JP2015172299A - Opening reinforcement structure in rc beam - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an opening reinforcement structure in RC beams, including a footing beam capable of reinforcing an opening without an excessive increase in reinforcement materials in a beam width direction, and of forming a larger opening without heightening the beam height.SOLUTION: The RC beam 20 has an opening 1 penetrating from a front face to a rear face, where a top reinforcement 2, a bottom reinforcement 3 and stirrups 4 are embedded in concrete 5. A pair of closed type reinforcement bars 6A, 6B in a trapezoidal shape are arranged to have vertical symmetry and surround the opening 1, and are embedded in the concrete 5. The closed type reinforcement bars 6A, 6B may be in a triangular shape.

Description

  The present invention relates to an opening reinforcement structure in an RC beam such as a foundation beam having a large opening such as a through hole.

  In buildings such as medium- and high-rise houses, office buildings, and distribution facilities, it may be necessary to provide large openings that allow people to pass through RC beams such as foundation beams. For example, in a building where the first floor is in a pit format, it is necessary to periodically inspect the inside of the pit. As a countermeasure, an opening through which an operator for inspection passes may be provided in the foundation beam so as to enter an area separated by the foundation beam.

  When an opening is provided in the foundation beam, the shear strength and rigidity decrease as the diameter of the opening increases, so the beam length must be increased. The RC standard of the Architectural Institute of Japan stipulates that the recommended diameter of the opening of the foundation beam is up to 1/3 of the beam. Therefore, when a large opening is required, the RC beam must be raised to the extent that it is necessary, and it is necessary to make it an uneconomical beam that is higher than that required for building structural calculations. is there. In the case of foundation beams, the excavation amount of the ground, the amount of residual soil disposal, and the amount of formwork increase with the increase in the height of the beam, leading to longer construction periods and higher costs.

  As a technique for reinforcing the opening of such an RC beam, there are many techniques for arranging various reinforcing bars such as diagonal reinforcing bars, opening reinforcing bars, vertical horizontal reinforcing bars, vertical reinforcing bars and the like around the opening. It has been proposed (for example, Patent Documents 1 to 3). 7A and 7B are a front view and a cross-sectional view of an example thereof. When these various reinforcing bars 31 to 35 are combined, there are some that are simply arranged so as to cross each other, and some that reinforce each other's reinforcing bars using dedicated metal fittings. In addition, as the shape of the reinforcing bars 31 to 35, instead of the diagonal reinforcing bars, a circular or polygonal closed bar arrangement or a steel material other than a reinforcing bar such as a steel pipe and a flat bar is processed. Some are used as reinforcement.

JP-A 63-297657 Japanese Utility Model Publication No. 05-083129 JP 2002-266470 A

  The above-mentioned various reinforcing bars (diagonal reinforcing bar 31, opening reinforcing bar 35, vertical horizontal reinforcing bar 32, vertical reinforcing bar 33, etc.) are often arranged so as to cross each other around the opening 1 and the beam width. The bar arrangement in the direction becomes overcrowded, which may cause obstacles in concrete placement. Reinforcement bars are made by using circular or polygonal closed bar arrangements instead of diagonal reinforcement bars, steel pipes, and materials other than reinforcing bars such as flat bars (steel materials). However, it is hard to say that the bar arrangement has been made in consideration of the concrete anchoring effect of these closed bar arrangements and the stress transmission with the upper and lower horizontal reinforcement bars.

The present invention solves the above-mentioned problems, and the opening can be shear-reinforced so that the reinforcing material arranged around the opening does not become overcrowded in the beam width direction, and a large opening can be formed without increasing the beam stake. It aims at providing the opening part reinforcement structure in RC beam which can be formed.
Another object of the present invention is to improve the effect of fixing a reinforcing material arranged around an opening to concrete.

In the RC structure of the RC beam according to the present invention, the top beam, the bottom beam, and the stirrup are embedded in the concrete, and the RC beam having an opening penetrating the front and rear surfaces.
A pair of trapezoidal or triangular reinforcing reinforcing bars in an upright posture are vertically symmetrical with each other, arranged at positions surrounding the openings, and embedded in the concrete.
The above “upright posture” refers to a posture without inclination.

According to this configuration, the trapezoidal or triangular pair of closed reinforcing bars are vertically symmetrical with each other and arranged at positions surrounding the openings, so that the openings of the RC beam can be shear-reinforced and a reduction in rigidity can be avoided. . The horizontal side portion of the closed reinforcing bar also serves as a horizontal reinforcing bar positioned above and below the opening. In addition, the oblique side portion of the closed reinforcing bar serves as an oblique reinforcing bar in the conventional example, and by arranging a pair of closed reinforcing bars vertically symmetrically, the opening is surrounded by a hexagonal shape and restrained. Can be expected. Moreover, since it is a closed-type reinforcing bar, the end fixing of the hypotenuse is secured by the horizontal side pre-connected to the hypotenuse, so that the fixing property to the concrete is good, There is no need to consider the fixing length when using a lap joint. For these reasons, the cost DN of the reinforcing bars can be achieved.
The pair of closed reinforcing bars are positioned on the same vertical plane along the longitudinal direction of the RC beam so that no overlapping joints are generated, and the reinforcing material arranged around the opening is not overcrowded in the beam width direction. It is possible to reinforce the opening and to prevent the reinforcing material from interfering with the concrete placement. Therefore, it is excellent also in workability, performing opening part reinforcement.

In the present invention, the pair of closed reinforcing bars are trapezoidal, and the pair of trapezoidal closed reinforcing bars is formed between the horizontal sides positioned on the upper side and the horizontal sides positioned on the lower side. The height positions may be aligned with each other.
When the closed reinforcing bar has a trapezoidal shape, two horizontal sides serving as horizontal reinforcing bars are obtained above and below the opening by the pair of closed reinforcing bars, respectively, and can be firmly reinforced. In addition, by arranging the height positions of the horizontal side portions located on the upper side and the horizontal side portions located on the lower side to be aligned with each other, the bar arrangement is simply gathered.

In this invention, the pair of closed reinforcing bars are trapezoidal, and the pair of closed reinforcing bars of the trapezoidal shape has a horizontal side that is a long side to a horizontal side that is a short side on the outer peripheral side. You may arrange | position so that it may protrude and may become a star shape as a whole.
Also in this case, two horizontal sides each serving as a horizontal reinforcing bar are obtained above and below the opening, respectively, and can be firmly reinforced. In addition, the two horizontal side portions that also serve as the horizontal reinforcing bars are shifted from each other and dispersed, and the pair of closed reinforcing bars are arranged in a star shape as a whole. It will be distributed over and reinforcement will be made and reinforcement can be made more effectively.

In the present invention, the pair of closed reinforcing bars are in a triangular shape with one side being a horizontal side, and the pair of triangular closed reinforcing bars is the horizontal side of one of the closed reinforcing bars. Therefore, the corners of the other closed reinforcing bar may protrude to the outer peripheral side to form a star shape as a whole.
In the case of this configuration, since the shape of the closed reinforcing bar is triangular, it is simpler than the case where it is trapezoidal. Also in this configuration, since the pair of closed reinforcing bars are arranged in a star shape as a whole, the reinforcing bars are distributed over a wide range to reinforce the reinforcing bars and can be effectively reinforced.

In the opening reinforcing structure of the present invention, a plurality of pairs of the closed type reinforcing bars are arranged side by side in the front-rear width direction, and a pair of shear reinforcing bars formed by facing a pair of shear reinforcing bars face each other. The two reinforcing bar portions above the openings of each pair of the plurality of closed reinforcing bar pairs in a range surrounded by the pair of shear reinforcing bars on the upper side of the openings, Two rebar portions below the openings of each pair of the plurality of closed reinforcing bar pairs in a range surrounded by the pair of shear reinforcing bars on the lower side of the opening through the upper end bars And the lower end line may be inserted.
In the case of this configuration, since the pair of divided reinforcing bars are opposed to each other, even if the closed reinforcing bar is post-installed, the closed reinforcing bar pair is within the range surrounded by the shear reinforcing bar pair. It can arrange | position in the state which penetrated the horizontal side part. The horizontal sides of the pair of shear reinforcement bars are fixed by the principle of the lap joint, so that it is not particularly necessary to join them.

The opening reinforcing structure in the RC beam of the present invention is an RC beam having an opening that penetrates through the front and rear surfaces in which the upper end, the lower end, and the stirrup are embedded in the concrete. Since a pair of triangular closed reinforcing bars are vertically symmetrical with each other and arranged at positions surrounding the openings and embedded in the concrete, the reinforcing material arranged around the openings is overcrowded in the beam width direction. Thus, the opening can be shear-reinforced so that a large opening can be formed without increasing the beam. Moreover, the fixing effect to the concrete of the reinforcing material arrange | positioned around an opening part can be improved.
In particular, when the RC beam is a foundation beam, an increase in the amount of excavation of the ground, the amount of residual soil disposal, and the amount of formwork is avoided due to the effect that a large opening can be formed without increasing the height of the beam of the present invention. This can shorten the construction period and reduce costs.

(A) is the longitudinal cross-sectional view which shows the opening part reinforcement structure in RC beam according to 1st Embodiment of this invention, (B) is the cross-sectional view which cut the RC beam by the opening part. It is a front view of a pair of closed type reinforcement in the opening part reinforcement structure. (A) is a front view which shows the state before arrange | positioning the pair of closed type reinforcement bars in the opening part reinforcement structure, (B) is a side surface of a pair of U-shaped shear reinforcement bars arranged in the opening part reinforcement structure FIG. 4C is a perspective view showing a state in which the same pair of shear reinforcement bars are overlapped and joined. (A) is a side view showing another example of a pair of shear reinforcement bars, (B) is a perspective view showing a state where the pairs of shear reinforcement bars are overlapped and joined, and (C) is a further illustration of a pair of shear reinforcement bars The side view which shows another example, (D) is a perspective view which shows the state which piled up and joined the pair of the same shear reinforcement. (A) is the longitudinal cross-sectional view which shows the opening part reinforcement structure in RC beam concerning other embodiment of this invention, (B) is the cross-sectional view which cut the RC beam by the opening part. (A) is the longitudinal cross-sectional view which shows the opening part reinforcement structure in RC beam according to further another embodiment of this invention, (B) is the cross-sectional view which cut the RC beam by the opening part. (A) is front sectional drawing of a prior art example, (B) is the cross-sectional view.

  A first embodiment of the present invention will be described with reference to FIGS. FIG. 1A shows a longitudinal cross-sectional view of an RC beam to which the opening reinforcement structure of this embodiment is applied, and FIG. 1B shows a cross-sectional view of the RC beam cut at the opening. An RC beam 20 shown in FIG. 1 (A) has an opening 1 having a circular cross section penetrating through the front and rear surfaces in a concrete 5 portion, and upper and lower main bars 2 as upper and lower main bars arranged along the axial direction. The lower end bars 3 and the ribs 4 arranged so as to surround the upper end bars 2 and the lower end bars 3 are embedded in the concrete 5 while avoiding the opening 1. A plurality of upper end bars 2 and lower end bars 3 are arranged in the horizontal direction, for example, 2 to 6 bars. The RC beam 20 is a foundation beam in a building in which the first floor is in a pit form in this example, and the opening 1 is a through hole. The RC beam 20 is not limited to a foundation beam but may be a superstructure beam.

In the concrete 5, as a reinforcing material for reinforcing the opening 1, a pair of trapezoidal closed reinforcing bars 6A and 6B as shown in FIG. Embedded. The pair of closed reinforcing bars 6A and 6B are arranged at the same height so that the horizontal sides 6Aa, 6Ab, 6Ba, and 6Bb that are trapezoidal upper and lower bases overlap each other in the front-rear direction. Each of the closed reinforcing bars 6A and 6B is formed by bending one reinforcing bar into a trapezoid. As shown in FIG. 1B, a plurality of trapezoidal closed reinforcing bar pairs 6 are arranged side by side in the longitudinal direction of the beam cross section. As a material for the closed reinforcing bars 6A and 6B, it is desirable to use high-strength reinforcing bars (685 N / mm ² or more) from the viewpoint of reducing the size and weight. Further, above and below the opening 1, a pair of shear reinforcement bars 7A and 7B, each having a U-shape extending in the longitudinal width direction of the beam cross section as shown in FIG. 7 are arranged respectively. 3A is a front view showing the arrangement of the ribs 4 and the shear reinforcing bar pairs 7, and FIG. 3B is a cross-sectional view of the upper and lower shear reinforcing bar pairs 7 in FIG. 3A. The exploded view seen from the side is shown. A pair of U-shaped shear reinforcement bars 7A and 7B are arranged next to each other as shown in FIG. These U-shaped shear reinforcement bars 7A and 7B are fixed on the horizontal side by the principle of the lap joint.

Within the range surrounded by the upper and lower shear reinforcement pairs 7, the horizontal side portions 6Aa, 6Ab, 6Ba, 6Bb of the closed reinforcement bars 6A, 6B in the plurality of closed reinforcement pair 6 and the upper end The muscle 2 or the lower muscle 3 is inserted. In FIG. 2, the lower and upper sides of one closed reinforcing bar 6A are the lower horizontal side 6Ab and the upper horizontal side 6Aa, and the upper and lower sides of the other closed reinforcing bar 6B are the upper horizontal side. The side 6Ba and the lower horizontal side 6Bb. At locations where the horizontal side portions 6Aa, 6Ab, 6Ba, 6Bb of the closed reinforcing bars 6A, 6B are present, the upper and lower shear reinforcing bar pairs 7 are the horizontal sides that are the short sides of the closed reinforcing bars 6A, 6B. It is located within the range of the parts 6Aa and 6Bb. These shear reinforcing bar pairs 7 position the closed reinforcing bars 6A and 6B before the concrete placement with respect to the upper and lower reinforcing bars 2 and 3 together with the shear reinforcement. As described above, the shear reinforcing bar pair 7 is composed of a combination of a pair of shear reinforcing bars 7A and 7B that are not closed, so that even if the closed type reinforcing bars 6A and 6B are subsequently applied, they are surrounded by the shear reinforcing bar pair 7. The horizontal side portions 6Aa, 6Ab, 6Ba, 6Bb of the respective closed reinforcing bars 6A, 6B can be placed in the inserted range, which contributes to improvement in workability.
In addition, a deformed reinforcing bar is used for each of the upper reinforcing bars 2, the lower reinforcing bars 3, the stirrups 4, and the reinforcing bars.

According to this configuration, since the pair of trapezoidal closed reinforcing bars 6A and 6B are vertically symmetrical with each other and are arranged at positions surrounding the opening 1, respectively, the horizontal sides 6Aa, 6Ab, 6Ba and 6Bb serve as reinforcing reinforcing bars that also serve as the upper and lower horizontal reinforcing bars of the opening 1, and the hypotenuses of the respective closed reinforcing bars 6A and 6B play the same role as the diagonal reinforcing bars in the conventional example. The mold reinforcing bars 6A and 6B have an effect of enclosing and restricting the opening 1 in a hexagonal shape. Therefore, the opening part 1 of RC beam 20 can be shear-reinforced, and a rigidity fall can also be avoided.
Further, the closed reinforcing bars 6A and 6B are integrated, and the end fixing of the oblique sides is secured by the horizontal sides 6Aa, 6Ab, 6Ba, and 6Bb. A joint as in the case of fixing is eliminated, and the fixing property to the concrete 5 is also good. Therefore, it is not necessary to consider the fixing length in the case where the oblique side portion is a lap joint with the main reinforcing bars such as the upper and lower reinforcing bars 2 and 3. For these reasons, the cost DN of the reinforcing bars can be achieved.

  Further, the pair of closed reinforcing bars 6A and 6B are located on the same vertical plane along the longitudinal direction of the RC beam 20 so that a lap joint is not generated, and a reinforcing material disposed around the opening 1 is provided. The opening 1 can be reinforced so as not to become overly dense in the beam width direction, and the reinforcement material can be prevented from interfering with concrete placement. Therefore, it is excellent also in workability, performing opening part reinforcement.

  When the RC beam 20 is a foundation beam as in this example, the increase in the beam stake H is accompanied by an increase in the amount of excavation of the ground, the amount of residual soil disposal, and the amount of formwork, thereby extending the construction period and increasing costs. Therefore, the effect of obtaining a large opening without increasing the beam length H according to this embodiment is more effectively exhibited.

  In the numerical example, when the opening 1 having a diameter of 600 mm is provided as a through hole, the recommended value of the diameter of the opening is 1/3 of that of the beam in the conventional basic beam. It is necessary to use a 1800 mm beam. Therefore, even if a beam of about 1500 mm is sufficient in structural calculation, it is necessary to use a beam of 1800 mm, and it is necessary to construct a foundation beam that is 300 mm higher than the structural calculation value. When the trapezoidal closed reinforcing bars 6A and 6B are reinforced with the pair 6 as in the above-described embodiment, for example, when the beam length H of 1 / 2.5 of the opening 1 is improved, the opening 1 of 600 mm is obtained. Even when the beam is provided, the beam length H is only 1500 mm, and the difference from the beam length (1500 mm) necessary for the structural calculation is reduced. For this reason, it can be considered as the RC beam 20 of the economic reason H.

  4A and 4B show another configuration example of the shear reinforcement pair 7 in the embodiment. In this example, as shown in FIG. 4 (A), a groove-shaped shear reinforcement bar 17A that extends in the longitudinal width direction of the beam cross section and has hook portions 17Aa at both ends and is open on the upper side, and similarly, the width across the beam cross section. A groove-shaped shear reinforcement bar 17B extending in the direction and opening downward is opposed to each other vertically to constitute a shear reinforcement pair 17 as shown in FIG. 4B. The pair of groove-shaped shear reinforcement bars 17A and 17B are arranged adjacent to each other, and the shear reinforcement bar pair 17 is configured by being fastened by a bind line or joined by flare welding or the like. The groove-shaped shear reinforcing bar 17A opened on the upper side secures fixing by engaging the hook part 17Aa with the upper end reinforcing bar 2 or by engaging the horizontal side parts 6Aa and 6Bb of the closed reinforcing bars 6A and 6B. it can. The groove-shaped shear reinforcement bar 17B opened to the lower side is fixed by engaging the central straight line portion with the upper end reinforcement 2 or by engaging the horizontal side portions 6Aa and 6Bb of the closed reinforcement bars 6A and 6B. Can be secured.

  4C and 4D show still another configuration example of the shear reinforcing bar pair 7 in the embodiment. In this example, in the example of FIGS. 4 (A) and 4 (B), one of the pair of shear reinforcement bars 17A and 17B facing each other up and down is the same as one shear reinforcement bar 17A, and the other shear reinforcement bar 27B is used. The hook portions 27Ba extend from both ends of the straight portion, and the hook portions 27Aa and 27Ba of the respective shear reinforcing bars 27A are engaged with the upper and lower ends of the lower bar 3 or the upper bar 2 respectively.

  FIG. 5 shows another embodiment of the present invention. In this embodiment, in the first embodiment shown in FIGS. 1 to 4, the pair of trapezoidal closed reinforcing bars 6A and 6B are arranged such that the horizontal sides 6Ab and 6Ba having long sides become short sides. The side portions 6Bb and 6Aa protrude toward the outer peripheral side and are arranged in a star shape as a whole of the closed reinforcing bar pair 6. The inclination angle of the oblique sides of the closed reinforcing bars 6A and 6B with respect to the horizontal is, for example, 60 degrees. Further, horizontal reinforcing bars 29 are provided above and below the opening 1 and are provided from the opening 1 to both sides to appropriate positions in the beam longitudinal direction. The horizontal reinforcing bars 29 are not necessarily provided. The shear reinforcement bars are provided in the same manner as in the first embodiment, but in the example of FIG. 5, a shear reinforcement bar pair 27 shown in FIG. 4C is used. Instead of the shear reinforcing bar pair 27, the shear reinforcing bar pair 17 shown in FIG. 4B or the shear reinforcing bar pair 7 shown in FIG. 4A may be used. (Not shown) may be used. Other configurations are the same as those of the first embodiment shown in FIGS.

  In the case of this configuration, the upper two horizontal sides 6Aa and 6Ba, which also serve as horizontal reinforcing bars, and the lower two horizontal sides 6Ab and 6Bb are shifted from each other and dispersed. In addition, since the pair 6 of the closed reinforcing bars 6A and 6B is arranged in a star shape as a whole, the reinforcing bars are distributed over a wide range to reinforce the reinforcing bars, which can be reinforced more effectively.

  FIG. 6 shows still another embodiment of the present invention. 1-4, in the first embodiment shown in FIGS. 1 to 4, instead of the trapezoidal pair of closed reinforcing bars 6A and 6B, a triangular closed type in which one side is a horizontal side part 6Ca and 6Da. Reinforcing bars 6C and 6D are used. The pair of triangular reinforcing bars 6C and 6D is formed from the horizontal side parts 6Ca and 6Da of one closing type reinforcing bar 6C and 6D, and the corners 6Dd and 6Cd of the other closing type reinforcing bars 6C and 6D. Are arranged in a star shape as a whole of the closed reinforcing bar pair 6 protruding toward the outer peripheral side. Also in this example, the horizontal reinforcing bars 29 are provided in the same manner as in the example of FIG.

  The shear reinforcement bars are provided in the same manner as in the first embodiment, but in the example of FIG. 6, a shear reinforcement bar pair 27 shown in FIG. 4C is used. Instead of the shear reinforcing bar pair 27, the shear reinforcing bar pair 17 shown in FIG. 4B or the shear reinforcing bar pair 7 shown in FIG. 4A may be used. (Not shown) may be used. Other configurations are the same as those of the first embodiment shown in FIGS.

  In the case of this embodiment, the shape of the closed reinforcing bars 6C and 6D is a triangle, so that it is simpler than the case of the trapezoidal shape as in the above embodiments. Also in this configuration, since the closed reinforcing bar pair 6 of the pair of closed reinforcing bars 6C and 6D is arranged in a star shape as a whole, it will be distributed over a wide area to reinforce the reinforcing bar. Can be effectively reinforced.

DESCRIPTION OF SYMBOLS 1 ... Opening part 2 ... Upper end reinforcement 3 ... Bottom end reinforcement 4 ... Stirrup reinforcement 5 ... Concrete 6A, 6B, 6C, 6D ... Closed reinforcement reinforcement 6Aa, 6Ab, 6Ba, 6Bb ... Horizontal side part 6 ... Pair of closure reinforcement 7A, 7B ... Shear reinforcement bar 7 ... Shear reinforcement bar pair 17A, 17B ... Shear reinforcement bar 17 ... Shear reinforcement bar pair 20 ... RC beam 27A, 27B ... Shear reinforcement bar 27 ... Shear reinforcement bar pair

Claims (5)

In RC beams with an upper end, a lower end, and a stirrup embedded in the concrete and having openings that penetrate through the front and rear surfaces,
An opening in an RC beam, wherein trapezoidal or triangular closed reinforcing bars in an upright position are vertically symmetrical with each other and are arranged at positions surrounding the opening and embedded in the concrete. Reinforced structure.   2. The opening reinforcing structure according to claim 1, wherein the pair of closed reinforcing bars are trapezoidal, and the pair of trapezoidal closed reinforcing bars includes the horizontal sides positioned on the upper side and the lower side. The opening part reinforcement structure which aligned the height position of the horizontal side parts located in each other.   2. The opening reinforcing structure according to claim 1, wherein the pair of closed reinforcing bars are trapezoidal, and the pair of trapezoidal closed reinforcing bars extends from a horizontal side which is a long side to a short side. The opening side reinforcement structure which becomes the star shape as a whole by the horizontal side part which protrudes to the outer peripheral side.   2. The opening reinforcing structure according to claim 1, wherein the pair of closed reinforcing bars has a triangular shape in which one side is a horizontal side, and the pair of triangular closed reinforcing bars is one of the closed reinforcing bars. An opening portion reinforcing structure in which a corner portion of the other closed type reinforcing bar protrudes from the horizontal side portion of the mold reinforcing bar to the outer peripheral side to form a star shape as a whole.   5. The opening reinforcing structure in the RC beam according to claim 1, wherein a plurality of pairs of the closed reinforcing bars are arranged side by side in the front-rear width direction, and are divided into a pair of shear reinforcements. A pair of shear reinforcement bars each having a line facing each other are respectively arranged above and below the opening, and each of the pairs of closed reinforcement bars in a range surrounded by the pair of shear reinforcement bars on the upper side of the opening. A pair of the plurality of closed reinforcing bars is inserted into a range surrounded by a pair of shear reinforcing bars below the opening, and the two reinforcing bars above the opening of the pair are inserted through the upper end bars. The opening reinforcement structure in RC beam which penetrated two rebar parts below the opening of each pair in, and the lower end reinforcement.

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