JP2013060712A - Construction method of hollow frame and hollow concrete structure using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To compact concrete at a lower side of a hollow frame comprised of a hollow body.SOLUTION: A hollow frame 10 for forming a cavity part 6 by being buried in concrete when constructing a hollow slab bridge 1 comprises a tubular hollow frame body 11 which is disposed approximately horizontally at a predetermined position, and a tubular body 12 which is provided in such a manner that the upper end and lower end thereof are opened on upper and lower surfaces of the hollow frame body 11, respectively. A multivibrator 21 is inserted into the tubular body 12 in the state of casting concrete up to a position higher than the lower end of the hollow frame 10, and concrete at a lower side of the hollow frame 10 is directly compacted.

Description

  The present invention relates to a hollow mold for embedding in concrete when forming a concrete structure to form a cavity, and a method for constructing a hollow concrete structure using the hollow mold. The present invention relates to a technology that enables compaction of concrete below.

  In a concrete structure such as a floor or a beam, a hollow mold may be embedded to form a hollow portion in the interior, particularly in an intermediate portion in the height direction. When a hollow mold is used, the concrete volume can be reduced and the weight can be reduced, so that a large span can be achieved by increasing the thickness of the structure. As the hollow mold, there are those made of a hollow body formed of a thin steel plate or plastic, and those made of a solid body formed of a plastic foam or an inorganic foam (see Patent Documents 1 and 2). In addition, as the shape of the hollow mold, there are a dice shape, a spherical shape, a rectangular tube shape, and a cylindrical shape (see Patent Documents 1 and 2). A cylindrical shape is often adopted in consideration of properties and the like.

  By the way, when placing concrete, a method of applying vibration to the concrete using an internal vibrator (so-called vibrator) is generally employed in order to remove the mixed air and compact the concrete. However, when using a hollow mold, it is difficult to confirm whether or not concrete has spread under the hollow mold, so a pair of through holes are provided on the upper and lower sides of the hollow mold made of a hollow body. An invention has been proposed in which a tubular body having both ends formed closed with window members is formed in the pair of through holes, and the gap between the through hole and the tubular body is closed (Patent Document 3). According to this invention, the lower part of the hollow mold can be visually recognized through the window portion, and the lack of strength of the hollow mold resulting from the provision of the window can be compensated by the tubular body.

JP 2002-138665 A JP 2003-90526 A JP 2011-94337 A

  On the other hand, the range (diameter) of the concrete that can be compacted by the vibrator is about 10 times the diameter of the vibration part of the vibrator. Moreover, a hollow formwork is normally arrange | positioned between the lower end reinforcement and upper end reinforcement of a concrete structure. Therefore, when placing concrete using a hollow mold with a relatively large structure and a large diameter, the vibration of the vibrator is difficult to reach directly under the hollow mold and the reinforcing bars prevent the flow of the concrete. As a result, concrete compaction tends to be insufficient, and in order to solve this, it is necessary to bring the vibrator closer to the range where vibration is transmitted below the hollow mold.

  However, in the invention of Patent Document 3, it can be confirmed through the window whether or not the concrete has spread below the hollow mold frame, but the concrete below the hollow mold frame is compacted with a vibrator. It is difficult.

  Here, it is conceivable to use a multivibrator in which an extension pipe is provided on the base end side of the vibration part and the length of the rod-shaped part is increased, and the vibration part is inserted in an oblique direction so as to approach directly below the hollow mold. However, in a hollow concrete structure such as a hollow floor slab bridge, a sheath for inserting a PC steel wire in addition to a reinforcing bar may be installed between hollow form frames adjacent in the horizontal direction. When arranged in a shape, the multivibrator cannot be inserted obliquely depending on the arrangement height of the sheath, and the concrete below the hollow mold cannot be compacted.

  This invention is made | formed in view of such a background, and makes it the main objective to enable the compaction of concrete under the hollow mold which consists of a hollow body.

  In order to solve the above problems, the present invention is a hollow mold (10) for forming a hollow portion (6) by being embedded in concrete when constructing a hollow concrete structure (1), A cylindrical hollow frame body (11) disposed substantially horizontally at a predetermined position, and an upper end (12a) and a lower end (12b) are provided so as to open on the upper surface and the lower surface of the hollow frame body, respectively. A tubular body (12) is provided.

  By setting it as such a structure, a vibrator can be inserted in the inside of a tubular body and the concrete below a hollow mold can be compacted directly.

  Moreover, in order to solve the said subject, this invention is a construction method of a hollow concrete structure (1), Comprising: The upper end (12a) and the lower end (12b) are respectively cylindrical hollow mold bodies (11). Preparing a hollow mold frame (10) provided with a tubular body (12) inside the hollow mold frame main body so as to open to the upper surface and the lower surface of the hollow mold frame, and disposing the hollow mold frame at a predetermined position substantially horizontally And a step of inserting a vibrator (21) into the tubular body in a state where the concrete is cast to a position higher than the lower end of the tubular body, and compacting the concrete below the hollow mold frame, and To do.

  By setting it as such a structure, the concrete below a hollow mold can be compacted directly with a vibrator.

  In addition, according to one aspect of the present invention, the method may further include a step of closing the opening at the upper end of the tubular body after the step of compacting the concrete below the hollow mold.

  According to this configuration, since it is possible to prevent the concrete from flowing into the tubular body from the upper opening, it is possible to suppress an increase in the volume of the concrete.

  As described above, according to the present invention, it is possible to compact concrete below the hollow mold made of a hollow body, and to ensure the quality of the hollow concrete structure.

Longitudinal sectional view of a hollow floor slab bridge constructed by applying the present invention II-II sectional view in FIG. III-III sectional view in FIG. Sectional view of the hollow form shown in FIG. Cross-sectional view showing the construction state of the hollow floor slab bridge shown in FIG. Cross section of the main part of the hollow floor slab bridge shown in FIG. Cross section of the main part of the hollow floor slab bridge according to the first modification Cross-sectional view of main part of hollow floor slab bridge according to second modification

  Hereinafter, with reference to drawings, an embodiment of hollow formwork 10 concerning this invention and hollow floor slab bridge 1 built using this hollow formwork 10 is described in detail.

  As shown in FIG. 1 and FIG. 2, the hollow floor slab bridge 1 is provided with a top stress 2 and a bottom reinforcement 3 and prestressed by a post-tension method using a PC steel wire 4 extending in the bridge axis direction. A prestressed concrete bridge. The PC steel wire 4 is inserted into each sheath 5 (FIG. 2) arranged in a plurality of stages in the vertical direction in one longitudinal section, and is tensioned and fixed after placing concrete to introduce prestress into the hollow floor slab bridge 1. In addition, a tunnel-like cavity 6 (FIG. 2) is formed in the hollow floor slab bridge 1 by a hollow mold 10 extending substantially horizontally in the bridge axis direction.

  Here, the hollow floor slab bridge 1 will be described as having no gradient in the bridge axis direction, but the hollow floor slab bridge 1 may have a gradient. In that case, the hollow mold 10 is inclinedly arranged in accordance with the gradient of the hollow floor slab bridge 1. Here, a common-sense gradient range of a hollow concrete body such as the hollow floor slab bridge 1 is assumed to be substantially horizontal.

  The hollow mold 10 has a cylindrical shape with both ends closed, and the cavity 6 has a circular cross section. A plurality of (in this case, four) hollow portions 6, that is, hollow molds 10, are arranged at equal intervals in the direction perpendicular to the bridge axis. Are arranged at the same height. In addition, the PC steel wires 4 and the sheaths 5 are arranged in 2 stages × 2 rows here between the hollow molds 10 adjacent to each other.

  On the other hand, the PC steel wire 4 and the sheath 5 are arranged in a suspended curve shape in the bridge axis direction as shown in FIG. 1, and near the center 1c in the bridge axis direction, as shown in FIG. It is arrange | positioned at the lower part of 1 and near the edge part 1e of a bridge axis direction, as shown in FIG.

  Therefore, in the vicinity of the center 1c in the bridge axis direction where the sheath 5 is arranged at the lower part of the hollow floor slab bridge 1, as shown in FIG. 2, a multivibrator having a vibrating portion 21a at the tip indicated by an imaginary line when placing concrete By inserting 21 obliquely from above and passing over the sheath 5, the vibrating portion 21 a can be brought close to the bottom of the hollow mold 10. On the other hand, near the end portion 1e in the bridge axis direction where the sheath 5 is disposed at the upper part of the hollow floor slab bridge 1, as shown in FIG. By allowing the vibration to pass, the vibrating portion 21a can be brought close to the bottom of the hollow mold 10, and vibration can be applied to the concrete being placed.

  On the other hand, the position in the height direction of the sheath 5 changes according to the position in the bridge axis direction, and the section in FIG. 1 in which the sheath 5 is located in the middle of the height positions shown in FIGS. In S, since it interferes with the sheath 5, the multivibrator 21 cannot be inserted obliquely, and the vibrating part 21 a cannot be brought close to the hollow mold 10.

  Therefore, the hollow mold 10 has a configuration as shown in FIG. 4, that is, a cylindrical hollow mold body 11 arranged substantially horizontally, and a center in the width direction inside the hollow mold body 11. 12a and the lower end 12b are comprised so that the tubular body 12 provided so that it might open to the upper surface and lower surface of the hollow mold main body 11, respectively was comprised. The hollow mold body 11 and the tubular body 12 are both spiral steel pipes having a circular cross section made of a galvanized steel plate or an aluminum steel plate. Although not shown, groove-shaped reinforcing ribs may be spirally formed on the outer periphery of the hollow frame body 11 or the tubular body 12 as necessary.

  The upper end 12a and the lower end 12b of the tubular body 12 are cut along the outline of the hollow mold body 11, and are joined to the hollow mold body 11 so that no gap is generated. The joining of both members may be by welding, by fastening with screws or the like, or by a joint member used separately.

  The cross-sectional dimension of the hollow mold body 11 is set according to the dimension of the hollow portion 6 of the hollow floor slab bridge 1. On the other hand, the cross-sectional dimension of the tubular body 12 is set according to the diameter of the multivibrator 21 to be used and the aggregate size of the concrete, and generally about φ100 mm to φ150 mm is sufficient. In the section S, a plurality of tubular bodies 12 are arranged at predetermined intervals L in the extending direction of the hollow mold body 11. The predetermined interval L is preferably set to a size that can give vibration to the concrete between the two tubular bodies 12 adjacent to each other in accordance with the ability of the multivibrator 21 to be used.

  As shown in FIG. 5, the hollow mold 10 is fixed at a predetermined position at a position having a gap of a predetermined dimension in the height direction with respect to the mold 22 defining the lower surface of the hollow floor slab bridge 1. The Further, a known anti-lifting member 23 (see FIGS. 1 to 3) is attached to the hollow mold 10 in order to prevent it from floating during concrete placement.

  Thus, by providing the tubular body 12 opening on the upper surface and the lower surface of the hollow mold body 11, a through-hole 13 extending vertically is formed at the center in the width direction of the hollow mold 10. Therefore, when the hollow floor slab bridge 1 is constructed, the hollow mold 10 is disposed substantially horizontally at the predetermined position, and the concrete is placed to a position higher than the lower end 12b of the tubular body 12, as shown in FIG. The multivibrator 21 can be inserted into the through-hole 13 (inside the tubular body 12) in the placed state, and the concrete below the hollow mold 10 can be vibrated and directly compacted. Since the through-hole 13 extends vertically, a vibrator in which a hose is directly connected to the base end side of the vibration part 21a can be used when the concrete below the hollow mold 10 is compacted. .

  Thereafter, the hollow floor slab bridge 1 is constructed by placing concrete to a predetermined height. In the hollow floor slab bridge 1 constructed in this way, as shown in FIG. 6, pillars 7 in which concrete is filled in the tubular body 12 are formed in the cavity 6 at intervals L.

<First Modification>
Next, the 1st modification of the construction method of the hollow floor slab bridge 1 is demonstrated with reference to FIG. 5 and FIG. In this modification, as shown in FIG. 5, the multivibrator 21 is inserted into the through-hole 13 (inside the tubular body 12) in a state where the concrete is cast to a position higher than the lower end 12 b of the tubular body 12, After the concrete below the mold 10 is vibrated and compacted directly, a cylindrical embedding material 14 having an outer diameter substantially the same as the inner diameter of the tubular body 12 is inserted into the tubular body 12 to form a tubular shape. The opening is closed at the upper end 12 a of the body 12.

  As the material of the embedding material 14, a lightweight and easily cut material such as foamed plastic is suitable. The concrete swells at the lower end 12 b of the tubular body 12 and enters the inside of the through-hole 13, so that when the embedded material 14 is inserted into the tubular body 12, the embedded material 14 is removed from the upper surface of the hollow mold 10. When projecting, the projecting portion is cut and the opening is closed at the upper end 12a of the tubular body 12, and then concrete is cast to a predetermined height to construct the hollow floor slab bridge 1.

  By constructing the hollow floor slab bridge 1 in this way, it is possible to prevent the concrete from flowing into the tubular body 12 from the upper opening, so that an increase in the volume of the concrete can be suppressed.

<Second Modification>
Furthermore, the 2nd modification of the construction method of the hollow floor slab bridge 1 is demonstrated with reference to FIG. 5 and FIG. In this modification, as shown in FIG. 5, the multivibrator 21 is inserted into the through-hole 13 (inside the tubular body 12) in a state where the concrete is cast to a position higher than the lower end 12 b of the tubular body 12, After the concrete below the mold 10 is vibrated and directly compacted, the opening is closed at the upper end 12 a of the tubular body 12 using the lid member 15. Thereafter, concrete is cast to a predetermined height, and the hollow floor slab bridge 1 is constructed.

  The lid member 15 may be formed of the same material as the material of the hollow mold body 11 or the tubular body 12, or may be formed of another material. Further, in order to prevent the lid member 15 from coming off, it may be fixed to the hollow frame body 11 or the tubular body 12 with an adhesive, a screw, a clip or the like.

  Also by constructing the hollow floor slab bridge 1 in this way, it is possible to prevent the concrete from flowing into the tubular body 12 from the upper opening, and thus it is possible to suppress an increase in the volume of the concrete.

  This is the end of the description of specific embodiments, but the present invention is not limited to these embodiments. For example, in the said embodiment, although the hollow formwork 10 which concerns on this invention is applied to construction of the hollow floor slab bridge 1, you may apply to construction of other hollow concrete structures. Moreover, in the said embodiment, although the hollow mold main body 11 is a cylindrical shape, the cylinder shape of an ellipse or an ellipse cross section may be sufficient. In addition, the tubular body 12 has a circular cross section in the above-described embodiment. However, as long as it is tubular, the tubular body 12 may have a rectangular or polygonal cross section as well as an ellipse or an oval cross section. In addition, the specific shape, arrangement, quantity, and the like of each member can be changed as appropriate without departing from the spirit of the present invention. In addition, the hollow mold 10 and the components of the hollow concrete structure and the building steps of the hollow concrete structure according to the present invention shown in the above embodiment are not necessarily all necessary, and at least depart from the spirit of the present invention. As long as it is not, selection can be made as appropriate.

1 Hollow floor slab bridge (hollow concrete structure)
6 hollow part 10 hollow form 11 hollow form body 12 tubular body 12a upper end 12b lower end 21 multivibrator

Claims (3)

A hollow mold for forming a hollow portion by embedding in a concrete when constructing a hollow concrete structure,
A cylindrical hollow mold body disposed substantially horizontally at a predetermined position;
A hollow mold frame comprising a tubular body provided inside the hollow mold frame body and having an upper end and a lower end opened to an upper surface and a lower surface of the hollow mold body, respectively. A method for constructing a hollow concrete structure,
A hollow mold frame provided with a tubular body inside the hollow mold body is prepared so that the upper end and the lower end thereof open to the upper surface and the lower surface of the cylindrical hollow mold body, respectively. Placing it approximately horizontally in position;
A step of inserting a vibrator into the inside of the tubular body in a state in which the concrete is placed to a position higher than a lower end of the tubular body, and compacting the concrete below the hollow formwork, Construction method for concrete structures.   The method for constructing a hollow concrete structure according to claim 2, further comprising a step of closing the opening at an upper end of the tubular body after the step of compacting the concrete below the hollow mold.

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