JP2000282484A - Pile head structure of rc cast-in-place pile - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make a pile head bending moment as small as possible and to maintain the required connection between the foundation of a structure and a pile. SOLUTION: In this pile head structure of an RC cast-in-place pile, a reinforced concrete foundation 10 of a structure is connected via a joint member 30 to the pile head part 21 of a cast-in-place reinforced concrete pile 20 supporting the foundation. The joint member 30 is in the form of a column having a smaller diameter than the pile 20, with its upper half 31 buried in the foundation 10 and its lower half 32 buried in the pile 20. The joint member 30 is located on the axis of the pile 20.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pile head structure of an RC cast-in-place pile, and more particularly to a pile head structure of an RC cast-in-place pile for reducing a pile head bending moment.

[0002]

2. Description of the Related Art The stress of a pile is given as the sum of "axial stress", "bending stress" and "shear stress". Generally, a pile used as a foundation of a structure such as a building receives only a vertical force at all times. Therefore, only “axial stress” occurs in the pile.

On the other hand, in the event of an earthquake, a horizontal force acts as an inertial force of the earthquake in addition to a vertical force, so that both "axial stress" and "bending stress" occur in a pile. The pile is designed so that the total stress, which is the sum of the two stresses, is below the allowable value.

In the design of a substructure of a building using an RC cast-in-place pile based on such a design standard, a pile head moment Mo is a major factor in determining a pile reinforcement amount and a connecting beam reinforcement amount. FIG. 2 shows distribution diagrams of the bending moment of the pile in the case of the pile head fixing structure and the case of the pin connection structure.

As apparent from FIG. 2, the bending moment is 0.645 times smaller in the case where the pile head has the pin connection structure than in the case where the pile head is fixed. Further, in the design of the foundation beam, since the pile head bending moment becomes zero, there is no need to consider the design. Therefore, for piles that do not pull out, it can be said that it is preferable to lower the pile head fixing degree as much as possible, that is, to use a pin connection structure.

When this concept is actually adopted, for example, it is conceivable that a foundation that is a part of the foundation of a building and a pile that supports the foundation have a pin connection structure. However, there is a problem in simply using a pin connection structure.

That is, it is necessary that the foundation and the pile are connected so that the shear force acting between them can be transmitted.
Moreover, it is necessary to give consideration to transmitting the axial force to the pile itself via its foundation in accordance with the load of the building. Further, it is necessary to provide a sufficient margin for the rotation angle of the pile head.

[0008]

SUMMARY OF THE INVENTION A pile head structure of an RC cast-in-place pile according to the present invention is to minimize the bending moment of the pile head and to ensure a necessary connection between the structure and the pile. It is an object to provide a pile head structure of an RC cast-in-place pile that can be used.

[0009]

According to the present invention, there is provided a pile head structure of an RC cast-in-place pile, in which a reinforced concrete foundation of a structure and a pile head portion of an RC cast-in-place pile supporting the foundation are connected via a joint member. It is a pile head structure of an RC cast-in-place pile, in which the joint members are columnar with a smaller diameter than the pile, the upper part is buried on the foundation side, the lower part is buried on the pile side, and located on the axis of the pile It is characterized by its structure.

Specifically, it is preferable to provide a gap between the foundation and the pile head, and to load an insulating material such as styrofoam into the gap.

[0011] Further, of the foundation and the pile, at least the foundation part and the pile head part around the joint member may be made of concrete having higher strength than other parts.

At this time, it is preferable that the joint member is designed to have higher strength than the foundation portion and the pile portion.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows the R according to the invention.
It is sectional drawing of the principal part which shows the pile head structure of C cast-in-place pile.

In FIG. 1, reference numeral 10 denotes a reinforced concrete foundation for a structure such as a building, and reference numeral 20 denotes an RC cast-in-place reinforced concrete pile that supports a part of the reinforced concrete foundation 10.

The foundation 10 and the pile 20 are connected to the joint member 3
0. The joint member 30 has a columnar shape having a circular or polygonal cross section, and has a smaller cross section than the cross section of the pile 20.

There is a gap between the foundation 10 and the pile 20,
An insulating material 40 such as a styrofoam is loaded in the gap. Accordingly, the pile head portion 21 is connected to the foundation 10 only via the joint member 30.

The joint member 30 is located on the axis of the pile 20. The upper half 31 is embedded in the foundation 10, and the lower half 32 is embedded in the pile head 20. As a result, the foundation 10 and the pile 20 have a connection structure close to a pin connection with a reduced degree of fixing of the pile head, but the entire axial force is transmitted to the pile 20 by the joint member 30.

The joint member 30 is made of high-strength CFT (filled steel pipe concrete) or an iron ingot, and is designed to have sufficient strength even in a small cross section. The embedding length of the joint member 30 is designed to be long enough to transmit a shearing force from the joint member 30 to the pile 20.

Of the foundation 10 and the pile 20, the foundation bottom 11 around the joint member 30 and the pile head 21 of the pile 20
Uses higher strength concrete than other parts.
The range in which the pile head portion 21 is made of high-strength concrete is approximately 45 degrees from the lower portion of the joint member 30 as shown in the figure, from the state of stress applied to the pile head portion. In order to further improve the strength of the pile head portion 21, the hoop reinforcement 23 of the pile head portion 21 has an increased bar arrangement density.

The main reinforcement 22 required for the pile 20 is arranged, but the main reinforcement 22 has a reinforcement arrangement that does not settle on the foundation.

The thickness of the insulating material 40 such as styrofoam loaded between the foundation 10 and the pile 20 is set to a thickness that allows a sufficient margin for the rotation angle of the pile head. I have.

With the above-mentioned pile head structure, the entire axial force is transmitted to the pile 20 via the joint member 30. Since the reinforced concrete foundation 10 and the pile 20 have a connection structure close to a so-called pin connection in which the degree of fixing of the pile head is lowered via the joint member 30, the pile head bending moment can be reduced.

Therefore, according to the present invention, by reducing the pile head bending moment, the amount of reinforcement of the pile itself can be reduced, and at the same time, the pile head bending moment is small even in the design of the connecting beam. This has the advantage that the amount of bar arrangement can be reduced.

As described above, the present invention has been described in detail based on the embodiments. However, the present invention is not limited to the above embodiments, and various changes can be made without departing from the spirit of the present invention. It is a matter of course.

[0025]

The pile head structure of an RC cast-in-place pile according to the present invention is constructed such that a reinforced concrete foundation of a structure and a pile head portion of an RC cast-in-place pile supporting the foundation are connected via a joint member. Is characterized by a structure in which the upper part is buried on the foundation side, the lower part is buried on the pile side, and it is located on the axis of the pile. It is possible to achieve the effect of making the structure as small as possible and ensuring the required connection between the structure and the pile.

More specifically, a further effect is provided by providing a gap between the foundation and the pile head and loading an elastic material such as styrofoam into the gap.

Further, of the foundation and the pile, at least the foundation portion and the pile head portion around the joint member are made of concrete having higher strength than the other portions, and the joint member is made of concrete higher than the concrete of the foundation portion and the pile head portion. By designing to have high strength, it has the effect of ensuring a safe and secure connection between the structure and the pile.

[Brief description of the drawings]

FIG. 1 is a sectional view of a main part showing a pile head structure of an RC cast-in-place pile according to the present invention.

FIG. 2 is a distribution diagram of a bending moment of a pile in a case where a pile head is fixed and a case where a pile head pin is connected.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Reinforced concrete foundation 11 Foundation bottom part 20 Pile 21 Pile head part 22 Main reinforcement 23 Hoop reinforcement 30 Joint member 31 Upper half (upper part) 32 Lower half part (lower part) 40 Insulation material

Claims (4)

[Claims] 1. A pile head structure of an RC cast-in-place pile in which a reinforced concrete foundation of a structure and a pile head portion of an RC cast-in-place pile supporting the foundation are connected via a joint member. Is a pillar shape smaller in diameter than the pile, the upper part is buried on the foundation side, the lower part is buried on the pile side,
And RC located on the axis of the pile.
Pile head structure of cast-in-place pile. 2. A pile head of an RC cast-in-place pile according to claim 1, wherein a gap is provided between the foundation and the pile head, and an insulating material such as styrofoam is loaded in the gap. Construction. 3. The RC according to claim 1, wherein a concrete having higher strength than other parts is used for at least a foundation portion and a pile head portion around the joint member among the foundation and the pile. Pile head structure of cast-in-place pile. 4. The pile head structure of a cast-in-place RC pile according to claim 1, wherein the joint member has higher strength than concrete of the foundation portion and the pile head portion.