JP7245758B2 - Column-beam frame - Google Patents

Description

The present invention relates to a reinforced concrete column-beam frame.

Conventionally, in the structural design of a reinforced concrete column-beam frame, the yield hinge of the beam is designed to be formed at the interface between the beam end and the column-beam joint (column-beam joint). However, if the difference in bending strength between the column and the beam is small, both the beam main reinforcement and the column main reinforcement may yield in the column-to-beam joint, and the expected seismic performance may not be obtained.

Non-Patent Literature 1 discloses a method of hinge relocation by arranging additional main reinforcing bars having mechanical anchoring hardware on the beam end side of a reinforced concrete beam as the second stage main reinforcing bars. The term "hinge relocation" as used herein refers to moving the position of the yield hinge from the boundary surface between the beam end and the beam-to-column joint toward the center of the beam in order to prevent damage to the beam-to-column joint.
In the beam of Non-Patent Document 1, cracks are concentrated at the yielding hinge position, but when the beam undergoes a large deformation, damage to the beam ends increases.
In addition, in Patent Document 1, in a reinforced concrete beam, an additional reinforcing bar is formed by integrating the upper reinforcing bar and the lower reinforcing bar arranged at the double-bar position of the upper and lower main bars through an intermediate bent portion. , a method of controlling the yield hinge position of the beam, in which the additional reinforcing bars are arranged separately on the left and right sides of the beam across the center position, is shown.
In the beam of Patent Document 1, it was necessary to perform a plurality of bending processes on the additional reinforcing bars at delicate angles, which required a great deal of cost and labor.

JP 2018-145595 A

Yukitaka Ota et al.: Experimental Study on RC Beam Forming Beam End Hinge Relocation Mechanism Using Y-Shaped Reinforcement (No. 1 Experiment Summary), Summaries of Technical Papers of Annual Meeting of Architectural Institute of Japan, Structure IV, pp.237-238, 2018 September

An object of the present invention is to provide a reinforced concrete column-to-beam frame structure in which the bending yield hinge position of the beam can be moved closer to the center of the beam than in the past to reduce damage to the column-to-beam joints during an earthquake. .

As a column-beam frame having a hinge relocation mechanism, the present inventors arranged the first stage main reinforcement, the second stage main reinforcement, and the shear reinforcement on the beam, and arranged the first stage main reinforcement and the second stage main reinforcement on the beam end side. By arranging the upper and lower restraint bars surrounding the main rebar, the breaking strength of the concrete when it is crushed increases on the beam end side. This development was carried out with a focus on the ability to reduce damage to the body.
The beam-to-column structure of the first invention (for example, the beam-to-column structure 1 described below) includes a reinforced concrete column (for example, a column 10 to be described later) and a reinforced concrete beam (for example, a beam to be described later) joined to the column. 20), wherein the beams are first-stage main reinforcements (for example, first-stage beam top reinforcements 30A and first-stage beam bottom reinforcements 40A, which will be described later) arranged on the upper and lower end sides of the beams; , the second stage main reinforcements (for example, the second stage beam top reinforcements 30B and 30C and the second stage beam bottom reinforcements 40B and 40C described later) arranged inside the first stage main reinforcements, the first stage main reinforcements and the second stage reinforcements and a shear reinforcing bar (for example, a stirrup 50 described later) provided surrounding the main reinforcement, and all or part of the second stage main reinforcement (for example, a second stage beam upper end reinforcement 30C described later, the second stage The beam bottom reinforcement 40C) is a cut-off reinforcement arranged only on the end side of the beam, and a fixing hardware (for example, a fixing hardware 60 described later) is provided at the tip of the cut-off reinforcement. , on the end side of the beam, there are an upper restraining bar (for example, an upper restraining bar 51 to be described later) surrounding the first stage main reinforcement and the second stage main reinforcement of the beam, and a first stage beam main reinforcement below the beam. and a lower restraint muscle (for example, a lower restraint muscle 52 described later) surrounding the second stage main reinforcement.

Here, the cut-off bar may be the same reinforcing bar as the through bar, or may have a larger diameter and higher strength than the through bar.
According to this invention, since the cut-off reinforcement is provided only on the end side of the beam, the number of beam reinforcements on the end side of the beam is larger than that on the center side of the beam. Therefore, since the bending yield hinge position of the beam moves to the center side of the beam compared to the conventional one, cracks in the vicinity of the bending yield hinge are suppressed from reaching the column-to-beam joint, thereby preventing the column-to-beam joint from breaking. The seismic performance of the column-to-beam joints can be sufficiently secured.
In addition, all or part of the second stage main reinforcement is used as a cutoff reinforcement, and a fixing hardware is provided at the tip of this cutoff reinforcement, so that the upper and lower reinforcements are placed at the center of the beam as in the additional reinforcement of Patent Document 1. There is no need to perform multiple bending processes at subtle angles toward the sides. In addition, since the cut-off reinforcement does not extend to the beam center side, it can be made shorter than the additional reinforcement of Patent Document 1, and the cost is low.
In addition, the first stage main reinforcement and the second stage main reinforcement were double surrounded by the upper and lower restraint muscles in addition to the shear reinforcement. Therefore, since the breaking strength of the concrete when it is crushed increases on the beam end side, it is possible to reduce the damage to the concrete body of the beam end due to the compressive force generated at the upper and lower ends of the beam end.

The beam-to-column structure of the second invention includes a reinforced concrete column (for example, a column 10 described later) and a reinforced concrete beam with a floor slab joined to the column (for example, a beam 20A described later). A column-beam frame (for example, a column-beam frame 1 to be described later), wherein the beams are first stage main reinforcements (for example, the first stage beam upper end reinforcements 30A to be described later, first stage beam lower ends) arranged on the upper and lower end sides of the beams. reinforcement 40A), second-stage main reinforcements arranged inside the first-stage main reinforcement (for example, second-stage beam top reinforcements 30B and 30C and second-stage beam bottom reinforcements 40B and 40C, which will be described later), and the first-stage main reinforcements. and a shear reinforcing bar (for example, a stirrup 50 to be described later) provided surrounding the second-tier main bar, and all or part of the second-tier main bar (for example, a second-tier beam upper end bar 30C to be described below) , second-stage beam bottom reinforcement 40C) is a cut-off reinforcement arranged only on the end side of the beam, and a fixing hardware (for example, a fixing hardware 60 described later) is attached to the tip of the cut-off reinforcement. A lower restraining bar (for example, a lower constraining bar 52 described later) is provided on the end side of the beam, surrounding the first stage beam main reinforcement and the second stage main reinforcement on the lower side of the beam. characterized by

According to this invention, as in the above-described first invention, cut-off bars are provided only on the end side of the beam, so the bending yield hinge position of the beam moves to the center side of the beam more than in the conventional art. By suppressing cracks in the vicinity of the bending yield hinge from reaching the beam-to-column joint, sufficient seismic performance of the beam-to-column joint can be ensured.
In addition, all or part of the second stage main reinforcement is used as a cutoff reinforcement, and a fixing hardware is provided at the tip of this cutoff reinforcement, so that the upper and lower reinforcements are placed at the center of the beam as in the additional reinforcement of Patent Document 1. There is no need to perform multiple bending processes at subtle angles toward the sides. In addition, since the cut-off reinforcement does not extend to the beam center side, it can be made shorter than the additional reinforcement of Patent Document 1, and the cost is low.
In addition, the first stage main reinforcement and the second stage main reinforcement were doubly surrounded by the lower restraining reinforcement in addition to the shear reinforcement. Therefore, since the breaking strength of the concrete at the time of crushing increases at the lower end side of the beam end, it is possible to reduce damage to the concrete body at the beam end due to the compressive force generated at the lower end of the beam end.
Also, since the floor slab is provided on the beam, the floor slab bears the compressive force together with the beam. Therefore, damage to the beam can be sufficiently suppressed even if the upper restraining muscle is omitted.

In the column-to-beam frame of the third invention, on the end side of the beam, all or part of the shear reinforcing bars are arranged in contact with each other to form binding bars (for example, binding bars 53 to be described later). It is characterized by

According to the present invention, all or part of the shear reinforcing bars are bundled into a plurality of bundled bars on the end side of the beam, so that many shear reinforcing bars can be arranged on the end side of the beam. Therefore, since the concrete body is more constrained on the beam end side, the breaking strength of the concrete when it is crushed increases, and damage to the concrete body of the beam due to the compressive force generated at the upper and lower ends of the beam end is reduced. can.

ADVANTAGE OF THE INVENTION According to this invention, the bending yield hinge position of a beam can be moved to the center part side of a beam rather than before, and it can reduce the damage of the column-to-beam joint part at the time of an earthquake.

1 is a side view of a beam-column structure according to an embodiment of the present invention; FIG. 2A and 2B are sectional views of the beam shown in FIG. 1; FIG. It is a figure which shows the structure of the reinforced concrete beam test body which concerns on the Example of this invention. FIG. 2 is a side view of a force applying device used for a force applying test of a reinforced concrete beam specimen; It is a figure which shows the test result of a load test. FIG. 4 is a side view showing the state of the surface of the reinforced concrete beam test body after completion of the loading test; It is a side view of the beam-column structure according to the modification of the present invention.

The present invention is a column-beam frame structure comprising reinforced concrete columns and reinforced concrete beams joined to the columns. This is a hinge relocation structure in which closed reinforcing bars (upper and lower restraining bars) surround the eye main bars and double the beam main bars. Specifically, in the beams of the column-beam frame, fixation metal fittings are attached to the ends of some of the second stage main rebars to make cutoff rebars with fixation metal fittings, and the section from the beam end surface to the tip of the cutoff rebars is the first stage It is characterized by arranging closed reinforcing bars (upper and lower restraining bars) so as to surround the main bars and the second stage main bars.
An embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a longitudinal sectional view of a beam-column structure 1 according to an embodiment of the present invention. 2(a) is a sectional view taken along line AA of the beam-column frame 1 in FIG. 1, and FIG. 2(b) is a sectional view taken along line BB of the beam-column frame 1 in FIG.
The column-beam frame structure 1 includes reinforced concrete columns 10 and reinforced concrete beams 20 joined to column-beam joints 11 of the columns 10 . As shown in FIG. 2, the floor slab is not joined to this beam 20 .
The beam 20 includes upper beam reinforcements 30A, 30B, 30C and lower beam reinforcements 40A, 40B, 40C arranged in two stages, and predetermined Stirrups 50 as shear reinforcing bars provided at intervals, upper restraining bars 51 provided at predetermined intervals on the end side of the beam 20 and surrounding the beam upper end muscles 30A to 30C, and on the end side of the beam 20 It includes a lower restraining muscle 52 provided to surround the beam lower end reinforcements 40A to 40C, and a bundling muscle 53 arranged in contact with two stirrups 50 on the end side of the beam 20. - 特許庁

Specifically, the beam top reinforcements 30A to 30C are four beam top reinforcements 30A as upper first stage main reinforcements, and upper beam top reinforcements 30A as second stage main reinforcements arranged below and outside the beam top reinforcement 30A. It is composed of two upper beam reinforcements 30B and two upper beam upper reinforcements 30C as second-stage main reinforcements arranged below and inside the beam top reinforcements 30A.
The beam bottom reinforcements 40A to 40C are four beam bottom reinforcements 40A as lower first stage main reinforcements and two beams as lower second stage main reinforcements arranged above and outside the beam bottom reinforcements 40A. It is composed of a bottom reinforcement 40B and two beam bottom reinforcements 40C as second-stage main reinforcements located above and inside the beam bottom reinforcement 40A.
The beam top reinforcements 30A and 30B and the beam bottom reinforcements 40A and 40B are through reinforcements arranged from the end portion side (the column-to-beam joint portion 11 side) of the beam 20 to the center portion side. On the other hand, the beam upper end reinforcement 30C and the beam lower end reinforcement 40C are cutoff reinforcements arranged only on the end side of the beam 20 (on the side of the column-to-beam joint 11).
Fixing hardware 60 that spreads like a brim is provided at the tip of the beam top reinforcement 30C and the beam bottom reinforcement 40C, which are cut-off reinforcements.

The upper restraining reinforcement 51 is provided surrounding the first stage beam top reinforcement 30A and the second stage beam top reinforcements 30B and 30C. The lower restraint muscles 52 are provided surrounding the first stage beam bottom reinforcement 40A and the second stage beam bottom reinforcements 40B and 40C.

A bending moment distribution diagram of the beam 20 during an earthquake is shown in FIG.
Let _Muhr be the ultimate bending strength calculated by the upper beam reinforcements 30A and 30B and the lower beam reinforcements 40A and 40B, and _Muf be the ultimate bending strength calculated by the upper beam reinforcements 30A to 30C and the lower beam reinforcements 40A to 40C. . Further, let p be the end surface of the beam 20 on the side of the beam end, that is, the position of the side surface of the column 10, and let q be the position of the tip surface of the fixing metal fitting 60. As shown in FIG.
As shown in FIG. 1, at the position q of the beam 20, the bending moment M _uhrf during an earthquake reaches the ultimate bending strength M _uhr , but at the position p of the beam 20, the bending moment M _uhrf during an earthquake reaches the ultimate bending strength M _uf is not reached. Therefore, the beam 20 yields at position q, and this position q is the position where the bending yield hinge occurs.

[Example]
As an example, two specimens of reinforced concrete beams as shown in Table 1 below were produced and a load test was conducted. Among these, the test body 1 is the one in which the beam upper end reinforcement, the beam lower end reinforcement, the stirrup, and the bundling reinforcement to which the fixing hardware is attached are arranged. The test body 2 has a structure similar to that of the beam shown in FIG.

That is, as shown in FIG. 3(a), the shape of the test specimen was rectangular in cross section, the beam width was 300 mm, the beam height was 450 mm, the internal length of the test section was 2250 mm, and the shear span ratio (a/D) was 2.5 mm. 5. In addition, as shown in FIG. 3B, the dimension of the mechanical fixing (fixing hardware) in the specimen from the side of the column was set to 225 mm, which is 1/2 of the beam height.
The beam main reinforcement used as the through reinforcement was set to D19 (SD490) for both the first and second stages, and the beam main reinforcement used as the cutoff reinforcement was set to D22 (SD490). Also, the bending margin (M _uf /M _uhrf ) was set to 1.14, reflecting the results of the material test.

A force application test was conducted using a force application device as shown in FIG. FIG. 5 shows the test results of the force application test, showing the relationship between the shear force applied to the specimen by the force application device and the deformation (member angle R) of the specimen. FIG. 6 is a side view showing the state of the surface of the specimen after the completion of the force application test. 5(a) and 6(a) are the test results of the load test for the specimen 1, and FIGS. 5(b) and 6(b) are the test results of the load test for the specimen 2. This is the result.
As shown in FIG. 5, in specimen 1, the shear force did not increase after the shear force reached the calculated value of bending yield strength, but in specimen 2, the shear force reached the calculated value of bending yield strength. After that, an increase in yield strength was also observed.
In addition, as shown in Fig. 6, in Test Specimen 1, since the top and bottom restraints were not provided, the concrete peeled off at the ends of the beams, and damage due to shear cracks occurred in the same way as beams with normal bar arrangement. is becoming more intense. On the other hand, in Test Specimen 2, slight spalling of concrete was confirmed near the beam end surface, but by arranging the upper and lower end restraining bars, the spalling of concrete at the beam end was reduced and the shear was reduced. Damage caused by cracks is also reduced.
Therefore, from FIGS. 5 and 6, it was confirmed that by providing the upper end restraining bar and the lower end constraining bar, the degree of restraint of the concrete body at the ends of the test body can be increased, and damage to the test body can be reduced.

According to this embodiment, there are the following effects.
(1) Since the cut-off reinforcements 30C and 40C are provided only on the end side of the beam 20, the number of beam reinforcements on the end side of the beam 20 is greater than that on the center side of the beam 20. Therefore, since the bending yield hinge position of the beam 20 moves to the beam central part side than conventional, the crack near the bending yield hinge is suppressed from reaching the column-to-beam joint 11, and the column-to-beam joint 11 is prevented from breaking. Therefore, the seismic performance of the column-to-beam joint 11 can be sufficiently secured.
In addition, since the beam upper end reinforcement 30C and the beam lower end reinforcement 40C are used as cutoff reinforcements, and the fixing hardware 60 is provided at the tips of the cutoff reinforcements, the upper and lower reinforcements are placed at the center of the beam like the additional reinforcements of Patent Document 1. There is no need to perform multiple bending processes at subtle angles toward the part side. Moreover, since the beam upper end reinforcement 30C and the beam lower end reinforcement 40C do not extend to the center side of the beam unlike the additional reinforcing bars of Patent Document 1, the material cost of the reinforcing bars can be saved.

(2) The first stage beam top reinforcement 30A and the second stage beam top reinforcements 30B and 30C are doubly surrounded by the upper restraining muscles 51 in addition to the stirrups 50, and the first stage beam bottom reinforcement 40A and the second stage beam bottom reinforcement 40B, 40C were doubly surrounded by lower restraint muscles 52 in addition to the stirrups 50 . Therefore, since the breaking strength of the concrete when it is crushed increases on the end portion side of the beam 20, it is possible to reduce damage to the concrete body of the beam due to the compressive force generated at the upper and lower ends of the beam end portion.
In addition, the upper restraining muscle 51 and the lower restraining muscle 52, which are closed-type reinforcing muscles, may be smaller in diameter than the beam upper end muscles 30A to 30C and the beam lower end muscles 40A to 40C, and the stirrup 50, which is a shear reinforcing muscle, may be used. The same processing time is required. Therefore, there is no problem in workability, and the damage to the concrete body due to the compressive force generated at the upper and lower ends of the beam ends can be reduced at low cost.

(3) Two shear reinforcements 50 are placed in contact with each other near the tips of the second-stage beam top reinforcement 30C and the second-stage beam bottom reinforcement 40C to form the bundling reinforcement 53 . Therefore, many shear reinforcing bars 50 can be arranged on the end side of the beam 20, and since the degree of restraint of the concrete body is increased on the end side of the beam 20, the breaking strength of the concrete when crushed increases, Damage to the concrete body of the beam due to the compressive force generated at the upper and lower ends of the beam end can be reduced.

It should be noted that the present invention is not limited to the above-described embodiments, and includes modifications, improvements, etc. within the scope of achieving the object of the present invention.
For example, in the above-described embodiment, the upper constraining muscles 51 are arranged on the upper side of the beam and the lower constraining muscles 52 are arranged on the lower side of the beam, but the present invention is not limited to this. That is, as shown in FIG. 7, when the floor slab 21 is provided on the beam 20A, only the lower constraining muscles 52 may be arranged without arranging the upper constraining muscles. This is because the floor slab 21 bears the compressive force together with the beam 20 by providing the floor slab 21 on the beam 20A, so that the upper restraining muscle can be omitted.

In the above embodiment, the upper beam reinforcement 30B and the lower beam reinforcement 40B arranged on the outside of the second stage are used as through reinforcements, and the upper beam reinforcement 30C and the beam bottom reinforcement 40C arranged on the inside of the second stage are cut-off reinforcements. However, it is not limited to this. That is, all of the upper and lower beam muscles of the second stage may be cut-off muscles, or part of the upper and lower beam muscles of the second stage may be used as cut-off muscles.
In the above-described embodiment, the bundling muscles 53 are provided only in the vicinity of the tips of the second-stage beam top reinforcement 30C and the second-stage beam bottom reinforcement 40C, but the present invention is not limited to this. That is, all of the shear reinforcements surrounding the second-stage beam top reinforcement 30C and the second-stage beam bottom reinforcement 40C, which are arranged at the beam ends, may be used as bundling reinforcements. In this way, many shear reinforcing bars can be arranged on the beam end side to further increase the breaking strength when the concrete is crushed.
Further, in the above-described embodiment, the beam upper end reinforcement 30C or the beam lower end reinforcement 40C arranged at the beam end portion are all single reinforcements, but the present invention is not limited to this. That is, a part of the beam upper end reinforcement 30C and the beam lower end reinforcement 40C may be arranged as a single reinforcement, and the rest may be arranged by contacting a plurality of reinforcements.

1... Column-beam frame 10... Column 11... Column-beam joint 20, 20A... Beam 21... Floor slab 30A... First stage beam upper end reinforcement (upper first stage main reinforcement, through reinforcement)
30B: Upper end reinforcement of the second stage beam (upper second stage main reinforcement, through reinforcement)
30C: Upper end reinforcement of the second stage beam (upper second stage main reinforcement, cut-off reinforcement)
40A... First stage beam bottom reinforcement (lower first stage main reinforcement, through reinforcement)
40B...Second stage beam bottom reinforcement (lower second stage main reinforcement, through reinforcement)
40C...Second beam bottom reinforcement (lower second stage main reinforcement, cutoff muscle)
50... Stirrup (shear reinforcing bar) 51... Upper side constraining bar 52... Lower side constraining bar 53... Bundling bar 60... Fixing hardware

Claims (3)

A column-beam frame structure comprising reinforced concrete columns and reinforced concrete beams joined to the columns,
The beam includes first-stage main reinforcements arranged on the upper and lower end sides of the beam, second-stage main reinforcements arranged inside the first-stage main reinforcements, and the first-stage main reinforcements arranged at predetermined intervals along the length direction of the beam. a shear reinforcing bar provided surrounding the eye main bar and the second stage main bar,
All or part of the second stage main reinforcement is a cut-off reinforcement arranged only on the end side of the beam,
Fixing hardware is provided at the tip of the cut-off line,
Between the shear reinforcing bars from the end of the beam on the column side to the tip of the cut-off bar , an upper restraining bar surrounding the upper first-stage main bar and the second-tier main bar of the beam, and the beam A column-beam frame characterized by being provided with lower restraining reinforcements surrounding the first- stage main reinforcement and the second-stage main reinforcement on the lower side of the. A column-beam frame comprising reinforced concrete columns and reinforced concrete beams with floor slabs joined to the columns,
The beam includes first-stage main reinforcements arranged on the upper and lower end sides of the beam, second-stage main reinforcements arranged inside the first-stage main reinforcements, and the first-stage main reinforcements arranged at predetermined intervals along the length direction of the beam. a shear reinforcing bar provided surrounding the eye main bar and the second stage main bar,
All or part of the second stage main reinforcement is a cut-off reinforcement arranged only on the end side of the beam,
Fixing hardware is provided at the tip of the cut-off line,
Between the shear reinforcing bars from the column-side end of the beam to the tip of the cut-off bar , there is a lower restraining bar surrounding the first- stage main bar and the second-tier main bar on the lower side of the beam. A column-beam frame characterized by being provided. 3. The beam-to-column structure according to claim 1, wherein a plurality of said shear reinforcing bars or some of said shear reinforcing bars are arranged in contact with each other on the end side of said beam to form a bundling bar.

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