JP2642293B2 - Crack-induced joint structure of concrete slab - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a joint structure for a concrete slab which concentrates cracks generated in a concrete slab such as a concrete slab or a post-cast concrete slab in a double slab structure.

[0002]

2. Prior Art and Problems to be Solved by the Invention
Conventionally, as the induced joint structure applied to this type of concrete slab, as shown in FIG.
0, 1/5 to 1/3 of concrete slab thickness
Is generally known. However, in this structure, since the reinforcing bar 22 buried in the concrete slab is continuous at the joint, the effect of the cutter joint 21 is deteriorated, and the function as the induced joint cannot be sufficiently exhibited. .

In order to cope with this problem, there is a structure as shown in FIG. 11 in which the reinforcing bar 22 is cut by a cutter to make the reinforcing bar 22 discontinuous. However, this structure requires too much time for cutting with the cutter, and when an eccentric load is applied to the opposing concrete slab bordering on the cutter joint 21, the concrete slab 20 may shift vertically and the concrete slab 20 may be stepped. There is something.

For this reason, as shown in FIG. 12, a slip bar 23 is previously set at a position where joints are to be applied, and
The reinforcing bar 22 is also arranged so as to be discontinuous at the position where the cutter joint 21 is applied, and a structure for preventing the concrete slab 20 from shifting in the vertical direction is also adopted. But this structure
It takes time and effort to accurately perform the work of installing the slip bar 23.

On the other hand, FIG. 13 shows a structure in which a steel fiber 24 is mixed in concrete instead of the reinforcing bar 22, and the work of arranging the reinforcing bar is omitted. The problem with this structure is that unless the depth of the cutter joint 21 is not less than 1/3 of the thickness of the concrete slab, the function as the induced joint is not sufficiently exhibited. It takes too much time to cut off.

Further, as shown in FIG. 14, a slit joint material 5 is buried under the induction joint portion 3 formed on the surface of the concrete slab to induce a contraction crack at an intended position, and the depth of the cutter joint is determined. The induced joint portion 3 of the concrete slab 2 has a cross-sectional defect by the thickness of the slit joint material 5 plus the height, and the shrinkage crack is more concentrated at the induced joint position than in the case of the cutter joint alone. A way to make it easier has been devised.

However, in the above-mentioned method, since the slit joint material 5 is hidden in the concrete slab 2 that has been cast, it is difficult in construction to accurately align the cutter joint 3 with the upper end of the slit joint material 5. there were. Also, before the construction of the cutter joint 3, along the upper end of the slit joint material 5,
There was a defect that cracks occurred.

As described above, conventionally, a method for effectively concentrating cracks at induced joints is complicated and time-consuming.
There was a disadvantage that the construction period was long.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object a simple and robust structure that does not shift in the vertical direction, and effectively realizes the concentration of cracks at induced joints. It is an object of the present invention to provide a crack-inducing joint structure of a concrete slab which can be made to work.

[0010]

SUMMARY OF THE INVENTION The present invention relates to a structure of an induction joint for concentrating cracks generated in a concrete slab, and the structure of the induction joint of claim 1 is "a bottom plate disposed along a lower surface of a concrete slab. And a rising plate portion arranged so as to extend from the lower surface to the surface, and the rising plate portion has a plate-shaped slit joint material having a shape of a cross-shaped lower portion and a cross-sectionally straight upper portion. Embedded in the concrete slab from the lower surface to the surface, and the concrete slab is divided by the slit joint material. "

According to a second aspect of the present invention, in the induction joint structure according to the first aspect, a cap having a U-shaped cross section is placed on an upper end edge of the slit joint material to be buried.

In the present invention, since the slit joint material is embedded in the concrete slab from the lower surface to the surface of the slab, and the slab concrete is divided by the slit joint material, the joint is strictly speaking a "crack-inducing joint". Not applicable, but expressed as “crack-inducing joint” according to custom.

[0013]

In the joint structure according to the first aspect, the plate-shaped slit joint material to be buried is composed of a bottom plate arranged along the lower surface of the concrete slab and a rising plate arranged from the lower surface to the surface, In addition, since the rising plate portion has a shape having a lower portion having a U-shaped cross section and an upper portion having a linear cross section, the vertical displacement between the slabs divided by the buried slit joint material is restricted. You.

According to a second aspect of the present invention, a cap having a U-shaped cross section is placed on the upper edge of the slit joint material, and the cap is moved up and down so as to cope with a change in the thickness of the slab and unevenness. The height can be adjusted.

[0015]

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a concrete slab according to an embodiment of the present invention;

As shown in FIG. 1, the induced joint structure 1 completely separates a post-cast concrete slab 2 or a post-cast concrete slab 2 of a double slab structure at a position where an induced joint 3 is to be applied. A slit joint material 5 continuous to the slab surface is embedded in the slab. The slit joint members 5 are continuously laid in a lattice shape, and the interval is about 3 m to 5 m, so that the concrete slab 2 partitioned by the slit joint members 5 does not crack.

In order to provide the induction joint 3, the slit joint 5 is fixed on the discarded concrete 10 on the gravel 9 by nails or cross tape, and then the reinforcing bar 5 is not positioned at the position where the induction joint 3 is applied. It is arranged so as to be continuous, and concrete 7 is cast.

The slit joint material 5 used in the present invention is a long thin plate made of metal or plastic, and has a flat bottom plate portion 5-2 disposed along the lower surface of the slab 2 as shown in FIGS. It comprises a rising plate portion 5-1 which rises from the bottom plate portion and is arranged from the lower surface of the slab to the surface.

The rising plate portion 5-1 of the joint material 5 of this embodiment has a lower portion bent in a V-shape in cross section, and mutually fits on two opposing thickness surfaces of the slab 2 sandwiching the joint material 5. Concavo-convex portions 8, 8 are formed to provide a so-called shear key function of restraining vertical displacement between the two slabs 2, 2 separated by the joint material 5.

The upper part of the rising plate part 5-1 stands substantially vertically.

FIGS. 4 (a), (b), (c) and (d) show slit joints 5
Are shown, but in any case, the bottom plate portion 5-
2 and a rising plate portion 5-1. The lower portion of the rising plate portion 5-1 is bent in a U-shape in cross section, and the upper portion rises almost vertically with a straight cross section.

FIGS. 5 (a), 5 (b), 5 (c) and 5 (d) show slit joints 5
, That is, a cap 4 for adjusting the height having a U-shaped cross section is put on the upper edge of the rising plate 5-1. FIG.
When the height of the slab 2 is different as shown in (a) and (b), or when the slab 2 is uneven, the height of the rising plate portion 5-1 can be adjusted by the cap 4. The cap 4 is fixed to a desired height position of the slit joint material 5 using a nail or a cross tape.

FIG. 7 shows a steel fiber 1 instead of a reinforcing bar.
This is an example in which an induced joint 3 is formed by using a slit joint material 5 in a concrete slab 2 reinforced by using a joint 1. FIG. 8 shows an example in which the induction joint 3 is formed by using the slit joint member 5 in the double-structure concrete slab 2 constructed by laying the spring treatment panel 13 on the mat slab 12.

As shown in FIG. 9, a water-swelling resin material 14 continuous in the horizontal direction is fixed to both surfaces of the rising plate portion 5-1 of the slit joint material 5, and concrete is cast to form the induced joint 3. Then, the water which invades from the bottom surface of the slab 2 by the capillary action is absorbed and swells, and it is possible to prevent permeation of the groundwater into the surface of the concrete slab.

[0025]

As described above, the present invention has the following effects.

[0026] Shrinkage cracks of the concrete slab are concentrated on the joints to be induced, so that random cracks can be extremely reduced.

There is no need to create joints with a cutter, slit joints can be installed and buried, construction can be performed, and vertical displacement between divided slabs can be prevented without using a slip bar or the like. Can be achieved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a partial cross section of an induction joint portion of an embodiment.

FIG. 2 is a perspective view of a slit joint material.

FIG. 3 is an enlarged sectional view of an induction joint portion according to the embodiment.

FIGS. 4 (a), (b), (c), and (d) are cross-sectional views of a slit joint material.

FIGS. 5 (a), (b), (c), and (d) are cross-sectional views of a slit joint material in which a height adjusting cap is sandwiched between upper end edges.

FIGS. 6A and 6B are cross-sectional views of joints in which the height of a slit joint material is adjusted with a cap corresponding to slabs having different heights.

FIG. 7 is a perspective view showing a partial cross section of an induction joint provided on a concrete slab reinforced with steel fibers.

FIG. 8 is a perspective view showing a partial cross section of an induction joint provided on a concrete slab having a double slab structure.

FIG. 9 is a cross-sectional view of a slit joint material to which a water-swelling resin material is fixed.

FIG. 10 is an explanatory view of a conventional induced joint portion.

FIG. 11 is an explanatory view of a conventional induced joint portion.

FIG. 12 is an explanatory view of a conventional induced joint portion.

FIG. 13 is an explanatory diagram of a conventional induced joint portion.

FIG. 14 is an explanatory view of a conventional induced joint portion.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Induction joint structure, 2 ... Concrete slab, 3 ... Induction joint, 4 ... Height adjusting cap, 5 ... Slit joint material, 5-1 ... Erecting plate part, 5-2 ... Bottom plate part, 6 ... Rebar , 7
... concrete, 8 ... concave and convex parts which fit each other,
9: gravel, 10: discarded concrete, 11: steel fiber, 12: mat slab, 13: spring treatment panel, 14: water-expandable resin material, 20: concrete slab,
21 ... induction joint, 22 ... rebar or welded wire mesh, 23 ... slip bar, 24 ... steel fiber.

 ──────────────────────────────────────────────────続 き Continuation of the front page (72) Inventor Katsuhide Ishiyama 1-3-8 Moto-Akasaka, Minato-ku, Tokyo Kashima Construction Co., Ltd. Tokyo Branch (56) References JP-A-61-165441 (JP, A) Open Sho 60-94503 (JP, U) Open Sho 57-117145 (JP, U)

Claims (2)

(57) [Claims] 1. A bottom plate portion arranged along the lower surface of a concrete slab and a rising plate portion arranged from the lower surface to the surface, wherein the rising plate portion has a lower portion having a U-shaped cross section and a rising portion having a straight cross section. A crack-inducing concrete slab characterized by burying a plate-shaped slit joint material having a shape consisting of an upper part from a lower surface of a slab in a concrete slab and dividing the concrete slab by the slit joint material. Joint structure. 2. The joint structure for inducing cracks in a concrete slab according to claim 1, wherein a cap having a U-shaped cross section is placed on an upper edge of the slit joint material.