Fireproof structure

Abstract

To provide a fireproof structure capable of exerting membrane effect even if the structure has a floor part having various specifications.SOLUTION: A fireproof structure 1 comprises: a plurality of fireproof beams having a prescribed fireproof performance; a plurality of fireproof columns, which have the prescribed fireproof performance and are connected to the plurality of fireproof beams so that a circular fireproof annular body consists of a portion of the plurality of fireproof columns and the whole of the plurality of fireproof beams; reduced fireproof beams 35 that are disposed in the fireproof annular body without having the prescribed fireproof performance so that both ends thereof are connected to the plurality of fireproof beams; and a floor part 45, which has a tensile force transmission member 47 provided in a concrete 46 and outer peripheral edge thereof so as to be entirely supported from below by the fireproof annular body and supported from below by the reduced fireproof beams. An opening 52b is formed on a top surface 52a of the floor part. When directions intersecting each other on the top surface are defined as a first intersection direction X and a second intersection direction Y, the tensile force transmission member transmits the tensile force between ends in the first intersection direction of the floor part and the tensile force between ends in the second intersection direction of the floor part.SELECTED DRAWING: Figure 5

Description

[Technical Field]

[0001] The present invention relates to a fire-resistant structure. [Background technology]

[0002] Conventionally, fire-resistant structures have been known in which a reinforced concrete slab (floor section) is supported by fire-resistant main beams (fire-resistant beams) and sub-beams with reduced fire-resistant coating (see, for example, Patent Document 1). In the fire-resistant structure of Patent Document 1, the minor beams are rigidly connected to the major beams. The slab is flat and supported by girders and sub-girders, to which horizontal steel plates are connected. With this configuration, the horizontal steel plates reinforce the connection structure between the main beam and the secondary beam, ensuring the fire resistance of the fire-resistant structure in the event of a fire. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6864991 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in the fire-resistant structure of Patent Document 1, the applicable slab specifications are limited.

[0005] The present invention has been made in consideration of these problems, and aims to provide a fire-resistant structure that can exert a membrane effect even when it is equipped with floor sections of a wider variety of specifications. [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 structure comprising: a plurality of fire-resistant beams having a predetermined fire resistance; a plurality of fire-resistant columns having the predetermined fire resistance and joined to the plurality of fire-resistant beams, with parts of the columns and the plurality of fire-resistant beams as a whole constituting a ring-shaped fire-resistant ring; reduced-fire-resistant beams that do not have the predetermined fire resistance and are arranged inside the fire-resistant ring, with both ends joined to the plurality of fire-resistant beams; and a floor section having a tensile force transmission member provided in concrete, whose outer peripheral edge is supported from below all around by the fire-resistant ring section and is supported from below by the reduced-fire-resistant beams, wherein an opening is formed on the upper surface of the floor section, and when directions that intersect each other within the upper surface are defined as a first intersecting direction and a second intersecting direction, the tensile force transmission member transmits the tensile force between the ends of the floor section in the first intersecting direction and the tensile force between the ends of the floor section in the second intersecting direction, respectively.

[0007] In this invention, the outer periphery of the floor section is supported from below by a fire-resistant ring body that has a predetermined fire resistance and can maintain a certain level of rigidity and strength even in the event of a fire. The tensile force transmission members provided in the floor section transmit the tensile force between the ends of the floor section in the first transverse direction and the tensile force between the ends of the floor section in the second transverse direction, respectively. In the event of a fire, gravity and other forces acting on the floor cause the center of the floor to bend downward in a plan view. However, due to the membrane effect, the outer periphery of the floor is supported by the fire-resistant ring. The tensile force transmission members, which are stretched by the bending of the floor, transmit tensile forces in the first intersecting direction and the second intersecting direction, respectively, thereby supporting the center of the floor. Therefore, the fire resistance performance of the fire-resistant structure can be maintained at the same level as before.

[0008] Within the fire-resistant ring body, reduced fire-resistance beams are arranged, each with both ends joined to multiple fire-resistance beams.Therefore, during normal times when no fire has occurred, the floor can be supported not only by the fire-resistant ring body but also by the reduced fire-resistance beams. As a result of careful investigation by the inventors, it was found that the above-mentioned membrane effect in the event of a fire and the effect of supporting the floor under normal conditions occur when an opening is formed in the floor. It was also found that these effects occur even when there is no opening in the floor. Therefore, the membrane effect can be exerted even when a fire-resistant structure has floors with a wide variety of specifications, regardless of whether they have openings or not.

[0009] (2) A second aspect of the present invention may be the fire-resistant structure according to (1), wherein the opening is located within 2 m of a corner of the floor portion. In general, it is believed that in the event of a fire, the principal stress acting within a range of 2 m from the corner of the floor is relatively small. With this invention, the floor will deflect in the event of a fire, but openings can be placed in positions that are unlikely to increase the deflection of the floor in the event of a fire.

[0010] (3) Aspect 3 of the present invention may be a fire-resistant structure as described in (1), in which the opening is located within one-fourth of the minimum length along the top surface of the floor from a corner of the floor. Generally, in the event of a fire, the principal stress acting on the area from the corner of the floor to within one-fourth of the minimum length along the top surface of the floor is considered to be relatively small. With this invention, the floor will deflect in the event of a fire, but openings can be placed in positions that are unlikely to increase the deflection of the floor in the event of a fire.

[0011] (4) A fourth aspect of the present invention may be the fire-resistant structure according to any one of (1) to (3), wherein a plurality of the openings are formed in the floor portion. In the present invention, a plurality of openings can be formed in the floor portion.

[0012] (5) A fifth aspect of the present invention is the fire-resistant structure according to claim 4, wherein the distance between the centers of the plurality of openings is at least twice the diameter of the openings. In this invention, for example, when the floor portion has reinforcing bars set in concrete, it is possible to ensure the thickness of concrete covering the reinforcing bars.

[0013] (6) Aspect 6 of the present invention may be a fire-resistant structure described in any one of (1) to (5), in which the floor portion has a first floor portion in which a first tensile force transmission member that is a part of the tensile force transmission member is provided in a first concrete that is a part of the concrete, and a part of its first outer peripheral edge is supported from below by the fire-resistant ring body, and a second floor portion in which a second tensile force transmission member that is at least a part of the remainder of the tensile force transmission member is provided in a second concrete that is at least a part of the remainder of the concrete, and a part of its second outer peripheral edge is supported from below by the fire-resistant ring body and at least a part of the remainder of the second outer peripheral edge is supported from below by a part of the first outer peripheral edge, and the opening is formed on the upper surface of the first floor portion or the second floor portion. In this invention, even when the floor section has a first floor section and a second floor section supported from below by the first floor section, a membrane effect can be exerted by the first tensile force transmission member and fire-resistant ring body for the first floor section, and the second tensile force transmission member and fire-resistant ring body for the second floor section. An opening can be formed in the upper surface of the first bed portion or the second bed portion. [Effects of the Invention]

[0014] The fire-resistant structure of the present invention can exert a membrane effect even when it is provided with floor sections of a wider variety of specifications. [Brief explanation of the drawings]

[0015] [Figure 1] 1 is a perspective view schematically showing a fireproof structure according to a first embodiment of the present invention. [Figure 2] FIG. 2 is a perspective view schematically showing a portion of the fire-resistant structure. [Figure 3] FIG. 3 is a cross-sectional view taken along the line A1-A1 in FIG. 2. [Figure 4] FIG. 3 is a cross-sectional view taken along the line A2-A2 in FIG. 2. [Figure 5] FIG. 3 is a cross-sectional view taken along the line A3-A3 in FIG. 2. [Figure 6] FIG. 2 is a plan view of the periphery of a through hole in the fire-resistant structure. [Figure 7] FIG. 4 is a perspective view schematically showing a fireproof structure according to a second embodiment of the present invention. [Figure 8] FIG. 1 is a perspective view illustrating the range in which the principal stress acting on the floor is compressive stress 15 minutes after the start of a fire. [Figure 9] FIG. 10 is a perspective view illustrating the range in which the principal stress acting on the floor is tensile stress 15 minutes after the start of a fire. [Figure 10] FIG. 10 is a perspective view illustrating the range in which the principal stress acting on the floor is compressive stress 30 minutes after the start of a fire. [Figure 11] FIG. 10 is a perspective view illustrating the range in which the principal stress acting on the floor is tensile stress 30 minutes after the start of a fire. [Figure 12] FIG. 10 is a perspective view illustrating the range in which the principal stress acting on the floor is compressive stress 60 minutes after the start of a fire. [Figure 13] FIG. 10 is a perspective view illustrating the range in which the principal stress acting on the floor is tensile stress 60 minutes after the start of a fire. [Figure 14] This is a perspective view illustrating the range in which the principal stress acting on the floor is compressive stress 141 minutes after the start of the fire. [Figure 15] FIG. 10 is a perspective view illustrating the range in which the principal stress acting on the floor is tensile stress 141 minutes after the start of the fire. DETAILED DESCRIPTION OF THE INVENTION

[0016] (First embodiment) A first embodiment of a fire-resistant structure according to the present invention will be described below with reference to FIGS. As shown in Figures 1 and 2, the fire-resistant structure 1 of this embodiment includes a plurality of fire-resistant beams 10, a plurality of fire-resistant columns 30, a plurality of reduced fire-resistant beams 35, and a floor section 45. Note that Figure 2 shows the floor section 45 in a see-through manner. In Figures 1 and 2 and Figure 7 described later, columns and beams to which fire-resistant covering is applied without being reduced are shown with hatching.

[0017] In the following, in order to define the directions, an outline of the floor portion 45 will first be described. The floor portion 45 is flat. For example, the floor portion 45 has a rectangular shape with multiple corners 45a when viewed in the thickness direction Z of the floor portion 45. The floor portion 45 is disposed so that the thickness direction Z is along the up-down direction. Here, "A is along (extends along) B" means that the angle between A and B is 30° or less. It is more preferable that this angle be 15° or less.

[0018] The directions perpendicular to each other within the upper surface 45b of the floor portion 45 are defined as a first intersecting direction X and a second intersecting direction Y. The first intersecting direction X is the longitudinal direction of the floor portion 45 when viewed in the thickness direction Z. The second intersecting direction Y is the lateral direction of the floor portion 45 when viewed in the thickness direction Z. One side of the first intersecting direction X is referred to as a first side X1 (hereinafter simply referred to as the first side X1). In the first intersecting direction X, the side opposite to the first side X1 is referred to as a second side X2 (hereinafter simply referred to as the second side X2). In this example, the minimum value of the length of the floor portion 45 along the upper surface 45b is the length of the floor portion 45 in the second intersecting direction Y. The first intersecting direction X and the second intersecting direction Y are not particularly limited as long as they are directions that intersect with each other within the upper surface 45b of the floor portion 45.

[0019] The plurality of fire resistance beams 10 include two first fire resistance beams 11 and two second fire resistance beams 21 . The two first fire-resistance beams 11 each extend along a first intersecting direction X. The two first fire-resistance beams 11 are disposed in a second intersecting direction Y at an interval from each other. The two second fire-resistance beams 21 each extend along the second intersecting direction Y. The two second fire-resistance beams 21 are disposed in the first intersecting direction X with a gap therebetween. Between the first fire resistance beam 11 and the second fire resistance beam 21, a gap S1 is formed in which the fire resistance column 30 is disposed.

[0020] As shown in Fig. 3, for example, a first fire resistance performance beam 11 is formed of an H-shaped steel 12 that is coated with a fire-resistant coating 17. The H-shaped steel 12 may be a rolled H-shaped steel or a welded and assembled H-shaped steel. A heat insulating material such as rock wool or glass wool is used for the fire-resistant coating 17. In this case, the fire-resistant coating 17 is formed on the H-beam steel 12 by, for example, a spray coating method.

[0021] The H-shaped steel 12 has two flanges 13 and 14 and a web 15 joined to each of the flanges 13 and 14. The flange 13 is disposed higher than the flange 14. Except for the length, the second fire-resistant beam 21 is configured in the same manner as the first fire-resistant beam 11. That is, the second fire-resistant beam 21 is formed of an H-shaped steel with a fire-resistant coating.

[0022] For example, the thickness of the fire-resistant coating 17, such as rock wool, on the first fire-resistance beam 11 is set in accordance with the "Construction Quality Control Guidelines for Sprayed Rockwool-Coated Fire-Resistant Structures (Spraying Division, Rockwool Industry Association)." If the first fire-resistance beam 11 is required to have a one-hour fire resistance, the thickness of the fire-resistant coating shall be 25 mm. Similarly, if the first fire-resistance beam 11 is required to have a two-hour fire resistance, the thickness of the fire-resistant coating shall be 45 mm. If the first fire-resistance beam 11 is required to have a three-hour fire resistance, the thickness of the fire-resistant coating shall be 60 mm. Hereinafter, the fire resistance performance based on the construction quality control guidelines for sprayed rock wool coated fire-resistant structures will be referred to as coated fire resistance performance (predetermined fire resistance performance). Each of the two first fire resistance beams 11 has coated fire resistance performance.

[0023] The predetermined fire resistance is not limited to the covering fire resistance, but may be, for example, the fire resistance based on the evaluation of the inherent fire resistance by the load heating test, the fire resistance based on the evaluation of the inherent fire resistance by the fire resistance verification method, etc. The second fire resistance beam 21 is the same as the first fire resistance beam 11. The fire-resistant coating may be formed by a formed plate method or a wrapping method. The fire-resistant beam may be formed of reinforced concrete, steel-reinforced concrete, fire-resistant wood, or fire-resistant wood and steel.

[0024] As shown in Fig. 3, gusset plates 18 are fixed by welding or the like to the webs 15 of the second side X2 of the two first fire resistance beams 11. The gusset plates 18 protrude toward the inside of the two first fire resistance beams 11 in the second cross direction Y. As shown in Fig. 4, gusset plates 19 are fixed by welding or the like to the webs 15 of the first side X1 portions of the two first fire resistance beams 11. The gusset plates 19 protrude toward the inside of the two first fire resistance beams 11 in the second cross direction Y. The upper ends of the gusset plates 19 are located lower than the upper ends of the gusset plates 18.

[0025] For example, the fire-resistant columns 30 are formed of H-shaped steel with a fire-resistant coating. The plurality of fire-resistant columns 30 have a fire-resistant coating. As shown in FIGS. 1 and 2, the plurality of fire-resistant columns 30 extend along the thickness direction Z. In this embodiment, the plurality of fire-resistant columns 30 are respectively arranged below the plurality of corners 45a of the floor portion 45. The ends of the plurality of fire-resistant beams 10 are rigidly joined to the upper ends (parts) of the plurality of fire-resistant columns 30. The upper ends of the plurality of fire-resistant columns 30 and the plurality of fire-resistant beams 10 as a whole constitute a square-ring (annular) fire-resistant ring body 32. In other words, the fire-resistant ring body 32 surrounds the region R1. In addition, the fire-resistant columns may be formed from fire-resistant coated square steel pipes, fire-resistant coated circular steel pipes, concrete-filled steel pipes, reinforced concrete, steel-reinforced concrete, fire-resistant treated wood, or fire-resistant treated wood and steel.

[0026] As shown in FIG. 3, in this embodiment, the reduced fire resistance beam 35 is formed of an H-shaped steel 36 with a fire-resistant coating (not shown). However, the reduced fire resistance beam 35 has lower fire resistance than the fire-resistant beam 10. For example, the thickness of the fire-resistant coating on the reduced fire resistance beam 35 is set to about 1 / 10 to 1 / 2 of the thickness of the fire-resistant coating based on the fire resistance performance of each coating. Therefore, the multiple reduced fire resistance beams 35 do not have the fire resistance of the coating. The H-shaped steel 36 has two flanges 37 and 38 and a web 39 joined to each of the flanges 37 and 38. The flange 37 is disposed higher than the flange 38. In addition, the reduced fire resistance beam does not need to have a fire-resistant coating.

[0027] 2, the plurality of reduced fire resistance beams 35 extend along the second transverse direction Y and are spaced apart from one another in the first transverse direction X. The plurality of reduced fire resistance beams 35 are arranged within the fire-resistant annular body 32. Both ends of the plurality of reduced fire resistance beams 35 are respectively joined to the plurality of fire resistance beams 10. Specifically, as shown in Figures 3 and 4, both ends of the plurality of reduced fire resistance beams 35 are fixed to gusset plates 18, 19 by bolts 41, 42, etc. In the following, among the multiple reduced fire resistance beams 35, the reduced fire resistance beam 35 connected to the gusset plate 19 (arranged on the first side X1) will also be referred to as reduced fire resistance beam 35A, and the reduced fire resistance beam 35 connected to the gusset plate 18 (arranged on the second side X2) will also be referred to as reduced fire resistance beam 35B.

[0028] As shown in Fig. 4, the upper end of flange 37 of reduced fire resistance beam 35A is positioned lower than the upper end of flange 13 of first fire resistance beam 11. On the other hand, as shown in Fig. 3, the upper end of flange 37 of reduced fire resistance beam 35B is positioned at the same height as the upper end of flange 13 of first fire resistance beam 11. 5, it is preferable that a support member 43 is fixed to the web 39 of the reduced fire resistance beam 35B arranged closest to the first side X1. The upper surface of the support member 43 is arranged in the middle of the web 39 in the thickness direction Z.

[0029] In this embodiment, the floor portion 45 is formed of a reinforced concrete slab. As shown in Fig. 5, the floor portion 45 is formed by providing a tensile force transmission member 47 in concrete 46. The outer peripheral edge of the floor portion 45 is supported from below over the entire periphery by a fire-resistant ring 32. The floor portion 45 is supported from below by a plurality of reduced fire resistance beams 35.

[0030] 1 and 5, the floor portion 45 has a first floor portion 50 and a second floor portion 65. The first floor portion 50 is disposed on the first side X1 and below the second floor portion 65. The first floor portion 50 is configured by providing a first tensile force transmission member 56 in a first concrete 51. The first concrete 51 is a part of the concrete 46. As shown in Figures 1 and 4 to 6, the first concrete 51 has a main body 52 and an edge portion 53. In Figure 6, the first tensile force transmission member 56 is indicated by a solid line.

[0031] The main body 52 has a flat plate shape. The main body 52 is disposed so that the thickness direction of the main body 52 is along the thickness direction Z. The main body 52 is disposed within the portion of the first side X1 of the fire-resistant ring 32. The main body 52 is disposed on the reduced fire resistance beam 35A and on the support member 43. A through-hole (opening) 52b is formed in the upper surface 52a of the main body 52. ​​The upper surface 52a is the upper surface of the floor section 45 (first floor section 50). The reduced fire resistance beam 35A supports the main body 52 of the first floor section 50 from below the main body 52. For example, the through-hole 52b has a circular shape when viewed in the thickness direction Z, and penetrates the main body 52 in the thickness direction Z. For example, the diameter of the through-hole 52b is 100 mm. A plurality of through holes 52b may be formed in the main body 52. ​​In this case, the distance between the centers of the plurality of through holes 52b is preferably at least twice the diameter of the through holes 52b.

[0032] When viewed in the thickness direction Z, the through hole 52b is preferably disposed within 2 m from the corner 45a of the floor portion 45. More specifically, when viewed in the thickness direction Z, the entire through hole 52b is preferably disposed within 2 m from the corner 45a of the floor portion 45. Furthermore, when viewed in the thickness direction Z, the through-hole 52b is preferably disposed within one-fourth of the length of the floor portion 45 in the second intersecting direction Y from the corner 45a of the floor portion 45. A plurality of through holes 52b may be formed in the floor portion 45. The main body 52 and the reduced fire resistance beam 35A are connected by headed studs or the like (not shown).

[0033] As shown in Fig. 1, the edge portion 53 is formed in a C-shape that opens toward the second side X2 when viewed in the thickness direction Z. As shown in Figs. 1 and 4, the edge portions 53 are disposed on the outer edges of both sides of the upper surface of the main body 52 in the second intersecting direction Y and on the outer edge of the first side X1. The edge portions 53 protrude outward from these outer edges along the horizontal plane. The outer portion of the edge portion 53 is supported from below by two first fire-resistant beams 11 and two second fire-resistant beams 21. In other words, a part of the first outer peripheral edge 50a, which is the outer peripheral edge of the first floor portion 50 when viewed in the thickness direction Z, is supported from below by the fire-resistant ring 32. The part of the first outer peripheral edge 50a here refers to the end portions of the first outer peripheral edge 50a on both sides in the second cross direction Y and the end portion on the first side X1. The edge 53 and the refractory ring 32 are connected by a headed stud or the like (not shown). The main body 52 and edge portion 53 of the first concrete 51 are integrally formed from concrete.

[0034] The first tensile force transmission member 56 is a part of the tensile force transmission member 47. As shown in Figures 5 and 6, the first tensile force transmission member 56 has a plurality of first main reinforcements 57, a plurality of second main reinforcements 58, and reinforcing steel bars 59 and 60. Note that the plurality of second main reinforcements 58 and the reinforcing steel bars 60 are not shown in Figure 5. As shown in Fig. 6, the multiple first main reinforcements 57 each extend along the first transverse direction X. The multiple first main reinforcements 57 are embedded in the first concrete 51 over the entire length between both ends of the first concrete 51 in the first transverse direction X. The multiple first main reinforcements 57 are arranged at intervals from one another in the second transverse direction Y. The multiple second main reinforcements 58 each extend along the second transverse direction Y. The multiple second main reinforcements 58 are embedded in the first concrete 51 over the entire length between both ends of the first concrete 51 in the second transverse direction Y. The multiple second main reinforcements 58 are arranged at intervals from one another in the first transverse direction X.

[0035] The reinforcing steel bars 59 extend in the first intersecting direction X and are arranged near the through holes 52b. The reinforcing steel bars 59 and the first main reinforcements 57 may be connected to each other by wire or the like. The reinforcing steel bars 60 extend in the second intersecting direction Y and are arranged near the through holes 52b. The reinforcing steel bars 60 and the second main reinforcements 58 may be connected to each other by wire or the like. The first tensile force transmission members 56 transmit the tensile force between the ends of the first floor portion 50 in the first transverse direction X and the tensile force between the ends of the first floor portion 50 in the second transverse direction Y. For example, during normal times when no fire has occurred and during a fire, the first tensile force transmission members 56 transmit the tensile force in the first transverse direction X generated at the end of the first side X1 of the first floor portion 50 by the multiple reinforcing bars 59 to the end of the second side X2 of the first floor portion 50, and also transmit the tensile force generated at the end of the second side X2 of the first floor portion 50 to the end of the first side X1 of the first floor portion 50. This tensile force is generated by the weight of the first floor portion 50, equipment placed on the first floor portion 50, etc. The same applies to the second intersecting direction Y as to the first intersecting direction X.

[0036] As shown in FIG. 5, the second floor portion 65 is configured by providing a second tensile force transmission member 67 in a second concrete 66 . The second concrete 66 is the remainder of the concrete 46. As shown in Figures 1 and 3, the second concrete 66 is in the form of a flat plate. A part of the second outer peripheral edge 65a, which is the outer peripheral edge of the second floor portion 65 when viewed in the thickness direction Z, is supported from below by the refractory ring 32. The part of the second outer peripheral edge 65a here refers to the end portions of the second outer peripheral edge 65a on both sides in the second transverse direction Y and the end portion on the second side X2. 5, the remainder of the second outer peripheral edge 65a is supported from below by a portion of the first outer peripheral edge 50a (the remainder is positioned above the portion of the first outer peripheral edge 50a). The remainder of the second outer peripheral edge 65a here refers to the end of the second outer peripheral edge 65a on the first side X1. The portion of the first outer peripheral edge 50a refers to the end of the first outer peripheral edge 50a on the second side X2. The second concrete 66, the fire-resistant ring body 32 and the reduced fire resistance beam 35B are connected by headed studs or the like (not shown).

[0037] The second tensile force transmission member 67 is the remaining part of the tensile force transmission member 47. The second tensile force transmission member 67 has a plurality of third main reinforcements 68, a plurality of fourth main reinforcements 69, and a plurality of reinforcing steel bars 70. Note that Fig. 5 shows only one of the plurality of third main reinforcements 68 and the plurality of reinforcing steel bars 70. The first main reinforcement 57 of the first tensile force transmission member 56, the third main reinforcement 68 of the second tensile force transmission member 67, and the reinforcing steel bar 70 constitute the first reinforcing steel bar 47a. As shown in Figure 6, the second main reinforcement 58 of the first tensile force transmission member 56 and the fourth main reinforcement 69 of the second tensile force transmission member 67 constitute the second reinforcing steel bar 47b.

[0038] The multiple third main reinforcements 68 each extend along the first transverse direction X. The multiple third main reinforcements 68 are embedded in the second concrete 66 over the entire length between both ends of the second concrete 66 in the first transverse direction X. The multiple third main reinforcements 68 are arranged at intervals from one another in the second transverse direction Y. The multiple fourth main reinforcements 69 each extend along the second transverse direction Y. The multiple fourth main reinforcements 69 are embedded in the second concrete 66 over the entire length between both ends of the second concrete 66 in the second transverse direction Y. The multiple fourth main reinforcements 69 are arranged at intervals from one another in the first transverse direction X.

[0039] For example, when viewed in the second intersecting direction Y, the reinforcing steel bar 70 is formed in a ring shape that is longer in the thickness direction Z than in the first intersecting direction X. The shape of the reinforcing steel bar depends on the specifications, height, etc. of a step 72 (described later) formed at the joint between the first floor portion 50 and the second floor portion 65. Each reinforcing steel bar 70 is connected to the third main reinforcement 68 and the first main reinforcement 57 of the first tensile force transmission member 56 by a wire (not shown) or the like. Each reinforcing steel bar 70 is connected to the first main reinforcement 57 of the first tensile force transmission member 56 by a wire or the like. The second tensile force transmission members 67 transmit the tensile force between the ends of the second floor portion 65 in the first transverse direction X and the tensile force between the ends of the second floor portion 65 in the second transverse direction Y, respectively. In addition, the reinforcing steel bars may have a shape that presents a cranked Z-shape when viewed in the second intersecting direction Y, or the like.

[0040] Each of the first reinforcing bars 47a extends along the first intersecting direction X. Each of the second reinforcing bars 47b extends along the second intersecting direction Y. Note that the first reinforcing bars 47a only need to extend along the first intersecting direction X when viewed in the thickness direction Z. The second reinforcing bars 47b only need to extend along the second intersecting direction Y when viewed in the thickness direction Z. The tensile force transmission member 47 is configured with a plurality of first reinforcing bars 47a and a plurality of second reinforcing bars 47b. The tensile force transmission members 47 transmit the tensile force between the ends of the floor portion 45 in the first transverse direction X and the tensile force between the ends of the floor portion 45 in the second transverse direction Y, respectively. The transmission of tensile force by the tensile force transmission member 47 and the transmission of tensile force by the second tensile force transmission member 67 are similar to the transmission of tensile force by the first tensile force transmission member 56 .

[0041] The reduced fire resistance beam 35B supports the second floor portion 65 from below the second floor portion 65. As described above, the reduced fire resistance beam 35 only needs to support at least one of the first floor portion 50 and the second floor portion 65 from below. As shown in Fig. 5, the first floor section 50 is disposed on the first side X1 and below the second floor section 65. A step 72 is formed in the vertical direction at the joint between the first floor section 50 and the second floor section 65. For example, the height of the step 72 is approximately half the beam depth of the reduced fire resistance beam 35B.

[0042] For example, the fire-resistant structure 1 is used by placing a bathtub (not shown) on the first floor portion 50 and passing a pipe 100 for draining water from the bathtub through the through-hole 52b.

[0043] As described above, in the fireproof structure 1 of this embodiment, the outer peripheral edge of the floor portion 45 is supported from below by the fireproof ring 32, which has fire-resistant coating performance and can maintain a certain level of rigidity and strength even in the event of a fire. The tensile force transmission members 47 provided in the floor portion 45 transmit the tensile force between the ends of the floor portion 45 in the first transverse direction X and the tensile force between the ends of the floor portion 45 in the second transverse direction Y. In the event of a fire, gravity and other forces acting on the floor 45 cause the center of the floor 45 to bend downward in a plan view. However, due to the membrane effect, the outer periphery of the floor 45 is supported by the fireproof ring 32. The tensile force transmission members 47, which are stretched as a result of the bending of the floor 45, transmit tensile forces in the first intersecting direction X and the second intersecting direction Y, thereby supporting the center of the floor 45. Therefore, the fire resistance performance of the fireproof structure 1 can be maintained at the same level as before. When the first reinforcing bar 47a stretches during a fire, for example, the first main reinforcing bar 57, the third main reinforcing bar 68, and the reinforcing reinforcing bar 70 that constitute the first reinforcing bar 47a stretch in the first transverse direction X as a unit.

[0044] A plurality of reduced fire resistance beams 35 are arranged within the fire-resistant ring body 32, with both ends each joined to a plurality of fire-resistant beams 10. Therefore, during normal times when no fire has occurred, the floor section 45 can be supported not only by the fire-resistant ring body 32 but also by the plurality of reduced fire resistance beams 35. As a result of careful investigation by the inventors, it has been found that the membrane effect during a fire and the effect of supporting the floor 45 under normal circumstances are achieved when the floor 45 has through-holes 52b. It has also been found that these effects are achieved even when no through-holes are formed in the floor 45. Therefore, the membrane effect can be achieved even when the fire-resistant structure 1 is equipped with floors 45 of a wider variety of specifications, regardless of whether or not they have through-holes 52b. This increases the degree of freedom in designing the floor portion 45 of the fire-resistant structure 1.

[0045] There are cases where through-hole 52b is located within 2 m of corner 45a of floor portion 45. Generally, in the event of a fire, it is considered that the principal stress acting within a range of 2 m from corner 45a of floor portion 45 is relatively small. In this invention, floor portion 45 will bend in the event of a fire, but through-hole 52b can be located in a position that is unlikely to increase the bending of floor portion 45 in the event of a fire. The through hole 52b may be located within one-fourth of the length of the floor portion 45 in the second intersecting direction Y from the corner 45a of the floor portion 45. Generally, in the event of a fire, the principal stress acting within a range from the corner 45a of the floor portion 45 within one-fourth of the minimum length along the top surface of the floor portion is considered to be relatively small. In this invention, the floor portion 45 will deflect in the event of a fire, but the through hole 52b can be located in a position that is unlikely to increase the deflection of the floor portion 45 in the event of a fire.

[0046] There may be a case where a plurality of through holes 52b are formed in the floor portion 45. In this case, a plurality of through holes 52b can be formed in the floor portion 45. The distance between the centers of the multiple through holes 52b may be twice or more the diameter of the through holes 52b. In this case, for example, when the floor portion 45 has reinforcing bars installed in the concrete, it is possible to ensure a sufficient thickness of concrete covering the reinforcing bars.

[0047] The floor portion 45 has a first floor portion 50 and a second floor portion 65, and a through hole 52b is formed in the upper surface 52a of the first floor portion 50. In this way, even when the floor portion 45 has the first floor portion 50 and the second floor portion 65 supported from below by the first floor portion 50, the first tensile force transmission member 56 and the fireproof ring 32 for the first floor portion 50, and the second tensile force transmission member 67 and the fireproof ring 32 for the second floor portion 65 can each exert a membrane effect. Then, a through hole 52b can be formed in the upper surface 52a of the first floor portion 50.

[0048] The floor portion 45 is formed of a reinforced concrete slab. Since reinforced concrete slabs are widely used as floor portions, the floor portion 45 can be constructed inexpensively. The tensile force transmission member 47 has a plurality of first reinforcing bars 47a and a plurality of second reinforcing bars 47b. Therefore, with a simple configuration of a plurality of first reinforcing bars 47a and a plurality of second reinforcing bars 47b, the tensile force between the ends of the floor portion 45 in the first transverse direction X and the tensile force between the ends of the floor portion 45 in the second transverse direction Y can be transmitted.

[0049] The first fire-resistant performance beam 11 is formed of an H-shaped steel 12 with a fire-resistant coating 17. H-shaped steel with a fire-resistant coating is widely used as a beam with fire-resistant performance, so the first fire-resistant performance beam 11 can be constructed inexpensively. The fire-resistant column 30 is formed of an H-shaped steel beam with a fire-resistant coating. Since the H-shaped steel beam with a fire-resistant coating is widely used as a fire-resistant column, the fire-resistant beam 10 can be constructed inexpensively.

[0050] The fire-resistant coating 17 is formed on the H-shaped steel 12 by a spray coating method. The spray coating method and the molded plate method are widely used to apply fire-resistant coatings to H-shaped steel and the like, and therefore the fire-resistant coating 17 can be applied inexpensively.

[0051] In this embodiment, the floor portion 45 may be formed of, for example, a composite slab having a deck plate and concrete placed on the deck plate. In this case, the deck plate constitutes a tensile force transmission member. The through hole may be formed in the upper surface of the second floor portion 65. The opening may be a through hole, or may be a recess formed in the upper surface of the floor portion 45 and not penetrating the floor portion 45 in the thickness direction Z. The number of first reinforcing bars 47a and second reinforcing bars 47b included in the tensile force transmission member may be one each. The bed portion may have three or more bed portions, such as a first bed portion, a second bed portion, a third bed portion, and so on.

[0052] (Second embodiment) Next, a second embodiment of the present invention will be described with reference to FIGS. 7 to 15. The same components as those in the above embodiment are designated by the same reference numerals, and their description will be omitted. Only the differences will be described. As shown in FIG. 7, the fireproof structure 2 of this embodiment has a floor portion 75 instead of the floor portion 45 in each configuration of the fireproof structure 1 of the first embodiment. In this embodiment, each of the reduced fire resistance beams 35 is configured as a reduced fire resistance beam 35B. The floor portion 75 does not have a plurality of floor portions 50, 65 like the floor portion 45 of the second embodiment, but is formed integrally in the shape of a flat plate.

[0053] The floor portion 75 is constructed by providing a tensile force transmission member (not shown) in concrete 76. The outer peripheral edge of the floor portion 75 is supported from below all around by a fire-resistant ring body 32, and is also supported from below by a plurality of reduced fire resistance beams 35B. The concrete 76 has an upper surface 76a formed with a through-hole (opening) 76b.

[0054] The fireproof structure 2 of this embodiment configured as described above can also achieve the same effects as the fireproof structure 1 of the first embodiment.

[0055] (Simulation results) Simulations were performed using fire-resistant structure 2 as an analytical model. The length of the floor portion 75 in the first intersecting direction X was set to 19.5 m. The length of the floor portion 75 in the second intersecting direction Y was set to 7.2 m. The boundary condition of the fire-resistant structure 2 is that the lower ends of the multiple fire-resistant columns 30 are each completely restrained. At normal temperatures before the fire started, fire-resistant structure 2 had a resistance of 4900N / m 2 The design live load is acting on the structure.

[0056] The simulation was carried out by dividing the floor 75 into multiple elements. The underside of the fire-resistant structure 2 was heated based on the "standard heating time-temperature curve" specified in ISO 834, which assumes heating due to fire. The criterion for the fire-resistant structure 2 becoming unable to withstand a fire was set to the point at which the distortion of the material constituting the fire-resistant structure 2 became so great that the deflection of the floor portion 75 increased. The simulation was stopped 141 minutes after the fire started because the criteria had been met.

[0057] In the simulation, the distribution of principal stress occurring within the plane of floor 75 was determined. The distribution of principal stress 15 minutes, 30 minutes, 60 minutes, and 141 minutes after the start of the fire is shown in Figures 8 to 15. For ease of explanation, the cases where the principal stress is compressive stress and where the principal stress is tensile stress are shown in separate figures. In each figure, the direction of the line segment corresponding to each element represents the direction of the principal stress, and the size of the line segment corresponding to each element represents the magnitude of the principal stress.

[0058] It was found that as time passed after the start of the fire, the magnitude and range of compressive stress decreased, while the magnitude and range of tensile stress increased. These results show that the principal stress acting within 2 m from the corner of the floor 75 is relatively small.

[0059] Although the first and second embodiments of the present invention have been described above in detail 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 and second embodiments, the part of the fire-resistant column 30 is not limited to the upper end of the fire-resistant column 30, but may be the middle part of the fire-resistant column 30 in the thickness direction Z. In this case, the fire-resistant column 30 protrudes upward beyond the floor parts 45, 75. The number of reduced fire resistance beams 35 provided in the fire-resistant structures 1 and 2 may be one. [Explanation of symbols]

[0060] 1,2 Fireproof structures 10 Fire resistance beam 30 Fire resistance performance pillar 32 Refractory ring 35,35A,35B Reduced fire resistance beam 45,75 Floor 45a corner 46 Concrete 47 Tensile force transmission member 47a First rebar 47b Second rebar 50 First Floor 50a First outer edge 52a Top side 52b Through hole (opening) 56 First tensile force transmission member 65 Second Floor 65a Second outer edge X 1st cross direction Y Second cross direction

Claims

1. A plurality of fire-resistant beams having a predetermined fire resistance; A plurality of fire-resistant columns having the predetermined fire resistance, joined to the plurality of fire-resistant beams, and forming an annular fire-resistant ring body with a part of the columns and the entire plurality of fire-resistant beams; A reduced fire resistance beam that does not have the predetermined fire resistance and is arranged inside the fire resistance annular body, and both ends of which are joined to the plurality of fire resistance beams, respectively; a floor portion in which a tensile force transmission member is provided in concrete, the outer peripheral edge of which is supported from below by the fire-resistant ring body over its entire circumference, and which is supported from below by the reduced fire resistance beam; Equipped with An opening is formed in the upper surface of the floor portion, When directions intersecting each other in the upper surface are defined as a first intersecting direction and a second intersecting direction, A fire-resistant structure, wherein the tensile force transmission member transmits a tensile force between the ends of the floor portion in the first intersecting direction and a tensile force between the ends of the floor portion in the second intersecting direction.

2. The fire-resistant structure according to claim 1, wherein the opening is located within 2 m of a corner of the floor portion.

3. 2. The fire-resistant structure according to claim 1, wherein the opening is located within one-fourth of the minimum length along the top surface of the floor from a corner of the floor.

4. The fire-resistant structure according to claim 1 , wherein a plurality of the openings are formed in the floor portion.

5. The fire-resistant structure according to claim 4 , wherein the distance between the centers of the plurality of openings is at least twice the diameter of the openings.

6. The floor portion is a first floor portion, in which a first tensile force transmission member, which is a part of the tensile force transmission member, is provided in a first concrete, which is a part of the concrete, and a first outer peripheral edge of the first tensile force transmission member is supported from below by the fireproof annular body; a second floor portion in which a second tensile force transmission member, which is at least a part of the remainder of the tensile force transmission member, is provided in a second concrete, which is at least a part of the remainder of the concrete, and a second outer peripheral edge of the second tensile force transmission member is supported from below by the fireproof annular body, and at least a part of the remainder of the second outer peripheral edge is supported from below by a part of the first outer peripheral edge; and The fire-resistant structure according to claim 1 or 2, wherein the opening is formed in an upper surface of the first floor portion or the second floor portion.

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