JPH0913694A - Aseismatic reinforcing structure of existing column - Google Patents

Abstract

PURPOSE: To enhance aseismatic performance by improving shear bearing force of an existing column lacking in shear bearing force and a column hit by an earthquake. CONSTITUTION: An existing column 10 is covered with both side flange parts 20a of covering plate members 20 bent in an almost U shape in a plan view by holding a covering thickness between a covering plate members 20 and the existing column 10 by sandwiching the existing column 10 by the tips of plural anchor bars 22 which are bent at a prescribed bending angle and are juxtaposed in the column height direction of the existing column 10. The covering plate members 20 assembled around the existing column 10 are restricted by form restricting holding members. A filler is injected into a covering part from injection ports 26A formed in the covering plate members 20, and the existing column 10 and the covering plate members are integrally formed. Therefore, a work process such as field welding can be eliminated, and reinforcing work can be speedily and inexpensively performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seismic reinforcement structure for existing columns, and in particular, the columns of an existing building damaged by an earthquake or columns for which the shear strength of columns has been found to be insufficient by seismic diagnosis are made of steel plates. The present invention relates to a seismic retrofit structure for existing columns, which is covered and reinforced by a quick process to improve the toughness of the column member after the reinforcement.

[0002]

2. Description of the Related Art Generally, it is known that in a building damaged by an earthquake, the damage is concentrated on a weak portion in the building. In particular, in many buildings that have been aged for a long time, many of them are designed with insufficient shear strength of columns. In a recent disaster survey after the Great Hanshin Earthquake, a column collapsed due to shear failure of a column in a building built before the so-called "new earthquake-resistant" design standards, and an example of layer collapse was reported.

On the other hand, in existing buildings damaged by the Tokachi-oki Earthquake and Miyagiken-oki Earthquake, in order to reuse the existing buildings, the shear-damaged columns are reinforced, and various seismic resistances for improving the toughness of the reinforced columns are added. Reinforcement work was done. FIG. 8 is a column cross-sectional view showing an example of an earthquake-proof reinforcement structure of an existing column made of reinforced concrete. As shown in the figure, the seismic reinforcement structure of this existing column is such that a covering steel plate 52 is provided by providing a covering of a predetermined thickness around the damaged column 50, and a portion surrounded by the column 50 and the covering steel plate 52 is provided. It is filled with non-shrink mortar 54.
The coating steel plate 52 is composed of two steel plates obtained by bending a structural rolled steel plate into a substantially U-shape, encloses the column so as to sandwich it from both sides, and integrally welds the butt joints 56 in the field. Further, in order to secure a certain amount of covering around the pillar, a known spacer 5 is provided between the pillar 50 and the covering steel plate 52.
8 is interposed.

Next, a series of operations for constructing the seismic retrofit structure for existing columns shown in FIG. 8 will be described with reference to FIG. FIG. 9A shows an example of a column 50 in which an X-shaped shear crack 60 has occurred on the surface due to an earthquake. First, the exfoliated concrete in the portion where the shear crack has occurred is scraped out, and the concrete pieces crushed by compressed air or the like are removed so that the mortar to be filled later can be surely attached. Next, a covering steel plate 52 having a height up to the beam lower position 63 is built around the pillar 50 with a predetermined covering thickness, and as shown in FIG. Field weld butt joints 56 up to 63.
After that, in order to fill the voids in the overlaid portion between the pillar 50 and the coating steel plate 52, as shown in FIG. 7C, the gap between the floor surface 61 and the gap under the beam 63 is sealed with sealing material (not shown). No.), and the high-fluidity non-shrink mortar is pressure-fed using a mortar pump (not shown) and is injected from the lower injection port 64 provided at the lower end of the coating steel plate 52. The pressure feeding is performed until it is confirmed that a part of the mortar is discharged from the upper air vent port 65, and the inside is completely filled with the mortar up to the beam lower position 63. Through the work steps described above, the existing columns were reinforced by coating steel sheets and mortar filling, and the toughness of the reinforced columns was improved.

[0005]

However, the welding length of the butt joints of the coating steel sheets is almost equal to the column height, 3 m.
In addition, as shown in FIG. 8, since there are welding points at least at two points on both sides of the column, a series of reinforcing work time until filling the mortar becomes long and the construction cost as a whole becomes high. There's a problem. Further, in order to maintain the quality of the welded portion at least 3.2 mm or more in order to weld the coating steel sheet on site, it is necessary to bear sufficient shear strength in the mortar portion. However, it is necessary to use an oversized steel material, and it is expected that the cost of the material will increase.

Therefore, an object of the present invention is to solve the above-mentioned problems of the conventional technique and provide a seismic retrofit structure for existing columns in which a steel plate for coating is quickly built without performing on-site welding. Especially.

[0007]

In order to achieve the above object, the present invention provides a plurality of anchors that are bent at a predetermined bending angle on both side flange portions of a plate material that is bent into a substantially U-shape when viewed from above. A cover plate member having a bar in the column height direction of the existing column and covering the existing column, and provided around the coating plate member that covers the existing column, the deformation of the coating plate member. A mold restraint holding member for preventing displacement, the existing pillar is sandwiched by the tip of the anchor bar, and the existing thickness is maintained by holding the covering thickness between the covering plate member and the existing pillar. In the state where the pillar is covered and the form restraint holding member is provided, a filler is injected into the covering portion from an injection port formed in the covering plate member, and the existing pillar and the covering plate member are provided. It is characterized by integrating.

At this time, the covering plate member is made of a steel plate, and a flange portion formed by bending the steel plate is
It is preferable that the anchor bar made of deformed rebar is welded and fixed at a predetermined row pitch in the column height direction of the existing column.

In any one of the above cases, it is preferable that the anchoring bar is set such that the fixing position is displaced by 1/2 of the row pitch between the left and right flange positions of the covering plate member.

[0010]

According to the present invention, a plurality of flanges on both sides of a covering plate member bent in a substantially U-shape when viewed in plan are bent at a predetermined bending angle and are provided in the column height direction of existing columns. The existing pillar is sandwiched by the tip of the anchor bar, the covering thickness between the covering plate member and the existing pillar is maintained to cover the existing pillar, and the pillar is assembled around the existing pillar. The coating plate member is constrained by a form restraint holding member, and the coating plate member is deformed when a filler is injected into the covering portion from an injection port formed in the coating plate member,
By integrating the existing column and the covering plate member so as to prevent displacement, it is possible to eliminate work steps such as on-site welding, and to perform a quick and inexpensive reinforcement work.

At this time, the covering plate member is made of a steel plate, and a flange portion formed by bending the steel plate is
Anchor bar consisting of deformed rebar is welded and fixed by opening a predetermined row pitch in the column height direction of the existing column, and it becomes a work using a popular inexpensive structural material, manufacturing in a factory, Processing can also be performed easily and quickly.

In any of the above cases, the anchor bar has the same shape of the covering plate member by shifting the fixing position between the left and right flange positions of the covering plate member by ½ of the row pitch. Can be produced in advance, and can be handled as a pair of covering plate members by reversing the vertical direction of this member on site. At this time, the pitch of the anchor bars at the butt joints of the assembled covering plate members is 1/2 of the row pitch.
Becomes

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the seismic retrofitting structure for existing columns according to the present invention will be described below with reference to the accompanying drawings. FIG. 1 shows a part of an existing pillar 10 that has been damaged by the earthquake. In this existing column 10, shear cracks 11 are formed in an X-shape at an approximately intermediate height position of the column due to the acting horizontal force. Therefore, in order to continue using the building in the future, it will be necessary to reinforce the columns against earthquakes. An example in which the seismic strengthening structure according to the present invention is applied to the existing pillar 10 will be described below. The covering steel plates 20 used for the seismic reinforcement structure have a height from the floor surface to the underside of the beam similarly to the steel plate shown in FIG. 9, and are a pair of covering steel plates having a substantially U-shape in plan view. The columns 20 are arranged so as to face each other and cover the entire height of the existing column 10 from the side of the column.
Note that, for simplification of the drawings, the illustration of the main reinforcing bars and the like in the existing columns 10 which are reinforced concrete columns is omitted in each figure.

Structure of the coating steel sheet: FIG.
(C) will be described with reference to FIG. In a portion corresponding to the flange 20a of the coating steel plate 20 bent in a U shape,
As shown in FIGS. 2A and 2B, short anchor bars 22 are welded along the height direction of the column at predetermined intervals over the entire height. In addition, in each drawing of FIG. 2, for simplification of the drawing, reference numeral 22 is attached only to a part of the anchor bars. In the present embodiment, the anchor bar 22 uses deformed bar that is cut into a predetermined length and bent. The shape of the anchor bar 22 is bent in an intermediate position and has a substantially “F” shape in a plan view, and an inward bending angle is set so that the tip of the anchor bar 22 is in contact with the existing column 10 (FIG. 2). (C), see FIG. Thereby, the steel plate 2 for coating
When attaching the end of 0 to the existing pillar 10, the steel plate 2 for coating
With 0, a predetermined covering thickness and position are retained with respect to the existing pillar 10. Further, the overall length L of the portion extended from the portion welded to the coating steel plate 20 is set to about 35 to 40 times the deformed bar diameter (L = 35 to 40D where the bar diameter is D). At this time, the bent portion of the anchor bar 22 is located at a position extending from the end portion 20a of the steel plate by a length e, and is bent inward from that portion. In this way, since the linear extension 22a for the length e is provided along the coating steel plate 20,
Another steel plate 20 (2 in FIG. 3) to which this part is joined
This is indicated by a chain line. ) Is the positioning portion of the end portion 20a. As a result, the end faces of the covering steel plates 20 attached to face each other with the existing pillar 10 interposed therebetween can be butt-joined without displacement.

Further, as shown in FIG. 2B, the anchor bar 22 is welded to each flange 20a at a pitch p arranged in the column height direction. Further, the left and right flanges 20a are arranged so as to be offset from each other by 1/2 of the row pitch p. Therefore, in the vicinity of the joint of the flange 20a, the anchor bars 22 extending from both sides are alternately arranged at the p / 2 pitch (see the notch in FIG. 4). Further, since the anchor bar 22 is arranged in this way, it is possible to use the covering steel plate 20 having the same shape with the vertical direction reversed. Therefore, the coating steel plates 20 to be supplied in the same layer having the same column cross-sectional dimension and column height can be dealt with by factory-manufacturing one type of standard.

When the installation of the coating steel plate 20 is completed, mortar filling is performed as in the conventional reinforcing structure. The covering thickness between the existing column 10 and the coating steel plate 20 corresponding to the void filled with the mortar is secured by the anchor bar 22 in the X direction as shown in FIGS. 1 and 2C.
Further, the Y direction is secured by the spacer 25 fixed to the inner surface of the web of the coating steel plate 20. Since the spacer 25 is embedded in the mortar to be filled later,
As long as there is no problem in compatibility with the mortar, known materials and shapes such as mortar, synthetic resin, various metal materials and the like can be used.

A circular opening 26 having a small diameter is provided at the upper end of the coating steel plate 20. The circular opening 26 has already been drilled at a predetermined position when the coating steel plate 20 was manufactured. Then, as shown in FIG. 1, since a pair of coating steel plates 20 having the same shape are used by reversing the upper and lower sides of the same, the circular opening 26 is formed in the lower part of the column in one coating steel plate 20. Located mortar inlet 2
6A, the other covering steel plate 20 functions as an air vent 26B located at the top of the pillar.

When mortar is injected into the void through the mortar injection port 26A at a predetermined injection pressure, the mortar fills the space between the existing column 10 and the coating steel plate 20 from below. Then, when the space is reliably filled to the position below the beam, a part of the mortar overflows from the air vent port 26B in the upper part of the column. In this way, the air vent port 26B also serves as a port for confirming whether or not the mortar is surely filled in the gap.

Next, a formwork restraining / holding member when the coating steel plate 20 is used as a formwork during mortar injection will be described with reference to FIGS. 4 and 5. FIG. 4 shows a state in which a restraint belt 30, which is a form restraint holding member, is bound around the coating steel plate 20 attached to the existing pillar 10 to be reinforced. The restraint belt 30 has a main body made of a synthetic fiber plain weave belt having a predetermined width, a buckle 31 is attached to the belt end, and the other end of the belt is inserted into the buckle 31 to tighten the buckle 31 to be an object. Steel plate for coating 20
It is possible to prevent the deformation and the opening of the butt joint. Although FIG. 4 shows a state in which the coating steel plate 20 is restrained by the four restraint belts 30, the restraint belt 30 used can have any belt width and thickness.
The number of belts and the arrangement position can also be appropriately set within a range in which the coating steel plate 20 is not deformed or the butt joint is opened with respect to the mortar internal pressure expected during mortar filling. As the material of the belt used, high tensile strength materials such as carbon fiber and aramid fiber may be used in addition to synthetic fibers.

FIG. 5 is a plan view showing a modified example in which a thick edge material is used as the formwork restraint holding member instead of the restraint belt 30. As this thick end material, various ready-made clamp members 40 that suppress the deformation of the formwork dam of the concrete pillar can be used. As shown in the same figure, the lateral end thick material is assembled in a cross beam shape so as to surround the coating steel plate 20, and the intersections of the clamp members 40 are fixed by a cotter pin or the like to form a □ -shaped frame. . This can prevent deformation of the coating steel plate 20 and opening of the butt joint when the mortar is filled. As the clamp member, various materials such as lightweight shaped steel and fiber-reinforced molded products that can exhibit a predetermined tensile strength can be used.

FIG. 6 is a partial perspective view showing a modified example in which flat steel (steel band) is used as the anchor bar instead of the deformed bar. The anchor bar 32 made of flat steel is bent into a predetermined shape as shown in FIG. 7, and is welded and fixed to the inner surface of the flange 20a of the coating steel plate 20. Further, circular holes are formed at a predetermined interval on the surface of the flat steel, and when the flat steel portion is filled in the mortar, sufficient adhesion with the mortar can be obtained. The bending shape of the tip portion of the anchor bar 32 is set to a width B0 which is slightly narrower than the width B of the existing column 10 as shown in FIGS.
When attaching the coating steel plate 20 to the existing column 10 in the direction of the arrow, the existing column 10 can be sandwiched by the tip portion of the anchor bar 32. At this time, the tip of the anchor bar 32 is pushed outward slightly, so that the leaf spring effect is exerted and the steel plate 20 for coating can be reliably positioned on the existing column 10. In the above description, the existing columns were covered with the covering steel plate in any of the examples, but an appropriate metal plate such as an aluminum plate can be used instead of the steel plate. At this time, special welding is required to attach the anchor bar depending on the type of base material. It is also possible to use a resin molding plate reinforced with glass fiber as a cover plate. In this case, it is necessary to apply a refractory coating material as a finish on the outer surface. In the case of a glass fiber reinforced resin molded plate, a rod molded of the same material as the anchor bar can be bonded to the flange portion.

The mortar to be filled is preferably a non-shrink mortar to which a swelling additive such as a gypsum type, a calcium sulphoaluminate type and a high sulfate type is added. As a filling method, conventional mortar filling technology and equipment can be applied as they are. Further, since the butt joint portion of the coating steel plate 20 is not welded, the mortar does not leak from the joint portion,
It is preferable to apply a sealing material in the same manner as the space between the floor and the lower part of the beam. As the sealing material, tape-shaped butyl rubber, water-swelling rubber and PE (polyethylene) which can be attached to the joint from the outside are preferable. It is also preferable that a groove having a predetermined size is formed and a liquid sealing material is injected into the groove to cure the groove so as to exhibit water stopping property.

In the above description, the seismic reinforcement structure of the existing columns has been described by taking the existing independent columns of the building damaged by the earthquake as an example, but the existing columns of the short column structure having the hanging wall and the sleeve wall are also described. The same effect can be obtained by using the coating steel plate 20 having the same shape and size. In addition, seismic diagnosis may be conducted in buildings that have not been damaged by the earthquake. When it is determined from the diagnostic results that the shear strength of the existing column is insufficient, it is also preferable to use the above-mentioned seismic reinforcement structure column in advance.

[0024]

As is apparent from the above description, according to the present invention, the pillar portion of an existing building or an existing building damaged by an earthquake or the like can be quickly and inexpensively reinforced, and sufficient seismic resistance can be obtained after the reinforcement. The effect of being able to exert the effect is exhibited.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view showing an embodiment of an earthquake-proof reinforcing structure for existing columns according to the present invention.

FIG. 2 is a front view, a side view, and a plan view showing an example of a steel plate for coating used for the seismic reinforcement structure of the existing column shown in FIG.

FIG. 3 is a partially enlarged view showing an example of an anchor bar welded to a coating steel plate.

FIG. 4 is a perspective view showing a state where the assembled covering steel plate is restrained by a restraint belt.

FIG. 5 is a plan view showing another modified example of the constraint holding member for the coating steel plate.

FIG. 6 is a partial perspective view showing a modified example of the anchor bar.

7 is a state explanatory view showing a state in which a coating steel plate is attached to an existing column using the anchor bar shown in FIG. 6 as a guide.

FIG. 8 is a sectional view showing an example of a conventional seismic retrofit structure for existing columns.

FIG. 9 is a work explanatory diagram showing a work sequence of a conventional seismic reinforcement structure for existing columns.

[Explanation of symbols]

 10 Existing Column 20 Steel Plate for Coating 22,32 Anchor Bar 25 Spacer 26 Circular Opening 26A Mortar Injection Port 26B Air Venting Port 30 Restraint Belt

Claims (3)

[Claims] 1. A plurality of anchor bars bent at a predetermined bending angle are provided in both side flange portions of a plate material bent in a substantially U-shape in a plan view in a column height direction of an existing column, The anchor includes: a covering plate member that covers the existing pillar; and a formwork constraint holding member that is provided around the covering plate member that covers the existing pillar and that prevents deformation and displacement of the covering plate member. The existing pillar is sandwiched by the tip of the bar, the covering thickness between the covering plate member and the existing pillar is held to cover the existing pillar, and the formwork constraint holding member is provided. In this state, a filling material is injected into the covering portion from an injection port formed in the covering plate member, and the existing pillar and the covering plate member are integrated with each other, and seismic reinforcement of the existing pillar is performed. Construction. 2. The covering plate member is made of a steel plate, and anchor bars made of deformed reinforcing bars are provided in a predetermined row in a column height direction of the existing columns on a flange portion formed by bending the steel plate. The seismic reinforcement structure for an existing column according to claim 1, wherein the seismic reinforcement structure is welded and fixed at a pitch. 3. The anchor bar has a fixing position of 1 / the row pitch between the left and right flange positions of the covering plate member.
The seismic reinforcement structure for an existing column according to claim 1 or 2, wherein the seismic reinforcement structure is set to be shifted by 2.