JP4780451B2 - Semi-rigid structure of precast concrete piles - Google Patents

Description

  The present invention relates to a semi-rigid pile head structure for joining a pile head of a ready-made concrete pile and a foundation of a structural frame.

Ready-made concrete piles having hollow shapes such as PHC piles (centrifugal high-strength prestressed concrete piles), SC piles (concrete piles with outer shell steel pipes), and PRC piles (prestressed reinforced concrete piles) have been commercialized. And since these ready-made concrete piles have improved the bearing capacity significantly compared with the conventional embedded pile construction method, the advantage of cost is increasing compared with a cast-in-place concrete pile.
Conventionally, the connection structure between the pile and the building foundation is based on a structure in which the pile head joint is rigidly connected by fixing the main bar of the pile to the foundation. And in the case of a ready-made concrete pile, it was set as the rigid joint which provided the anchor reinforcement and the pile stud at the pile head, and was embedded in the foundation. This structure has a drawback that a pile head joint is damaged due to a large bending stress generated in the pile head during an earthquake. Therefore, the rigidity of the piles and foundations is streamlined by reducing the fixing degree (rotational rigidity) of the pile head by reducing the fixing degree of the joint at the pile head and reducing the bending moment generated at the pile head. A contact structure has been proposed (see, for example, Patent Document 1).
Patent Document 1 is a pile head joint structure in which a cylindrical ring member (joining member) is placed on the outer periphery of a pile head of a ready-made concrete pile, and the pile head and the foundation are joined via this ring member. . This structure reduces the rotational rigidity of the pile head because the pile head is not directly joined to the foundation.
JP 2002-167776 A

  However, since the semi-rigid connection structure in the ready-made concrete pile of Patent Document 1 has no or few joint (contact) portions between the pile main body and the foundation, there is a drawback that the shear strength decreases when the pile axial force is small. It was not a structure that could ensure the tensile strength in the event of an earthquake. Therefore, there has been a need for a suitable structure that can ensure the tensile strength without increasing the rotational rigidity of the pile head, that is, the structure that relaxes the rotational restraining force of the pile head.

  The present invention has been made in view of the above-mentioned problems, and can reduce the rotational rigidity by reducing the rotational restraining force of the pile head with a simple configuration, and can ensure the tensile strength acting in the axial direction of the pile. The purpose is to provide a semi-rigid structure of precast concrete piles.

In order to achieve the above object, in the pile head semi-rigid connection structure of the ready-made concrete pile according to the present invention, a shock-absorbing member that covers the outer periphery of the pile end is provided on the pile head of the ready-made concrete pile, and the shock-absorbing member is a structure was embedded in the foundation of the building frame, the pile head and is constructed by joining the basis through the concrete filled in formed by pouring into a hollow portion of the inner pile body concrete having a cylindrical shape constituting a prefabricated concrete pile, ready-made A large number of headed studs are arranged on the inner peripheral part of the concrete pile, and the tip of each headed stud protrudes from the inner peripheral surface of the pile concrete .
In the present invention, for example, when a bending moment acts on the pile head due to the occurrence of an earthquake or the like, the buffer member made of, for example, a rubber material provided on the outer periphery of the pile end of the pile head is crushed by elastic deformation. And deform. Therefore, the ready-made concrete pile can be rotated within the range of this deformation. That is, an increase in rotational rigidity at the pile head can be suppressed, and a semi-rigid connection structure can be realized. Moreover, the tensile strength can be ensured by reliably transmitting the axial force between the pile and the structural frame via the filled concrete.
Moreover, it can be set as the structure which reinforces the tensile strength of a pile and can resist by providing the headed stud integrated with a structure housing via filling concrete in the hollow part of a ready-made concrete pile.

Moreover, in the pile head semi-rigid connection structure of the ready-made concrete pile which concerns on this invention, it is preferable that the 2nd buffer member is provided in the upper end of pile body concrete.
In the present invention, the contact between the upper end of the pile head and the foundation is eliminated by the second buffer member, and therefore, the ready-made concrete pile and the foundation are joined only with the middle-filled concrete of the hollow portion of the pile. Since the pile cross-sectional area in contact with the foundation is thus reduced, the rotational rigidity is further reduced.

Further, in the pile head semi-rigid connection structure of the ready-made concrete pile according to the present invention, a plurality of anchor bars protrude above the pile head and are arranged in the pile axial direction in the hollow portion of the ready-made concrete pile. Is preferred.
In this invention, it can be set as the structure which reinforces the tensile strength of a pile and can resist by arrange | positioning the anchor reinforcement integrated with a structure frame via filling concrete in the hollow part of a ready-made concrete pile.

  According to the pile head semi-rigid structure of the ready-made concrete pile of the present invention, for example, when a bending moment acts on the pile head due to the occurrence of an earthquake or the like, the ready-made concrete pile can be rotated within the deformation range of the buffer member. The rotation restraint force of the pile head can be relaxed. That is, an increase in rotational rigidity at the pile head can be suppressed, and a semi-rigid structure can be realized. Moreover, the tensile strength can be ensured by reliably transmitting the axial force between the pile and the structural frame via the filled concrete.

Hereinafter, a first embodiment of a pile head semi-rigid connection structure of a ready-made concrete pile according to the present invention will be described with reference to FIG.
Fig.1 (a) is a vertical sectional view of the pile head of the ready-made concrete pile of 1st embodiment, (b) is a top view of the assembly reinforcement arrange | positioned at the pile head.

As shown to Fig.1 (a) and (b), the ready-made concrete pile 10 is a PHC pile (centrifugal high-strength prestressed concrete pile).
In this semi-rigid pile head structure of the ready-made concrete pile 10, a large number of headed studs 20 are arranged on the inner periphery of the hollow pile head 10 a, and the tip of each headed stud 20 constitutes the ready-made concrete pile 10. It is made to project from the inner peripheral surface of the pile concrete 11 having a cylindrical shape, and an end plate 12 is arranged on the upper end surface of the ready-made concrete pile 10, and a pile end outer peripheral portion 10 b (the pile head 10 a of the pile head 10 a) The buffer member 13 that covers the portion embedded in the foundation 50 is provided.

  In the pile concrete 11, there are a plurality of fixed plates 22, which are cylindrical cage-like support members, extend in the axial direction of the ready-made concrete piles 10, and have one ends joined to the end plates 12 of the pile heads 10 a. And hoop-like assembly bars 23 that hold the outer periphery at intervals in the circumferential direction, and the base end of the headed stud 20 is joined to the inner surface of each fixing plate 22 to form an integral frame shape. A support member 21 is formed.

The buffer member 13 has a sheet shape with a thickness of about several centimeters, for example. For example, a material having elasticity such as soft rubber having high water-stopping property and small rigidity is adopted.
This buffer member 13 corresponds to the rotational force in the pile head 10a. That is, when a rotational force acts on the pile head 10a, the buffer member 13 provided on the pile end outer peripheral portion 10b of the pile head 10a is deformed so as to be crushed by elastic deformation. Therefore, the ready-made concrete pile 10 can be rotated within the range of this deformation. In addition, the buffer member 13 is arrange | positioned irrespective of the presence or absence of the tensile proof stress which acts on a pile.

On the upper surface of the end plate 12, for example, a second buffer member 14 made of a foaming material such as elastite (registered trademark, manufactured by Sanko Chemical Industry Co., Ltd.) is provided. By providing the second buffer member 14, only the filling concrete 15 in the hollow portion of the pile 10 is directly connected to the upper foundation 50.
At this time, the joint area between the pile 10 and the foundation 50 (corresponding to the area of the circular portion inside the end plate 12 or the second buffer member 14 and the hollow portion) is substantially half of the entire cross section of the pile 10, for example. . Specifically, pile head rotational rigidity is reduced, so that the cross-sectional area (diameter of a contact part) of the pile 10 which contact | connects the foundation 50 is small. Since the inner diameter of the inner space in the case of a PHC pile is approximately 0.7 times the pile diameter, the entire head section of the pile is brought into contact with the foundation 50 by bringing only the hollow portion into contact with the foundation 50 at the pile head 10a. The pile head rotational rigidity can be reduced to about 1/3.

In addition, a plurality of anchor bars 30 are arranged in the center of the cross section of the ready-made concrete pile 10 so as to protrude upward from the pile head 10a. The anchor bar 30 is fastened at a predetermined location by a hoop-shaped assembly bar 31, and a receiving bar 32 is provided on the upper portion of the end plate 12. The receiving bar 32 supports the assembly bar 31, and the pile top end (second buffer member 14). The weight of the anchor muscle 30 is received.
In place of the anchor bars 30, anchors can be obtained by using T head bars (registered trademark, manufactured by Shimizu Corporation), reinforcing bars, etc., in which the ends of the anchor bars 30 are enlarged. The length dimension may be shortened.

As described above, since a large number of headed studs 20 and a plurality of anchor bars 30 are disposed on the inner peripheral side of the hollow pile head 10a, by placing the filling concrete 15 therein, the headed studs 20 and The shear resistance force and fixing force of the anchor bars 30 are ensured, and the integrity of the filling concrete 15 and the ready-made concrete pile 10 can be enhanced.
Therefore, it is possible to reliably transmit the axial force between the ready-made concrete pile 10 and the structural frame via the filling concrete 15 without performing special additional work, and the construction cost can be reduced. Moreover, by using the support member 21, the headed stud 20 can be easily disposed, and the ready-made concrete pile 10 can be easily manufactured.

Next, the construction of the pile head semi-rigid structure of the ready-made concrete pile 10 will be described.
As shown in FIGS. 1 (a) and 1 (b), first, the headed stud 20 is welded to the fixed plate 22 so that the head protrudes into the hollow portion of the pile, and then the pile concrete 11 is placed. And ready-made concrete piles.
First, in order to support the structural frame, the ready-made concrete pile 10 is erected on the ground such that the buffer member 13 is embedded in the foundation 50. In this case, although the tip of the headed stud 20 protrudes into the hollow portion of the pile head 10a of the ready-made concrete pile 10, even if an embedding method (pre-boring type) or a hammering method is adopted as the pile construction method. The headed stud 20 does not become an obstacle to the construction, and the conventional construction method can be followed as it is.
Subsequently, the filling concrete 15 for linking with the structure frame is placed on the pile head 10a. At this time, reinforcing anchor bars 30 are installed in the hollow portion of the pile head 10a as necessary.

  In the semi-rigid connection structure of the ready-made concrete pile according to the first embodiment described above, when the rotational force is applied to the pile head 10a due to the occurrence of an earthquake, for example, the ready-made concrete pile 10 is deformed by the buffer member 13. It becomes possible to rotate within the range, and the rotational restraining force of the pile head 10a can be relaxed. That is, an increase in rotational rigidity in the pile head 10a can be suppressed, and a semi-rigid connection structure can be realized. In addition, the tensile strength can be ensured by reliably transmitting the axial force between the pile and the structural frame via the filling concrete 15.

Next, a second embodiment of the present invention will be described with reference to FIG. 2, but the same or similar members and parts as those in the first embodiment described above are denoted by the same reference numerals and description thereof is omitted. A configuration different from that of the first embodiment will be described.
Fig.2 (a) is an elevation sectional view of the pile head of the ready-made concrete pile of 2nd embodiment, (b) is a top view of the assembly reinforcement arrange | positioned at the pile head.
As shown in FIGS. 2 (a) and 2 (b), the ready-made concrete pile 10 in the second embodiment is an SC pile (concrete pile with a shell steel pipe) in which a shell steel pipe 42 is arranged on the outer periphery of a pile concrete 41. ) Is applied to the present invention. The ready-made concrete pile 40 is manufactured by joining the base end of the headed stud 20 to the inner circumference of the outer shell steel pipe 42 by welding or the like, and driving the pile concrete 41. The end plate 12 is connected to the upper end portion of the pile head 40a by welding. And the buffer member 13 is provided in the pile end outer peripheral part 40b similarly to 1st embodiment.
In addition, in 2nd Embodiment, since the 2nd buffer member 14 (refer FIG. 1) of 1st Embodiment is abbreviate | omitted, it is a structure which contacts the foundation 50 at the upper end surface of the pile head 40a. For this reason, since the contact area with the foundation 50 is large compared with the structure where the hollow part of the pile of 1st embodiment (refer FIG. 1) and the foundation 50 contact, the rotational rigidity of a pile will increase.
In the semi-rigid connection structure as in the second embodiment, for example, a high strength pile method with a large support force (the support force for the ground is increased by providing a node protruding outward from the outer periphery of the pile). It is preferable to adopt it for piles by construction method. That is, in the case of a high strength pile, the compressive stress of the portion on which the rotational rigidity acts increases, so that the upper end surface of the pile 10 may be brought into contact with the foundation 50 as in the second embodiment. In short, the contact area between the upper end face of the pile and the foundation 50 as described above may be set in consideration of the balance between the axial force acting on the ready-made concrete pile and the bending moment.

As mentioned above, although the 1st and 2nd embodiment of the pile head semi-rigid connection structure of the ready-made concrete pile by this invention was described, this invention is not limited to said 1st and 2nd embodiment. However, it can be changed as appropriate without departing from the spirit of the invention.
For example, in the first and second embodiments, the anchor bars 30 are basically arranged in a circular shape in plan view, but avoid interference with the bar arrangement provided in the horizontal direction of the foundation 50 constructed on the top of the pile. Therefore, they may be arranged in a square shape in plan view.
Moreover, although the PHC pile is used in the first embodiment, and the ready-made concrete piles 10 and 40 of the SC pile are used in the second embodiment, the present invention is not limited to these, and PRC (prestressed reinforced concrete pile) is also used. Etc. are subject to ready-made concrete piles.
The anchor bars 30 may be provided when a tensile strength is generated in the pile, and may not be provided when the tensile strength does not act. Then, by covering the anchor muscle 30 with a sheath tube or the like and providing a non-adhesive portion between the anchor muscle 30 and the sheath tube, the flexible length is increased to suppress an increase in the degree of fixation (rotational rigidity). May be.
Further, the number, the diameter, the material type of the anchor bars 30 and the diameter and the number of the headed studs 20 are not limited to those in the first and second embodiments, and may be appropriately set according to the construction conditions. That's fine.

(A) is an elevation sectional view of a pile head of a ready-made concrete pile according to the first embodiment of the present invention, and (b) is a plan view of an assembly bar arranged on the pile head. (A) is an elevation sectional view of a pile head of a ready-made concrete pile according to the second embodiment of the present invention, and (b) is a plan view of an assembly bar arranged on the pile head.

Explanation of symbols

10, 40 Ready-made concrete piles 10a, 40a Pile head 10b, 40b Pile end outer periphery 11, 41 Pile body concrete 12 End plate 13 Buffer member 14 Second buffer member 15 Filled concrete 20 Headed stud 30 Anchor reinforcement 50 Foundation

Claims (3)

Provide a cushioning member with elasticity to cover the outer periphery of the pile end on the pile head of the ready-made concrete pile,
The buffer member is embedded in the foundation of the structure housing;
The pile head is configured to be joined to the foundation via a filling concrete formed by placing in a hollow portion inside a pile body concrete forming a cylindrical shape constituting the ready-made concrete pile ,
A pile head of a ready-made concrete pile, wherein a number of studs with heads are arranged on the inner peripheral part of the ready-made concrete pile, and the tips of the studs with heads protrude from the inner peripheral surface of the pile body concrete. Semi-rigid structure. The pile head semi-rigid connection structure of a ready-made concrete pile according to claim 1, wherein a second buffer member is provided at an upper end of the pile concrete. 3. The ready-made concrete pile according to claim 1, wherein a plurality of anchor bars protrude above the pile head and are arranged in a pile axis direction in the hollow portion of the ready-made concrete pile. Pile head semi-rigid structure.

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