JP6784355B2 - Shear reinforcement PC pile - Google Patents

Description

The present invention relates to shear reinforced PC piles used for foundations of structures and the like.

Conventionally, in foundation construction of structures, prestressed concrete piles (hereinafter referred to as PC piles), prestressed reinforced concrete piles (hereinafter referred to as PRC piles), prestressed high-strength concrete piles (hereinafter referred to as PHC piles), etc. are used according to the application. It is widely used (see, for example, Patent Document 1).

The PC pile includes a cylindrical concrete body, a plurality of PC steel materials embedded in the concrete body at intervals in the circumferential direction, and spiral or annular shear reinforcing bars arranged outside the plurality of PC steel materials. It has a high bending strength due to the compressive stress due to prestress acting on the concrete body, and the shear strength is reinforced by the binding force of the shear reinforcing bar.

In this PC pile, a reinforcing bar cage consisting of multiple PC steel materials and shear reinforcing bars is installed in the formwork, concrete is poured into the formwork with the PC steel materials tense, and the concrete body is made by centrifugal compaction. After forming, the concrete body is subjected to pretension type prestress by PC steel material by removing the mold.

The PHC pile is a PC pile made of high-strength concrete having a design standard strength of 80 N / mm ² or more, and has high strength and is hard to crack. Further, as the PHC pile, a so-called JIS reinforced pile having a high shear strength with a dense pitch of shear reinforcing bars is also known.

The PRC pile is a PC pile or a PHC pile in which deformed reinforcing bars and flat steel are arranged between PC steel materials in the concrete, and has high toughness.

Further, as other ready-made piles, an outer shell steel pipe concrete pile (hereinafter referred to as SC pile) formed by forming a tubular concrete body in the outer shell steel pipe by centrifugal compaction is also known (for example, Patent Document). 2).

Japanese Unexamined Patent Publication No. 6-299549 Japanese Unexamined Patent Publication No. 6-220842

However, the conventional PC piles, PHC piles and PRC piles as described above have a structure in which a shear reinforcing bar is provided inside the concrete, and a concrete cover having a certain thickness is required outside the shear reinforcing bar. There was a problem that it was difficult for the shear reinforcing bar to work effectively in the portion.

Further, when the pitch of the shear reinforcing bars is made dense like the JIS reinforced pile, there is a problem that it takes time and effort to form the shear reinforcing bars, the number of materials used increases, and the manufacturing cost increases.

On the other hand, in the conventional SC pile, bending reinforcement and shear reinforcement are performed by the outer shell steel pipe arranged outside the concrete body, so the thickness of the outer shell steel pipe is determined by the bending strength and is excessive with respect to the shear stress. I had no choice but to become.

In addition, the outer shell steel pipe used for SC piles has a certain thickness in order to obtain a predetermined bending strength, and in many cases it is externally produced because special equipment is required for its production. There was a problem that integrated production was difficult.

Therefore, in view of such conventional problems, the present invention has been made for the purpose of providing a shear-reinforced PC pile having excellent productivity, a simple structure, and a high shear strength.

The feature of the invention according to claim 1 for solving the above-mentioned conventional problems includes a tubular concrete body and a plurality of PC steel materials embedded in the concrete body at intervals in the circumferential direction. , at a shear reinforcement PC pile prestress by the PC steel material has been introduced, and Kuijiku direction of deformed bar or flat bar between the PC steel and one or more shear reinforcing steel that restrains the outer periphery of said concrete body The shear reinforced steel pipe is made of a thin steel plate.

The feature of the invention according to claim 2 is that, in addition to the configuration of claim 1, the thin-walled steel sheet corrodes to the square root of {(0.5 to 1.6) × pile outer diameter / yield strength of the thin-walled steel sheet}. The thickness is due to the addition of the allowance.

The feature of the invention according to claim 3 is that, in addition to the configuration of claim 1 or 2, end fittings and the shear reinforced steel pipe arranged between adjacent shear reinforced steel pipes in the pile axis direction or at the end of the concrete body. There is a tension between and.

The shear-reinforced PC pile according to the present invention has the configuration according to claim 1, and thus, like the conventional PC pile, PHC pile and PRC pile, the bending stress acting on the pile due to the introduction of prestress by the PC steel material. By restraining the concrete body with a shear reinforced steel pipe, it is possible to counter the shear stress acting on the pile with a simple structure. Further, since the shear reinforced steel pipe is arranged on the outside of the concrete body, the toughness improving effect is also high. Furthermore, since the thin-walled steel sheets that make up the shear-reinforced steel pipe are thin and have excellent workability, the shear-reinforced steel pipe can be manufactured without using special equipment, and the work from the production of the shear-reinforced steel pipe to the completion of the pile can be performed at the pile manufacturing plant. It can be performed consistently, and the manufacturing cost can be reduced. In addition, the structure can be made to correspond to the conventional PRC pile, and high toughness can be ensured.

Further, in the present invention, by providing the configuration according to claim 2, the shear stress can be suitably countered by the shear reinforced steel pipe made of a thin steel plate.

Further, in the present invention, by providing the configuration according to claim 3, the shear reinforced steel pipe does not hinder the compression of the concrete body, and prestress can be suitably introduced.

It is a partial fracture front view which shows an example of the shear reinforcement PC pile which concerns on this invention. It is a cross-sectional view taken along the line AA of the same as above. It is a partial fracture front view which shows another example of the shear reinforcement PC pile which concerns on this invention.

Next, an embodiment of the shear-reinforced PC pile according to the present invention will be described based on the examples shown in FIGS. 1 to 3. Reference numeral 1 in the drawing is a shear-reinforced PC pile.

As shown in FIGS. 1 and 2, the shear-reinforced PC pile 1 includes a tubular concrete body 2, a plurality of PC steel materials 3, 3 ... Buried in the concrete body 2 at intervals in the circumferential direction, and concrete. A shear-reinforced steel pipe 4 for restraining the outer periphery of the body 2 is provided, and prestress is introduced into the concrete body 2 by PC steel materials 3, 3 ....

The concrete body 2 is formed in a cylindrical shape having a hollow portion 21 in the center by high-strength concrete having a compressive strength of 80 N / mm ² or more, and each PC steel material 3, 3 ... Is embedded in the thick portion thereof in a tense state. ing.

Further, the end metal fittings 5, 5 are fixed to both ends in the axial direction of the concrete body 2, and the ends of the PC steel materials 3, 3 ... Are fixed to the end metal fittings 5, 5.

The end metal fittings 5 and 5 include a tubular reinforcing cylinder portion 51 fitted to the end portion of the concrete body 2 and an annular plate-shaped end plate 52 fixed to one opening of the reinforcing cylinder portion 51. The end portions of the PC steel materials 3, 3 ... Are fixed to the end plate 52.

The PC steel materials 3, 3 ... Are formed in a round steel shape, for example, and both ends thereof are fixed to the end plates 52 in a tense state, and prestress in the compression direction is applied to the concrete body 2. The PC steel materials 3, 3 ... Are not limited to the round steel shape, and may be, for example, a PC steel stranded wire or a deformed steel rod.

The shear-reinforced steel pipe 4 is formed in a cylindrical shape with a thin-walled steel plate made of rolled steel for welding (SM400 steel plate) or the like, adheres to the outer peripheral surface of the concrete body 2, and restrains the concrete body 2 in the radial direction. ..

The thickness T of the thin-walled steel sheet is determined according to the shearing force acting on the pile, and is preferably set in the following range.
T = {√ (0.5 d / σ _y ) to √ (1.6 d / σ _y )} + (corrosion allowance of steel pipe)
In addition, T is the required thickness (mm) of the shear reinforced steel pipe 4, d is the outer diameter of the pile (mm), and σ _y is the yield strength (N / mm ² ) of the thin-walled steel pipe.

Therefore, the thickness of the thin steel plate used for the shear reinforced steel pipe 4 secures a shear strength equal to or higher than that of the JIS reinforced pile (ρs · σ _{y ′} ≧ 2.45), for example, assuming that the corrosion allowance is 1.0 mm. Even in this case, a pile having an outer diameter of 300 mm can be set to about 1.6 mm, and a pile having an outer diameter of 1000 mm can be set to about 3.5 mm.

On the other hand, the thickness of the outer shell steel pipe constituting the SC pile is about 4.5 mm to 9 mm for a pile having an outer diameter of 300 mm and about 6 to 19 mm for a pile having an outer diameter of 1000 mm, and the shear-reinforced steel pipe 4 is outside the SC pile. The wall thickness is significantly thinner than that of the shell steel pipe.

Further, the shear reinforcing steel pipe 4 is formed to have a shorter overall length than the concrete body 2, a tension allowance 6 is provided between the end metal fittings 5 and 5 and the shear reinforcing steel pipe 4, and the shear reinforcing steel pipe 4 introduces prestress. It is designed not to interfere with.

As a preliminary preparation, the shear-reinforced PC pile 1 is formed by welding both end edges of a rectangular plate-shaped thin-walled steel plate, adjusting the shape, and forming a cylindrical shape to form a shear-reinforced steel pipe 4.

At that time, unlike the outer shell steel pipe used for SC piles, the shear reinforced steel pipe 4 uses a thin steel plate with a thin plate thickness, so that it is excellent in workability and does not require special equipment for processing. Integrated production at a pile manufacturing plant is possible without depending on.

Next, the shear reinforcing steel pipes 4, PC steels 3, 3 ... And the end members are housed in the formwork with the PC steels 3, 3 ... Passed through the shear reinforcing steel pipes 4, and then the PC steels 3, 3 ... By pulling the end plate 52 on which the ... is fixed by a jack or the like, the PC steel materials 3, 3 ... Are strained.

In that state, a predetermined amount of concrete is put into the formwork with both ends of the PC steel materials 3, 3 ... Supported by each formwork, and the cylindrical concrete body 2 is formed by centrifugal compaction by a centrifugal molding machine. To do.

Then, the necessary curing treatment is performed, the concrete body 2 is solidified, and then the mold is removed, and the tension force of the PC steel materials 3, 3 ... Is applied to the concrete body 2.

At that time, by providing the tension allowance 6 between the end metal fittings 5 and 5 and the shear reinforced steel pipe 4, the shear reinforced steel pipe 4 does not hinder the compression of the concrete body 2 due to the introduction of prestress, and concrete is preferably used. Axial prestress is introduced into the body 2.

The shear-reinforced PC pile 1 configured in this way can resist the bending stress acting on the pile due to the introduction of prestress by the PC steel materials 3, 3 ... Like the conventional PC pile, PHC pile and PRC pile. ..

On the other hand, the shear reinforced PC pile 1 is provided with a shear reinforced steel pipe 4 made of a thin steel plate on the outer periphery of the concrete body 2, and by restraining the concrete body 2, it is possible to counter the shear stress acting on the pile with a simple structure. It has become.

At that time, since the shear reinforcing steel pipe 4 is arranged on the outside of the concrete body 2, the effect acts on the entire concrete body 2 and the toughness improving effect is also high.

Further, in the shear reinforced PC pile 1 according to the present invention, since the thin steel plate constituting the shear reinforced steel pipe 4 is thin and has excellent workability, the shear reinforced steel pipe 4 can be manufactured without relying on special equipment, and the pile can be manufactured. The work from the production of the shear reinforced steel pipe 4 to the completion of the pile can be performed consistently in the factory, and the production cost can be reduced.

As shown in FIG. 3, the shear auxiliary PC pile may be provided with a plurality of shear reinforcing steel pipes 7, 7, ... In the pile axial direction. The same reference numerals are given to the same configurations as in the above-described embodiment, and the description thereof will be omitted.

In this case, the distance L between the shear reinforced steel pipes 7 and 7 may be 1/2 or less of the outer diameter of the pile, but it is desirable that the distance L is about 50 to 100 mm, which is less than the wall thickness of the concrete body 2.

Further, in the above-described embodiment, the structure corresponding to the conventional PC pile or PHC pile has been described, but the shear-reinforced PC pile 1 according to the present invention has a deformed shape in the pile axial direction between the PC steel materials 3, 3 ... It may be provided with reinforcing bars or flat steel.

T Thin-walled steel plate Thickness d Shear outer diameter L Shear reinforcement pipe spacing 1 Shear reinforcement PC pile 2 Concrete body 21 Hollow part 3 PC steel material 4 Shear reinforcement steel pipe 5 End metal fittings 51 Reinforcement cylinder 52 End plate 6 Tension allowance 7 Shear reinforcement steel pipe

Claims (3)

In a shear-reinforced PC pile provided with a tubular concrete body and a plurality of PC steel materials embedded in the concrete body at intervals in the circumferential direction, and prestress is introduced by the PC steel materials.
A deformed reinforcing bar or flat steel in the direction of the pile axis is provided between the PC steel materials, and one or a plurality of shear reinforced steel pipes for restraining the outer periphery of the concrete body , and the shear reinforced steel pipe is made of a thin steel plate. Shear reinforcement PC pile. The shear-reinforced PC pile according to claim 1, wherein the thin-walled steel plate has a plate thickness obtained by adding a corrosion allowance to the square root of {(0.5 to 1.6) x pile outer diameter / yield strength of the thin-walled steel plate}. The shear reinforcement according to claim 1 or 2, wherein a tension allowance is provided between the shear reinforcing steel pipes adjacent to each other in the pile axis direction or between the end metal fittings arranged at the end of the concrete body and the shear reinforcing steel pipe. PC pile.

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