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 fireproof performance; a plurality of fireproof columns, which have the fireproof performance and are connected to the plurality of fireproof beams so that a fireproof annular body consists of a portion of the fireproof columns and the plurality of fireproof beams; a first floor part 50, which has a first tensile force transmission member 56 provided in a first concrete 51 and a first outer peripheral edge 50a that is partially supported by the fireproof annular body; a second floor part 65, which has a second tensile force transmission member 67 linked to the first tensile force transmission member in a second concrete 66, and a second outer peripheral edge 65a that is partially supported by the fireproof annular body so that a remaining part of the second outer peripheral edge is partially disposed above a remaining part of the first outer peripheral edge; and reduced fireproof beams 35 that are disposed in the fireproof annular body without having the fireproof performance so that both ends thereof are connected to the plurality of fireproof beams, respectively, and so as to support at least either the first floor part or the second 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 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 a portion of each column and the plurality of fire-resistant beams as a whole constituting a ring-shaped fire-resistant ring; a first floor section having a first tensile force transmission member disposed in a first concrete body and a portion of a first outer periphery of the first floor section supported from below by the fire-resistant ring; a second floor section having a second tensile force transmission member connected to the first tensile force transmission member disposed in a second concrete body and a portion of a second outer periphery of the second floor section supported by the fire-resistant ring; and a second floor section having a second tensile force transmission member disposed in a second concrete body and connected to the first tensile force transmission member; a second floor section having a second outer periphery of the second floor section supported by the fire-resistant ring; and a second floor section having a second tensile force transmission member disposed in a second concrete body and connected to the second tensile force transmission member; a second floor section having a second outer periphery of the second floor section supported by the fire-resistant ring; and a second floor section having a second outer periphery of the second floor section with at least a portion of the remainder of the second outer periphery located above at least a portion of the remainder of the first outer periphery; and a reduced fire resistance beam that does not have the specified fire resistance and is arranged within the fire resistance annular body, has both ends joined to the plurality of fire resistance beams, and supports at least one of the first floor section and the second floor section from below, wherein when the directions that intersect with each other within the upper surface of the first floor section are defined as the first intersecting direction and the second intersecting direction, the first tensile force transmission member transmits the tensile force between the ends of the first floor section in the first intersecting direction and the tensile force between the ends of the first floor section in the second intersecting direction, respectively, and the second tensile force transmission member transmits the tensile force between the ends of the second floor section in the first intersecting direction and the tensile force between the ends of the second floor section in the second intersecting direction, respectively.

[0007] In this invention, a part of the first outer peripheral edge of the first floor section is supported from below by a fire-resistant annular body that has a predetermined fire resistance and can maintain a certain level of rigidity and strength even in the event of a fire. First tensile force transmission members provided in the first floor section transmit the tensile force between the ends of the first floor section in the first transverse direction and the tensile force between the ends of the first floor section in the second transverse direction. Similarly, a portion of the second outer periphery of the second floor section is supported by the refractory ring. Second tensile force transmission members provided in the second floor section transmit tensile forces between the ends of the second floor section in the first transverse direction and between the ends of the second floor section in the second transverse direction, respectively. A step is formed in the vertical direction at the joint between the first bed section and the second bed section.

[0008] In the event of a fire, gravity and other forces acting on the first and second floor sections cause the centers of the first and second floor sections as a whole to bend convexly downward in a plan view. However, due to the membrane effect, the outer peripheries of the first and second floor sections as a whole are supported by the fire-resistant rings. The first and second tensile force transmission members, which are connected to each other and stretched as the first and second floor sections bend, transmit tensile forces in the first and second intersecting directions, respectively, thereby supporting the centers of the first and second floor sections as a whole. Therefore, the fire resistance performance of the fire-resistant structure can be maintained at the same level as before.

[0009] 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, not only the fire-resistant ring body but also the reduced fire-resistance beams can support at least one of the first floor section and the second floor section. 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 entire first and second floor sections under normal circumstances occur when a step is formed between the first and second floor sections. It was also found that these effects occur even when there is no step between the first and second floor sections. Therefore, the membrane effect can be achieved even when a fire-resistant structure is equipped with floor sections of a wide variety of specifications, regardless of whether there is a step or not.

[0010] (2) Aspect 2 of the present invention may be a fire-resistant structure as described in (1), which includes reinforcing steel bars arranged within at least one of the first concrete and the second concrete near the joint between the first floor section and the second floor section. In this invention, at least one of the first concrete and the second concrete in the vicinity of the joint can be reinforced by the reinforcing steel bars. [Effects of the Invention]

[0011] 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]

[0012] [Figure 1] 1 is a perspective view schematically showing a fire-resistant structure according to one 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. 2 is a perspective view of the analytical model as seen from above. [Figure 8] FIG. 2 is a perspective view of the analysis model as seen from below. [Figure 9] FIG. 1 is a perspective view showing the analysis results of a fire-resistant structure 1A. [Figure 10] FIG. 1 is a perspective view showing the analysis results of a fire-resistant structure 2. [Figure 11] FIG. 1 is a perspective view showing the analysis results of a fire-resistant structure 1B. [Figure 12] FIG. 2 is a side view schematically showing a main part of a fire-resistant structure 1A that has been deformed during a fire. [Figure 13] FIG. 2 is a side view showing a schematic view of a main part of a fire-resistant structure 2 that has been deformed during a fire. [Figure 14] FIG. 1 is a side view schematically showing a main part of a fire-resistant structure 1B that has been deformed during a fire. [Figure 15] FIG. 10 is a diagram showing the change in the deflection of the floor section over time. [Figure 16] FIG. 10 is a cross-sectional side view of a main part of a fire-resistant structure according to a first modified example of an embodiment of the present invention. [Figure 17] FIG. 10 is a cross-sectional side view of a main part of a fire-resistant structure according to a second modified example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0013] Hereinafter, one embodiment of a fire-resistant structure according to the present invention will be described 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, a first floor section 50, and a second floor section 65. Note that Figure 2 shows the first floor section 50 and the second floor section 65 in a see-through manner. In Figures 1 and 2, columns and beams on which fire-resistant covering is applied without being reduced are shown with hatching.

[0014] In the following, in order to define the directions, first, an overview of the first floor portion 50 will be described. As shown in FIG. 1, the main body 52 of the first floor portion 50, which will be described later, is flat. For example, the main body 52 has a rectangular shape with multiple corners when viewed in the thickness direction Z of the main body 52. ​​The main body 52 is disposed so that its thickness direction Z is aligned with the up-down direction. Here, "A is aligned with (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.

[0015] Here, directions that are perpendicular to each other within the upper surface 52a of the main body 52 (first floor portion 50) 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 first floor portion 50 and the second floor portion 65 as a whole when viewed in the thickness direction Z. The second intersecting direction Y is the lateral direction of the first floor portion 50 and the second floor portion 65 as a whole 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). 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 52a of the main body 52.

[0016] As shown in FIG. 2, 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.

[0017] 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.

[0018] 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.

[0019] 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.

[0020] 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 made of reinforced concrete or steel-reinforced concrete.

[0021] 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.

[0022] 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 FIG. 2, the plurality of fire-resistant columns 30 extend along the thickness direction Z. In this embodiment, the upper ends of the plurality of fire-resistant columns 30 are respectively arranged in the gap S1. The ends of the plurality of fire-resistant beams 10 are rigidly joined to (a portion of) the upper ends 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 column may be formed from any of a square steel pipe with a fire-resistant coating, a circular steel pipe with a fire-resistant coating, a concrete-filled steel pipe, reinforced concrete, and steel-reinforced concrete.

[0023] 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 in 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.

[0024] 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.

[0025] 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.

[0026] In this embodiment, the first floor portion 50 and the second floor portion 65 are each formed of a reinforced concrete slab. As shown in Figures 5 and 6, the first floor portion 50 is formed by providing a first tensile force transmission member 56 and reinforcing steel bars 59, 60 in a first concrete 51. As shown in FIGS. 1 and 4, the first concrete 51 has a main body 52 and an edge portion 53.

[0027] 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 body 32. The main body 52 is disposed on the reduced fire resistance beam 35A and on the support member 43. The main body 52 has an upper surface 52a formed with one through-hole 52b. 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. The main body 52 and the reduced fire resistance beam 35A are connected by headed studs or the like (not shown). The reduced fire resistance beam 35A supports the main body 52 of the first floor section 50 from below the main body 52. ​​The first floor section 50 is joined to the web 39 of the H-shaped steel 36 of the reduced fire resistance beam 35B via support members 43 and headed studs or the like (not shown).

[0028] 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.

[0029] 5 and 6, the first tensile force transmission member 56 has a plurality of first main reinforcements (first reinforcing bars) 57 and a plurality of second main reinforcements (second reinforcing bars) 58. Note that the plurality of second main reinforcements 58 and reinforcing bars 60, which will be described later, are not shown in Fig. 5. In Fig. 6, the first tensile force transmission member 56 and the like are indicated by solid lines. 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.

[0030] 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 reinforcing bars 59, 60 are arranged near the joint between the first floor section 50 and the second floor section 65. Here, "near the joint between the first floor section 50 and the second floor section 65" means, for example, a range from the outer surface of the joint between the first floor section 50 and the second floor section 65 within five times the thickness of the thinner of the first floor section 50 and the second floor section 65.

[0031] 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.

[0032] As shown in Fig. 5, the second floor section 65 is configured by providing a second tensile force transmission member 67 and a plurality of reinforcing bars 70 in a second concrete 66. Note that Fig. 5 shows only one of the plurality of reinforcing bars 70. As shown in FIGS. 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. As shown in Fig. 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 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 remainder of the second outer peripheral edge 65a is positioned above the remainder of the first outer peripheral edge 50a. The second concrete 66, the fire-resistant ring 32, and the reduced fire-resistance beam 35B are connected by headed studs or the like (not shown). The reduced fire-resistance beam 35B supports the second concrete 66 of the second floor portion 65 from below the second concrete 66.

[0033] As shown in Fig. 5, the second tensile force transmission member 67 has a plurality of third main reinforcements 68 and a plurality of fourth main reinforcements 69. Note that Fig. 5 shows only one of the plurality of third main reinforcements 68.

[0034] 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.

[0035] 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 and height of a step 72 (described later) formed at the joint between the first floor portion 50 and the second floor portion 65. The reinforcing steel bar 70 is arranged near 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 bars 68 by a wire (not shown) or the like. Each reinforcing steel bar 70 is connected to the first main reinforcement bars 57 of the first tensile force transmission member 56 by a wire or the like. In this way, the third main reinforcement bars 68 of the second tensile force transmission member 67 are connected to the first main reinforcement bars 57 of the first tensile force transmission member 56 via the reinforcing steel bars 70 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. The transmission of tensile force by the second tensile force transmission member 67 is similar to the transmission of tensile force by the first tensile force transmission member 56 .

[0036] 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.

[0037] 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.

[0038] (Analysis results) Here, the results of analyzing the fire resistance performance of fire-resistant structures will be explained. The analysis was performed using an analytical model of a fire-resistant structure 1A shown in FIGS. It should be noted that the ends of the plurality of fire resistance beams 10 and the reduced fire resistance beam 35B are rigidly joined. The cross-sectional dimensions of the H-shaped steel beams of fire resistance performance 10 and reduced fire resistance performance beams 35B were H-450 x 200 x 9 x 14, and the steel type was SS400 (general structural rolled steel). In the H-shaped steel of the fire-resistant beam 10, it was assumed that the two flanges and webs show the same temperature history (the temperature changes over time are the same for each other). The temperature history of the reduced fire-resistant beam 35B is also the same as that of the fire-resistant beam 10.

[0039] The first floor section 50A is a flat deck slab. That is, the first floor section 50A has a first tensile force transmission member (not shown) instead of the first tensile force transmission member 56 in each configuration of the first floor section 50. The first tensile force transmission member has a deck plate (not shown) in addition to the multiple first main reinforcements 57 and multiple second main reinforcements 58 that the first tensile force transmission member 56 has. The plurality of first main reinforcements 57 and the plurality of second main reinforcements 58 are configured in two layers, upper and lower. The main reinforcement bars (first main reinforcement bars 57 and second main reinforcement bars 58) and distribution reinforcement bars in the upper layer are arranged with D10@200 (diameter 10 mm, 200 mm pitch). The main reinforcement bars and distribution reinforcement bars are assumed to be made of deformed steel bars SD295. The main reinforcement and distribution reinforcement of the lower layer are of the same configuration as the main reinforcement and distribution reinforcement of the upper layer. The deck plate supports the first concrete 51 from below the first concrete 51. The design standard strength of the first concrete 51 was set to Fc21.

[0040] The second floor section 65A is a fellow deck slab. That is, the second floor section 65A has a second tensile force transmission member (not shown) instead of the second tensile force transmission member 67 in each configuration of the second floor section 65. The second tensile force transmission member has a deck plate (not shown) in addition to the multiple third main reinforcements 68 and multiple fourth main reinforcements 69 that the second tensile force transmission member 67 has. The plurality of third main reinforcements 68 and the plurality of fourth main reinforcements 69 are configured in one layer. The main reinforcement, consisting of a plurality of third main reinforcement bars 68 and a plurality of fourth main reinforcement bars 69, and the distribution reinforcement bars are arranged with D10@200. The main reinforcement and the distribution reinforcement bars are assumed to be formed from deformed steel bars SD295. The deck plate supports the second concrete 66 from below the second concrete 66. The design standard strength of the second concrete 66 was set to Fc21.

[0041] The undersides of the first floor section 50A and the second floor section 65A were heated based on the "standard heating time-temperature curve" specified in ISO 834, which assumes heating due to fire.

[0042] In addition to Fire Resistant Structure 1A, the following specifications were analyzed for fire-resistant structures: - A specification in which the fire-resistant structure 1A does not have multiple reinforcing bars (connecting bars) 70 (hereinafter referred to as the fire-resistant structure 1B). In the fire-resistant structure 1A, the first floor section 50A is not joined to the web of the H-shaped steel of the reduced fire resistance beam 35B (hereinafter referred to as fire-resistant structure 1C). In the fire-resistant structure 1A, the first floor section 50 and the second floor section 65 are formed on the same plane, forming an integrated floor section 75 (see Figure 10) without a step 72 (hereinafter referred to as the fire-resistant structure 2). The analysis was also carried out for fire-resistant structures 1B, 1C, and 2 under the same conditions as for fire-resistant structure 1A.

[0043] Contour diagrams (isoline diagrams) of the analysis results are shown in Figs. 9 to 11. The analysis results shown in Figs. 9 to 11 are the results at the end of the analysis of the fire-resistant structures 1A, 2, and 1B. 9 to 11, the darker the gray color, the greater the deflection. However, the same shade of gray does not represent the same deflection (magnitude of deflection) between FIGS. 9 to 11. Arrows B1, B2, and B3 in FIGS. 9 to 11 indicate the positions where the deflection of the floor is greatest.

[0044] Fig. 9 shows the analysis results for the fire-resistant structure 1A. Similarly, Fig. 10 shows the analysis results for the fire-resistant structure 2, and Fig. 11 shows the analysis results for the fire-resistant structure 1B. 12 to 14 are side views showing schematic views of the main parts of the fire-resistant structures 1A, 2, and 1B that have been deformed during a fire. Figure 15 shows the change in the deflection of the floor of a fire-resistant structure over time. The symbols in Figure 15 correspond to the symbols of fire-resistant structures 1A, 1B, 1C, and 2. The deflection of the floor here refers to the value at the position of the floor where the deflection is greatest.

[0045] It was found that in fire-resistant structures 1A and 1C having reinforcing steel bars 70 and forming steps 72, the deflection of the floor over time is smaller than in fire-resistant structure 2 having an integral floor 75 without steps 72.

[0046] As described above, in the fireproof structure 1 of this embodiment, a portion of the first outer peripheral edge 50a of the first floor portion 50 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 first tensile force transmission members 56 provided in the first floor portion 50 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 in the second transverse direction Y. Similarly, a portion of the second outer peripheral edge 65a of the second floor portion 65 is supported from below by the refractory ring 32. The second tensile force transmission members 67 provided in the second floor portion 65 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.

[0047] In the event of a fire, gravity and other forces acting on the first and second floor sections 50 and 65 cause the central portions of the first and second floor sections 50 and 65 as a whole to bend convexly downward in a plan view. However, due to the membrane effect, the outer peripheries of the first and second floor sections 50 and 65 as a whole are supported by the fireproof rings 32. The first tensile force transmission members 56 and second tensile force transmission members 67, which are connected to each other and stretched as the first and second floor sections 50 and 65 bend, transmit tensile forces in the first transverse direction X and the second transverse direction Y, respectively, thereby supporting the central portions of the first and second floor sections 50 and 65 as a whole. Therefore, the fire resistance performance of the fireproof structure 1 can be maintained at the same level as in the past.

[0048] 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 resistance beams 10.Therefore, during normal times when no fire has occurred, the first floor section 50 and the second floor section 65 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 entire first floor section 50 and the second floor section 65 under normal circumstances are achieved when the step 72 is formed in the first floor section 50 and the second floor section 65. It has also been found that these effects are achieved even when the step 72 is not formed in the first floor section 50 and the second floor section 65. Therefore, the membrane effect can be achieved even when the fire-resistant structure 1 is equipped with floor sections of a wider variety of specifications, regardless of whether the step 72 is present or not.

[0049] The fire-resistant structure 1 has reinforcing bars 59, 60, and 70. Therefore, the reinforcing bars 59, 60, and 70 can reinforce the first concrete 51 and the second concrete 66 in the vicinity of the joint.

[0050] The first floor portion 50 is formed of a reinforced concrete slab. Since reinforced concrete slabs are widely used as floor portions, the first floor portion 50 can be constructed inexpensively. The first tensile force transmission member 56 has a plurality of first main reinforcements 57 and a plurality of second main reinforcements 58. Therefore, with a simple configuration of a plurality of first main reinforcements 57 and a plurality of second main reinforcements 58, 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 can be transmitted.

[0051] 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 with a fire-resistant coating. Since the H-shaped steel with a fire-resistant coating is widely used as a column with fire resistance, the fire-resistant column 30 can be constructed inexpensively.

[0052] 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.

[0053] The configuration of the fire-resistant structure 1 of this embodiment can be modified in various ways as described below. A fireproof structure 4 of a first modified example shown in FIG. 16 has a first floor portion 50B and a second floor portion 65B instead of the first floor portion 50 and the second floor portion 65 in each configuration of the fireproof structure 1 of this embodiment. The first tensile force transmission member 80 of the first floor section 50B is composed of two layers: an upper layer 81A arranged above and a lower layer 81B arranged below. The upper layer 81A and the lower layer 81B have a plurality of first main reinforcements (first reinforcing bars) and a plurality of second main reinforcements (second reinforcing bars), not shown. The second tensile force transmission member 85 of the second floor portion 65B is configured with two layers: an upper layer 86A disposed above, and a lower layer 86B disposed below.

[0054] In the fire-resistant structure 4, the first main reinforcement etc. of the upper layer 81A extends along the lower layer 86B of the second tensile force transmission member 85. The first main reinforcement etc. of the upper layer 81A and the lower layer 86B may be connected to each other by wire or the like. The first main reinforcement etc. of the lower layer 81B extends up to above the headed studs 37a fixed to the flanges 37 of the H-shaped steel 36 of the reduced fire resistance beam 35B. The fire-resistant structure 4 includes a connecting bar 88 arranged across the first concrete 51 of the first floor portion 50B and the second concrete 66 of the second floor portion 65B.

[0055] The connecting bar 88 has a Z-shape when viewed in the second transverse direction Y. The end of the connecting bar 88 on the first side X1 extends along the lower layer 81B in the first floor portion 50B. This end and the lower layer 81B may be connected to each other by a wire or the like. The end of the connecting bar 88 on the second side X2 extends along the upper layer 86A in the second floor portion 65B. This end and the upper layer 86A may be connected to each other by a wire or the like. In the fire-resistant structure 4, the upper layer 81A of the first tensile force transmission member 80 and the upper layer 86A of the second tensile force transmission member 85 are not connected to each other.

[0056] In the fire-resistant structure 5 of the second modified example shown in FIG. 17, the second tensile force transmission member 85 is made of, for example, New Fellow Deck (registered trademark, Fuji Showa Giken Co., Ltd.). In this case, shear force acts on the cross section defined by planes L1 and L2 shown in Figure 17. Plane L1 extends from the flange 37 of the H-shaped steel 36 of the reduced fire resistance beam 35B along the underside of the second concrete 66 to the first side X1 and also extends in the second transverse direction Y. Plane L2 extends from the web 39 of the H-shaped steel 36 of the reduced fire resistance beam 35B along the upper surface 52a of the main body 52 of the first concrete 51 to the first side X1 and also extends in the second transverse direction Y.

[0057] The fireproof structure 4 of the first modified example and the fireproof structure 5 of the second modified example configured as described above can also achieve the same effects as the fireproof structure 1 of this embodiment.

[0058] The above describes in detail one embodiment of the present invention and its modified examples with reference to the drawings. However, the specific configurations are not limited to this embodiment and modified examples, and also include modifications, combinations, deletions, etc. of the configurations within the scope that does not deviate from the gist of the present invention. For example, the first floor portion 50 of the fire-resistant structure 1 does not necessarily have to have the through-hole 52b formed therein. The fire-resistant structure 1 does not necessarily have to have the reinforcing bars 59, 60, and 70.

[0059] 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 first floor portion 50 and the second floor portion 65. The number of reduced fire resistance beams 35 provided in the fire-resistant structures 1, 4, and 5 may be one. The fire-resistant structure may have three or more floors, such as a first floor, a second floor, a third floor, and so on. [Explanation of symbols]

[0060] 1,4,5 Fireproof structures 10 Fire resistance beam 30 Fire resistance performance pillar 32 Refractory ring 35,35A,35B Reduced fire resistance beam 50,50B 1st floor 50a First outer edge 51 First Concrete 56, 80 First tensile force transmission member 52a Top side 57 First main bar (first rebar) 58 Second main bar (second rebar) 59, 60, 70 Reinforcement bars 65,65B 2nd floor 65a Second outer edge 66 Second Concrete 67,85 Second tensile force transmission member 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 first floor portion including a first tensile force transmission member disposed in the first concrete, the first outer peripheral edge of the first tensile force transmission member being supported from below by the fireproof annular body; a second floor portion in which a second tensile force transmission member connected to the first tensile force transmission member is provided in the second concrete, a second outer peripheral edge of the second tensile force transmission member being supported by the fireproof annular body, and at least a portion of a remainder of the second outer peripheral edge being positioned above at least a portion of a remainder of the first outer peripheral edge; a reduced fire resistance beam that does not have the predetermined fire resistance and is arranged within the fire resistance annular body, has both ends joined to the plurality of fire resistance beams, and supports at least one of the first floor portion and the second floor portion from below; Equipped with When directions intersecting each other within the upper surface of the first floor portion are defined as a first intersecting direction and a second intersecting direction, the first tensile force transmission member transmits a tensile force between the ends of the first floor portion in the first intersecting direction and a tensile force between the ends of the first floor portion in the second intersecting direction, A fire-resistant structure in which the second tensile force transmission member transmits the tensile force between the ends of the second floor section in the first cross direction and the tensile force between the ends of the second floor section in the second cross direction.

2. The fire-resistant structure according to claim 1 , further comprising a reinforcing steel bar disposed near a joint between the first floor section and the second floor section.

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