Floor structure

Abstract

To provide a floor structure that reduces carbon dioxide emissions during construction, suppresses the neutralization of concrete after placing, and takes measures to address the time required for concrete curing.SOLUTION: A floor structure 10 comprises a plurality of beams 12, 13, a floor slab 15 supported by the plurality of beams and formed of reinforced concrete, and a zinc-based plated steel plate 14 fixed to an underside of the floor slab and having a plating layer containing 50% or more zinc by mass, and at least a part of binding material of the reinforced concrete contains steel slag or fine powder thereof.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a floor structure.

Background Art

[0002] In recent years, the need to reduce CO2 (carbon dioxide) emissions globally has been rapidly increasing. Among these, the CO2 emissions attributed to cement used in the construction and civil engineering fields account for a non-negligible proportion of the total emissions, and are estimated to be about 4 - 8% in the world and Japan respectively. As one of the countermeasures for reducing CO2 emissions, reduction of emissions attributed to cement is required.

[0003] As one of the countermeasures, utilization of cement derived from steel slag is considered (see, for example, Patent Documents 1 to 3). For example, it is known that by using Blast Furnace Cement Type B in which 60% or less of the binder such as cement is replaced with blast furnace slag, the CO2 emissions can be reduced by about 40%.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Patent Document 3

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, it is said that in concrete containing blast furnace slag, neutralization occurs earlier and it takes more time for hardening compared to concrete not containing blast furnace slag.

[0006] The present invention has been made in view of such problems, and aims to suppress the amount of carbon dioxide emissions during the production and construction of concrete, suppress the carbonation of the concrete after placement, and provide countermeasures against the time required for the hardening of the concrete, and provide a floor structure.

Means for Solving the Problems

[0007] In order to solve the above problems, the present invention proposes the following means. (1)Aspect 1 of the present invention includes a plurality of beams, a floor slab supported by the plurality of beams and formed of reinforced concrete, and a zinc-based plated steel sheet fixed to the lower surface of the floor slab and having a plating layer containing 50% or more of zinc by mass ratio, and at least a part of the binder of the reinforced concrete contains steel slag or its fine powder, which is a floor structure.

[0008] In the present invention, a zinc-based plated steel sheet having a plating layer containing 50% or more of zinc by mass ratio is fixed to the lower surface of the floor slab. As a result of intensive studies by the inventors, it has been found that the adhesion strength between this zinc-based plated steel sheet and concrete is higher than the adhesion strength between a steel sheet other than this zinc-based plated steel sheet and concrete. Therefore, due to the relatively high adhesion strength between the zinc-based plated steel sheet and concrete, peeling of the concrete and the plated steel sheet after placement can be suppressed, the range where the concrete contacts the atmosphere can be suppressed, and carbonation of the concrete can be suppressed. In addition, since at least a part of the binder of the reinforced concrete contains steel slag or its fine powder, for example, the amount of carbon dioxide emissions during the construction of the floor structure can be suppressed as compared with the case where the binder does not contain steel slag or its fine powder. Note that, for suppressing the peeling of the concrete and the plated steel sheet, mechanical joining such as drill screws, screws, nails, bolts, etc. may be used in combination.

[0009] (2)Aspect 2 of the present invention may be the floor structure according to (1), wherein, among the reinforcing bars of the reinforced concrete, the cover thickness of the reinforcing bar arranged at the uppermost position from the upper surface or side surface of the reinforced concrete is 25 mm or more. In the present invention, in concrete, the reinforcing bars arranged at positions where they are likely to be exposed to the atmosphere and where the concrete is likely to be carbonated can be made rust-resistant.

[0010] (3)Aspect 3 of the present invention may be the floor structure according to (1) or (2), wherein the content of the steel slag in the binder is more than 30% and 70% or less by mass ratio. In the present invention, the carbon dioxide emission during construction can be suppressed more efficiently.

[0011] (4)Aspect 4 of the present invention may be the floor structure according to any one of (1) to (3), comprising a sealing material arranged at the joint portion of the zinc-based galvanized steel sheet. In the present invention, by sealing the joint portion of the zinc-based galvanized steel sheet with a sealing material, the range where the concrete comes into contact with the atmosphere can be suppressed, and the progress of carbonation of the concrete can be suppressed.

[0012] (5)Aspect 5 of the present invention may be the floor structure according to any one of (1) to (4), comprising a first functional layer provided on the upper surface of the floor slab and coated with finishing mortar, alkaline paint, or neutral paint. In the present invention, the carbonation of the concrete from the upper surface of the floor slab can be suppressed by the first functional layer coated with finishing mortar, alkaline paint, or neutral paint.

[0013] (6)Aspect 6 of the present invention may be the floor structure according to any one of (1) to (5), wherein the reinforcing bars of the reinforced concrete are subjected to rust prevention treatment. In the present invention, the reinforcing bars of the reinforced concrete can be made rust-resistant.

[0014] (7)Aspect 7 of the present invention defines the distance from the upper surface of the floor slab to the central axis of the reinforcing bars in the reinforced concrete as hs, and when the thickness of the floor slab is defined as H, only the reinforcing bars satisfying formula (1) are subjected to rust prevention treatment. It may be the floor structure according to any one of (1) to (5). hs ≦ H / 2 ··(1) In this invention, in the concrete, rust prevention treatment can be efficiently performed only on the reinforcing bars arranged at positions where they are likely to come into contact with the atmosphere and where the concrete is likely to be carbonated.

[0015] (8)Aspect 8 of the present invention is such that the installation range of the studs joined to the flange of the beam and the reinforcing bars, which are at least a part of the reinforcing bars in the reinforced concrete and are arranged near the studs and fixed to the concrete in the reinforced concrete, is from one end in the material axis direction of the beam to the other end side, and is in a range of at least 0.1 times the length of the beam in the material axis direction and in a range of 0.4 times or less the length. It may be the floor structure according to any one of (1) to (7). In this invention, by utilizing the reinforcing bars, cracking of the concrete and conical failure around the studs are suppressed, the progress of carbonation inside the concrete and the progress of rusting of the reinforcing bars are suppressed, and by limiting the arrangement of the reinforcing bars to the structurally important beam ends, compared with the case where the installation range of the reinforcing bars is the entire length in the material axis direction of the beam, the number of reinforcing bars to be arranged can be efficiently reduced.

[0016] (9)Aspect 9 of the present invention is such that the zinc-based plated steel sheet is wavy or T-shaped protruding downward when viewed along the horizontal plane. It may be the floor structure according to any one of (1) to (8). In this invention, for example, the strength of the zinc-based plated steel sheet can be increased compared to a flat zinc-based plated steel sheet. It is said that in concrete containing steel slag or its fine powder as a part of the binder, the strength development may be slow in some cases, but by using the present zinc-based plated steel sheet, even when using such concrete, it is possible to appropriately ensure the strength during construction. Incidentally, there is also a conventional method in which the zinc-based plated steel sheet corresponding to the bottom plate 20 described later remains flat and truss bars are arranged thereon. Also in the present invention, such a measure may be taken to ensure the strength during construction.

[0017] (10)Aspect 10 of the present invention may be a floor structure according to any one of (1) to (9), wherein the nominal diameter of the reinforcing bars in the reinforced concrete is 10 mm or less. Generally, during a fire, due to gravity and the like acting on the floor slab, the floor slab deflects so as to be convex downward. At this time, the floor slab is supported by the reinforcing bars that have elongated due to the deflection of the floor slab transmitting tensile force. At this time, as a reaction force to the tensile force, a ring-shaped compressive stress field is formed around the perimeter of the floor slab near the beam, and corresponding compressive forces act on the concrete and reinforcing bars in the vicinity. When maintaining these mechanisms, ensuring the compressive stress of the concrete at high temperatures is also an important aspect. As a result of intensive studies by the inventors, it has been found that in concrete containing steel slag or its fine powder as part of the binder, the rate of decrease in strength at high temperatures compared to the strength at normal temperature of the concrete can be suppressed to a low level in some cases. Thereby, even when the diameter of the reinforcing bars used is suppressed to a certain extent or less, the fire resistance performance of the floor structure can be maintained equivalent to that of the conventional case.

[0018] (11)Aspect 11 of the present invention may be a floor structure according to any one of (1) to (10), wherein the plating layer contains aluminum in a mass ratio of 3% or more and 25% or less. In this invention, since the adhesion strength between the plating layer and the concrete is relatively high, it is possible to suppress the peeling of the concrete and the plated steel sheet after casting and to prevent air from entering between the concrete and the plated steel sheet, thereby suppressing the carbonation of the concrete.

[0019] (12)Aspect 12 of the present invention may be a floor structure according to any one of (1) to (11), wherein the zinc-based plated steel sheet has a second functional layer. In the present invention, the second functional layer can impart, for example, a function of further enhancing the adhesion strength to the zinc-plated steel sheet.

Advantages of the Invention

[0020] In the floor structure of the present invention, it is possible to suppress the amount of carbon dioxide emissions during the production and construction of concrete, and also to suppress the influence of the carbonation of the concrete after casting and the influence of the time required for the hardening of the concrete.

Brief Description of the Drawings

[0021]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0022] Hereinafter, a building equipped with the floor structure of one embodiment according to the present invention will be described with reference to FIGS. 1 to 6. As shown in FIG. 1, this building 1 includes a floor structure 10, a roof (not shown), and walls. The floor structure 10 has a plurality of columns (not shown), a plurality of large beams (beams) 12, small beams (beams) 13, a zinc-plated steel sheet 14, and a floor slab 15. In FIG. 1, only one of the plurality of large beams 12 is shown. That is, in this example, the plurality of beams include the plurality of large beams 12 and the small beams 13. In FIG. 1, the first functional layer 36 described later is shown with hatching. The main beam 12 mentioned here means a beam whose both ends are directly joined to columns. The secondary beam 13 mentioned here means a beam whose both ends are directly joined to the main beam 12.

[0023] For example, the columns are formed of welded fabricated steel box sections, cold-formed square steel tubes, H-shaped steel, etc., and extend vertically. The lower end of the column is supported by a supporting member (not shown) such as the ground. Note that the column may be formed of reinforced concrete or steel-reinforced concrete. A plurality of columns are arranged at intervals along a horizontal plane. For example, each of the plurality of main beams 12 and secondary beams 13 is formed of welded fabricated steel H-shaped steel or rolled H-shaped steel. The plurality of main beams 12 and secondary beams 13 each extend along a horizontal plane.

[0024] The main beam 12 has a flange 12a, a flange 12b, and a web 12c. The flange 12a, the flange 12b, and the web 12c are each formed in a flat plate shape. The flange 12a is disposed above the flange 12b. The web 12c is disposed between the flange 12a and the flange 12b and is connected to the center in the width direction of the flange 12a and the center in the width direction of the flange 12b, respectively. A gusset plate 16 is fixed to the web 12c etc. of the main beam 12 by welding or the like. Both ends of the main beam 12 are joined to a plurality of columns. Bolt joining, welding joining, etc. are used for the joining. For example, in plan view, the plurality of main beams 12 exhibit a rectangular outer edge shape.

[0025] For example, the secondary beam 13 is formed in a shape substantially similar to the main beam 12 and has a flange 13a, a flange 13b, and a web 13c. The cross-sectional shape perpendicular to the longitudinal direction of the secondary beam 13 is smaller than the cross-sectional shape perpendicular to the longitudinal direction of the main beam 12. Both ends of the secondary beam 13 are joined to a plurality of main beams 12 via a gusset plate 16 or the like. For example, the secondary beam 13 is arranged along a part of the plurality of main beams 12. The upper surface of the flange 13a of the secondary beam 13 is arranged at the same height as the upper surface of the flange 12a of the main beam 12. A plurality of studs 17 are joined to the flange 13a of the secondary beam 13. The plurality of studs 17 are arranged at intervals along the longitudinal direction of the secondary beam 13.

[0026] Note that the plurality of columns, the plurality of main beams 12, and the secondary beam 13 may be provided with a fire-resistant coating. For example, for the fire-resistant coating, rock wool, glass wool, etc. can be used. In this case, for example, the thickness of the fire-resistant coating is set in accordance with the "Construction Quality Management Guidelines for Sprayed Rock Wool Coated Fire-Resistant Structures (Rock Wool Industrial Association Spraying Subcommittee)". When 1-hour fire resistance is required for the main beam 12 etc., the thickness of the fire-resistant coating is set to 25 mm. Similarly, when 2-hour fire resistance is required for the main beam 12 etc., the thickness of the fire-resistant coating is set to 45 mm. When 3-hour fire resistance is required for the main beam 12 etc., the thickness of the fire-resistant coating is set to 60 mm. However, if it is recognized through separate consideration, it may be set to be less than this thickness.

[0027] In plan view, a section R1 is defined by the central axis (and its extension line) or the outer end line (and its extension line) of the plurality of main beams 12, and the central axis (and its extension line) or the outer end line (and its extension line) of the secondary beam 13. Note that the section may be defined by the central axis (and its extension line) or the outer end line (and its extension line) of the plurality of main beams 12 etc. in plan view.

[0028] As shown in FIGS. 1 and 2, the zinc-plated steel sheet 14 is a composite deck. The zinc-plated steel sheet 14 is a deck plate formed of a zinc-plated steel sheet. The zinc-plated steel sheet 14 may have a bottom plate 20 and two side plates 21, 22, or the bottom plate and the side plates may be formed separately. Further, part of the functions of the bottom plate 20 may be replaced by the flanges of the H-shaped steel of the beam. In this case, since the area ratio in contact with the concrete is relatively small and the degree of influence on the neutralization of the concrete due to peeling is small, the flanges and side plates of the H-shaped steel may be zinc-based plated steel plates, or may be other materials such as rolled steel plates, aluminum, resin, etc.

[0029] Although not shown in the figure, the bottom plate 20 (zinc-based plated steel plate 14) has, as a layer structure, a steel plate (base material), a zinc-based plating layer (plating layer), and a second functional layer. The steel plate is formed in a flat plate shape. The zinc-based plating layers are provided on both surfaces of the steel plate respectively. The zinc-based plating layer contains 50% or more of zinc by mass ratio. The zinc-based plating layer contains three elements of zinc, aluminum, and magnesium. The zinc-based plating layer preferably contains aluminum in a mass ratio of 3% or more and 25% or less. The second functional layers are provided on the zinc-based plating layers (on the side opposite to the steel plate in the zinc-based plating layer) respectively. The second functional layer may be provided with a metal oxide film as a chemical conversion treatment for primary rust prevention, or may be provided by phosphate treatment as a chemical conversion treatment for improving paint adhesion, etc., or may be provided by a resin-containing film, etc. as a chemical conversion treatment for improving adhesiveness, etc.

[0030] The bottom plate 20 (zinc-based plated steel plate 14) is formed in a wavy shape when viewed along the horizontal plane. For example, the bottom plate 20 has a rectangular shape in plan view. The bottom plate 20 has two opposing first sides 20a and two opposing second sides 20b in plan view. In FIG. 1, only one of the first side 20a and the second side 20b is shown. The outer peripheral edge of the bottom plate 20 is disposed on a plurality of large beams 12 and small beams 13. In other words, the plurality of large beams 12 and small beams 13 support the outer peripheral edge of the bottom plate 20 from below this outer peripheral edge.

[0031] As for the layer structure, the side plates 21 and 22 are configured in the same manner as the bottom plate 20. As shown in FIG. 1, the two side plates 21 cover the first side 20a from the outside and project upward and downward from the first side 20a, respectively. The two side plates 22 project upward from the second side 20b. The side plate 22 is adjacent to the side plate 21. A joint portion 23 of the zinc-based plated steel sheet 14 is formed between the side plate 21 and the side plate 22. A sealing material (sealing material) 24 is disposed at the joint portion 23. Known silicone-based resins, polyurethane resins, etc. can be used for the sealing material 24. The sealing material 24 seals the joint portion 23. Note that the sealing position is not limited to the above-mentioned 23 between the side plate 21 and the side plate 22, and may be provided at the joint portion within each plate of the side plate or the bottom plate. For example, the sealing material 24 is preferably disposed at a position to avoid contact between the concrete 27 and the atmosphere.

[0032] The floor slab 15 is formed of reinforced concrete. The reinforced concrete has the concrete 27 and a plurality of reinforcing bars 28. The concrete 27 is formed in a plate shape having a rectangular shape in plan view. The concrete 27 is disposed along the horizontal plane. The concrete 27 is manufactured by solidifying the fresh concrete obtained by mixing the aggregate, the binder, and water and integrating them. The binder is the binder of the concrete 27 (reinforced concrete). For the aggregate, crushed stone, gravel, mountain sand, etc. are used. The binder includes cement, cement derived from steel slag, steel slag, etc. That is, at least a part of the binder contains steel slag or its fine powder. It is preferable that the binder contains steel slag as fine powder.

[0033] It is preferable that the content of the steel slag or its fine powder in the binder is more than 30% and 70% or less by mass ratio. For example, the fine powder of steel slag is the fine powder corresponding to blast furnace slag fine powder 3000 to blast furnace slag fine powder 8000 defined in JIS A 6206:2013, blast furnace slag fine powder for concrete.

[0034] The steel slag may be blast furnace slag produced in the steelmaking process in a blast furnace or steelmaking slag produced in the steelmaking process in a converter.

[0035] Here, the directions along the upper surface of the concrete 27 (floor slab 15) and perpendicular to each other are defined as the first direction X and the second direction Y. For example, the first direction X and the second direction Y are the directions along each side of the concrete 27 in plan view. The small beam 13 extends in the first direction X. The plurality of reinforcing bars 28 includes a plurality of first reinforcing bars 32, a plurality of second reinforcing bars 33, and a plurality of reinforcing bars 34. The plurality of first reinforcing bars 32 extend in the first direction X and are arranged at intervals from each other in the second direction Y. The plurality of second reinforcing bars 33 extend in the second direction Y and are arranged at intervals from each other in the first direction X. For example, the plurality of second reinforcing bars 33 are in contact with the plurality of first reinforcing bars 32 from below the plurality of first reinforcing bars 32. The plurality of first reinforcing bars 32 and the plurality of second reinforcing bars 33 are arranged in the concrete 27. In this example, the plurality of first reinforcing bars 32 form one layer, and the plurality of second reinforcing bars 33 form one layer. The plurality of first reinforcing bars 32 are the reinforcing bars arranged at the uppermost position among the plurality of reinforcing bars 28 of the reinforced concrete.

[0036] Here, the distance from the upper surface of the floor slab 15 to the central axes of the plurality of first reinforcing bars 32 and the plurality of second reinforcing bars 33 is defined as hs. The thickness of the floor slab 15 is defined as H. At this time, only the reinforcing bars that satisfy the formula (1) are subjected to rust prevention treatment. hs ≦ H / 2 ··(1) For the rust prevention treatment of the reinforcing bars 32 and 33, known materials such as rust conversion type rust prevention materials, resin-based rust prevention materials, and polymer cement-based materials can be used. The cover thickness of the plurality of first reinforcing bars 32 from the upper surface or side surface of the reinforced concrete (concrete 27) is preferably 25 mm or more. Note that all of the plurality of first reinforcing bars 32 and the plurality of second reinforcing bars 33 may be subjected to rust prevention treatment. The nominal diameters of the plurality of first reinforcing bars 32 and the plurality of second reinforcing bars 33 may be 10 mm or less.

[0037] As shown in FIGS. 1 to 3, the plurality of reinforcing bars 34 are formed by bending deformed steel bars at the central portion in the length direction so that the overall shape is U-shaped. As shown in FIG. 3, that is, the reinforcing bar 34 has a bent portion 34a and two end portions 34b provided at both ends of the bent portion 34a. As shown in FIG. 2, studs 17 are arranged inside the bent portion 34a. That is, the reinforcing bar 34 is arranged in the vicinity of the studs 17. The two end portions 34b extend from the bent portion 34a toward the first side in the second direction Y that is orthogonal to the direction in which the small beam 13 extends.

[0038] Note that the configuration of the reinforcing bars and their peripheral members is not necessarily limited to the above, and any specification may be used as long as the load acting on the floor slab 15 can be appropriately transmitted to the beams 12 and 13 via studs, plug welding, etc. The reinforcing bars may be round steel, and the overall shape of the reinforcing bars may be J-shaped, V-shaped, mesh-shaped, or L-shaped. A part may be welded to the beams 12 and 13. The upper portions of the plurality of reinforcing bars 34 and the plurality of studs 17 are arranged in the concrete 27 and are fixed to the concrete 27.

[0039] The installation range of the plurality of reinforcing bars 34 is preferably in the range of at least 0.1 times the length in the material axis direction of the small beam 13 and 0.4 times or less the length from one end to the other end side in the material axis direction (first direction X) of the small beam 13.

[0040] As shown in FIG. 1, the floor structure 10 includes a first functional layer 36 formed by applying finishing mortar (mortar), alkaline paint, or neutral paint on the upper surface of the floor slab 15. The bottom plate 20 of the zinc-based plated steel sheet 14 is fixed to the lower surface of the floor slab 15. That is, the bottom plate 20 is firmly and tightly attached to the lower surface of the floor slab 15, along with the influence of a zinc-based plating layer or the like. Similar to the bottom plate 20, the side plates 21 and 22 of the zinc-based plated steel sheet 14 are fixed to the side surfaces of the floor slab 15. The outer peripheral edge of the floor slab 15 in plan view is supported by a plurality of main beams 12 and secondary beams 13 via the zinc-based plated steel sheet 14. The ends of the plurality of first reinforcing bars 32 and the ends of the plurality of second reinforcing bars 33 extend to the portions supported by the plurality of main beams 12 and secondary beams 13 in the concrete 27.

[0041] For example, the zinc-based plated steel sheet 14 and the floor slab 15 are arranged corresponding to the partition R1 in plan view. The roof is fixed to the upper ends of a plurality of columns. The walls are appropriately installed between the plurality of columns.

[0042] When the building 1 configured as described above is used, the concrete 27 of the floor slab 15 is neutralized by carbon dioxide (CO2) or the like present in the atmosphere.

[0043] On the other hand, in the floor structure 10 of the present embodiment, a zinc-based plated steel sheet 14 having a zinc-based plating layer containing 50% or more of zinc by mass ratio is fixed to the lower surface of the floor slab 15. As a result of intensive studies by the inventors, it has been found that the adhesion strength between this zinc-based plated steel sheet and the concrete is higher than the adhesion strength between a steel sheet other than this zinc-based plated steel sheet and the concrete. Therefore, due to the relatively high adhesion strength between the zinc-based plated steel sheet 14 and the concrete 27, it is possible to suppress the peeling of the concrete 27 and the zinc-based plated steel sheet 14 after casting, and to suppress the entry of air between the concrete 27 and the zinc-based plated steel sheet 14, thereby suppressing the neutralization of the concrete 27. In addition, since at least a part of the binder of the reinforced concrete contains steel slag or its fine powder, for example, the carbon dioxide emission amount during the construction of the floor structure 10 can be suppressed compared to the case where the binder does not contain steel slag or its fine powder.

[0044] The zinc-plated steel sheet 14 fixed to the lower surface of the floor slab 15 makes it difficult for the concrete 27 to come into contact with the atmosphere, and the carbonation of the concrete 27 can be suppressed. Among the concretes in which at least a part of the binder contains steel slag, there is a characteristic that relatively few calcium ions are contained. For this reason, it is possible to suppress the corrosion of the zinc-plated steel sheet 14 fixed to the concrete 27.

[0045] The plurality of beams have a plurality of main beams 12 and secondary beams 13. For this reason, the floor slab 15 can be supported by both the main beam 12 and the secondary beam 13 which are beams. The content of the steel slag in the binder may be greater than 30% and 70% or less by mass ratio. In this case, the carbon dioxide emission amount during construction can be suppressed more efficiently.

[0046] The floor structure 10 includes a sealing 24. Thereby, the joint portion 23 of the zinc-plated steel sheet 14 can be sealed by the sealing 24, so that the range in which the concrete 27 comes into contact with the atmosphere can be suppressed, and the progress of the carbonation of the concrete 27 can be suppressed. The floor structure 10 includes a first functional layer 36. Therefore, the carbonation of the concrete 27 from the upper surface of the floor slab 15 can be suppressed by the first functional layer 36 to which the finishing mortar, the alkaline paint, or the neutral paint is applied.

[0047] In some cases, all of the plurality of first reinforcing bars 32 and the plurality of second reinforcing bars 33 are subjected to rust prevention treatment. In this case, all of the plurality of first reinforcing bars 32 and the plurality of second reinforcing bars 33 can be made difficult to rust. In some cases, only the reinforcing bars that satisfy the formula (1) are subjected to rust prevention treatment. In this case, in the concrete 27, it is possible to efficiently perform the rust prevention treatment only on the reinforcing bars arranged at relatively rust-prone positions.

[0048] The cover thickness of the plurality of first reinforcing bars 32 from the upper surface or side surface of the reinforced concrete is 25 mm or more. Therefore, among the concrete 27, the uppermost plurality of first reinforcing bars 32 arranged at positions where the concrete 27 is likely to be exposed to the atmosphere and neutralized can be made difficult to rust. The floor structure 10 has a plurality of studs 17 and a plurality of reinforcing bars 34. Thereby, by utilizing the reinforcing bars 34, cracking of the concrete 27 and conical failure around the studs 17 are suppressed, the progress of carbonation inside the concrete 27 and the progress of rusting of the reinforcing bars 34 are suppressed, and by limiting the arrangement of the reinforcing bars 34 to the beam ends that are structurally important, the number of the plurality of reinforcing bars 34 to be arranged can be efficiently reduced as compared with the case where the installation range of the plurality of reinforcing bars 34 is the entire length in the material axis direction of the secondary beam 13.

[0049] The bottom plate 20 is formed in a wavy shape when viewed along the horizontal plane. Therefore, the strength of the zinc-based plated steel sheet can be increased as compared with a flat zinc-based plated steel sheet. It is said that in concrete containing steel slag or its fine powder in a part of the binder, the strength development may be slow, but by using this zinc-based plated steel sheet, even when using such concrete, it is possible to appropriately ensure the strength during construction.

[0050] The nominal diameters of the plurality of first reinforcing bars 32 and the plurality of second reinforcing bars 33 may be 10 mm or less. Generally, during a fire, due to gravity and the like acting on the floor slab 15, the floor slab 15 deflects so as to be convex downward. At this time, the plurality of first reinforcing bars 32 and the plurality of second reinforcing bars 33 extended by the deflection of the floor slab 15 transmit tensile force, whereby the floor slab 15 is supported. At this time, as a reaction force of the tensile force, a ring-shaped compressive stress field is formed around the perimeter of the floor slab 15 near the beams 12, 13, and it is known that a corresponding compressive force acts on the concrete 27 and the reinforcing bars in the vicinity. When maintaining these mechanisms, ensuring the compressive stress of the concrete 27 at high temperatures is also an important perspective. As a result of the inventors' intensive studies, it has been found that in concrete containing steel slag or its fine powder in a part of the binder, the reduction rate of the strength at high temperature with respect to the strength at normal temperature of the concrete can be suppressed to be low as compared with normal concrete. Thereby, even when the diameter of the reinforcing bar 28 to be used is suppressed to a certain extent or less, the fire resistance of the floor structure 10 can be maintained equivalent to the conventional one.

[0051] The zinc-based plating layer may contain aluminum in a mass ratio of 3% or more and 25% or less. In this case, due to the relatively high adhesion strength between the zinc-based plating layer and the concrete 27, peeling between the concrete 27 and the zinc-based plated steel sheet 14 after placement can be suppressed, and it is possible to suppress air from entering between the concrete 27 and the zinc-based plated steel sheet 14, and neutralization of the concrete 27 can be suppressed. The zinc-based plated steel sheet 14 has a second functional layer. Therefore, the second functional layer can impart, for example, further improvement in adhesion strength to the zinc-based plated steel sheet 14.

[0052] The floor structure 10 of the present embodiment can be variously deformed in its configuration as described below. As in the floor structure 40 of the first modification shown in FIGS. 4 and 5, the bottom plate 42 of the zinc-based plated steel sheet 41 may be T-shaped protruding downward when viewed along the horizontal plane. In other words, the bottom plate 42 is T-shaped inverted in the vertical direction. The zinc-based plated steel sheet 41 is a formwork deck. Note that FIG. 4 does not show a plurality of reinforcing bars 28 and the like, and FIG. 5 shows only the bottom plate 42. As shown in FIG. 5, for example, the bottom plate 42 is configured by alternately arranging a plurality of plate pieces 43 and convex members 44 in the first direction X. As shown in FIG. 4, the end portion of the convex member 44 of the bottom plate 42 in the second direction Y may be crushed in the vertical direction. The end portion of this convex member 44 is disposed on the secondary beam 13.

[0053] The floor structure 50 of the second modification shown in FIG. 6 has a deck 51 with truss bars. Note that FIG. 6 shows only the main part of the floor structure 50. The deck 51 with truss bars has a zinc-based plated steel sheet 52 and truss bars 53 and 54 arranged above the zinc-based plated steel sheet 52. Even with floor structures 40, 50, etc. configured as described above, the same effects as the floor structure 10 of the present embodiment can be achieved.

[0054] As described above, although one embodiment of the present invention and its modifications have been described in detail with reference to the drawings, the specific configuration is not limited to this embodiment and its modifications, and changes, combinations, deletions, etc. of the configuration within the scope not departing from the gist of the present invention are also included. For example, in the above embodiment, the zinc-based plated steel sheet 14 may not have a second functional layer. The zinc-based plated steel sheet 14 may not have side plates 21 and 22. In this case, the zinc-based plated steel sheet is not fixed to the side surface of the floor slab 15.

[0055] Rust prevention treatment may not be applied to all of the plurality of first reinforcing bars 32 and the plurality of second reinforcing bars 33. The cover thickness of the plurality of first reinforcing bars 32 from the upper surface or side surface of the reinforced concrete may be less than 25 mm. The first functional layer may be provided not only on the upper surface of the floor slab but also on the side surface of the floor slab 15.

[0056] As a measure against cracking of the concrete 27, an expansion material may be appropriately arranged in the concrete 27. It is known that concrete 27 containing steel slag in at least a part of the binder has a higher ratio of strength at high temperature to strength at normal temperature than concrete not containing steel slag. Therefore, by using concrete 27, it is possible to ensure a longer fire resistance time of the floor slab even when using the same amount of fire-resistant reinforcing bars, or to reduce the amount of fire-resistant reinforcing bars of the floor slab. The floor structures 10 and 40 may have a plurality of joists 13 or may not have joists 13. The floor structures 10 and 40 may not have at least one of a plurality of columns, a plurality of studs 17, a ceiling 24, a plurality of reinforcing bars 34, and a first functional layer 36.

Description of Symbols

[0057] Floor structures of 10, 40, and 50 12 Girder (beam) 13 Small beam (beam) 14, 41, 52 Zinc-based plated steel sheets 17 Stud 23 Joint part 24 Sealing material 27 Concrete 28 Reinforcing bar 34 Reinforcing bar 36 First functional layer X First direction (material axis direction)

Claims

1. A plurality of beams, A floor slab supported by the plurality of beams and formed of reinforced concrete, A zinc-based plated steel sheet fixed to the lower surface of the floor slab and having a plating layer containing 50% or more of zinc by mass ratio, and comprising A floor structure, wherein at least a part of the binder of the reinforced concrete contains steel slag or fine powder thereof.

2. The floor structure according to claim 1, wherein the cover thickness of the rebar arranged at the uppermost position among the rebars of the reinforced concrete from the upper surface or side surface of the reinforced concrete is 25 mm or more.

3. The floor structure according to claim 1 or 2, wherein the content of the steel slag in the binder is more than 30% and 70% or less by mass ratio.

4. The floor structure according to claim 1 or 2, further comprising a sealing material arranged at the joint portion of the zinc-based plated steel sheet.

5. The floor structure according to claim 1 or 2, further comprising a first functional layer provided on the upper surface of the floor slab and coated with finishing mortar, alkaline paint, or neutral paint.

6. The floor structure according to claim 1 or 2, wherein the rebars of the reinforced concrete are subjected to rust prevention treatment.

7. When the distance from the central axis of the rebar of the reinforced concrete to the upper surface of the floor slab is defined as hs, and the thickness of the floor slab is defined as H, The floor structure according to claim 1 or 2, wherein only the rebars satisfying the formula (1) are subjected to rust prevention treatment. hs ≦ H / 2 ··· (1)

8. Studs joined to the flange of the beam, The installation range of the reinforcing bars, which are at least part of the reinforcing bars of the reinforced concrete and are arranged near the studs and fixed to the concrete of the reinforced concrete, is in the range of at least 0.1 times the length of the beam in the material axis direction from one end to the other end side in the material axis direction of the beam, and is in the range of 0.4 times or less of the length, for the floor structure according to claim 1 or 2.

9. The zinc-based plated steel sheet is wavy or T-shaped protruding downward when viewed along the horizontal plane, for the floor structure according to claim 1 or 2.

10. The nominal diameter of the reinforcing bars of the reinforced concrete is 10 mm or less, for the floor structure according to claim 1 or 2.

11. The plating layer contains aluminum in a mass ratio of 3% or more and 25% or less, for the floor structure according to claim 1 or 2.

12. The zinc-based plated steel sheet has a second functional layer, for the floor structure according to claim 1 or 2.

Images