JPH04249109A - Manufacture of pc pile having ultrahigh bending toughness - Google Patents

Abstract

PURPOSE:To provide a method with good workability for manufacturing a PC pile having ultrahigh bending toughness, which has a high yield strength against failure in bending and high plastic deformability. CONSTITUTION:In a cylindrical formwork 14 for centrifugal molding, cross- binding-bar supporting bars 12 are so disposed as to be formed into a cylindrical shape via spacers with respect to the inner face of the formwork, and a spiral cross binding bar 11 is held inside the supporting bars 12 and stretched throughout the entire length of the formwork 14. PC steel bars 10 are inserted inside the cross binding bar 11, and the supporting bars 12 and the PC steel bars 10 are secured to tension bearing fittings 17, 18. Thereupon, the tension bearing fitting 18 on one side is pulled by a jack to be tensioned. Concrete is cast into the formwork 14 to make a cylindrical concrete pile by a method of centrifugal molding, and the tension bearing fittings are removed from the PC steel bars 10 and the supporting bars 12 to introduce prestress into the concrete pile.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing ultra-high bending toughness PC piles for use in civil engineering and building foundations.

0002

[Prior Art] Conventionally, the production of prestressed concrete piles, in which prestressed concrete piles are made by burying prestressed steel in the vertical direction and prestressed in the vertical direction, have been carried out using cylindrical formwork, which is hollowed out by centrifugal force. Centrifugal molding is commonly used to form cylindrical shapes.

[0003] This conventional method will be explained with reference to FIG. 6. First, a group of longitudinal reinforcements consisting of PC steel wires 1, 1, . The hoop muscle 2 is wound spirally or in a large number of rings and welded to form a cylindrical cage (FIG. 6A). With the upper half of the cylindrical formwork 3 cut in half removed, insert it into the lower half, and insert each PC steel wire 1, 1
... is passed through the end iron plate (commonly known as "Hakama") 4 and fixed to the tension bearing fitting 5 (Fig. 6B).

After filling a predetermined amount of concrete 6 in this state, the upper half of the cylindrical formwork 3 is covered and fixed, and one of the tension bearing fittings 5 is pulled with a jack to apply a predetermined tension to the PC steel wire. is applied, and the reaction force is supported by both ends of the cylindrical formwork 3 (FIG. 6C). In addition, before filling the concrete 6, cover and fix the upper half of the cylindrical form 3, pull the tension bearing fitting 5 with a jack, apply a predetermined tension to the PC steel wire, and then fill the concrete with a pump. do.

In this state, the cylindrical form 3 is placed on the rotating roller 7 of a centrifugal forming machine and rotated, and the centrifugal force forms the concrete 6 into a cylindrical shape along the inner surface of the form (FIG. 6D).
After curing in a temperature-controlled curing chamber using steam or the like, the tension bearing fittings 5 are removed and the tension is released to introduce prestress into the concrete.

[0006] Conventional PC piles manufactured in this manner have increased bending fracture strength by increasing the prestress introduced, but in order to increase seismic resistance during earthquakes,
It is important to increase the plastic deformation capacity at the same time as increasing the bending fracture strength, and there has been a problem in that increasing the prestress reduces the plastic deformation capacity and actually reduces the seismic performance.

In view of these problems, the inventor of the present invention buried spiral horizontal restraint bars between the cylindrical vertical reinforcing bars and the outer peripheral surface of the pile in order to improve seismic performance. By using longitudinal reinforcement groups with a high ratio, we have developed an ultra-high bending toughness PC pile that has a large bending fracture strength and a large plastic deformation capacity (Japanese Patent Application Laid-Open No. 62-280418).

[0008] In the ultra-high bending toughness PC pile as described above, in order to maintain properties such as the yield strength and high uniform elongation rate of the longitudinal reinforcement group, the spot welding used for forming the basket reinforcement is not preferable, and moreover, the horizontal In order to enhance the bending toughness improvement effect of restraint reinforcement, it is necessary to arrange horizontal restraint reinforcement as close to the outer circumferential surface of the pile as possible while keeping it away from the longitudinal reinforcement group. , it was necessary to position it strongly to withstand centrifugal molding.

[0009] Therefore, in order to position the lateral restraint reinforcement within the formwork, the present inventor inserted a lateral restraint reinforcement support wire inside a spiral or ring-shaped lateral restraint reinforcement to form a cage shape, and the support wire We have developed a method for manufacturing ultra-high bending toughness PC piles that are tensioned in formwork (Japanese Patent Application No. 1-143006).

0010

[Problems to be Solved by the Invention] However, in the conventional method described above, the horizontal restraint bars are wound around the outside of the support wire, so unless the horizontal restraint bars and the support wire are firmly fixed around the entire circumference, concrete There was a problem in that the horizontal restraint bars were pushed outward due to centrifugal force during forming, making it impossible to obtain a constant concrete cover from the outer peripheral surface of the pile. For this reason, it is necessary to firmly secure the lateral restraints and support wires at multiple locations using binding, etc.
There was a problem in that the number of man-hours required for this was large, leading to high costs.

In view of these conventional problems, the present invention makes it possible to easily manufacture an ultra-high bending toughness PC pile in which the positioning of the lateral restraining reinforcement is accurate and strong, with less man-hours than in the past. It is intended to provide a method.

0012

[Means for Accomplishing the Object] The gist of the present invention for achieving the above-mentioned objects is to provide a cylindrical formwork with a large number of longitudinal bars made of prestressed steel material directed in the axial direction of the formwork. The two ends of each prestressing steel member are supported by a pair of tension-bearing metal fittings, arranged in a cylindrical shape concentric with the formwork, and located outside of the longitudinal reinforcement group and of the formwork. A plurality of bars for supporting lateral restraint bars are inserted in a cylindrical arrangement between the formwork and the formwork at a position close to the inner surface, and a spiral lateral restraint bar is inserted into the cylindrical inner side of the bar material along the inner surface of the formwork. It is characterized by housing restraint bars, then pulling one of the tension-bearing metal fittings with a jack to apply a predetermined tension force to the group of longitudinal bars, and centrifugally forming the concrete filled inside in this state. The invention consists in a method of manufacturing an ultra-high bending toughness PC pile.

[0013] It is also possible to use a cylindrical cage-shaped rod material in which a rod for supporting the lateral restraint is fixed in advance to the outside of the lateral restraint.Furthermore, the lateral restraint can be formed into a coil spring shape. It may be stretched to a predetermined helical pitch and fixed to a rod for supporting lateral restraints, or a concrete covering layer may be attached to the outer peripheral surface of the rod and the covering layer may be used as a spacer. Furthermore, the bar may be stored in a state in contact with the inner surface of the mold, and after centrifugal molding and demolding, the bar may be removed and the grooves after the removal may be filled.

[0014]

[Function] In this method for manufacturing ultra-high bending toughness PC piles, the bar for supporting lateral restraints is supported on the inner surface of the formwork via spacers, thereby regulating the outer circumferential position of the spiral lateral restraints. Therefore, the bar for supporting the lateral restraints will serve as a spacer that connects the lateral restraints to the formwork.

[0015] In this way, by positioning the transverse restraint reinforcements and tensioning the vertical reinforcements, and performing centrifugal molding with the concrete filled in the formwork, the concrete moves to the inner surface of the formwork to a uniform thickness, and each It is formed into a cylindrical shape with the striations embedded.

[0016]

Embodiments Next, embodiments of the present invention will be described with reference to FIGS. 1 to 5.

FIGS. 3 and 4 show an example of a PC pile manufactured by the method of the present invention. This PC pile has a cylindrical shape, and a vertical reinforcement group 10A in which a large number of PC steel members 10, 10, . A circumferentially oriented lateral restraint bar 11 is embedded in a spiral arrangement near the outer peripheral surface of the PC pile. This lateral restraint muscle 11 has a large number of horizontal restraint muscle support bars 12 arranged in a cylindrical shape in the axial direction on its outer peripheral surface.
, 12... are in contact.

Next, the manufacturing method will be explained. The lateral restraint bars 11 are formed into a coil spring shape with a small pitch using a coil spring manufacturing machine. A PC steel wire is used for the lateral restraint bars 11.

The bar 12 also has an annular horizontal restraint bar 11.
It is used to hold the steel in place and usually uses ordinary reinforcing bars, but various other materials such as other metal materials, reinforced wood, or synthetic resins can also be used.

Then, as shown in FIG. 2, horizontal restraining reinforcements 11 are supported inside the bars 12 and arranged within the formwork 14. At the time of this reinforcement, a required number of concrete spacers 12a are fixed to each bar 12, and spaced from the inner surface of the formwork 14 by a predetermined distance. Also, a vertical reinforcement group 11A consisting of a required number of PC steel members 11, 11, . . . oriented in the axial direction within the horizontal restraining reinforcement 11.
Insert. For example, each PC steel material 11 is cut into a predetermined length in advance, and then male threads 11a are carved at both ends.

After the reinforcements 10, 11 and the bar 12 are housed in the formwork 14, the end iron plates 16 are installed inside the formwork 14 at both ends. After that, both ends of the bar 12 and the PC steel material 11 are inserted into the respective through holes of the pair of tension bearing fittings 17 and 18, and the fixing nuts 11b are screwed into the male screws 11a at both ends of each of the PC steel materials 11 on the outside thereof. fit.

Then, one tension bearing fitting 17 is attached to the formwork 14.
and the other tension bearing fitting 18
is movably inserted into the formwork 14, and the tension rod 19 is connected to the center thereof.The fixing plate 20 is screwed onto the male screw 19a formed outside the rod 19, and the fixing plate 20 (
(shown in FIG. 1) are supported on the ends of the formwork 14.

In this way, the bar material 12 and the PC steel material 11
After installing the coil spring-like lateral restraint bar 11 in a predetermined position,
is stretched to the full distance between the iron plates 16 at both ends to form a predetermined spiral pitch, and a binding wire 2 is attached to each bar 12 at several points.
Fixed by 1.

Next, a jack (not shown) is set at the end of the formwork 14, and one of the tension bearing fittings 18 is pulled through the rod 19 to tension the PC steel material 11 and apply a tensile force for prestressing. give.

After tensioning in this manner, the fixing plate 20 is rotated and moved until its surrounding surface comes into contact with the end face of the formwork 14, and then the tension by the jack is released and the formwork 1
Apply reaction force to the end of 4 and remove the jack.

[0026] Next, the required amount of concrete 22 is filled into the mold 14 using a conventional method, molded into a cylindrical shape using a centrifugal molding machine, and removed from the mold after being subjected to necessary curing treatment.

[0027] In the above-mentioned embodiment, a normal reinforcing bar is used as the bar 12, but a diagonal bar may be used, or a deformed steel bar with an uneven surface may be used. .

As a spacer, as shown in FIG. 5, mortar, cement milk,
Covering layer 1 made of polyester resin or even epoxy resin
2b may be applied as a spacer.

Furthermore, in the above-described embodiment, the transverse restraint bars 11 are stretched within the formwork 14 and fixed to the bars 12; Bar material 1
2 may be fixed to form a cage.

Furthermore, the bar 12 and the horizontal restraining reinforcement are made separable, and the bar 12 is placed in contact with the mold bar, and after pouring concrete and removing the mold, the bar 12 is placed on the pile surface. The exposed bar 12 may be removed and the groove after the removal may be filled with mortar.

[0031]

[Effects of the Invention] As mentioned above, the ultra-high bending toughness PC of the present invention
In the method of manufacturing piles, horizontal restraint bars are placed near the surface of the pile in a circumferential direction, and spiral lateral restraints are placed inside a cylindrical bar with the axially oriented PC steel members oriented in the same direction. By supporting the bars, the bar material plays the role of a continuous spacer for the formwork, and even if the transverse restraint bars and the bars are not fixed, the transverse restraint bars will not bulge in the outer circumferential direction during centrifugal molding. Therefore, there is no need to fix bars and horizontal restraint bars at multiple locations as in the past to create a complete cage bar state, and it is possible to manufacture high-performance PC piles with good workability. This is what became.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing a state after completion of molding within a mold.

FIG. 2 is a sectional view showing a reinforcing step in the formwork.

FIG. 3 is a longitudinal cross-sectional view of an example of a PC pile manufactured by the method of the present invention.

FIG. 4 is a sectional view taken along line AA in FIG. 1.

FIG. 5 is a longitudinal cross-sectional view of another example of a PC pile manufactured by the method of the present invention.

FIG. 6 is a cross-sectional view showing steps of a conventional manufacturing method.

[Explanation of symbols]

10 PC steel material 10a Male thread 10b Nut 11 Lateral restraint muscle 12 Bar material 12a Spacer 12b Coating layer (spacer) 13 Hoop muscle 14 Formwork 16 End iron plate 17, 18 Tension bearing fittings 19 Rod 20 Fixer plate 21　Tie wire 22 Concrete

Claims (5)

[Claims] [Claim 1] A group of longitudinal reinforcements made of a large number of prestressing steel materials are inserted into a cylindrical formwork in the axial direction, and both ends of each of the prestressing steel materials are supported by a pair of tension-bearing metal fittings. , a plurality of horizontal restraint reinforcement rods arranged in a cylindrical shape concentric with the formwork, and located outside the longitudinal reinforcement group and close to the inner surface of the formwork, and between the formwork and the support rods; inserting the bars into a cylindrical arrangement, accommodating a spiral lateral restraint along the inner surface of the formwork inside the cylindrical shape of the bars, and then pulling one of the tension bearing fittings with a jack; A method for manufacturing an ultra-high bending toughness PC pile, characterized in that a predetermined tension is applied to the group of longitudinal reinforcements, and in this state, the concrete filled inside is centrifugally formed. 2. The method for manufacturing an ultra-high bending toughness PC pile according to claim 1, wherein a bar for supporting the lateral restraint is fixed in advance to the outside of the lateral restraint and is shaped into a cylindrical cage. 3. The ultra-high bending toughness PC according to claim 1 or 2, wherein the lateral restraint muscle is formed into a coil spring shape, stretched to a predetermined helical pitch, and fixed to a bar for supporting the lateral restraint muscle.
Method of manufacturing piles. 4. The method for manufacturing an ultra-high bending toughness PC pile according to claim 1, wherein a concrete covering layer is attached to the outer peripheral surface of the bar, and the covering layer serves as a spacer. 5. The ultra-high mold according to claim 1, wherein the bar is housed in a state in contact with the inner surface of the mold, and after centrifugal molding and demolding, the bar is removed and the groove after the removal is filled. A method for manufacturing a bend-tough PC pile.