Floor structure and construction method of floor structure

Abstract

To provide a floor structure whose construction period is reduced.SOLUTION: A floor structure 10 includes multiple beams 12, 13, support members 14 erected on the multiple beams 12, 13, and a floor slab 15 with concrete 15a, which is supported by the support members 14 when the concrete 15a is cast and is supported by the multiple beams 12, 13 after the concrete 15a has cured, and the support members 14 remain in place even after the concrete 15a has cured.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a floor structure and a method for constructing a floor structure. [Background technology]

[0002] Conventionally, buildings having a floor structure in which a floor slab is supported by a plurality of beams are known (see, for example, Patent Documents 1 and 2). The floor slab includes concrete or the like. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Utility Model Application Publication No. 62-193046 [Patent Document 2] JP 2001-317148 A Summary of the Invention [Problem to be solved by the invention]

[0004] In the construction of floor structures, when pouring ready mixed concrete (concrete) for the floor slab of a certain floor, vertical supports such as pipe supports (pillars) may be erected on the floor slab of the floor immediately below that floor (hereinafter also referred to as the lower floor). These vertical supports support the ready mixed concrete from below. After a certain period of time, the fresh concrete hardens and turns into concrete, the floor slab is laid, and the vertical supports supporting the concrete are then removed.

[0005] However, while the ready-mix concrete is hardening, vertical supports are placed on the lower floors, which makes it difficult to proceed with interior construction work, equipment installation, and other work on the lower floors, resulting in a longer construction period for the floor structure.

[0006] In light of this, for example, Patent Document 1 proposes a support beam that is erected horizontally in an attempt to secure work space on the floor below. However, since the support beam is a temporary material, it needs to be removed after the concrete hardens, which may increase the workload on site. Also, Patent Document 2 proposes a structure in which a lower layer's casting beam is suspended by a hanging support member from an upper layer's casting beam. This is an attempt to safely and easily perform the construction and dismantling work of conventional vertical supports, which was dangerous and complicated work. However, there is a possibility that the hanging support member will compress the working space of the lower layer. In addition, after removing the hanging support member after the concrete has hardened, additional concrete must be poured near the joint between the hanging support member and the lower layer's casting beam, which is time-consuming from the perspective of concrete procurement.

[0007] The present invention has been made in consideration of such problems, and has an object to provide a floor structure that shortens the construction period, and a construction method for this floor structure. [Means for solving the problem]

[0008] In order to solve the above problems, the present invention proposes the following means. (1) Aspect 1 of the present invention is a floor structure comprising a plurality of beams, supporting members installed on the plurality of beams, and a floor slab having concrete, which is supported by the supporting members when the concrete is poured and is supported by the plurality of beams after the concrete has hardened, wherein the supporting members remain in place even after the concrete has hardened.

[0009] In this invention, when the concrete is poured, it is supported by supports installed on multiple beams. Therefore, for example, the supports are prevented from interfering with the construction work on the floor directly below the concrete, and the construction period for the floor structure can be shortened. In addition, after the concrete hardens and the floor slab is constructed, the floor slab is supported by a number of beams. At this time, since the support members are still in place even after the concrete hardens, the floor slab can be supported by the support members.

[0010] (2) Aspect 2 of the present invention may be the floor structure described in (1), in which the support members are not provided with a fire-resistant coating. In the present invention, the supporting members are not required to have fire resistance like beams, and therefore can be used without providing fire-resistant coating to the supporting members.

[0011] (3) A third aspect of the present invention may be the floor structure described in (1) or (2), in which the support member is an H-shaped cross-section member made of steel. In this invention, the floor slab can be supported by the support members with efficiently increased rigidity at room temperature, which contributes to suppressing flexural deformation, cracks, and vibrations of the floor slab.

[0012] (4) A fourth aspect of the present invention may be a floor structure as described in (3), in which the H-shaped cross-section member has an upper flange, a lower flange, and a web, and the floor slab is integrated with the H-shaped cross-section member via a connecting member installed on the upper flange, and is configured to satisfy formula (1). however, s d is the distance from the top surface of the floor slab to the center of gravity of the H-shaped section member, B c is the effective width of the floor slab, t c is the thickness of the floor slab, n is the Young's modulus ratio between the H-shaped section member and the concrete of the floor slab, A is the cross-sectional area perpendicular to the material axis direction of the H-shaped section member, t w is the thickness of the web, E is the Young's modulus of the H-section member, F is the design strength of the H-section member, t f are the thicknesses of the upper flange and the lower flange, respectively.

[0013]

number

[0014] In this invention, by setting formula (1) to be satisfied, the neutral axis of the H-shaped section member (support member) and the floor slab as a whole moves toward the floor slab from the central axis of the H-shaped section member, preventing the occurrence of shear buckling and local buckling due to compression in the web. Therefore, for example, an H-shaped section member with a relatively thin web thickness can be effectively used in a floor structure, and the mass of the H-shaped section member can be reduced while ensuring the specified bending rigidity and bending strength of the floor structure.

[0015] (5) Aspect 5 of the present invention relates to a tensile strength σ u The floor structure may be the one described in (4) above, which is configured to satisfy formula (2). 550≦σ u ≦1000 (2) In the present invention, the thicknesses of the upper flange, lower flange and web of the support member, which is an H-shaped cross-section member, can be made thinner.

[0016] (6) A sixth aspect of the present invention may be a floor structure as described in (3), in which each of the plurality of beams is an H-shaped cross-section member made of steel, and the thickness of the H-shaped cross-section member of the support member is thinner than the thickness of the H-shaped cross-section member of the plurality of beams. In this invention, the support members are not required to have the fire resistance strength that beams do, so the mass of the steel frame used for the support members can be reduced.

[0017] (7) A seventh aspect of the present invention may be a floor structure according to any one of (1) to (6), in which blast-furnace slag cement is used for the concrete. This invention makes it possible to reduce the amount of carbon dioxide emitted during construction of the floor structure, compared to when only Portland cement is used for the concrete.

[0018] (8) Aspect 8 of the present invention is a method for constructing a floor structure, comprising a pouring step in which the concrete is supported by supporting members erected on a plurality of beams during pouring, and a hardening step in which the concrete is hardened to form a floor slab having the concrete and supported by the plurality of beams.

[0019] In this invention, the concrete is supported by supports installed on multiple beams during the casting process, which prevents the supports from interfering with construction work on the floor directly below the concrete, and shortens the construction period for the floor structure. In addition, after the concrete hardens and the hardening process in which the floor slab is formed, the floor slab is supported by a plurality of beams. At this time, the floor slab can be supported by a support member. Effect of the Invention

[0020] The floor structure and floor structure construction method of the present invention can shorten the construction period. [Brief description of the drawings]

[0021] [Figure 1] 1 is a cross-sectional view showing a schematic diagram of a building in which a floor structure according to one embodiment of the present invention is used. [Diagram 2] 2 is a cross-sectional view taken along line A1-A1 in FIG. [Diagram 3] 4 is a flowchart showing a construction method for a floor structure in one embodiment of the present invention. [Figure 4] 1 is a cross-sectional view illustrating a construction method for a floor structure according to one embodiment of the present invention. FIG. [Diagram 5] FIG. 1 is a diagram showing a cross-sectional shape of an analysis model used in a heat conduction analysis in analysis study 1. [Figure 6] FIG. 13 is a diagram showing the results of a thermal conduction analysis. [Figure 7] FIG. 1 is a diagram showing an analytical model used in a thermal stress analysis. [Figure 8] FIG. 13 is a diagram showing the results of a thermal stress analysis. [Figure 9]FIG. 2A is a cross-sectional view of the main part of the beam-floor structure examined in analysis study 2, and FIG. 2B is a diagram explaining the stress distribution acting thereon, etc. [Figure 10] FIG. 1 is a diagram showing a practically preferable range of cross-sectional area ratio and outer dimension height. [Figure 11] FIG. 1 is a diagram showing the relationship between bending strength ratio and moment of inertia. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0022] Hereinafter, an embodiment of a floor structure and a method for constructing a floor structure according to the present invention will be described with reference to Figs.

[0023] [1. Floor structure configuration] As shown in FIG. 1, a floor structure 10 of this embodiment is used in a building 1. There is no limitation on the configuration of the building 1. For example, the building 1 is a two-story building. The building 1 comprises a floor structure 10, a lower floor slab 20, a roof 25 and walls (not shown). 1 and 2, the floor structure 10 has a plurality of columns 11, a plurality of main girders (beams) 12, a sub-girder (beam) 13, a support member 14, and an upper floor slab (floor slab) 15. That is, in this example, the plurality of beams has a plurality of main girders 12 and sub-girders 13. The girder 12 referred to here means a beam having both ends directly joined to the columns 11. The secondary beam 13 referred to here means a beam having both ends directly joined to the girder 12.

[0024] For example, the pillar 11 is made of H-shaped steel and extends in the vertical direction. The lower end of the pillar 11 is supported by a supporting member F such as the ground. The pillar may be made of reinforced concrete or steel-reinforced concrete. The multiple pillars 11 are spaced apart from one another along a horizontal plane. For example, each of the multiple girders 12, sub-girders 13, and support members 14 is formed of H-shaped steel (H-shaped cross-section member) made of steel. The support members 14 are formed of a first H-shaped cross-section member, and the multiple girders 12 and sub-girders 13 are formed of a second H-shaped cross-section member. The first H-shaped cross-section member and the second H-shaped cross-section member may be different from each other. The main girder 12, the secondary girder 13, and the support member 14 each extend along a horizontal plane.

[0025] As shown in Fig. 2, the girder 12 has a flange 12a, a flange 12b, and a web 12c. The flanges 12a, 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 flanges 12a and 12b, and is connected to the center of the flange 12a in the width direction and the center of the flange 12b in the width direction. The girder 12 is erected on a plurality of columns 11. Both ends of the girder 12 are joined to vertical middle parts of the plurality of columns 11. For the joining, bolt joining, welding joining, or the like is used. For example, in a plan view, the multiple girders 12 have a rectangular outer edge shape.

[0026] For example, the minor beam 13 is formed in a shape substantially similar to that of the major beam 12, and has a flange 13a, a flange 13b, and a web 13c. The cross-sectional shape of the minor beam 13 perpendicular to the longitudinal direction is smaller than the cross-sectional shape of the major beam 12 perpendicular to the longitudinal direction. The minor beam 13 is supported by the plurality of main beams 12. Both ends of the minor beam 13 are joined to the plurality of main beams 12.

[0027] A fireproof coating may be applied to the multiple main girders 12 and minor girders 13. For example, rock wool, glass wool, etc. may be used as the fireproof coating. In a plan view, a section R1 is defined by the central axes (and their extensions) or the outer end lines (and their extensions) of the multiple girders 12. In addition, the section may be defined, when viewed in a plan view, by the central axes (and their extensions) or outer end lines (and their extensions) of multiple main beams 12, and the central axes (and their extensions) or outer end lines (and their extensions) of secondary beams 13.

[0028] For example, the support member 14 is formed in a shape similar to that of the sub-beam 13, and has a flange (upper flange) 14a, a flange (lower flange) 14b, and a web 14c. The cross-sectional shape of the support member 14 perpendicular to the longitudinal direction is smaller than the cross-sectional shape of the sub-beam 13 perpendicular to the longitudinal direction. That is, the thickness of the flanges 14a, 14b of the H-shaped steel of the supporting member 14 is thinner than the thickness of the flanges 12a, 12b, 13a, 13b of the H-shaped steel of the main girder 12 and the sub-girder 13. The thickness of the web 14c of the H-shaped steel of the supporting member 14 is thinner than the thickness of the webs 12c, 13c of the H-shaped steel of the main girder 12 and the sub-girder 13. The support member 14 is installed on a plurality of main girders 12. Both ends of the support member 14 are joined to the plurality of main girders 12. That is, in this example, the support member 14 is disposed along the minor girders 13. The support member 14 is disposed within the section R1 in a plan view.

[0029] In this example, no fireproof coating is provided on the support members 14. However, the support members 14 may be provided with a fireproof coating.

[0030] For example, the upper floor slab 15 is formed of a reinforced concrete slab. The upper floor slab 15 includes concrete 15a and a plurality of reinforcing bars (not shown). For example, the concrete 15a is formed into a plate shape having a rectangular shape in a plan view. The concrete 15a is produced by mixing cement, water, aggregate, and admixture to produce ready-mix concrete, and then allowing it to harden for a certain period of time. This cement includes portland cement and blast furnace cement. For example, blast furnace cement is specified by the Japanese Industrial Standard JIS R 5211:2009 blast furnace cement (hereinafter referred to as JIS blast furnace cement). That is, blast furnace cement is used for the concrete 15a. The plurality of reinforcing bars are embedded in the concrete. For example, the plurality of reinforcing bars include a first reinforcing bar extending in a first direction along a horizontal surface and a second reinforcing bar extending in a second direction along the horizontal surface and intersecting the first direction.

[0031] The outer peripheral edge of the upper floor slab 15 is supported from below by a plurality of girders 12. The middle part of the upper floor slab 15 in plan view is supported from below by small girders 13 and supporting members 14. The upper floor slab may be formed of a composite slab in which concrete 15a and reinforcing bars are placed on a deck plate.

[0032] As shown in Fig. 1, the lower floor slab 20 is disposed on a support member F between a plurality of columns 11. The lower floor slab 20 is made of concrete or the like. The roof 25 is fixed to the upper ends of the multiple pillars 11. The walls are appropriately installed between the multiple pillars 11. In the building 1 constructed as described above, the first floor F1 is constructed between the lower floor slab 20 and the upper floor slab 15. The second floor F2 is constructed between the upper floor slab 15 and the roof 25.

[0033] The upper floor slab 15 is supported from below the concrete 15a by support members 14 via appropriate forms (temporary forms) when pouring the concrete 15a (fresh concrete before the concrete 15a hardens). After the concrete 15a hardens, the upper floor slab 15 is supported from below the concrete 15a by multiple girders 12 and minor girders 13. The support members 14 remain in place even after the concrete 15a has hardened.

[0034] [2. Floor structure construction method] Next, a description will be given of a construction method for the floor structure 10 configured as above. Fig. 3 is a flowchart showing a construction method S1 for a floor structure (hereinafter simply referred to as the construction method) in one embodiment of the present invention. First, in the pouring step (step S5 shown in FIG. 3), as shown in FIG. 4, concrete 15a (ready mixed concrete) is supported by support members 14 installed on a plurality of girders 12 when pouring the concrete 15a. At this time, a formwork or the like may be used as appropriate. When the pouring process S5 is completed, the process proceeds to step S7.

[0035] Next, in a hardening step S7, the concrete 15a is hardened to form an upper floor slab 15 having the concrete 15a and supported by a plurality of girders 12, as shown in FIG. When the hardening step S7 is completed, all steps of the construction method S1 are completed, and the floor structure 10 is constructed.

[0036] [3. Use of blast furnace slag cement] According to the JIS blast furnace cement, there are two types of blast furnace cement: Type B and Type C. Type B blast furnace cement contains more than 30% to 60% by mass of blast furnace slag. Type C blast furnace cement contains more than 60% to 70% by mass of blast furnace slag. According to the summary of LCI data for cement (see [9.] 1), as shown in Table 1, blast-furnace slag cement type B has 42% less CO2 than ordinary cement. 2 Reductions are possible.

[0037] [Table 1]

[0038] According to the Standard Specifications for Concrete (see [9.]2), as shown in Table 2, blast-furnace slag cement develops strength slower than ordinary cement and its curing period is about two days longer.

[0039] [Table 2]

[0040] However, by using support members that are permanently left in place (still in place after the concrete has hardened), the impact of the curing period on the construction schedule is reduced.

[0041] 4. Previous Issues As shown in Fig. 1, a conventional building 2 is provided with a vertical support 50 instead of the support member 14 of the building 1. In Fig. 1, the vertical support 50 is indicated by a two-dot chain line. In the pouring process of the conventional floor structure construction method, the concrete 15a was supported by the vertical support 50 such as a pipe support. The vertical support 50 was erected on the lower floor slab 20 of the first floor F1. This makes it difficult to proceed with the construction of the first floor F1, which results in a problem that the construction period for the floor structure becomes longer. Note that the vertical supports 50 are removed after the construction of the floor structure.

[0042] 5. Effects of this embodiment In contrast, in the floor structure 10 of this embodiment, when the concrete 15a is poured, the concrete 15a is supported by support members 14 erected on a plurality of girders 12, or on the girders 12 and the minor girders 13. This prevents the support members 14 from interfering with the construction on the first floor F1, for example, and shortens the construction period of the floor structure 10. Furthermore, the floor slab of the upper floor can be poured even if the floor slab of the lower floor has not yet hardened. In addition, after the concrete 15a hardens and the upper floor slab 15 is constructed, the upper floor slab 15 is supported by the multiple girders 12 and minor girders 13. At this time, since the support members 14 remain in place even after the concrete 15a hardens, the upper floor slab 15 can be supported by the support members 14.

[0043] The multiple beams include multiple main girders 12 and sub-girders 13. Therefore, the upper floor slab 15 after the concrete 15a has hardened can be supported by both the main girders 12 and sub-girders 13, which are beams. The upper floor slab 15 has a plurality of reinforcing bars, which can improve the tensile strength of the upper floor slab 15.

[0044] No fire-resistant coating is applied to the supporting members 14. Since the supporting members 14 are not required to have fire resistance like beams, they can be used without being coated with fire-resistant coating. The support members 14 are formed of H-shaped steel beams. Therefore, at room temperature, the upper floor slab 15 can be supported by the support members 14, which have efficiently increased rigidity, and bending deformation, cracks, and vibrations of the upper floor slab 15 can be suppressed.

[0045] The thickness of the H-shaped steel of the support member 14 is thinner than the thickness of the H-shaped steel of the multiple main girders 12 and sub-girders 13. Since the support member 14 is not required to have the fire resistance strength like the main girders 12 and sub-girders 13, the mass of the steel frame used for the support member 14 can be reduced. Blast-furnace cement is used for the concrete 15a. When blast-furnace cement is used, the curing period of the concrete 15a is about two days longer than when Portland cement is used, but in the floor structure 10 of this embodiment, the concrete 15a is permanently supported by the support members 14, so construction can proceed even if the concrete 15a is not hardened. Therefore, it is possible to reduce carbon dioxide emissions compared to when only Portland cement is used for the concrete, without extending the construction period.

[0046] In the construction method S1 of the present embodiment, in the pouring step S5, the concrete 15a is supported by support members 14 installed on a plurality of girders 12. Therefore, for example, in the construction on the first floor F1, the support members 14 are prevented from becoming an obstacle, and the construction period of the floor structure 10 can be shortened. After the concrete 15a hardens and the upper floor slab 15 is constructed in the hardening process S7, the upper floor slab 15 is supported by the multiple girders 12 and minor girders 13. At this time, the upper floor slab 15 can be supported by the support members 14, and bending deformation, cracks, and vibrations of the upper floor slab 15 can be suppressed.

[0047] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and changes, combinations, deletions, etc. of the configuration are also included within the scope that does not deviate from the gist of the present invention. For example, in the above embodiment, the H-shaped cross-section members forming the main girder 12, the secondary girder 13, and the support member 14 are not limited to H-shaped steel, but may be members whose cross sections perpendicular to the longitudinal direction are H-shaped. The floor structure 10 may have multiple joists 13, or may not have the joists 13. The support members 14 may be installed on the girders 12 and the joists 13, or may be installed on multiple joists 13. The support members 14 may be made of wood or concrete.

[0048] [6. Analysis and Consideration 1] Normally, a small beam needs to have a certain plate thickness because it needs to be fire-resistant. On the other hand, the support member 14 (steel member) of this embodiment does not need to have fire resistance, so a thin-walled H-shaped cross section can be used to reduce the weight of steel used. A thin-walled H-shaped cross section is, for example, a cross section whose web structural type, such as Case No. 2 shown in Table 3, is FD rank. The structural type is stipulated in the Building Standards Act Notification (Notification No. 1792, Article 3, 1980).

[0049] [Table 3]

[0050] The heat conduction analysis and thermal stress analysis described below were carried out for the cross sections shown in Table 3. Case No. 1 has a cross section shape standardized by JIS G 3192. In contrast, Case No. 2 has a cross section in which the second moment of area is approximately the same as Case No. 1, and the web and flange are made thinner by increasing the beam depth (cross-sectional depth of the beam). The general-purpose FEM analysis software "SAFIR" was used for the numerical analysis. In the analysis, a two-dimensional heat conduction analysis of the cross section of the beam (sub-beam, support member) was performed, and a three-dimensional thermal stress analysis of the beam member was performed based on the obtained cross-sectional temperature distribution. Note that Case No. 1 assumes a sub-beam, and Case No. 2 assumes a support member.

[0051] [6.1. Heat conduction analysis] Table 4 shows the materials and dimensions.

[0052] [Table 4]

[0053] Additionally, the floor slabs were assumed to be unreinforced (without rebar), and the fillets of the steel beams were ignored.The thermal properties of steel were taken from Eurocode 3 (see [9.] 3)), while the thermal properties of sprayed rock wool and ALC (Autoclaved Lightweight aerated Concrete: lightweight aerated concrete cured with high-temperature, high-pressure steam) were taken from the Fire Resistance Guidebook for Structural Materials (see [9.] 4)). The moisture content of both the sprayed rock wool and ALC was set to 5.0%. The 25mm-thick sprayed rock wool is a one-hour fire-resistant specification stipulated in the Building Standards Act. The heating history was based on the standard heating curve of ISO 834-1 (see [9.] 5)), and the conditions were set to heat the underside of the floor slab, the fireproof coating, and the surface of the steel beams. The standard heating curve is defined by equation (11). T = 345 × log 10 (8t+1)+20 ··(11) where T is the heating temperature (°C) and t is the heating time (min).

[0054] FIG. 5 shows the cross-sectional shape of the analysis model used in the heat conduction analysis. The floor structure 30 includes a fire-resistant beam 31 and a floor slab 36 . The fire-resistant performance beam 31 has a beam (beam to be analyzed) 32 and a fire-resistant coating 33. The beam 32 is a generalized version of a sub-beam, a support member, etc. The beam 32 has an upper flange 32a, a lower flange 32b, and a web 32c. The fireproof coating 33 covers the beams 32. The fireproof coating 33 is formed of sprayed rock wool. In this analysis, the heating history based on Eq. (11) was applied to the entire periphery of the steel member (the surface of the fire-resistant coating) and the underside of the ALC, and the boundary condition for the top surface of the ALC was set to room temperature (20°C). The results of the heat conduction analysis are shown in Figure 6. As can be seen from Figure 6, the upper and lower flanges were roughly the same for Cases No. 1 and 2, but the web was higher for Case No. 2. This is because the web in Case No. 2 is thinner and has a smaller heat capacity.

[0055] [6.2. Thermal stress analysis] In the thermal stress analysis, the temperature history obtained from the heat conduction analysis is reflected in the shell elements of the four junctions. Table 5 shows the various conditions for Cases No. 1 and 2.

[0056] [Table 5]

[0057] In this analysis, the strength reduction due to temperature rise of steel frame and the stress-strain relationship at high temperatures were based on Eurocode 3. The design strength F was set at 235N / mm 2 The external force was set so that the maximum bending stress was equal to the long-term allowable bending stress (=F / 1.5). The analytical model used in the thermal stress analysis is shown in Fig. 7. The analytical condition was a simply supported four-point bending. The unit of length in Fig. 7 is mm. For example, in FIG. 7, at the position indicated by the thick solid line as the boundary condition, the translational displacement (dx) in the x-axis direction is free (free=0), and the rotational displacement (rx) around the x-axis is fixed (fix=1). A load P was applied in the position and direction indicated by the arrow.

[0058] The results of the thermal stress analysis are shown in Figure 8. The beam was judged to have collapsed when the deflection displacement at the center of the beam span reached the specified deflection value. Here, the specified deflection value (δu) is an index given in ISO834 (see [9.] 3)) and is expressed by formula (12). δu=L 2 / (400H) ··(12) Here, L is the beam span (mm) and H is the beam depth (mm). In addition, the deflection standard value based on formula (2) is also applied in domestic fire-resistant construction certification tests. The thickness of the fire-resistant coating was set at 25 mm. As shown in Figure 8, Case No. 1 did not reach the prescribed deflection value one hour after heating, and therefore secured one-hour fire resistance. On the other hand, Case No. 2 collapsed in about 38 minutes, and therefore did not secure one-hour fire resistance. In the present invention, even a cross section that does not ensure a certain fire resistance, such as Case No. 2, can be used as a support member. In addition, the cross-sectional area ratio of Case No. 2 to Case No. 1 is 3538 mm 2 / 5100mm 2 = 0.694, it is possible to reduce the steel weight by about 30%.

[0059] [7. Analysis and Consideration 2] Here, the configuration of the floor structure 40 to be considered below will be described.

[0060] [7.1. Floor structure] As shown in FIG. 9(A), the floor structure 40 has a connecting member 41 in addition to each component of the floor structure 10. The upper floor slab 15 is integrated with the support member (H-shaped cross-section member) 14 via a connection member 41 installed on the upper flange 14a. For example, a headed stud is used as the connection member 41. Note that the connection member is not limited to the headed stud.

[0061] Here, the specifications of the floor structure 40 are defined as follows. Some of the following dimensions are not shown in the drawings. The thickness of the web 14c is t w The thickness of each of the flanges 14a and 14b is defined as t f The thickness of the upper floor slab 15 is specified as t (mm). c The inside height of the support member (H-shaped cross-section member) 14 is specified as d (mm). If the external height (beam depth) of the support member 14 is defined as H (mm), then (d=H-2×tf satisfies the relationship of Define the cross-sectional area perpendicular to the material axis direction of the support member 14 as A (mm 2 ). Define the distance from the upper surface of the upper floor slab 15 to the centroid of the support member 14 as s d (mm).

[0062] Define the Young's modulus of the support member 14 as E (N / mm 2 ). Define the Young's modulus ratio between the support member 14 and the concrete 15a of the upper floor slab 15 as n (-). Here, the Young's modulus ratio n is defined as (E / Young's modulus of the concrete 15a). Define the design reference strength of the support member 14 as F (N / mm 2 ). Define the height of the portion where the compressive force acts in the web 14c as d' (mm). Define the effective width of the upper floor slab 15 as B c (mm). Here, the effective width B c is the value defined in the various composite structure design guidelines and explanations in [9.] 6).

[0063] For example, define the length of the support member 14 as L, and the distance between two adjacent support members 14 in the width direction of the support member 14 as a. At this time, the effective width B c in [9.] 6) is obtained by, for example, equation (21) or (22). (when a < L) B c = (width of the support member 14) + 2 × (0.5 - 0.3a / L)a ·· (21) (when L ≤ a) B c = (width of the support member 14) + 2 × 0.2L ·· (22)

[0064] Note that for the effective width B c , the effective width (b eff ) defined on page 30 of [9.] 7) may be used.

[0065] 9(B) shows the position of the neutral axis L1 of bending of the support member 14 and the upper floor slab 15 as a whole (L1 is the vertical position of the neutral axis, but for convenience it is shown as the neutral axis L1). Also shown is the center of gravity L2 of the support member 14 (L2 is the vertical position of the center of gravity, but for convenience it is shown as the center of gravity L2).

[0066] [7.2. Consideration of conditions under which local buckling due to compression does not occur in the web of a support member] In the following, a case where a compressive force acts on the web 14c of the supporting member 14 as shown in FIG. 9(A) will be considered.

[0067] The condition for local buckling not to occur in the web 14c (for it to be designed as effective across the entire cross section) is when the width-to-thickness ratio of the width (height) of the web 14c on which the compressive force acts is less than or equal to the width-to-thickness ratio specified value based on [9.] 8). In this embodiment, the compression area of ​​the web 14c is treated as a "plate supported at two edges and subjected to pure compression" as shown in FIG. 9(B), and conditions under which local buckling does not occur in this portion are organized. Here, the shape of the stress distribution (stress block) in the compressed region of the web 14c is triangular, but in this embodiment, the shape of the stress distribution is replaced with a rectangle as a condition for receiving a uniform compressive force, so that a safe evaluation is made. The range of width-thickness ratio of the web 14c for which local buckling does not occur in a plate supported on two edges under pure compression is given by equation (26).

[0068]

number

[0069] At this time, the range of height d' of the portion of web 14c where compressive force acts, in which local buckling does not occur in the region of web 14c where compressive force acts, is given by equation (27) from equation (26).

[0070]

number

[0071] The distance x that satisfies equation (27) n The range is given by equation (28).

[0072]

number

[0073] According to [9.] 6), the dimensional conditions for the support member 14 and the upper floor slab 15 to satisfy equation (28) are given by equation (29).

[0074]

number

[0075] That is, it is preferable that the floor structure 40 is configured so as to satisfy the formula (29). In addition, the tensile strength σ of the support member 14 (H-shaped cross-section member) u (N / mm 2 ) is preferably configured to satisfy formula (32). 550≦σ u ≦1000 (32) In this case, the support member 14 is made of so-called high-strength steel.

[0076] [7.3. Verification of the weight reduction effect of support components] Below, an example of the high-strength thin-walled support member 14 that is the subject of [7.] is shown. Here, we take as an example a high-strength thin-walled H-section member having a second moment of area equal to or greater than that of a rolled H-section member (other than general-purpose products; JIS section) specified in [9.] 9), and examine whether or not local buckling of web 14c occurs based on equation (29). The cross-sectional shape of the support member 14 is described on pages 18 and 19 of [9.] 9). The design strength F of high-strength thin-walled H-shaped cross-section members is 780N / mm 2 , Young's modulus is 205000N / mm 2 The Young's modulus ratio was set to 15 following [9.]6).

[0077] When equation (29) is satisfied, local buckling will not occur, so even if the provision of [9.] 8) applies, the entire cross section of the support member 14 can be considered effective. Table 6 shows the results of the study when the thickness of the upper floor slab 15 is 100 mm, 150 mm, and 200 mm, and the effective width is 1500 mm. Table 6 shows the results of the study on local buckling due to compression.

[0078] [Table 6]

[0079] For example, in sample No. 1, ( s d≦ s d'), that is, formula (29) is satisfied ("OK" in the column labeled "Judgment"), so it was found that no local buckling due to compression occurred in web 14c of sample No. 1. In Table 6, all samples except for sample Nos. 22, 28, and 29 satisfy formula (29), so local buckling due to compression does not occur in the web 14c of those samples, and the entire cross section of the web 14c can be considered effective. Note that when the neutral axis L1 is inside the floor slab 20, the entire cross section can be considered effective regardless of formula (29). The high-strength, thin-walled support member 14 that was the subject of this study has a cross-sectional area that is 30 to 50% smaller than the rolled H-section member specified in [9.] 9) that it is replacing. Therefore, while maintaining the same moment of inertia, the weight of the support member 14 can be reduced by up to 50% by reducing the thickness. In addition, it is possible to design the entire cross section of the web 14c to be effective, making it possible to maximize the benefits of high strength.

[0080] In the study in [7.], the floor structure 40 is equipped with a connecting member 41 and is configured to satisfy formula (29). Therefore, the neutral axis L1 of the support member 14 and the upper floor slab 15 as a whole moves toward the upper floor slab 15 side from the central axis of the support member 14, and the occurrence of shear buckling and local buckling due to compression in the web 14c is suppressed. Therefore, for example, an H-shaped cross-section member with a relatively thin web 14c can be effectively used in the floor structure 40, and the mass of the support member 14 can be reduced while ensuring a predetermined bending rigidity and bending strength for the floor structure 40.

[0081] [8. Supplementary Information] [8.1. Preferred range for practical use] Here, the practically preferable ranges for the floor structure targeted by the present invention are shown. Regarding formula (29), the following study was conducted using the specifications of the support member 14 and the upper floor slab 15 shown in Table 7 as an example.

[0082] [Table 7]

[0083] Here, the distance from the top surface of the upper floor slab 15 to the center of gravity of the support member 14 is s d is the outer height H of the support member 14 and the thickness t of the upper floor slab 15 c Using this, it can be expressed as equation (42).

[0084]

number

[0085] In addition, the cross-sectional area ratio of the support member 14 and the upper floor slab 15 is α(=B c ×t c / A)(-). Then, equation (29) can be expressed as equation (43) from equation (42).

[0086]

number

[0087] On the other hand, the range of exterior height H commonly used for H-shaped cross-section members for architecture is expressed by equation (44). 100≦H≦1200 (44)

[0088] Here, the lower limit of Eq. (44) is the minimum dimension of the H-shaped cross-section member specified in [9.] 9), and the upper limit of Eq. (44) is the maximum dimension of the H-shaped cross-section member for architecture currently in practical use. As a practical range of the cross-sectional area ratio α, the lower limit can be set from equation (43). The upper limit of equation (44) was set from a thin-walled H-section member having a moment of inertia equivalent to the minimum cross section of the H-section member specified in [9.] 9). The set results are shown in Table 8.

[0089] [Table 8]

[0090] In addition, the fillet portion of the thin support member 14 was ignored. The dimensions of the upper floor slab 15 shown in Table 7 were used to calculate the cross-sectional area ratio α.

[0091] From the above, the practically preferable range in this embodiment can be shown as in FIG. In addition, the thickness of the upper floor slab 15 is t c is 100mm, effective width B c was estimated at 1500mm. If the dimensions of the upper floor slab 15 are constant, the larger the cross-sectional area ratio α, the smaller the cross-sectional area of ​​the supporting member 14 and the smaller the mass of the supporting member 14. Therefore, in the consideration of [7.] and [8.], the more preferable range was determined to be the range in which the cross-sectional area ratio α is larger than that of [9.] 9). In other words, the range in which the mass of the support member 14 is smaller than that of the H-shaped steel specified by JIS. The design strength F is 325,780N / mm 2 is illustrated as an example.

[0092] In Figure 10, the design strength F is 780N / mm 2 A preferable range in this case is shown by hatched area R1. Samples No. 4 and No. 22 shown in Table 6 are plotted in Figure 10. Sample No. 22 has a design strength F of 780 N / mm 2 This case is outside the scope of application of the present invention, but the design strength F is 325N / mm 2 If so, it falls within the scope of application. Although the preferred range of this embodiment is smaller when the design strength F is high, it is advantageous in terms of strength calculation. This point will be described in detail in [8.2].

[0093] [8.2. Advantages of high strength] Here, the bending strength is examined using the strength as a parameter, using the samples shown in Table 6 as examples. The results of the examination are shown in Table 9. Table 9 shows the examination results for bending strength.

[0094] [Table 9]

[0095] Samples No. 31 to 62 in Table 9 have approximately the same moment of inertia as the H-shaped steel specified in [9.] 9), but their section modulus is approximately 5 to 31% smaller. On the other hand, by using high-strength steel, the bending strength can be ensured to be equal to or greater than that of [9.] 9). Here, the bending strength is the value (Z × F) obtained by multiplying the section modulus by the design strength, and the design strength of [9.] 9) is 235 N / mm 2 It was decided.

[0096] Figure 11 shows the bending strength ratio (M y / M y_JIS ) and the second moment of area. Here, M y_JIS M means the bending strength of H-shaped steel as specified in [9.] 9). ymeans the bending strength of the support member 14 having a second moment of area equivalent to that of the H-shaped steel specified in [9.] 9). For example, the four symbols (X, circle, square, and triangle) arranged vertically with the legend "equivalent to JIS248×124" indicate the design strength F of the support member 14 as 235, 325, 440, and 780 N / mm 2 This shows the bending strength ratio when the bending moment is changed as follows.

[0097] From Figure 11, the design strength F is 325N / mm 2 If so, the bending strength can be secured at the same level as that in Reference 4. In addition, if the design strength F is 440N / mm 2 If this is the case, a higher bending strength than that in Reference 4 can be ensured. As described above, the effect of this embodiment is more pronounced when high strength steel is used.

[0098] [9. Literature] 1) Overview of LCI data for cement: Japan Cement Association, "Overview of LCI data for cement," February 16, 2023, [Retrieved November 2, 2023], Internet <URL: https: / / www.jcassoc.or.jp / cement / 4pdf / jg1i_01.pdf> 2) Concrete Standard Specifications: Edited by the Japan Society of Civil Engineers, Concrete Committee, and Concrete Standard Specifications Revision Subcommittee, "Concrete Standard Specifications (Construction Edition)," 2017 3)Eurocode3:Design of steel structures Part 1-2:General rules- Structural fire design,prEN 1993-1-2,2005 4) Guidebook for Fire Resistance of Structural Materials: Edited by the Architectural Institute of Japan, "Guidebook for Fire Resistance of Structural Materials," Maruzen Publishing Co., Ltd., 2017 5)ISO 834-1:ISO 834-1, “Fire-resistance tests -Elements of building construction- Part 1: General requirements”, 1999.9 6) Edited by the Architectural Institute of Japan, "Guidelines and Commentary on Composite Structure Design," Maruzen Publishing Co., Ltd., 2023 7) “Eurocode 4: Design of composite steel and concrete structures - Part 1-1: General rules and rules for buildings”, 2004, Authority: The European Union Per Regulation 305 / 2011, Directive 98 / 34 / EC, Directive 2004 / 18 / EC 8) Architectural Institute of Japan (ed.), "Allowable Stress Design Criteria for Steel Structures," Maruzen Publishing Co., Ltd., 2019 9) Japan Standards Association, "JIS G 3192, Shape, Dimensions, Mass and Tolerances of Hot-Rolled Steel Sections," 2021 [Explanation of symbols]

[0099] 10,40 Floor structure 12 Large beam (beam) 13 Small beam (beam) 14 Supporting members 14a Flange (upper flange) 14b Flange (lower flange) 14c Web 15 Upper floor slab (floor slab) 15a Concrete 41 Connection member S1 Construction method (floor structure construction method) S5 Casting process S7 Curing process

Claims

1. A plurality of beams; A support member installed on the plurality of beams; a floor slab having concrete, the floor slab being supported by the support member when the concrete is poured and being supported by the beams after the concrete has hardened; Equipped with A floor structure, wherein the support members remain in place after the concrete has hardened.

2. 2. The floor structure of claim 1, wherein the support members are not provided with a fire-resistant coating.

3. 3. The floor structure according to claim 2, wherein the support member is an H-shaped cross-section member made of steel.

4. The H-section member has an upper flange, a lower flange, and a web; The floor slab is integrated with the H-shaped section member via a connecting member installed on the upper flange, The floor structure according to claim 3, which is configured to satisfy formula (1). however, ｓ d is the distance from the top surface of the floor slab to the center of gravity of the H-shaped section member, B ｃ is the effective width of the floor slab, t ｃ is the thickness of the floor slab, n is the Young's modulus ratio between the H-shaped section member and the concrete of the floor slab, A is the cross-sectional area perpendicular to the material axis direction of the H-shaped section member, t ｗ is the thickness of the web, E is the Young's modulus of the H-section member, F is the design strength of the H-section member, t ｆ are the thicknesses of the upper flange and the lower flange, respectively. [0010]

5. The tensile strength σ of the H-shaped cross-section member ｕ The floor structure according to claim 4, configured to satisfy formula (2). 550≦σ ｕ ≦1000 ・・(2)

6. Each of the plurality of beams is a steel H-shaped cross-section member, The floor structure according to claim 3 , wherein the thickness of the H-shaped section member of the support member is thinner than the thickness of the H-shaped section members of the plurality of beams.

7. 7. The floor structure according to claim 1, wherein the concrete is made of blast furnace cement.

8. A pouring step of supporting the concrete by support members installed on a plurality of beams when pouring the concrete; a curing step of hardening the concrete to form a floor slab having the concrete and supported by the plurality of beams; A construction method for floor structures.

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