JPS621311Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a prestressed concrete pile whose purpose is to prevent a decrease in stress in a portion close to the fractured portion when one end of the pile is fractured.

Conventionally, concrete is poured by applying the required tensile force to PC steel materials such as PC steel rods, PC steel wires, and stranded PC steel wires, and after the concrete has hardened, the tensile force on the PC steel materials is released and the hardened concrete is pre-filled. Prestressed concrete piles manufactured by a pretension method that introduces stress have superior strength characteristics compared to other ready-made concrete piles (that do not introduce prestress).

However, in the foundation work using the prestressed concrete piles mentioned above, in order to integrate the prestressed concrete piles and the foundation footing, the concrete pile head portion of the prestressed concrete piles is suspended by about 1 m and the main reinforcement of the prestressed concrete piles is removed. It is common to use a pile head processing method in which PC steel is extracted and used as anchorage for the foundation footing. However, at this time, by peeling off the concrete part of the pile head, the adhesion between the PC steel material and the concrete comes off and the prestress is released, which reduces the bending resistance and shear of the concrete part near the pile head treatment area. It had the disadvantage of having strength problems such as a significant decrease in resistance.

However, in this invention, a steel wire is spirally wound around the PC steel material and fixed, and slits are provided at a predetermined interval on the side edge of the steel wire that does not contact the PC steel material, so that the contact between the PC steel material and the concrete is prevented. The adhesion force is strengthened, and when the concrete pile head part is crushed, the stress caused by the PC steel material is difficult to be released from the concrete end adjacent to it, thus solving the above-mentioned conventional problems.

This invention will be explained below based on embodiments shown in the drawings. A plurality of PC twisted wires 1 are appropriately arranged as a PC steel material (Fig. 2), and both ends 1a,
Concrete 2 is poured with a predetermined tensile force applied to the PC strands 1 pulled between 1b and 1b, and after the concrete 2 is cured, the tensile force on the PC strands 1 is released and prestress is introduced into the concrete 2, thereby prestressing. This constitutes a concrete pile 3. A steel tape 4 having a square cross section is spirally wound around the peripheral wall of the PC stranded wire 1 on the side of the pile head 3a over an appropriate length L (straight line distance) from the head 1a of the PC stranded wire 1. The twisted wire 1 and the steel tape 4 are fixed together with an epoxy adhesive.
The steel tape 4 has slits 4b formed at a predetermined interval on the side edge of the steel tape 4 that does not come into contact with the PC strands 1.

In the above, the winding length of the steel tape 4 must be such a length (for example, 1 m) that there is no risk that the adhesion between the PC strands 1 and the concrete 2 will come off when the concrete 2 is lifted off the pile head 3a. , the PC strands 1 may be wound over the entire length as required. Also steel tape 4
The spiral pitch P is appropriately selected in consideration of the slippage (movement toward the contraction side relative to the concrete 2) that differs depending on the type of PC steel material.
Incidentally, the angle of inclination θ between the bearing surface 4a of the steel tape 4 and the central axis of the PC twisted wire 1 should not be set too small.

According to the above embodiment, even when the concrete portion of the pile head is lifted off after burying the prestressed concrete pile 3, the adhesion between the PC strands 1 and the concrete 3 is strong, so the PC strands 1 do not slide down and stress is reduced. There is no risk of it being canceled. Also, steel tape 4 is attached to all strands 1.
Although the wires are wrapped and fixed, it is not necessary to wrap them all around, for example, it may be wrapped around every other wire.

FIG. 4 shows another embodiment of the PC steel material used in the prestressed concrete pile of this invention. A large number of slits 7 are provided at equal intervals on the outer edge of the steel tape 6. If this steel material is used, the slit 7 and the concrete will be hooked together, resulting in a large adhesion force, especially in the direction of rotation.
is obtained.

In addition to PC stranded wire and PC steel wire, PC steel bars can also be used as the PC steel material.
It is also possible to use a deformed PC steel rod and caulk it by fitting a steel tape having a thickness greater than the depth of the spiral groove into the spiral groove.

That is, according to this invention, a steel wire is spirally wound and fixed to the PC steel material buried in prestressed concrete, and slits are provided at a predetermined interval on the side edge of the steel wire that does not contact the PC steel material. If the pile cap concrete is removed in this area, even if the adhesion between the PC steel material and the concrete in the vicinity of the pile cap treatment peels off, the steel wire will prevent the PC steel material from moving toward the contraction side relative to the concrete. This can be reliably prevented by the bearing surface, and the release of prestress can be effectively prevented. Thereby, it is possible to avoid deterioration in strength such as bending resistance and shear resistance of the concrete portion near the pile head processing portion.

Moreover, since the steel wire is wound and fixed in a spiral, its bearing surface is located continuously in the concrete, making it possible to minimize the release of prestress no matter where the concrete is removed. This makes it possible to change the length of the concrete pile head and to absorb slight deviations in the length, making it highly versatile and It has advantages such as easier turning.

[Brief explanation of the drawing]

Fig. 1 is a partially cutaway front view of the embodiment of this invention, Fig. 2 is a front view of the reinforcing state, Fig. 3 is an enlarged front view of the steel wire winding section, and Fig. 4 is the same steel wire winding section. FIG. 7 is an enlarged front view showing another embodiment of the wire winding section. 1...PC stranded wire, 2...concrete, 3...
Prestressed concrete pile, 4, 6...Steel tape, 5...PC pile line, 7...Slit.

Claims (1)

[Claims for Utility Model Registration] 1. A concrete pile in which stress is introduced using PC steel material, in which a steel wire is spirally wound and fixed to the peripheral wall of the PC steel material, and the steel wire is attached to the PC steel material. A prestressed concrete pile characterized in that slits are provided at predetermined intervals on side edges that do not touch each other. 2. The prestressed concrete pile according to claim 1, in which the steel wire is a steel tape with a square cross section. 3. The prestressed concrete pile according to claim 1 or 2 of the utility model registration claim, in which the PC steel material is partially or entirely wrapped with steel wire.