RC wall frame

Abstract

To realize an RC wall frame capable of suppressing damage to an RC wall in an earthquake while reducing the cost by moving a position where a bending yield hinge of an RC beam is formed from the end part of the RC beam to the central part side when joining the RC beam to the RC wall.SOLUTION: An RC wall frame 1A includes an RC wall 2 and an RC beam 3 joined to the RC wall 2. The RC beam 3 includes a first beam main reinforcement 31 disposed on the central portion side in the length direction of the RC beam 3 so as to extend in the length direction and a second beam main reinforcement 32 disposed on an end part 3s side of the RC beam 3. The first beam main reinforcement 31 and the second beam main reinforcement 32 are connected by a reinforcement joint part 37. The RC wall 2 includes a wall horizontal reinforcement 23 disposed in the horizontal direction inside the RC wall 2. The second beam main reinforcement 32 is a large-diameter reinforcement or a high-strength reinforcement as compared with the first beam main reinforcement 31, is disposed to extend inside the RC wall 2, and is joined to the wall horizontal reinforcement 23 via a lap joint part 5 or an open lap joint part.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an RC wall frame comprising an RC wall and an RC beam joined to the RC wall. [Background technology]

[0002] In the structural design of reinforced concrete beam-column frames, it is common to design RC (reinforced concrete) beams so that their flexural yield hinges are formed at the joints between the RC beams and RC columns, more specifically, at the interface between the ends of the RC beams and the RC columns. However, in this case, when an earthquake occurs, the calculated flexural strength of the RC beams at the time of design is not exerted, and both the main reinforcement of the RC beams and the main reinforcement of the RC columns embedded in the column-beam joints may yield within the column-beam joints, causing the column-beam joints to fail first. In order to prevent such premature failure of beam-column joints, in RC beams, the strength of the main beam reinforcement located on the beam-column joint side, i.e., the end side of the beam in the longitudinal direction of the beam, is made higher than the strength of the main beam reinforcement located on the central side of the beam, thereby moving the position where the flexural yield hinge is formed from the interface between the end of the RC beam and the RC column toward the central side, a process known as hinge relocation.

[0003] For example, Patent Document 1 discloses a configuration in which the main reinforcement for a beam connected to a column has a normal-strength portion and a high-strength portion having a strength greater than that of the normal-strength portion. In this configuration, the high-strength portion is arranged in a region extending from the column-beam joint along the length of the beam, and the normal-strength portion is arranged on the opposite side of the column-beam joint from the high-strength portion. The high-strength portion in the region extending from the column-beam joint along the length of the beam is formed by partially hardening normal reinforcing bars with the same strength as the normal-strength portion. Furthermore, Patent Document 2 discloses a configuration in which, in a reinforced concrete column-beam joint, the beam main reinforcement is made of high-strength reinforcing bars from the intersection with the column to the beam end, and is connected to ordinary reinforcing bars in the middle of the beam with a mechanical joint, thereby shifting the yield region of the beam main reinforcement to the middle of the beam. Furthermore, Patent Document 3 discloses a configuration in which additional reinforcing bars are separately arranged on both the left and right sides of the center of a beam in a reinforced concrete structure.

[0004] The above-described hinge relocation of RC beams in reinforced concrete beam-column frames is also effective when the RC beam is connected to a RC wall. For example, when an RC beam is erected between two RC walls spaced apart on the same plane, hinge relocation of the RC beam connected to the RC wall can be achieved by connecting the central main reinforcement of the RC beam to the larger-diameter, higher-strength end main reinforcement using mechanical joints, and then embedding the end main reinforcement within the RC wall, extending from the end of the RC beam into the RC wall. When connecting an RC beam to a RC wall using this structure, it is necessary to sufficiently embed the end main reinforcement into the RC wall, or to attach plate nuts or anchors to the end main reinforcement to ensure that the end main reinforcement is adequately anchored to the RC wall. This increases the cost of connecting an RC beam to a RC wall. When joining an RC beam to an RC wall, it is desirable to move the position where the flexural yield hinge of the RC beam is formed from the end of the RC beam toward the center, thereby realizing an RC wall frame that can suppress damage to the RC wall during an earthquake while reducing costs. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-69926 [Patent Document 2] Japanese Patent Application Publication No. 1-244040 [Patent Document 3] Japanese Patent Application Publication No. 2018-145595 Summary of the Invention [Problem to be solved by the invention]

[0006] The problem that this invention aims to solve is to realize an RC wall frame with excellent seismic resistance, in which an RC wall and an RC beam are joined, by moving the position of the flexural yield hinge of the RC beam from the end of the RC beam to the center, thereby suppressing damage to the end of the RC beam and the RC wall joined to the RC beam in the event of an earthquake, while reducing costs. [Means for solving the problem]

[0007] In order to solve the above problems, the present invention employs the following means. That is, the RC wall frame of the present invention is an RC wall frame comprising an RC wall and an RC beam joined to the RC wall, and the main beam reinforcement provided on the end side of the RC beam is arranged extending inside the RC wall and joined to the wall cross reinforcement arranged horizontally inside the RC wall via a lap joint or an open lap joint, and some of the main beam reinforcement on the end side are connected to the main beam reinforcement on the central side of the RC beam, and the remaining main beam reinforcement is a cut-off reinforcement arranged only on the end side of the beam. According to the above-mentioned configuration, the main beam reinforcement at the end of the RC beam is arranged to extend inside the RC wall and is joined to the horizontal wall reinforcement arranged inside the RC wall via a lap joint or a gap lap joint. Therefore, the stress acting on the main beam reinforcement of the RC beam is transmitted to the RC wall by the main beam reinforcement at the end and the horizontal wall reinforcement being joined by a lap joint or a gap lap joint inside the RC wall. Here, some of the beam reinforcement bars at the end are connected to the beam reinforcement bars at the center of the RC beam, while the remaining beam reinforcement bars are cutoff reinforcement arranged only at the end of the beam. This configuration results in a greater number of beam reinforcement bars transmitting stress to the RC wall at the end than at the center. Therefore, during an earthquake, flexural yield hinges that develop in the RC beam are formed near the center of the RC beam. By shifting the position of the flexural yield hinges that develop in the RC beam from the end to the center of the RC beam in this way, cracks propagating from the flexural yield hinges during an earthquake can be prevented, suppressing damage to the end of the RC beam or the RC wall connected to the RC beam, thereby improving seismic performance. In particular, as described above, the main beam reinforcement at the end is connected to the cross-bars of the RC wall via lap joints or gap lap joints. This improves the anchoring performance of the main beam reinforcement at the end to the RC wall, thereby reducing the length of the main beam reinforcement at the end embedded in the RC wall. Furthermore, it also reduces the need to provide anchoring devices such as plate nuts or anchors for the main beam reinforcement at the end. This reduces the cost required to construct the RC wall frame. In this way, in an RC wall frame where an RC wall and an RC beam are joined, by moving the position of the flexural yield hinge of the RC beam from the end of the RC beam toward the center, it is possible to realize an RC wall frame that can suppress damage to the end of the RC beam and the RC wall joined to the RC beam in the event of an earthquake, while reducing costs.

[0008] In one aspect of the present invention, the main beam bars on the end side are larger diameter reinforcing bars or higher strength reinforcing bars than the main beam bars on the central side. With this configuration, the position where the flexural yield hinge of the RC beam is formed can be more efficiently moved from the end of the RC beam to the center, thereby suppressing damage to the RC wall in the event of an earthquake. [Effects of the Invention]

[0009] According to the present invention, in an RC wall frame where an RC wall and an RC beam are joined, by moving the position of the flexural yield hinge of the RC beam from the end of the RC beam to the center, it is possible to realize an RC wall frame that can suppress damage to the end of the RC beam and the RC wall joined to the RC beam in the event of an earthquake, while reducing costs. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view showing the configuration of an RC wall frame according to an embodiment of the present invention. [Figure 2] FIG. 2 is a vertical cross-sectional view showing the joint structure between the RC wall and the end of the RC beam in the RC wall frame of the embodiment. [Figure 3] FIG. 3 is a diagram showing the construction procedure of the RC wall frame shown in FIG. 2. [Figure 4] FIG. 10 is a vertical cross-sectional view showing a joint structure between an RC wall and an end portion of an RC beam in an RC wall frame according to a first modified example of the above embodiment. [Figure 5] FIG. 5 is a diagram showing the construction procedure of the RC wall frame shown in FIG. 4. [Figure 6] FIG. 10 is a vertical cross-sectional view showing a joint structure between an RC wall and an end portion of an RC beam in an RC wall frame according to a second modified example of the above embodiment. [Figure 7] FIG. 7 is a cross-sectional view of part II in FIG. 6. [Figure 8] FIG. 7 is a cross-sectional view taken along line II-II in FIG. 6. DETAILED DESCRIPTION OF THE INVENTION

[0011] In the present invention, in an RC wall frame in which an RC wall and an RC beam are joined, the second main beam reinforcement on the beam end side of the RC beam is extended to the inside of the RC wall, and the second main beam reinforcement and the horizontal wall reinforcement of the RC wall are joined with a lap joint or a gap lap joint. Hereinafter, an embodiment of an RC wall frame according to the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a cross-sectional view illustrating the configuration of an RC wall frame according to an embodiment of the present invention. As shown in Fig. 1, the RC wall frame 1A comprises an RC wall 2 and an RC beam 3 joined to the RC wall 2. The RC wall frame 1A constitutes, for example, a multi-story earthquake-resistant wall installed in an architectural structure. Note that, as long as the RC wall frame 1A comprises the RC wall 2 and the RC beam 3 joined to the RC wall 2, there are no limitations on its use or the location in the architectural structure to which it is applied. The RC walls 2 are formed along a plane that intersects horizontally (a plane along the plane of the paper in FIG. 1). A plurality of the RC walls 2 are arranged at intervals in the horizontal direction (left-right direction in FIG. 1) along the surface, i.e., in the width direction. In this embodiment, for example, three RC walls 2 are provided on the same plane, spaced apart in the horizontal direction. The number of RC walls 2 is not limited to three, and may be two, four or more.

[0012] FIG. 2 is a vertical cross-sectional view showing the joint structure between the RC wall and the end of the RC beam in the RC wall frame of this embodiment. As shown in FIG. 2, each RC wall 2 includes a concrete portion 21 formed in a predetermined shape, and vertical wall reinforcement bars 22 and horizontal wall reinforcement bars 23 embedded in the concrete portion 21. A plurality of vertical wall reinforcements 22 are provided at intervals in the width direction of the RC wall 2 (left-right direction on the paper in FIG. 1). Alternatively, a plurality of vertical wall reinforcements 22 may be provided at intervals in the thickness direction of the RC wall 2 (direction perpendicular to the paper in FIG. 1) intersecting the surface of the RC wall 2. Each vertical wall reinforcement 22 extends in the up-down direction. A plurality of horizontal wall reinforcements 23 are provided at intervals in the vertical direction along the surface of the RC wall 2. A plurality of vertical wall reinforcements 22 may also be provided at intervals in the thickness direction of the RC wall 2. Each horizontal wall reinforcement 23 is arranged horizontally inside the RC wall 2. Each horizontal wall reinforcement 23 extends in the width direction of the RC wall 2 (the length direction of the RC beam 3, which will be described later). In this way, when the RC wall 2 is viewed from its thickness direction, a plurality of vertical wall reinforcements 22 and a plurality of horizontal wall reinforcements 23 are arranged, for example, in a lattice pattern. In this embodiment, the RC wall 2 is made of precast concrete. That is, in the RC wall 2, vertical wall reinforcement 22 and horizontal wall reinforcement 23 are embedded in a concrete portion 21 that has been formed in advance into a predetermined shape.

[0013] The RC beam 3 has its end portions 3s in the longitudinal direction joined to the RC wall 2. In this embodiment, the RC beam 3 is erected between adjacent RC walls 2. The RC beam 3 has its end portions 3s on both sides in the longitudinal direction joined to the RC wall 2. The RC beam 3 includes first beam main reinforcement bars 31, second beam main reinforcement bars 32, shear reinforcement bars 34, and a beam concrete portion 35. The first beam main reinforcement 31 and the second beam main reinforcement 32 are provided on the upper end 3t side and the lower end 3b side of the RC beam 3. The first beam main reinforcement 31 and the second beam main reinforcement 32 are provided on both ends of the RC beam 3 in the beam width direction (depth direction of the paper in FIG. 2 ) on the upper end 3t side and the lower end 3b side. The first beam main reinforcement 31 is arranged on the longitudinal center 3c (see FIG. 1) side of the RC beam 3. The first beam main reinforcement 31 extends in the longitudinal direction of the RC beam 3. The first beam main reinforcement 31 is provided so as to extend from the central portion 3c of the RC beam 3 to the end portions 3s on both sides in the longitudinal direction.

[0014] The second beam main reinforcements 32 are arranged on the end portion 3s side on both longitudinal sides of the RC beam 3. The second beam main reinforcements 32 are larger diameter reinforcing bars or higher strength reinforcing bars than the first beam main reinforcements 31. The second beam main reinforcements 32 protrude from the end portion 3s of the RC beam 3 toward the inside of the concrete portion 21 of the RC wall 2 and are arranged extending inside the RC wall 2. In other words, a portion of the second beam main reinforcements 32 in the longitudinal direction is embedded in the beam concrete portion 35 of the RC beam 3, and the remaining portion of the second beam main reinforcements 32 in the longitudinal direction is embedded in the concrete portion 21 of the RC wall 2. When the RC wall 2 is manufactured as precast concrete, a portion of the second main beam reinforcement 32 of the RC beam 3 on the RC wall 2 side is embedded in the concrete portion 21, and the remaining portion on the RC beam 3 side protrudes outward from the concrete portion 21.

[0015] The end 31s of the first beam main reinforcement 31 and one end 32s of the second beam main reinforcement 32 located inside the beam concrete portion 35 are joined by a reinforcing bar joint 37. The reinforcing bar joint 37 is, for example, a cylindrical mortar-filled joint having dimensions that match the diameter of the second beam main reinforcement 32. The reinforcing bar joint 37 joins the first beam main reinforcement 31 and the second beam main reinforcement 32 by inserting the end 31s of the first beam main reinforcement 31 from one side and the end 32s of the second beam main reinforcement 32 from the other side, and filling the interior with mortar (not shown). The other end 32t of the second beam main reinforcement 32, opposite to one end 32s located within the beam concrete portion 35, is joined to the wall cross reinforcement 23 within the RC wall 2 via a lap joint 5 or a gap lap joint. In this embodiment, the other end 32t of the second beam main reinforcement 32 and the wall cross reinforcement 23 are arranged side by side at the lap joint 5 so that they overlap in part of their length direction, and are bound together with a wire or the like. When joined via a gap lap joint, the second beam main reinforcement 32 and the wall cross reinforcement 23 do not necessarily need to be bound with a wire or the like. In this case, the second beam main reinforcement 32 and the wall cross reinforcement 23 only need to be positioned so that the distance between the second beam main reinforcement 32 and the wall cross reinforcement 23 in the vertical direction is 0.2 × L or less and 150 mm or less, based on the length (L) of the lap joint between the second beam main reinforcement 32 and the wall cross reinforcement 23. When the other end 32t of the second beam main reinforcement 32 is joined to the wall cross reinforcement 23 via an open lap joint, the other end 32t of the second beam main reinforcement 32 and the wall cross reinforcement 23 are arranged so that they overlap in part of their lengthwise direction and are spaced a predetermined distance apart in a direction intersecting the lengthwise direction.

[0016] A plurality of shear reinforcement bars 34 are provided at intervals along the length of the RC beam 3. On the central portion 3c side of the RC beam 3, each shear reinforcement bar 34 is provided so as to surround the first beam main reinforcement bars 31 provided on the upper end portion 3t side and the lower end portion 3b side. On the end portion 3s side of the RC beam 3, each shear reinforcement bar 34 is provided so as to surround the second beam main reinforcement bars 32 provided on the upper end portion 3t side and the lower end portion 3b side. The beam concrete portion 35 is provided so as to cover and embed the first beam main reinforcement bars 31, the second beam main reinforcement bars 32, and the shear reinforcement bars 34 over the entire length of the RC beam 3. In this embodiment, the beam concrete portion 35 has a precast concrete portion 35p formed on the central portion 3c side of the longitudinal direction of the RC beam 3, and a cast-in-place concrete portion 35c formed on both ends 3s of the longitudinal direction of the RC beam 3. That is, in this embodiment, the RC beam 3 has a precast concrete beam 3P in a part of the center in the longitudinal direction of the RC beam 3. The precast concrete beam 3P has a precast concrete section 35p. The center in the longitudinal direction of the first beam main reinforcement 31 is embedded in the precast concrete section 35p, and the longitudinal ends 31s protrude on both sides in the longitudinal direction from the precast concrete section 35p. The cast-in-place concrete section 35c is provided between the concrete section 21 of the RC wall 2 and the precast concrete section 35p. An end 31s of the first beam main reinforcement 31, one end 32s of the second beam main reinforcement 32, and a reinforcing bar joint 37 joining them are embedded in the cast-in-place concrete section 35c.

[0017] FIG. 3 is a diagram showing the construction procedure for the RC wall frame shown in FIG. To construct such an RC wall frame 1A, a precast concrete RC wall 2 is fabricated in advance, in which the ends 32t of the wall vertical reinforcement 22, wall horizontal reinforcement 23, and second beam main reinforcement 32 on the RC wall 2 side are embedded in the concrete section 21, and a precast concrete beam 3P is fabricated in advance, in which the first beam main reinforcement 31 is embedded in the precast concrete section 35p. Here, the ends 32s of the second beam main reinforcement 32 protrude from the concrete section 21 of the RC wall 2. Furthermore, both ends 31s of the first beam main reinforcement 31 protrude from the precast concrete beam 3P. Next, as shown in Fig. 3, such an RC wall 2 and a precast concrete beam 3P are placed with a predetermined distance between them. Subsequently, an end 31s of the first beam main reinforcement 31 and one end 32s of the second beam main reinforcement 32 are joined with a reinforcing bar joint 37 between the RC wall 2 and the precast concrete beam 3P. 2, a formwork (not shown) is then assembled around the end 31s of the first beam main reinforcement 31, one end 32s of the second beam main reinforcement 32, and the reinforcing bar joint 37 connecting them, and concrete is poured into the formwork. As the poured concrete hardens, a cast-in-place concrete section 35c is formed between the RC wall 2 and the precast concrete beam 3P. In this way, the RC beam 3 is constructed, and the RC wall frame 1A is built.

[0018] In such an RC wall frame 1A, the moment distribution diagram in the RC beam 3 during an earthquake is as shown in FIG. The ultimate bending strength calculated for the first beam main reinforcement 31 is defined as M1, and the ultimate bending strength calculated for the second beam main reinforcement 32 is defined as M2. Furthermore, the position of the side surface of the RC wall 2 is defined as p, and the position of the end face of the reinforcing bar joint 37 on the beam center side is defined as q. When an earthquake occurs and a large bending moment acts on the RC beam 3, even if the bending moment at position p attempts to reach the ultimate bending strength M2 calculated for the second beam main reinforcement 32, the bending moment at position q will have already reached the ultimate bending strength M1 calculated for the first beam main reinforcement 31 at an earlier stage. For this reason, the bending moment at position p is suppressed to a value M21 that is smaller than the ultimate bending strength M2. Therefore, the RC beam 3 does not yield at position p, but rather at position q, and this position q becomes the position where a bending yield hinge occurs.

[0019] According to the RC wall frame 1A described above, the RC wall frame 1A comprises an RC wall 2 and an RC beam 3 joined to the RC wall 2, the RC beam 3 comprises a first beam main reinforcement 31 arranged at the center 3c side in the longitudinal direction of the RC beam 3 and a second beam main reinforcement 32 arranged at the end 3s side of the RC beam 3 so as to extend in the longitudinal direction of the RC beam 3, the first beam main reinforcement 31 and the second beam main reinforcement 32 being connected by a reinforcing bar joint section 37, the RC wall 2 comprises wall cross reinforcement 23 arranged horizontally inside the RC wall 2, the second beam main reinforcement 32 being a larger diameter reinforcing bar or a high strength reinforcing bar compared to the first beam main reinforcement 31, arranged extending inside the RC wall 2 and joined to the wall cross reinforcement 23 via a lap joint section 5 or an open lap joint section. According to the above-described configuration, the first beam main reinforcement 31 provided on the central portion 3c side in the longitudinal direction of the RC beam 3 is connected to the second beam main reinforcement 32 arranged on the end portion 3s side by the reinforcing bar joint 37. The second beam main reinforcement 32 is arranged extending inside the RC wall 2 and joined to the horizontal wall reinforcement 23 of the RC wall 2 via a lap joint 5 or a gap lap joint. Therefore, the stress acting on the first beam main reinforcement 31 and the second beam main reinforcement 32 constituting the RC wall 2 is transmitted to the RC wall 2 by the second beam main reinforcement 32 and the horizontal wall reinforcement 23 being joined inside the RC wall 2 by the lap joint 5 or the gap lap joint. Here, the second beam main reinforcement 32 is a larger diameter reinforcing bar or a higher strength reinforcing bar than the first beam main reinforcement 31. Therefore, in the event of an earthquake, the flexural yield hinge that occurs in the RC beam 3 is formed not at the end 3s of the RC beam 3 where the second beam main reinforcement 32 is provided, where the RC beam 3 and the RC wall 2 are joined, but closer to the central portion 3c of the RC beam 3 where the first beam main reinforcement 31, which has a smaller diameter or lower strength than the second beam main reinforcement 32, is provided. In this way, by shifting the position of the flexural yield hinge that occurs in the RC beam 3 from the end 3s of the RC beam 3 to the central portion 3c, in the event of an earthquake, the occurrence of cracks that propagate from the flexural yield hinge can be prevented, and damage to the ends of the RC beam 3 or the RC wall 2 joined to the RC beam 3 can be suppressed, thereby improving seismic performance. In particular, as described above, the second beam main reinforcement 32 is joined to the wall cross reinforcement 23 of the RC wall 2 via lap joints 5 or open lap joints. This improves the anchoring performance of the second beam main reinforcement 32 to the RC wall 2, thereby reducing the length of the second beam main reinforcement 32 embedded inside the RC wall 2. Furthermore, it also reduces the need to provide anchoring devices such as plate nuts and anchors for the second beam main reinforcement 32. This reduces the cost required to construct the RC wall frame 1A. In this way, in the RC wall frame 1A in which the RC wall 2 and the RC beam 3 are joined, by moving the position of the flexural yield hinge of the RC beam 3 from the end 3s of the RC beam 3 toward the center 3c, it is possible to realize the RC wall frame 1A that can suppress damage to the end of the RC beam 3 and the RC wall 2 joined to the RC beam 3 in the event of an earthquake, while reducing costs.

[0020] (First Modification of the Embodiment) The RC wall frame of the present invention is not limited to the above-described embodiment explained with reference to the drawings, and various modifications are possible within the technical scope. For example, in the above embodiment, a part of the central portion in the longitudinal direction of the RC beam 3 is made of a precast concrete beam 3P, and cast-in-place concrete portions 35c are arranged on both sides in the longitudinal direction, but this is not limited to this. FIG. 4 is a vertical cross-sectional view showing the joint structure between the RC wall and the end of the RC beam in the RC wall frame of this modified example. In the RC wall frame 1B shown in Fig. 4, the entire longitudinal length of the RC beam 3 may be a precast concrete beam 3Q. That is, in the precast concrete beam 3Q, the first beam main reinforcement 31, a portion of the second beam main reinforcement 32, and a reinforcing bar joint 37 joining an end 31s of the first beam main reinforcement 31 to one end 32s of the second beam main reinforcement 32 are embedded in a precast concrete section 35q formed in advance into a predetermined shape. The other end 32t of the second beam main reinforcement 32 protrudes from the precast concrete section 35q to both ends of the RC beam 3 in the longitudinal direction.

[0021] FIG. 5 is a diagram showing the construction procedure of the RC wall frame shown in FIG. To construct the RC wall frame 1B, after arranging the wall vertical reinforcement 22 and wall horizontal reinforcement 23 that form the RC wall 2, the precast concrete beam 3Q is hung in place, and the other end 32t of the second beam main reinforcement 32 protruding from the precast concrete section 35q is joined to the wall horizontal reinforcement 23 with a lap joint 5. Thereafter, the concrete that forms the concrete section 21 is poured in place, thereby constructing the RC wall 2.

[0022] In this modified example, as in the above embodiment, when joining an RC beam 3 to an RC wall 2, the position where the flexural yield hinge of the RC beam 3 is formed can be moved from the end 3s of the RC beam 3 to the center, thereby realizing an RC wall structure 1B that can suppress damage to the RC wall 2 during an earthquake while reducing costs.

[0023] (Second Modification of the Embodiment) Fig. 6 is a vertical cross-sectional view showing a joint structure between an RC wall and an end of an RC beam in an RC wall frame according to a second modified example of the embodiment. Fig. 7 is a cross-sectional view of part II in Fig. 6. Fig. 8 is a cross-sectional view of part II-II in Fig. 6. As shown in FIG. 6, the RC wall frame 1C in this modification includes third beam main reinforcement bars 33 and restraining reinforcement bars 39 in addition to the configuration shown in the above embodiment. As in the above embodiment, the RC wall frame 1C includes first beam main reinforcements 31 (beam main reinforcements at the center of the RC beam) and second beam main reinforcements 32 (some of the beam main reinforcements at the end of the RC beam) at the upper end 3t and lower end 3b of the RC beam 3C. Additionally, multiple shear reinforcements 34 are provided at intervals along the length of the RC beam 3C. As shown in FIG. 7, in the portions where the first beam main reinforcements 31 are provided, each shear reinforcement 34 is provided so as to surround the first beam main reinforcements 31 provided at the upper end 3t and lower end 3b, forming a closed structure. As shown in FIG. 8, at both ends 3s of the RC beam 3C, each shear reinforcement 34 is arranged to surround the second beam main reinforcement 32a provided on the upper end 3t side and the lower end 3b side, the second beam main reinforcement 32b provided on the lower end 3b side, and the third beam main reinforcement 33 of each stage, which will be described next, to form a closed type.

[0024] The third beam main reinforcement 33 (other beam main reinforcement among the beam main reinforcement on the end side of the RC beam) is provided inside the shear reinforcement 34 at both ends 3s of the RC beam 3C. The third beam main reinforcement 33 is arranged between the second beam main reinforcement 32a on the upper end 3t side and the second beam main reinforcement 32b on the lower end 3b side. The third beam main reinforcement 33 is provided in multiple stages in the vertical direction. In this embodiment, the third beam main reinforcement 33 is provided in two stages in the vertical direction. The uppermost third beam main reinforcement 33a is arranged at a distance below the second beam main reinforcement 32a on the upper end 3t side of the RC beam 3C, at a distance from the bottom of the second beam main reinforcement 32b on the lower end 3b side. The lowermost third beam main reinforcement 33b is arranged at a distance above the bottom of the second beam main reinforcement 32b on the lower end 3b side of the RC beam 3C. Each third beam main reinforcement 33 is provided extending in the length direction of the RC beam 3C. The third beam main reinforcement 33 is a cut-off reinforcement arranged only on the end 3s side of the RC beam 3C, and has the same length in the extension direction as the second beam main reinforcement 32. The third beam main reinforcement 33 is provided in a position overlapping the second beam main reinforcement 32 when viewed from the top-bottom direction. The third beam main reinforcement 33 protrudes from the end 3s of the RC beam 3C toward the inside of the concrete portion 21 of the RC wall 2 and is arranged extending inside the RC wall 2. In other words, a part of the length of the third beam main reinforcement 33 is embedded in the beam concrete portion 35 of the RC beam 3C, and the remaining part of the length of the third beam main reinforcement 33 is embedded in the concrete portion 21 of the RC wall 2.

[0025] An end 33t of the third beam main reinforcement 33 on the side embedded in the concrete portion 21 of the RC wall 2 is joined via a lap joint 5 or a gap lap joint to a cross wall reinforcement 23 located corresponding to the third beam main reinforcement 33 within the RC wall 2. In this modification, at the lap joint 5, the end 33t of the third beam main reinforcement 33 on the RC wall 2 side and the cross wall reinforcement 23 are arranged side by side so that they overlap in part of their lengthwise direction, and are bound together by wire or the like. In this modification, both the end 32t of the second beam main reinforcement 32 and the end 33t of the third beam main reinforcement 33 are joined to the corresponding wall cross reinforcement 23 by lap joints 5 in the RC wall 2, but only one of the end 32t of the second beam main reinforcement 32 and the end 33t of the third beam main reinforcement 33 may be joined to the wall cross reinforcement 23 by a lap joint 5, and the other may be joined to the wall cross reinforcement 23 by a gap lap joint. Alternatively, both the end 32t of the second beam main reinforcement 32 and the end 33t of the third beam main reinforcement 33 may be joined to the wall cross reinforcement 23 by a gap lap joint.

[0026] The constraining reinforcement 39 is a closed-type reinforcing bar provided at the end 3s of the RC beam 3C, on both the upper end 3t side and the lower end 3b side, so as to surround the second beam main reinforcement 32 and the third beam main reinforcement 33. A plurality of constraining reinforcement 39 is provided at the end 3s of the RC beam 3C, at intervals in the longitudinal direction, within the range where the second beam main reinforcement 32 and the third beam main reinforcement 33 are provided. The positions of the constraining reinforcement 39 in the longitudinal direction of the RC beam 3C may be the same as the positions of the shear reinforcement 34, or may be offset from the shear reinforcement 34 in the longitudinal direction. Furthermore, the spacing between the constraining reinforcement 39 in the longitudinal direction of the RC beam 3C may be the same as or different from the spacing between the shear reinforcement 34. The restraining bars 39 include upper restraining bars 39a and lower restraining bars 39b. The upper restraining bars 39a are provided surrounding the second beam main reinforcement 32a on the upper end 3t side and the uppermost third beam main reinforcement 33a. The lower restraining bars 39b are provided surrounding the second beam main reinforcement 32b on the lower end 3b side and the lowermost third beam main reinforcement 33b. In this way, the second beam main reinforcement 32 and the third beam main reinforcement 33 are doubly surrounded by the shear reinforcement 34, the upper restraint reinforcement 39a, and the lower restraint reinforcement 39b.

[0027] According to the RC wall structure 1C described above, as in the above embodiment, when joining the RC beam 3C to the RC wall 2, the position where the flexural yield hinge of the RC beam 3C is formed can be moved from the end 3s of the RC beam 3C to the central portion 3c, thereby realizing the RC wall structure 1C that can suppress damage to the RC wall 2 during an earthquake while reducing costs.

[0028] In addition, the first beam main reinforcement 31 and the second beam main reinforcement 32 are provided on the upper end 3t side and the lower end 3b side of the RC beam 3C, respectively, and at the end of the RC beam 3C, the third beam main reinforcement 33 is arranged between the second beam main reinforcement 32a on the upper end 3t side and the second beam main reinforcement 32b on the lower end 3b side, and the third beam main reinforcement 33 is arranged extending inside the RC wall 2 and is joined to the wall cross reinforcement 23 via a lap joint portion 5 or a gap lap joint portion. According to this configuration, at the end of the RC beam 3C, the third beam main reinforcement 33 is provided between the second beam main reinforcement 32a on the upper end 3t side and the second beam main reinforcement 32b on the lower end 3b side. As a result, the number of beam main reinforcement bars (second beam main reinforcement bars 32 and third beam main reinforcement bars 33) on the end 3s side of the RC beam 3C is greater than the number of beam main reinforcement bars (first beam main reinforcement bars 31) on the central portion 3c side of the RC beam 3C. Therefore, the position where the flexural yield hinge of the RC beam 3C is formed can be more efficiently shifted from the end 3s of the RC beam 3C toward the central portion 3c side, thereby suppressing damage to the RC wall 2 in the event of an earthquake. Furthermore, within the RC wall 2, the third beam main reinforcement 33 and the wall cross reinforcement 23 are joined via lap joints 5 or gap lap joints. This improves the anchoring performance of the third beam main reinforcement 33 to the RC wall 2, thereby reducing the length of the third beam main reinforcement 33 embedded inside the RC wall 2. Furthermore, it also reduces the need to provide anchoring devices such as plate nuts or anchors for the third beam main reinforcement 33. As a result, the amount of main reinforcement of the RC beam 3C is greater at the beam end than at the beam center, which reduces damage to the beam end of the RC beam 3C or the RC wall 2 during an earthquake and improves seismic performance. Furthermore, it is possible to suppress the increase in costs associated with providing the third beam main reinforcement 33.

[0029] The third beam main reinforcement 33 is arranged in multiple stages in the vertical direction, and is provided with closed-type shear reinforcement 34 at the end 3s of the RC beam 3C, surrounding the second beam main reinforcement 32a on the upper end 3t side, the second beam main reinforcement 32b on the lower end 3b side, and the third beam main reinforcement 33 of each stage; closed-type upper restraint reinforcement 39a surrounding the second beam main reinforcement 32a on the upper end 3t side and the third beam main reinforcement 33a of the top stage; and closed-type lower restraint reinforcement 39b surrounding the second beam main reinforcement 32b on the lower end 3b side and the third beam main reinforcement 33b of the bottom stage, so that the second beam main reinforcement 32 and the third beam main reinforcement 33 are doubly surrounded by the shear reinforcement 34 and the upper restraint reinforcement 39a or the lower restraint reinforcement 39b. With this configuration, the second beam main reinforcement 32 and the third beam main reinforcement 33 arranged on the end 3s side of the RC beam 3C are doubly surrounded by closed upper and lower restraint reinforcements 39a and 39b, which surround the second beam main reinforcement 32 and the third beam main reinforcement 33, and the shear reinforcement 34. This restrains the concrete portion that forms the beam cross section on the end 3s side of the RC beam 3C. This increases the strength of the concrete against compressive failure, and suppresses damage to the RC wall 2 during an earthquake.

[0030] In the second variant described above, at the beam end of the RC beam, the second beam main reinforcement 32 and the third beam main reinforcement 33 are surrounded by shear reinforcement 34 and restraining reinforcement 39, but the restraining reinforcement 39 may not be provided and the second beam main reinforcement 32 and the third beam main reinforcement 33 may be surrounded by shear reinforcement 34 only. Alternatively, the structure may be configured to include only shear reinforcement 34 and upper restraint reinforcement 39a, but not lower restraint reinforcement 39b, with the second beam main reinforcement 32a on the upper end 3t side and the third beam main reinforcement 33a in the uppermost row surrounded by the upper restraint reinforcement 39a, and the second beam main reinforcement 32b on the lower end 3b side and the third beam main reinforcement 33b in the lowermost row not surrounded by the lower restraint reinforcement 39b. Furthermore, it is also possible to have only shear reinforcement 34 and lower restraint reinforcement 39b, but no upper restraint reinforcement 39a, so that the second beam main reinforcement 32a on the upper end 3t side and the third beam main reinforcement 33a in the uppermost row are not surrounded by the upper restraint reinforcement 39a, and the second beam main reinforcement 32b on the lower end 3b side and the third beam main reinforcement 33b in the lowermost row are surrounded by the lower restraint reinforcement 39b.

[0031] Furthermore, in the second modified example, the third beam main reinforcement 33 is provided in two vertical rows, but it may be provided in only one row. In this case, the third beam main reinforcement 33 in one row may be surrounded only by the upper restraint reinforcement 39a, or may be surrounded only by the lower restraint reinforcement 39b. Alternatively, the third beam main reinforcement 33 in one row may be surrounded from both above and below by both the upper restraint reinforcement 39a and the lower restraint reinforcement 39b. The third beam main reinforcement 33 in one row may be configured so as not to be surrounded by either the upper restraint reinforcement 39a or the lower restraint reinforcement 39b. Alternatively, the third beam main reinforcement 33 may be provided in three or more stages. The third beam main reinforcement 33 that is not located at the top or bottom stage but is located between them may be surrounded only by the upper restraint reinforcement 39a or only by the lower restraint reinforcement 39b. Alternatively, the third beam main reinforcement 33 located in the middle may be surrounded from above and below by both the upper restraint reinforcement 39a and the lower restraint reinforcement 39b. The third beam main reinforcement 33 located in the middle may be configured so as not to be surrounded by either the upper restraint reinforcement 39a or the lower restraint reinforcement 39b.

[0032] In addition to the above, the configurations given in the above embodiments can be selected or changed as appropriate to other configurations without departing from the spirit of the present invention. [Explanation of symbols]

[0033] 1A~1C RC wall frame 32 2nd beam main reinforcement 2 RC wall 32a Second main beam reinforcement on the upper end side 3, 3C RC beam 32b Second main beam reinforcement on the bottom end 3c Center part 33 3rd beam main reinforcement 3s End 33a Third main beam bar at the top 3t Top end 33b Third main beam reinforcement at the bottom 3b Bottom end 34 Shear reinforcement 5 Lap joint 37 Reinforcement joint 23 Wall horizontal reinforcement 39a Upper restraint reinforcement 31 1st beam main reinforcement 39b Lower restraint reinforcement

Claims

1. An RC wall frame comprising an RC wall and an RC beam joined to the RC wall, The main beam reinforcement provided at the end side of the RC beam is arranged extending inside the RC wall and is joined to the horizontal wall reinforcement arranged horizontally inside the RC wall via a lap joint or a gap lap joint, Some of the beam main reinforcements on the end side are connected to the beam main reinforcements on the central side of the RC beam, and the other beam main reinforcements are cut-off reinforcements arranged only on the beam end side. RC wall structure characterized by:

2. The main beam bars at the end portions are larger in diameter or higher in strength than the main beam bars at the center portions.

2. The reinforced concrete wall structure according to claim 1.

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