JP7699522B2 - Joint structure between piles and superstructure - Google Patents

Description

The present invention relates to a joint structure between a pile and a superstructure.

The most common method for connecting piles to the superstructure is to use a foundation footing made of reinforced concrete, but this method requires complicated reinforcing bar arrangement and increases the amount of soil excavated from the ground, which hinders cost reduction and shortening of construction time.

In order to eliminate the need for foundation footings and reduce the amount of soil excavated, for example, Patent Document 1 discloses a joint structure between a pile and a superstructure in which a cap steel pipe (joint jig) consisting of a base plate joined to the base of a steel pipe column or a concrete-filled steel pipe column and a steel pipe joined to its underside is placed over the top of a steel pipe pile or a precast concrete pile, and the gap is filled with concrete to integrate the pile and the column and form a rigid joint.

JP 2007-009438 A

However, the joint structure disclosed in Patent Document 1 is designed to be applied to single-story structures such as single-story buildings, and it is difficult to apply it to structures with two or more stories that have relatively heavy loads. This is because upper structures with two or more stories have large loads and are subject to large horizontal forces during earthquakes, which increases pile head displacement and column deformation angles, and the horizontal bearing capacity does not increase. In particular, if the N value of the ground at the planned construction site is low, pile head displacement and column deformation angles during an earthquake will be large, making it necessary to take measures to suppress horizontal deformation, such as increasing the pile diameter or installing braces.

The joint structure disclosed in Patent Document 1 assumes that the first floor will be a dirt floor, and reduces the amount of soil excavated by omitting the foundation beams that connect the joints between the piles and columns. However, when the ground is soft and the load on the first floor is large, it is difficult to apply this joint structure because the dirt floor structure will cause the floor to sink. In addition, the horizontal forces acting on the piles from each column base of the superstructure are not transmitted to each other through the foundation beams, and the magnitude of the horizontal forces acting on the piles from each column base is prone to variation. For this reason, depending on the floor plan of the superstructure, it becomes necessary to enlarge the pile diameter of the column base where large horizontal forces act, making it difficult to economically design the piles.

Furthermore, if a brace is installed on the superstructure to suppress pile head displacement and column deformation angle during an earthquake, an even greater horizontal force is applied to the pile below the column base where the lower end of the brace is joined, due to the input from the brace. Thus, if a brace is used in conjunction with a structure having the joint structure disclosed in Patent Document 1, it becomes necessary to further increase the pile diameter, which poses a problem of compromising the cost reduction effect.

The present invention has been made to solve the above problems, and aims to provide a joint structure between a pile and a superstructure that simplifies the structure and reduces costs, reduces the variation in the magnitude of the horizontal force acting on the pile from each column base of the superstructure, and can be applied to superstructures with two or more floors and can be used in conjunction with braces.

The means for solving the above problems are as follows.
[1] A joint structure between a pile and a superstructure, comprising: a pile driven into the ground; a vertical position adjustment jig installed on the top of the pile; a top plate to which a column of a superstructure is joined; a cap member having a cylindrical fitting provided below the top plate, the top plate being installed on the vertical position adjustment jig so that the fitting covers the upper outer periphery of the pile; and concrete filled in the space formed between the upper outer periphery of the pile and the cap member, wherein a joint portion with a foundation beam is provided directly above the top plate.
[2] The joint structure between a pile and a superstructure described in [1], wherein a brace is provided on the superstructure, and the lower end of the brace is joined within the joint portion.
[3] A joint structure between a pile and a superstructure as described in [2], wherein the height of the center of the joint position of the brace to the joint portion is within the beam depth of the foundation beam.
[4] The joint structure between a pile and a superstructure described in any one of [1] to [3], wherein the foundation beam is a steel beam and the joint portion has a bracket to which the foundation beam can be attached.
[5] The joint structure between a pile and a superstructure described in [4], in which the cap member and the joint portion are formed as a single steel member.
[6] The joint structure between a pile and a superstructure described in any one of [1] to [3], wherein the foundation beam is a reinforced concrete beam and the joint portion is a concrete beam wrapped around the base of the column.
[7] A joint structure between a pile and a superstructure described in [2] or [3], in which the foundation beam is a reinforced concrete beam, the joint portion is made of concrete wrapped around the base of the column, and the concrete wrapped around the base has reinforcing bars arranged in it to transmit the horizontal force input from the brace to the joint portion to the foundation beam below the brace.
[8] A joint structure between a pile and a superstructure as described in [6] or [7], wherein the foundation beam has a cross-sectional shape in which the width is greater than the height.
[9] A joint structure between a pile and a superstructure described in any one of [6] to [8], wherein the foundation beam is formed integrally with the concrete floor.

According to the joint structure between the pile and the superstructure of the present invention, the columns of the superstructure are joined to the top plate of the cap member that is fitted to the top of the pile, so that the columns of the superstructure can be joined to the pile without the need for a foundation footing. Therefore, by omitting the foundation footing, it is possible to reduce the amount of excavated soil, lighten the foundation, and shorten the construction period.

In addition, by joining the foundation beams to the joints provided on the top plate, the horizontal forces acting on the piles from each column base of the superstructure can be dispersed through the foundation beams. This reduces the variation in the magnitude of the horizontal forces acting on the piles from each column base of the superstructure.

As a result, it is possible to simplify the structure and reduce costs, while also enabling application to superstructures with two or more floors and the use of braces in combination.

1(a) to 1(c) are vertical and horizontal sectional views showing an example of a joint structure between a pile and a superstructure according to the present invention. 2(a) to 2(c) are perspective and plan views showing another example of the application of the joint structure between a pile and a superstructure of the present invention. 3(a) and 3(b) are a vertical sectional view and a horizontal sectional view showing another example of the joint structure between a pile and a superstructure according to the present invention. FIG. 4 is a vertical sectional view showing still another example of the joint structure between a pile and a superstructure according to the present invention.

Hereinafter, an embodiment of the joint structure between a pile and a superstructure of the present invention will be specifically described with reference to the drawings.
[First embodiment]
1(a) to 1(c) show vertical and horizontal cross-sectional views of a joint structure between a pile and a superstructure according to a first embodiment of the present invention. Fig. 1(b) shows a cross section taken along the line IB-IB in Fig. 1(a), and Fig. 1(c) shows a cross section taken along the line IC-IC in Fig. 1(a).

The joint structure between a pile and a superstructure in this embodiment is used at the location where a steel pipe pile 1 is joined to a steel pipe column 2 of the superstructure. In this embodiment, the superstructure is assumed to be a two- to three-story steel-framed building. As shown in FIG. 1(a), no footing is provided at the base of the steel pipe column 2, and the base of the steel pipe column 2 is directly joined to the steel pipe pile 1 as described below.

In this embodiment, the bases of each steel pipe column 2 are connected by a foundation beam 3 made of H-shaped steel, and a floor slab 32 made of a deck plate or the like is provided on the foundation beam 3.

To explain the joint structure between the pile and the superstructure in this embodiment in more detail, as shown in FIG. 1(a), the steel pipe pile 1 is erected in the excavated part of the ground G in a state in which the upper part of the steel pipe pile 1 protrudes from the excavated surface of the ground G. In addition, crushed stone 81 is laid around the steel pipe pile 1 in the excavated part of the ground G.

The top of the steel pipe pile 1 is closed with a cover plate, and as shown in FIG. 1(a), a shear stop ring 1a is welded to the outer periphery of the steel pipe pile 1 near the top and below it. Note that if the pull-out force expected to act on the steel pipe pile 1 from the steel pipe column 2 is small, the shear stop ring 1a may be omitted.

A vertical position adjustment jig 6 is installed on the cover plate at the top of the steel pipe pile 1. Furthermore, a cap member 7 is installed on the vertical position adjustment jig 6.

The cap member 7 is a joining jig that joins the steel pipe pile 1 and the steel pipe column 2, and has a top plate 71 to which the base of the steel pipe column 2 is joined, and a cylindrical fitting portion 72 provided below the top plate 71. The top plate 71 is installed on the vertical position adjustment jig 6 so that the fitting portion 72 covers the upper outer periphery of the steel pipe pile 1. The vertical position adjustment jig 6 fine-tunes the height of the steel pipe column 2 relative to the steel pipe pile 1.

The inner diameter of the fitting portion 72 of the cap member 7 is larger than the outer diameter of the steel pipe pile 1 (for example, about 1.2 to 2.5 times the outer diameter of the steel pipe pile 1). A top plate 71 with a diameter larger than the outer diameter of the fitting portion 72 is welded to the upper end of the fitting portion 72. A slip stop ring 72a is welded to the lower end of the inner peripheral surface of the fitting portion 72. Note that if the pull-out force expected to act from the steel pipe column 2 to the steel pipe pile 1 is small, the slip stop ring 72a of the fitting portion 72 of the cap member 7 may be omitted, just as the slip stop ring 1a of the steel pipe pile 1 may be omitted.

Then, with the vertical position adjustment jig 6 adjusting the height of the steel pipe column 2 relative to the steel pipe pile 1, i.e., the height of the cap member 7 relative to the steel pipe pile 1, basal concrete 82 is poured on top of the crushed stone 81 laid around the steel pipe pile 1. As a result, the opening at the lower end of the fitting portion 72 of the cap member 7 is blocked by the basal concrete 82.

Furthermore, as shown in FIG. 1(c), concrete 8 is filled into the space formed between the upper outer peripheral surface of the steel pipe pile 1 and the cap member 7 through the through hole 71h provided in the top plate 71 of the cap member 7. Then, as the concrete 8 hardens, the steel pipe pile 1 and the steel pipe column 2 are joined.

Furthermore, in the joint structure between the pile and the superstructure in this embodiment, a joint portion 73 with the foundation beam 3 is provided directly above the top plate 71 of the cap member 7. The joint portion 73 is provided with a bracket 73J for attaching the foundation beam 3.

Specifically, as shown in Figs. 1(a) to 1(c), a diaphragm 73a is disposed above a top plate 71 and parallel to the top plate 71. The distance between the top plate 71 and the diaphragm 73a is set equal to the distance between the upper and lower flanges of the H-shaped steel that constitutes the foundation beam 3. The sides of the top plate 71 and the diaphragm 73a are joined by welding to the upper and lower flanges 73f of the bracket 73J that attaches the foundation beam 3. A web 73w is joined by welding between the top plate 71 of the cap member 7 and the flanges 73f joined to its sides, and the diaphragm 73a and the flanges 73f joined to its sides.

The upper and lower flanges 73f joined to the top plate 71 and diaphragm 73a of the cap member 7 and the tip portion of the web 73w joined between the upper and lower flanges 73f become the bracket 73J for attaching the foundation beam 3. The tip of the bracket 73J should be located, for example, about 1200 mm from the central axis of the steel pipe column 2.

In this embodiment, the cap member 7 and the joint portion 73 are fabricated as a single steel frame member in a steel frame factory and then transported to the site for use.

In the joint structure between the pile and the superstructure of this embodiment, the foundation beam 3 is made of H-shaped steel, so the beam depth of the foundation beam can be suppressed to, for example, about 700 to 900 mm. In contrast, if a conventional foundation construction method is adopted for a building of the same scale, the beam depth of the foundation beam made of reinforced concrete will be about 1500 to 1800 mm. In this way, since the foundation beam 3 is made of H-shaped steel, the size of the beam depth is suppressed, the amount of excavated soil is significantly reduced, and the weight of the foundation can be significantly reduced. As a result, the pile diameter of the steel pipe pile 1 can be reduced, for example, from about φ1200 to about φ1000. Furthermore, when the conventional foundation construction method is adopted, structural root wrapping is required to fix the column base of the steel pipe column 2, whereas this is not necessary in the joint structure between the pile and the superstructure of this embodiment.

Furthermore, in the joint structure between the piles and the superstructure in this embodiment, the foundation beams 3 on which the floor slab 32 is provided are supported by the steel pipe piles 1 together with the steel pipe columns 2, so that even if the ground is soft, the load capacity of the first floor floor can be increased, unlike a dirt floor structure.
[Second embodiment]
Fig. 2(a) is a schematic perspective view of a building to which the joint structure between a pile and a superstructure according to the second embodiment of the present invention is applied. Fig. 3(a) and Fig. 3(b) are a vertical cross-sectional view and a horizontal cross-sectional view of the joint structure between a pile and a superstructure according to the present embodiment. Fig. 3(b) shows a cross section taken along the line IIIB-IIIB in Fig. 3(a).

In the joint structure between the pile and the superstructure in this embodiment, unlike the first embodiment, the foundation beam 4 is a reinforced concrete beam rather than a steel beam. As shown in FIG. 3(a), the joint 25 with the foundation beam 4, which is provided directly above the top plate 71 of the cap member 7, is made of concrete wrapped around the base of the steel pipe column 2. In other words, in this embodiment, the top plate 71 of the cap member 7 is used as the lower surface base of the concrete wrapped around the base that constitutes the joint 25.

As shown in Figures 2(b) and 2(c), in this embodiment, the superstructure is assumed to be a logistics warehouse with a truck berth on one side (the upper side in Figures 2(b) and 2(c)) of a two-story steel-framed building and a first-floor floor made of concrete slab 41 (see Figure 2(a)).

Furthermore, in this embodiment, in order to suppress the displacement of the pile head and the deformation angle of the steel pipe column 2 during an earthquake, a brace 5 is installed in the building to ensure the horizontal bearing capacity of the building. Figure 2 (b) shows the arrangement of the brace 5 at the base of the first floor column of the above-mentioned building. As shown in Figure 2 (b), in this embodiment, one side of the first floor of the building is a truck berth, so the arrangement of the brace 5 is restricted. Therefore, the brace 5 is arranged in both the X and Y directions on the side where the truck berth is not provided (the lower side of Figures 2 (b) and 2 (c)), and the lower end of the brace 5 is joined to the steel pipe column 2 in the joint section 25. In addition, as shown in Figures 3 (a) and 3 (b), the root-wrapped concrete constituting the joint section 25 to which the lower end of the brace 5 is joined has a U-shaped reinforcing bar 26 arranged to transmit the horizontal force input from the brace 5 to the foundation beam 4 below the brace 5.

Figure 2(c) shows the arrangement of the foundation beams 4 in the above-mentioned building. As shown in Figure 2(c), the foundation beams 4 are installed at the center of the structural surface on which the braces 5 are installed, so that the shear force input from the braces 5 is transmitted through the foundation beams 4 to the concrete floor 41.

In this embodiment, the height of the first floor, which is made of the concrete floor 41, is about 1100 mm above the ground level. As shown in Figures 3(a) and 3(b), the foundation beam 4 has a flat cross-sectional shape with a width 4w greater than the height 4h, and is formed integrally with the concrete floor 41 at approximately the same height as the concrete floor 41. Furthermore, as shown in Figure 3(a), the height (brace point) 5P of the center of the joint position of the brace 5 to the steel pipe column 2 in the joint section 25 is set to fall within the beam depth 4h of the foundation beam 4.

In other respects, the joint structure between the piles and the superstructure in this embodiment is configured similarly to the joint structure between the piles and the superstructure in the first embodiment.

In the joint structure between the piles and the superstructure of this embodiment, the horizontal force acting on the base of the steel pipe column 2 from the lower end of the brace 5 during an earthquake is transmitted to the joint between the other steel pipe column 2 and the steel pipe pile 1 through the foundation beam 4 attached to the joint part 25 of the base of the steel pipe column 2 and the concrete floor 41. This reduces the variation in the magnitude of the horizontal force acting on the steel pipe pile 1 from the base of each steel pipe column 2 of the building.

In addition, in the joint structure between the pile and the superstructure in this embodiment, the joint position (brace point) 5P of the brace 5 to the steel pipe column 2 within the joint section 25 is set at approximately the same height as the foundation beam 4 and the concrete floor 41 (see FIG. 2(a)). This prevents additional bending due to the height difference when there is a height difference between the brace point 5P and the foundation beam 4 and the concrete floor 41, as shown in FIG. 4. Therefore, horizontal force can be smoothly transmitted from the brace 5 to the foundation beam 4 and the concrete floor 41.

In addition, the U-shaped reinforcing bars 26 arranged in the concrete 25 that forms the joint 25 can further facilitate the transmission of horizontal forces from the brace 5 to the foundation beams 4 and the concrete floor 41.

Therefore, even if there is variation in the horizontal forces acting on the bases of each steel pipe column 2 of a building, the horizontal forces transmitted to the steel pipe pile 1 can be balanced, and the pile diameter of the steel pipe pile 1 can be reduced, making it possible to economically design the steel pipe pile 1.

In addition, in the joint structure between the piles and the superstructure in this embodiment, the width 4w of the foundation beam 4 is made larger than its height 4h. This allows for a reduction in the amount of excavated soil, a lighter foundation, and lower costs compared to conventional foundation construction methods in which the height of the foundation beam is larger than its width.

In the above embodiments, an example was described in which a steel pipe pile 1 and a steel pipe column 2 are joined by the joint structure between a pile and a superstructure of the present invention, but the application of the present invention is not limited to this. For example, the present invention can also be applied to joint structures between various prefabricated piles and various columns, such as PHC piles, PRC piles (centrifugally formed prestressed reinforced high-strength concrete piles), and SC piles (centrifugally formed concrete piles with steel pipe shells).

1 Steel pipe pile (pile)
1a Shear stop ring 2 Steel pipe column (pillar)
25 Root wrapping concrete (joint section)
26 Reinforcement 3 Steel beam (foundation beam)
31 Splice plate 32 Floor slab 4 Reinforced concrete beam (foundation beam)
4h Beam height
Reference Signs List 41 Concrete floor 5 Brace 5P Joint position 6 Vertical position adjustment jig 7 Cap member 71 Top plate 71h Through hole 72 Fitting portion 72a Anti-slip ring 73 Connection portion 73J Bracket 73a Diaphragm 73w Web 73f Flange 8 Concrete 81 Crushed stone 82 Waste concrete G Ground

Claims (9)

Piles driven into the ground,
A vertical position adjustment jig installed on the top of the pile;
a cap member having a top plate to which a column of an upper structure is joined and a cylindrical fitting portion provided under the top plate, the top plate being installed on the vertical position adjustment jig so that the fitting portion covers the outer periphery of the upper part of the pile;
A joint structure between a pile and a superstructure, the joint structure comprising concrete filled in a space formed between an upper outer peripheral surface of the pile and the cap member,
A joint between the piles and the superstructure is provided directly above the top plate, with a joint to the foundation beam. The upper structure is provided with a brace,
2. The joint structure between a pile and a superstructure according to claim 1, wherein a lower end of the brace is joined within the joint portion. The joint structure between the pile and the superstructure according to claim 2, wherein the height of the center of the joint position of the brace to the joint portion is within the beam depth of the foundation beam. The foundation beam is a steel beam,
2. The joint structure between a pile and a superstructure according to claim 1 , wherein the joint portion has a bracket to which the foundation beam can be attached. The joint structure between a pile and a superstructure according to claim 4, wherein the cap member and the joint portion are formed as a single steel member. The foundation beam is a reinforced concrete beam,
The joint structure between a pile and a superstructure as described in any one of claims 1 to 3, wherein the joint portion is made of concrete wrapped around the base of the pillar. The foundation beam is a reinforced concrete beam,
4. The joint structure between a pile and a superstructure according to claim 2 or 3, wherein the joint portion is made of concrete wrapped around the base of the column, and the concrete wrapped around the base contains reinforcing bars arranged in the concrete to transmit the horizontal force input from the brace to the joint portion to the foundation beam below the brace. The joint structure between the pile and the superstructure according to claim 6 or 7, wherein the foundation beam has a cross-sectional shape in which the width is greater than the height. The joint structure between a pile and a superstructure according to any one of claims 6 to 8, wherein the foundation beam is formed integrally with the concrete floor.

Images