JP7556827B2 - Pile head construction method - Google Patents

Description

The present invention relates to a pile head structure for a precast concrete pile and its construction method.

Composite steel pipe concrete piles, which are constructed by casting concrete into a steel pipe as the outer shell and integrating it with centrifugal molding, are widely used in the fields of architecture and civil engineering. As a technique for using such composite steel pipe concrete piles as precast concrete piles and connecting the piles to footings, for example, Patent Document 1 discloses a configuration in which a sleeve-pressed screw joint is attached to the end plate of a precast concrete pile, and a reinforcing steel bar pressed into this sleeve-pressed screw joint is embedded in one end of the concrete part.

According to the configuration disclosed in Patent Document 1, for example, when connecting a pile and a footing, it is possible to achieve the desired performance as a connection structure using a joint means by introducing torque into the sleeve without taking measures such as chipping to expose the reinforcing steel bars for the footing connection or welding the reinforcing steel bars for the footing connection to the outer periphery of the pile.

JP 2010-144391 A

As described above, even in the configuration according to the conventional technology disclosed in, for example, Patent Document 1, it is possible to introduce torque into the sleeve to achieve a predetermined performance as a joint structure, but the conventional configuration has the following problems. That is, in the conventional configuration, it is difficult to make the surface of the end plate and the surface of the sleeve the same. For example, if the surface of the sleeve is located below the end plate, when torque is introduced into the flange of the connection bolt, the flange hits the end plate, and the torque cannot be introduced sufficiently, and there is a risk that the reinforcing bars to be connected will not be able to perform sufficiently. In order to reliably introduce torque, it is necessary for the surface of the sleeve and the flange of the connection bolt to abut reliably. To achieve this, it is possible to make the surface of the sleeve protrude from above the end plate, but in the first place, when manufacturing a pile structure, if the surface of the sleeve is located above the end plate and a protruding portion is provided, there is a risk that the protruding portion will interfere with the manufacturing machine and cause damage, so there was no pile head structure with such a configuration in the past.

The inventors therefore conducted extensive research into a pile head structure and construction method that can fully utilize the mechanical performance of the pile head reinforcing bars and the pile interior reinforcing bars when connecting the pile head reinforcing bars and the pile interior reinforcing bars in the pile head structure of a precast concrete pile.

In view of the above circumstances, the object of the present invention is to provide a pile head structure and construction method thereof that avoids problems such as interference with manufacturing machinery during the manufacture of the pile structure and damage during concrete pouring, even when the tip of the joint material inside the pile is already protruding from the pile head end plate, and that ensures that torque is introduced into each joint material and that the performance of both the pile head reinforcing bar and the reinforcing bar inside the pile can be fully demonstrated, since the pile structure has the joint material inside the pile protruding from the pile head end plate.

According to the present invention, there is provided a method for constructing a pile head structure of a precast concrete pile, the method comprising the steps of: inserting a plurality of internal pile reinforcing bars each having an internal pile joint material at its end into a steel pipe; fixing the internal pile reinforcing bars in a state in which the tips of the internal pile joint materials protrude as protrusions of a predetermined length from holes formed in an end plate fixed to the top end of the steel pipe; providing a template having mounting holes formed therein on the upper surface of the end plate so that the protrusions can be inserted into the mounting holes; fixing the template to the end plate; pouring concrete into the steel pipe; removing the template after the concrete has hardened; connecting the internal pile reinforcing bars each having an external pile joint material at its end to the protrusions; and crimping the internal pile joint materials and the external pile joint materials together.

According to the present invention, even if the tip of the joint material inside the pile is already protruding from the pile head end plate, problems such as interference with the manufacturing machine during the manufacturing of the pile structure and damage during concrete pouring can be avoided, and since the joint material inside the pile protrudes from the end plate of the pile head, torque can be reliably introduced into each joint material, and a pile head structure and construction method therefor can be realized that can fully demonstrate the performance of both the pile head reinforcing bar and the reinforcing bar inside the pile.

1 is a schematic explanatory diagram showing a configuration of a pile head structure according to an embodiment of the present invention. FIG. 2 is a schematic explanatory diagram showing a pile structure in a stage prior to connecting the pile head reinforcing bar. FIG. 2 is a schematic enlarged view of the upper end of the pile structure. FIG. 2 is a schematic plan view of a displacement prevention material. FIG. 1 is a schematic explanatory diagram of a manufacturing method of a pile structure. FIG. 1 is a schematic explanatory diagram of a manufacturing method of a pile structure. FIG. 1 is a schematic explanatory diagram of a manufacturing method of a pile structure. FIG. 1 is a schematic explanatory diagram of a manufacturing method of a pile structure. FIG. 1 is a schematic explanatory diagram of a construction method for a pile head structure. FIG. 13 is a schematic explanatory diagram of a template according to a first modified example of the present invention. FIG. 13 is a schematic explanatory diagram of a template according to a 2-1st modified example of the present invention. FIG. 13 is a schematic explanatory diagram of a template according to a 2-2 modified example of the present invention. FIG. 13 is a schematic explanatory diagram of a protective member according to a third modified example of the present invention. FIG. 13 is a schematic explanatory diagram of a protective member according to a fourth modified example of the present invention.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In this specification and the drawings, components having substantially the same functional configuration are designated by the same reference numerals, and duplicated explanations will be omitted.

<Pile head structure configuration>
FIG. 1 is a schematic diagram showing the configuration of a pile head structure 1 according to an embodiment of the present invention, and is a side cross-sectional view of the pile head structure 1. As shown in FIG. 1, the pile head structure 1 includes a cylindrical steel pipe 10, a concrete portion 20 that is cast with the steel pipe 10 as an outer shell and integrated by centrifugal force forming, and a plurality of pile inner reinforcing bars 30 arranged inside the concrete portion 20, and the pile inner reinforcing bars 30 and the pile head reinforcing bars 40 are connected via a pile inner joint material 32 and a pile outer joint material 42. An end plate 50 is provided at the top end of the steel pipe 10 (one end shown in FIG. 1). The end plate 50 may be, for example, a flat steel member or a rubber plate.

As shown in FIG. 1, a hole 52 is formed in the end plate 50, and the pile internal joint material 32 provided at the end of the pile internal reinforcing bar 30 is inserted into the hole 52, and a part (upper end) of the pile internal joint material 32 protrudes from the upper surface of the end plate 50 to form a protruding portion 32a. The pile internal joint material 32 (protruding portion 32a) is connected to the upper end of the pile internal joint material 32 (protruding portion 32a) to the pile head reinforcing bar 40 equipped with the pile external joint material 42. The pile internal joint material 32 and the pile external joint material 42 are cylindrical so-called sleeve members, and are fixed to the pile internal reinforcing bar 30 and the pile head reinforcing bar 40, respectively, by means of crimping or the like. In addition, a threaded portion may be formed on the inner peripheral surface of the pile internal joint material 32 and the pile external joint material 42 at the portion where the relay bolt 55 is screwed. The means of connection between the pile internal joint material 32 and the pile external joint material 42 is arbitrary, but may be, for example, a relay bolt 55, and the structure of the relay bolt 55 may be, for example, a general full-thread bolt or a full-thread bolt with a flange formed in the center.

<Configuration of pile structure before connecting pile head reinforcing bars>
Fig. 2 is a schematic explanatory diagram showing a pile structure 2 in a stage prior to constructing a pile head structure 1, i.e., a stage prior to connecting a pile head reinforcing bar 40 having a pile outer joint material 42. Fig. 2(a) is a schematic plan view, and Fig. 2(b) is a schematic vertical sectional view. Fig. 3 is a schematic enlarged view of the upper end of the pile structure 2. As shown in Fig. 2(a), a plurality of holes 52 and mounting holes 62 are formed in the circumferential direction in the end plate 50 and a template 60 described later, and the pile inner joint materials 32 provided at the ends of a plurality of pile inner reinforcing bars 30 are inserted into each of the holes 52 and mounting holes 62.

As shown in Figures 2 and 3, an end plate 50 is provided on the top end of the steel pipe 10, and a template 60 is attached to the top surface of the end plate 50. The template 60 is, for example, a flat plate member, and may be made of steel or rubber. The template 60 has mounting holes 62 through which the pile joint material 32 can be inserted. The arrangement of the mounting holes 62 is designed to correspond to the hole 52 formed in the end plate 50. The thickness of the template 60 can be designed as desired, and it is preferable to design it to be thicker than the height of the protruding portion 32a, for example, so that the protruding portion 32a of the pile joint material 32 does not protrude from the surface of the template 60 when the template 60 is attached.

In addition, a displacement prevention material 70 may be provided in the concrete portion 20, for example, in the longitudinal center portion inside the steel pipe 10. FIG. 4 is a schematic plan view of the displacement prevention material 70. As shown in FIG. 4, the displacement prevention material 70 has a plurality of notches 73 formed along the outer periphery for inserting the pile reinforcing bar 30 into the annular steel flat plate 71 and is provided so as to surround the steel flat plate 71 over the entire periphery to close the notches 73. In addition, the band-shaped plate 75 has a spacing retaining material 77 attached at a predetermined position (four positions around the periphery in FIG. 4) that appropriately maintains the spacing between the reinforcing bars and the spacing between the reinforcing bars and the inner circumference of the steel pipe when the pile reinforcing bar 30 is attached. A number of reinforcing bars 30 are fitted into the cutouts 73, and in this state, a strip plate 75 is placed to cover the cutouts 73, and the reinforcing bars 30 are fixed in place, so that the displacement prevention material 70 and the reinforcing bars 30 are integrated together so that each reinforcing bar 30 is in a suitable position.

<Pile head structure construction method>
Next, a method from manufacturing the pile structure 2 to constructing the pile head structure 1 according to an embodiment of the present invention will be described. Figures 5 to 8 are schematic explanatory diagrams of the manufacturing method of the pile structure 2, and Figure 9 is a schematic explanatory diagram of the constructing method of the pile head structure 1. Note that in Figures 5 to 9, the same reference numerals are used to denote the respective components described above with reference to Figures 1 to 4, and their explanations may be omitted.

First, as shown in FIG. 5, multiple pile reinforcing bars 30, each with a pile joint material 32 attached to its tip and integrated with a displacement prevention material 70, are inserted into the opening (one end that becomes the top end) of the steel pipe 10. After insertion, the ends of the pile joint material 32 attached to the tips of the pile reinforcing bars 30 are protruded so as to be positioned above the top end of the steel pipe 10.

Next, as shown in FIG. 6, an end plate 50 is provided on the top end of the steel pipe 10 with the pile joint material 32 protruding from the top end of the steel pipe 10. At this time, the pile joint material 32 is inserted into a hole 52 formed in the end plate 50, and is positioned so that the protruding portion 32a protrudes upward from the end plate 50. At this time, adhesive may be applied between the inner circumference of the hole 52 of the end plate 50 and the pile joint material 32 to fix the pile joint material 32. The end plate 50 may also be fixed to the end of the steel pipe 10 by a fixing means such as full circumference welding.

Note that, here, the procedure for providing the end plate 50 after inserting the pile reinforcing bar 30 with the pile joint material 32 attached into the steel pipe 10 is described, but the procedure is not limited to this. For example, it is also possible to fix the end plate 50 to the steel pipe 10 in advance, insert the pile reinforcing bar 30 with the pile joint material 32 attached from the lower end (other end) of the steel pipe 10, and fix the protruding portion 32a of the pile joint material 32 by protruding it from the hole portion 52 of the end plate 50.

Next, as shown in FIG. 7, a template 60 is provided on the upper surface of the end plate 50 so that the protrusion 32a is inserted into the mounting hole 62. The template 60 is then fixed to the end plate 50. The protrusion 32a is set in a state where it does not protrude upward from the mounting hole 62. The fixing means at this time may be, for example, welding or a locking bolt.

Then, as shown in FIG. 8, concrete U is poured inside the steel pipe 10. The concrete U is poured, for example, by centrifugal molding so as to be integrated with the inner peripheral surface of the steel pipe 10. After the concrete U hardens and the concrete portion 20 is formed, the template 60 is removed to complete the pile structure 2.

Next, as shown in FIG. 9, the completed pile structure 2 is erected and inserted as a precast concrete pile into the desired ground (not shown), and the pile head reinforcing bar 40, to which the pile outer joint material 42 has already been attached, is connected using a relay bolt 55 to the protruding portion 32a of the pile inner joint material 32 protruding from the pile head. Then, torque is introduced to each joint material (pile inner joint material 32, pile outer joint material 42) to crimp the pile inner reinforcing bar 30 and the pile head reinforcing bar 40 together. In this way, the construction of the pile head structure 1 according to the embodiment of the present invention is completed.

(Action and Effect)
According to the pile head structure 1 of this embodiment, when the pile structure 2 is used as a precast concrete pile, it can be manufactured in a state in which the protruding portion 32a of the joint material 32 in the pile protrudes from the hole 52 in the end plate 50. In the pile structure 2, since the protruding portion 32a of the joint material 32 in the pile is provided, the pile interior reinforcing bar 30 and the pile head reinforcing bar 40 can be effectively crimped together. That is, the opposing surfaces of the joint material 32 in the pile and the joint material 42 in the pile exterior can be reliably abutted against each other, and torque can be effectively introduced, so that the reinforcing bar performance of both the pile interior reinforcing bar 30 and the pile head reinforcing bar 40 can be fully exhibited.

In addition, in the pile head structure 1 according to this embodiment, a displacement prevention material 70 is provided inside the steel pipe 10, for example in the concrete portion 20 at the center of the longitudinal direction, during the manufacture of the pile structure 2. This ensures that the spacing between the multiple reinforcing bars 30 installed inside the pile and the spacing between the reinforcing bars 30 inside the pile and the inner circumference of the steel pipe 10 are adequate, allowing the desired reinforcement configuration to be achieved.

In particular, when manufacturing the pile structure 2, the provision of the protruding portion 32a of the joint material 32 inside the pile can prevent interference with the manufacturing machine during the manufacturing of the pile structure 2 (prefabricated concrete pile) and damage to the protruding portion 32a during concrete pouring, which can occur when the pile structure 2 is manufactured by using a manufacturing method that uses the template 60.

Although one embodiment of the present invention has been described above, the present invention is not limited to the illustrated embodiment. It is clear that a person skilled in the art can come up with various modified or revised examples within the scope of the ideas described in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

<Modifications Related to Templates>
In the above embodiment, when manufacturing the pile structure 2, the protruding portion 32a of the joint material 32 in the pile is inserted into the mounting hole 62 of the template 60, thereby suppressing interference of the protruding portion 32a with a manufacturing machine during manufacturing of the pile structure 2 and damage to the protruding portion 32a during concrete pouring. The configuration of the template 60 is not limited to that described in the above embodiment. Therefore, other forms of the template 60 will be described below with reference to the drawings as the first modified example, the second modified example, and the second modified example of the present invention. In the following description, components having the same functional configuration as those in the above embodiment are illustrated with the same reference numerals, and their description may be omitted.

<First Modification>
10 is a schematic explanatory diagram of a template 60a according to a first modified example of the present invention, where (a) is a plan view, (b) is a vertical cross-sectional view, and (c) is an enlarged explanatory view. As shown in Fig. 10, the template 60a according to this modified example has a counterbore 80 having a diameter larger than the diameter of the mounting hole 62 formed around the mounting hole 62. The design of the diameter and depth of the counterbore 80 is arbitrary, and it is designed so that, for example, a bolt 81 of a predetermined dimension can be screwed in.

According to the configuration of this modified example, by screwing the bolt 81 into the upper end of the joint material 32 inside the pile, it is possible to prevent the intrusion of foreign matter during concrete pouring. In addition, when the template 60a is a rubber plate, by tightening the bolt into the countersunk portion 80, the template 60a can be fixed in close contact with the steel pipe 10 without using welding or other methods, thereby preventing concrete leakage.

<Modification 2-1>
11A and 11B are schematic diagrams of a template 60b according to a second modified example of the present invention, in which (a) is a plan view and (b) is a longitudinal sectional view. As shown in FIG. 11, the template 60b according to this modified example is a so-called notched template in which a notch 85 is formed around the mounting hole 62.

It is known that during the manufacture of the pile structure 2, the joint material 32 inside the pile may be manufactured in a state where it is shifted inward. With the configuration of this modified example, the construction error of the pile head structure 1 caused by such manufacturing errors can be absorbed by forming a notch 85 around the mounting hole 62, making it possible to realize efficient construction.

<Modification 2-2>
12 is a schematic diagram of a template 60c according to the second modified example of the present invention, where (a) is a plan view, (b) is a vertical cross-sectional view, and (c) is an enlarged explanatory view. As shown in FIG. 12, the template 60c according to this modified example has a notched counterbore 87 formed around the mounting hole 62. That is, the notched portion 85 of the second modified example is provided with a predetermined depth and also has a counterbore shape. The depth of the notched counterbore 87 is arbitrary, and is designed so that, for example, a bolt 88 of a predetermined dimension can be screwed in.

In addition to the same effects as those of the above-mentioned variant 2-1, the configuration of this variant can prevent the intrusion of foreign matter during concrete pouring by forming a notched countersunk portion 87 and screwing a bolt 88 into the upper end of the joint material 32 inside the pile.

<Modifications Related to Protective Member>
In addition, in the construction method of the pile head structure 1 described in the above embodiment, when the pile structure 2 is erected and inserted into the ground as a precast concrete pile, a protective member 100 may be used to protect the protruding portion 32a of the joint material 32 protruding from the end plate 50. Therefore, the following will describe configurations using the protective member 100 (hereinafter, referred to as 100a or 100b) as the third and fourth modified examples of the present invention with reference to the drawings. In the following description, components having the same functional configuration as those in the above embodiment and modified examples are illustrated with the same reference numerals, and their description may be omitted.

<Third Modification>
13 is a schematic diagram of a protective member 100a in a third modified example of the present invention, where (a) is a plan view, (b) is a vertical cross-sectional view, and (c) is an enlarged explanatory view. As shown in FIG. 13, the protective member 100a has a so-called split type configuration in which a plurality of divided protective member parts are arranged above the joint material 32 in the pile on the same circumference. Each part of the protective member 100a is formed with a counterbore 91, which is designed so that, for example, a bolt 93 of a predetermined dimension can be screwed in.

According to this modified example, when the manufactured pile structure 2 is inserted into the ground as a precast concrete pile, the precast concrete pile can be inserted while the protruding portion 32a protruding upward from the end plate 50 is protected by the protective member 100a. By protecting the protruding portion 32a, the pile interior reinforcing bar 30 and the pile head reinforcing bar 40 can be effectively crimped together, and a pile head structure 1 is realized in which the performance of both the pile head reinforcing bar 40 and the pile interior reinforcing bar 30 is fully demonstrated.

<Fourth Modification>
FIG. 14 is a schematic diagram of a protective member 100b in a fourth modified example of the present invention, where (a) is a plan view and (b) is a vertical cross-sectional view. As shown in FIG. 14, the protective member 100b is a concrete member having a through hole 95 that penetrates vertically. The protective member 100b is made of concrete, and has a certain thickness from the viewpoint that reinforcing bars must be arranged inside or a certain amount of concrete must be filled in order to ensure its strength. In this modified example, the protective member 100b may be fixed to the end plate 50 by, for example, screwing a bolt 97 into the upper end of the joint material 32 in the pile through the through hole 95. The shape of the through hole 95 is arbitrary, and for example, as shown in the figure, a configuration in which a bolt 97 screwed in at two points in the circumferential direction is held by one through hole 95 may be used.

According to this modification, as in the third modification, when the manufactured pile structure 2 is inserted into the ground as a precast concrete pile, the precast concrete pile can be inserted while the protruding portion 32a protruding upward from the end plate 50 is protected by the protective member 100b. By protecting the protruding portion 32a, the pile interior reinforcing bar 30 and the pile head reinforcing bar 40 can be effectively crimped together, and a pile head structure 1 is realized in which the performance of both the pile head reinforcing bar 40 and the pile interior reinforcing bar 30 is fully demonstrated.

The present invention can be applied to the pile head structure of a precast concrete pile and its construction method.

LIST OF SYMBOLS 1...Pile head structure 2...Pile structure 10...Steel pipe 20...Concrete section 30...Inside pile reinforcing bar 32...Inside pile joint material 32a...Protruding section 40...Pile head reinforcing bar 42...Outside pile joint material 50...End plate 52...Hole section 55...Relay bolt 60...Template 60a to 60c...Template (pertaining to modified example) 62...Mounting hole 70...Position prevention material 71...Steel flat plate 73...Notch section 75...Strip plate 77...Spacing retaining material 80, 91...Counterbore section 81, 88, 93, 97...Bolt 85...Notch section 87...Notch counterbore section 95...Through hole 100 (100a, 100b)...Protective member U...Concrete

Claims (1)

A construction method for a pile head structure of a precast concrete pile, comprising:
A plurality of reinforcing bars having joint members at their ends are inserted into the steel pipe,
The pile reinforcing steel bar is fixed in a state in which the tip of the pile joint material protrudes as a protrusion of a predetermined length from a hole provided in an end plate fixed to the top end of the steel pipe,
a template having mounting holes formed therein is provided on an upper surface of the end plate such that the protrusions are inserted into the mounting holes, and the template is fixed to the end plate;
pouring concrete into the steel pipe, and removing the template after the concrete has hardened;
A construction method for a pile head structure, characterized in that a pile head reinforcing bar having an outer pile joint material at its end is connected to the protrusion, and the inner pile joint material and the outer pile joint material are crimped together.

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