JP6204027B2 - Reinforced structure - Google Patents

Description

  The present invention relates to a shear reinforcement technique for reinforced concrete members.

  Various methods have been proposed for shear reinforcement of reinforced concrete members (hereinafter also referred to as RC members). For example, Patent Document 1 discloses a technique for shear reinforcement of a beam having an opening (through hole). Patent Document 2 discloses a structure in which shear reinforcement bars are crossed in a wall column (flat column). Further, Patent Document 3 discloses one using a core muscle.

  In general, RC members are reinforced by using D10 to D16 thin reinforcing bars to surround the main bars (hoops, stirrups). In addition, when using an ultra-high strength reinforcing bar (for example, SBPD1275 / 1420), the diameter of the shear reinforcing bar may be further reduced (nominal diameters 7.1 mm and 9.0 mm). As a shear reinforcement of RC members having a rectangular cross section, it is also known that a shear reinforcement bar is densely arranged near the end of a member having severe shear stress conditions.

  On the other hand, in such a rectangular cross-section member, in particular, a flat wall column or wall beam (wall girder) having a large long side / short side ratio, the width of the compressed concrete is narrow with respect to the bending resistance force by the main bars. For this reason, it will be in the final crack state as shown, for example in FIG. 7 (A), and it will be easy to produce crushing of member end compression part concrete compared with the member of a square cross section. Further, in the case of a beam member having an opening (through hole), when there is no opening reinforcement, as shown in FIG. 7 (B), a shearing crack extending from the opening is expanded, and sufficient opening reinforcement is applied. However, as shown in FIG. 7C, it can be a fracture type in which shear cracks expand above and below the opening.

JP 2011-256658 A Japanese Patent Laid-Open No. 2002-4411 JP-A-8-260565

  As a measure for suppressing the expansion of cracks in the vicinity of the main reinforcing bar position of the bending reinforcement portion of the member as shown in FIGS. 7 (A) to (C), for example, a large diameter reinforcing bar is used separately from the outer peripheral shear reinforcing bar. It is conceivable to provide the core muscle used. However, as shown in FIG. 8 (A), due to the reinforcement arrangement relating to the bending radius of the reinforcing bar and the extra length of the hook part, the bending radius and extra length of the reinforcing bar in the bent hook part are increased, making it difficult to arrange the reinforcing bar. There is a case. If the 180 ° hook is used instead of the 135 ° hook as shown in the figure, the extra length is shortened and the construction is complicated, but the number of cases where the bar arrangement is possible increases. However, as shown in the figure, although the tensile force works effectively in the straight portion (S2) of the core muscle, the other portion (S1) has poor tensile force. Therefore, the extension / expansion of a crack that induces destruction near the main muscle cannot be efficiently restrained.

  It is also possible to use large-diameter rebars for hoops and stirrups, and to densely arrange shear reinforcement bars (hoops and stirrups) using general thin-diameter rebars (D10 to D16). . However, each measure has difficulty and limitations in construction. In general, it is said that there is a limit to the effect of increasing the amount of shear reinforcement such as columns, beams and walls.

  One of the factors is shown in the commentary on earthquake-resistant walls in “(Old) Reinforced Concrete Structure Calculation Standards / Description” (hereinafter referred to as the former RC Standard) edited by the Architectural Institute of Japan. FIG. 8B is a schematic diagram shown in the same standard. In this explanation, since the shear reinforcement crosses at 45 ° with respect to the shear crack surface, the shear reinforcement attempts to bend by expanding the crack width (or displacement on the crack surface) as shown in the figure. If the concrete in the bent part is compressed and a reinforcing bar with a diameter larger than the cover thickness is used, or if the reinforcing bar is increased with a small diameter reinforcing bar, the concrete in the bent part will be locally destroyed and shear reinforcement will occur. It has been pointed out that the tensile force of the muscle does not increase so much and the reinforcing effect cannot be expected sufficiently.

  Therefore, it is considered that a reinforcing method that ensures a sufficient cover for large-diameter reinforcing bars is essential. This point is that, in the shear reinforcement of general RC members, except for the above-described core reinforcing bars, the shear reinforcing bars are applied to the outer periphery of the cross section and there is little fogging, and the effect of the shear reinforcing bars increases as the concrete strength increases. It is also related to previous research cases.

According to the present invention, the reinforcing structure of the reinforced concrete member having a rectangular cross section, wherein the reinforcing bars are respectively disposed at both corners of the reinforced concrete member so as to surround a plurality of main bars, A first shear reinforcement bar disposed on the outer peripheral side of the main bar and a linear line so as to cross the row of the main bars at the corners surrounded by the constraint bar on the inner peripheral side of the main bar An extended second shear reinforcement bar, wherein the second shear reinforcement bar has a larger diameter than the first shear reinforcement bar, and the outer peripheral side of the main bar at both ends thereof There is provided a reinforcing structure comprising a plate-type fixing unit located at the position .

  An object of the present invention is to perform shear reinforcement using a thicker reinforcing bar to a part where the stress condition is severe without securing the fog and degrading the workability.

  According to the present invention, there is provided a reinforcing structure for a reinforced concrete member, wherein the first shear reinforcing bar disposed on the outer peripheral side of the main reinforcing bar of the reinforced concrete member and the main reinforcing bar facing each other on the inner peripheral side of the main reinforcing bar. A second shear reinforcement bar extending linearly across the row, the second shear reinforcement bar being thicker than the first shear reinforcement bar, and There is provided a reinforcing structure characterized in that plate-type fixing portions are provided at both ends on the outer peripheral side of the main bar.

  According to the present invention, it is possible to perform shear reinforcement using a thicker reinforcing bar to a part where the stress condition is severe without securing the fog and deteriorating the workability.

(A) is a vertical sectional view of a flat column to which a reinforcing structure according to an embodiment of the present invention is applied, and (B) is a horizontal sectional view. (A) is a vertical cross-sectional view of a flat column to which another reinforcing structure is applied, (B) is a horizontal cross-sectional view, and (C) is a cross-sectional view taken along line II in FIG. 2 (A). (A) And (B) is a horizontal sectional view of the flat pillar to which the reinforcement structure of another example was applied, respectively. (A) is a horizontal sectional view of a beam to which a reinforcing structure according to an embodiment of the present invention is applied, (B) is a vertical sectional view, and (C) is a sectional view taken along line II-II in FIG. 4 (B). The vertical sectional view of the beam which applied the reinforcement structure of another example. The figure which shows a crack concentration rate and a cross-sectional defect rate. (A) is explanatory drawing of the crack state in a flat column, (B) and (C) are explanatory drawings of the crack state in the beam which has an opening part. (A) is explanatory drawing of the problem of a core line, (B) is explanatory drawing of the problem of the conventional shear reinforcement.

<First Embodiment>
FIG. 1A is a vertical sectional view of a flat column (wall column) 1, which is an RC member to which a reinforcing structure according to an embodiment of the present invention is applied, and shows an elevation view of the flat column 1. FIG. 1B is a horizontal sectional view of the flat column 1. In the drawings, arrows X and Y indicate horizontal directions orthogonal to each other, and an arrow Z indicates a vertical direction (vertical direction).

  The flat column 1 is an RC member having a rectangular cross section, the long side direction is the X direction, and the short side direction is the Y direction. The long side direction may be referred to as the left-right direction, and the short side direction may be referred to as the depth direction. The flat column 1 includes main bars 2a and 2b (referred to collectively as main bar 2), auxiliary bars 3, restraint bars 4, core bars 5, shear reinforcement bars 6 and shear reinforcement bars 7. The shear reinforcement bar 6 and the shear reinforcement bar 7 constitute a reinforcement structure according to an embodiment of the present invention.

  The main reinforcement 2 serving as a bending reinforcement is an aggregated main reinforcement having a relatively large diameter that works in the in-plane direction (X direction), and is roughly divided into a main reinforcement 2a at the left corner and a main reinforcement 2b at the right corner. Is done. As shown in FIG. 1B, the inner side of the envelope L surrounding all the main muscles 2 is called the inner peripheral side, and the outer side is called the outer peripheral side. The main bar 2 extends in the Z direction, and both the main bar 2a at the left corner and the main bar 2b at the right corner have a configuration of two in one row with the Y direction as the column direction. It is said to be eight. The main bar 2a at the left corner and the main bar 2b at the right corner constitute a row of main bars facing each other.

  The auxiliary bars 3 extend in the Z direction, and a plurality of bars (here, 20 bars) are arranged along the peripheral edge of the flat column 1. The restraint muscle 4 is divided into a main muscle 2a at the left corner and a main muscle 2b at the right corner, and is disposed so as to surround the auxiliary muscle 3 in the vicinity thereof. The core muscle 5 is arranged with both ends locked to the auxiliary muscle 3 at the center in the X direction of the flat column 1.

  The shear reinforcement bar 6 is arranged on the outer peripheral side of the main bar 2, and forms a hoop having a ring shape so as to surround the auxiliary bar 3 in the case of the present embodiment. As the shear reinforcement 6, for example, D10 to D16 small-diameter reinforcing bars can be adopted.

  The shear reinforcement bars 7 are linearly extended in the X direction so as to cross the rows of the main bars 2a and the main bars 2b facing each other on the inner peripheral side of the main bar 2. The shear reinforcement bars 7 are rod-like reinforcing bars having a diameter larger than that of the shear reinforcement bars 6 and are alternately arranged with the shear reinforcement bars 6 when viewed in the Z direction. In the case of the present embodiment, the shear reinforcement bars 7 are arranged in a single row at the center in the Y direction. However, it may be arranged in a plurality of rows (for example, up to about 4 rows depending on the member width).

  Plate-type fixing portions 7 a and 7 a are provided at both ends of the shear reinforcement 7. The plate-type fixing unit 7a may have any configuration as long as it projects in the radial direction of the shear reinforcing bar 7 and can improve the fixing property of the end of the shear reinforcing bar 7. For example, the diameter of the shear reinforcing bar 7 can be increased, the steel plate can be fixed, the nut having a fixing plate can be attached, and the like. In the case of using a steel plate, for example, it may be fixed to the end of the reinforcing bar constituting the shear reinforcing bar 7 by friction welding. The plate-type fixing unit 7 a is disposed on the outer peripheral side of the main bar 2.

  In the case of the present embodiment, the plate-type fixing unit 7 a is arranged to be hooked on the auxiliary muscle 3. This configuration improves the fixing property of the shear reinforcement 7 when a tensile force acts on the shear reinforcement 7. The object to be hooked may be the main muscle 2.

  In the flat column 1 having such a structure, when the shearing force acts in the direction of the arrow in the figure, the large-diameter shear reinforcing bar 7 cracks at the main bar position where the large-diameter shear reinforcing bar 7 induces collapse in the column base 1a serving as the compression unit (broken line) It is a reinforcement that directly restrains the expansion of L1), and can sufficiently prevent the expansion and extension of cracks.

By adopting the large-diameter shear reinforcement bar 7, the bending rigidity of the large-diameter reinforcing bar is larger than that when a large amount of small-diameter reinforcement reinforcement is used.・ Can prevent expansion. For example, in order to make the total cross-sectional area of the reinforcing bar equal with the thin reinforcing bar D10, nine (6.42 cm ² ) are required for one large reinforcing bar D29. Flexural rigidity of the reinforcement, i.e. the second moment ^{(I = πd 4/64,} d: Rebar diameter) Considering only, one D29 rebar becomes 7.9 times the D10 rebar nine equal cross-sectional area, both Even if the complicated stress condition of the concrete bearing surface of the reinforcing bar bend is taken into consideration, the bending rigidity of the reinforcing bar is surely increased by using the large diameter reinforcing bar.

  The effect of suppressing the extension / expansion of shear cracks is effective when the diameter of the shear reinforcing bar 7 is as large as possible, and is preferably at least twice as large as the diameter of the shear reinforcing bar 6 used together. It is preferably a D19 or higher reinforcing bar.

  The shear reinforcing bar 7 is a straight bar-shaped reinforcing bar and does not require bending, so that the workability is not deteriorated even if the diameter is large. Further, since the plate-type fixing portions 7a are provided at both ends thereof, not only the fixing property can be improved, but the fogging is influenced by the thickness of the plate-type fixing portion 7a, but is not affected by the diameter of the shear reinforcement bars 7. Even when a thicker reinforcing bar is used, it is easy to ensure the cover.

  Thus, in the reinforcing structure of the present embodiment, the shear reinforcement is performed using a thicker reinforcing bar to a part where the stress conditions are severe (here, the column base portion 1a) without securing the covering and degrading the workability. It can be carried out. In addition, since the bar arrangement method is simple and rational, the design method for ultimate strength and the like becomes clear and simple.

  In the present embodiment, the shear reinforcement bars 7 are arranged over the entire Z direction, but the plate-type fixing unit 7a is omitted in a portion where the stress condition is not relatively strict (for example, the intermediate portion in the Z direction of the flat column 1). Alternatively, the number of the shear reinforcement bars 7 may be reduced or eliminated.

Second Embodiment
FIG. 2A is a vertical sectional view of a flat column (wall column) 1 </ b> A, which is an RC member to which a reinforcing structure according to another embodiment of the present invention is applied, and shows an elevation view of the flat column 1. 2B is a horizontal sectional view of the flat column 1A, and FIG. 2C is a sectional view taken along line II-II in FIG. 2A. The flat column 1A is a modified example of the flat column 1 of the first embodiment. The same components are denoted by the same reference numerals, description thereof is omitted, and different points will be described below.

  This embodiment has a shear reinforcement bar 6 'corresponding to the shear reinforcement bar 6 of the first embodiment. The shear reinforcing bars 6 ′ are arranged on the outer peripheral side of the main reinforcing bars 2, but are straight bar-like reinforcing bars, and are provided in parallel with each other at a distance in the Y direction on the same horizontal plane.

  The shear reinforcement bars 7 are the same as those in the first embodiment, but the arrangement positions of the shear reinforcement bars 6 'and the shear reinforcement bars 7 are close to each other in the height direction (Z direction). In other words, the shear reinforcement bars 6 ′ and the shear reinforcement bars 7 are arranged so as to overlap each other in a direction (Y direction) parallel to the row direction of the main bars 2. In the present embodiment, in particular, the height of the central axis of the shear reinforcement bar 6 ′ and the central axis of the shear reinforcement bar 7 are located on the same horizontal plane (broken line L2), and the positions of both are aligned in the Z direction. It is said. A set of shear reinforcement bars 6 ′ and shear reinforcement bars 7 and restraint bars 4 are alternately arranged in the Z direction so as to avoid the interference between them.

  If the arrangement positions of the shear reinforcement bars 6 'and the shear reinforcement bars 7 are close to each other in the height direction (Z direction), the concrete area will be lost by the reinforcing bars in the cross section (broken line L2), and the acting shear force The bending crack generated by the above becomes easier to extend along the broken line L2.

  On the other hand, the larger the shear reinforcement bar 7 is, the higher the bending rigidity becomes, and the extension of shear cracks (broken line L3) across the shear reinforcement bar 7 can be suppressed. Actually, since the shearing force repeatedly acts positively and negatively during an earthquake, the bending crack (broken line L2) penetrates through the entire horizontal section in a relatively early stage, and the extension of the resulting shear crack (broken line L3) is generally common. It can be suppressed compared to a large reinforcing bar (a hoop of a small diameter reinforcing bar).

  Regarding the cross-sectional defect rate of concrete due to reinforcing bars, according to the study on the crack concentration ratio of crack-induced joints in the “Architectural Guidelines for Cracks in Reinforced Concrete Structures” edited by the Architectural Institute of Japan, the results shown in FIG. The defect rate is 20% for the cross section and the crack rate is 60% or more, and the defect rate is 22% and the concentration rate is 80%. This guideline aims at concentrating cracks due to drying shrinkage of concrete at the induced joints, but the external factor of cracking is the difference between drying shrinkage and acting shear force. Are also considered to be consistent.

  Therefore, in order to achieve the above effects, the total sum of the diameters of the outer peripheral shear reinforcing bar 6 'and the inner peripheral shear reinforcing bar 7 is preferably 20% or more with respect to the member width. For example, in this embodiment, with respect to a column width of 250 mm, the shear reinforcement bar 6 ': 2 pieces-D13 + shear reinforcement bar 7: 1 piece-D25, the defect rate can be 20.4%. Even if the positions where the shear reinforcement bars 6 'and the shear reinforcement bars 7 are not completely coincided with each other in the height direction (Z direction), the same effect can be expected.

  As a method for inducing bending cracking even if the shear reinforcement 6 'and the shear reinforcement 7 are separated in the Z direction, for example, the shear reinforcement 7 has a diameter of 10% or more with respect to the member width. For example, two diameter reinforcing bars may be used, or one large diameter reinforcing bar having a diameter of 20% or more of the member width may be used. As a result, the defect rate can be increased to 20% or more with only the shear reinforcement bars 7, the concentration of bending cracks can be effectively promoted, and the extension of the shear cracks can be suppressed by the bending rigidity of the shear reinforcement bars 7.

  Furthermore, even if the concrete cross-section defect rate due to the shear reinforcement 7 is 20% or less, if the diameter of the shear reinforcement 7 is at least twice that of the shear reinforcement 6 'used in combination and D19 or more, normal reinforcement (thinning reinforcement) Bending cracks are more likely to occur in advance at the position where the shear reinforcing bar 7 is disposed than in the case of only the muscle hoop. In any case, in this embodiment, in the state where multiple bending cracks penetrating the cross section are generated due to repeated positive and negative seismic loads, it is difficult to generate shear cracks crossing them. One of the features.

<Third Embodiment>
FIG. 3A is a horizontal sectional view of a flat column (wall column) 1B, which is an RC member to which a reinforcing structure according to another embodiment of the present invention is applied. The flat column 1B is a modification of the flat column 1 of the first embodiment. The same reference numerals are assigned to the same components, the description thereof is omitted, and different points will be described below.

  In this embodiment, in order to make the flat column 1B have high reinforcement and high proof strength, the main reinforcement 2 is increased from that in the first embodiment, and the shear reinforcement reinforcement 7 is also increased accordingly.

  In the first and second embodiments described above, the case where the main bar 2 is arranged so as not to contact the restraint bar 4 has been described for the purpose of increasing the cover thickness. However, the main bars in a more general flat column are often arranged so that the main bars 2 are in contact with the restraint bars 4 as in the example of FIG. In such a case, as shown in FIG. 7A, cracks along the main bars are likely to occur, but the shear reinforcing bars 7 are arranged in a plurality of rows with respect to the cross section (two rows in the example of FIG. 3A). By doing so, it is possible to provide a flat column with high toughness that prevents cracks along the bending reinforcement, and has high yield strength and excellent deformation performance.

  FIG. 3B is a horizontal cross-sectional view of a flat column (wall column) 1C, which is an RC member to which a reinforcing structure according to another embodiment of the present invention is applied. As with the flat column 1B described above, the main reinforcement 2 Are arranged in contact with the restraint muscle 4. The flat column 1C is an example in which mesh bars 8 are installed from both sides of the flat column 1C instead of the shear reinforcement bars 6 for the purpose of rationalizing the construction. The mesh reinforcement 8 corresponds to a mesh-like intersection of a reinforcing bar corresponding to the shear reinforcing bar 6 'in the second embodiment and a reinforcing bar corresponding to the reinforcing bar 3 described above. Such mesh streaks 8 can also be employed in the first embodiment and the second embodiment.

  In addition, since the cooperative effect of the restraining bar 4 and the shear reinforcing bar 7 can be expected in a part where the stress condition on both sides of the cross section is severe, if the amount of reinforcement of the shear reinforcing bar 7 is large, the intermediate part other than the restraining area on both sides of the cross section In the portion, a sufficient shear reinforcement effect can be expected with only the shear reinforcement 7 even without the mesh reinforcement 8.

<Fourth embodiment>
In this embodiment, the reinforcing structure of the present invention is applied to the reinforcement of the opening of the RC beam. 4A is a horizontal sectional view of the beam 11 to which the reinforcing structure according to the embodiment of the present invention is applied, FIG. 4B is a vertical sectional view, and FIG. 4C is along a line II-II in FIG. It is sectional drawing.

  In general opening reinforcement, in addition to shear reinforcement (small diameter stirrup) on the upper and lower chords above and below the opening, diagonal reinforcement bars (such as X-type) and ready-made opening reinforcement hardware around the opening Reinforced with. In the present embodiment, such reinforcement is not employed, and the upper chord material and the lower chord material at the top and bottom of the opening are reinforced, and the reinforcement at the time of opening where the shear stress is severe (opening left and right) is performed.

  The beam 11 is an RC member having a rectangular cross section, and its axial direction is the X direction, the beam direction is the Z direction, and the beam width direction is the Y direction. The axial direction may be referred to as the left-right direction, and the beam direction may be referred to as the up-down direction. The beam 11 has an opening 11a, which is a through hole that opens in the horizontal direction at the center in the axial direction. The beam 11 includes main bars 12a and 12b (referred to collectively as main bars 12), a shear reinforcing bar 16, a shear reinforcing bar 17, an opening reinforcing bar 18, and a restraining bar 19. The shear reinforcing bar 16, the shear reinforcing bar 17, and the opening reinforcing bar 18 constitute a reinforcing structure according to an embodiment of the present invention.

  The main muscle 12 is roughly classified into an upper main muscle 12a and a lower main muscle 12b. The main muscles 12 extend in the X direction, and each of the main muscles 12a and 12b has a configuration of four in one row with the Y direction as the row direction, and the total number is eight. The upper main bar 2a and the lower main bar 2b constitute a row of main bars facing each other.

  The shear reinforcement bars 16 are arranged on the outer peripheral side of the main bars 12, and in the case of the present embodiment, they constitute a stirrup arranged so as to surround the main bars 12. As the shear reinforcement 16, for example, D10 to D16 small-diameter reinforcing bars can be employed.

  The shear reinforcement bars 17 are linearly extended in the Z direction so as to cross the rows of the main bars 12a and the main bars 12b facing each other on the inner peripheral side of the main bars 12. The shear reinforcing bar 17 is a bar-shaped reinforcing bar having a diameter larger than that of the shear reinforcing bar 16. In the case of this embodiment, the shear reinforcement 17 is arrange | positioned at the up-down direction at the right-and-left side part of the opening part 11a, respectively, It is set to 2x2 = 4 on one side and a total of eight on both sides. However, the number of shear reinforcement bars 17 can be selected as appropriate.

  Plate-type fixing portions 17 a and 17 a are provided at both ends of the shear reinforcement 17. As in the first embodiment, the plate-type fixing unit 17a may have any configuration as long as the plate-type fixing unit 17a can protrude in the radial direction of the shear reinforcing bar 17 and improve the fixing property of the end of the shear reinforcing bar 7. The plate-type fixing unit 17 a is disposed on the outer peripheral side of the main bar 12. In the case of the present embodiment, the plate-type fixing unit 17a is arranged to be hooked on the main muscle 12. This configuration improves the fixing property of the shear reinforcement 17 when a tensile force acts on the shear reinforcement 17.

  In this embodiment, the main reinforcing bars 2 are arranged in a single step on the upper side and the lower side of the beam 11, respectively, so that the opening reinforcing bars 18 are provided at portions close to the upper and lower openings of the opening 11 a. In addition, in the case of a configuration in which the main reinforcing bars 2 are multistage reinforcing bars, the opening reinforcing bars 18 can be omitted.

  The opening reinforcing bars 18 are linear bar-like reinforcing bars that are respectively arranged at the upper and lower parts of the opening 11a and extend linearly in the left-right direction. Plate type fixing portions 18 a are provided at both ends of the opening reinforcing bars 18. The plate-type fixing unit 18a may be any configuration as long as the plate-type fixing unit 18a protrudes in the radial direction of the opening reinforcing bar 18 and can improve the fixing property of the end of the opening reinforcing bar 18 similarly to the plate-type fixing unit 7a of the first embodiment. It may be configured. The plate-type fixing unit 18a is not essential, but in the present embodiment, it is purposely provided for the purpose of efficiently and forcibly constraining cracks that induce destruction. The restraint bars 19 are arranged so as to surround the main bars 2 and the opening reinforcing bars 18.

  In the beam 11 having such a configuration, the large-diameter shear reinforcing bar 17 is a reinforcing bar that directly restrains the expansion of cracks (broken line L4) near the main reinforcing bar 12 and the opening reinforcing bar 18 that induce crushing. Can be sufficiently deterred. Further, the opening reinforcing bar 18 also restrains a crack that induces a fracture. The shear reinforcing bar 17 is also effective in suppressing adhesion splitting cracks along the main bar 12 that occurs when the main bar 12 has severe conditions.

  The shear reinforcing bar 17 is a straight bar-like reinforcing bar and does not require bending work, so that the workability is not deteriorated even if the diameter is large. Further, since the plate-type fixing portions 17a are provided at both ends thereof, not only the fixing property can be improved, but the fogging is influenced by the thickness of the plate-type fixing portion 17a, but is not affected by the diameter of the shear reinforcing bar 17. Even when a thicker reinforcing bar is used, it is easy to ensure the cover.

  In this way, in the reinforcing structure of the present embodiment as well, as in the reinforcing structure of the first embodiment, the cover is secured and a thicker part (here in the vicinity of the opening 11a) is stressed without deteriorating the workability. The shear reinforcement can be performed using a reinforcing bar having a diameter. In addition, since the bar arrangement method is simple and rational, the design method for ultimate strength and the like becomes clear and simple.

<Fifth Embodiment>
FIG. 5 is a vertical sectional view of a beam 11 ′ that is an RC member to which a reinforcing structure according to another embodiment of the present invention is applied. The beam 11 ′ is a modification of the beam 11 of the third embodiment. The same components are denoted by the same reference numerals, description thereof is omitted, and different points will be described below.

  In the case of the present embodiment, the main reinforcement 2 has a two-stage configuration in the upper and lower directions, the opening reinforcement 18 in the third embodiment is omitted, and the restraining reinforcement 19 'includes an upper main reinforcement 2a and a lower main reinforcement 2b. Are each enclosed.

  The beam 11 'has a plurality of openings 11a. In the example shown in the figure, the interval between the openings 11a is set to be twice the opening diameter, but is usually set to three or more times the opening diameter (edited by the Architectural Institute of Japan: Reinforced concrete bar arrangement guide).

  In such an RC beam having a plurality of openings 11a, the ultimate shear strength of the beam 11 'is determined by the lower one of the strength of the bundle material between the openings 11a shown in FIG. In FIG. 5, a broken line L5 indicates a breaking line for the upper chord material, a broken line L6 indicates a breaking line for the lower chord material, and a broken line L7 indicates a breaking line for the bundle material. When the amount of reinforcement on the fracture line is large, the shear compression fracture of concrete becomes the final fracture type, and when the amount of reinforcement decreases, the expansion of shear cracks on the fracture line becomes the final fracture type.

  The shear reinforcement 17 is arrange | positioned at the both right and left sides of each opening part 11a. The shear reinforcement 17 works effectively for preventing the breakage of the string material and the bundle material above and below the opening 11a. In addition, for reinforcement of the bundle material, an oblique reinforcing bar that obliquely passes through the side of the opening portion 11a is effective, but the interval between the opening portions 11a is set to a normal interval (more than three times the opening diameter). In this case, the fracture line L7 of the bundle is closer to the horizontal than the inclination (about 30 °) in the illustrated example. From the general theory that it is more effective to reinforce the reinforcing bars perpendicular to the cracks, the effect is not necessarily different from that of the oblique reinforcing bars, and the shear reinforcing bars 17 have high bending rigidity of the reinforcing bars on the fracture line. It is more rational than conventional methods (diagonal reinforcement, etc.) in terms of workability.

  As the position of the opening 11a is closer to the beam end, bending cracks are more likely to occur along the shear reinforcement bars 17 due to the bending stress of the member, and the effect of suppressing the extension / expansion of harmful shear cracks is further increased.

<Other embodiments>
In the first to fifth embodiments, RC columns and beams (opening reinforcement) are shown as targets. However, the application target of the present invention is not limited to these, and a seismic wall or wall type without a column shape is used. The present invention can be applied to various RC members such as shear reinforcement of bearing walls and opening reinforcement in the structure, and is particularly useful for shear reinforcement in the long side direction of RC members having a rectangular cross section. It can also be applied to prestressed concrete members.

Claims (1)

A reinforcing structure of a reinforced concrete member having a rectangular cross section,
At both corners of the reinforced concrete member, restraint bars are respectively arranged so as to surround a plurality of main bars,
A first shear reinforcing bar disposed on the outer peripheral side of the main reinforcing bar of the reinforced concrete member;
A second shear reinforcement bar linearly extending so as to cross the row of the main bars at both corners, surrounded by the constraint bars on the inner peripheral side of the main bar,
The second shear reinforcement is
Larger diameter than the first shear reinforcement, and
A reinforcing structure comprising plate-type fixing portions positioned on the outer peripheral side of the main bar at both ends thereof.

Images