JP2020133174A - Pile foundation structure - Google Patents

Abstract

[PROBLEMS] To provide a pile foundation structure in which a pile head of a pile body and a structural portion of a pile foundation are integrally joined in the foundation structure of various structures supported by pile bodies. SOLUTION: A pile 1 driven with a pile head 2 having a predetermined protruding length from a ground surface, and a foundation beam 15 joined to the pile head 2 form an annular shape in plan view, and the foundation An annular joint that holds anchoring bars 31 jointly joined to the main reinforcement end 17 of the beam 15 and is installed around the pile head 2 so that the pile head 2 is positioned approximately at the center of the annular inner peripheral space 26. a body 20; The foundation beam 15 is installed at a predetermined distance from the outer peripheral surface of the annular joint 20 , and the main reinforcement ends 17 of the foundation beam 15 and the anchoring reinforcement 31 are joined to each other with the annular joint 20 and joint concrete 35 . The inner peripheral space 26 of the annular joined body 20 is filled with filling concrete 36, and the pile head 2 and the foundation beam 15 are joined. [Selection drawing] Fig. 1

Description

The present invention relates to a pile foundation structure, and relates to a pile foundation structure capable of integrally joining a pile head of a pile body and a structural portion of the pile foundation in the foundation structure of various structures supported by the pile body.

In the joint structure between the pile head of the pile body and structural parts such as underground beams and foundation footings of the reinforced concrete structure, the pile head and the structural part of the pile foundation are integrated so that a predetermined strength and rigidity are secured. A large number of reinforcing bars are arranged in a space having a narrow joint structure, and labor-intensive and complicated reinforcement work is required.

In order to solve this problem, a joint structure between a beam and a pile has been proposed in which an annular member functioning as a fixing portion of a beam main bar end is loosely fitted on the outer periphery of a steel pipe pile (Patent Document 1). In this joint structure, the ends of the beam main bars are attached so that the ends of the reinforcing bars are lined up on the fixing plates attached at predetermined positions of the fixing rings in which the strips provided on the outer periphery of the steel pipe pile are arranged in an annular shape. Therefore, when a large-diameter reinforcing bar is used for the beam main bar, it is difficult to secure a predetermined fixing length and rigidity of the joint structure with an annular member composed of only a fixing plate and a fixing ring.

On the other hand, Patent Document 2 discloses a foundation structure in which the rigidity of the pile head and the foundation footings is increased. In this foundation structure, a predetermined space (pile head insertion portion) is secured at the outer peripheral position of the pile head, a precast foundation member is installed, and a predetermined stress transmission member is provided at the pile head insertion portion to fill the space. The pile head and the precast foundation member are integrated by filling with.

Japanese Unexamined Patent Publication No. 2001-342684 Japanese Unexamined Patent Publication No. 2016-70028

In the foundation structure disclosed in Patent Document 2, the joint portion of the pedestal portion installed above the precast foundation member is rigidly joined to the end portion of the steel frame beam, and then the footing portion is footed so as to cover the entire joint portion with concrete. The entire concrete is placed. Therefore, the basic structure disclosed in Patent Document 2 has a structural form different from the structure in which the main bar end portion of the underground beam is directly joined to the pile head side with a sufficient anchorage length. Therefore, in the joint structure of the reinforced concrete structure with the underground beam and the foundation footing, a pile foundation structure capable of easily and surely joining and holding the main bar at the beam end to the pile head side is required.

Therefore, an object of the present invention is to solve the problems of the above-mentioned conventional techniques, and to use a precast joint member capable of joining and holding the anchored ends of the reinforcing bars of the underground beam and the foundation footings to the pile head and the ground. It is an object of the present invention to provide a pile foundation structure that enables easy and reliable joining with structural parts such as a center beam and foundation footings.

In order to achieve the above object, the present invention presents a plan view of a pile in which a pile head is driven with a predetermined protruding length from the ground surface, a structural portion of a pile foundation joined to the pile head, and a plan view. The pile head forms an annular shape, holds the anchoring bar jointly joined to the main bar end of the structural portion of the pile foundation, and the pile head is located substantially at the center of the inner peripheral space of the annular shape. The pile foundation is provided with an annular joint to be installed around the portion, and the structural portion of the pile foundation is installed with a predetermined separation portion from the outer peripheral surface of the annular joint, and is installed with the main bar end of the structural portion of the pile foundation. In a state where the anchoring bar is joined, the annular joint and the joint concrete are integrated, the inner peripheral space of the annular joint is filled with filled concrete, and the structural portion of the pile head and the pile foundation. It is characterized in that and is joined.

The annular joint is preferably a precast concrete member in which the outer peripheral surface and the inner peripheral surface of the inner concrete are covered with a steel plate.

It is preferable that the annular joint is formed with a through hole capable of inserting and holding the anchoring muscle.

It is preferable that the anchoring muscle is inserted and held in the through hole so as to project by a predetermined anchoring length toward the inner peripheral space side of the annular joint.

The structural portion of the pile foundation is preferably a reinforced concrete underground beam or foundation footings.

In the annular joint, it is preferable that a shear resistor is formed at a joint position of the outer peripheral surface with the structural portion of the pile foundation.

It is preferable that a shear resistor is formed on the inner peripheral surface of the annular joint.

FIG. 5 is a plan sectional view showing a partial cross section of the internal structure of an embodiment of the pile foundation structure of the present invention. The normal sectional view which showed the internal structure of the pile foundation structure along the II-II sectional line in FIG. The plan view and the cross-sectional view which showed the appearance shape of the annular anchor body used for the pile foundation structure of this invention. FIG. 3 is a cross-sectional view showing a state in which an end fixing muscle is attached to the annular fixing body shown in FIG. A plan view and a cross-sectional view showing a state in which a shear resistor is attached to the inner and outer surfaces of the annular fixing body shown in FIG. Explanatory drawing which showed construction procedure of pile foundation structure of this invention (the 1: (a)-(c)). Explanatory drawing which showed construction procedure of pile foundation structure of this invention (part 2: (d), (e)).

Hereinafter, the configuration of the pile foundation structure of the present invention will be described with reference to the accompanying drawings. 1 and 2 show, as one embodiment of the pile foundation structure of the present invention, an underground beam 15 and a pile head of the pile 1 arranged vertically and horizontally in a plan view around the pile head of the pile 1. A part of the appearance and the internal structure of the pile foundation structure 10 for joining the part 2 is shown.

The pile body 1 of the present embodiment is made of a steel pipe pile having a pile outer diameter of 1,000 mmφ, and as shown in FIG. 2, the pile head 2 stiffened with filled concrete (not shown) is the ground surface 5. A square steel pipe column (550 mm □) 4 is erected on the top end surface of the column base plate 3 via a column base plate 3.

The underground beam 15 of the present embodiment is made of a precast reinforced concrete member having a beam length of 2,000 mm and a beam width of 1,000 mm, and is an annular joint installed around the pile head 2 as shown in FIGS. Around the body, a predetermined separated portion 16 is taken and arranged vertically and horizontally so as to form a cross in a plan view, and is placed on a base concrete 6 laid flat on the ground surface 5 and joined concrete 35. (It will be described later.), It is joined to the pile head 2 of the pile body 1 via the annular joint body 20.

The annular joint 20 of the present embodiment is the main constituent member of the present invention that joins the pile head 2 of the pile 1 and the underground beam 15. As shown in each figure of FIG. 3, the annular joint 20 has a hollow cylindrical shape having an annular cross section, and the outer peripheral surface and the inner peripheral surface are covered with the outer peripheral steel plate 21 and the inner peripheral steel plate 22, and the outer peripheral steel plate 21 It is composed of a precast concrete steel plate composite member in which the internal concrete 23 is densely filled between the inner peripheral steel plate 22 and the inner concrete steel plate 22. The dimensions of the annular joint 20 in this embodiment are an outer diameter of 2,300 mm, an inner diameter of 1,300 mm, a height of 2,200 mm, and a thickness of the inner concrete 23 of 500 mm. These dimensions are set based on the cargo bed dimensions of the vehicle on which the factory-made annular joint 20 can be mounted, and may be larger than the above dimensions if there are no dimensional restrictions during transportation. it can. Further, it is preferable to set the inner diameter of the annular joint 20 in consideration of the construction error of the pile position where the pile is placed. For example, the inner diameter of the annular joint 20 is preferably 15% or more of the outer diameter of the pile. By adjusting the installation position of the annular joint 20, it is possible to absorb the deviation of the driving position of the pile 1, and as a result, the underground beam 15 can be installed with high accuracy. The outer peripheral steel plate 21 and the inner peripheral steel plate 22 of the present embodiment have a thickness of 16 mm. The concrete strength of the internal concrete 23 is 27 N / mm ² . It is preferable that the thickness of the steel plate, the strength of the internal concrete 23, and the strength of the filling concrete 36 described later are appropriately set according to the design conditions of the pile foundation structure 10. When high-strength concrete is used, the annular joint 20 can be a precast concrete member that does not have the outer peripheral steel plate 21 and the inner peripheral steel plate 22. Further, in order to integrate the inner concrete 23 with the outer peripheral steel plate 21 and the inner peripheral steel plate 22, it is preferable to dispose a shear resistance material such as flat steel or round steel on the inner surface side (inner concrete 23 side) of the steel plate. ..

As shown in FIG. 3, six through holes 24 are arranged in the upper and lower parts of the annular joint 20 in two upper and lower stages and in the horizontal direction. The through hole 24 is composed of a sheath pipe 25 having a predetermined pipe diameter embedded at a predetermined position so that both ends are supported by the steel plates 21 and 22. The sheath pipe 25 used in the present embodiment has an inner diameter of 42 mmφ, and a deformed steel bar having a diameter of about D35 is inserted into the sheath pipe 25, and the reinforcing bar is held in the hole by grout filling. The inner diameter of the sheath pipe 25 may be set according to the diameter of the short reinforcing bar 31 inserted into the through hole 24 (see FIG. 4).

As shown in FIGS. 1 and 2, a short fixing rebar as a beam end fixing bar previously attached to the annular joining 20 side through the through hole 24 of the annular joint 20 (hereinafter, short reinforcing bar 31). The end portion of the beam main bar 17 of the underground beam 15 is joined, and the joint concrete 35 is cast-in-place concrete at a predetermined separation portion 16 portion between the annular joint 20 and the end face of the underground beam 15. It is cast as. Further, a filling concrete 36 is cast in the inner peripheral space 26 of the annular joint 20. As a result, the pile head 2, the annular joint 20, and the main body of the underground beam 15 of the pile are integrally constructed, and the rigid joint of each member of the pile foundation structure 10 is realized.

FIG. 4 Each figure shows a state in which a short reinforcing bar 31 as a beam end fixing bar is inserted into each through hole 24 of the annular joint 20 carried into the construction site and fixedly held by a filling grout. As described above, the short reinforcing bar 31 has the same diameter as the beam main bar 17 of the underground beam 15 to be joined, and is joined to the beam main bar 17 via a mechanical joint (see FIGS. 1 and 2). A fixing nut 32 is screwed to the end of the short reinforcing bar 31. Further, the protruding length of the short reinforcing bar 31 on the fixing nut 32 side is set so as to secure the required fixing length of the beam main bar 17 of the underground beam 15 in consideration of the fixing effect of the fixing nut 32.

FIG. 5 Each figure shows a shear resistance member provided on a beam joint surface and an inner peripheral surface of the outer peripheral surface of the annular joint 20. As shown in FIGS. 1 and 2, the annular joint 20 and the underground beam 15, which are precast concrete members, are installed by providing a predetermined separation portion 16 including a reinforcing bar joint joint between them. Then, a joint concrete 35 to be post-cast at the site is cast in the separated portion 16, and the annular joint 20 and the underground beam 15 are integrally joined. Further, in the inner peripheral space 26 of the annular joint 20, the filling concrete 36 is cast after the installation. The underground beam 15, the annular joint 20, and the pile head 2 are integrated by the joint concrete 35 and the filling concrete 36.

In order to resist the shearing force generated on the joint surface between the annular joint 20 and the joint concrete 35 and the joint surface between the annular joint 20 and the filled concrete 36, the shear key as a shear resistance member is the annular joint 20. It is attached to the outer peripheral steel plate 21 and the inner peripheral steel plate 22 of the above. In the outer peripheral steel plate 21, a shear key is attached to the joint range with the underground beam 15 as shown by a virtual line in FIG. 5A. As the shear key, a plurality of deformed steel bars 37 and shaped steel 38 are attached to the outer peripheral steel plate 21 at predetermined intervals in the height direction of the annular joint 20. FIG. 3B shows an example of mounting the deformed steel bar 37 (right half view) and the shaped steel 38 (left half view).

On the other hand, a shear key similar to that of the outer peripheral steel plate 21 is attached to the inner peripheral steel plate 22 in order to integrate the annular joint 20 with the filled concrete 36 filled in the inner peripheral space 26. The filling concrete 36 filled in the inner peripheral space 26 by the shear key and the inner concrete 23 of the annular joint 20 are in close contact with each other, and the annular joint 20 and the filling concrete 36 are integrated. Further, a part of the inner peripheral steel plate 22 may be removed to expose the surface of the inner concrete 23, and the annular joint 20 and the filled concrete 36 may be integrated by the exposed portion. Since a part of the short reinforcing bar 31 and the fixing nut 32 are projected and embedded in the filling concrete 36, a sufficient fixing effect can be obtained for the short reinforcing bar 31.

Hereinafter, a construction procedure for constructing the pile foundation structure 10 of the present invention will be described with reference to FIGS. 6 (a)-(c), 7 (d), and (e).

A ready-made pile such as a steel pipe pile is driven as the pile body 1, and a filling concrete (not shown) for stiffening is placed in the pile of the pile head 2 (FIG. 6 (a)). The annular joint 20 so that the holding position of the short reinforcing bar 31 of the annular joint 20 and the bar arrangement position of the beam main reinforcement 17 to which the short reinforcing bar 31 is joined, that is, the axial center direction of the underground beam 15 exactly match. Is installed on the ground surface 5 which is shaped almost horizontally. At this time, the cross-sectional center of the annular joint 20 and the cross-sectional center of the pile need only be substantially concentric, and the error of the pile construction position with respect to the installation position of the underground beam 15 can be absorbed at this stage (FIG. 6 (b). )). At this time, as shown in the figure, the short reinforcing bars 31 are inserted and held in advance at predetermined positions in the through holes 24 of the annular joint 20, so that the positioning work of the underground beam 15 with the beam main bars 17 can be performed. It can be done easily and with high accuracy. At this stage, a steel pipe column 4 is erected on each pile head 2 via a column base plate 3 (FIG. 6 (c)), and then an underground beam 15 to be connected to the annular joint 20 is installed. The base concrete is placed and the underground beam 15 made of precast concrete is placed at a predetermined position on the base concrete. Further, the main bar end protruding from the end of the underground beam 15 and the short reinforcing bar 31 of the annular joint 20 are joined by a mechanical joint 18 (FIG. 7 (d)). In the present embodiment, the beam main bar 17 of the underground beam 15 and the short reinforcing bar 31 of the annular joint 20 are joined by using a sleeve or a coupler previously attached to the beam main bar 17 of the underground beam 15 as the mechanical joint 18. ing.

Finally, in order to integrate the pile head 2 and the underground beam 15 as the foundation structure, the joint concrete 35 is placed in the separated portion 16 between the annular joint 20 and the precast concrete underground beam 15. .. For that purpose, additional reinforcement is arranged in the separation portion 16 between the annular joint 20 and the underground beam 15, a side formwork (not shown) corresponding to the beam width is attached, and the underground beam is inside the formwork. Joined concrete 35 having the same strength as the concrete strength of 15 is placed. At the same time, the filling concrete 36 is placed in the inner peripheral space 26 of the annular joint 20 to solidify the column bases of the pile head 2 and the column 4. As a result, the pile head 2 (pile cap) can be made into a rigid structure, and the pile foundation structure 10 in which the pile head 2 and the underground beam 15 are rigidly joined can be constructed (FIG. 7 (e)).

In each attached figure, a mode in which the underground beam 15 is joined from four directions orthogonal to the annular joint 20 is drawn, but the underground beam 15 is L-shaped or T-shaped in a plan view. It can be applied to outer peripheral piles and corner piles that are joined to the pile head 2 so as to form the above. In this case, the through hole 24 provided in the annular joint 20 may be provided at a position in two right-angled directions or three right-angled directions in accordance with the extension direction of the underground beam 15, for example. Further, it can be assumed that the structural portion joined to the annular joint 20 is a part of the foundation footing in addition to the underground beam 15 described above. In that case, it is preferable that the through hole 24 of the annular joint 20 is provided at a position where a part of the reinforcement arrangement of the foundation footings can be reliably joined to the annular joint 20.

The present invention is not limited to the above-described embodiment, and various modifications can be made within the scope of each claim. That is, an embodiment obtained by combining technical means appropriately modified within the scope of the claims is also included in the technical scope of the present invention.

1 Pile body 2 Pile head 4 Pillars (steel pipe columns)
10 Pile foundation structure 15 Underground beam (structural part)
16 Separation part 17 Beam main bar 18 Mechanical joint 20 Circular joint 21 Outer steel plate 22 Inner peripheral steel plate 23 Internal concrete 24 Through hole 26 Inner peripheral space 31 Fixing bar (short reinforcing bar)
35 Joined concrete 36 Filled concrete

Claims (7)

Pile heads placed with a predetermined protrusion length from the ground surface,
The structural part of the pile foundation to be joined to the pile head,
The pile has an annular shape when viewed in a plan view, holds a fixing bar jointly joined to the main bar end of the structural portion of the pile foundation, and the pile head is located substantially at the center of the inner peripheral space of the annular shape. Equipped with an annular joint installed around the pile head,
The structural portion of the pile foundation is installed with a predetermined separation portion from the outer peripheral surface of the annular joint, and the annular joint is joined in a state where the main bar end of the structural portion of the pile foundation and the anchoring bar are joined. And integrated with joint concrete,
The inner peripheral space of the annular joint is filled with filled concrete.
A pile foundation structure characterized in that the pile head and the structural portion of the pile foundation are joined. The pile foundation structure according to claim 1, wherein the annular joint is a precast concrete member in which the outer peripheral surface and the inner peripheral surface of the inner concrete are covered with a steel plate. The pile foundation structure according to claim 1, wherein the annular joint is formed with a through hole capable of inserting and holding the fixing bar. The pile foundation structure according to claim 3, wherein the anchoring bar is inserted and held in the through hole so as to project by a predetermined anchoring length toward the inner peripheral space side of the annular joint. The pile foundation structure according to claim 1, wherein the structural portion of the pile foundation is an underground beam or foundation footing made of reinforced concrete. The pile foundation structure according to claim 1, wherein the annular joint is a pile foundation structure in which a shear resistor is formed at a joint position of the outer peripheral surface with the structural portion of the pile foundation. The pile foundation structure according to claim 1, wherein the annular joint has a shear resistor formed on the inner peripheral surface.

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