JP2012112195A - Concrete placing method to heterogeneous strength concrete beam/floor structure, and heterogeneous strength concrete beam/floor structure - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve the problems due to a construction joint surface of heterogeneous strength concrete in a heterogeneous strength concrete beam/floor structure.SOLUTION: In a heterogeneous strength concrete beam/floor structure 1, high strength concrete C1 is placed to reach a level lower than an underfloor surface level A, and normal strength concrete C2 is placed before the high strength concrete C1 is hardened. Then, the boundary surface of the high strength concrete C1 and the normal strength concrete C2 is mixed by vibration generation means, and a mixed layer M is formed between them. Thus, the concentration of damages on the sudden change part of a cross section width is prevented. Also, prolonging of a process is evaded without the need of waiting for hardening of the high strength concrete C1, and the invasion of the normal strength concrete C2 to the area of the high strength concrete C1 of a beam 2 is prevented as well.

Description

  TECHNICAL FIELD The present invention relates to a method for placing concrete on a different strength concrete beam / floor structure, which is a beam / floor structure in a building, in which concrete having different strength is divided between an upper part and a floor part of the beam and a lower part of the beam. . The present invention also relates to the above-mentioned different strength concrete beam / floor structure.

  As a beam / floor structure in a building, as shown in Patent Document 1, there is a structure using concrete having different strengths in an upper part and a floor part of the beam and a lower part of the beam. The beam / floor structure described in Patent Document 1 is formed by hitting ordinary strength concrete on the ground after the lower portion of the beam is formed of high strength concrete as a half precast beam.

  Here, in addition to the method of using the half precast beam as described above, a method of placing both high-strength concrete and normal-strength concrete in the field is also conceivable. Patent Document 2 shows an example of such a method. Although ordinary strength concrete is not used on the upper part of the beam, a separate formwork for different strength concrete is installed at the boundary between the beam and the slab. Thus, the precast concrete (high-strength concrete) cast on the beam portion and the post-cast concrete (normal strength concrete) cast on the slab portion are partitioned. Then, cast-in concrete is cast, and after the cast-in concrete is cured, the above-mentioned formwork for placement is removed, and then the cast-in concrete is placed.

  However, the method described in Patent Document 2 has a drawback in that the post-cast concrete is placed after the pre-cast concrete has been hardened, resulting in a prolonged work. Moreover, a defect may arise in the joint part of concrete.

  As an example of means for solving such a problem, in Patent Document 3, when placing a plurality of types of concrete having different strengths, before the concrete placed previously hardens, A method is disclosed in which concrete is cast and a mixing part is formed in which the concrete is mixed in the joint part. According to this method, it is possible to prevent the work from being prolonged due to waiting for the hardening of the pre-cast concrete, and to prevent joint defects and the like.

JP 7-305443 A Japanese Patent Laid-Open No. 10-46814 Japanese Patent Laid-Open No. 11-6296

  As described above, the point of using different-strength concrete in the beam / floor structure and several techniques relating to jointing of different-strength concrete have already been known, but the following points have not been considered. In other words, the beam / floor structure forms a T shape when cut along a plane perpendicular to the longitudinal direction of the beam, so the bottom surface level of the floor becomes a part where the cross-sectional width changes suddenly, and when shearing force is applied to the beam The damage tends to concentrate, and if the joint surface of the different strength concrete exists at such a position, the above damage is more likely to occur.

  In addition, of course, in order to obtain a desired strength in the beam / floor structure, it is necessary to ensure the concrete adhesion strength to the reinforcing steel bars. However, if joints of different strength concrete exist around the reinforcing bars, the concrete adhesion properties to the reinforcing bars may not be stable, and the target adhesion strength may not be ensured. If the problem is to be prevented by the process management, there arises a problem that the process management becomes difficult.

  Therefore, the present invention has been made in view of such a situation, and an object of the present invention is to solve some of the problems caused by the joint surface of the above-mentioned different strength concrete in the different strength concrete beam / floor structure. is there.

  A first aspect of the present invention for solving the above problems is a concrete placing method for different strength concrete beams / floor structures in which concrete having different strengths is divided between an upper part and a floor part of the beam and a lower part of the beam. The cast concrete for forming the lower part of the beam is cast until the upper surface level reaches a level lower than the lower surface level of the floor part, and then relatively stronger than the cast concrete. A low-priced concrete for forming the upper part of the beam and the floor part is placed before the pre-cast concrete is hardened, and then the interface between the pre-cast concrete and the post-cast concrete is mixed by mixing means. And a mixed layer of both is formed between the precast concrete and the postcast concrete.

  According to this aspect, in the concrete placement method for different-strength concrete beams / floor structures in which concretes having different strengths are divided between the upper part and the floor part of the beam and the lower part of the beam, the lower part of the beam is formed. Placing precast concrete until the upper surface level reaches a level below the lower surface level of the floor portion, and then postcast to form the upper part of the beam and the floor portion, which are less strong than the precast concrete. Place concrete. That is, the joint portion between the pre-cast concrete and the post-cast concrete is located not on the lower surface level of the floor but below it.

  Therefore, in this case, in the beam / floor structure having a T-shaped cross section, the shear force is applied to the beam as compared with the structure in which the joint surface of the precast concrete and the postcast concrete is present at the site where the cross section width changes suddenly. When added, damage can be prevented from concentrating on the sudden change portion of the cross-sectional width.

  In addition, the cast-in concrete is placed before the cast-in concrete is cured, and then the boundary surface between the cast-in concrete and the post-cast concrete is mixed by mixing means, Therefore, it is not necessary to wait for the hardening of the pre-cast concrete, and the lengthening of the process can be avoided.

  In addition, if the upper surface level of the precast concrete is made the same as the lower surface level of the floor, the cast concrete placed on the floor portion can easily enter the lower area of the beam, that is, an unexpected concrete is placed in the beam area. Since there are cases where the design strength of the beam cannot be secured due to intrusion, process management becomes difficult to prevent this. However, in this aspect, since the upper surface level of the precast concrete is lower than the lower surface level of the floor, the postcast concrete placed on the floor portion is difficult to enter the beam region, and the space between the precast concrete and the postcast concrete is difficult. When mixing the boundary surface, process management becomes easy.

  In addition, since a mixed layer is formed between the precast concrete and the precast concrete (that is, there is no clear boundary surface between the precast concrete and the postcast concrete) Adhesive strength at the interface between concrete and post-cast concrete is not a problem. For example, when a shearing force is applied to a beam, slip does not occur at the interface and does not cause destruction.

  According to a second aspect of the present invention, in the first aspect, the mixed layer is formed so that the post-cast concrete is not mixed below 1/2 of the beam.

  According to this aspect, the mixed layer between the precast concrete and the postcast concrete is mixed with postcast concrete (that is, concrete having relatively lower strength than the precast concrete) below 1/2 of the beam. Therefore, it is possible to minimize the strength reduction of the entire beam.

  A third aspect of the present invention is a heterogeneous strength concrete beam / floor structure in which concrete having different strength is divided between an upper part and a floor part of a beam and a lower part of the beam, for forming the lower part of the beam. An upper surface level of the precast concrete is lower than a lower surface level of the floor portion, and an upper portion and a floor portion of the beam are formed by the postcast concrete having relatively lower strength than the precast concrete, and the precast concrete A mixed layer in which the precast concrete and the postcast concrete are mixed is formed between the cast concrete and the postcast concrete.

  According to this aspect, the different-strength concrete beam / floor structure in which the concrete having different strengths is divided between the upper part and the floor part of the beam and the lower part of the beam is provided between the precast concrete and the postcast concrete. The part is not at the lower surface level of the floor but below it. Therefore, in the same manner as in the first aspect, in the beam / floor structure whose cross-sectional shape is T-shaped, compared to the configuration in which the joint surface between the precast concrete and the post-cast concrete exists in the portion where the cross-sectional width changes suddenly. When a shearing force is applied to the beam, it is possible to prevent damage from concentrating on the sudden change portion of the cross-sectional width.

  In addition, as in the first aspect, since a mixed layer of both is formed between the precast concrete and the postcast concrete, it is not necessary to wait for the hardened concrete to be cured, and it is possible to avoid lengthening the process. In addition, the adhesion strength at the interface between the precast concrete and the postcast concrete does not matter, and when the shearing force is applied to the beam, slippage does not occur at the interface and does not cause breakage.

  Furthermore, as in the first aspect, the upper surface level of the precast concrete is lower than the lower surface level of the floor, so that the precast concrete is difficult to enter the floor portion, and the boundary between the precast concrete and the postcast concrete. Process control is facilitated when mixing the surfaces.

  According to a fourth aspect of the present invention, in the third aspect, the mixed layer is formed so that the post-cast concrete is not mixed below 1/2 of the beam.

  According to this aspect, similar to the second aspect, the mixed layer between the pre-cast concrete and the post-cast concrete is less than 1/2 of the beam shank concrete (that is, relative to the pre-cast concrete). Therefore, the strength reduction of the entire beam can be minimized.

According to a fifth aspect of the present invention, in the third or fourth aspect, an upper end line of the beam is disposed above the mixed layer.
If the joint surface between precast concrete and postcast concrete hits the beam top reinforcement, it will easily cause problems in the adhesion properties of the concrete to the beam top reinforcement, as well as variations in adhesion strength, and ensuring design strength. It becomes difficult. However, according to this aspect, the upper end bars of the beam are disposed above the mixed layer, so that the above-described problems are not caused.

Sectional drawing of the different-strength-strength concrete beam and floor structure concerning 1st Embodiment of this invention. (A)-(C) is explanatory drawing which shows the concrete placement method with respect to the different-strength-strength concrete beam and floor structure based on 1st Embodiment of this invention. Sectional drawing of the different-strength-strength concrete beam and floor structure concerning 2nd Embodiment of this invention. Sectional drawing of the different-strength-strength concrete beam and floor structure concerning 3rd Embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the same structure in each figure, and the overlapping description will be avoided. Further, in the xyz coordinate system shown in each figure, the z direction indicates the direction of gravity, the y direction indicates the length direction of the beam, and the x direction indicates a direction orthogonal to the length direction of the beam. .

  First, a first embodiment of the present invention will be described with reference to FIGS. In FIG. 1, reference numeral 1 denotes a different strength concrete beam / floor structure (also called a concrete beam with a floor (slab)). In the different-strength concrete beam / floor structure 1, the beam 2 and the floor 3 are integrally formed to form a substantially T-shaped cross section, and the beam 2 is further composed of a beam upper portion 2A and a beam lower portion 2B. It has a rectangular shape. As will be described later, the beam upper part 2A and the floor 3 are continuously formed of the same kind of concrete and there is no clear boundary surface between them, but the beam 2 is treated as a rectangular shape for strength design. Is called. Further, the beam upper portion 2A indicates a region above the mixed layer M (described later) in the beam 2, and the beam lower portion 2B indicates a region below the mixed layer M.

  Reference numeral 5 denotes a beam formwork. Pre-cast concrete described later is placed inside the beam formwork 5, and a part of post-cast concrete described later is placed inside the beam formwork 5. . Reference numeral 4 denotes a half precast (Pca) slab plate, and post-cast concrete is placed on top of the half Pca slab plate 4. In the present embodiment, the half Pca slab plate 4 is used for forming the floor 3 and both the formation of the lower floor and the floor formwork are used, but it goes without saying that the present invention is not limited to this.

  Reference numerals 6A and 6B indicate beam upper main bars extending in the longitudinal direction (y direction) of the beam, which are arranged in the beam upper portion 2A. As shown in the drawing, a plurality of the bar upper main bars 6A are arranged at appropriate intervals in the beam width direction, and the beam upper main bars 6B correspond to both ends of the beam upper main bars 6A. The bar is arranged at a position slightly below the beam upper main bar 6A, and constitutes a two-stage bar together with the beam upper main bar 6A.

  Reference numeral 6C denotes a beam lower end main bar that is arranged in the beam lower part 2B and extends in the longitudinal direction (y direction) of the beam. Similar to the beam upper main bar 6A, a plurality of bar lower bar main bars 6C are arranged at appropriate intervals in the beam width direction. In addition, although the reinforcing bar for ensuring the intensity | strength of the said floor 3 is arranged on the floor 3, this reinforcing bar is abbreviate | omitting illustration.

  However, in this embodiment, as shown in Japanese Patent Application Laid-Open No. 7-305443, a “shear force transmission bar that is stretched between the beam upper main bar and the floor reinforcing bar for transmitting the shearing force in the slab surface direction. "Is not arranged. However, the present invention does not exclude the arrangement of such a “shear force transmission line”, and may provide such a “shear force transmission line” in order to ensure strength as necessary.

  Reference numeral 8 denotes a shear reinforcing bar (hoop bar) that is wound between the beam upper main bars 6A and 6B and the beam lower bar main bar 6C. A large number of the shear reinforcement bars 8 are arranged at an appropriate interval in the longitudinal direction (y direction) of the beam 2.

  Next, in FIG. 1, reference numeral M denotes a mixed layer formed by mixing the boundary surface between the precast concrete and the postcast concrete (boundary surface in the uncured state), in which the precast concrete and the postcast concrete are mixed. The symbol t indicates the thickness of the mixed layer.

  Reference numeral D indicates a beam shank (the height of the beam), and reference numeral A indicates the level of the lower surface of the half Pca slab plate 4, that is, the lower surface of the floor 3 (hereinafter referred to as "floor lower surface level A"). Furthermore, the symbol x indicates the distance from the floor lower surface level A to the upper surface of the mixed layer M.

  As shown in the figure, in the different-strength concrete beam / floor structure 1 according to the present invention, the precast concrete is a concrete having a relatively higher strength than the postcast concrete. Also called post-cast concrete as ordinary strength concrete. In the present invention, the mixed layer M is set below the floor lower surface level A, and a predetermined distance x is secured. Further, in the present embodiment, the mixed layer M is formed so as not to be located below 1/2 of the beam dam D, and more specifically, normal strength concrete is not mixed below ½ of the beam dam D. Formed.

  The different strength concrete beam / floor structure 1 shown in FIG. 1 is generally formed as shown in FIGS. As shown in FIG. 2 (A), the beam formwork 5 and the half Pca slab plate 4 form a formwork of a different strength concrete beam / floor structure 1, and the beam upper end main bars 6A to 6C are arranged, High-strength concrete C1 is cast as cast concrete. The high-strength concrete C1 is placed until the upper surface level Sa reaches a level lower than the floor lower surface level A. Next, ordinary strength concrete C2 as post-cast concrete having relatively lower strength than the high strength concrete C1 is placed before the high strength concrete C1 is hardened.

  And before normal strength concrete C2 and high strength concrete C1 harden | cure completely, as shown in FIG.2 (B), vibrator rod 11 as a mixing means is made into upper surface level Sa (that is, high strength concrete) of high strength concrete C1. Insert until it reaches slightly below the boundary surface between C1 and ordinary strength concrete C2, and mix the boundary surface between high strength concrete C1 and ordinary strength concrete C2 to form a mixed layer M of both (FIG. 2). (C)). At this time, in this embodiment, management is performed such that the tip of the vibrator rod 11 does not reach below 1/2 of the beam D. By this work, not only the boundary surface between the high-strength concrete C1 and the normal-strength concrete C2 is mixed, but also the normal-strength concrete C2 can be compacted at the same time.

  Here, when the boundary surface between the high-strength concrete C1 and the normal-strength concrete C2 is mixed by using the vibrator rod 11 to form the mixed layer M, the mixed layer M is not necessarily clear (clean) as illustrated. The portion into which the vibrator rod 11 is inserted and the periphery thereof are mixed, and the region other than the layer is not necessarily mixed sufficiently. Further, when the vibrator rod 11 is pulled out, the high-strength concrete C1 adhering to the vibrator rod 11 may be slightly mixed into the upper portion of the beam upper portion 2A, that is, the normal strength concrete C2.

  Therefore, in the present invention, the mixed layer M is not necessarily formed for the purpose of forming a clear (clean) layer as shown in the drawing, but at least the boundary surface between the high-strength concrete C1 and the normal-strength concrete C2 is mixed. By doing so, it is formed for the purpose of not forming a clear boundary surface between the two. Further, the mixing ratio of the concrete in the mixed layer M is preferably such that the distribution of the proportion is made gradation so that the proportion of the high-strength concrete C1 decreases upward, but is not limited to this, and at least the high strength It is sufficient that a clear boundary surface is not formed between the concrete C1 and the normal strength concrete C2.

  In this embodiment, the vibrator rod 11 is used as the mixing means. However, it goes without saying that the vibration generating means other than the vibrator rod 11, for example, the vibration generating means is provided outside the beam formwork 5. The boundary surface between the high-strength concrete C1 and the normal-strength concrete C2 may be mixed by installing and applying vibration to the entire beam formwork. Moreover, any means may be used as long as it can mix the boundary surface between the high-strength concrete C1 and the normal-strength concrete C2 without being limited to the vibration generating means.

  As described above, according to the different strength concrete beam / floor structure 1 and the concrete placing method therefor according to the present invention, the precast concrete (high strength concrete C1) and the postcast concrete (normal strength concrete C2) are used. The intermediate joint portion (mixed layer M) is not below the floor lower surface level A but below it.

  Therefore, in this case, the beam / floor structure having a T-shaped cross-section has a beam surface compared to a structure in which the connection surface between the high-strength concrete C1 and the ordinary-strength concrete C2 is clearly present in a portion where the cross-sectional width changes suddenly. When a shearing force is applied to 2, damage can be prevented from concentrating on the sudden change portion of the cross-sectional width.

  Ordinary strength concrete C2 is placed before the high strength concrete C1 is hardened, and then the boundary surface between the high strength concrete C1 and the ordinary strength concrete C2 is mixed by mixing means, and a part of both is mixed between the two. Therefore, it is not necessary to wait for the high-strength concrete C1 to harden, and it is possible to avoid a prolonged process.

  In addition, if the upper surface level of the high-strength concrete C1 is the same as the floor lower surface level A, the normal-strength concrete C2 placed on the floor 3 can easily enter the region of the beam lower portion 2B, that is, the height of the beam lower portion 2B is high. Since unexpected concrete (ordinary strength concrete C2) enters the high-strength concrete C1 and the design strength of the beam 2 cannot be ensured, the process management becomes difficult to prevent this. However, in the present invention, since the upper surface level Sa of the high-strength concrete C1 is lower than the floor lower surface level A, the normal-strength concrete C2 placed on the floor 3 is difficult to enter the high-strength concrete C1 of the beam lower portion 2B. When mixing the boundary surface between the concrete C1 and the normal strength concrete C2, process management becomes easy.

  In addition, since a mixed layer of both is formed between the high-strength concrete C1 and the normal-strength concrete C2 (that is, there is no clear interface between the high-strength concrete C1 and the normal-strength concrete C2). ) Adhesive strength at the interface between the high-strength concrete C1 and the normal-strength concrete C2 does not matter. For example, when a shearing force is applied to the beam 2, slipping occurs at the interface and causes destruction. Nor. Moreover, the design regarding the connecting portion between the two becomes unnecessary, and the design work is simplified.

  In addition, the fact that the upper surface level Sa of the high-strength concrete C1 is lower than the floor lower surface level A also reduces the amount of use of the high-strength concrete C1, thereby contributing to cost reduction and work time reduction. Further, by reducing the amount of first-time concrete (advanced concrete) used, the side pressure applied to the beam form 5 can be reduced, and the risk of collapse of the beam form 5 can be reduced. Further, by reducing the amount of the first concrete placement, the first and second (post-working) concrete placement intervals can be shortened, and the concrete can be compacted easily.

  In addition, in the present embodiment, the beam upper end main reinforcement 6B is disposed above the mixed layer M. That is, when the connecting surface of the high strength concrete C1 and the normal strength concrete C2 is applied to the beam upper main bar 6B, a problem of the adhesion property of the concrete to the beam upper main bar 6B is likely to occur, and the adhesion strength is likely to vary. In addition, although it is difficult to ensure the design strength, in the present embodiment, since the beam upper main bar 6B is disposed above the mixed layer M as described above, the above problems are not caused.

  In the present embodiment, the mixed layer M between the high-strength concrete C1 and the normal-strength concrete C2 is formed so that the normal-strength concrete C2 is not mixed below 1/2 of the beam, so the entire beam 2 The strength reduction can be minimized.

<< Other Embodiments >>
The different strength concrete beam / floor structure 1 ′ shown in FIG. 3 is a form in which the floor 3 ′ is provided with a stepped portion B for barrier-free purposes such as a bathroom. The present invention can also be applied to such a form. That is, the joint portion between the precast concrete (high strength concrete C1) and the postcast concrete (normal strength concrete C2) is not the floor lower surface level A (lower floor lower surface level in this embodiment), It is placed below it and a mixed layer M is formed between them. Thereby, the same effect as embodiment already demonstrated can be acquired.

  Further, the different strength concrete beam / floor structure 1 ″ shown in FIG. 4 is provided with an incision bar 9 that enters a predetermined amount from the beam upper main bar 6A arranged in the beam upper part 2A into the beam lower part 2B. 1 are arranged at predetermined intervals in the longitudinal direction of the beam 2, and the cross-sectional shape shown in FIG. 1 and the cross-sectional shape shown in FIG. It has become a form.

In the present invention, a clear joint surface is not formed between the high-strength concrete C1 and the normal-strength concrete C2, and a mixed layer M in which both are mixed is formed to ensure the adhesion strength between the two. Although the use of the incisor 9 can be made unnecessary, the incisor 9 may be provided as necessary. However, it goes without saying that if the insertion bar 9 can be omitted, the bar arrangement becomes easy.
Moreover, each embodiment described above is an example, and it cannot be overemphasized that various deformation | transformation are possible.

1 Different strength concrete beam / floor structure 2 Beam 2A Beam upper part 2B Beam lower part 3 Floor (slab)
4 Half PCa slab plate 5 Beam form 6A, 6B Beam upper main bar 6C Beam lower bar 8 Shear reinforcement bar 9 Insert bar 11 Vibrator (vibration generating means)
A Floor bottom level C1 Precast concrete (high-strength concrete)
C2 Post-cast concrete (normal strength concrete)
D Beam M M Mixed layer x Distance from floor lower surface level A to upper surface of mixed layer M t Thickness of mixed layer

Claims (5)

A concrete placement method for different strength concrete beams / floor structures, in which concrete with different strengths is divided between the upper part and floor part of the beam and the lower part of the beam,
Placing the pre-cast concrete for forming the lower part of the beam until the upper surface level reaches a level lower than the lower surface level of the floor part,
Next, a post-cast concrete for forming the upper part of the beam and the floor portion, which is relatively lower in strength than the pre-cast concrete, is placed before the cast concrete is cured,
Next, the mixing means mixes the interface between the precast concrete and the postcast concrete, and forms a mixed layer between the precast concrete and the postcast concrete,
A concrete placement method for a beam / floor structure. In the concrete placement method according to claim 1, the mixed layer is formed so that the post-cast concrete is not mixed below 1/2 of the beam.
A concrete placement method for a beam / floor structure. It is a different-strength concrete beam / floor structure consisting of concrete with different strengths in the upper and floor parts of the beam and the lower part of the beam,
The upper surface level of the precast concrete for forming the lower part of the beam is lower than the lower surface level of the floor portion,
The upper part of the beam and the floor part are formed by post-cast concrete having a relatively lower strength than the pre-cast concrete,
Between the precast concrete and the postcast concrete, a mixed layer in which the precast concrete and the postcast concrete are mixed is formed,
Different strength concrete beams and floor structures. The heterogeneous strength concrete beam / floor structure according to claim 3, wherein the mixed layer is formed so that the post-cast concrete is not mixed below 1/2 of the beam.
Different strength concrete beams and floor structures. The concrete beam / floor structure according to claim 3 or 4, wherein an upper end of the beam is disposed above the mixed layer.
Different strength concrete beams and floor structures.

Images