JP2006089929A - Pile head connection structure and method of connecting the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pile head connection structure which reduces stress occurring at a pile head to prevent breakage of the pile head, and transmits shear force from a foundation to a pile even if axial pull strength occurs at the pile, and to provide a method of connecting the pile head. <P>SOLUTION: According to the pile head connection structure, the pile head 2 has a bearing portion 3 set on the center of a pile head surface 2a, which bearing portion is smaller in diameter than the pile head 2 and formed of a flanged steel pipe 5 with a plate-like ring flange annularly arranged on a peripheral surface thereof, and infilling concrete 6 filled in the flanged steel pipe 5. Then, the steel reinforced concrete foundation 8 is constructed on the bearing portion 3. The pile head 2 has a plurality of rod-like joint reinforcements 4 arranged at a cross sectional center thereof in a pile core direction, and each joint reinforcement 4 extends from the pile head 2 to penetrate the infilling concrete 6, and it is anchored in the foundation 8. A pile main reinforcement 7 arranged in a peripheral portion of the pile 1 is not anchored in the foundation 8 but remains in the pile head 2. Further, backfill soil enclosing the flanged steel pipe 5 is formed of sand 10 having a granular cellular material like foamed polyethylene beads mixed therein. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pile head joint structure and a construction method thereof.

Conventionally, in the joint structure between the pile head and the foundation supported by the pile, a method has been adopted in which the main reinforcement of the pile is extended upward from the pile head by a predetermined length and fixed in the foundation frame. It has been. However, when a large horizontal force is applied to the pile foundation due to an earthquake or the like, the pile head may be destroyed due to excessive stress generated in the pile head. A pile head joint structure has been proposed to alleviate this. For example, in patent document 1, the joint part of a pile head and a foundation is made into a truncated cone shape, and the main part of a pile body is fastened to a pile head, and it connects with a foundation by the joint reinforcement arrange | positioned in the pile core vicinity, and a pile head Support structures for structure foundations that reduce the rotational rigidity of the structure have been proposed.
JP-A-2002-242207 (page 3-4, FIG. 1-3)

  However, in piles arranged in the periphery of the foundation, axial tensile force may act on the pile due to axial force fluctuation at the time of earthquake, and in the semi-rigid joint structure described in Patent Document 2, Although it can be dealt with with jointed reinforcing bars, there is a problem that the transmission of shear force during earthquake from the foundation to the pile becomes insufficient, and that shear force must be borne by other piles.

  The present invention has been made in view of the above-described problems, and reduces the stress generated in the pile head to prevent the pile head from being destroyed, and also when the axial tensile force is generated in the pile, from the foundation to the pile. It is an object of the present invention to provide a pile head joint structure capable of transmitting a shearing force and a construction method thereof.

In order to achieve the above object, a pile head joint structure according to the present invention is a joint structure between a pile head and a foundation supported by the pile, and has a smaller diameter than the pile head. A bearing portion in which concrete is filled in a flanged steel pipe in which a ring-shaped flange is mounted on the outer peripheral portion is interposed between the pile head and the foundation; A joining rebar disposed in the center of the cross section and extending from the pile head penetrates the concrete in the flanged steel pipe and is embedded in the foundation.
In the present invention, a bearing portion, which has a smaller diameter than the pile head and is filled with concrete in a flanged steel pipe with a ring-shaped flange mounted around the outer periphery, is interposed between the pile head and the foundation. Since the pile head and the foundation are connected by the joint rebar that penetrates the support part, the rigidity of the pile head joint is reduced, and the bending moment acting on the pile head is greatly reduced. Moreover, even when an axial tensile force is generated in the pile, the shearing force during earthquake is transmitted from the foundation to the pile through the flanged steel pipe. As a result, the pile head is not damaged even during a large earthquake. In addition, as the pile head stress is reduced, the pile section and foundation frame section are reduced, the amount of excavated sand is reduced, construction costs can be reduced, construction period can be shortened, and the environmental load is also reduced. .

In the pile head joint structure according to the present invention, a granular foam material may be mixed in the backfill sand surrounding the flanged steel pipe.
In the present invention, by mixing granular foaming material such as foamed polyethylene beads into the backfill sand on the pile head surrounding the flanged steel pipe, the rotation of the pile head is not hindered and the pile head rotates smoothly during an earthquake. can do.
In addition, as long as the backfill sand is of a quality that does not hinder the rotation of the pile head, only the sand may be used without mixing the granular foam material.

The pile head joint construction method according to the present invention is a pile head construction method having the above-mentioned joint structure, and extends from the pile head to the center of the cross section above the pile hole formed in the ground. The joint rebar is disposed so as to come out, and is embedded temporarily in the center of the cross section above the pile hole so that the joint rebar is included in a plan view and the lower end is embedded in the pile head. After setting the member, setting the lower end of the flanged steel pipe in the recess formed on the pile head by removing the temporary embedded member and placing the concrete in the pile hole, Filling the flanged steel pipe with concrete; and refilling the periphery of the flanged steel pipe with sand or sand mixed with granular foam, and then forming a foundation on the flanged steel pipe. It is characterized by that.
In the present invention, a bearing portion filled with concrete in a steel pipe with a flange is interposed between the pile head and the foundation, and the pile head and the foundation are connected by a joining rebar inserted through the flanged steel pipe. Thus, the pile head can be easily semi-rigidly joined.

  In the present invention, a bearing portion, which has a smaller diameter than the pile head and is filled with concrete in a flanged steel pipe with a ring-shaped flange mounted around the outer periphery, is interposed between the pile head and the foundation. Since the pile head and the foundation are connected by the jointed reinforcing bar that penetrates the support part, the pile head is easy to rotate, the stress generated in the pile head is reduced, and the pile head is destroyed. Is prevented. Even when an axial tensile force is generated in the pile, the shearing force during an earthquake is smoothly transmitted from the foundation to the pile via the flanged steel pipe. In addition, as the pile head stress is reduced, the cross section of the pile body and the cross section of the foundation frame are reduced, the amount of excavated sand is reduced, and the construction period and cost can be reduced.

Hereinafter, an embodiment of a pile head joint structure according to the present invention will be described with reference to the drawings.
[Pile head joint structure]
FIG. 1 is a vertical sectional view showing an embodiment of a pile head joint structure according to the present invention. In addition, since a figure becomes complicated, the reinforcement of a foundation and the horizontal reinforcement of a pile are not illustrated in the figure.

The target pile in this embodiment is a cast-in-place concrete pile.
In the center portion of the pile head surface 2a, a bearing portion having a smaller diameter than the pile head surface 2 and filled with concrete stuffed concrete 6 in a flanged steel pipe 5 in which a flat ring-shaped flange is mounted on the outer periphery. 3 is installed, and a reinforced concrete foundation 8 is constructed on the support 3. At this time, the lower end portion of the flanged steel pipe 5 is embedded in the pile head 2, and the upper end portion of the flanged steel pipe 5 is embedded in the foundation 8 so that the bearing portion 3, the pile head 2 and the foundation 8 are integrated. Try to make it easier.
Further, a plurality of rod-shaped joining reinforcing bars 4 are arranged in the center of the cross section of the pile head 2 in the pile core direction. The plurality of joint reinforcing bars 4 extend from the pile head 2 and are anchored in the foundation 8 through the filled concrete 6 in the flanged steel pipe 5. On the other hand, the pile main reinforcement 7 disposed on the peripheral edge of the pile 1 is not anchored in the foundation 8 but remains in the pile head 2.

FIG. 2 is a plan sectional view and an elevation sectional view of the flanged steel pipe 5. FIG. 3 is a perspective view of the flanged steel pipe 5.
The flanged steel pipe 5 is obtained by welding a flat ring-shaped upper flange 5b and a lower flange 5c to the outer periphery of a cylindrical steel pipe 5a, and between the upper flange 5b and the lower flange 5c, In order to prevent local buckling, ribs 5d made of a flat plate are arranged radially in plan view.
In this invention, since the upper flange 5b and the lower flange 5c are attached to the outer peripheral part of the steel pipe 5a, a larger bending moment can be processed compared with the case of only the steel pipe 5a.
The rib 5d between the upper flange 5b and the lower flange 5c does not necessarily have to be installed, and may be installed as appropriate according to the stress state acting on the flanged steel pipe 5.

  For the backfill surrounding the flanged steel pipe 5, sand 10 mixed with granular foam such as high quality sand or foamed polyethylene beads is used. Thereby, the pile head 2 can rotate smoothly at the time of an earthquake, without inhibiting the rotational resistance of the pile head 2.

In the joint structure of the pile head according to the present embodiment, the filling concrete 6 is filled in a flanged steel pipe 5 having a smaller diameter than the pile head 2 and having a flat ring-shaped flange mounted around the outer periphery. Since the support part 3 is interposed between the pile head 2 and the foundation 8 and the pile head 2 and the foundation 8 are connected by the joining rebar 4 penetrating the support part 3, the pile head joint part The bending moment acting on the pile head 2 is greatly reduced, and even when an axial tensile force is generated on the pile 1, the shearing force during earthquake is generated from the foundation 8 via the flanged steel pipe 5. 1 is transmitted. As a result, the pile head 2 is not damaged even by a large earthquake. Further, along with the reduction of the pile head stress, the pile body cross section and the foundation frame cross section can be reduced, and the amount of excavation and unloading earth and sand can be reduced, so that the construction cost and construction period can be reduced.
Further, in the pile head joint structure according to this embodiment, the pile head can be changed by changing the material and size of the members constituting the flanged steel pipe 5, the strength of the filling concrete 6, or the diameter and number of the joint reinforcing bars 4. It is possible to easily cope with the magnitude of the acting load acting on the second.

[Pile head joint construction method]
Next, the construction method of the pile head joint part concerning this invention is demonstrated.
FIG. 4 shows the construction method of the pile head joint according to the present invention in order. In addition, since this figure also becomes complicated like FIG. 1, the reinforcement of the foundation and the horizontal reinforcement of the pile are not shown.

First, the ground G is excavated using an earth drill (not shown) or the like to form the pile hole 13. Next, after the reinforcing bar 7 'is built in the pile hole 13, the column-shaped temporary embedding member 11 made of expanded polystyrene or the like is piled so that the lower end portion thereof is embedded in the pile head 2 by about 10 cm. Set in the center of the cross section above the hole 13. At the same time, the rod-shaped joining rebar 4 is inserted into a plurality of through holes (not shown) provided in the temporary embedding member 11 and joined so as to extend from the pile head 2 to the center of the cross section of the pile hole 13. A reinforcing bar 4 is disposed (see FIG. 4A). At this time, the temporary embedding member 11 and the joining reinforcing bar 4 are set aside from the pile main reinforcing bars 7 constituting the reinforcing bar 7 'so as not to float when the concrete 12 is placed.
Note that the bonded reinforcing bar 4 and the temporary embedded member 11 may be assembled integrally with the reinforcing bar 7 'and built at the same time.
Next, a tremy pipe (not shown) is inserted into the pile hole 13, and the concrete 12 is placed from the tremy pipe into the pile hole 13 (see FIG. 4B).
When the concrete 12 is hardened, the periphery R of the surplus concrete 12a is excavated, and the surplus concrete 12a is crushed and removed (see FIG. 4C). In cast-in-place concrete piles, mud, slime, etc. concentrate on the pile head 2 and the quality of the concrete 12 deteriorates. Therefore, an extra 500 to 800 mm of concrete 12 is cast from the top of the design pile, and after the concrete 12 is hardened The concrete 12a is crushed and removed to ensure the quality of the pile 1. In the present embodiment, the temporary embedding member 11 made of foamed polystyrene or the like is installed so as to enclose the joining rebar 4, so that the extra concrete 12 a around the joining rebar 4 can be easily removed.
Next, the joining rebar 4 is inserted into the steel pipe 5a of the flanged steel pipe 5, and the flanged steel pipe 5 is inserted into the recess 2b having a depth of about 10 cm formed by the temporary embedding member 11 at the center of the pile head surface 2a. The lower end is inserted and set (see FIG. 4C).
Then, while filling the steel pipe 5a of the flanged steel pipe 5 with the inside-filled concrete 6, the gap between the lower flange 5c of the flanged steel pipe 5 and the pile head surface 2a is filled with the non-shrink mortar 9, and the pile from the lower flange 5c The stress is transmitted to 1 (see FIG. 4D).
Then, after refilling the circumference R of the flanged steel pipe 5 with sand 10 mixed with high-quality sand or granular foam material such as foamed polyethylene beads, a reinforcing bar (not shown) is arranged on the flanged steel pipe 5. Then, a formwork (not shown) of the foundation 8 is built, and concrete is placed in the formwork to construct the foundation 8 (see FIG. 4 (e)). At this time, the bottom surface of the foundation 8 is supported by the upper flange 5 b so that stress is transmitted from the upper flange 5 b to the pile 1.

  In the construction method of the pile head joint portion according to the present embodiment, the bearing portion 3 in which the intermediate concrete 6 is filled in the flanged steel pipe 5 is interposed between the pile head 2 and the foundation 8, and the flanged steel pipe 5 is provided. By connecting the pile head 2 and the foundation 8 by the joining rebar 4 inserted through the inside, the pile head 2 can be easily semi-rigidly joined.

As mentioned above, although embodiment of the joining structure of the pile head concerning this invention was described, this invention is not limited to said embodiment, It can change suitably in the range which does not deviate from the meaning. For example, in the above-described embodiment, filling of the filled concrete in the flanged steel pipe and placement of the foundation concrete are performed in separate processes, but after setting the flanged steel pipe on the pile head, earth and sand etc. The upper surface of the flanged steel pipe may be cured so as not to enter, and the flanged steel pipe may be filled with concrete when the foundation concrete is placed.
Moreover, in said embodiment, in order to form a recessed part on a pile head, although the temporary embedding member is used, when using a temporary embedding member and removing surplus concrete, it removes. You may form a recessed part over the pile head surface. In short, it is only necessary to obtain the desired function in the present invention.

It is an elevation sectional view showing one embodiment of a pile head joint structure concerning the present invention. (A) is a plane sectional view of a steel pipe with a flange, and (b) is an elevation sectional view thereof. It is a perspective view of a steel pipe with a flange. It is an elevation sectional view showing a construction method of a pile head junction concerning the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pile 2 Pile head 2a Pile head surface 2b Recess 3 Bearing part 4 Joining rebar 5 Steel pipe 5b with flange Upper flange (flange)
5c Lower flange (flange)
5d Rib 6 Filled concrete 7 Pile main reinforcement 7 'Reinforcement bar 8 Foundation 9 Non-shrink mortar 10 Sand 11 Temporary embedding member 12 Concrete 12a Extra pile concrete 13 Pile hole G Ground

Claims (3)

It is a joint structure between the pile head and the foundation supported by the pile,
A bearing portion having a smaller diameter than the pile head and filled with concrete in a flanged steel pipe with a ring-shaped flange mounted around the outer periphery is interposed between the pile head and the foundation. As well as
A pile head characterized in that a joint reinforcing bar disposed in the center of the cross section of the pile head and extending from the pile head penetrates the concrete in the flanged steel pipe and is embedded in the foundation. Part joining structure.   The pile head joint structure according to claim 1, wherein the ground around the pile head surrounding the flanged steel pipe is backfilled with sand mixed with sand or a granular foam material. A method for constructing a pile head having the joint structure according to claim 1 or 2,
In the center of the cross section above the pile hole formed in the ground, the joint rebar is arranged so as to extend from the pile head, and the joint rebar is included in a plan view, and the lower end is inside the pile head So as to be embedded in, after setting the temporary embedded member in the central portion of the cross section above the pile hole, and placing concrete in the pile hole;
Setting the lower end of the flanged steel pipe in a recess formed on the pile head by removing the temporary embedded member, and filling the flanged steel pipe with concrete;
And a step of forming a foundation on the flanged steel pipe after the periphery of the flanged steel pipe is backfilled with sand or sand mixed with a granular foam material.

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