JPH086336B2 - Pile head support structure - Google Patents

Description

The present invention relates to a pile head support structure having a support function close to a pin state.

[Conventional technology]

Regarding the connection of the pile head, there are an idea that the pile head is rigidly connected and an idea that the pile head is pin-joined.

However, if rigid connection is used, the bending moment that acts on the pile head becomes extremely large, so it is necessary to deal with it by increasing the amount of reinforcement of the pile head, etc. It is also disadvantageous.

On the other hand, if the pile head is pin-jointed, the bending stress acting on the pile main body is reduced, and the pile main body can be economically designed. In addition to the complicated structure, it is difficult to form a complete pin structure, which may cause damage such as damage to the pile head.

Conventionally, such a structure of the pile head has been devised, for example, a pile foundation described in JP-B-63-19651 or a joint between a pile head and basic concrete described in JP-A-63-300120. There is a structure. The former has a structure in which a steel plate is provided on the bottom surface of the footing, and a cushioning layer wrapping sand or gravel with a sheet is further provided between the steel plate and the pile head to separate the footing and the pile head. The latter has a structure in which a cap made of precast concrete is provided on the pile head, and the cap is loosely fitted to the pile head to reduce the bending constraint of the pile head.

[Problems to be Solved by the Invention]

The conventional pin structure in the pile head is complicated in structure, and since the continuity of the pile and the upper structure is broken in some way, there is a problem in workability and it tends to be an unstable structure. There is also a problem.

The present invention is intended to solve the above problems.

[Means for solving the problem]

In the pile head supporting structure of the present invention, the pile head having the pile main body is replaced with one or several thin rods made of metal having a small diameter to form a variable cross-section portion, thereby pinning the pile head. The support structure is close to the state. That is, at the attachment site of the upper structure such as the bottom of the building foundation and the top of the pile,
In order to transmit the pile supporting force, the cross-sectional area of the rod-shaped body of the variable cross-section has to be the same as that of the pile main body, and the bending rigidity of the pile head is higher than that of the pile main body. I made it smaller.

The rod-shaped body is made of steel or other metal and can have various cross-sections such as solid and hollow.

The rod-shaped body at the upper end of the pile can also have a damper function in response to shaking due to an earthquake, and can follow horizontal deformation while maintaining axial force. In that case, the required damper function can be easily designed by variously selecting the length, rigidity, and strength of the rod-shaped body, or by combining rod-shaped bodies having different rigidity.

The pile body may be a precast concrete pile such as a steel pipe pile or a precast concrete pile, or a cast-in-place concrete pile. Also, the joining or assembling of the pile main body and the rod-shaped body of the pile head may be integrated in advance or may be integrated on site.

In order to smooth the support between the foundation and the pile or to protect the rod-shaped body, separate one or several layers of rings made of concrete, etc. around the rod-shaped body from the altered cross-section to compensate for the cross-sectional change with respect to the body of the pile. It can also be placed. When a plurality of layers of rings are provided, it is possible to stably follow the horizontal displacement such as bending deformation of the rod-shaped body because there is no constraint between the layers.

[Work]

Regarding the supporting force for the vertical load from the superstructure, that is, the overload, the pile head and the pile main body have a cross-sectional area that can obtain a similar supporting force, so that the supporting ability is not impaired. For example, if the pile body is a steel pipe pile and the rod-shaped body of the pile head is made of steel of the same material, the cross-sectional areas may be made equal. If the pile body is reinforced concrete or composite pile, the converted areas should be the same.

In addition, the pile upper end is replaced with one or more metal rods having a smaller diameter than the pile body so that the bending rigidity of the pile head is smaller than that of the pile body. Since the head has a structure close to a pin, bending stress acting on the pile body is reduced, and the pile body can be economically designed.

Since the continuity is maintained from the pile body to the pile head bar and the foundation of the upper structure, it has a stable structure, and in terms of workability it does not differ much from the conventional rigid connection, rather. Reinforcement of the pile head becomes easy.

〔Example〕

 Next, the illustrated embodiment will be described.

FIG. 1 shows an embodiment of the present invention, in which a pile body 1
Is a steel pipe pile, and a solid steel rod is used as the rod-shaped body 2. In this case, the cross-sectional area of the pile body 1 and the cross-sectional area of the rod-shaped body 2 are made equal. Regarding the sectional rigidity, that is, the bending rigidity, the pile main body 1 which is a steel pipe is obviously much larger.

The joint between the lower end of the rod-shaped body 2 and the pile main body 1 and the upper end of the rod-shaped body 2 and the upper structural foundation (not shown, but the two-dot chain line in the figure indicates the joint surface a to the upper structural foundation). For each, four wing-shaped ribs 3 and 4 are provided, and the ribs 3 at the lower end are inserted into and joined to the upper ends of the steel pipes that make up the pile body 2, and the ribs 4 at the upper end are made of concrete in the superstructure foundation part. It has a structure to be embedded in. Of course, the joining structure is not limited to that of this embodiment, and various structures are conceivable. For example, instead of the rib 4 at the upper end, a stud bolt or other various shear connectors may be welded to the rod-shaped body. It should be noted that these can be assembled and integrated in advance in a factory, or can be assembled while driving piles on site.

FIG. 2 shows another embodiment in which a solid steel rod is used as the rod-like body 2 as in the above-mentioned embodiment, and a plurality of layers (4 layers in the figure) of rings 5 made of concrete are provided around the solid steel rod. Is. By filling the periphery of the rod-shaped body 2 whose cross-sectional outer shape is reduced, the ring 5 smoothes the support between the superstructure foundation and the pile main body 1 and also has a function of protecting the rod-shaped body 2 part. As described above, since there is no constraint between layers, it is possible to stably follow the horizontal displacement of the pile head.

As yet another embodiment, FIG. 3 shows a case where the pile main body 6 is a reinforced concrete pile built in the field (7 indicates a reinforcing bar in the figure) and three rod-shaped bodies 8 are arranged on the pile head. It is a thing. In this case, the rod-shaped bodies 8 are determined so that the total cross-section of the three rod-shaped bodies 8 has a cross-sectional area capable of obtaining a compressive force comparable to that of the reinforced concrete portion of the pile body. In the present embodiment, with respect to the portions of the pile main body 6 and the upper structural foundation portion embedded in the concrete, the rod-shaped bodies 8 are connected to each other by the joint plate 9 so that the mutual displacement does not occur.

FIG. 4 shows an example of the application position of the pile head support structure of the present invention. A pile is arranged near the position of the foundation slab column as the superstructure foundation, and the pile head is used as a pin according to the present invention. It has a close structure. Note that FIG. 4 shows only an example, and the present invention can be applied to any pile that supports an upper structure.

〔The invention's effect〕

In the pile head support structure of the present invention, since the rod-shaped body of the pile head has the same support capacity as the pile body and the bending rigidity is much smaller than that of the pile body, the pile head has a structure close to a pin, The bending stress acting on the main body is reduced, and the pile main body can be economically designed.

Since the structure for connecting the pile body to the superstructure foundation is simple, it has excellent workability and is structurally stable.

[Brief description of drawings]

FIG. 1 is a perspective view of a pile head showing an embodiment of the present invention, and FIG.
Drawing and Drawing 3 are perspective views of the pile head in other examples,
FIG. 4 is a vertical sectional view showing an example of a support structure for the upper structure. 1 ... pile body, 2 ... rod-shaped body, 3,4 ... rib, 5 ... ring, 6 ... pile body, 7 ... rebar, 8 ... rod-shaped body, 9 ...
… Joining plate, 10… Superstructure foundation

Claims (4)

[Claims] 1. A pile-shaped rod of the varying cross-section portion, which comprises one or a plurality of metal rod-like bodies having a smaller diameter than the pile body at the upper end of the pile and has a bending rigidity smaller than that of the pile body. A pile head supporting structure, wherein a cross-sectional area of the body is a cross-sectional area capable of obtaining a vertical supporting force equivalent to that of the pile main body, and an upper structure is supported by an upper end portion of the rod-shaped body. 2. The pile main body is a steel pipe, and the modified cross-section portion is composed of one or a plurality of steel rods located inside the cross-section of the steel pipe in plan view, and the cross-sectional area of the steel pipe and the modified cross-section. The pile head support structure according to claim 1, wherein the areas of the parts are equal. 3. The pile body is made of reinforced concrete,
The pile head support structure according to claim 1, wherein the modified cross-section portion is composed of one or a plurality of steel rods located inside the cross-section of the steel pipe when viewed in plan. 4. The pile head supporting structure according to claim 1, wherein a ring for compensating for a cross-sectional change with respect to the pile main body portion is provided around the variable cross-section portion in a single layer or a plurality of layers separated from the variable cross-section portion.