JP2002242126A - Columnar structure and construction method therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technology of using a prestressing steel strand, into which a long object can be easily inserted, as a main reinforcement of a columnar structure in place of a reinforcing bar requiring a joint. SOLUTION: Precast concrete blocks 3 are temporarily coupled together to be piled up on a footing 2, and grout 7 is infilled into a sheath 4 within the footing 2 and the concrete blocks 3. After that, the prestressing steel strand 5, onto which a binding grip 6 is crimped, is inserted into the footing 2 and the respective concrete blocks 3 so as to form the main reinforcement and construct the columnar structure.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a columnar structure and a method for constructing the same.

[0002]

2. Description of the Related Art Conventionally, a reinforcing bar has been used as a main bar of a precast member. Reinforcing bars are limited to a maximum length of 12 m due to transportation reasons. To use them as long reinforcing bars, measures such as connecting them with mechanical joints on site or connecting them by pressure welding are required. It is. Therefore, a long reinforcing bar requires labor such as man-hours and time for connection. Further, in order to insert a long reinforcing bar into a columnar concrete structure, a heavy machine such as a crane having a long stroke capable of lifting a long material and a work space for the crane are required.

[0003]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a technique which overcomes the difficulty caused by using the above-described reinforcing bar as a main bar of a columnar structure.

[0004]

According to the present invention, there is provided a columnar structure characterized in that a PC steel stranded wire is used as a vertical main reinforcing bar, and a crimping grip crimped to the PC steel stranded wire is present in the footing and in each precast block. It is. By using a high-strength PC steel stranded wire that can be continuously conveyed by a coil as a reinforcing bar, a connecting joint of the reinforcing bar becomes unnecessary.
There is no need for a long body truck for transportation, and a normal truck is sufficient. It is possible to insert the reinforcing bar into the columnar structure without using any heavy equipment and with a simple device or human power. The space required for insertion can be reduced to a small space. However, PC steel strands have a different adhesion mechanism to concrete than rebar, and because of adhesion not by bearing pressure but by friction, the adhesion strength is low, and the problem is that the adhesion breaks immediately upon receiving a tensile load. There is. Therefore, it is necessary to install and fix the fixing parts at both ends of the PC steel strand. In addition, since it is in an unbonded state in concrete, the deformation tends to increase.

According to the present invention, in order to improve the adhesion of the strand of PC steel, a crimping grip is crimped at a certain interval in the middle of the strand of PC steel so that the adhesion is caused by the bearing of the crimping grip. The same adhesion function as described above was performed.

In such a columnar structure, if a plastic hinge section is provided between the crimping grip in the footing and the crimping grip in the lowermost precast block, the elongation of this portion absorbs displacement due to an earthquake load or the like, The structure is rich in toughness. For this purpose, it is advantageous to arrange the crimping grip so that the plastic hinge section is as long as possible. Here, the plastic hinge section is a portion where the steel material yields and transmits a certain bending moment.

[0007] When a PC steel strand is used as a main reinforcing bar in place of a reinforcing bar, the bonding strength between the PC steel strand and concrete or mortar is small, and when the main reinforcing bar is subjected to a tensile load, the bond breaks and the unbonded section expands. I do. As a result, in the case of a bridge pier, pullout of the stranded wire from the footing and reduction in strain are caused, thereby lowering the tensile resistance.

[0008] For a pier, a design method is employed in which a crack is induced at a base portion of the pier due to an earthquake load or the like at a specific position to specify a fracture location. Therefore, the length of the plastic hinge section is adjusted by installing a crimping grip across the crack induction point (joint near the base in the case of a columnar structure made of precast concrete) and adjusting the interval. As a result, the deformation performance of the pier can be improved. That is, when the interval between the crimping grips is increased and the length of the plastic hinge section is increased, the allowable value of the elongation of the main bar at that portion increases, and the deformation performance also improves.

The construction of the above structure can be achieved as follows. In building the columnar structure by stacking the precast concrete blocks, the concrete blocks are stacked on the footing, temporarily bonded, and the footing and the sheath in the concrete block are filled with grout, and then the inside of the footing and inside each precast block. The main reinforcing steel is formed by inserting a PC steel stranded wire having a crimping grip crimped so as to be positioned in the sheath into the sheath. At this time, if the distance between the crimping grip in the footing and the crimping grip in the lowermost block is made as large as possible, the deformability of the columnar structure can be increased.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention is to improve the performance of adhering to concrete or mortar by pressing a crimping grip on a PC steel stranded wire at a position having a predetermined interval. P
By using the C steel strand as the main reinforcement, the connection of the main reinforcement by the joint can be omitted, continuity can be ensured, and economical and workability can be improved. The applicable structure can be applied to a cast-in-place structure, and can be applied to a precast structure and the like. And
There is an excellent characteristic that the length of the plastic hinge section can be adjusted by adjusting the interval between the pressure grips.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic longitudinal sectional view of a columnar structure 1 according to an embodiment. The left half of FIG. 1 shows a plastic hinge section 11 having a relatively short length, and the right half of FIG.
Shows a longer version. A precast concrete block 3 is stacked on the footing 2, a main reinforcing bar made of a PC stranded wire is arranged in a vertical sheath 4, and a crimping grip 6 is attached to an intermediate portion of the PC stranded wire 5. . The crimping grip 6 is attached so as to be present in the footing 2 and the block 3 respectively. The PC steel stranded wire 5 is adhered to concrete or mortar by the supporting mechanism of the crimping grip 6, and has a structure for preventing the PC steel stranded wire from being pulled out from the footing 2 and lowering the tensile resistance. As a result, it can be expected that the PC steel stranded wire 5 acts as a main reinforcing bar in the same manner as a reinforcing bar up to its holding strength. The operation of crimping the crimp grip 6 to the PC stranded wire 5 can be easily performed on site. As shown in the right half of FIG. 1, if the plastic hinge section 11 is made longer, the plastic hinge section (unbond section) 11
Even if a crack 12 is generated at the base of the columnar structure due to the earthquake, the strand 5 of the PC steel is restored, and the crack 12 is repaired.

After the mortar (grout 7) is injected into the sheath 4, the PC steel stranded wire 5 is inserted into the sheath 4 from above the columnar structure by inserting the PC steel stranded wire 5 to which the crimping grip 6 is crimped. .

A model similar to the columnar structure shown in FIG. 1 was prepared, and a PC steel stranded wire having a crimping grip mounted in a footing was inserted from above into a sheath filled with grout, and after curing, the PC steel wire was moved upward. After performing a tensile test to pull out
The result that the pull-out force was increased to the tensile strength of the PC steel strand without causing the pull-out of the strand from the PC steel was obtained,
The excellent performance of the present invention has been confirmed.

[0014]

According to the present invention, a high-strength PC steel stranded wire can be used as a vertical main reinforcing bar of a columnar structure in the same manner as a reinforcing bar. (A) The yield strength of the precast structure itself is increased. b) PC steel strands have large elongation and do not yield, improving restoration performance. (c) Even if a crack occurs in an earthquake of seismic intensity level, after unloading, the PC strand strands return and crack. Is repaired. (D) Because of the high strength, the number of main rebars is reduced compared to rebar,
Extra space is available and the cross section of the columnar structure can be reduced. (E) Excellent effects such as the ability to effectively utilize the performance of high-strength concrete and simplifying the construction to improve economic efficiency. To play.

[Brief description of the drawings]

FIG. 1 is a schematic longitudinal sectional view of a columnar structure of an embodiment.
The left half shows an example in which a normal plastic hinge section is provided, and the right half shows an example in which the plastic hinge section is lengthened.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Column-shaped structure 2 Footing 3 Precast block 4 Sheath 5 PC steel strand 6 Crimp grip 7 Grout 8 Joint 11 Plastic hinge section (unbond section) 12 Crack

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masahiro Nakai 3-4-1 Marunouchi, Chiyoda-ku, Tokyo PS Co., Ltd. (72) Inventor Kazutoshi Okuyama 3-4-1 Marunouchi, Chiyoda-ku, Tokyo Issued by PS Co., Ltd. (72) Shouichi Ino, Inventor 3-4-1 Marunouchi, Chiyoda-ku, Tokyo PS Co., Ltd. (72) Inventor: Kazuyoshi Tsuda 5-33, Shimbashi, Minato-ku, Tokyo No. 11 Inside Nippon Huam Co., Ltd. (72) Inventor Junji Umeda 1-16-6 Kita Otsuka, Toshima-ku, Tokyo Dope Construction Industry Co., Ltd. F-term (reference) 2D059 AA03 CC01 2E163 FA02 FD21 FD25 FD44

Claims (4)

[Claims] 1. A columnar structure wherein a PC steel stranded wire is used as a vertical main bar, and a crimp grip crimped to the PC steel stranded wire is present in the footing and in each precast block. 2. The columnar structure according to claim 1, wherein a plastic hinge section is provided between the crimping grip in the footing and the crimping grip in the lowermost precast block. 3. When precast concrete blocks are stacked to form a columnar structure, the concrete blocks are stacked on a footing, temporarily joined, and the footing and the sheath in the concrete block are filled with grout and then footed. A method of constructing a columnar structure, comprising: inserting a PC steel stranded wire having a crimping grip crimped therein so as to be positioned in each precast block to form a main reinforcing bar in the sheath. 4. The method for constructing a columnar structure according to claim 3, wherein the distance between the crimping grip in the footing and the crimping grip in the lowermost block is made as large as possible.