Precast concrete foundation beam structure

Abstract

To provide a precast concrete foundation beam structure allowing efficient construction by integrally connecting a foundation beam constructed using a precast beam member and a structural slab and the like supported on the foundation beam.SOLUTION: A foundation beam structure 1 is the structure configured to arrange a foundation beam to connect pile head foundations 3 therebetween, to fix and support the peripheral part of a pressure-resistant plate 30 on lower parts of both side surfaces of the foundation beam, and to fix and support the peripheral part of a structural slab 40 on upper ends of both side surfaces of the foundation beam. The foundation beam has stirrup reinforcement bars 16 projecting from side surfaces and upper surfaces of precast beam members 10. A through slit 19 which a slab bar of the pressure-resistant plate 30 penetrates is formed in the lower end of the precast beam member 10. A pair of symmetrical precast beam members 10 with respect to a center line C in a beam width direction are placed on a bottom plate so as to face each other by securing a connection space S1 and a connection space S2, wherein concrete is installed at the site in the connection space S1, the connection space S2, the pressure-resistant plate 30, and the structural slab 40.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a precast concrete foundation beam structure, and in particular to a precast concrete foundation beam structure in which a plurality of half precast concrete members are used to easily join the upper and lower ends of the foundation beam to the ends of a structural slab, etc. [Background technology]

[0002] The foundation beam structure of a building is often constructed using the so-called conventional method, in which formwork is assembled on-site and concrete is poured in. However, because the conventional method increases the amount of work and construction time required, precast concrete is sometimes used not only for the superstructure but also for the substructure, the foundation beam structure.

[0003] When using precast concrete for foundation beam structures, the beam depth and beam span of the foundation beams become large in large buildings such as condominiums and buildings, so the weight of the precast concrete foundation beams becomes much heavier than that of precast concrete columns. For this reason, the lifting equipment used on site must be large enough to handle the weight of the foundation beams, which leads to increased construction costs.

[0004] In order to address these problems, the applicant has proposed a foundation beam structure in which two precast concrete beam members are integrated with cast-in-place concrete, thereby reducing the weight of each precast concrete beam member (Patent Document 1). [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2023-19966 A Summary of the Invention [Problem to be solved by the invention]

[0006] According to the invention described in Patent Document 1, the mass of the precast concrete beam members can be reduced, and there is no need to enlarge the lifting equipment at the precast member manufacturing plant. Even at the construction site of the foundation beams, the foundation beams can be constructed simply by pouring in-situ concrete between the precast concrete beam members and at the column side ends, thereby reducing labor in on-site foundation work.

[0007] Incidentally, when constructing a pit or the like within a foundation, it is often designed so that the periphery of the structural slab or pressure plate is supported by the foundation beam. The foundation beam structure disclosed in Patent Document 1 does not assume a structure in which the slab reinforcement of the structural slab or pressure plate is fixed within the foundation beam. Therefore, it is necessary to embed inserts for joining multiple slab reinforcements in advance into the precast concrete members that will become the foundation beams, or to construct the slab joints using conventional construction methods.

[0008] SUMMARY OF THE PRESENT EMBODIMENT An object of the present invention is to provide a foundation beam structure using precast concrete, which is integrally joined to the periphery of a slab such as an underground pit. [Means for solving the problem]

[0009] In order to achieve the above object, a precast concrete foundation beam structure according to a first invention is a foundation beam structure in which a foundation beam is arranged to connect the pile head foundations, a periphery of a pressure plate is fixedly supported to the lower part of both sides of the foundation beam, and a periphery of a structural slab is fixedly supported to the upper end of both sides of the foundation beam, the foundation beam has a first stirrup reinforcement having a part protruding from the side surface and the upper surface of the beam member, a plurality of through slits are formed at the lower end of the beam member through which a part of the slab reinforcement of the pressure plate passes, and the center line of the foundation beam in the beam width direction is A pair of symmetrically shaped precast concrete beam members are placed facing each other on a base plate with a first joint space in the beam width direction and a second joint space between the end face of the beam member and the pile head foundation, the slab reinforcement of the pressure plate passes through the through slits and the slab reinforcement of the structural slab is arranged beyond the upper end of the first precast concrete beam member into the first joint space, and concrete is poured on site into the first joint space, the second joint space, the pressure plate, and the structural slab.

[0010] The slab reinforcement of the structural slab is preferably arranged in the vicinity of the first stirrup reinforcement protruding from the upper surface of the foundation beam.

[0011] A precast concrete foundation beam structure as a second invention is a foundation beam structure in which a foundation beam is arranged to connect the pile head foundations, the periphery of a pressure plate is fixedly supported to the lower part of one side of the foundation beam, and the periphery of a structural slab is fixedly supported to the upper end of the side of the foundation beam where the pressure plate is fixedly supported, and the foundation beam has a first precast concrete beam member having a first stirrup bar partially protruding from the side surface of the beam member and the upper surface of the beam member, and a plurality of through slits formed at the lower end through which a portion of the slab bar of the pressure plate passes, and a second precast concrete beam member having a first stirrup bar partially protruding from the side surface of the beam member and a plurality of through slits formed at the lower end through which a portion of the slab bar of the pressure plate passes, and a second precast concrete beam member having second stirrup reinforcement bars and a second precast concrete beam member having second stirrup reinforcement bars are placed facing each other on the base plate so as to secure a first joint space in the beam width direction and a second joint space between the material end face of the beam member and the pile head foundation, the slab reinforcement of the pressure plate passes through the through slits and the slab reinforcement of the structural slab is placed beyond the upper end of the first precast concrete beam member into the first joint space, and concrete is poured on site into the first joint space, the second joint space, the pressure plate, and the structural slab.

[0012] It is preferable that the distance from the vertical rebar of the first stirrup bar in the first joint space to the outer surface of the first precast concrete beam member on the side where the structural slab is attached is greater than 1 / 2 the beam width of the foundation beam.

[0013] It is preferable that the end of the slab reinforcement of the pressure plate is bent near the vertical reinforcement of the first stirrup reinforcement in the first joint space and fixed to the concrete poured in place.

[0014] The depth of the second precast concrete beam member is preferably equal to the sum of the depth of the first precast concrete beam member and the thickness of the structural slab. Effect of the Invention

[0015] According to the present invention, a foundation beam made of precast concrete can be integrally joined to a structural slab supported by the foundation beam, which is expected to shorten construction time, reduce construction costs, and avoid the need for larger equipment at manufacturing plants for precast components. [Brief description of the drawings]

[0016] [Figure 1] FIG. 1(a) is a plan view showing a portion of a building foundation consisting of a foundation beam structure according to an embodiment of the present invention, (b-1) is an elevation view of the foundation beam 100 and pile head foundation 3,3 in (a), (b-2) is a cross-sectional view of the beam along the Ib2-Ib2 cross-sectional line, (c-1) is an elevation view of the foundation beam 200 and pile head foundation 4,4 in (a), and (c-2) is a cross-sectional view of the beam along the Ic2-Ic2 cross-sectional line. [Diagram 2] FIG. 2 is a cross-sectional view of a foundation beam structure according to one embodiment of the present invention taken along the IIa-IIa cross-sectional line of the foundation beam 100 in FIG. 1(b-1). [Diagram 3] Cross section (a) and partial side view (b) of a half-precast concrete beam member that constitutes part of the foundation beam structure shown in Figure 2. [Figure 4] FIG. 4 is a cross-sectional view of a foundation beam structure according to one embodiment of the present invention taken along the IVa-IVa cross-sectional line of the foundation beam 200 in FIG. 1(c-1). [Diagram 5] Cross section (a) and partial side view (b) of a half-precast concrete beam member that constitutes part of the foundation beam structure shown in Figure 4. [Figure 6] Construction sequence diagram for constructing the foundation beam structure shown in Figure 2 (Part 1: (a)-(c)). [Figure 7] Construction sequence diagram for constructing the foundation beam structure shown in Figure 2 (part 2: (d)-(f)). [Figure 8] Construction sequence diagram for constructing the foundation beam structure shown in Figure 4 (Part 1: (a)-(d)). [Figure 9] Construction sequence diagram for constructing the foundation beam structure shown in Figure 4 (Part 2: (e)-(g)). DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0017] The precast concrete foundation beam structure of the present invention will be described with reference to the attached drawings. In each drawing, for the sake of simplicity, the illustration of the web reinforcement and width stop reinforcement, which are not characteristic of the present invention, is omitted.

[0018] 1(a) to (c-2) show a part of the planar configuration of a foundation beam structure 1 composed of foundation beams 100, 200 and pile head foundations 3, 4 according to the present invention. The foundation beam structure 1 of the present invention is constructed with foundation beams 100, 200 composed of two types of cross-sectional shapes. The pile head foundations 3, 4 supporting the ends of the foundation beams 100, 200 are constructed as pile head joints of prefabricated piles P consisting of shell steel pipe concrete piles (SC piles) with a diameter of φ=1000 mm, for example, and a precast concrete column member 7 (hereinafter referred to as the precast column member 7) with a cross-sectional dimension of column depth 1200 mm×1200 mm is erected on the pile head foundations 3, 4 with a column span S=10 m.

[0019] [Outline of foundation beams 100 and 200] As shown in each figure of Figure 1 and Figure 2, the foundation beam 100 is constructed by installing identical half precast concrete beam members 10, 10 (hereinafter referred to as precast beam members 10) at predetermined positions on leveled concrete (not shown) with a predetermined gap between them, with stirrup bars 16 as first stirrup bars facing each other, and pouring foundation beam concrete 11 on site between the precast beam members 10, 10 (joint space S1 as the first joint space: described later), and pouring foundation beam concrete 12 on site between the beam end in the material axis direction and the pile head foundation 3 (joint space S2 as the second joint space: described later), thereby forming an integrated foundation beam.

[0020] As shown in each figure of Figure 1 and Figure 4, the foundation beam 200 is constructed by installing half precast concrete beam members 20, 25 (hereinafter referred to as precast beam members 20, 25) of different cross-sectional shapes at predetermined positions on leveled concrete (not shown) so that the stirrup reinforcements 26, 27 face each other, and pouring foundation beam concrete 21 on site between the precast beam members 20, 25 (joint space S1: described later), and pouring foundation beam concrete 22 on site between the beam end in the material axis direction and the pile head foundation 4 (joint space S2: described later), thereby forming an integrated foundation beam.

[0021] The completed cross section of the foundation beams 100, 200 is both beam depth H = 2000mm, beam width W = 1000mm, and the main beam reinforcements 14, 24 protrude from the axial end faces of the precast beam members 10, 20, 25, each with a member length L = 5250mm, and are joined via mechanical joints to the reinforcing bars extending from the pile head foundations 3, 4. In addition, stirrup reinforcements 18, 28 are arranged at specified intervals in the axial direction in the protruding range and joint positions of the main beam reinforcements 14, 24 (each diagram in Figure 1).

[0022] [Configuration of precast beam member 10] The configuration of the precast beam member 10, which is the main component of the foundation beam 100, will be described with reference to Figs. 1(b-1), 2, and 3. As described above, the precast beam member 10 is a half precast concrete product of a predetermined member length in which the beam main reinforcement 14 protrudes a predetermined length from both ends in the material axis direction (Fig. 1(b-1)). When constructing the foundation beam structure 1, the precast beam member 10 is placed on the leveled concrete (not shown) with a predetermined width between the stirrup reinforcements 16 arranged in a part of the member facing each other, as shown in Figs. 2 and 3(a). At this time, the width of the joint space S1 is set to 500 mm and the width of each precast beam member 10 is set to 250 mm out of the beam width of 1000 mm in the completed cross section of the foundation beam 100. As shown in the completed cross section of the foundation beam 100 (Fig. 2), the stirrup reinforcement 16 has a vertically elongated rectangular shape, as shown in Fig. 3(a), with its upper edge protruding from the upper surface of the precast beam member 10 and arranged so as to project a predetermined length into the joint space S1, and holds a predetermined number of main beam reinforcements 24 arranged in two stages at the upper and lower edges together with assembly reinforcements not shown.

[0023] At the bottom of the precast beam member 10, as shown in Fig. 1(b-1) and Fig. 3(b), through slits 19 with their lower sides open are formed continuously at a predetermined interval. The through slits 19 are formed at the same time as the beam member is manufactured at the factory by providing a box-cut section in the formwork when the precast beam member 10 is manufactured at the factory, and are used to pass the slab reinforcement 31 of the pressure plate 30 joined to the bottom side of the foundation beam 100 through the bottom side of the foundation beam 100 (Fig. 2). As shown in the left cross-sectional view of Fig. 3(a), the top surface of the through slits 19 is slightly inclined from the outer surface side of the beam to the inner surface side, and the through slits 19 are reliably closed as the concrete flows when the pressure plate concrete 32 is poured (Figs. 6(b)-(c)).

[0024] [Configuration of precast beam members 20 and 25] The configurations of the precast beam member 20 as the first precast concrete beam member and the precast beam member 25 as the second precast concrete beam member, which are the main components of the foundation beam 200, will be described with reference to Figs. 1(a-1), (c-1), 4, and 5. As shown in Figs. 1(a-1) and 4, the foundation beam 200 is a foundation beam placed on the periphery of a building, and one side of the pressure plate 30 and the structural slab 40 is joined to only one side of the foundation beam 200. Therefore, the foundation beam 200 is constructed using precast beam members 20 and 25 having different beam cross-sectional shapes.

[0025] The precast beam members 20, 25 have the same member length as the precast beam member 10, and are similar to the precast beam member 10 in that the main beam reinforcement 24 protrudes a predetermined length from both end faces in the material axial direction (Figure 1(c-1)), that when constructing the foundation beam structure 1, a joint space S1 is secured in which the stirrup reinforcement 26, 27 face each other with a predetermined width between them (Figures 4 and 5(a)), that the width of the joint space S1 is set to 500 mm and the width of each precast beam member 20, 25 is set to 250 mm out of the 1000 mm beam width of the completed cross section of the foundation beam 200, and that when the foundation beam 200 is completed, the main beam reinforcement 24 is arranged in two stages at the upper and lower ends of the beam using the stirrup reinforcement 26, 27 and assembly reinforcement not shown (Figure 4).

[0026] Here, the cross-sectional shape of each precast beam member 20, 25 will be described with reference to Figs. 5(a) to (c). In the precast beam member 20, the stirrup reinforcement 26 is a vertically long rectangle as shown in Fig. 5(a), and the upper side protrudes from the upper surface of the precast beam member 20, and is arranged so as to protrude by a predetermined width into the joint space S1. A plurality of beam main reinforcements 24 are arranged at the upper and lower sides together with assembly reinforcements (not shown). The length of the upper side of the stirrup reinforcement 26 is set to be longer than the center position (B / 2) in the beam width direction from the outer surface of the precast beam member 20 with respect to the beam width B of the completed cross section (Fig. 4) of the foundation beam 200. This ensures a sufficient fixing length for fixing the slab reinforcement 31 of the pressure plate 30 and the slab reinforcement 41 of the structural slab 40 in the foundation beam 200. Furthermore, as shown in Figures 8 (b) and (c), the ends of each slab reinforcement 31 are folded up to form folded-up fixing portions 31a, and are fixed near the vertical reinforcement 26a of the stirrup reinforcement 26.

[0027] 5(b), similarly to the precast beam member 10, the lower side of the precast beam member 20 is also provided with a series of through slits 29 with a predetermined interval between them, each of which is open at the bottom. The through slits 29 are formed at the same time as the precast beam member 20 is manufactured at a factory by providing a box cutout portion in the formwork to manufacture the member, and are used to pass the slab reinforcement 31 of the pressure plate 30 joined to the lower side of the foundation beam 200 through the lower side of the foundation beam 200. The upper surface of the through slits 29 is also slightly inclined from the outer surface side to the inner surface side of the beam, so that the through slits 29 are reliably closed as the concrete flows when the pressure plate concrete 32 is poured (FIGS. 8(c) and (d)).

[0028] On the other hand, as shown in Figures 5(a) and (c), the beam depth of the precast beam member 25 is the sum of the height of the precast beam member 20 and the thickness of the structural slab 40, and the whole of it also plays the role of a side formwork when the foundation beam concrete 21 is poured. From the side opposite the precast beam member 20, stirrup bars 27 protrude so as to face the largely protruding stirrup bars 26 with a specified gap between them. The stirrup bars 27 and the assembly bars (not shown) together hold a specified number of beam main bars 24 arranged in two stages at the upper and lower sides.

[0029] [Width direction joint of precast beam members (construction of joint space S1)] As shown in Fig. 3(a), the foundation beam 100 is constructed by placing precast beam members 10, 10 with a cross-sectional shape symmetrical with respect to the center line C in the width direction of the beam on a leveled concrete (not shown) on a base plate at a predetermined distance so that the stirrup bars 16 protruding from the ends of the members to the upper and side surfaces face each other, and a joint space S1 is formed between the precast beam members 10, 10. The foundation beam concrete 11 is poured on-site in this joint space S1, and the precast beam members 10, 10 and the foundation beam concrete 11 are integrally joined. At the same time that the foundation beam concrete 11 is poured, the end of the pressure plate concrete 32 is integrally constructed on the lower part of the precast beam member 10, and the end of the structural slab concrete 42 is integrally constructed on the upper surface of the precast beam member 10 (see Fig. 2). The structure and construction procedure will be described later with reference to Figs. 6 and 7.

[0030] The foundation beam 200 is constructed by placing precast beam members 20, 25 of different cross-sectional shapes, as shown in Fig. 4 and Fig. 5(a), on a level concrete (not shown) at a predetermined distance so that the stirrup bars 26, 27 protruding from the ends of the members to the upper surface side (only the precast beam member 20) and the side surface face each other, and pouring the foundation beam concrete 21 into the joining space S1 formed between the precast beam members 20, 25 at the site to integrally join the precast beam members 20, 25 and the foundation beam concrete 21. At the same time that the foundation beam concrete 21 is poured, the end of the pressure plate concrete 32 is integrally constructed on the lower surface of the precast beam member 20, and the end of the structural slab concrete 42 is integrally constructed on the upper surface of the precast beam member 20 (see Fig. 4). The structure and construction procedure will be described later with reference to Figs. 8 and 9.

[0031] [Jointing of precast beam members in the beam axis direction (construction of joint space S2)] At the end of the end of the precast beam member 10, 10 in the material axis direction of the foundation beam 100, a joint space S2 for joining the material end of the precast beam member 10, 10 and the pile head foundation 3, 4 is provided (FIG. 1). In this joint space S2, the beam main reinforcement 14 protruding from both end faces in the axial direction of the precast beam member 10 and the beam main reinforcement joint bar arranged to protrude from the side of the pile head foundation 3, 4 are joined via a mechanical joint (not shown), and the foundation beam 100 and the pile head foundation 3 are integrally joined by the foundation beam concrete 12 poured in the joint space S2. Also, in the joint space S2, the end of the pressure plate concrete 32 is integrally constructed by predetermined reinforcement arrangement at the bottom of the precast beam member 10, and the end of the structural slab concrete 42 is integrally constructed by predetermined reinforcement arrangement at the top.

[0032] A joint space S2 for joining the end of the precast beam members 20, 25 in the material axis direction of the foundation beam 200 to the pile head foundation 4 is also provided at the end of the precast beam members 20, 25 in the material axis direction. In this joint space S2, the beam main reinforcement 24 protruding from both end faces in the material axis direction of the precast beam members 20, 25 and the beam main reinforcement joint reinforcement arranged to protrude from the side of the pile head foundation 4 are joined via a mechanical joint (not shown), and the foundation beam 200 and the pile head foundation 4 are integrally joined by the foundation beam concrete 22 poured in the joint space S2. Also, in the joint space S2, a predetermined reinforcement is arranged by passing through the through slit 29 at the bottom of the precast beam member 20, and the end of the pressure plate concrete 32 is integrated with the foundation beam 200, and the end of the structural slab concrete 42 is integrated with the upper surface of the precast beam member 25.

[0033] [Integrated construction of foundation beam 100, pressure plate 30 and structural slab 40] The construction procedure for constructing the foundation beam 100 will be described below with reference to each figure in FIG. 1 and FIG. 6(a) to FIG. 7(f). As shown in FIG. 1(a), the foundation beam 100 is constructed between the pile head foundations 3, 3 located inside the building. On the leveling concrete (not shown) formed at the construction position of the foundation beam 100, the precast beam members 10, 10 are placed in pairs so as to secure a predetermined joint space S1 between them and a joint space S2 between the pile head foundation 3 at the end of the member (FIG. 6(a)). The slab reinforcement 31 of the pressure plate 30 (FIG. 6(c)) is arranged so that the four sides are surrounded between the adjacent foundation beams 100. At this time, the reinforcement is arranged by inserting each slab reinforcement 31 through the through slit 19 formed on the lower side of the precast beam member 10 (FIG. 6(b)). Furthermore, as shown in FIG. 6(c), the pressure plate concrete 32 (250 mm thick, for example) is poured. At this time, a part of the pressure plate concrete 32 is integrally filled up to the lower part of the joint space S1 of the foundation beam 100 through each through slit 19. This integrally joins the end edge of the pressure plate 30 and the lower edge of the foundation beam 100, and the pressure plate 30 is fixed and supported by the foundation beam 100.

[0034] After the pressure plate concrete 32 reaches a predetermined strength, a structural slab 40 (FIG. 7(e)) is constructed at the upper end of the foundation beam 100, which will be the upper surface of the underground pit 50. A shoring support 44 supporting the bottom formwork 43 of the structural slab concrete 42 is assembled on the pressure plate 30, and the slab reinforcement 41 of the structural slab 40 is arranged (FIG. 7(d)). At this time, the end of the slab reinforcement 41 is arranged up to the upper surface position of the foundation beam 100 with a sufficient anchorage length. Then, after pouring the foundation beam concrete 11 into the joint space S1 of the foundation beam 100, the structural slab concrete 42 is poured so as to integrally join the upper end of the foundation beam 100 and the structural slab 40 (FIG. 7(e)). In addition, in the construction of the structural slab concrete 42, the shoring support 44 can be omitted by using a steel deck plate (flat deck) for floor formwork instead of the bottom formwork 43.

[0035] When the concrete strength of the foundation beam concrete 11 and the structural slab concrete 42 are the same, the foundation beam concrete 11 and the structural slab concrete 42 can be cast continuously (FIGS. 7(e), (f)). When the concrete strengths are different, the foundation beam concrete 11 in the joint space S1 of the foundation beam 100 is cast up to the top of the precast beam member 10, and then a predetermined joint processing is performed as necessary, and the structural slab concrete 42 is cast. Regarding the construction of the joint space S2 between the precast beam member 10 and the pile head foundation 3, it is preferable to perform the reinforcing work of the stirrup reinforcement 18 before casting the foundation beam concrete 11 in the joint space S1 of the foundation beam 100, and to cast the concrete in the joint spaces S1 and S2 at the same time. After casting the joint spaces S1 and S2 and the structural slab concrete 42, the side formwork (not shown) of the joint space S2 and the bottom formwork 43 of the structural slab 40 are demolded after a predetermined curing period has elapsed. This completes the foundation beam structure 1 including the underground pit 50 in which the foundation beam 100, pressure plate 30, and structural slab 40 are integrated together (FIG. 7(f)).

[0036] [Integrated construction of foundation beam 200, pressure plate 30 and structural slab 40] The construction procedure for constructing the foundation beam 200 will be described below with reference to each figure of FIG. 1 and FIG. 8(a) to FIG. 9(g). As shown in FIG. 1(a), the foundation beam 200 is constructed between the pile head foundations 4, 4 located inside the building. A precast beam member 20 that defines one side of the foundation beam 200 is installed on the leveling concrete (not shown) formed at the construction position of the foundation beam 200 (FIG. 8(a)). Slab reinforcement 31 of pressure-resistant concrete 32 is arranged through a through slit 29 formed at the lower side of the installed precast beam member 20. At this time, a folded-up fixing portion 31a of a predetermined length is provided at the end of the slab reinforcement 31, and the folded-up fixing portion 31a of the slab reinforcement 31 is fixed to the vertical reinforcement 26a of the stirrup reinforcement 26 that is manufactured in advance to have a width of 1 / 2 or more of the beam width B so as to hold it. This ensures a predetermined fixing length for the slab reinforcement 31 (FIG. 8(b), (c)). Furthermore, the other precast beam member 25 is installed in a position that ensures a predetermined joint space S1 between the precast beam member 20 and a joint space S2 between the pile head foundation 4 at the end of the member, and the slab reinforcement 31 of the pressure plate 30 is arranged so that the four sides are surrounded between the adjacent foundation beams 100, 200 (Fig. 8(c)). Furthermore, as shown in Fig. 8(d), the pressure plate concrete 32 (250 mm thick as an example) is poured. At this time, a part of the pressure plate concrete 32 is integrally filled through each through slit 29 up to the lower part of the joint space S1 of the foundation beam 200. As a result, one side of the pressure plate 30 and the lower part of the foundation beam 200 are integrally joined, and the pressure plate 30 can be fixed and supported by the foundation beam 200 (Fig. 9(f)).

[0037] After the pressure plate concrete 32 reaches a predetermined strength, the structural slab 40, which will be the upper surface of the underground pit 50, is constructed at the upper end position of the foundation beam 200 (FIG. 9(f)). The shoring support 44 supporting the bottom formwork 43 of the structural slab concrete 42 is erected on the pressure plate 30, and the slab reinforcement 41 of the structural slab 40 is arranged (FIG. 9(e)). At this time, the end of the slab reinforcement 41 is bent downward and arranged so as to be located near the vertical reinforcement 26a of the stirrup reinforcement 26. Then, after the foundation beam concrete 22 is poured in the joint space S1, the structural slab concrete 42 is poured so as to integrally join the upper end of the foundation beam concrete 22 and the structural slab concrete 42 (FIG. 9(f)). In this embodiment, a case is shown in which the design strength of the concrete strength of the foundation beam concrete 11 and the concrete strength of the structural slab concrete 42 are different. In this case, the foundation beam concrete 22 in the joint space S1 of the foundation beam 200 is poured up to the top of the precast beam member 20, and then a predetermined joint processing is performed as necessary, and the structural slab concrete 42 is poured up to the top height of the precast beam member 25. The construction procedure of the joint space S2 between the precast beam member 20 and the pile head foundation 4 is preferably the same as that of the foundation beam 100 (FIGS. 1(a), (c-1)). After pouring the joint spaces S1, S2 and the structural slab concrete 42, the side formwork (not shown) of the joint space S2 and the bottom formwork 43 of the structural slab 40 are removed after a predetermined curing period has elapsed. This completes the foundation beam structure 1 with the underground pit 50 in which the foundation beam 200, the pressure plate 30, and the structural slab 40 are integrated (FIG. 9(g)).

[0038] According to the foundation beam structure 1 of this embodiment, the weight of each of the precast beam members 10, 20, 25 constituting the foundation beams 100, 200 can be kept below the weight of each of the precast column members 7 constituting the columns. Therefore, even though a precast foundation beam is used in the foundation beam structure, the foundation beam structure can be constructed with a lifting machine of the same capacity as in the case where only the superstructure is constructed by the conventional precast construction method. Furthermore, reinforcement is not required in the connection between the pair of precast beam members 10 and 20, 25 (connection space S1), and since the precast beam members 10, 20, 25 have a larger mass than the foundation beam concrete 11, 21 cast on site in the connection space S1, the member supporting the precast beam member 10 can be omitted, and separators and the like are also not required. Therefore, the construction labor and construction cost can be reduced, and the foundation beam structure 1 can be easily constructed.

[0039] In addition, it is also preferable to enhance adhesion between the foundation beam concrete 11, 22 poured on site and the inner surfaces of the precast beam members 10, 20, 25 by providing unevenness in the concrete surface on the opposing inner sides between opposing precast beam members 10, 10 or precast beam members 20, 25, grooves of various cross-sectional shapes along the material axis direction, or an arrangement of multiple cotters.

[0040] The present invention is not limited to the above-described embodiment, and various modifications are possible within the scope of the claims. In other words, embodiments obtained by combining technical means appropriately modified within the scope of the claims are also included in the technical scope of the present invention. [Explanation of symbols]

[0041] 1 Foundation beam structure 3,4 Pile head foundation 7 Precast concrete column members (precast column members) 10,20,25 Half precast concrete beams (precast beams) 11, 12, 21, 22 Foundation beam concrete (cast-in-place concrete) 14,24 Beam main reinforcement 16,26,27 Stirrup muscles 19,29 Through slit 30 Pressure Plate 31,41 Slab reinforcement 32 Pressure Plate Concrete 40 Structural slab 42 Structural slab concrete 100,200 Foundation beam S1,S2 joint space

Claims

1. A foundation beam structure in which a foundation beam is arranged to connect the pile head foundations, the periphery of a pressure plate is fixed and supported to the lower part of both sides of the foundation beam, and the periphery of a structural slab is fixed and supported to the upper end of both sides of the foundation beam, The foundation beam has first stirrup reinforcement, parts of which protrude from the side surface and the top surface of the beam member, and a plurality of through slits are formed at the lower end of the beam member through which parts of the slab reinforcement of the pressure plate pass. A pair of precast concrete beam members, which are symmetrical with respect to the center line of the foundation beam in the beam width direction, are placed opposite each other on the base plate, with a first joint space in the beam width direction and a second joint space between the end surface of the beam member and the pile head foundation, The slab reinforcement of the pressure plate passes through the through slit, and the slab reinforcement of the structural slab is arranged beyond the upper end of the precast concrete beam member and into the first joint space, A precast concrete foundation beam structure, characterized in that concrete is poured into the first joint space, the second joint space, the pressure plate, and the structural slab at site.

2. 2. The precast concrete foundation beam structure according to claim 1, wherein the slab reinforcement of the structural slab is arranged in the vicinity of the first stirrup reinforcement protruding from the upper surface of the foundation beam.

3. A foundation beam structure in which a foundation beam is arranged to connect the pile head foundations, a periphery of a pressure plate is fixed and supported to a lower part of one side of the foundation beam, and a periphery of a structural slab is fixed and supported to an upper end of the side of the foundation beam where the pressure plate is fixed and supported, The foundation beam comprises a first precast concrete beam member having first stirrup bars partially protruding from the side surface and the top surface of the beam member, and a plurality of through slits formed at the lower end through which some of the slab bars of the pressure plate pass, and a second precast concrete beam member having second stirrup bars partially protruding from the side surface of the beam member, the first precast concrete beam member being placed opposite to each other on the base plate so as to secure a first joint space in the beam width direction and a second joint space between the material end surface of the beam member and the pile head foundation, The slab reinforcement of the pressure plate passes through the through slit, and the slab reinforcement of the structural slab is arranged beyond the upper end of the first precast concrete beam member and into the first joint space, A precast concrete foundation beam structure, characterized in that concrete is poured into the first joint space, the second joint space, the pressure plate, and the structural slab at site.

4. 4. The precast concrete foundation beam structure according to claim 3, wherein the distance between the vertical reinforcement of the first stirrup reinforcement in the first joint space and the outer surface of the first precast concrete beam member on the side where the structural slab is attached is greater than 1 / 2 of the beam width of the foundation beam.

5. 5. The precast concrete foundation beam structure according to claim 4, wherein the end of the slab reinforcement of the pressure plate is bent near the vertical reinforcement of the first stirrup reinforcement in the first joint space and fixed in the concrete poured on site.

6. 4. The precast concrete foundation beam structure according to claim 3, wherein the beam depth of the second precast concrete beam member is equal to the sum of the beam depth of the first precast concrete beam member and the thickness of the structural slab.

Images