JP2001279614A - Method for jointing precast concrete blocks - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the need of long reinforcements and a long boom crane by stacking precast blocks having main reinforcement inserting hole formed therein, inserting filler and reinforcement in the inserting holes, and improving the technique for connecting the precast blocks to each other through the reinforcement and filler. SOLUTION: Precast concrete blocks 11 having PC strand insert holes communicating with each other formed therein are stacked sequentially on a foundation concrete 12 to construct a columnar structural body 10. A filler hardening with elapse of time is filled into the insert holes 15, the PC strand is unwound from a drum 14 and inserted into the insert holes 15, and filler is fixed so as to connect the stacked blocks 11 to each other.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for joining precast concrete blocks to form a column structure by stacking the blocks, and more particularly, to a long bridge pier, a tubular structure, and a tower structure. The present invention relates to an overall joining method for connecting stacked precast concrete blocks used for objects or pillars.

[0002]

2. Description of the Related Art Concrete structures are designed to reduce the number of skilled workers due to the aging of workers, to reduce the effects of noise, vibration, dust, etc. on the surroundings of construction sites, to increase the strength by reducing the cross-section of structures, Precasting has been promoted in order to satisfy requirements such as improvement of earthquake resistance. One of the most important issues in the precasting of the concrete structure is a joining technique of the precasted members. As a joining technology for precast concrete, PC
Various techniques have been studied and proposed and implemented, such as the technique of introducing prestress using steel, the technique of using mechanical joints of reinforcing bars, and the joining technique of mortar-filled joints. Of these, for the piers, a cylindrical precast concrete block manufactured at the factory is transported to the site, and one end is fixed to the foundation concrete as an example of a joining technology that builds up a pillar frame by stacking and joining the cylindrical blocks on site. There is a technique in which the PC steel material is stacked while introducing prestress as needed at the joints of the blocks. According to this technology, a strong and tough bridge pier can be obtained, but a large prestress is introduced at the joint.
If the joint surface is uneven, cracks due to pre-stress may be a factor in concrete. In order to avoid this, there is a limitation in the manufacturing technology, such as the need to manufacture blocks so that the joining surfaces of the blocks are completely coincident, that is, so-called match cast manufacturing. In addition, this technique had difficulty in mass production.

[0003] As one of means for solving this problem,
There is a technology disclosed in "Civil Engineering Construction Volume 8 No. 8 (Construction of RC Precast Block Type Pier in Construction of 8th Mabuchigawa Bridge on Tohoku Main Line)" and Japanese Patent Application Laid-Open No. 8-4021. The technology is based on stacking precast blocks with a structural reinforcing bar insertion hole that communicates with the entire pier column, up to a predetermined height, and then injecting a filler such as grout or mortar into the reinforcing bar insertion hole, and then uncured. The main rebar is submerged in this filler from the top end of the columnar part in the filler,
This is a technique in which the filler is cured and the precast block is connected via the filler by the main reinforcing bar.

According to this technique, a main structural reinforcing bar is provided so as to penetrate the joint surface between the blocks, and the shear strength is satisfied.
Cracks due to excessive prestress do not occur.
For this reason, there is a merit that a block that is not required to be manufactured in a match cast can be used, and mass production is possible. When an alternating horizontal force is applied to a conventional reinforced concrete structure column during an earthquake or the like, bending cracks occur at the part where the moment increases, stress concentrates at that part, the strain of the main reinforcing bar increases sharply, and the main reinforcing bar plasticizes and Protrudes toward. As a result, the cover concrete is peeled and peeled, leading to destruction. On the other hand, the advantage of this connection technology is that stress is transmitted to the reinforcing steel and concrete that are later attached with a filler such as grout or mortar through the filler, so that even if cracks occur due to horizontal force, the filler and the reinforcing steel Is gradually reduced, so that the rebar is uniformized without a sudden increase in strain. In addition, the filler around the reinforcing bar is more easily deformed than concrete, so that the deformation of the reinforcing bar can be absorbed without restraint, and the destruction of the structure can be delayed. When applied to the joining of precast concrete members, the deformation and strain are dispersed at the joints, the progress of destruction to other parts is small, and the repaired parts are limited even when repairing damaged parts.
Excellent economy.

[0005]

However, in the joining method using the above-mentioned reinforcing bar, when the structure becomes long, the reinforcing bar also needs to be long, and a fixed-length reinforcing bar is connected by pressure welding or a coupler. Must be used. For this reason, there is a problem that it takes time and effort to connect, and a long boom crane is required to insert a long reinforcing bar. The present invention solves such a problem, and uses a flexible and high-strength PC strand that can be easily inserted into a hole without the need for connection of rebar or a lifting crane for a long boom. It is another object of the present invention to realize a method for joining precast concrete blocks.

[0006]

SUMMARY OF THE INVENTION According to the present invention, a columnar structure is constructed by sequentially stacking precast concrete blocks having vertically inserted PC strand insertion holes communicating with each other on a foundation concrete, and constructing a columnar structure. The time-hardening filler is filled, the PC strand is inserted into the insertion hole, the time-hardening filler is fixed, and the stacking block is connected to the PC.
This is a method for joining precast concrete blocks, characterized by being connected by strands.

[0007] The PC strand used here has a tensile strength about three times that of a reinforcing bar, and the amount of steel material can be reduced. In addition, since it is highly flexible, it is easy to insert it into the hole while rewinding from the drum, and a lifting crane having a long boom is not required. Note that the PC strand is a material for binding the concrete block, and does not introduce prestress into the concrete and does not need to introduce tension.

In the above joining method, the order of filling the insertion hole with the time-curable filler and the step of inserting the PC strand into the insertion hole may be reversed. Further, the time-curable filler is cement grout,
Or it may be a cement mortar. These curable fillers, after curing, demonstrate appropriate adhesion,
When a large force is applied to the concrete block or a repeated load is applied, the concrete block yields or breaks ahead of the concrete and absorbs the strain energy, thereby preventing the concrete joint from being damaged.

[0009]

Embodiments of the present invention will be described below with reference to the drawings. The embodiment is an example in which precast concrete cylindrical pipe blocks are stacked and applied to a pier of a bridge, but the present invention is not limited to this.

FIG. 1 is a side view of a pillar-shaped skeleton 10 of a pier. A precast concrete cylindrical pipe block 11 is applied to a joint joint with an adhesive, stacked to a predetermined height, and penetrated from a top end to a foundation concrete (footing) 12. Main bar 13
Are shown in the figure. As the penetrating main bar, a flexible PC strand is used and supplied while being rewound from the drum 14 wound in a coil shape.
As shown by an arrow 17 in FIG. After being inserted into the foundation 12, a filler (mortar) is injected and fixed. The penetrating main bar 13 is
Needless to say, the PC strand may be cut into a predetermined length on the ground in advance and inserted.

FIG. 2 shows a columnar skeleton 1 constructed in this manner.
0 is the pier of the bridge. FIG. 3 is a cross-sectional view of the precast concrete cylindrical pipe block 11 taken along the line AA in FIG. In the pipe wall, there is PC
A sheath 21 for accommodating the strand 13 is provided. In addition, an insertion hole is formed by the sheath 21 into which the PC steel rod 22 is inserted for securing safety when stacking the blocks and consolidating the adhesive for joining the blocks. Prestress is introduced into the PC steel bar 22 for each cylindrical tube block 11 and connected by a coupler.

In this example, a PC steel rod was used in combination with a precast concrete block. However, if there is sufficient block weight for the stability of the columnar structure and the compaction of the adhesive,
It is not always necessary to use a PC steel bar together.

FIG. 4 is a partially detailed view of FIG. 2, in which the PC strand 13 is filled with the filler 24 in the insertion hole 21 of the PC strand 13 communicating from the foundation concrete 12 to the upper end of the columnar frame.
It is fixed with. At the lower end of the PC strand 13, a fixing tool 23 serving as an anchor is mounted so as to prevent the PC strand 13 from coming off. Filling material 2
In the injection of No. 4, an injection pipe 26 connected to the lower end of the sheath 21 is buried in the foundation concrete 12 and injected from an injection hole 25 opened on the upper surface of the footing 12. This may be performed by pouring from the upper end of the columnar skeleton 10, but the workability deteriorates when the columnar skeleton becomes long.

The filler may be injected before the PC strand is inserted, and then the PC strand may be immersed in the filler, and then injected after the PC strand 13 is inserted. It may be that. The grouting liquid or mortar is used as the filler 24 used here. When the grouting liquid is injected before the insertion of the PC strand 13, a setting retarder is added to keep the fluidity for several hours. It is preferable to use curable grout or delayed-curable mortar.

FIGS. 5 to 7 are perspective views showing examples of shapes of precast concrete blocks suitable for the method of the present invention. FIG. 5 shows a precast concrete cylindrical tube block 31 used in the above-described example. FIG. 6 shows a solid precast concrete cylindrical block 32. FIG. 7 shows a solid precast concrete prismatic block 33, but it may have a hollow cylindrical shape.

Next, test examples of the method of the present invention will be described. A prismatic structure (specimen) 40 shown in FIG. 8 was prototyped, and a test on seismic performance was performed. An individual precast block 41 is manufactured, an adhesive is applied to these joint end surfaces, and the blocks are stacked. A prestress of about 1 N / mm ² is introduced with a PC steel rod 42 to assemble the blocks while tightening the blocks 41. Then, the mortar was filled in the axial main reinforcement insertion hole 43 and the axial main reinforcement 44 was inserted to complete the prismatic structure 40. The size of the specimen 40 is 400 mm x 400 mm x
The height is 1500 mm, and the ratio between the shear supports is 3.75 mm.
Reinforcing bar 45 or PC strand 46 as axial main bar 44
FIG. 9 and FIG. 10 show cross-sectional views of the respective test specimens using.

In the test piece 51 shown in FIG. 9, the PC steel rod 42 was unbonded with a fixing member provided at the lower end, and the reinforcing bar 45 as the main reinforcing bar was completely fixed with mortar using SD345 and D13. Yield point 371N /
A reinforcing bar 45 having a mm ² and a yield ratio of 47.0 kN is used. The main bar ratio is 0.0095 only for the main bar and 0.011 when the PC steel bar 42 is included. Specimen 52 shown in FIG. 10 has SWPR7A and 1T9.3 as PC strands 46 as main bars.
Was completely fixed with a mortar using PC strand 46 of No. 1.
The PC steel bar 42 is the same as in FIG. Yield point 1771 N / mm ² , yield ratio 91.4
The main bar ratio is 0.0026 for the main bar only, and the main bar ratio including the PC steel rod 42 is 0.0042. Also, the stirrup 47 uses SD345 and D6 for both FIGS.
The interval was 30 mm and the volume ratio was 0.0126. PC steel rod 4
2 was a steel material of 13 mmφ, 930/1080 class and elongation of 12%.

Using a loading device 60 shown in FIG. 11, a horizontal repetitive load was applied to a test structure 61 by a cylinder 62. The loading device 60 fixes the test structure 61 on the base 63, and applies a horizontal repetitive load from the lateral direction to the upper end thereof.
The displacement was measured. Loading was controlled by the rotation angle (horizontal displacement / load span). The loading step is the time of the calculated crack load and the time of the main bar yield load.
The load was set to be an integral multiple of ad, and loading was repeated three times in each step. In each cycle, a hold time of 1 minute was provided at the maximum load point. The loading was terminated when the load was less than 80% as the final state of the specimen. Loading was performed by load control until yielding, and thereafter by displacement control. The loading speed was 0.05 mm / sec and 0.1 mm / sec. The torsion of the test structure 61 during loading was measured by installing a displacement meter horizontally on the head.

The load displacement curves of the test pieces 51 and 52 shown in FIGS. 9 and 10 are shown in FIGS. 12 and 13, respectively. The destruction was due to the crushing of the concrete at the joint of the blocks for both the test pieces 51 and 52. The maximum strain of the stirrup 47 is 170 μm when the main bar is a reinforcing bar, and 196 μm when the main bar is a PC strand.
m, the strain of the main muscle was 24 cm for the former and 12 cm for the latter. As shown in FIGS. 12 and 13, the columnar structure using the PC strand (the specimen 52) according to the present invention (the specimen 52) is compared with the columnar structure using the conventional reinforcing bar (the specimen 51). Adhesion to the filler is slightly lower and energy absorption is slightly lower, but the load-carrying capacity and deformation performance are the same, and the structure using PC strands has excellent characteristics of excellent recovery performance and small residual displacement. are doing.

[0020]

According to the method of the present invention, the flexibility is higher and the tensile strength is about three times as large as that of the rebar as compared with the conventional technique of connecting the blocks stacked on the foundation concrete with the rebar as the main rebar. Since a certain PC strand is used, the ratio of the main rebar is reduced, the load carrying capacity and the deformability are equal, and a columnar structure excellent in resilience can be easily constructed.

If cement grout or cement mortar is used as the hardening filler over time, it yields at this portion during an earthquake or the like, and the structure has a large strain energy, which is suitable. PC strands do not need to introduce tension, improving workability compared to using conventional rebar,
The effect of reducing the amount of steel material and contributing to improved economic efficiency is enormous.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram of an embodiment of the present invention.

FIG. 2 is an illustration of a pier using an embodiment of the present invention.

FIG. 3 is a view as viewed in the direction of arrows AA in FIG. 2;

FIG. 4 is a partially enlarged view of FIG. 2;

FIG. 5 is a perspective view showing the shape of a column in the embodiment.

FIG. 6 is a perspective view showing the shape of a column in the embodiment.

FIG. 7 is a perspective view showing the shape of a column in the embodiment.

FIG. 8 is a perspective view of a specimen.

FIG. 9 is a sectional view of a specimen.

FIG. 10 is a sectional view of a specimen.

FIG. 11 is a side view of the test loading device.

FIG. 12 is a graph of a load displacement curve.

FIG. 13 is a graph of a load displacement curve.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Column-shaped skeleton 11 Cylindrical pipe block 12 Foundation concrete (footing) 13 Penetrating main bar (PC strand) 14 Drum 15 Hole 16 Scaffolding 17 Arrow 21 Sheath (Insertion hole) 22 PC steel rod 23 Fixing tool 24 Filler 25 Injection hole 26 Injection tube Reference Signs List 31 cylindrical pipe block 32 columnar block 33 prismatic block 40 structure (sample) 41 precast block 42 PC steel bar 43 main bar insertion hole 44 main bar 45 reinforcing bar 46 PC strand 47 band bar 51 sample 52 sample 60 loading device 61 Test structure 62 Cylinder 63 Base

 ──────────────────────────────────────────────────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 No. PS Co., Ltd. (72) Inventor Kazuyoshi Tsuda 5-33-11 Shimbashi, Minato-ku, Tokyo Inside Nippon Hyukan Co., Ltd. 272 AA03 CC03 GG55 GG56 2E125 AA04 AA44 AB12 AB13 AB16 AB17 AC02 AC05 AC08 EA17 EA33 2E163 FA02 FD04 FD25 FD44

Claims (3)

[Claims] 1. A columnar structure is constructed by sequentially stacking precast concrete blocks having vertically extending PC strand insertion holes which communicate with each other on a base concrete, and filling the insertion holes with a time-curable filler. A method of joining a precast concrete block, comprising inserting a PC strand into the insertion hole, fixing a time-curable filler, and connecting the stacked blocks with the PC strand. 2. The method according to claim 1, wherein the step of filling the insertion hole with the time-curable filler and the step of inserting the PC strand into the insertion hole are performed in reverse order.
The method for joining precast concrete blocks according to the description. 3. The method for joining precast concrete blocks according to claim 1, wherein the time-curable filler is cement grout or cement mortar.