Precast concrete footing structure and construction method thereof

Abstract

To accommodate piles that are subject to tensile forces, and reduce the amount of work required for construction by dividing a footing structure into upper and lower precast members, and making transportation and lifting easier.SOLUTION: In this construction method, a head of a foundation pile is accommodated in a through hole of a lower footing member made of precast concrete, the lower footing member having a through hole capable of accommodating the head of the foundation pile, the lower footing member is then installed, and cast-in-place concrete is poured into a gap between the head of the foundation pile and the through hole of the foundation pile, thereby integrating the head of the foundation pile and the lower footing member, and fixing an upper footing member made of precast concrete, which has joints with columns and beams, and a joint that is joined to the lower footing member, onto the lower footing member.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a footing structure made of precast concrete and a construction method thereof.

Background Art

[0002] In the foundation structure of a building, for the purpose of mainly reducing the labor during construction, it has been proposed to precast the entire foundation footing including the column-beam joints where the reinforcement is complicated. For example, Patent Documents 1 and 2 disclose a structure in which a footing member (integral precast footing member) made of precast concrete with a recess formed on the lower surface for covering the pile head is placed on the pile head of a pile. Patent Document 3 describes the use of a half-precast member in which only the lower part of the foundation footing is precast. Patent Document 4 discloses a structure in which only the lower part in the height direction of the footing is a precast member through which the pile head penetrates.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0004] When the foundation footing, including the column-beam joint, is precast as a whole as in Patent Documents 1 and 2, a precast footing member having a recess for covering the pile head is placed on the pile head, and a filling material is filled in the recess and the gap between the pile. However, such a precast footing member does not have pile head reinforcing bars connecting the pile head and the foundation footing, and is not suitable for piles subjected to tensile force. Also, it is difficult to ensure a sufficient embedment length of the pile into the footing, and the pile head joint becomes semi-rigid. Furthermore, the precast footing itself becomes a relatively heavy object, requiring a large hoisting device, etc., which makes the construction troublesome.

[0005] On the other hand, in the half-precast member in which only the lower part of the foundation footing is precast as in Patent Documents 3 and 4, a through-hole through which the pile is inserted is provided in the precast member. Therefore, it is possible to ensure a sufficient embedment length of the pile with respect to the foundation footing, and it is also possible to make the pile head joint not only semi-rigid but also rigid. Also, if pile head reinforcing bars are arranged, it is possible to integrate the pile and the foundation footing with cast-in-place concrete and apply it to piles subjected to tensile force. However, when using a half-precast member, the main bars of the column, steel frame anchors, and the main bars of the beam intersect, and the amount of reinforcement is also large, so the joint part where the construction becomes complicated must be constructed on-site. Compared with the above-mentioned integral precast footing member, the effect of reducing on-site work and shortening the construction period by precasting is low.

[0006] In addition, Patent Document 3 states that "regardless of whether the upper part of the footing is made of cast-in-place reinforced concrete or precast concrete", but the specific structure of the precast concrete upper part of the footing and its technical significance are unclear.

[0007] In view of the above circumstances, an object of the present invention is to provide a precast concrete footing structure and a construction method thereof that can cope with piles subjected to tensile force, and that can reduce the construction effort by making the transportation and hoisting work easier by dividing the footing structure into an upper precast member and a lower precast member.

Means for Solving the Problem

[0008] To achieve the above object, the precast concrete footing structure of the present invention is a footing structure for joining a building foundation pile, the head of the foundation pile, a column, and a beam. The precast concrete lower footing member has a through hole capable of accommodating the head of the foundation pile, and an upper footing member made of precast concrete having a joint portion between the column and the beam and a joint portion joined to the lower footing member, and cast-in-place concrete placed in a gap between the head of the pile in the through hole of the lower footing member.

[0009] Further, the lower footing member and the upper footing member may be joined by prestress. Furthermore, the lower footing member and the upper footing member may be joined to each other by bolts and nuts. The lower footing member and the upper footing member may be joined to each other by reinforcing bars connected by a mechanical joint. The upper end surfaces of the lower footing member and the cast-in-place concrete and the lower end surface of the upper footing member may be joined to each other via a leveling adjustment material. The leveling adjustment material may be a cement-based material, a resin-based filler, or a pressure-sensitive curing rubber.

[0010] The construction method of the precast concrete footing structure of the present invention is a method in which the head of the foundation pile is accommodated in the through hole of the precast concrete lower footing member having a through hole capable of accommodating the head of the foundation pile, the lower footing member is installed, and cast-in-place concrete is placed in the gap between the head of the pile in the through hole of the foundation pile, thereby integrating the head of the foundation pile and the lower footing member, and fixing an upper footing member made of precast concrete having a joint portion between the column and the beam and a joint portion joined to the lower footing member on the lower footing member.

[0011] According to the present invention, by joining and integrating a precast concrete lower footing member and an upper footing member, which are each individually manufactured in a factory (including temporary manufacturing facilities near the construction site), at the construction site, compared with an integral precast footing member manufactured in the factory in advance, transportation and handling are facilitated, the overall constructability is improved, and the construction period can be shortened. In addition, a footing structure capable of coping with piles subjected to tensile forces can be obtained.

Brief Description of the Drawings

[0012]

Figure 1

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Figure 11

Embodiments for Carrying Out the Invention

[0013] Hereinafter, embodiments of the precast concrete footing structure and its construction method of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing the whole of the precast concrete footing structure of the present embodiment, FIG. 2 is a plan view of this precast concrete footing structure, and FIGS. 6 and 7 are longitudinal sectional views thereof. The portion drawn by the solid line in FIG. 1 is the precast concrete footing structure 100 of the present embodiment. The footing structure 100 has a lower footing member 10 and an upper footing member 20. The lower footing member 10 and the upper footing member 20 are precast concrete members individually manufactured in a factory.

[0014] As shown in FIGS. 4, 6, and 7, the lower footing member 10 has a through hole 12 through which the pile head 31 of the foundation pile 30 can be inserted in the vertical direction. The thickness of the lower footing member 10 (the depth of the through hole 12) is set such that the height of the top end 33 of the pile head 31 of the foundation pile 30 is slightly lower than the upper end surface 10a of the lower footing member 10 when the lower footing member 10 is installed. In the through hole 12, cast-in-place concrete 40 is placed at the same height as the upper end surface 10a of the lower footing member 10, whereby the pile head 31 of the foundation pile 30 and the lower footing member 10 are integrated. Note that 3 indicates the main reinforcement of the foundation pile 30. A plurality of PC steel bars 14 for joining with the upper footing member 20 are provided so as to project vertically from the upper end surface 10a of the lower footing member 10. These PC steel bars 14 are embedded during the manufacture of the lower footing member 10 in the factory.

[0015] The upper footing member 20 has a joint portion 22 where the lower end surface 20b is joined to the upper end surface 10a of the lower footing member 10, a column-beam connection port portion 24, and a beam joint portion 25. In FIG. 1, the dotted line 200 is another precast concrete column joined to the column-beam connection port portion 24 of the upper footing member 20, and the dotted line 300 is another precast concrete beam joined to the beam joint portion 25 of the upper footing member 20, etc. However, the column is not limited to being made of precast concrete. It may be a cast-in-place concrete column or a steel column. Similarly, the beam may be a cast-in-place concrete beam or a steel beam.

[0016] The widths of the joint portion 22 in the X direction and the Y direction may be the same as the widths of the lower footing member 10 in the X direction and the Y direction, respectively. As shown in FIG. 6, the joint portion 22 is provided with a plurality of PC steel bar holes 26 through which the PC steel bars 14 protruding from the upper end surface 10a of the lower footing member 10 penetrate vertically. Then, as shown in FIG. 7, with the upper footing member 20 placed on the lower footing member 10, the tip portions of each of the PC steel bars 14 protrude from the upper end openings of the PC steel bar holes 26 of the joint portion 22, and nuts 28 are set on the tip portions of the PC steel bars 14 protruding from the upper end openings of the PC steel bar holes 26 and tensioned with a hydraulic jack, whereby the upper footing member 20 is connected to and joined to the lower footing member 10.

[0017] As described above, the precast concrete footing structure 100 of the present embodiment joins the precast concrete lower footing member 10 and the upper footing member 20, which are individually manufactured in the factory, to each other on site. Therefore, compared with the integral precast footing member manufactured in the factory in advance, the transportation and handling are easy, the total constructability is improved, and the construction period can be shortened.

[0018] In addition, since reinforcing bars (not shown), PC steel bars (not shown), sheaths (not shown), bolts (not shown) that are connected to columns, beams, etc. can be arranged with high precision at the factory in the lower footing member 10 and the upper footing member 20, construction management at the site becomes easier. Further, once the installation of the lower footing member 10 and the upper footing member 20 is completed, without waiting for the completion of the construction of the entire foundation structure, the construction of connecting columns and beams to the constructed footing structure while constructing other footing structures can be carried out in parallel, enabling further shortening of the construction period.

[0019] Next, a construction method of the precast concrete footing structure of the present embodiment will be described. As shown in FIG. 3, after the installation of the foundation pile 30, the ground around the pile head 31 of the foundation pile 30 is excavated, and leveling concrete 9 is placed on the excavated ground 7. Then, the concrete in the excess portion of the pile head 31 of the foundation pile 30 is removed to expose the reinforcing bars 3 inside the foundation pile 30.

[0020] Next, as shown in FIG. 4, the lower footing member 10 is installed on the leveling concrete 9 in such a manner that the pile head 31 [Yiyu 1] protruding above the leveling concrete 9 is accommodated in the through hole 12.

[0021] Thereafter, as shown in FIG. 5, the in-situ concrete 40 is placed in the through hole 12 of the lower footing member 10 installed on the leveling concrete 9 to integrate the pile head 31 of the foundation pile 30 and the lower footing member 10. At this time, the in-situ concrete 40 is placed in the through hole 12 up to the height of the upper end surface 10a of the lower footing member 10.

[0022] Next, as shown in FIGS. 6 and 7, the upper footing member 20 is installed on the lower footing member 10. At this time, the two are joined so that the lower end surface 20b of the joint portion 22 of the upper footing member 20 faces the upper end surface 10a of the lower footing member 10. A plurality of PC steel bars 14 for joining with the upper footing member 20 are provided protruding vertically on the upper end surface 10a of the lower footing member 10, and a plurality of PC steel bar holes 26 into which the respective PC steel bars 14 are inserted are provided in the joint portion 22 of the upper footing member 20. Therefore, each PC steel bar 14 is inserted into each PC steel bar hole 26, a nut 28 is set on the tip portion of each PC steel bar 14 protruding from the upper end surface of the joint portion 22 of the upper footing member 20, and prestress is introduced into the PC steel bar 14 with a hydraulic jack, thereby crimping and joining the upper footing member 20 on the lower footing member 10.

[0023] Also, as shown in FIG. 7, the upper end surface 10a of the lower footing member 10 and the in-situ concrete 40 and the lower end surface 20b of the upper footing member 20 may be joined via a leveling adjustment material 50. As the leveling adjustment material 50, a cement-based material such as dry mortar or non-shrinking mortar can be adopted. In addition, it may have deformation performance that can follow the unevenness of the precast concrete surface during construction and obtain strength during use. For example, resin-based fillers, pressure-sensitive curing rubbers, etc. can be mentioned.

[0024] As described above, according to the construction method of the precast concrete footing structure of the present embodiment, the precast concrete lower footing member 10 and the upper footing member 20, which are individually manufactured in the factory, are joined and integrated with each other on site. Therefore, compared with the integral precast footing member manufactured in the factory in advance, the transportation and handling are easier, so the total constructability is improved and the construction period can be shortened.

[0025] Furthermore, since the embedding length of the pile into the through hole 12 of the lower footing member 10 can be adjusted and pile head reinforcement bars (not shown) can be arranged in the through hole 12, it is possible to cope with piles subjected to tensile force and to make the pile into a rigid joint structure.

[0026] (Other embodiments) As the footing structure 101 of another embodiment, as shown in FIG. 8, the height of the top end 33 of the pile head 31 of the foundation pile 30 is set to be the same as or slightly lower than the height of the upper end surface 10a of the lower footing member 10, and the cast-in-place concrete 40 is filled in the gap between the through hole 12 of the lower footing member 10 and the pile head 31 without protruding the main reinforcement 3 from the pile head 31 to integrate the pile head 31 and the lower footing member 10.

[0027] FIGS. 9 and 10 are longitudinal sectional views of a footing structure 102 showing still another embodiment. In this footing structure 102, while a reinforcing bar 141 is provided to protrude from the upper end surface 10a of the lower footing member 10, a bar-shaped steel material 143 such as a reinforcing bar with a mechanical joint 126 for joining with the reinforcing bar 141 fixed to one end is embedded in the upper footing member 20. When the upper footing member 20 is placed on the lower footing member 10, the reinforcing bar 141 protruding from the lower footing member 10 is inserted into the mechanical joint 126 embedded in the upper footing member 20 to be connected to the bar-shaped steel material 143 in the upper footing member 20, thereby joining the lower footing member 10 and the upper footing member 20 to each other. For the mechanical joint 126, for example, a mortar-filled sleeve joint or the like can be used.

[0028] Furthermore, as another embodiment, as shown in FIG. 11, the planar shape of the joint portion 22 between the lower footing member 10 and the upper footing member 20 is not a quadrangle, but for example, an octagon lacking the four corner portions of the joint portion 22 of the quadrangular lower footing member 10 and the upper footing member 20 shown in FIG. 2, so that the plane occupied by the footing structure 102 may be reduced. By this reduction, the lower footing member 10 and the upper footing member 20 can be lightened, or an optimal footing structure 103 that matches conditions such as the shape of the site can be obtained. Furthermore, it may be circular or a polygonal shape close to a circle.

Description of Reference Numerals

[0029] 3 Reinforcing bar 10 Lower footing member 12 Through hole 14 PC steel bar 20 Upper footing member 22 Joint part 24 Column-beam joint 25 Beam joint 30 Foundation pile 31 Pile head 40 Cast-in-place concrete 50 Unevenness adjusting material 100 Footing structure

Claims

1. A footing structure for joining a foundation pile of a building, the head of the foundation pile, a column, and a beam, a precast concrete lower footing member having a through-hole capable of accommodating the head of the foundation pile, an upper footing member made of precast concrete having a joint portion with the column and the beam and a joint portion joined to the lower footing member, cast-in-place concrete placed in a gap between the head of the pile in the through-hole of the lower footing member and the head of the pile, and comprising a footing structure made of precast concrete.

2. A footing structure made of precast concrete according to Claim 1, wherein the lower footing member and the upper footing member are press-bonded to each other by prestress A footing structure made of precast concrete.

3. A footing structure made of precast concrete according to Claim 1, wherein the lower footing member and the upper footing member are joined to each other by bolts and nuts A footing structure made of precast concrete.

4. A footing structure made of precast concrete according to Claim 1, wherein the lower footing member and the upper footing member are joined to each other by reinforcing bars connected by a mechanical joint A footing structure made of precast concrete.

5. A footing structure made of precast concrete according to any one of Claims 1 to 4, wherein the upper end surfaces of the lower footing member and the cast-in-place concrete and the lower end surface of the upper footing member are joined to each other via a level difference adjusting material A footing structure made of precast concrete.

6. A footing structure made of precast concrete according to Claim 5, wherein the level difference adjusting material is a cement-based material, a resin-based filler, or pressure-sensitive curing rubber A footing structure made of precast concrete.

7. Install the lower footing member with the head of the foundation pile accommodated in the through-hole of the precast concrete lower footing member having a through-hole capable of accommodating the head of the foundation pile, By placing cast-in-place concrete in the gap between the head of the pile in the through-hole of the foundation pile and the head of the pile, the head of the foundation pile and the lower footing member are integrated, Fix an upper footing member made of precast concrete, which has a joint with a column and a beam and a joint portion joined to the lower footing member, on the lower footing member. A construction method for a footing structure made of precast concrete.

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