JP6814610B2 - Concrete pile - Google Patents

Description

The present invention relates to a reinforced concrete concrete pile in which hoop bars surrounding the pile main bar are arranged at high density only on the upper side of the pile, or high-strength reinforcing bars are used for the hoop bars.

Conventionally, as piles for supporting a building, there are concrete piles provided with a plurality of main bars extending in the vertical direction and hoop bars wound around the main bars.
Patent Document 1 shows the structure of hoop muscles wound around the outer periphery of a plurality of main muscles. In the structure of this hoop bar, a multi-layered winding portion in which a plurality of spiral reinforcing bars are stacked and wound, and a single winding portion in which a single spiral reinforcing bar is wound are alternately arranged in the axial direction of the main bar. It is formed.

Patent Document 2 discloses a method of arranging reinforced concrete piles by on-site construction. Specifically, after temporarily fixing the main bars of the reinforced concrete pile at predetermined intervals with closed type setup bars, spiral hoop bars are continuously built on the outer circumference of the main bars at right angles to the main bars, and the main bars and spiral bars are tied together. To form a reinforcing bar cage.

Patent Document 3 discloses a hollow precast concrete pile in which a plurality of reinforcing bars are spirally wound around a shaft reinforcing bar extending in the axial direction at predetermined intervals.

Japanese Unexamined Patent Publication No. 2007-270486 Japanese Patent No. 3094368 Jitsukaisho 61-008220

Since a large horizontal load acts on the joint between the lower surface of the building and the pile, it is necessary to increase the strength of the upper part of the pile more than the strength of the middle part of the pile and the lower part of the pile. However, in the above-mentioned structures of Patent Documents 1 to 3, the arrangement of the pile main reinforcement and the hoop reinforcement is the same over the entire length of the pile, resulting in high cost.

An object of the present invention is to provide a concrete pile capable of resisting a large horizontal load acting on a joint portion between a building lower surface and a pile at low cost.

As a reinforced concrete pile structure that supports a high-rise building, the present inventors provided a double spiral bar in which a plurality of spiral hoop bars are stacked and wound on the upper side of the pile, and a single spiral bar is provided in the middle part of the pile and the lower part of the pile. We have invented the concrete pile of the present invention, paying attention to the fact that the required amount of shear reinforcement can be secured and the space required for filling the concrete can be widened by arranging the reinforcing bars.

The concrete pile of the first invention (for example, the concrete pile 1 described later) has a plurality of main bars extending in the vertical direction (for example, the main bar 20 described later) and a hoop bar wound around the main bar (for example, the main bar 20 described later). In a concrete pile provided with a hoop bar 21) described later, the shear strength of the pile upper portion (for example, the pile upper portion 30 described later) is the pile intermediate portion (for example, the pile intermediate portion 31 described later) and the pile lower portion (for example). It is characterized in that it is higher than the shear strength of the pile lower portion 32) described later.

According to the present invention, the shear strength at the upper part of the pile is made higher than that at the middle part of the pile and the lower part of the pile, instead of making the shear strength the same over the entire length of the pile, thereby reducing the horizontal displacement generated at the upper part of the pile. , The toughness performance of the pile body at the middle part of the pile and the lower part of the pile can be improved. In addition, by increasing the shear strength only for the upper part of the pile that is joined to the lower surface of the building, the joint part between the lower surface of the building and the pile can be made at a lower cost than when the shear strength is the same over the entire length of the pile. Can withstand large horizontal loads acting.
Specifically, for example, in the upper part of the pile, the yield strength of the hoop reinforcement, the diameter of the reinforcing bar, the amount of reinforcement of the hoop reinforcement, or the concrete strength is increased as compared with the middle portion of the pile and the lower part of the pile. Alternatively, place a steel ring on top of the pile.

In the concrete pile of the second invention, the hoop bar at the upper part of the pile has a lap winding portion (for example, a lap winding portion 23 described later) in which a plurality of spiral reinforcing bars are stacked and wound up, and the pile intermediate. The hoop bar of the portion and the lower portion of the pile is characterized by being a single spiral reinforcing bar.

According to the present invention, the hoop bar at the upper part of the pile is provided with a lap winding portion in which a plurality of spiral reinforcing bars are stacked and wound up, and one spiral reinforcing bar is provided at the hoop bar at the middle portion of the pile and the lower part of the pile. By using the pile, the shear strength of the upper part of the pile can be easily made higher than the shear strength of the middle part of the pile and the lower part of the pile without changing the distance between the hoop bars over the entire length of the pile.
Specifically, since a plurality of spiral reinforcing bars are stacked and wound up at the upper part of the pile, the hoop bar spacing is set between the middle part of the pile and the hoop bar at the lower part of the pile while ensuring the required amount of reinforcing bars for the hoop bars. In comparison, it is only necessary to narrow the diameter of one hoop bar, so that the bar can be arranged at a high density and concrete can be reliably placed in every corner of the pile.
Further, by stacking and winding a plurality of spiral reinforcing bars, only one hoop bar is wound around the main pile bar, and it is possible to prevent the hoop bar from increasing in cover thickness.
In addition, since spiral (spiral type) reinforcing bars are used as the hoop bars, a predetermined interval is maintained as compared with the case of using an annular or rectangular ring hoop bar that is bent into a closed shape for each hoop bar. Multiple hoop muscles can be tied to the main muscle in a short time.

In the concrete pile of the third invention, the hoop bar at the upper part of the pile is a spiral reinforcing bar having a higher strength and / or a larger diameter than the hoop bar at the middle portion of the pile and the lower part of the pile, and the hoop at the upper part of the pile. The distance between the streaks is equal to or greater than the distance between the hoop streaks in the middle portion of the pile and the lower part of the pile.

According to the present invention, by using a high-strength reinforcing bar, a large-diameter reinforcing bar, or a high-strength large-diameter reinforcing bar in the upper part of the pile, the shear strength of the upper part of the pile can be increased without narrowing the distance between the hoop bars. It can be easily higher than the shear strength of the middle part and the lower part of the pile. Further, by using high-strength hoop bars on the upper part of the pile, the required shear strength can be realized without arranging the upper part of the pile at high density.

In the concrete pile of the fourth invention, the main bar is arranged only on the upper part of the pile (for example, the inner main bar 24 described later) and outside the inner main bar and over substantially the entire length of the pile. The hoop muscle is a single spiral reinforcing bar (for example, the inner side described later) which is provided with the outer main muscle (for example, the outer main muscle 25 described later). It is characterized by including a hoop muscle 26) and an outer hoop muscle (for example, an outer hoop muscle 27 described later) which is a single spiral reinforcing bar wound around the outer main muscle.

According to the present invention, the inner and outer main bars are arranged only on the upper part of the pile, and the hoop bars are spirally arranged so as to surround the respective main bars, thereby increasing the shear strength and bending strength of the upper part of the pile in the middle of the pile. It can easily be higher than the shear strength and bending strength of the part and the bottom of the pile.

According to the present invention, it is possible to provide a concrete pile capable of resisting a large horizontal load acting on a joint portion between a building lower surface and a pile at low cost.

It is a vertical cross-sectional view of the foundation structure provided with the concrete pile which concerns on 1st reference example . It is a cross-sectional view of AA of the concrete pile shown in FIG. It is an enlarged vertical sectional view of the pile middle part and the pile lower part, and the pile upper part of a concrete pile. It is a schematic diagram of the relationship between the force acting on the pile and the horizontal displacement at the time of an earthquake. It is a longitudinal sectional view of a basic structure with a concrete pile according to implementation embodiments. A B-B cross-sectional view of the concrete pile as shown in FIG. It is a vertical sectional view of the foundation structure provided with the concrete pile which concerns on the 2nd reference example . It is a vertical sectional view of the foundation structure provided with the concrete pile which concerns on the 3rd reference example . It is C-C in cross-sectional view of a concrete pile as shown in FIG. It is a vertical sectional view of the foundation structure provided with the concrete pile which concerns on 4th reference example .

In the present invention, in a concrete pile having a substantially uniform pile diameter, the shear strength of the upper part of the pile is not constant by arranging the pile main reinforcement and the hoop reinforcement in the same form over the entire length of the pile. It should be higher than the middle part of the pile and the lower part of the pile. Specifically, as a concrete pile, only the first reference example (FIGS. 1 to 4) in which a double spiral bar in which a plurality of spiral type hoop bars are stacked and wound up is arranged only on the upper side of the pile, and only on the upper side of the pile. the inner pile main reinforcement and outer piles main reinforcement arranged, implementation form you reinforcement a hoop in each of the main reinforcement (5, 6) and, pile upper side only high strength spiral hoop or large diameter spiral A second reference example (FIG. 7) in which the mold hoop reinforcement is arranged, a third reference example (FIGS. 8 and 9) in which a steel ring is arranged on the outer peripheral surface of the pile only on the upper side of the pile, and only the upper side of the pile. There is a fourth reference example (FIG. 10) of constructing a pile with high-strength concrete.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the description of the following embodiments, the same components will be designated by the same reference numerals, and the description thereof will be omitted or simplified.
[ First reference example ]
FIG. 1 is a vertical sectional view of a foundation structure 10 of a building provided with a concrete pile 1 according to a first reference example of the present invention. FIG. 2 is a cross-sectional view taken along the line AA of the concrete pile shown in FIG.
The foundation structure 10 is provided on the reinforced concrete concrete pile 1 driven into the ground, the footing 11 supported at the upper end of the concrete pile 1, the foundation beam 12 connecting the footings 11 to each other, and the footing 11. It is provided with a pillar 13.

The concrete pile 1 has a substantially cylindrical shape, and includes a plurality of main bars 20 extending in the vertical direction and hoop bars 21 wound around the main bars 20.
Hereinafter, the upper part of the concrete pile 1 is referred to as the pile upper portion 30, the intermediate portion is referred to as the pile intermediate portion 31, and the lower portion is referred to as the pile lower portion 32.

FIG. 3A is an enlarged vertical sectional view of the pile intermediate portion 31 and the pile lower portion 32 of the concrete pile 1. FIG. 3B is an enlarged vertical sectional view of the pile upper portion 30 of the concrete pile 1.
The hoop bars 21 of the pile intermediate portion 31 and the pile lower portion 32 are one spiral reinforcing bar.
The hoop bar 21 of the pile upper portion 30 is composed of a lap winding portion 23 in which two spiral (spiral type) reinforcing bars are laid and wound.

Here, hoop bars 21 having the same yield strength and reinforcing bar diameter are used in the pile upper portion 30, the pile intermediate portion 31, and the pile lower portion 32. As a result, it is possible to reduce the risk of making a mistake in the reinforcing bar used at the time of reinforcing bar arrangement, and it is possible to improve the efficiency of the reinforcing bar arrangement work. Further, the intervals between the hoop muscles 21 and the lap winding portions 23 are also substantially the same.
Therefore, the shear strength of the pile upper portion 30 of the concrete pile 1 is higher than the shear strength of the pile intermediate portion 31 and the pile lower portion 32.

Here, assuming that the shear reinforcing bar ratio is p _w and the yield strength of the shear reinforcing _bar is σ _wy , the shear reinforcing bar mass Q is expressed by the following equation (1).
Q = p _w × σ _wy・ ・ ・ (1)

Hereinafter, the subscript will be 1 for the middle part of the pile and the lower part of the pile, and the subscript will be 2 for the upper part of the pile.
Therefore, for example, in the middle part of the pile and the lower part of the pile, if p _w1 is 0.2% and σ _wy1 is 390 N / mm ² , Q ₁ is 0.78 N / mm ² . Meanwhile, the pile top, since the lap-wound portion is _provided, next to 0.4% of 2 times the _{p w2} is _{p w1,} As a result, double 1.56N / mm ² next _{Q 2} 'also _{Q 1} , The shear strength of the upper part of the pile can be increased.

FIG. 4A is a schematic diagram showing the behavior of buildings and piles during an earthquake.
When an earthquake occurs, a horizontal force H acts on the building, and as shown in FIG. 4A, the pile is deformed.
FIG. 4B is a schematic view showing the horizontal displacement of the present invention, the conventional ordinary strength pile, and the conventional high yield strength pile. In FIG. 4B, the solid line is the distribution of the horizontal displacement of the pile of the present invention, the one-point broken line is the distribution of the horizontal displacement of the conventional ordinary strength pile, and the broken line is the distribution of the horizontal displacement of the conventional high-bearing pile. is there.

Here, examples of the ordinary strength piles include centrifugally formed reinforced concrete RC piles, centrifugally formed prestressed concrete PC piles, and cast-in-place reinforced concrete piles. The high-strength piles include high-strength prestressed concrete PHC piles formed by centrifugal force, high-strength prestressed reinforced concrete PRC piles formed by centrifugal force, concrete SC piles with outer shell steel pipes formed by centrifugal force, cast-in-place steel pipe concrete piles, and ground. The middle wall pile can be mentioned.

A large shear force acts in the opposite direction at the joint between the building and the upper part of the pile in an attempt to cancel the horizontal force acting on the building. At that time, the horizontal displacement generated in the pile is the largest at the upper end of the pile and decreases toward the lower end side of the pile. Corresponding to the distribution of this horizontal displacement is the distribution of the bending moment acting on the pile.

Since the conventional high yield strength pile has a structure having high strength over the entire length of the pile, the horizontal displacement of the pile can be suppressed and reduced over the entire length as shown by the broken line in FIG. 4 (b). However, such a high yield strength pile has a problem that the construction method is complicated, the production time is long, and the cost is high.
On the other hand, the pile of the present invention is characterized in that only the shear strength of the upper part of the pile is increased more than that of the middle part of the pile and the lower part of the pile, so that only the amount of horizontal displacement generated in the upper part of the pile is suppressed. Therefore, it is possible to realize a reinforced concrete pile having high toughness performance and high shear strength.

The concrete pile 1 includes a ready-made pile that is manufactured in advance at a factory, transported to a site and driven, and a cast-in-place pile to be constructed at the site.
When the concrete pile 1 is a ready-made pile, it is manufactured by the following procedure. That is, at the factory, a reinforcing bar cage is assembled with the main reinforcing bar 20 and the hoop reinforcing bar 21, and the reinforcing bar cage is placed in a steel cylindrical formwork extending in the horizontal direction, and then concrete is cast in the formwork. Install and manufacture.

When the concrete pile 1 is a cast-in-place pile, it is constructed by the following procedure. First, at the site, a reinforcing bar cage is assembled with the main bar 20 and the hoop bar 21. Next, a pile hole extending in the vertical direction is formed on the ground surface, a reinforcing bar cage is put into the pile hole, and then concrete is poured into the pile hole for construction.

According to this reference example , there are the following effects.
(1) The shear strength of the pile upper portion 30 was made higher than the shear strength of the pile intermediate portion 31 and the pile lower portion 32. A large horizontal load acts on the joint between the footing 11 and the concrete pile 1, but since the shear strength is increased only for the pile upper portion 30 joined to the footing 11, it is possible to resist this large horizontal load at low cost.

(2) The hoop bar 21 of the upper part 30 of the pile is provided with a lap winding portion 23 in which two spiral reinforcing bars are overlapped and wound, and the hoop bar 21 of the middle portion 31 of the pile and the lower part 32 of the pile is combined with one hoop bar 21. A spiral reinforcing bar was used. Therefore, the shear strength of the pile upper portion 30 can be easily made higher than the shear strength of the pile intermediate portion 31 and the pile lower portion 32.
Further, since two spiral reinforcing bars are stacked and wound up at the upper portion 30 of the pile, the required amount of reinforcing bars for the hoop reinforcing bars 21 can be secured, and the hoop reinforcing bar spacing required for filling concrete can be widely secured. Concrete can be reliably placed in every corner.
Further, by stacking and winding a plurality of spiral reinforcing bars, it is possible to prevent the hoop reinforcing bar 21 from increasing in cover thickness.

[Implementation Embodiment
Figure 5 is a longitudinal sectional view of the base structure 10 having a concrete pile 1A according to the implementation embodiments of the present invention. FIG. 6 is a cross-sectional view taken along the line BB of the concrete pile 1A shown in FIG.
In the present embodiment, the concrete pile 1A includes, as main bars, an inner main bar 24 arranged at the upper portion 30 of the pile and an outer main bar 25 arranged outside the inner main bar 24 and over substantially the entire length of the concrete pile 1. Be prepared.

Further, the concrete pile 1A has an inner hoop bar 26, which is a spiral reinforcing bar wound around the inner main bar 24, and a spiral wound around the outer main bar 25, as hoop bars. It is provided with an outer hoop bar 27, which is a shaped reinforcing bar.
Further, the distance between the hoop muscles 26 and the distance between the hoop muscles 27 are substantially the same.

Further, although not shown, a plate or a hook is provided at the end of the inner main bar 24 on the pile intermediate side side, and is fixed and fixed. By providing the plate end or the hook at the end of the inner main bar 24 in this way, the fixing length of the inner main bar 24 embedded in the pile concrete can be shortened.

Therefore, for example, in the middle part of the pile and the lower part of the pile, if p _w1 is 0.2% and σ _wy1 is 390 N / mm ² , Q ₁ is 0.78 N / mm ² . Meanwhile, the pile top, since the inner hoop is _provided, next to 0.4% of 2 times the _{p w2} is _{p w1,} As a result, double 1.56N / mm ² next _{Q 2} 'also _{Q 1} , The shear strength of the upper part of the pile can be increased as in the first embodiment.

According to this embodiment, in addition to the above-mentioned effect (1), there are the following effects.
(3) Since the inner main bar 24 and the outer main bar 25 are arranged on the pile upper part 30 and one spiral reinforcing bar is used as each hoop bar, the shear strength of the pile upper part 30 is adjusted to the pile intermediate part 31 and the pile lower part. It can easily be higher than the shear strength of 32.

(4) Since the inner main bar 24 and the outer main bar 25 are arranged on the pile upper portion 30, the bending strength is higher than that of the pile intermediate portion 31 and the pile lower portion 32, and high toughness performance can be realized.

[ Second reference example ]
FIG. 7 is a vertical cross-sectional view of the foundation structure 10 provided with the concrete pile 1B according to the second reference example of the present invention.
In this reference example , one spiral high-strength reinforcing bar is arranged on the hoop bar 21a of the upper part 30 of the pile, and the hoop bar 21b of the middle part 31 of the pile and the lower part 32 of the pile has lower strength than the upper part of the pile. One spiral reinforcing bar is arranged.
In this reference example , the distance between the hoop bars 21a of the pile upper portion 30 and the distance between the hoop bars 21b of the pile intermediate portion 31 and the pile lower portion 32 are substantially the same.

Therefore, for example, in the middle part of the pile and the lower part of the pile, if p _w1 is 0.2% and σ _wy1 is 390 N / mm ² , Q ₁ is 0.78 N / mm ² . On the other hand, since high-strength reinforcing bars are used in the upper part of the pile, p _w2 is 0.2%, which is equal to p _w1 , and if σ _wy2 is 490 N / mm ² , Q ₂ becomes 0.98 N / mm ² , and Q ₁ The shear strength of the upper part of the pile can be increased.

Reinforcing bars with a reinforcing bar diameter of D19 are used for the hoop bars at the upper part of the pile, and spiral reinforcing bars with a reinforcing bar diameter of D16 are used for the hoop bars at the middle part of the pile and the lower part of the pile. May be good. In this case as well, the shear strength of the hoop muscle at the upper part of the pile can be made higher than the shear strength at the middle part of the pile and the lower part of the pile.

According to this reference example , in addition to the above-mentioned effect (1), there are the following effects.
(5) Since high-strength reinforcing bars are used for the hoop bars 21 of the upper part 30 of the pile, the distance between the hoop bars 21 is not narrower than the distance between the hoop bars 21 at the middle part of the pile and the lower part of the pile. The shear strength can be easily made higher than the shear strength of the pile intermediate portion 31 and the pile lower portion 32.

The present invention is not limited to the above-described embodiment, and modifications, improvements, and the like within the range in which the object of the present invention can be achieved are included in the present invention.
The implementation described above, was used spiral rebar as hoop 21 is not limited thereto, it may be used an annular or rectangular ring rebar as hoop.

[ Third reference example ]
Further, as shown in FIGS. 8 and 9, the hoop bar 21 is composed of one spiral reinforcing bar over the entire length of the concrete pile 1C, and further, the material of the reinforcing bar used for the hoop bar 21 and the hoop bar. The shear strength of the pile upper portion 30 may be increased by arranging the cylindrical steel ring 40 only on the outer peripheral surface of the concrete pile 1 on the pile upper portion 30 side with substantially the same distance between the 21.

In here, along the steel ring 40 in the circumferential direction in advance in a plurality of arc-shaped ring member, on site, it may be connected to the divided ring members together with bolts. This ring member is a thin steel plate to which a reinforcing steel material is attached, and can also be used as a concrete formwork material. When the concrete pile 1C is constructed on site, a support reinforcing bar 41 extending substantially horizontally and linearly is attached to the hoop bar, and the steel ring 40 is supported by the supporting reinforcing bar 41.
Even in this way, the same effect as (1) described above can be obtained.

[ Fourth reference example ]
Further, as shown in FIG. 10, the hoop bars 21 are composed of one spiral reinforcing bar over the entire length of the concrete pile 1D, and further, the material of the reinforcing bars used for the hoop bars 21 and the hoop bars 21 are used with each other. The upper portion 30 of the pile may be constructed of high-strength concrete 50 (indicated by diagonal lines in FIG. 10), and the intermediate portion 31 of the pile and the lower portion 32 of the pile may be constructed of low-strength concrete 51 with substantially the same spacing. In this case, since the pile upper portion 30 is made of concrete having a higher strength than the pile intermediate portion 31 and the pile lower portion 32, the shear strength of the pile upper portion 30 is made higher than the shear strength of the pile intermediate portion 31 and the pile lower portion 32. Can be done.

When constructing this concrete pile 1D as a cast-in-place pile at a construction site, first, a construction hole is provided in the ground, and then a reinforcing bar cage assembled with a main bar and a hoop bar is inserted into the construction hole. After that, the first concrete (low-strength concrete 51) is poured into the construction hole from the lower part of the pile to the middle part of the pile, and temporarily stopped. After that, within one hour from the time when the first concrete was stopped, the second concrete, which has higher strength than the first concrete, is again formed in the construction hole so that the joint surface is not formed as a fragile part in the cross section of the pile body. (High-strength concrete 50) is placed. This makes it possible to form a concrete pile 1D having high-strength concrete on the upper side of the pile.

When the concrete pile 1D is manufactured as a ready-made pile at a PC factory, the reinforcing bar cage to be driven into the pile is placed in a cylindrical steel mold extending in the horizontal direction, and then the upper part of the pile and the middle part of the pile are connected. A mesh mold is installed on the surface so as to cross the reinforcing bar cage, and in this state, the first concrete (low-strength concrete 51) is poured from the lower part of the pile to the middle part of the pile. After placing the first concrete, the mesh formwork is removed, and a second concrete (high-strength concrete 50) having a higher strength than the first concrete is placed on the upper part of the pile to form the concrete pile 1D.

1, 1A, 1B, 1C, 1D ... Concrete pile 10 ... Foundation structure 11 ... Footing 12 ... Foundation beam column ... 13
20 ... Main bar 21, 21a, 21b ... Hoop bar 23 ... Overlap winding part 24 ... Inner main bar 25 ... Outer main bar 26 ... Inner hoop bar 27 ... Outer hoop bar 30 ... Pile upper part 31 ... Pile middle part 32 ... Pile lower part 40 ... Steel Ring 41 ... Supporting rebar 50 ... High-strength concrete 51 ... Low-strength concrete

Claims (1)

A concrete pile having a plurality of main bars extending in the vertical direction and hoop bars wound around the main bars.
The main bar includes an inner main bar arranged only on the upper part of the pile and an outer main bar arranged outside the inner main bar and over substantially the entire length of the pile.
The hoop bars are an inner hoop bar, which is a spiral reinforcing bar wound around the inner main bar, and an outer hoop, which is a spiral reinforcing bar wound around the outer main bar. With a streak,
A concrete pile characterized in that the shear strength of the upper part of the pile is higher than the shear strength of the middle part of the pile and the lower part of the pile.

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