JP2006083609A - Joint structure of pile head section and its construction method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a joint structure of a pile head section, which enhances constructibility and quality and which enables the shortening of a construction period and a reduction in cost, and a construction method for the pile head. <P>SOLUTION: This joint structure of the pile head section is intended for a pile 1, the outer peripheral section of which is composed of a steel pipe, such as a steel pipe pile, an SC pile (prefabricated concrete pile covered with the steel pipe), and a concrete-filled steel pipe pile. A plurality of vertical ribs 3 etc. are radially welded to an outer peripheral surface of the pile head section 2 at each angle of 45° from the center of the cross section of the pile 1. Leading ends of the adjacent vertical ribs 3 and 3 are welded to a steel plate 4a, so as to form an outer steel pipe 4 in an octagonal shape in plan view. A plurality of anchor bars 6 etc., which are to be embedded in a foundation, are welded to an upper outer peripheral surface of the outer steel pipe 4 at predetermined intervals. A filler 7, which is composed of concrete, soil mortar, mortar, etc., is infilled into a gap between the outer steel pipe 4 and the pile head section 2. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

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

Conventionally, as a joint structure of a pile head when joining a concrete-filled steel pipe pile or a steel pipe pile and a foundation beam, for example, an inner anchor method in which one end of an anchor bar is inserted and fixed inside the pile head, There is a whisker muscle method in which one end of an anchor bar is welded to the outer peripheral surface of the pile head. Alternatively, a coupler method (see Patent Document 1) for fixing screw reinforcing bars to a coupler mounted on the outer peripheral surface of the pile head, or an outer steel pipe that is slightly larger than the pile head is wound around the pile head and There has been proposed a double steel pipe system (see Patent Documents 2 and 3) in which concrete is filled between the outer steel pipe and one end of an anchor bar is embedded in the concrete.
Japanese Patent Publication No. 3-54736 (Page 1-2, Fig. 5) Japanese Patent Laid-Open No. 11-13139 (page 3-4, FIG. 1) JP 2000-297472 A (page 2-3, FIG. 1)

However, the conventional pile head joint structure has the following problems.
In the inner saddle method, when a large bending moment is generated at the pile head, the anchor bars become overcrowded and there is a problem that the workability is inferior. In addition, since the anchor bars are arranged inside the pile head, the cross-section efficiency of the anchor bars is poor with respect to bending, and it is often impossible to cope with the pile head stress generated when the pile head is fixed.
In addition, in the beard muscle method, anchor bars are welded to the outer peripheral surface of the pile head, so the cross-sectional efficiency is higher compared to the inner collar method, but there are not only problems with workability and welding quality on site. When the pile head bending stress increases, the necessary number of anchor bars cannot be arranged, and the pile head stress at the time of fixing the pile head may not be processed.
Further, in the coupler method, on-site welding is not required and anchor bars can be easily attached, so that both workability and quality are improved. However, since the coupler is expensive, the construction cost is likely to increase. Moreover, when pile head bending stress becomes large, a required number of anchor bars cannot be arranged, and pile head stress at the time of pile head fixation may not be processed.
Furthermore, in the double steel pipe method, the distance from the neutral axis of the pile body to the anchor bar is not significantly increased compared to the inner rod method, the whiskers method, or the coupler method. Not much reduced. In addition, since anchor bars are anchored to the concrete between the pile head and the outer steel pipe, there is a problem that the length of the outer steel pipe becomes long in order to secure the anchoring length, which tends to increase costs.

  The present invention has been made in view of the above-described problems, and has an object to provide a pile head joint structure that improves workability and quality, shortens the work period, and reduces the cost, and its construction method. To do.

In order to achieve the above object, a pile head joint structure according to the present invention is a pile head joint for joining a steel pipe pile or a pile around which a steel pipe is wound to a foundation (footing or foundation beam) of a structure. The structure has a plurality of anchor bars embedded in the foundation at the outer peripheral portion, and is arranged radially on the outer peripheral surface of the pile head and a polygonal outer steel pipe surrounding the pile head. And a plurality of vertical ribs provided between the pile head and the outer steel pipe, and a gap between the pile head and the outer steel pipe is filled with a filler.
In this invention, the bending of a pile can be smoothly transmitted to an outer steel pipe via a vertical rib by providing the some vertical rib which connects a pile head and an outer steel pipe. As a result, the pile head and the outer steel pipe can be integrated without expecting the effect of the filler filled in the gap between the pile head and the outer steel pipe. On the other hand, since the functions required of the filler are only rust prevention and buckling prevention of the steel material, it is not necessary to pay special attention to the filling property and quality control of the filler.

  In the pile head joint structure according to the present invention, a diaphragm may be provided on the upper end surface and / or the lower end surface of the gap so as to close the gap between the pile head and the outer steel pipe.

Moreover, the construction method of the pile head joint part which concerns on this invention is a construction method of the pile head which has said joining structure, Comprising: The several vertical rib is arrange | positioned radially on the outer peripheral surface of the said pile head. A first step, a second step of laying a steel plate between the adjacent vertical ribs to form a polygonal outer steel pipe surrounding the pile head, and the pile head and the outer steel pipe. A third step of filling the gap with a filler and a fourth step of disposing anchor bars on the outer peripheral portion of the outer steel pipe are characterized.
In the present invention, since the outer steel pipe is attached to the pile head in advance in a factory or the like prior to the pile placement, stable quality can be realized at low cost. Moreover, since no special skills or tools are required, the construction time can be shortened.

Further, in the construction method of the pile head joint according to the present invention, the gap head is closed between the second step and the third step so as to close the gap between the pile head and the outer steel pipe. You may install a diaphragm in an end surface and / or a lower end surface.
In the present invention, before the filler is filled in the gap between the pile head and the outer steel pipe, a diaphragm for closing the gap is installed, so that it is not necessary to separately treat the filler so that it does not flow out of the gap. Filling of the material becomes easy.

ADVANTAGE OF THE INVENTION According to this invention, the bending of a pile can be smoothly transmitted to an outer steel pipe via a vertical rib by providing the several vertical rib which connects a pile head and an outer steel pipe. Therefore, the functions required of the filler are only rust prevention and buckling prevention of the steel material, and it is not necessary to pay special attention to the filling property and quality control of the filler.
Further, according to the present invention, since the outer steel pipe is attached to the pile head in advance at a factory or the like prior to the driving of the pile, stable quality can be realized at low cost. Moreover, since no special skills or tools are required, the construction time can be shortened.

DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments 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 perspective view showing a first embodiment of a pile head joint structure according to the present invention. Moreover, FIG. 2 is the top view and AA arrow sectional drawing.
The joint structure of the pile head according to the present invention is for a pile 1 whose outer peripheral portion is made of a steel pipe, such as a steel pipe pile, an SC pile (a prefabricated concrete pile covered with a steel pipe), and a concrete-filled steel pipe pile. A plurality of vertical ribs 3 are radially welded to the outer peripheral surface of the pile head 2 every 45 degrees. Moreover, the front-end | tip parts of the adjacent vertical ribs 3 and 3 are welded to the steel plate 4a, and form the outer steel pipe 4 of a planar view octagonal shape. A plurality of anchor bars 6 embedded in a foundation (not shown) are welded to the upper outer peripheral surface of the outer steel pipe 4 at a predetermined interval.
On the other hand, the gap between the outer steel pipe 4 and the pile head 2 is filled with a filler 7 made of concrete, soil mortar, mortar or the like in order to prevent rust and buckling of the steel material.

  The vertical rib 3 is a rectangular steel plate having a width of about 0.25 times the pile diameter D and a length of about 0.5 to 1.0 times (wrap length between the vertical rib 3 and the pile head 2). is there. Similarly, the steel plate 4 a constituting the outer steel pipe 4 is also a rectangular steel plate having the same length as the vertical rib 3.

As the anchor bars 6, in addition to using normal reinforcing bars, anchor strength is increased by using a T head bar having a diameter-expanded portion at the tip or an anchor bar in which a fixing plate is fixed to the tip of the reinforcing bar by welding or the like. The length can be shortened.
Instead of flaring the anchor bar 6 to the outer steel pipe 4, a coupler having a female thread, a cap nut, or the like may be welded to the upper outer peripheral surface of the outer steel pipe 4 in advance at a factory or the like. Thereby, the anchor reinforcement 6 is eliminated when the pile 1 is constructed, and the medium digging method can be easily constructed, and the construction efficiency is improved because there is no anchor reinforcement 6 when the pile head is rolled.

FIG. 3 is a perspective view showing a second embodiment of a pile head joint structure according to the present invention. Moreover, FIG. 4 is the top view and AA arrow sectional drawing.
In this embodiment, in addition to the first embodiment, diaphragms 5 are respectively installed on the upper end surface and the lower end surface of the gap so as to close the gap between the pile head 2 and the outer steel pipe 4. The shear force of the pile head 2 can be smoothly transmitted to the outer steel pipe 4 by the 4 and the diaphragm 5.
Here, every other gap 5 is provided for the gaps partitioned by the vertical ribs 3, but the diaphragms 5 may be installed in all the gaps partitioned by the vertical ribs 3. Further, the diaphragm 5 may be provided only on the lower end surface of the gap.

In the pile head joint structure according to the present embodiment, by providing a plurality of vertical ribs 3 that connect the pile head 2 and the outer steel pipe 4, the bending of the pile 1 is smoothly performed on the outer steel pipe 4 via the vertical rib 3. Can be communicated to. As a result, the pile head 2 and the outer steel pipe 4 can be integrated without expecting the effect of the filler 7 filled in the gap between the pile head 2 and the outer steel pipe 4. On the other hand, since the functions required of the filler 7 are only rust prevention and buckling prevention of the steel material, it is not necessary to pay special attention to the filling property and quality control of the filler 7.
Moreover, in the joint structure of the pile head according to the present embodiment, the anchor bars 6 are arranged on the outer peripheral portion of the outer steel pipe 4, so that the arrangement diameter of the anchor bars 6 is smaller than that of the conventional beard bar method or inner collar method. Furthermore, since the size can be freely adjusted according to the cross-sectional diameter of the outer steel pipe 4, overcrowding can be eliminated. As a result, the bending strength and the pulling strength of the pile head 2 can be easily increased, and the strength of the joint structure of the pile head 2 can be increased without difficulty. As a result, there is no damage to the pile head joint, and a pile head structure that generates a yield site in the pile body can be obtained. In other words, it is an optimum joint structure for a tough-oriented pile, and a rational pile design is possible by adopting a thin pile.
Furthermore, in the pile head joint structure according to the present embodiment, the anchor bar 6 is arranged in an octagonal shape, and interference with the base bar arrangement is less likely to occur than in the conventional circular arrangement. Since the number of 6 can also be reduced, the construction of the foundation is greatly facilitated.
In addition, in the joint structure of the pile head according to the present embodiment, the lap length of the pile head 2 and the outer steel pipe 4 is about 0.5 to 1.0 times the pile diameter D, and is less than half the lap length of the conventional method. As a result, the material and excavated soil volume can be greatly reduced.

[Pile head joint construction method]
Next, the construction method of the pile head joint part concerning this invention is demonstrated.
FIG. 5 shows the construction method of the pile head joint according to the present invention in order.
First, in a factory or the like, a plurality of vertical ribs 3 are radially welded to the outer peripheral surface of the pile head 2 every 45 degrees from the center of the cross section of the pile 1 (see FIG. 5A).
Next, the outer steel pipe 4 having an octagonal shape in plan view that surrounds the pile head 2 is formed by connecting the tips of the adjacent vertical ribs 3 and 3 with a steel plate 4a (see FIG. 5B), Filler 7 is filled in the gap with the pile head 2 (see FIG. 5C).
Then, at the pile driving site, the pile 1 with the outer steel pipe 4 attached to the pile head 2 is driven, excavated until the outer steel pipe 4 is exposed, and the anchor bars 6 are welded to the outer periphery of the outer steel pipe 4 ( (See FIG. 5 (d)).
Thereafter, the periphery R of the outer steel pipe 4 is backfilled, and a foundation (not shown) is constructed on the pile head 2.

  In addition, when installing the diaphragm 5 in the gap | interval of the pile head 2 and the outer steel pipe 4, the diaphragm 5 is installed after formation of the outer steel pipe 4 and before filling of the filler 7, and the filling hole provided in the diaphragm 5 is provided. Filler 7 is filled with filler 7 (not shown).

  In the construction method of the pile head joint portion according to the present embodiment, the outer steel pipe 4 is mounted on the pile head 2 in advance at the factory or the like prior to placing the pile 1, so that stable quality can be realized at low cost. Can do. Moreover, all the reinforcing steel materials to be attached to the pile head 2 are made of only steel plates, and no press work is required, so that the production period can be shortened and the cost can be reduced.

  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 embodiment, the outer steel pipe has an octagonal shape in plan view, but it goes without saying that it may be another polygon such as a quadrangle or a hexagon. In the above embodiment, the pile is placed after filling the gap between the outer steel pipe and the pile head. However, the pile is placed so as not to enter the gap between the outer steel pipe and the pile head. After that, piles may be laid and the gap filled with the foundation concrete during foundation construction. In short, it is only necessary to obtain the desired function in the present invention.

It is a perspective view which shows 1st embodiment of the joining structure of the pile head which concerns on this invention. (A) is a top view and (b) is an AA arrow sectional drawing. It is a perspective view which shows 2nd embodiment of the junction structure of the pile head which concerns on this invention. (A) is a top view and (b) is an AA arrow sectional drawing. 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 3 Vertical rib 4 Outer steel pipe 4a Steel plate 5 Diaphragm 6 Anchor reinforcement 7 Filler

Claims (4)

A pile head joint structure for joining a steel pipe pile or a pile wrapped with a steel pipe to the foundation of a structure,
A plurality of anchor bars embedded in the foundation on the outer periphery, a polygonal outer steel pipe surrounding the pile head, and radially disposed on the outer peripheral surface of the pile head, the pile head A pile head joint comprising: a plurality of vertical ribs erected between a section and the outer steel pipe, and a gap between the pile head and the outer steel pipe is filled with a filler. Construction.   2. The pile head joint structure according to claim 1, wherein a diaphragm is installed on an upper end surface and / or a lower end surface of the gap so as to close the gap between the pile head and the outer steel pipe. . A method for constructing a pile head having the joint structure according to claim 1 or 2,
A first step of radially arranging a plurality of vertical ribs on the outer peripheral surface of the pile head;
A second step of laying a steel plate between the adjacent vertical ribs to form a polygonal outer steel pipe that surrounds the pile head; and
A third step of filling a filler in the gap between the pile head and the outer steel pipe;
And a fourth step of disposing an anchor bar on the outer peripheral portion of the outer steel pipe. Between the second step and the third step,
The construction method of a pile head joint according to claim 3, wherein a diaphragm is installed on the upper end surface and / or the lower end surface of the gap so as to close the gap between the pile head and the outer steel pipe.

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