structure in a first modified example of the first embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] (First embodiment) Hereinafter, a first embodiment of a fireproof beam and a floor structure according to the present invention will be described with reference to FIGS. 1 to 16 and 20. FIG.

[0019] [1.1. Floor structure configuration] As shown in Figs. 1 and 2, the floor structure 1 of this embodiment includes a floor slab 10 and a fire-resistant beam 15 of this embodiment. The floor slab 10 is formed in a flat plate shape with its thickness direction aligned with the vertical direction Z. Here, "A is aligned with B" means that the angle between A and B is 30 degrees or less. It is more preferable that this angle is 15 degrees or less. For example, "A" corresponds to the thickness direction of the floor slab 10, and "B" corresponds to the vertical direction Z. The floor slab 10 is made of concrete, reinforced concrete, or the like.

[0020] The fire-resistant beam 15 comprises a steel beam 16, a plurality of lower cladding materials 21, upper and middle cladding materials 36, and an air layer 41. In this embodiment, the beam 16 is formed of an H-shaped steel. The beam 16 extends in a longitudinal direction X along the lower surface of the floor slab 10, i.e., along the horizontal plane. Hereinafter, a direction perpendicular to the longitudinal direction X and the vertical direction Z is referred to as a width direction Y. The width direction Y is the width direction of the beam 16.

[0021] The beam 16 has an upper flange 17 , a lower flange 18 , and a web 19 . The upper flange 17, the lower flange 18, and the web 19 are each formed in a flat plate shape. The upper flange 17 and the lower flange 18 are arranged to face each other in the up-down direction Z. The upper flange 17 is arranged higher than the lower flange 18. The web 19 is arranged between the upper flange 17 and the lower flange 18, and is joined to the center of the upper flange 17 in the width direction Y and the center of the lower flange 18 in the width direction Y, respectively. A stud (fastening material) 18a is fixed to the upper surface of the lower flange 18. The fastening material may be a screw, a welded pin, or the like. The studs 18a are formed in a rod shape and extend along the up-down direction Z. The studs 18a are disposed on the upper surface of the lower flange 18 on a first side Y1 in the width direction Y relative to the web 19 (hereinafter simply referred to as the first side Y1) and on a second side Y2 opposite the first side Y1 in the width direction Y relative to the web 19 (hereinafter simply referred to as the second side Y2).

[0022] The beam 16 is disposed below the floor slab 10. The upper flange 17 is joined to the floor slab 10 by studs or the like (not shown).

[0023] 1, hereinafter, a plane that passes through the center of the web 19 in the width direction Y and is perpendicular to the width direction Y is defined as a reference plane S1. The beam 16 is symmetrical with respect to the reference plane S1.

[0024] In this embodiment, the lower covering material 21 is configured to have a rectangular cylindrical shape with a rectangular outer shape by two members (pieces). The lower covering material 21 has a first covering piece 22 and a second covering piece 32. The lower covering material 21 may be configured by one member or by three or more members. The first covering piece 22 and the second covering piece 32 each have a C-shape when viewed in the longitudinal direction X. The first covering piece 22 has a bottom wall 23A, a side wall 24A, a top wall 25A, and a connecting piece 26. The bottom wall 23A, the side wall 24A, the top wall 25A, and the connecting piece 26 are each formed in a flat plate shape.

[0025] The thickness of the bottom wall 23A, the thickness of the side wall 24A, and the thickness of the top wall 25A are equal to each other. Note that the thickness of each wall 23A, 24A, 25A may be adjusted according to the required fire resistance performance, for example, by making the bottom wall 23A thicker than the side wall 24A. The thickness of the connection piece 26 is approximately half the thickness of the bottom wall 23A. The bottom wall 23A is disposed such that its thickness direction is along the up-down direction Z. The bottom wall 23A is disposed below the lower flange 18 and on the first side Y1 of the reference plane S1. The bottom wall 23A is spaced downward from the lower flange 18. The side wall 24A protrudes upward from an end of the first side Y1 of the bottom wall 23A. The side wall 24A is disposed on the first side Y1 further than the lower flange 18. The side wall 24A is spaced from the lower flange 18 on the first side Y1.

[0026] The top wall 25A extends from the upper end of the side wall 24A toward the second side Y2. The top wall 25A contacts the lower flange 18 from above the lower flange 18. The top wall 25A contacts the web 19 from the first side Y1 of the web 19. The top wall 25A has a through hole 25aA formed therein, which penetrates the top wall 25A in the up-down direction Z. The stud 18a is disposed in the through hole 25aA.

[0027] The connection piece 26 protrudes from a lower portion of the end portion of the bottom wall 23A on the second side Y2 toward the second side Y2. The bottom wall 23A, side wall 24A, top wall 25A, and connection piece 26 of the first covering piece 22 are integrally formed from reinforced gypsum board (dry fire-resistant covering material).

[0028] The second covering piece 32 has a bottom wall 23B, a side wall 24B, a top wall 25B, and a connecting piece 27. The connecting piece 26 and the connecting piece 27 configure a connecting portion 28. The connecting portion 28 is a mechanical joint. In this embodiment, the configuration of the top wall 25A and the configuration of the top wall 25B are plane symmetrical with respect to the reference plane S1. Therefore, the configuration of the top wall 25A is indicated by adding the capital letter "A" to the number of the symbol, or the number and the lowercase English letter. The configuration of the top wall 25B corresponding to the top wall 25A is indicated by adding the capital letter "B" to the same number as the symbol of the top wall 25A, or the number and the lowercase English letter. In this way, duplicated explanations are omitted. For example, the through-hole 25aA in the top wall 25A and the through-hole 25aB in the top wall 25B have the same configuration.

[0029] The thickness of the connection piece 27 is about half the thickness of the bottom wall 23B. The connection piece 27 protrudes toward the first side Y1 from an upper portion of the end of the first side Y1 of the bottom wall 23B. The connection piece 27 contacts (engages) with the connection piece 26 of the first covering piece 22 from above the connection piece 26. The bottom wall 23B, the side wall 24B, the top wall 25B, and the connection piece 27 of the second covering piece 32 are integrally formed from a reinforced gypsum board or the like. The second covering piece 32 is connected to the first covering piece 22 by a connecting portion 28 formed by engagement. The first covering piece 22 and the second covering piece 32 of the lower covering material 21 cover the entire lower flange 18. The first covering piece 22 and the second covering piece 32 sandwich the lower flange 18 in the width direction Y. Alternatively, the bottom wall 23A, the side wall 24A, and the top wall 25A may be defined as a first covering piece, and the bottom wall 23B, the side wall 24B, and the top wall 25B may be defined as a second covering piece.

[0030] The lower covering material 21 is formed with an accommodation portion 21a that accommodates the lower flange 18 of the beam 16. The accommodation portion 21a is an internal space of the lower covering material 21. When viewed in the longitudinal direction X, the accommodation portion 21a has a rectangular shape.

[0031] For example, the upper-middle covering material 36 is made of sprayed rock wool (wet fire-resistant covering material). Sprayed rock wool is a material whose main components are inorganic fibers such as rock wool and a binder such as cement. The upper-middle covering material 36 covers the upper flange 17 and a part of the web 19 other than the upper surface of the upper flange 17. The upper-middle covering material 36 contacts the ends of the top walls 25A, 25B of the lower covering material 21 on the reference plane S1 side in the width direction Y from above these ends. The upper and middle covering material may be composed of a dry fire-resistant covering material, or may be composed of both a dry fire-resistant covering material and a wet fire-resistant covering material.

[0032] The air layer 41 is formed between the lower flange 18 and the lower covering material 21. More specifically, the air layer 41 is formed below the lower flange 18, on the first side Y1, and on the second side Y2.

[0033] 2, in the fireproof beam 15, a plurality of lower covering materials 21 are arranged side by side in the longitudinal direction X. A fire-resistant joint material 43 is arranged between (in the joints of) the lower covering materials 21 adjacent to each other in the longitudinal direction X. For example, the joint material 43 is made of a material obtained by mixing an inorganic material with an organic binder. The number of lower cladding materials 21 provided on the fireproof beam 15 may be one.

[0034] [1.2. Floor construction method] Next, a method for constructing the floor structure 1 configured as above will be described, with emphasis on a method for applying the covering materials 21, 36. The following description will begin with a state in which the floor slab 10 is supported on the beam 16, as shown in Fig. 3. Studs 18a are fixed to the bottom flange 18 of the beam 16. The studs 18a are fixed to the bottom flange 18 in a factory where the beam 16 is manufactured. First, at the construction site, the first covering piece 22 is attached to the bottom flange 18 of the beam 16 as shown in Fig. 4. At this time, the stud 18a is passed through the through hole 25aA of the first covering piece 22.

[0035] Next, as shown in Fig. 5, the second covering piece 32 is attached to the bottom flange 18 of the beam 16. At this time, the stud 18a is passed through the through hole 25aB of the second covering piece 32. The connection piece 27 of the second covering piece 32 is placed on the connection piece 26 of the first covering piece 22. The first covering piece 22 and the second covering piece 32 constitute the lower covering material 21. A joint material 43 is disposed between the lower covering materials 21 adjacent to each other in the longitudinal direction X. Next, as shown in FIG. 1, rock wool or the like is sprayed onto the upper flange 17 and web 19 of the beam 16 and then dried to form the upper and middle covering material 36. By carrying out the above steps, the floor structure 1 is constructed.

[0036] The floor structure may be constructed as shown in FIG. That is, a first covering piece 22 without a through hole 25aA is attached to a beam 16 to which a stud 18a is not fixed. This first covering piece 22 is fixed to the bottom flange 18 of the beam 16 with a screw 90. At this time, a through hole 25aA is formed in the first covering piece 22. The screw 90 passes through the through hole 25aA of the first covering piece 22 and fixes it to the bottom flange 18. Next, in the same manner as the first covering piece 22, the second covering piece 32 in which the through hole 25aB is not formed is fixed to the lower flange . By carrying out the above steps, the floor structure of the modified example is constructed.

[0037] [1.3. Consideration of fire resistance of floor structure] [1.3.1.Analysis conditions] The effect of the air space 41 of the fire-resistant beam 15 on the fire resistance was examined by performing a heat conduction analysis of the floor structure 1. Here, the dimensions of the fire beam 15 are defined as shown in FIG. The thickness of the lower flange 18 (length in the vertical direction Z) is t fThe width of the lower flange 18 (length in the width direction Y) is defined as B (mm). The length of the storage portion 21a in the vertical direction Z is defined as h a The length of the storage portion 21a in the width direction Y is defined as b a (mm). Length h a and length b a is the inside dimension of the lower cladding material 21.

[0038] Fig. 6 shows an analytical model of the floor structure 1. Note that in Fig. 6, the mesh density of the analytical model is shown coarser than the actual density. Table 1 shows the cross-sectional shapes and materials used in the analysis.

[0039] [Table 1]

[0040] As shown in Table 1, the cross-sectional shape of the beam 16 perpendicular to the longitudinal direction X was H-400x200x8x13 as specified in JIS G 3192. However, the fillet parts formed at the connection parts of the flanges 17, 18 and the web 19 in the beam 16 were ignored. The lower covering material 21 was made of reinforced gypsum board with a thickness of 21 mm. The upper and middle covering material 36 was made of sprayed rock wool with a thickness of 25 mm.

[0041] In this analysis, we assumed a one-hour fire-resistant beam, with the thickness of the lower cladding material 21 set to 21 mm (fire-resistant construction certification number: FP060BM-0258) and the thickness of the upper and middle cladding material 36 set to 25 mm (fire-resistant construction certification number: FP060BM-9408). The floor slab 10 is a concrete slab, and the width and thickness of the floor slab 10 are 1000 mm and 150 mm, respectively. The thermal properties of the steel frame and concrete are based on Eurocode 2, 3 (see [1.4] 1), 2), and the thermal properties of the reinforced gypsum board and sprayed rock wool are based on the Fire Resistance Guidebook for Structural Materials (see [1.4] 3). The moisture content of the concrete, reinforced gypsum board, and sprayed rock wool was all 5.0%.

[0042] The heating history of the floor structure 1 was based on the standard heating curve of ISO-834 (see [1.4] 4) shown in Figure 7. Specifically, as shown in Figure 6, the underside 10a of the floor slab 10, the surface 21b exposed to the outside of the lower cladding material 21, and the surface 36a exposed to the outside of the upper and middle cladding material 36 were heated based on the standard heating curve. In Figure 6, the underside 10a and the surfaces 21b and 36a are indicated by thick solid lines. The heating temperature T (°C) according to the standard heating curve is defined by equation (11) relative to the heating time t (min). T=345log 10 (8t+1)+20 ··(11) The analysis was performed using SAFIR, a general-purpose FEM analysis software. Beam 16 was designed for a one-hour fire resistance specification.

[0043] Table 2 shows a list of analysis models.

[0044] [Table 2]

[0045] The alphabetical characters in Table 2 are the case names of the analytical models. In other words, there are 16 types of analytical models, from analytical model a to analytical model p. The analysis parameters are the length h of the storage portion 21a a and length b a It was decided. According to the formula (14), the coefficient k of the inside dimension of the lower cladding material 21 in the vertical direction Z is h (-) is defined. From the formula (15), the coefficient k b (-) is specified. k h =h a / t f (14) k b =b a / B ··(15)

[0046] In Table 2, for example, in analytical model j, coefficient k his 1.10(h a =1.10t f ) and the coefficient k b is 1.25(b a =1.25B). In the analysis model a, the air layer 41 is not formed between the lower flange 18 of the beam 16 and the lower covering material 21, and the specifications correspond to those of Patent Document 1 (comparative example).

[0047] [1.3.2. Analysis results] The temperature of the beam 16 obtained by analysis will now be described. In Fig. 6, the temperature sampling points of the beam 16 are shown as points T1, T2, and T3. Points T1, T2, and T3 are three points at both ends and the center in the width direction Y on the underside of the lower flange 18. In this embodiment, the average value of the temperatures of the lower flange 18 at these three points T1, T2, and T3 is taken as the beam temperature, and this beam temperature is used for the study. Figure 8 shows the beam temperature history in analytical model a. The temperature at point T1 shown by the solid line overlaps with the temperature at point T3 shown by the dashed line. In this embodiment, since the target is a beam with one-hour fire resistance, the beam temperature indicated by circle C1 60 minutes after the start of heating (heating time 60 minutes) is used.

[0048] Table 3 shows the beam temperatures obtained for each analysis model.

[0049] [Table 3]

[0050] Table 3 shows the beam temperature etc. at 60 minutes after the start of heating, as shown in Figure 8. In addition, the analytical model a (coefficient k b is 1.00 and coefficient k h The case of the analysis model in which the beam temperature is higher than that of analysis model a is hatched, with a standard value of 1.00. From Table 3, when the air layer 41 is not formed in the width direction Y with respect to the lower flange 18 (coefficient k b is 1.00), an air layer 41 is formed below the lower flange 18 (coefficient kh is 1.10 or more), the air layer 41 is not formed (coefficient k h is 1.00), 1.1 (1.10) ≦ k h < 3.0 (3.00) resulted in lower beam temperature. The result of this example is the coefficient k b When is 1.00, the coefficient k h is changed from 1.00 to 3.00, as shown by line L5 in FIG.

[0051] On the other hand, when an air layer 41 is formed in the width direction Y with respect to the lower flange 18 (coefficient k b is 1.25 or more), the air layer 41 is not formed in this portion (coefficient k b The beam temperature was higher than that of the beam with a coefficient of k = 1.00. b As the temperature increases, the difference in the beam temperature for analytical model a increases. This result is taken as coefficient k h When is 1.00, the coefficient k b is changed from 1.00 to 2.00, as shown by line L6 in FIG. In the above trend, the coefficient k h 1.1(1.10)≦k h <1.75, and the coefficient k b When the length h of the housing part 21a in the vertical direction Z is set to 1.25, the beam temperature is lower than that of the analysis model a. a satisfies formula (18), and the length b a When equation (19) is satisfied (see the range indicated by the solid line L1 in Table 3), the beam temperature is lower than that of analytical model a. 1.1t f (1.10t f )≦h a ≦1.75t f (18) B(1.00B)≦b a ≦1.25B (19)

[0052] In addition, from the range of equation (18) and equation (19), the coefficient k b is 1.25 and coefficient k hThe case where is 1.75 may be excluded.

[0053] In addition, the lower covering material 21 contacts the lower flange 18 from both sides in the width direction Y, and the length h of the storage portion 21a in the vertical direction Z is a When equation (20) is satisfied (see the range indicated by the dashed line L2 in Table 3), the beam temperature is lower than that of analytical model a. 1.1t f (1.10t f )≦h a ≦3t f (3.00t f ) ··(20)

[0054] [1.4. Literature] 1)Eurocode 2:Design of concrete structures Part 1-2:General rules- Structural fire design,prEN 1992-1-2,2004 2)Eurocode 3:Design of steel structures Part1-2:General rules- Structural fire design,prEN 1993-1-2,2005 3) Architectural Institute of Japan: Guidebook for Fire Resistance Performance of Structural Materials, Maruzen Publishing, 2017 4)ISO 834-1, Fire-resistance tests -Elements of building construction- Part 1: General requirements, 1999.9

[0055] 1.5. Effects of this embodiment As described above, in the fire-resistant beam 15 of this embodiment, as a result of intensive study by the inventors, the bottom flange 18 of the beam 16, which is most likely to fall off, is covered with the lower covering material 21 made of a dry fire-resistant covering material that does not need to be dried during construction. This improves the fire resistance of the bottom flange 18 and prevents the lower covering material 21 from falling off during construction. In addition, the upper flange 17 and part of the web 19 are covered with the upper-middle covering material 36 made of a dry fire-resistant covering material, so that the fire resistance of the upper flange 17 and part of the web 19 can be improved. Furthermore, as a result of extensive research, the inventors have found that the temperature (beam temperature) of the lower flange 18 is less likely to rise during a fire by forming an air layer 41 between the lower flange 18 and the lower covering material 21. Therefore, it is possible to suppress a rise in the temperature of the lower flange 18 during a fire.

[0056] The lower covering member 21 is formed with a storage portion 21a, and the length h a satisfies formula (18), and the length b a may satisfy formula (19). In this case, there is a gap between the lower flange 18 and the lower covering material 21 on both sides below the lower flange 18 and in the width direction Y, and the temperature of the lower flange 18 can be more reliably prevented from rising in the event of a fire. The lower covering material 21 is formed with a storage portion 21a. The lower covering material 21 contacts the lower flange 18 from both sides in the width direction Y. The length h of the storage portion 21a in the vertical direction Z is a may satisfy formula (20). In this case, the temperature rise of the lower flange 18 in the event of a fire can be more reliably suppressed.

[0057] The lower covering material 21 has a first covering piece 22 and a second covering piece 32 that are connected to each other by a connecting portion 28. Therefore, the first covering piece 22 and the second covering piece 32 can be detachably connected by the connecting portion 28 through engagement. In addition, in the floor structure 1 of this embodiment, the floor structure 1 can be constructed using fire-resistant beams 15 that prevent the lower covering material 21 from falling off during construction while suppressing the temperature rise of the lower flange 18 in the event of a fire.

[0058] [1.6. Modifications of fire-resistant beams] The configuration of the fire-resistant beam 15 of this embodiment can be modified in various ways as described below. As in the first modified fireproof beam 15a shown in Fig. 10, in each configuration of the fireproof beam 15, a lower covering material 51 may be provided instead of the lower covering material 21. The lower covering material 51 has a first covering piece 52 and a second covering piece 57. The first covering piece 52 has connecting pieces 53 and 54 instead of the connecting piece 26 in each configuration of the first covering piece 22. The connecting pieces 53 and 54 are each formed in a flat plate shape. The thickness of the connecting pieces 53 and 54 is about one-third the thickness of the bottom wall 23A. The connection piece 53 protrudes toward the second side Y2 from an upper end of the end of the second side Y2 of the bottom wall 23A. The connection piece 54 protrudes toward the second side Y2 from a lower end of the end of the second side Y2 of the bottom wall 23A. A gap is formed between the connection piece 53 and the connection piece 54.

[0059] The second covering piece 57 has a connecting piece 58 instead of the connecting piece 27 in each configuration of the second covering piece 32. The connecting pieces 53, 54 and the connecting piece 58 of the first covering piece 52 form a connecting portion 59. The connection piece 58 is formed in a flat plate shape. The thickness of the connection piece 58 is about one third of the thickness of the bottom wall 23B. The connection piece 58 protrudes from a middle part in the up-down direction Z at an end part of the first side Y1 of the bottom wall 23B toward the first side Y1. The connection piece 58 is disposed between the connection piece 53 and the connection piece 54 of the first covering piece 52. The connection portion 59 is a connection portion formed by fitting the connection pieces 53 and 54 and the connection piece 58 together.

[0060] 11, in each configuration of the fireproof beam 15, a lower covering material 61 may be provided instead of the lower covering material 21. The lower covering material 61 has a first covering piece 62 and a second covering piece 67. The first covering piece 62 has connecting pieces 63 and 64 instead of the connecting piece 26 in each configuration of the first covering piece 22 . The connection piece 63 protrudes toward the second side Y2 from an upper end of the end of the bottom wall 23A on the second side Y2. The connection piece 64 protrudes downward from the end of the connection piece 63 on the second side Y2. The second covering piece 67 has connecting pieces 68 and 69 instead of the connecting piece 27 in each configuration of the second covering piece 32. The connecting pieces 63 and 64 and the connecting pieces 68 and 69 of the first covering piece 62 form a connecting portion 70. The connection piece 68 protrudes toward the first side Y1 from a lower end of the end of the first side Y1 of the bottom wall 23B. The connection piece 69 protrudes upward from the end of the connection piece 68 on the first side Y1. The connection pieces 64, 69 are fitted together in the width direction Y. The connection portion 70 is a connection portion formed by the connection pieces 63, 64 and the connection pieces 68, 69 being fitted together.

[0061] The fireproof beam 15a of the first modified example and the fireproof beam 15b of the second modified example configured as above can also achieve the same effects as the fireproof beam 15 of the present embodiment.

[0062] As in a fireproof beam 15c of a third modified example shown in Fig. 12, each component of the fireproof beam 15 may be provided with an adhesive portion 75 instead of the stud 18a. In the fireproof beam 15c, the through holes 25aA and 25aB are not formed in the top walls 25A and 25B. The adhesive portions 75 are adhered to the top walls 25A, 25B and the lower flanges 18 of the cover pieces 22, 32, respectively. An adhesive is used for the adhesive portion 75. The adhesive preferably has fire resistance. In addition, the fireproof beam 15c does not necessarily have to include the adhesive portion 75.

[0063] As in the fireproof beam 15d of the fourth modified example shown in Fig. 13, the through holes 25aA, 25aB may also function as the uneven portion. The through holes 25aA, 25aB are provided on the upper surface of the top walls 25A, 25B of the lower covering material 21, and are recesses recessed downward from the upper surface of the top walls 25A, 25B. The through holes 25aA, 25aB represent the thickness of the sprayed rock wool constituting the upper-middle covering material 36. That is, for example, when the rock wool is sprayed on the beam 16, the rock wool is sprayed so that the through holes 25aA, 25aB are hidden by the rock wool. The rock wool is then dried to form the upper and middle covering material 36. In the fireproof beam 15d of the fourth modified example, the thickness of the sprayed rock wool required when applying the sprayed rock wool is indicated by the through holes 25aA and 25aB, so that the application of the sprayed rock wool can be performed efficiently.

[0064] When the studs 18a in the through holes 25aA, 25aB are covered by the upper and middle covering material 36, the studs 18a become a thermal bridge, preventing heat from outside the lower covering material 21 from being transmitted to the lower flange 18 through the studs 18a. The uneven portions may be holes that do not penetrate the top walls 25A and 25B, or may be protrusions that protrude upward from the upper surfaces of the top walls 25A and 25B.

[0065] 14, in addition to each component of the fireproof beam 15, an indicator 80 may be provided. In this example, the indicator 80 is provided on the upper surface of the top walls 25A and 25B, and is a mark indicating the thickness of the sprayed rock wool constituting the upper-middle covering material 36. For example, the indicator 80 is formed with ink and extends linearly along the longitudinal direction X. The fireproof beam 15e of the fifth modified example has a plurality of indicators 80. The plurality of indicators 80 include indicators 80a, 80b, and 80c. The indicators 80a, 80b, and 80c are arranged corresponding to the distances L10, L11, and L12 from the web 19 of the beam 16. The fireproof beam 15e of the fifth modified example can also provide the same effects as the fireproof beam 15d of the fourth modified example. The indicator may be in the form of a dot or the like.

[0066] Like a fireproof beam 15f of a sixth modified example shown in FIG. 15, in each configuration of the fireproof beam 15, a beam 16a and a lower cladding material 86 may be provided instead of the beam 16 and the lower cladding material 21. In addition to the respective components of the beam 16, the beam 16a has a fillet portion 18b at a connection portion between the lower flange 18 and the web 19. For example, the fillet portion 18b is formed when the lower flange 18 and the web 19 are welded together.

[0067] The lower covering material 86 has a first covering piece 22a and a second covering piece 32a. In each configuration of the first covering piece 22a, a slope 25bA is formed on the top wall 25A. The slope 25bA is formed on a lower portion of the end face of the second side Y2 of the top wall 25A. The slope 25bA is gradually inclined toward the first side Y1 (moving away from the reference plane S1) as it extends downward. In each configuration of the second covering piece 32a, a slope 25bB is formed on the top wall 25B. The slope 25bB is formed on a lower portion of the end face of the first side Y1 of the top wall 25B. The slope 25bB is gradually inclined toward the second side Y2 (moving away from the reference plane S1) as it extends downward. In the fireproof beam 15f of the sixth modified example configured as above, the inclined surfaces 25bA, 25bB of the covering pieces 22a, 32a can prevent the covering pieces 22a, 32a from interfering with the fillet portion 18b of the beam 16a.

[0068] As in a fireproof beam 15g of a seventh modified example shown in FIG. 16, a lower covering material 91 may be provided instead of the lower covering material 86 in each configuration of the fireproof beam 15f of the sixth modified example. The lower covering material 91 has a first covering piece 22b and a second covering piece 32b. In the covering pieces 22b and 32b, the top walls 25A and 25B do not have the inclined surfaces 25bA and 25bB, and the top walls 25A and 25B are spaced apart from the web 19 and the fillet portion 18b of the beam 16a. That is, the web 19 and the fillet portion 18b are disposed in the gap between the top walls 25A and 25B. In this modified example, the lower covering material 91 does not cover a portion of the upper part of the lower flange 18, but covers the other portion (portion) of the lower flange 18. The fireproof beam 15g of the seventh modified example configured as above can achieve the same effects as the fireproof beam 15f of the sixth modified example.

[0069] Second embodiment Next, a second embodiment of the present invention will be described with reference to Figs. 1, 17, and 18. The same parts as those in the above embodiment are given the same reference numerals, and their description will be omitted. Only the differences will be described. 1, 17, and 18, the floor structure 2 of this embodiment includes a fireproof beam 95 instead of the fireproof beam 15 in each configuration of the floor structure 1. Note that FIG. 1 is a cross-sectional view of the cutting line A1-A1 in FIG. The fireproof beam 95 has a first lower cladding material (lower cladding material) 96 and a second lower cladding material (lower cladding material) 101 instead of the lower cladding material 21 in each configuration of the fireproof beam 15. In this embodiment, the studs 18a are not fixed to the beams 16.

[0070] In the first lower covering material 96, in each configuration of the lower covering material 21, the through holes 25aA, 25aB are not formed in the top walls 25A, 25B. The second lower covering material 101 has a length h a is the length of the storage section in the vertical direction Z, and the length b a is the length of the width direction Y of its own storage section. A first end of the first lower covering material 96 in the longitudinal direction X is disposed within a second lower covering material 101. A second end of the first lower covering material 96 opposite to the first end in the longitudinal direction X is disposed within another second lower covering material 101.

[0071] As described above, the fire-resistant beam 95 of this embodiment can prevent the lower covering material 21 from falling off during construction, while suppressing the temperature rise of the lower flange 18 in the event of a fire. Furthermore, the first lower covering material 96 and the second lower covering material 101 can be connected in the longitudinal direction X without placing a joint material such as cement between the first lower covering material 96 and the second lower covering material 101.

[0072] Third embodiment Next, a third embodiment of the present invention will be described with reference to Figs. 1 and 19. The same components as those in the above embodiment are given the same reference numerals, and the description thereof will be omitted. Only the differences will be described. In this embodiment, a method for applying a fire-resistant covering material (hereinafter, simply referred to as an application method) will be described. In the construction method, a first beam 16b (see FIG. 1) which is the same as the beam 16, and a second beam 106 shown in FIG. 19 are used. The second beam 106 is made of a steel frame and has an upper flange 107 , a lower flange 108 , and a web 109 .

[0073] The first beam 16b and the second beam 106 differ from each other in at least the cross-sectional dimensions perpendicular to the longitudinal direction X of the lower flanges 18, 108. In this embodiment, the width (length in the width direction Y) of the lower flange 108 is longer than the width of the lower flange 18. The thickness (length in the up-down direction Z) of the lower flange 108 and the thickness of the lower flange 18 are equal to each other. In other words, the cross-sectional area perpendicular to the longitudinal direction X of the lower flange 108 of the first beam 16b and the cross-sectional area perpendicular to the longitudinal direction X of the lower flange 108 of the second beam 106 are different from each other. The thickness of the lower flange 108 may be different from the thickness of the lower flange 18. The cross-sectional area perpendicular to the longitudinal direction X of the upper flange 17 of the first beam 16b and the cross-sectional area perpendicular to the longitudinal direction X of the upper flange 107 of the second beam 106 may be different from each other. The cross-sectional area perpendicular to the longitudinal direction X of the web 19 of the first beam 16b and the cross-sectional area perpendicular to the longitudinal direction X of the web 109 of the second beam 106 may be different from each other.

[0074] In the construction method, the bottom flange 18 of the first beam 16b is covered with a lower covering material 21, and the bottom flange 108 of the second beam 106 is covered with a lower covering material 21 different from the lower covering material 21 that covers the bottom flange 18. The lower covering material 21 covering the lower flange 18 and the lower covering material 21 covering the lower flange 108 have the same cross-sectional dimensions perpendicular to the longitudinal direction X. Next, the upper flange 17 and part of the web 19 of the first beam 16b are covered with the upper-middle covering material 36, and the upper flange 107 and part of the web 109 of the second beam 106 are covered with the upper-middle covering material 116, as shown in Fig. 19. The upper-middle covering material 116 is made of sprayed rock wool. In addition, the upper and middle covering material 36 and the upper and middle covering material 116 may be composed of a dry fire-resistant covering material, or may be composed of both a dry fire-resistant covering material and a wet fire-resistant covering material.

[0075] As described above, in the construction method of this embodiment, as a result of intensive study by the inventors, parts of the lower flanges 18, 108 of the first beam 16b and the second beam 106, which are most likely to fall off, are covered with the lower covering material 21 made of a dry fire-resistant covering material that does not need to be dried during construction. This improves the fire resistance of the lower flanges 18, 108 and prevents the lower covering material 21 from falling off during construction. Furthermore, parts of the upper flanges 17, 107 and webs 19, 109 of the first beam 16b and the second beam 106 are covered with the upper middle covering materials 36, 116, respectively, so that the fire resistance of the upper flanges 17, 107 and parts of the webs 19, 109 can be improved. Furthermore, the bottom flange 18 of the first beam 16b and the bottom flange 108 of the second beam 106, which have different cross-sectional dimensions, are covered with lower covering materials 21 made of sprayed rock wool and have the same cross-sectional dimensions perpendicular to the longitudinal direction X. Therefore, the lower covering material 21 that covers both lower flanges 18, 108 can be made common, and at least a portion of both lower flanges 18, 108 can be easily covered with the lower covering material 21.

[0076] Although the first to third embodiments of the present invention have been described above with reference to the drawings, the specific configurations are not limited to these embodiments, and the present invention also includes modifications, combinations, deletions, etc. of the configurations within the scope of the gist of the present invention. Furthermore, it goes without saying that the configurations shown in each embodiment can be used in appropriate combinations. For example, in the first to third embodiments, the beam does not have to be made of an H-shaped steel as long as it has an upper flange, a lower flange, and a web. Dry fireproof coating materials may include calcium silicate boards, cement, ALC (Autoclaved Lightweight Aerated Concrete), particle boards, and the like. The first covering piece and the second covering piece may be connected to each other by an adhesive or the like. The entire top flange 17 and web 19 may be covered with a top center covering 36 . [Explanation of symbols]

[0077] 1,2 floor structure 10 Floor slab 15,15a,15b,15c,15d,15e,15f,95 Fireproof beam 16,16a beam 16b 1st beam 17,107 Top flange 18,108 Lower flange 19,109 Web 21,51,61,86,91 Lower covering material 22,22a,22b,52,62 1st covering piece 25aA, 25aB Through hole (uneven part) 28, 59, 70 Connection part 32, 32a, 32b, 57, 67 Second covering piece 36, 116 Upper middle covering material 41 Air layer 80 Indicator 96 First lower covering material (lower covering material) 101 Second lower covering material (lower covering material) 106 Second beam Y Width direction Z Up and down direction

Claims

1. A steel beam having an upper flange, a lower flange, and a web joined to the upper flange and the lower flange, respectively; A lower covering material that is made of a dry fire-resistant covering material and covers at least a portion of the lower flange; an upper middle covering material that is made of at least one of a dry fire-resistant covering material and a wet fire-resistant covering material and covers the upper flange and at least a part of the web; an air layer formed between the lower flange and the lower covering material; A fire-resistant beam.

2. The lower covering member is formed with an accommodating portion for accommodating the lower flange, The length h of the storage section in the vertical direction ａ (mm) satisfies formula (1), The length b of the beam in the width direction in the housing portion ａ The fireproof beam according to claim 1, wherein (mm) satisfies formula (2). Here, t ｆ is the thickness (mm) of the lower flange, and B is the width (mm) of the lower flange. <h2 style=";text-align:left;direction:ltr">1415<h2 style=";text-align:left;direction:ltr"> ｆ <h2 style=";text-align:left;direction:ltr"> ≦h<h2 style=";text-align:left;direction:ltr"> ａ <h2 style=";text-align:left;direction:ltr"> ≦15555<h2 style=";text-align:left;direction:ltr"> ｆ <h2 style=";text-align:left;direction:ltr">・・(11) <h2 style=";text-align:left;direction:ltr">B≦b<h2 style=";text-align:left;direction:ltr"> ａ <h2 style=";text-align:left;direction:ltr"> ≦14255B・・(22)

3. The lower covering member is formed with an accommodating portion for accommodating the lower flange, The lower cladding material contacts the lower flange from both sides in the width direction of the beam, The length h of the storage section in the vertical direction ａ The fireproof beam according to claim 1, wherein (mm) satisfies formula (3). Here, t ｆ is the thickness of the lower flange (mm). 1.1t ｆ ≦h ａ ≦3t ｆ ・・(3)

4. The undercoat material is A first covering piece; a second covering piece connected to the first covering piece by a connection portion formed by engagement or fitting; The fire beam of claim 1 , having

5. The lower cladding material includes a first lower cladding material and a second lower cladding material, The fire-resistant beam of claim 1 , wherein the longitudinal ends of the beam in the first lower cladding are disposed within the second lower cladding.

6. The upper and middle covering material is composed of the wet fire-resistant covering material, The fire-resistant beam according to claim 1 , further comprising an uneven portion or an indicator on the upper surface of the lower covering material, which indicates the thickness at which the wet fire-resistant covering material is applied.

7. Floor slabs and A fire-resistant beam according to claim 1, which is disposed below the floor slab and the upper flange is joined to the floor slab; A floor structure comprising:

8. When a steel beam having an upper flange, a lower flange, and a web joined to the upper flange and the lower flange, and the cross-sectional dimensions of the lower flange perpendicular to the longitudinal direction of the beam are different from each other, the first beam and the second beam are defined as the first beam and the second beam, At least a portion of the lower flange of the first beam and the lower flange of the second beam are covered with a lower covering material that is made of a dry fire-resistant covering material and has the same cross-sectional dimension perpendicular to the longitudinal direction; A method for installing fire-resistant coating material, comprising covering at least a portion of the upper flange and web of the first beam and at least a portion of the upper flange and web of the second beam with an upper / middle coating material composed of at least one of a dry fire-resistant coating material and a wet fire-resistant coating material.

Images