JP2004300754A - Pile head joint structure - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a pile heat joint structure, having high base isolation performance, simple in structure and easily constructed. <P>SOLUTION: A hollow pipe 2 and an inner pipe 3 having a smaller diameter than the hollow pipe 2 are concentrically installed on the pile head part of a foundation pile 1. A foundation slab 4 is formed on the hollow pipe 2 and the inner pipe 3. A sliding member 5 is interposed between the hollow pipe 2 and the inner pipe 3 and the foundation slab 4. Two or more bar-like anchors 7 are installed in a hollow part 6 formed between the hollow pipe 2 and the inner pipe 3, and the lower end part 7a and the upper end part 7b are fixed to the pile head part of the foundation pile 1 and the foundation slab 4, respectively. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to a pile head joint structure having a seismic isolation function, and is mainly used for a pile head joint structure between a foundation pile made of ready-made piles such as PC piles and a foundation slab.
[0002]
[Prior art]
In the case of a pile foundation, the foundation pile and the foundation slab are generally constructed in a rigidly connected state. Conventionally, as a pile head connection structure between a foundation pile and a foundation slab using an existing pile such as a PC pile, a long rod-shaped stud or anchor reinforcing bar is welded or bolted to a connection end plate attached to the pile head of the foundation pile. 2. Description of the Related Art A pile head joint structure is known in which a plurality of plants are vertically laid at substantially equal intervals by connection or the like, and concrete is cast thereon to form a foundation slab in a rigid joint state with a pile head.
[0003]
In addition, a flange having a diameter larger than the pile diameter and having a plurality of small holes in the periphery is integrally attached to the joining end plate attached to the pile head by welding or the like, and a reinforcing bar for joining with the foundation slab is attached to this flange. There is also known a pile head joint structure in which a plurality of flanges having the same shape are joined by bolts using small holes (Patent Document 1).
[0004]
However, all of these pile head joint structures have a very high degree of fixation between the pile head and the foundation slab, so that the pile head, especially the joint between the joint end plate and the anchor rebar or stud, is severely damaged during a huge earthquake. In some cases, unexpected shearing and bending moments caused the piles to break and eventually the superstructure to collapse.
[0005]
For this reason, recently, various pile head joint structures having a seismic isolation function at the pile head have been developed, and for example, FIG. 5 shows an example thereof (Patent Document 2).
[0006]
In the figure, a pile head cap 21 having a bottomed pipe 20 is put on a pile head of a foundation pile 22 to form a hollow space 23 inside the bottomed pipe 20 at the pile head. Further, a plurality of reinforcing bars 24 are vertically arranged in the hollow space 23, and the lower end 24a is fixed to the bottom of the hollow space 23, that is, the bottom plate 20a of the bottomed tube 20 by the fixing nut 25, and the upper end 24b is It is fixed to a base plate 26 which is a base part of the upper structure.
[0007]
In such a configuration, the reinforcing bars 24 can be freely deformed in the hollow space 23 without any constraint, thereby absorbing the relative displacement between the pile head and the upper structure during a huge earthquake, As a result, an excessive shearing force or bending moment does not act on the pile head, so that it is possible to prevent the pile head from being broken and, consequently, the upper structure from collapsing.
[0008]
Also, as another pile head joint structure, a plurality of anchor rebars are planted by welding or bolt connection on the joint end plate of the pile head, and damper materials are installed around these anchor rebars, and the foundation slab is installed. A pile head joint structure embedded and installed in the inside is known (Patent Document 3).
[0009]
In addition, by reducing the diameter of the foundation pile so that the edge stress due to the bending of the pile is less than the allowable stress of the material that forms the foundation pile, the foundation pile itself will be able to react to the lateral flow of the ground due to earthquake etc. There is also known a configuration in which it is displaced by following (Patent Document 4).
[0010]
Furthermore, even though concrete piles such as PHC are used for the lower pile to increase the strength of the pile on the pile head side against the horizontal force acting on the pile head during an earthquake, the steel pipe is used for the upper pile. It connects piles or SC piles (Patent Document 5).
[0011]
[Patent Document]
[Patent Document 1]
Japanese Patent Application 2000-312922
[Patent Document 2]
JP 2000-248560
[Patent Document 3]
JP-A-2000-336665
[Patent Document 4]
JP-A-1998-219678
[Patent Document 5]
JP-A-7-48833
[0012]
[Problems to be solved by the invention]
However, in the case of the pile head joint structure described in Patent Document 2 as shown in FIG. 5, it is necessary to secure a hollow portion for installing a device including the pile head cap 21 and the like, particularly at the pile head. In addition, since the device is complicated, there are problems that not only the structure tends to be complicated but also the cost is significantly increased.
[0013]
Further, in the pile head joint structure described in Patent Document 3, the purpose is to reduce the degree of fixation of the pile head, but the seismic isolation effect of the damper material alone cannot avoid the destruction of the pile head during a huge earthquake. There was a problem.
[0014]
And, in the pile head joint structure described in Patent Document 5, even if the horizontal strength of the foundation pile increases, the strength of the joint (pile head joint) between the foundation pile and the foundation slab is weak, and the There was a risk of breakage at the location.
[0015]
The present invention has been made to solve the above problems, and an object of the present invention is to provide a pile head joint structure having a very high seismic isolation performance, a simple structure, and easy construction.
[0016]
[Means for Solving the Problems]
In the pile head joint structure according to claim 1, a hollow pipe is installed at a pile head of a foundation pile, a plurality of rod-like anchors are installed in the hollow pipe, and a lower end thereof is attached to a pile head of the foundation pile. The upper end is fixed to a base slab formed at the upper end of the hollow tube.
[0017]
The invention of the present application is capable of absorbing the relative displacement between the pile head and the upper structure during a huge earthquake by allowing the rod-shaped anchor to be freely deformed in the hollow tube without any constraint. As a result, an excessive shearing force or bending moment is not generated at the pile head, so that it is possible to prevent the pile head from breaking, and eventually the upper structure from collapsing.
[0018]
In this case, a steel pipe can be used as the hollow pipe, and as the rod-shaped anchor, a normal rebar, a deformed rebar, a steel bar, a PC steel, a PC steel bar, a bolt, a low yield point steel material, or the like can be used. In addition, by appropriately changing the diameter, the number, the length, and the like of the rod-shaped anchors, the degree of fixation of the pile head joint can be freely set according to design conditions.
[0019]
A pile head joint structure according to a second aspect is the pile head joint structure according to the first aspect, wherein a sliding member is interposed between the hollow tube and the foundation slab.
[0020]
The present invention particularly enables the relative displacement between the pile head and the upper structure to be smoothly performed by sliding (horizontal displacement) the sliding member on the lower surface of the foundation slab in a direction opposite to the foundation slab. It is.
[0021]
It is desirable to attach a sliding plate to the lower surface of the base slab so as to correspond to the sliding member. Further, the sliding member and the sliding plate in this case can be easily formed from, for example, a steel plate subjected to Teflon (registered trademark) processing.
[0022]
The pile head joint structure according to claim 3 is the same as the pile head joint structure according to claim 1 or 2, wherein an inner pipe is installed in the hollow pipe, and a rod-shaped anchor is installed between the hollow pipe and the inner pipe. It is characterized by becoming.
[0023]
The present invention is applied to a case where a foundation pile is constructed by an embedding method such as a pre-boring method, and a hollow portion (a hollow tube and an inner tube) for installing a rod-like anchor by installing an inner tube in a hollow tube. With this arrangement, it is possible to prevent the cement milk filled in the borehole from overflowing into the hollow tube and solidifying to restrain the rod-shaped anchor.
[0024]
In this case, since the inner tube does not require any particular strength, a tubular body made of a synthetic resin, hard paper, or the like can be used in addition to a steel tube.
[0025]
A pile head joint structure according to a fourth aspect is the pile head joint structure according to the first or second aspect, wherein the hollow pipe is filled with a space forming material. In this case, as the space forming material, for example, a foaming material, a viscous material, rubber, lead, or a low-strength solidifying material (such as mortar or cement milk) can be used.
[0026]
The invention of the present application fills an excavation hole by filling a space forming material such as a foam material or a viscous material instead of installing an inner pipe in a hollow pipe when constructing a foundation pile by an embedding method such as a pre-boring method. It is possible to prevent the poured cement milk from overflowing into the hollow tube and solidifying to restrain the rod-shaped anchor.
[0027]
According to a fifth aspect of the present invention, there is provided a pile head joint structure according to any one of the first to fourth aspects, wherein a steel pipe is provided as a hollow pipe.
[0028]
The pile head joint structure according to claim 6 is characterized in that, in the pile head joint structure according to any one of claims 1 to 5, a precast concrete pile or a steel pipe pile is installed as a foundation pile. .
[0029]
BEST MODE FOR CARRYING OUT THE INVENTION
1 to 3 show an example of a pile head joint structure according to the present invention. In the figures, a hollow pipe 2 and an inner pipe 3 smaller in diameter than the hollow pipe 2 are formed concentrically on a pile head of a foundation pile 1. And a base slab 4 is formed at the upper end of the hollow tube 2 and the inner tube 3.
[0030]
Further, a sliding member 5 is interposed between the hollow tube 2 and the inner tube 3 and the base slab 4, and a plurality of rod-shaped anchors are provided in a hollow portion 6 formed between the hollow tube 2 and the inner tube 3. 7 are installed.
[0031]
As the foundation pile 1, a hollow RC pile formed by centrifugal molding or a PC pile into which prestress is introduced is used, and a joining end plate 1a is attached to an upper end portion. The joining end plate 1a is used not only as a joining plate for connecting the foundation piles 1 but also for introducing a prestress in the axial direction of the foundation pile 1 such as a PC bar inserted into the concrete of the pile. The fixing plate also serves as a fixing plate for fixing the end portion of the tendon. Therefore, the joining end plate 1a is usually provided with several screw holes and loose holes for fixing the end of the tendon. I have. In this case, as the foundation pile 1, a pile having a larger area of the joining end plate 1 a (difference between the outer diameter and the inner diameter of the hollow pile) such as a head pile is more easily used.
[0032]
The hollow pipe 2 is formed of a steel pipe having an outer diameter substantially equal to the outer diameter of the foundation pile 1 and having a supporting strength equal to or higher than that of the foundation pile 1. The hollow tube 2 is integrally welded to the upper end of the joining end plate 1a. By using a steel pipe as the hollow pipe, the material strength of the pile head can be increased, and the stress applied to the pile head can be reduced.
[0033]
The inner pipe 3 has substantially the same inner diameter as the inner diameter of the hollow portion 1a of the foundation pile 1 and has substantially the same height as the hollow pipe 2, and is formed of a tubular body made of, for example, a steel pipe or a synthetic resin or hard paper. Have been. The inner pipe 3 has an inner diameter substantially equal to the inner diameter of the hollow portion 1 a of the foundation pile 1 and is formed to have substantially the same height as the hollow pipe 2.
[0034]
If it is possible to install a tube having the same supporting strength as the hollow tube 2 as the inner tube 3, the inner tube 3 is formed from a steel tube to be a hollow tube, and the hollow tube 2 is provided outside the hollow tube. Instead, a synthetic resin tube or a hard paper tube may be provided. Further, instead of installing the inner tube 3, the hollow tube 2 may be filled with a foaming material, a viscous material, or a low-strength solidified material. Further, the hollow portion 6 may be left hollow.
[0035]
In this case, when the foundation pile 1 is constructed by the embedding method such as the pre-boring method, the inner pipe 3 is filled with the cement milk or soil cement in the excavation hole through the hollow portion 1b of the foundation pile 1 and the upper end of the pile. To prevent the inside of the hollow portion 6 from being filled with cement milk or soil cement, so that the inner tube 3 has the same strength as the hollow tube 2. Since it is not required, it may be formed of a synthetic resin pipe or a tubular body made of hard paper, in addition to a steel pipe. Further, when the strength of the rod-shaped anchor 7 is larger than that of cement milk or soil cement, the inner pipe is particularly required. The interior of the hollow portion 6 may be filled with cement milk or soil cement without providing the 3.
[0036]
The sliding member 5 slides (horizontal displacement) the lower surface of the sliding plate 4a attached to the lower surface of the foundation slab 4 in a direction opposite to the sliding plate 4a and the foundation slab 4, thereby forming the pile head of the foundation pile 1 and the foundation slab. 4 is provided in order to allow relative horizontal displacement to be performed smoothly.
[0037]
The sliding member 5 is formed in a circular cap shape so as to cover the upper end of the hollow tube 2, and a through hole 5 a through which the rod-shaped anchor 7 penetrates is provided at a predetermined interval in the circumferential direction slightly inside the peripheral edge. In particular, the through-hole 5a is a so-called dumb hole so that the rod-shaped anchor 7 can be freely deformed.
[0038]
The sliding member 5 and the sliding plate 4a are formed from a steel plate subjected to Teflon (registered trademark) processing. Excessive sliding (horizontal displacement) between the sliding member 5 and the sliding plate 4a and the foundation slab 4 is prevented by the peripheral edge of the sliding member 5 hitting a stopper 4b protruding from the peripheral edge of the sliding plate 4a. You.
[0039]
The rod-shaped anchor 7 penetrates the through hole 5a of the sliding member 5 and the through hole 4c formed in the sliding plate 4a, and is provided in the hollow portion 6 at predetermined intervals in the circumferential direction of the hollow tube 2 and the inner tube 3. is set up.
[0040]
Further, the lower end 7a and the upper end 7b of each rod-shaped anchor 7 are fixed to the pile head of the foundation pile 1 and the foundation slab 4, respectively. In particular, the lower end 7a is stud welded, bolted or coupled to the joining end plate 1a. Has been established by such.
[0041]
When fixing the lower end 7a of the rod-shaped anchor 7 to the joining end plate 1a, a screw hole or a loose hole formed in the joining end plate 1a can be used. Further, the rod-shaped anchor 7 can be attached when the hollow pipe 2 is attached to the pile head of the foundation pile 1 at the time of manufacturing the foundation pile 1 before or during construction.
[0042]
Further, the rod-shaped anchor 7 may be attached to the head of the foundation pile 1 together with the hollow tube 2 at the time of manufacturing the foundation pile 1, but is extended above the hollow tube 2, and In order to obstruct the construction of the foundation pile 1, it is preferable to adopt a structure that can be stored in the hollow pipe 2 until the construction of the foundation pile 1 is completed. As a method therefor, for example, there is a method in which the rod-shaped anchor 7 has a structure that can freely expand and contract, or a structure in which the rod-shaped anchor 7 can be connected and added later.
[0043]
When the foundation pile 1 is constructed, a cap (not shown) is placed on the upper end of the hollow tube 2 so that soil and the like do not enter the hollow section 6 during construction of the pile. It is possible to prevent soil cement, earth and sand, etc. in the excavation hole from entering from inside from above.
[0044]
It is desirable to use a steel material having a high toughness for the rod-shaped anchor 7, for example, a normal reinforcing bar, a deformed reinforcing bar, a steel bar, a PC steel, a PC steel bar, a bolt, a low yield point steel material, or the like can be used.
[0045]
4 (a), 4 (b) and 4 (c) show modifications of the present invention. In FIG. 4 (a), a flange 2a horizontally projecting inward from the lower end of the hollow tube 2 is provided. The lower end 7a of each rod-shaped anchor 7 is fixed on the horizontal flange 2a by welding.
[0046]
4 (b) and 4 (c), the lower end 7a of each rod-like anchor 7 is slightly bent outward and fixed inside the hollow tube 2 by welding. In particular, in FIG. 4 (c), The lower end 7a of each rod-like anchor 7 is fixed to the inside of a substantially middle portion of the hollow tube 2.
[0047]
【The invention's effect】
The invention of the present application has been described above. In particular, since the rod-shaped anchor installed in the hollow pipe of the foundation pile head can be freely deformed without any constraint in the hollow pipe, the pile head at the time of a huge earthquake Can absorb the relative displacement between the pile head and the superstructure, which does not generate excessive shearing force or bending moment at the pile head, thus preventing the pile head from breaking and eventually the superstructure from collapsing. There are effects such as prevention.
[0048]
Further, the steel pipe can be extremely easily and inexpensively constructed using a steel pipe as the hollow pipe and a normal reinforcing bar as the rod-shaped anchor. Furthermore, the fixing degree of the pile head joint can be freely set according to the design conditions by appropriately changing the diameter, the number, the length, or the like of the rod-shaped anchors.
[Brief description of the drawings]
1 shows an example of a pile head joint structure between a foundation pile and a foundation slab, (a) is a partial perspective view, and (b) is a partially exploded perspective view.
FIG. 2 shows an example of a pile head joint structure between a foundation pile and a foundation slab, (a) is a partial plan view, and (b) is a longitudinal sectional view thereof.
FIG. 3 is a partial perspective view showing a modified example of a pile head joint structure between a foundation pile and a foundation slab.
FIG. 4 shows an example of a pile head joint structure between a foundation pile and a foundation slab, and (a), (b) and (c) are partial longitudinal sectional views thereof.
FIG. 5 is a longitudinal sectional view showing a conventional example of a pile head joint structure between a foundation pile and a foundation slab.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Foundation pile 2 Hollow tube 3 Inner tube 4 Foundation slab 5 Sliding member 6 Hollow part 7 Rod anchor

Claims (6)

A hollow pipe is installed at the pile head of the foundation pile, a plurality of rod-shaped anchors are installed within the hollow pipe, the lower end thereof is at the pile head of the foundation pile, and the upper end is the upper end of the hollow pipe. A pile head joint structure characterized by being fixed to a foundation slab formed in a slab. The pile head joint structure according to claim 1, wherein a sliding member is interposed between the hollow tube and the foundation slab. The pile head joint structure according to claim 1 or 2, wherein an inner pipe is installed in the hollow pipe, and a plurality of rod-shaped anchors are installed between the hollow pipe and the inner pipe. The pile head joint structure according to claim 1 or 2, wherein the hollow tube is filled with a space forming material. The pile head joint structure according to any one of claims 1 to 4, wherein a steel pipe is installed as the hollow pipe. The pile head joint structure according to any one of claims 1 to 4, wherein a concrete ready-made pile or a steel pipe pile is installed as the foundation pile.

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