JP5530403B2 - Joint structure of beam member and vertical member - Google Patents

Description

  The present invention relates to a joint structure between a beam member and a vertical member. In particular, the present invention relates to a concrete joint structure between a beam member made of a precast member formed of a fiber reinforced cementitious material and a vertical member.

  In the structural design of a building, it is necessary to ensure toughness so that the yield strength does not drop suddenly even if a member breaks due to a large earthquake or the like. Therefore, by designing the structural member such as a beam or a column to be bent and yielded before shear yielding, it is possible to prevent the yield strength from being suddenly lowered due to shear failure. Particularly in a concrete structure, it is desirable to increase the ratio of the beam length to the beam formation so that the beam yields before the shear yield, and avoids short span beams with a short beam length.

  However, in practice, it is necessary to provide a short span beam in a concrete structure due to restrictions such as site shape, plan of a building, arrangement plan of structural members such as earthquake resistant walls.

  In recent years, a structure has been proposed in which a core wall is provided in the core portion of a high-rise building, and most of the seismic force is borne by this core wall. In such a structure, a core wall with a small opening width is often planned, and the beam provided on the opening is a short span beam.

  As described above, since the short span beam is forced to undergo a large deformation under high stress such as during a large earthquake, it is necessary to have excellent deformability and a large shear strength during large deformation.

  Therefore, it is conceivable to form a concrete structure such as a beam member from a fiber-reinforced fiber-reinforced cement-based material that is made tough by mixing short fibers into the cement-based material. For example, Patent Document 1 describes a fiber-reinforced cement-based material in which PVA (Polyvinyl Alcohol polyvinyl alcohol) vinyl fibers are mixed into a cement-based material and the tensile strain of the cured body is 1% or more. Yes.

  Patent Document 2 describes that a short span beam is constructed by a precast member having a central portion made of a fiber-reinforced cement-based material and both end portions made of a normal concrete material.

JP 2000-7395 A Japanese Patent No. 3942973

  However, as a result of the inventor of the present application creating a test body in which the entire short span beam is made of a fiber-reinforced cement-based material and carrying out a positive and negative alternating force test on a concrete structure made of this test body, It was found that the shear strength suddenly decreased with fractures smaller than expected.

  In view of the above, the present invention is excellent in toughness when a beam member is greatly deformed in a connection structure between a beam member such as a short span beam made of a fiber-reinforced cement-based material and a vertical member such as a seismic wall or a column. It is an object to provide a bonded structure.

  In the above experiment, it is considered that the main factor of the beam reinforcement is as follows because the beam reinforcement broke and the shear strength suddenly decreased with a smaller deformation than expected.

  When skin contact occurs between the joint surface of the beam member and the vertical member, a gap is formed in a fan shape centering on the compression side end of the joint surface. When the load is reduced, the fan is closed and the gap is reduced. When the tensile load is applied, the main beam of the beam pulls out from the gap between the joints and extends. Deform. Thereafter, when a tensile load is applied again, the buckled portion is forcibly extended. As a result of such repetition, it is considered that the fatigue of the beam main reinforcement accumulates in the range where buckling has occurred, leading to fracture.

  In the case of a beam member made of ordinary concrete, the concrete at the corner portion of the beam member is cracked greatly by a relatively small deformation, and the beam main bar is not restrained. For this reason, the expansion and contraction of the main beam of the beam mainly occurs in the beam member, and it is difficult for fatigue to accumulate in a specific location in the main beam of the beam, and the buckling is restrained by the stirrup of the beam member.

  On the other hand, in the case of a beam member made of a fiber reinforced cementitious material, large cracks and dropouts do not occur at the corners of the beam member even if it is greatly deformed. It occurs only in a narrow area up to the vertical line. For this reason, fatigue tends to accumulate in the main beam of the beam and buckling is likely to occur because there is no constraint such as stirrup. In this way, it is considered that the shear strength suddenly decreases with a deformation smaller than expected.

  The present invention is a precast member made of a fiber-reinforced cement-based material in which a beam main bar and a stirrup are embedded in advance and mixed with short fibers in cement, a beam member in which the beam main bar protrudes from a side end surface, and a vertical bar It is a joint structure with a vertical member made of concrete with transverse bars arranged orthogonally, wherein the beam main reinforcing bars and the vertical bars are arranged orthogonally, and the vertical member is closest to the beam member side. An end stirrup surrounding the plurality of protruding beam main bars is disposed between the longitudinal bars and the side end surfaces of the beam members, and is formed by placing concrete. .

  As described above, in the process of closing the fan-shaped gap, the outward force of the sector acts on the beam reinforcing bar, and the core concrete (concrete in the reinforcing bar) prevents the beam member from deforming in the center direction. Buckles in the outer circumferential direction of the beam member cross section. Therefore, in the present invention, the end stirrup surrounding the periphery of the plurality of beam main bars protruding from the beam member is disposed between the vertical bar on the beam member side of the vertical member and the side end surface of the beam member. . By the binding force of the end stirrup, deformation can be suppressed in the outer circumferential direction of the beam member cross section of the beam main reinforcement, and the beam main reinforcement can be prevented from buckling. Thereby, the toughness when the beam member is greatly deformed becomes excellent.

  In order to install the end stirrup, it is necessary to set the distance between the side end face of the beam member and the vertical streak of the vertical member closest to the beam member side. is there. When the beam type is projected from the vertical member side to the side end surface of the beam member, this protruding part is likely to be cracked easily in the cover concrete like the beam end part of ordinary concrete, and the beam member is made of fiber reinforced cementitious material. The advantage is poor.

  Therefore, in the present invention, concrete may be applied to the side surface of the vertical member such that the side end surface of the vertical member on the beam member side exceeds the end surface of the beam member in the inner direction of the beam member. preferable.

  Thereby, the outstanding performance of the beam member by comprising a fiber reinforced cement-type material can fully be exhibited.

  Furthermore, in the present invention, it is preferable that a column inner end stirrup surrounding the periphery of the protruding beam main bar is disposed inside the vertical member inside the vertical member closest to the beam member of the vertical member. .

  In this case, the column inner end stirrup serves to prevent the beam main bar from being deformed in the outer peripheral direction of the beam member in the vertical member, and can assist the buckling suppression function by the end stirrup.

The top view which shows the joining structure of the short span beam member and core wall which concern on embodiment of this invention. The side view which shows the joining structure of a short span beam member and a core wall. The side view of a short span beam member. The top view of a short span beam member. The side view which shows the reinforcement arrangement | positioning of a core wall. The side view which shows the state which built the short span beam member in the reinforcement of the core wall.

  A joint structure between a beam member and a vertical member according to an embodiment of the present invention will be described with reference to the drawings. Here, with reference to FIG.1 and FIG.2, the joining structure of the short span beam member 10 which is a beam member, and the core wall 20 which is a vertical member is demonstrated. In addition, a short span beam means a beam with a span ratio of about 1.2 to 1.5.

  The short span beam member 10 is a precast member made of a fiber reinforced cementitious material (or fiber reinforced mortar material). Fiber reinforced cement-based materials are randomly dispersed in a three-dimensional direction in a cement matrix using short fibers such as carbon fiber, aramid fiber, glass fiber, PVA (vinylon) fiber, polyethylene fiber, polypropylene fiber, and steel fiber as a reinforcing material. It is a thing. A precast member made of such a mixed fiber-reinforced cement-based material has high deformability and excellent toughness.

The fiber reinforced cementitious material includes, as an example, 1.0 to 2.0% of PVA short fibers having a diameter of 0.04 mm, a length of 12 mm, and a strength of 1600 N / mm ² , a thickener, a high-performance AE water reducing agent, and shrinkage. Reducer and expansion agent are mixed, material strength Fc is 30 to 48 N / m ² , water cement ratio is 35 to 55%, slump flow is 50 ± 7.5 cm, air amount is 8.0 ± 1.5% Things can be used.

  In the embodiment, referring to FIG. 3 and FIG. 4, a short span beam member 10 is a precast in which a plate-like floor slab body 12 is integrated with a top of a beam main body 11 constituting a short span beam and provided by precast. It is a composite beam.

  A plurality of beam main bars 13 and a plurality of star wraps (shear reinforcement bars) (not shown) that restrain the beam main bars 13 are embedded in the beam main body 11 in advance. A plurality of beam main bars 13 protrude from both end faces in the longitudinal direction of the beam body 11.

  A plurality of slab muscles 14 are embedded in the floor slab body 12 in advance. Reinforcing bar joints (relay joints) 15 are connected to the end face portions of a plurality of slab bars (not shown) extending in the short direction in consideration of transportation. A plurality of slab muscles 14 extending in the longitudinal direction protrude from both end faces. In addition, the reinforcement arrangement | positioning of the short span beam member 10 should just be a conventionally well-known thing, and is not specifically limited.

  Further, a plurality of hoop bars 17 temporarily fixed by a hoop rack 16 are arranged in advance in the protruding plurality of beam main bars 13 at intervals in the height direction. In addition, a plurality of stirrups 18 and 19 surrounding these beam main bars 13 are arranged in advance in the projecting direction at intervals in the protruding plurality of beam main bars 13. Here, one star wrap (end star wrap) 18 is located between the side end surface of the beam main body 11 and the hoop line 17 in a top view, and one or more (2 in the drawing) The star wrap (column inner end star wrap) 19 is located inside the hoop muscle 17 in a top view.

  Hereinafter, the construction method of the short span beam member 10 will be described.

  First, referring to FIG. 5, the reinforcing bars of the core wall 20 (see FIGS. 1 and 2) are assembled. A columnar reinforcing bar 23 composed of column main bars (longitudinal bars) 21 and hoop bars 22 is provided in a portion to be an end of the core wall 20 in preparation for stress concentration. A plurality of hoop bars 22 are arranged at intervals in the height direction so as to surround the plurality of columnar main bars 21 arranged in a planar rectangular shape.

  The vertical stripes 24 and the horizontal stripes 25 are disposed in the other portions of the core wall 20. A plurality of horizontal stripes 25 are arranged at intervals in the height direction perpendicular to the plurality of vertical stripes 24 arranged at intervals in the horizontal direction. Reinforcing bars 21 to 25 of the core wall 20 are fixed by width stop bars (not shown). The height of the hoop bars 22 and the horizontal bars 25 is less than the lower end surface of the short span beam member 10 to be built. In addition, the reinforcement arrangement | positioning structure of the core wall 20 should just be a conventionally well-known thing, and is not specifically limited.

  Then, referring to the left side of FIG. 6, the core wall mold 26 is assembled to the lower end of the short span beam member 10.

  Next, the short span beam member 10 in which the hoop bars 17 and the stirrups 18 and 19 are disposed in advance is built from above the core wall 20 using a lifting machine (not shown). At this time, a hoop bar 17 temporarily fixed to the beam main bar 13 protruding from the side end surface of the beam main body 11 is built so as to surround a plurality of column main bars 21 arranged in a plane rectangular shape, and the beam main bar 13 and the hoop bar 17 are embedded. And the column main reinforcement 21 are bound together with a binding wire or the like.

  Thereby, the end stirrup 18 connected in advance to the beam main bar 13 is located between the column main bar 21a closest to the beam main body 11 and the side end surface of the beam main body 11, and the column inner end stirrup 19 is It will be located in the inside of the plane rectangular shape which column main reinforcement 21 forms.

  Next, the remaining horizontal bars 25 of the core wall 20 are arranged, and these horizontal bars 25 are connected to the beam main bars 13. Then, referring to the right side of FIG. 6, the remaining core wall mold 27 is installed. Further, although not shown, the floor slab body 12 is connected in the longitudinal direction of the floor slab body 14, the slab reinforcement is connected to the reinforcing bar joint 15 in the short direction, and the floor slab is not shown up to the top of the slab. Build floor formwork.

  Next, referring to FIGS. 1 and 2, concrete is placed to form the core wall 20. The concrete material may be ordinary concrete or high strength / ultra high strength concrete.

  Thereafter, the formwork of the floor slab is removed from the mold, and although not shown, the reinforcement and the formwork are assembled with respect to other than the core wall 20, and concrete is placed. Finally, demold. Thereby, the joining structure of the short span beam member 10 and the core wall 20 is completed.

  As described above, in the joint structure of the short span beam member 10 and the core wall 20, the beam main body 11 is a precast member made of a fiber-reinforced cement material, so that fine cracks are dispersed throughout the member and the entire member is Since it elongates, the yield strength does not drop rapidly until the deformation amount increases. In addition, since large cracks are unlikely to occur, the building can be used with simple repairs even when damaged by an earthquake.

  An end stirrup 18 that surrounds the plurality of beam main bars 13 protruding from the beam main body 11 is disposed between the column main bars 21 a closest to the beam main body 11 and the side end surfaces of the beam main body 11.

  The end stirrup 18 prevents the beam main bar 13 from being deformed in the outer circumferential direction of the beam main body 11 in the process in which the tensile force is unloaded and turned into a compressive force after the beam main bar 13 is pulled out by the tensile force. Thus, the end stirrup 18 functions to suppress buckling of the beam main bars 13. Therefore, the beam body 11 has excellent toughness when greatly deformed.

  In addition, a column inner end stirrup 19 is disposed on the beam main bar 13 inserted into the reinforcing bar 23 of the core wall 20. The column inner end stirrup 19 functions to prevent the main beam 13 from being deformed in the outer peripheral direction of the beam main body 11 by the core wall 20, and assists the buckling suppression function by the end stirrup 18.

  By the way, since the end stirrup 18 is installed, the distance between the side end face of the beam main body 11 and the reinforcing bar 23 of the core wall 20 is increased, and the normal concrete cover thickness cannot be accommodated. When the beam mold is projected from the core wall 20 side to the side end face of the beam body 11, this projection is covered with the same concrete as the beam end, and the concrete is likely to be cracked greatly. The advantage made of materials is poor.

  Therefore, referring to FIG. 1 and FIG. 2, the portion of the side end face side of the beam main body 11 with the space between the rebar cage 23 of the core wall 20 is increased, and concrete is added to the entire side surface of the core wall 20. It is preferable to extend the core wall 20 in the inner direction of the beam body 11 so as to exceed the side end surface of the beam body 11. In this case, the position of the rebar cage 23 is not changed, and if the additional striking portion 28 becomes large, the staking bar 29 may be arranged as necessary to prevent cracks in the concrete.

  Although the embodiment of the present invention has been described above with reference to the drawings, the present invention is not limited to this. For example, although the short span beam member 10 which is a beam member and the core wall 20 which is a vertical member have been described, the present invention is not limited to this. For example, the beam member may be a long span beam member. A plurality of end stirrups 18 may be disposed between the side end surface of the beam main body 11 and the column main reinforcement 21a closest to the beam main body 11. The vertical member may be a load bearing wall or a column other than the core wall.

  DESCRIPTION OF SYMBOLS 10 ... Short span beam member (beam member), 11 ... Beam main body, 12 ... Floor slab body, 13 ... Beam main reinforcement, 14 ... Slab reinforcement, 15 ... Reinforcement joint, 16 ... Hoop rack, 17 ... Hoop reinforcement, 18 ... End Part stirrup, 19 ... inner end part star wrap, 20 ... core wall (vertical member), 21 ... column main reinforcement (vertical reinforcement), 21a ... column main reinforcement on the shortest span beam side, 22 ... hoop reinforcement, 23 ... rebar Cage, 24 ... vertical streak, 25 ... horizontal streak, 26 ... core wall formwork, 27 ... remaining core wall formwork, 28 ... extra striking part, 29 ... swarf streak.

Claims (3)

The beam main reinforcement and stirrup are pre-embedded, and are precast members made of a fiber-reinforced cement-based material in which short fibers are mixed in cement, and the beam main protrusion protrudes from the side end surface,
Longitudinal and transverse bars are arranged perpendicular to each other, and it is a joint structure with a vertical member made of concrete,
The beam main bars and the vertical bars are arranged orthogonally, and the plurality of protruding beam main bars protrude between the vertical bars closest to the beam member of the vertical member and the side end surfaces of the beam members. An end stirrup surrounding the periphery of the steel is disposed, and is formed by casting concrete.   2. The concrete is reinforced on the side surface of the vertical member such that the side end surface of the vertical member on the beam member side exceeds the end surface of the beam member in the inner direction of the beam member. The joining structure of the beam member and vertical member as described in 2.   The column inner end stirrup surrounding the periphery of the protruding beam main bar is disposed inside the vertical member inside the vertical member closest to the beam member of the vertical member. The joint structure of the beam member of Claim 2, and a vertical member.

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