JP5726590B2 - Connection structure of reinforced concrete beams or columns - Google Patents

Description

  The present invention relates to a joint structure of beams or columns made of reinforced concrete.

  When the load of a reinforced concrete beam is increased, the bending stress increases, and when the elastic limit of the concrete is exceeded, the beam enters the plastic zone from the joint end (outermost edge). When the entire cross section reaches the plastic region, one side (for example, the upper surface side) of the neutral shaft is subjected to plastic compression and the other side (for example, the lower surface side) is subjected to plastic tension. In this state, the beam continues to rotate like a hinge while the bending moment remains constant. The moment in this state is the total plastic moment, and the mechanical state of the cross section of the beam having the total plastic moment is the plastic hinge. In other words, the hinge is a pin state formed by yielding the cross section of the member by a load.

  In a reinforced concrete structure, energy input at the time of an earthquake is generally configured to be absorbed by a plastic hinge formed at the beam end of each floor. Therefore, a portion where a plastic hinge is supposed to be formed is densely arranged with a shear reinforcement bar or a band for the purpose of preventing brittle fracture and providing sufficient strength and rotational deformation capability.

  In Patent Document 1, a beam is constructed with a precast beam member in which a range in which a plastic hinge is assumed to be formed at the beam end portion is formed of a fiber-reinforced cement material and an intermediate portion between the beam end portions is formed of ordinary concrete. This increases the plastic deformation and rotation capacity of the beam end and enables the seismic response control of the entire building.In addition, the deformation capacity is increased while reducing the amount of shear reinforcement at the beam end, and the large seismic energy absorption capacity as a whole. Has been proposed (see Patent Document 1).

  Here, when a load is applied to the beam and the plastic hinge portion at the end of the beam is rotationally deformed and the reinforcing bar expands and yields, the yielded region becomes a plastic deformation region and shear cracks (cracks) occur in the concrete. In addition, since the cracked part closes when the load is removed, the expanded and yielded reinforcing bar is pushed into the concrete section. And by repeating this, the adhesion property with concrete gradually deteriorates. That is, the adhesion characteristic of the reinforcing bar to the concrete due to the repeated deformation of the plastic hinge part at the beam end portion is deteriorated, whereby the energy absorbing ability of the reinforcing bar is lowered and the restoring force characteristic is lowered.

  From another point of view, in a reinforced concrete structure, it is not possible to form a hysteresis characteristic of complete elastoplasticity like steel structure, so the load is applied to the beam and the plastic hinge part at the end of the beam is repeatedly rotated and deformed. Restoring force characteristics are reduced.

Patent 3999591

  In view of the above, it is an object of the present invention to improve the energy absorption capability of a beam end portion of a reinforced concrete beam or a column end portion of a column of a reinforced concrete beam.

The invention of claim 1 is joined to a beam or column made of reinforced concrete and a frame to which the beam or the column is joined, and is deformed along with the rotational deformation of the beam end portion or the plastic hinge portion of the column end portion to thereby save energy. Energy absorbing means for absorbing, the energy absorbing means, the corrugated steel plate arranged with the direction perpendicular to the beam length direction or the column length direction as the crease direction, and the end or column length of the corrugated steel plate in the beam length direction The first fixing means for fixing the end of the direction to the housing, and the convex portion of the corrugated steel plate are fixed to the surface of the beam or the column with the beam length direction or the direction perpendicular to the column length direction as the out-of-plane direction. Second fixing means .

  In the invention of claim 1, when a load is applied to a reinforced concrete beam or column and the plastic hinge part at the beam end or the column end is rotationally deformed and the reinforcing bar is expanded and yielded, the yielded region becomes the plastic deformation region. At the same time, shear cracks occur in the concrete. Moreover, the adhesion property of the reinforcing bars to the concrete deteriorates.

  However, even if shear cracks (cracks) enter the reinforced concrete beam or column in this way and the adhesion characteristics of the reinforced concrete to the concrete deteriorate, the energy at the time of rotational deformation of the plastic hinge part at the beam end or column end is reduced. The energy absorbing means absorbs.

  Therefore, the energy absorption capacity of the beam end portion or the column end portion of the reinforced concrete beam is improved as compared with the configuration without the energy absorption means.

In addition, the corrugated steel sheet repeatedly undergoes plastic deformation along with the rotational deformation of the plastic hinge portion at the beam end or the column end, thereby absorbing energy when the plastic hinge portion at the beam end or the column end is rotationally deformed. To do. Therefore, the energy absorption capability of the beam end portion or the column end portion is improved.

  As described above, according to the present invention, the energy absorption capability of the beam end portion of the reinforced concrete beam or the column end portion of the column can be improved as compared with the configuration without the energy absorption means.

It is a perspective view which shows the beam edge part joined to the pillar by the joining structure of the beam made from a reinforced concrete which concerns on 1st embodiment of this invention. It is a top view which shows the beam end part shown in FIG. (A) is a side view which shows the beam end part shown in FIG. 1, (B) is a side view which shows the state which the plastic hinge part of the beam end part rotationally deformed. It is a perspective view which shows the beam edge part joined to the pillar by the joining structure of the beam made from a reinforced concrete which concerns on the modification of 1st embodiment of this invention. It is a top view which shows the beam end part shown in FIG. (A) which shows the beam edge part joined to the pillar by the joining structure of the beam made from a reinforced concrete which concerns on 2nd embodiment of this invention is a top view, (B) is a perspective view. (A) is sectional drawing of the direction orthogonal to the crease direction which shows the corrugated steel plate used for the beam edge part joined to the column by the joining structure of the beam made from reinforced concrete which concerns on 1st embodiment, (B)- (D) is sectional drawing which shows the variation of a corrugated steel plate. It is a side view shown in the partial cross section which shows the damper apparatus as another example of an energy absorption means.

<First embodiment>
The joint structure of the reinforced concrete beam which concerns on 1st embodiment of this invention is demonstrated using FIGS. 1-3.

  As shown in FIGS. 1, 2, and 3A, a reinforced concrete column 20 and a reinforced concrete beam 50 of a structure 10 are joined to a reinforced concrete beam connection structure according to the first embodiment of the present invention. Is applied and joined.

  The beam length (longitudinal) direction of the beam 50 is the X direction, the vertical direction is the Z direction, and the direction orthogonal to the X direction and the Z direction is the Y direction. Further, the Y direction is the beam width direction of the beam 50 (a direction orthogonal to the beam length direction in plan view).

  The beam 50 and the column 20 have a so-called reinforced concrete structure composed of concrete Q reinforced by embedding reinforcing bars.

  A plurality of main reinforcing bars 40 arranged in the vertical direction and a plurality of shear reinforcing bars (not shown) arranged in a direction orthogonal to the main reinforcing bars 40 are embedded in the column 20.

  The beam 50 is arranged along the beam length direction (axial direction), a plurality of main bars 42 arranged across the beam 50 and the column 20, and a bar arranged along the direction orthogonal to the main bars 42. Shear reinforcement bars (not shown) are embedded. The main bars 42 are arranged on the upper side and the lower side of the neutral axis S in the vertical direction of the beam 50.

  Concave portions 54 recessed inward in the beam width direction are formed on both side surfaces (elevation surfaces) 50A of the beam end portion 52 joined to the column 20 in the beam 50.

  An energy absorption mechanism 90 is provided in the recess 54. The energy absorbing mechanism 90 has a corrugated steel plate 100. As shown in FIG. 7A, the corrugated steel plate 100 is a corrugated steel plate having a cross-sectional shape in which peaks (convex portions) 102 and valleys (concave portions) 104 are alternately formed. And in the recessed part 54, the corrugated steel plate 100 is arrange | positioned by making the corrugated folding line direction into the vertical direction.

  In addition, the cross-sectional shape of the corrugated steel plate 100 may be a corrugated shape, and may be, for example, the corrugated steel plates 400, 410, and 420 having the cross-sectional shapes of FIGS. Moreover, as a material which comprises a corrugated steel plate, normal steel (for example, SM490, SS400 etc.), low yield point steel (for example, LY225 etc.), etc. can be used.

  As shown in FIGS. 1, 2, and 3 (A), one end 110 in the direction (beam length direction (Y direction)) orthogonal to the bending direction of the corrugated steel plate 100 is joined to the column 20. Yes. The other end 112 is joined to the side wall 56 of the recess 54 of the beam end 52. Further, the apex portion of the convex portion 102 that is convex toward the beam side (the vertical surface 58 side) of the corrugated steel plate 100 is joined to the vertical surface 58 of the concave portion 54 of the beam end portion 52.

  In this embodiment, each joining site | part of the corrugated steel plate 100 is joined by the anchor bolt 25 and the nut 28 of the post-installation type. However, a joining member and a joining method are not limited to this. It may be joined by a member or method other than the anchor bolt 25 and the nut 28.

  Note that the concrete Q constituting the beam 50 is not placed in the concave portions (valley portions) 104 between the convex portions 102 of the corrugated steel plate 100.

<Action and effect>
Next, functions and effects of the present embodiment will be described.

  When a load is applied to the reinforced concrete beam 50 and the plastic hinge portion of the beam end 52 is rotationally deformed, when the main bar 42 expands and yields, the yielded region becomes the plastic deformation region and the concrete Q constituting the beam 50 Shear cracks (cracks) occur (see crack K in FIG. 3B). In addition, the adhesion characteristic of the main reinforcement 42 to the concrete Q due to the repeated deformation of the plastic hinge portion of the beam end 52 is deteriorated, thereby reducing the energy absorption capability of the main reinforcement 42.

  Here, the corrugated steel plate 100 has a high shear resistance to a force in a bending line direction (vertical direction (Z direction) in the present embodiment) perpendicular to the corrugated direction, but the corrugated direction (beam in the present embodiment). In the long direction (X direction), it expands and contracts freely like an accordion of a musical instrument.

  Therefore, in this embodiment, when the plastic hinge part of the beam end part 52 is rotationally deformed, the corrugated steel sheet 100 expands and contracts like an accordion in the corrugated direction (lateral direction) (refer to plastic deformation repeatedly (see FIG. 3B)). ).

  Therefore, even if shear cracks (cracks) enter the beam 50 made of reinforced concrete and the adhesion characteristics of the main reinforcement 42 to the concrete Q deteriorate, the corrugated steel sheet 100 expands and contracts (repeatedly plastic deformation) like an accordion in the lateral direction. The energy when the plastic hinge portion of the beam end 52 is rotationally deformed is absorbed. Therefore, compared with a configuration in which the energy absorption mechanism 90 is not provided (a configuration in which the corrugated steel plate 100 is not bonded), the beam end 52 energy absorption capability is improved.

  If it demonstrates from another viewpoint, even if it is a reinforced concrete structure, it will become possible to form the hysteresis characteristic of complete elastoplasticity (or substantially complete elastoplasticity) like a steel frame structure, a load will be applied to the beam 50, and beam end part 52 will be applied. The deterioration of the restoring force characteristic due to repeated rotational deformation of the plastic hinge portion is suppressed.

  Since the concrete Q constituting the beam 50 is not placed in the concave portion (valley portion) 104 between the convex portions (mountains) 102 of the corrugated steel plate 100, the horizontal expansion and contraction of the corrugated steel plate 100 is not hindered. .

  In this embodiment, a concave portion 54 is formed in the beam end portion 52, the corrugated steel plate 100 is disposed in the concave portion 54, and the corrugated steel plate 100 is configured not to protrude outside in the width direction of the beam 50. . However, there may be a configuration in which the corrugated steel plate 100 is joined to the side surface (elevation surface) 50A without the recess 54.

  Here, for example, in the case of a flat steel plate, it hardly expands or contracts in the lateral direction. Therefore, when a flat steel plate is used instead of the corrugated steel plate 100, formation of the plastic hinge at the beam end portion 52 is inhibited and rotational deformation is suppressed, so that the energy absorption effect by the plastic hinge (rotational deformation) is not sufficiently exhibited. On the other hand, since the corrugated steel sheet 100 expands and contracts like an accordion in the corrugated direction, a plastic hinge is formed at the beam end 52 and is rotationally deformed. Therefore, the energy absorption effect by the plastic hinge (rotational deformation) is effectively obtained. Demonstrated.

"Modification"
Next, a modified example of the present embodiment will be described with reference to FIGS.

  In the beam end portion 52 of the beam 50, a hollow portion 60 penetrating in the vertical direction is formed. The cavity 60 has an elongated rectangular shape whose vertical section has the beam length direction (X direction) as a longitudinal direction, and is formed at a substantially central portion in the beam width direction (Y direction).

  An energy absorption mechanism 92 is provided in the hollow portion 60. One end 110 in a direction (beam length direction (Y direction)) perpendicular to the bending direction of the corrugated steel plate 100 is joined to the column 20. The other end 112 is joined to the side wall 66 of the cavity 60 of the beam end 52. Further, the apex portion of the convex portion 102 that is convex toward the beam side (the upright surface 58 side) of the corrugated steel plate 100 is joined to the compatible surface 68 of the hollow portion 60 of the beam end portion 52.

  Note that the concrete Q constituting the beam 50 is not placed in the concave portion (valley portion) 104 of the corrugated steel plate 100.

"Other examples"
Although not shown in the drawings, a filling material made of a material that can be easily deformed (compressed), such as polystyrene foam, is filled in the concave portion 54 (see FIG. 1) and the hollow portion 60 (see FIG. 4) of the beam end portion 52. It may be. In this case, the concave portion (valley portion) 104 of the corrugated steel plate 100 is also filled with the filler, but the filler is compressed and easily crushed, so that the corrugated steel plate 100 does not hinder lateral expansion and contraction.

<Second embodiment>
With reference to FIG. 6, a description will be given of a joint structure of reinforced concrete beams according to a second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the member same as 1st embodiment, and the overlapping description is abbreviate | omitted.

  An energy absorbing mechanism 200 is provided in the recesses 54 formed on both side surfaces (elevation surfaces) 50 </ b> A of the beam end portion 52 of the beam 50. The energy absorption mechanism 200 includes two laminated flat plate-like steel plates 202 and 204.

  The steel plate 202 arranged on the inner side in the beam width direction is formed with a through hole (not shown) and the anchor bolt 25 is inserted. The diameter of the through hole (not shown) is a circular hole that is substantially the same as the shaft diameter of the anchor bolt 25 (more precisely, the through hole is slightly larger because it is inserted).

  An end 206 in the beam length direction (beam length direction) of the steel plate 204 arranged on the outer side in the beam width direction is joined to the column 20 with an anchor bolt 25. Further, the steel plate 204 is formed with a long hole 210 having a substantially vertical direction as a longitudinal direction. Then, the anchor bolt 25 inserted through the through hole of the steel plate 202 is inserted into the long hole 210 and fastened by the nut 28. That is, the two laminated flat steel plates 202 and 204 are fastened together with the anchor bolt 25 and the nut 28.

  The long hole 210 is formed larger than the shaft diameter of the anchor bolt 25 and has an R shape that is slightly convex toward the direction away from the column 20.

<Action and effect>
Next, functions and effects of the present embodiment will be described.

  As the plastic hinge portion of the beam end portion 52 is rotationally deformed, the anchor bolt 25 that fastens the steel plates 202 and 204 is moved. Since the steel plate 202 on the inner side in the beam width direction is not joined to the column 20 and the shaft diameter of the through hole and the anchor bolt 25 is substantially the same, the steel plate 202 moves as the anchor bolt 25 moves. In other words, the steel plate 202 moves as the beam end 52 rotates.

  On the other hand, in the steel plate 204 on the outer side in the beam width direction, the end 206 is joined to the column 20 and the anchor bolt 25 is inserted into the long hole 210, so that the steel plate 202 does not move and the anchor bolt 25 has the long hole 210. To move. That is, the steel plate 204 does not move even if the beam end portion 52 is rotationally deformed.

  Accordingly, with the rotational deformation of the beam end portion 52, the steel plate 202 on the inner side in the beam width direction and the steel plate 204 on the outer side in the beam width direction move relative to each other, and a frictional force is generated at the contact surface 203 between the steel plate 202 and the steel plate 204. The energy is absorbed by the frictional force generated on the contact surface 203. That is, by providing the energy absorption mechanism 200, the energy absorption capability of the beam end portion 52 is improved.

  In addition, the structure which absorbs energy using a friction force with another structure may be sufficient. For example, an existing friction damper may be used. In short, it has a first member joined to the frame and a second member joined to the beam and in contact with the first member, and the first member moves in accordance with the rotational deformation of the plastic hinge portion at the end of the beam. And what is necessary is just to be comprised so that energy may be absorbed by the frictional force which generate | occur | produces in the contact surface of a 1st member and a 2nd member.

<Others>
By applying the present invention and improving the history of a beam made of reinforced concrete, the structural characteristic coefficient DS of the beam can be reduced. Further, by applying the present invention, for example, if the DS is reduced by 0.05, more specifically, from 0.30 to 0.025, the retained horizontal proof stress is reduced by about 15%. Cost reduction and resource saving by reduction.

  The present invention is not limited to the above embodiment.

For example, the energy absorbing means may be an orifice type damper device 500 shown in FIG.
The damper device 500 includes a steel pipe 502 and a shaft member 510. The shaft member 510 is formed with a disk-shaped protrusion 512 that protrudes outward in the radial direction. This shaft member 510 is inserted into the steel pipe 502. The ends of the steel pipe 502 are fixed to both side surfaces (elevation surfaces) 50A of the beam end 52 of the beam 50 by fixing portions 504. The end of the shaft member 510 is embedded and fixed in the column 20.
Then, energy is absorbed by the resistance force generated by the shaft 510 moving in the steel pipe 502 as the plastic hinge portion of the beam end 52 rotates.

For example, in the said embodiment, although the energy absorption mechanism was arrange | positioned in the standing surface of the beam end part 52 joined to the pillar 20 in the beam 50, it is not limited to this. For example, energy absorbing mechanisms may be disposed on the upper and lower surfaces of the beam end portion 52. In this case, energy is effectively absorbed with respect to the moment in the vertical direction. Moreover, the energy absorption mechanism should just be provided in the at least 1 surrounding surface among the four surrounding surfaces of a beam end part (it may be provided in all four surrounding surfaces). Further, even in the case of a beam having a non-square cross section, an energy absorbing mechanism may be provided on at least one peripheral surface.
Moreover, you may arrange | position to the upper and lower surfaces of the cavity part which penetrates a beam to a horizontal direction (structure which rotated 90 degrees of the modification of 1st embodiment).
In short, what is necessary is just to provide in the surface which makes the direction orthogonal to the beam length direction in a beam an out-of-plane direction.
The “elevation surface” is a surface in which the beam width direction orthogonal to the beam length direction in plan view is an out-of-plane direction.

Further, for example, in the above embodiment, the present invention is applied to the beam end portion, but the present invention is not limited to this. The present invention can be applied to the column end. When the present invention is applied to the column end, a configuration in which the beam arranged in the horizontal direction in the above embodiment is rotated 90 ° and arranged in the vertical direction (for example, applied to a joint portion between the column end and the slab) The configuration is substantially the same.
In addition, when a pillar is a square pillar, it is desirable to provide energy absorption mechanisms, such as a corrugated steel plate, in two surrounding peripheral surfaces (side surface). Furthermore, it is more desirable to provide energy absorption mechanisms such as corrugated steel sheets on the four peripheral surfaces (side surfaces).

  Furthermore, the above-described plurality of embodiments and the plurality of modified examples can be implemented in combination as appropriate. Moreover, it cannot be overemphasized that it can implement with a various aspect in the range which does not deviate from the summary of this invention.

20 pillars
25 Anchor bolt (energy absorbing means, first fixing means, second fixing means)
28 Nut (energy absorbing means, first fixing means, second fixing means)
42 Reinforcing bars (reinforcing bars)
50 Beam 52 Beam end 90 Energy absorption mechanism (energy absorption means)
100 Corrugated steel sheet (energy absorption means)
200 Energy absorption mechanism (energy absorption means)
202 Steel plate (energy absorbing means, second member)
204 Steel plate (energy absorbing means, first member)
203 Contact surface 500 Damper device (energy absorbing means)

Claims (1)

An energy absorbing means is provided which is joined to a beam or column made of reinforced concrete and a frame to which the beam or the column is joined, and is deformed and absorbs energy by the rotational deformation of the plastic hinge portion at the beam end or the column end. ,
The energy absorbing means is
Corrugated steel sheets arranged with the direction perpendicular to the beam length direction or the column length direction as the crease direction;
First fixing means for fixing the end of the corrugated steel sheet in the beam length direction or the end of the column length direction to the housing;
A second fixing means for fixing the convex portion of the corrugated steel plate to a surface having a beam length direction or a direction perpendicular to the column length direction in the beam or the column as an out-of-plane direction;
Having
Reinforced concrete beam or column joint structure.

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