JPH06220842A - Reinforced concrete pile with outer steel pipe - Google Patents

Abstract

PURPOSE:To easily manufacture an existing pile having a high bending strength at a low cost by inserting multiple reinforcing bars into a steel pipe, and integrating the steel pipe and the reinforcing bars with expanding concrete. CONSTITUTION:Erection bars 4 are welded to deformed reinforcing bars 2 having a high adhesion to concrete into a basket shape. It is inserted into a steel pipe 1 having the thickness of 4.5-9.0mm. The thickness of the steel pipe 1 can be determined by the required bending strength and the weight of the reinforcing bars 2. SKK490 is preferable for the material of the steel pipe 1. Expanding concrete 3 is injected into the steel pipe 1. The expanding concrete 3 is centrifugally molded while the steel pipe 1 is used as a formwork. The expanding concrete 3 is molded into a hollow cylindrical shape by the autoclave curing or atmospheric pressure steam curing. The steel pipe 1 and the reinforcing bars 2 are fixed and integrated by the expanding concrete 3.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ready-made pile used as a foundation for civil engineering and building structures.

[0002]

Bending performance as well as vertical axial force is required for ready-made piles used as the foundation of civil engineering and construction structures. As a ready-made pile suitable for such a purpose, there is known a hollow concrete pile (hereinafter referred to as SC pile) in which expansive concrete is integrally formed in a cylindrical shape on the inner surface of a steel pipe (hereinafter referred to as SC pile). This SC pile is intended to improve the adhesion between the steel pipe and the concrete by using expanded concrete to obtain a pile that is strong against bending moment.

Further, there is known a steel pipe concrete pile in which a plurality of rebars are arranged inside the steel pipe along its longitudinal direction, the rebars are welded to the steel pipe, and concrete is integrally molded into a cylindrical shape on the inner surface of the steel pipe. There is (actual Kaisho 51-14270
3 gazette). This pile is intended to improve the bending strength by welding the reinforcing bar to the steel pipe to integrate it with the steel pipe through the adhesion of the reinforcing bar and the concrete.

Further, there is known a steel pipe concrete pile in which a concrete pile having reinforcing bars is fitted into a steel pipe, and expansion mortar is injected into a gap between the concrete pipe and the steel pipe to integrate the concrete pile and the steel pipe (actually developed). 51-157
No. 104). In this steel pipe concrete pile, a concrete pile is manufactured in advance, and the pile is put into a steel pipe and adhered with expanded mortar to obtain bending strength.

[0005]

In the above-mentioned first SC pile, it was necessary to increase the thickness of the steel pipe in order to increase its bending strength. However, there is a problem that a steel pipe having a large diameter becomes extremely expensive as the thickness increases. In addition, the thickness of steel pipes on the market is rough because the standard width is rough, and if a steel pipe with a thickness one step higher is used, more bending strength than necessary will be obtained, resulting in higher costs. It was

The steel pipe concrete pile described in Japanese Utility Model Laid-Open No. 51-142703 has a problem that it takes time and labor to manufacture because the reinforcing rod must be welded to the steel pipe. Further, the adhesion between the steel pipe and the rebar is not good, and the concrete shrinks after curing to form a gap between the steel pipe and the concrete, so that there is a problem that the bending strength is reduced accordingly.

In the steel pipe concrete pile described in Japanese Utility Model Laid-Open No. 51-157104, a concrete pile with reinforcing bars is first formed, then inserted into the steel pipe, and then expanded mortar is injected between the concrete pile and the steel pipe. Since it sticks and sticks, it is troublesome in work and production efficiency is poor. Further, it was difficult to confirm whether the injection of the expanded mortar was carried out reliably, and there was a concern about the adhesive strength. Further, since the concrete pile is inserted, it is difficult for the concrete pile and the steel pipe to be coaxial with each other.

[0008] Therefore, an object of the present invention is to provide a concrete pile with an outer shell steel pipe which can obtain a high bending strength by using a steel pipe and a reinforcing bar, is easy to manufacture and is low in cost.

[0009]

The reinforced concrete pile with an outer shell steel pipe according to the present invention has a steel pipe having a thickness of 4.5 to 9.0 mm in the outer shell, and is hollow inside which is lined with expansive concrete. In the cylindrical concrete layer, a plurality of reinforcing bars not fixed to the steel pipe are arranged in the axial direction of the pile.

[0010]

According to the present invention, by inserting a plurality of reinforcing bars into a steel pipe and lining the steel pipe with expanded concrete to form a hollow cylindrical shape, the steel pipe and the reinforcing bar can be integrated with the expanded concrete. . Therefore, the required bending strength can be obtained without welding the conventional reinforcing bar to the steel pipe. As a result, even if the weight of the steel pipe is reduced as compared with the conventional SC pile by the weight of the reinforcing bar to be inserted into the steel pipe, the same bending strength and the like can be obtained. Therefore, the cost of the pile can be remarkably reduced because the thickness of the expensive steel pipe can be reduced by effectively using the inexpensive reinforcing bar.

[0011]

FIG. 1 is a partial perspective view schematically showing a reinforced concrete pile with an outer shell steel pipe of the present invention (hereinafter, simply referred to as a pile). In the figure, the pile is composed of a steel pipe 1, a hollow cylindrical expanded concrete 3 lined inside the steel pipe 1, and a plurality of reinforcing bars 2 arranged in the axial direction of the steel pipe 1.

The steel pipe 1 has a thickness of 4.5 to 9.0 mm, which can be selected from the sizes of commercially available steel pipes. The thickness of the steel pipe 1 can be determined from the required bending strength and the weight of the reinforcing bar 2 to be inserted. That is, if the required bending strength is determined, it can be increased or decreased depending on the amount of the reinforcing bars 2 to be inserted. Therefore, the thickness of the steel pipe 1 and the rebar 2
The amount of can be freely designed. However, the lower limit of the thickness of the steel pipe is determined by the strength capable of centrifugal molding and needs to be 4.5 mm or more. The upper limit is determined by the economically available thickness and is preferably 9.0 mm or less. Material is SKK4
It is preferable to use 00 or SKK490. Further, since the steel pipe 1 is replaced by the mold itself, it is economical in terms of industrial production.

The rebars 2 are not fixed to the steel pipes 1 and are arranged at required intervals in the axial direction of the pile, and are assembled with the spiral or ring-shaped rebars 4 by, for example, welding or clips to form a cage. Has been inserted. As the reinforcing bar 2, round steel, deformed reinforcing bar, or the like can be used, but deformed reinforcing bar having good adhesion to concrete is preferable. The diameter of the reinforcing bar 2 can be about 25 mm.

The expansive concrete 3 has expansibility upon hardening, and the expansive force firmly integrates the expansive concrete 3, the steel pipe 1 and the reinforcing bar 2. Next, the arrangement of the reinforcing bars 2 will be described. As shown in FIG. 1, by arranging the reinforcing bars at the necessary intervals over the entire length of the pile, bending strength and vertical axial force can be obtained in the pile. By the way, when a horizontal force acts on the pile, a bending moment is generated. Since this bending moment greatly appears on the upper part of the pile, the reinforcing bar may be placed on the upper part of the pile in an intensive manner for economic design, for example, as shown in FIG. FIG. 2 is a partial perspective view schematically showing the arrangement of reinforcing bars. In the figure, many reinforcing bars 2 are arranged in the upper part where bending strength is required, and the reinforcing bars 2 are arranged in paragraphs along the longitudinal direction. In this case, the reinforcing bar 2 does not have to be arranged over the entire length of the pile 5. In this way, it is possible to design a rational pile that reinforces only necessary parts without causing loss of reinforcing bars.

Next, in the method for manufacturing a pile of the present invention, first, the reinforcing bar 2
The assembly bar 4 is welded to form a cage shape, which is inserted into the steel pipe 1. Next, the expanded concrete 3 is poured into the steel pipe 1, and the steel pipe 1 is subjected to centrifugal molding using the frame as a mold, and is subjected to autoclave curing or normal pressure steam curing to form a hollow cylindrical shape. Steel pipe 1 by this expanded concrete 3
The reinforcing bars 2 are fixed to each other, and bending strength can be obtained by integrating these three members.

Next, the bending strength and deformation performance of the pile of the present invention and the conventional SC pile will be compared. The effects of changes in material and changes in the amount of rebar inserted were also investigated. Outer diameter 6
Using a steel pipe of 00 mm and a length of 9000 mm, a simple bending test was carried out by supporting a test body under the following conditions with a span of 8 m, and the result is shown in FIG. FIG. 3 shows a graph of deflection and load at the center of the pile. The vertical axis of the graph shows the load applied to the pile, and the horizontal axis shows the deflection of the center point by the simple bending test.

In the figure, as a blank, a steel pipe having a thickness of 4.
An unstripped test body of 5 mm in material SKK400 was used, and four types of test bodies A, B, C, and D described below were used as a reference for comparison. A is a conventional SC pile having a steel pipe thickness of 9.0 mm and a material of SKK400, which is unreinforced.
B is a pile of the present invention, which is a deformed rebar having a sectional area corresponding to a steel pipe thickness of 4.5 mm and a steel pipe thickness of 4.5 mm (material SD
30, diameter 25 mm × 14 pieces) are inserted. C
Shows that the material of the B test body is changed to SKK490. D is the number of inserted reinforcing bars of the C test body is increased to 18.

According to this result, B of the present invention is the same as the conventional A.
It is slightly lower than the curve of the SC pile, but there was no experimental difference. Further, it can be seen that when the material of the steel pipe is upgraded like C, the bending strength is increased. It can be seen that the bending strength of D increases as the amount of rebar inserted increases. From the above results, it is understood that a pile equivalent to a thick steel pipe pile can be obtained by inserting a reinforcing bar to compensate for the reduction in the thickness of the steel pipe used for the pile. Also, if the material of the steel pipe and the amount of rebar to be inserted are upgraded, it will appear as the performance improvement as it is, and the performance can be freely controlled in design.

[0019]

In the pile of the present invention, a plurality of reinforcing bars are inserted into the steel pipe, and the steel pipe and the reinforcing bars are integrated with each other by the expansive concrete. In addition, the required bending strength can be obtained, and the influence of heat is reduced. Thereby, even if the weight of the steel pipe is reduced by the weight of the reinforcing bar to be inserted into the steel pipe, the same bending strength can be obtained. In addition, the amount and length of the reinforcing bar can be freely changed according to the required bending strength, and the design can be made freely by combining the weight of the steel pipe and the weight of the reinforcing bar. Therefore, the cost of the pile can be remarkably reduced because the thickness of the expensive steel pipe can be reduced by effectively using the inexpensive reinforcing bar.

[Brief description of drawings]

FIG. 1 is a partial perspective view schematically showing a reinforced concrete pile with an outer shell steel pipe of the present invention.

FIG. 2 is a partial perspective view schematically showing the arrangement of reinforcing bars to be inserted in the pile of the present invention.

FIG. 3 is a graph of deflection and load at the center of the pile of the present invention.

[Explanation of symbols]

 1 Steel pipe 2 Reinforcing bar 3 Expanded concrete 4 Assembly bar 5 Pile

Claims (1)

[Claims] 1. A hollow-cylindrical concrete layer having a steel pipe having a thickness of 4.5 to 9.0 mm in its outer shell and lining with expanded concrete inside thereof is not fixed to the steel pipe. A reinforced concrete pile with an outer shell steel pipe, wherein a plurality of reinforcing bars are arranged in the axial direction of the pile.