JPS59114322A - High-strength concrete pile - Google Patents

Abstract

PURPOSE:To prevent the corrosion of steel bars, etc., by providing a rust-proof ductile protective material to the outside surface of a pile consisting of an iron bar cage composed of a high-tensile steel bar and a spiral steel bar and a high-tensile steel bar into which a prestress is introduced toward the core side rather than the iron bar cage. CONSTITUTION:A high-strength concrete pile is composed of a high-strength concrete 1, a high-tensile steel bar 2, a spiral iron bar 4, a high-tensile steel bar 3, a rust-proof ductile protective material 5, and an end plate 4. The concrete 1 is an expanded concrete having a compressive strength of about 800kg/cm<2> or more, and an iron bar cage is formed of the steel bar 2 and the spiral iron bar 4. The steel bar 3 is used for introducing a prestress into the pile body and set on the core side rather than the iron bar cage. The protective material 5 is made of polyethylene sheet. Since the ground is isolated from the spiral iron bar 4 and the steel bars 2 and 3 by the protective material 5, these parts 2-4 can thus be prevented from corrosion.

Description

[Detailed description of the invention] The present invention relates to high strength concrete piles.

In particular, it greatly improves performance when axial force and bending are applied simultaneously, and at the same time reduces groundwater in the ground where piles are installed.
It prevents corrosion of high-tensile steel bars and reinforcing bars and erosion of concrete in gas and acidic soils.

Conventional ready-made concrete piles include the following types, but each of these has its own merits and demerits, and as seismic performance is increasingly required, various shortcomings are becoming a problem.

(1) Reinforced concrete pile (hereinafter abbreviated as RC pile) Since the tensile strength of concrete is originally low, cracks easily occur during handling of the pile product or due to external forces such as ground expansion force after construction.

This single crack will not completely close even if no external force is applied.As a result, the allowable stress of concrete and reinforcing bars is low (suppressed), and the mechanical properties of the pile structure are low. The reliability of foundation designers is also low.

(2) Prestressed concrete pile (hereinafter referred to as PC)
Abbreviated as pile. ) Since the tensile strength of concrete is supplemented by prestressing, cracks are less likely to occur, but when bending loads, especially bending loads and axial forces are applied simultaneously, the increase in curvature from cracking to final failure is small. The process leading to destruction is brittle and not of the preferred 11: quality.

When using prestressed members in above-ground structures, even if a crack occurs due to the action of a transient excessive external force, the crack will close due to the prestress, as the transient excessive external force no longer acts. So -11? However, according to the standards for the handling of piles set by the Japan Society of Civil Engineers, the Architectural Institute of Japan, and the Ministry of Construction, cracks may temporarily occur underground where the possibility of corrosion of PC steel bars is high. The disadvantage is that it is not possible.

In addition, in the range where the axial force acting on the PC pile is small, the bending crack strength increases as the number of helices per press increases, and at the same time, the bending crack resistance increases due to the increase in the amount of PC steel rods used that inevitably accompanies an increase in prestress. However, since the combined force of compressive stress due to external force and 71 no stress acts on the concrete, increasing the prestress reduces the bending strength in the range where the axial force acting on the PC pile is large. There are drawbacks.

(3) Reinforced prestressed concrete - 1 to pile (hereinafter referred to as
It is abbreviated as PRC pile. ) A slight prestress is introduced into the RC pile in order to improve the shortcomings of the RC pile, and it is generally recognized as a lower grade of the PC pile.

1) Similar to the case of C-vile, there is a drawback that cracks are not tolerated.

(4) W4 pipe] concrete-1-pile mechanical performance is excellent, but ordinary Rc pile' and PC
From piles; the disadvantages are that they are very expensive and that corrosion of the outer shell pipe must be accounted for.

The present invention aims to eliminate the drawbacks of these piles and provide inexpensive ready-made concrete piles.

Next, one embodiment of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a partially cutaway side view of one embodiment of high-strength concrete 1 to pile of the present invention, and FIG. 2 is a sectional view perpendicular to the axis of FIG. 1. In the drawings, 1 is high-strength concrete with a compressive strength of 800 ko/cv or higher, preferably expansion +11 concrete.

2 is a high-tensile steel bar that forms a reinforcing bar basket together with the spiral reinforcing bar 4, and it is possible to do so (do not apply tension to it).

3 is a high-strength horn steel rod used in a tensioned state to introduce a press into the pile body, and its placement is on the side of pile 8 from the aforementioned reinforcing bar cage, and in a centrifugally formed pile body like this example, , it is desirable to arrange it on the thickness center diameter of the thick-walled cylindrical cross section. Further, as in the case of the high-tensile steel bar 2, a spiral reinforcing bar may be wound around the bar.

5 is a ductile anti-rust protective material. For example, after curing the pile at a high temperature, the outer surface of the stake is still warm, a layer of epoxy or resin is applied to a thickness of 200 μm as a brimer, and then a modified polyethylene resin is applied to a thickness of 100 to 150 μm as an adhesive layer. Poly 1 continuously extruded into a shape
Wrap the tyrene sheet to a thickness of 2mm and 1m.

Reference numeral 6 denotes an end plate at the end of the stake for fixing the high-tensile steel rod 3. Although the high-tensile steel rod 2 does not need to be locked to this end plate 6, it is more desirable that it is locked. It is desirable that the winding pitch of the helical reinforcing bar 4 is small near the end plate 6.

In the pile of the present invention, the ground reinforcement/v reinforcing bars and high-tensile steel bars are completely isolated by the ductile rust prevention protection forest 5, so there is no fear of corrosion of these reinforcing materials, which directly affect the strength of the pile. do not have. In addition, if the outer periphery of the stake is covered with an air-impermeable, water-impermeable, acid-resistant plastic snack material as in the example,
Even if the piles of the present invention are installed in acidic ground, the concrete of the piles will not be eroded.

Even if cracks occur in the body temporarily due to earthquake forces, etc., the anti-rust protection material 5 on the outside is ductile, preventing foreign matter from entering the crack opening.
After the temporary external force such as the seismic force is removed, the crack is completely closed by pressing 1-less. Therefore, under normal conditions, the closing of cracks and the functions of the ductile anti-corrosion protection forest 5 are combined to completely prevent corrosion of the helical reinforcing bars and high-tensile steel bars that affect the mechanical performance of piles. effective.

As is clear from the above explanation, the ductile anti-rust protection material 5 does not necessarily have to be in close contact with the pile body.

In conventional PC piles and PRC piles, the occurrence of cracks is not tolerated, but in the pile of the present invention, cracks that occur temporarily are harmless, and the occurrence of cracks can be tolerated.

Assuming cracks, the axial strength and bending strength of the pile are i
When calculating the value, it has the advantage that the calculated value obtained is highly reliable because it is based on the stress level of the reinforcing bar. On the other hand, when the occurrence of cracks is not recognized, the method is based on the uncertain tensile strength or bending strength of the concrete, which has the disadvantage of having to multiply the tensile strength or bending strength of the concrete by a large safety factor.

(The mechanical performance is determined by plotting the fracture bending moment Mu at a predetermined axial force N on the orthogonal coordinates consisting of axial force and moment, with the axial force N as a variable.
Evaluation using a correlation curve or an allowable N-Ma phase closed curve (Ma indicates the maximum allowable bending moment 1 or more when the predetermined axial force N is applied), which includes a certain safety factor, e.g. 1.75, in the N-Mu correlation curve. can do. From now on, the mechanics of the stake 1! To increase the capacity, N-ML at the time of destruction.
It is important to make the value of each point of the I correlation curver as large as possible. However, for conventional I)C piles and PRC piles, there are limitations regarding the tensile strength and bending strength of concrete, so expanding the N-M11 correlation curve at failure is equivalent to expanding the allowable N-Ma correlation curve. It doesn't lead to.

In the pile of the present invention, by using the ductile anti-rust protection forest 5, it is possible to arrange the high tensile strength steel rod 2 near the surface layer of the pile. By the way, the bending fracture strength of piles is normally proportional to the square of the distance from the pile core to the reinforcing material, so the pile bending fracture strength of the present invention is higher than that of conventional PC piles and PRC piles If the total amount of rods used is the same, the yield strength will be extremely large. In addition, the prestress of the pile of the present invention is suppressed to such an extent that no cracks occur during handling of the pile, or to such an extent that once opened cracks close again. When the force is large, there are four cases where the bending strength decreases or the pile's failure mode becomes brittle. Conventional type 0 (Press 1 to Resume 100/Cv) PC pile with an outer diameter of 500ml and the pile of the present invention (same use of high-tensile steel rods, prestress amount 50k!)/C
'In2, cover thickness of high tensile steel bar 2 9mm) allowable N-
The Ma correlation curve is as shown in FIG. According to this, it is clear that the mechanical properties of the pile of the present invention are excellent. Placing the high-tensile steel rod 3 for introducing prestress as far away from the surface of the concrete molded body as possible has the effect of preventing rust from occurring. By wrapping the helical reinforcing bar 4 around the high-tensile steel bar 3 for introducing prestress (although it may be possible to wrap it as little as possible), it is possible to avoid the negative effects of spot welding between the high-tensile steel bar 3 and the helical reinforcing bar, i.e. It is possible to reduce the possibility of breakage of a steel bar that is constantly under high tension due to accelerated corrosion caused by welding, a decrease in cyclic fatigue strength, a decrease in elongation ability, etc.

In addition, because the high-tensile steel bars 2 and 3 are arranged at different positions, it is not necessary to set the fixing holes for the high-tensile horn steel bars on the end plate of the pile on the same line. This has the effect of reducing stress and lowering the manufacturing boss of the end plate.

Piles are generally joined by welding the outer periphery of the end plates of the pegs, but since the part where the high-tensile steel bar 2 is attached to the end plate is close to the welded part of the peg joint, When a bending moment is applied, the force is transmitted very smoothly, which also has the effect of improving joint performance.

When spiral reinforcing bars 4 are used extensively, the toughness is very high (1
However, the effect only affects the part of the pile body surrounded by the spiral reinforcing bar. In the present invention, since the helical reinforcing bars 4 are arranged close to the outer periphery of the pile body, the toughness of the pile is 1!1.
can be effectively increased.

When installing piles, it is often necessary to remove unnecessary pile parts, but since the reinforcing bars are installed close to the outside surface of the pile, cutting the piles is much easier. Become.

When using a high-tensile steel bar like the high-tensile steel bar 2 of the present invention as a tensile reinforcing shrine, there is a risk of poor adhesion between the steel cup and the concrete at the end of the steel bar. By spot welding spiral reinforcing bars at a close pitch, the adhesion properties of the steel rod are extremely good.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway view of one embodiment of the high-strength concrete pile of the present invention, Fig. 2 is a sectional view taken along the line A-△ of Fig. 1, and Fig.
The figure shows the allowable axial force between the pile of the present invention and the conventional pile.
It is a diagram of bending moment. 1 is concrete, 2.3 is a high-tensile steel bar, 4 is a spiral reinforcing bar, 5 is a ductile rust-preventing protective material, and 6 is an end plate. Patent applicant: Ube Industries, Ltd.

Claims (1)

[Claims] The high-tensile steel bars of the reinforcing bar cage, which is formed by high-tensile steel bars and helical reinforcing bars arranged parallel to the pile axis direction, are placed on the outer surface of the pile, and the high-tensile steel bars are placed at a higher position than the high-tensile steel rods. This high-strength concrete pile is characterized in that a ductile anti-corrosion protection forest 5 is attached to the outer surface of a concrete pile formed body in which prestress is introduced by tensioning high-tensile steel rods placed on the 8 sides.