JP3406820B2 - Seismic retrofitting method for existing columns and seismic retrofitting structure for existing columns - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a seismic retrofitting method and a seismic retrofitting structure for an existing reinforced concrete column from the outer periphery.

[0002]

2. Description of the Related Art Many structures have collapsed or damaged due to the Great Hanshin Earthquake that struck the Hanshin area on January 17, 1995, and the collapse of reinforced concrete columns such as elevated roads was unprecedented. It was Therefore, reinforcement of such reinforced concrete columns is still being actively performed in preparation for a future great earthquake.

As one of the methods for seismic reinforcement of such a column, there is a steel plate winding construction method shown in FIGS. 7 (A) and 7 (B). In this method, the entire circumference of the existing pillar 51 is replaced by the horizontal beam 52 at the upper end.
It is surrounded by a pair of steel plates 54 having a U-shaped cross section, leaving a lower gap 53, and the vertical joints with backing plates of both steel plates are welded (55), and the outer circumference of the steel plates 54 is longitudinally spaced by a predetermined distance. This is a method in which the space between the steel plate 54 and the existing column 51 is filled with the mortar 57 after being reinforced by the horizontally welded presser strip plate 56.
However, since this method requires on-site welding (55), quality control is difficult, and a crane or hoisting equipment is required when the steel plate 54 is installed in a small space. Since it is necessary to make the steel plate thicker than required for strength or to expose the air to the atmosphere, rust-preventive coating is required, which is uneconomical as compared with reinforcement by hoop reinforcement.

[0004]

[Problems to be solved by the invention]
As one of the seismic reinforcement methods, there is an RC (reinforced concrete) winding construction method shown in FIGS. 7 (C) and (D). In this construction method, reinforcing bars 58 are hung vertically on the outer four corners of the existing columns 51, and these reinforcing bars 58 have, for example, a steel bar for reinforced concrete with a diameter of 16 mm.
(SD35) is processed into a rectangular shape and a hoop line 59 is externally fitted to weld the hoop seam (59a), and the hoop line 59 is welded or bound to the spline line 58 in the longitudinal direction at intervals of, for example, 10 cm. After bundling with the
2 is a method of placing a mortar 57 in a temporary frame (not shown) surrounded by a gap 53 below. However, in this RC winding construction method, since there is a foundation at the lower end of the existing column 51 and a horizontal beam 52 at the upper end, the hoop reinforcements 59 are externally fitted one by one and the seams are welded, and then sequentially fixed at predetermined intervals. However, there is a problem in terms of quality control and workability by on-site welding.

Therefore, the object of the present invention is to save time and labor by using one hoop muscle processed into a spiral bundle instead of the conventional hoop muscle which is formed into a separate loop. The purpose of the present invention is to provide an earthquake- proof reinforcement method and structure for existing columns that can reinforce existing columns with few defects.

[0006]

Means for Solving the Problems] To achieve the above object, seismic reinforcement method for existing column of claim 1, the helical hoop a bundle formed in a shape along the outer shape of the existing columns, flux
It is characterized in that it is arranged around the existing column at a constant distance from the outer peripheral surface of the existing column by rotating in the unwinding direction, and the existing column and the spiral hoop muscle are covered with mortar. In this specification, mortar means
In addition to mortar itself, it is used in a broad sense that includes concrete.

[0007] In the seismic reinforcement method of the existing pillars of claim 1, already
By rotating the spiral hoop muscle that is formed into a shape that conforms to the outer peripheral shape of the installation column and is bundled ,
Note: Since it is wound around the existing column and arranged at regular intervals, it is not necessary to externally fit one ring-shaped hoop muscle to the column and weld the seam as in the past, so there are few defects and efficient operation. By constructing various hoop reinforcements, existing columns can be efficiently and strongly reinforced against earthquakes.

According to the seismic retrofitting method for an existing column of claim 2, the spiral hoop muscles formed into a shape along the outer peripheral shape of the existing column and bundled are rotated in a direction in which the bundle is unraveled. A spiral hoop muscle is arranged around the existing column at a constant interval from the outer peripheral surface of the existing column, and while filling the gap between the existing column and the spiral hoop muscle while spraying mortar, the spiral hoop muscle is mortar. It is characterized by coating.

According to the seismic retrofitting method of claim 2 , outside the existing pillar
The helical hoop a bundle formed in a shape along the circumferential shape, beam
By rotating it in the unwinding direction, it is wound around the existing pillars and arranged at regular intervals, so that one ring-shaped hoop muscle is externally fitted to the pillars one by one and the seams are welded as in the conventional case. Since it is not necessary, the existing columns can be efficiently and strongly reinforced by earthquake by constructing efficient hoop reinforcements with few defects. Also, since the gap between existing columns and spiral hoop muscles is filled with mortar and the spiral hoop muscles are covered by spraying, the spiral hoop muscles can be covered without the need for a temporary frame for mortar filling, so construction is more efficient. In addition, the anti-corrosion coating of the spiral hoop can be omitted.

The seismic retrofitting structure of the existing pillar of claim 3 is the existing structure.
The pillar and this existing pillar before being placed on the outer circumference of this existing pillar
And has a shape along the outer peripheral shape, characterized by comprising a helical hoop being disposed at a predetermined interval from the outer peripheral surface of the existing columns, the mortar covering the existing columns and spiral hoop . In the earthquake-proof reinforcement structure according to claim 3, a shape along the outer peripheral shape of the existing pillar is provided around the existing pillar.
Since the spiral hoop muscle that it has before installation is installed,
Unlike the conventional case, it is not necessary to externally fit the ring-shaped hoop muscles to the columns one by one and weld the seams, so that a strong earthquake-proof reinforcement structure with good construction efficiency is obtained.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will be described in detail below with reference to the embodiments shown in the drawings. 1 (A) and 1 (B) are a perspective view and a side view, respectively, showing an embodiment of a method of arranging spiral hoop muscles, which is a main part of a method for seismic strengthening an existing column. Spiral hoop muscle 1
Is a high-strength steel wire processed into a spiral bundle by forming a rectangular loop along the outer circumference of the existing column 51. To wind the spiral hoop muscle 1 around the existing column 51, the spiral hoop muscle 1 is brought close to the outer surface of the existing column 51 as shown in the drawing.
In addition, the opening surface (loop surface) of the spiral hoop muscle 1 is laterally oriented so as to face the outer surface, that is, arranged in the direction along the vertical plane, and the tip of the winding start, which is bent at a right angle (not shown), Inserted and fixed in a hole (not shown) formed perpendicularly to the pillar surface at the lower end of the existing pillar 51, while holding the bundle of spiral hoop muscles 1 such that the opening surface thereof is along the vertical direction,
While rotating in the direction in which the bundle shown by arrow X in FIG. 1 (B) is unwound, the circumference of the existing column 51 is circulated in the direction indicated by arrow Y,
It is carried out by winding around the existing column 51 one loop at a time. It should be noted that what is horizontally overlapped with the outer periphery of the lower end of the existing column 51 in FIG. 1 is the already wound spiral hoop streak, and the bundle vertically held facing the outer surface of the existing column 51 will be wound next. It is a spiral hoop muscle.

FIG. 2 is a schematic diagram for examining the winding pitch of the spiral hoop muscle of the present invention and the stress generated at that time in comparison with the conventional example described in FIGS. 7 (C) and (D). is there.
First, assuming that the allowable load carried by the total cross section of the spiral hoop muscle per column unit length is equal to the allowable load carried by the similar total cross section of the conventional hoop muscle, the winding pitch of the embodiment is obtained. The hoop muscle of the conventional example has a diameter: d = 16 mm, a pillar 1 m
Number of pieces per piece: n = 10 pieces / m (10 cm pitch), Yield point: σy = 3
Because it is 8 kgf / mm ^2, per pole 1m allowable load W of the hoop plays ^{is, W = σy × (πd 2} /4) × 2 × n = 15270
It will be 0 kg. On the other hand, the spiral hoop muscle (PC steel bar SBPD130 / 145) of this embodiment has n '(pieces / m) per 1 m of the column, and d' = 7.4 mm, σy '= 134 kgf / mm ² Load W '
Is W '= σy'πd' ² n '/ 2 = 11520 n'kg, and W =
If you write W ', you get n' = 152500/11510 = 13.3. Therefore, considering the safety factor, n '= 20, that is, the winding pitch is determined to be 5 cm. Thus, in this embodiment, the pitch made is doubled length of hoop required for winding pillars 1m halved in the conventional example, 0.214 cross-sectional area of the hoop is in the conventional example (= 3.7 ² / 8 ² ) times, so while maintaining the same degree of reinforcement as before, it is possible to reduce the weight of the hoop muscle by about half and reduce the construction weight.

Next, the shear stress caused by twisting during winding will be examined. The torsional rigidity T of a round bar of diameter d (mm) is T = GI = Gπd, where G (kgf / mm ² ) is the transverse elastic modulus of the round bar and θ (rad / mm) is the twist angle per unit length. ⁴ θ
/ 32, which is the maximum shear stress τ (kgf
/ Mm ² ) Substituting into τ = 16T / (πd ³ ), τ =
Gdθ / 2 (1) The twist angle of the spiral hoop muscle 1 is
As shown in FIG. 2, from the lower end 1s fixed to the pillar 51 to the first corner 1a of the uppermost loop already wound is zero, and gradually increases from here to the second corner 1b to reach 45 °, It can be considered that the constant value of 45 ° is maintained up to the third corner 1c, and then gradually increases again to 90 ° at the fourth corner 1d. That is, since the twist angle increases by 90 ° with respect to the half circumference of 1800 mm of the pillar 51 (900 mm □), the twist angle θ per unit length is θ
= (Πrad / 180 °) × (90 ° / 1800mm) = 0.000873 (rad / m
m).

G in the equation (1) is G = E / 2 (ν + 1)
E: Young's modulus, ν: Poisson's ratio
As long as it is steel regardless of SD35 of the conventional example, SWPR1 of the present invention,
It is constant (8100 kgf / mm ² ), and θ in the equation (1) is also the above constant value regardless of the present invention or the conventional example. Therefore, the maximum shear stress τ generated in the hoop muscle due to the twist is proportional to the diameter d of the hoop muscle from the equation (1). On the other hand, the maximum allowable shear stress τa of a material is given by τa = σy / 2√3… (2), where γy is the yield point of the material. Therefore, the maximum allowable shear stress of hoop muscles is It will be proportional to the point σy. Therefore, by substituting the material characteristic values and the like of the conventional example and the present embodiment into the above equations (1) and (2) to obtain the maximum shear stress τ and the maximum allowable shear stress τa, respectively, in the conventional example, τ = Since 56.6 (kgf / mm ² )> τa = 11.0 (kgf / mm ² ), winding is impossible, but in the present invention, τ = 26.2 (kgf
/ Mm ² ) <τa = 38.7 (kgf / mm ² ), which enables winding within elastic deformation. This is because this embodiment uses SWPR1 having a much higher strength than the SD35 of the conventional example, so that the maximum allowable shear stress τa can be increased,
This is because the hoop muscle can be made small in diameter and the maximum shear stress τ generated by torsion can be made small in inverse proportion to the diameter.

A seismic retrofitting method for an existing column including the above-mentioned spiral hoop bar winding will be described with reference to FIG. First, the concrete of the existing pillars 51 is subjected to a surface treatment so as to be compatible with mortar to be sprayed later, and subsequently, brace 58 for binding is vertically provided at the four outer corners of the pillars 51. Next, pillar 5
Make an anchor hole (not shown) at the lower end of 1 perpendicular to the pillar surface,
After inserting the tip of the spiral hoop muscle 1 bent at a right angle into this anchor hole, hold the loop surface of the bundle of spiral hoop muscle 1 facing the column outer surface, that is, along the vertical direction, and keep it in this state. While rotating the bundle in the direction of arrow X shown in FIG. 1B, the bundle is wound around the column in the direction of arrow Y and wound around the column 51 one loop at a time. After the winding of one bundle is completed, the upper end of the spiral loop streak 1 which is wound around the lower end of the pillar 51 and overlapped with it is lifted above the pillar 51 as shown in FIG. Then, in this state, the four corners of the spiral loop muscle 1 are bound or welded to the supplementary ribs 58 with binding wires to be fixed. Next, the spiral loop muscle 1
After the grout is injected and fixed in the anchor hole into which the tip of the is inserted, the gap between the existing pillar 51 and the spiral loop muscle 1 is filled while spraying mortar and the spiral loop muscle 1
Is covered with mortar to form a mortar layer 57 having a thickness of 40 mm,
The seismic retrofitting of the existing columns 51 is completed.

As described above, the winding of the spiral hoop muscle, which is the main part of the method for reinforcing the seismic resistance of the existing pillar of the present embodiment, is performed in the vertical direction with the loop surface of the spiral hoop muscle 1 facing the outer surface of the existing pillar 51. While holding along, while rotating in the unwinding direction (arrow X in FIG. 1 (B)) around the existing pillar (arrow Y in FIG. 1 (B)) and winding one loop at a time, Rather than opening the corners of the rectangular hoop muscle in the rectangular plane by 90 ° as in the conventional case, the helical hoop muscle can be twisted by 90 ° per semi-perimeter of the column, so it is within the elastic deformation range. In addition to being able to wind around, the vertical holding of the bundle of spiral hoop muscles allows construction even if the space around the column is narrow. Furthermore, in the present embodiment, it is not necessary to externally fit the ring-shaped hoop muscles to the pillars one by one and weld the seams, so that it is possible to efficiently perform seismic retrofitting of existing pillars with few defects. it can.

Further, in the above-mentioned embodiment, since the high strength steel having a yield point of 134 kgf / mm ² is used as the material of the spiral hoop reinforcement 1, the required hoop reinforcement is maintained while maintaining the same reinforcing strength as the conventional one. The weight can be halved, the construction can be made lighter, and the allowable shear stress due to the increase in the yield point and the maximum torsional shear stress that accompanies the winding that is proportional to the diameter reduction of the hoop muscles can be reduced. It is possible to further ensure the winding while surely guaranteeing the winding.

In the above embodiment, the loop shape of the spiral hoop muscle is square, but it is needless to say that this shape can be circular, rectangular or the like according to the sectional shape of the existing column. Further, the material of the spiral hoop muscle is not limited to SWPR1 of the above-described embodiment, and any material may be used as long as the maximum torsional shear stress due to winding is within the elastic range. Further, in the above-described embodiment, since the mortar layer 57 is constructed by spraying after winding the spiral hoop muscles 1, the spiral hoop muscles can be covered without the need for a temporary frame for mortar filling. The efficiency can be further improved, and the anticorrosion coating of the spiral hoop can be omitted. Alternatively, a temporary frame may be assembled around the spiral hoop muscle 1 and mortar may be injected into the temporary frame for construction.

FIG. 4, FIG. 5, and FIG. 6 are a plan view, a side view, and a front view, respectively, showing an apparatus for automatically winding spiral hoop muscles, which is the main part of the method for seismic retrofitting existing columns according to the present invention. It is a figure. This device is a spiral hoop streak 1 which is formed by forming a rectangular loop along the outer circumference of an existing column 51 into a spiral shape and bundling.
With the loop surface 1f facing the outer surface of the existing column 51, that is, the frame member 11 that is supported by the outer circumference 11a along the vertical direction, and the base end of the central axis 11b that is the horizontal axis of the frame member 11 is rotated. Freely (see arrow L in FIG. 6) and a horizontally supporting column 12, and a vertical axis 12a that is the vertical axis of this column 12.
It is equipped with a carriage 13 that is swingably mounted (see arrow M in FIG. 4) via and that turns around an existing column 51 (see arrow N in FIG. 4).

On the ground around the existing pillars 51, there is laid a track 14 which is formed by processing a section steel having a U-shaped cross section into a circular shape, and rails 15 and 15 are formed on the section steel forming the inner and outer circles. The rack gear 16 is fixed and is provided on the entire inner circumference of the outer circle, and the guide rail 17 is provided in the middle of the inner and outer circles. On the other hand, the carriage 13 includes four wheels 18 rolling on the rails 15, positioning rollers 19 that prevent the wheels 18 from separating from the rails 15 by sandwiching the guide rails 17 from both sides. A pinion gear 21 that meshes and is driven by the motor 20 to rotate the carriage 13 and a generator 22 that supplies electric power to the motor 20 are provided.

Further, the frame member 11 has a central shaft 11b.
And horizontal members 11a arranged at the four corners of the horizontal members 11a are connected to each other by bracing members 23 to form a rectangular parallelepiped. At the tip of each horizontal member 11a, a retaining pin for turning the spiral hoop muscle 1 to prevent the spiral hoop muscle 1 from slipping off 24, and the base end of the central shaft 11b is located at the upper end of a pillar 26 projecting from the far end of the plate-like portion 25 of the pillar 12 that is swingably mounted on the carriage 13 via the vertical shaft 12a. It is pivotally supported via a bearing 27.

The winding of the spiral hoop muscle around the existing column by the above device is as follows. First, the retaining pins 24 at the four corners of the front surface of the frame member 11 are aligned with the horizontal members 11a, and the bundle of spiral hoop muscles 1 is externally fitted to the frame member 11 from the front surface, and the tips of the spiral hoop muscles 1 are pulled out. Existing pillar 5
It is locked in an anchor hole (not shown) at the lower end of 1, and the retaining pin 24 is pivoted at a right angle and locked to prevent the bundle from falling out. As a result, the spiral hoop muscle 1 is vertically supported with its loop surface 1f facing the outer surface of the existing column 51. Next, the generator 22 is started to drive the motor 20 with electric power, and the trolley 13 is moved through the pinion gear 21 and the rack gear 16 onto the rail 15 around the existing pillar 51 by an arrow N (FIG. 4).
Turn in the direction of. Then, the pillar 12 on the carriage 13
While swinging in the direction of arrow M (FIG. 4) in the horizontal plane, the frame member 11 pivotally supported by the upper end of the support 26 via the bearing 27 rotates in the direction of arrow L (FIG. 6), and spirals. The bundle of loop muscles 1 is unwound one by one and wound around the existing column 51 as shown in the drawing.

As described above with reference to FIGS. 1 and 2, the spiral hoop muscle 1 when wound is twisted and deformed within the elastic range by 90 ° per semi-peripheral length of the column. Since it is not necessary to fit each of the streaks onto the column and weld the seam, it is possible to reinforce the existing column efficiently and without defects. If the spiral hoop muscle 1 is made of high-strength steel, the required weight of the hoop muscle can be halved while maintaining the reinforcing strength as described above, which reduces the construction weight and ensures the winding within the elastic range and the winding. Needless to say, it can be further simplified.

In the above apparatus, the central axis 11b of the frame member 11
The base end of is supported horizontally by a column 12, and this column 12 is swingably mounted on a carriage 13 via a vertical shaft 12a, so that the spiral hoop muscles 1 are bundled in a rectangular loop. However, there is an advantage that the swinging of the column portion 12 facilitates winding around the existing column 51. Further, since the retaining pins 24 are provided at the four corners of the front surface of the frame member 11, there is an advantage that the spiral hoop muscle 1 can be reliably prevented from falling out of the frame member 11.

In the above apparatus, the frame member 11 is a rectangular parallelepiped, but it is needless to say that this shape can be a cylindrical shape or the like according to the loop shape of the spiral hoop muscle. If the loop shape of the spiral hoop muscle is, for example, a circle, the column 12
Even if is attached to the carriage 13 so as not to swing, there is no problem in winding.

[0026]

As is apparent from the above description, claim 1
The seismic retrofitting method for existing columns is the direction of unwinding the spiral hoop streak that is formed into a shape along the outer peripheral shape of the existing column and bundled.
The existing column and the spiral hoop muscles are covered with mortar by arranging them so that they are spaced apart from the outer peripheral surface of this existing column by a mortar. Since it is not necessary to fit and weld the seam, the existing columns can be efficiently and strongly reinforced by seismic reinforcement by efficient hoop reinforcement construction with few defects.

According to a second aspect of the seismic reinforcement method for an existing column, a spiral hoop streak formed and bundled along the outer peripheral shape of the existing column is rotated in a direction in which the bundle is unwound, whereby the outer periphery of the existing column is reinforced. Since it is arranged at a constant distance from the surface and the mortar is filled into the gap between the existing column and the spiral hoop muscle while the spiral hoop muscle is covered with the mortar, the existing column can be efficiently treated as in claim 1. In addition to being able to satisfactorily and strongly strengthen the earthquake resistance, the spiral hoop muscles can be covered without the need for a temporary frame for filling mortar, which makes the construction even more efficient,
The anti-corrosion coating of the spiral hoop can be omitted.

The seismic reinforcement structure of the existing column of claim 3 is the existing structure.
The pillar and this existing pillar before being placed on the outer circumference of this existing pillar
While having a shape along the outer peripheral shape, since it is provided with a spiral hoop muscle that is arranged at a constant distance from the outer peripheral surface of the existing column, and a mortar that covers the existing column and the spiral hoop muscle, The hoop-shaped loop like a column
Since it is not necessary to weld the seams by fitting them one by one, a strong seismic strengthening structure with good construction efficiency can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view and a side view showing an embodiment of a method of arranging spiral hoop muscles, which is a main part of an earthquake-proof reinforcing method for existing columns according to the present invention.

FIG. 2 is a schematic diagram for examining a winding pitch of a spiral hoop muscle and a stress generated at that time.

3A and 3B are a plan view, a side view, and an enlarged plan view showing a seismic retrofitting method of an existing column including winding of a spiral hoop muscle of the present invention.

FIG. 4 is a plan view showing an apparatus for automatically winding spiral hoop muscles, which is a main part of the method for earthquake-proofing reinforcement of an existing column of the present invention.

5 is a view taken along the line VV of FIG.

6 is a view taken along the line VI-VI in FIG.

7A and 7B are a plan view and a side view showing a conventional steel plate winding construction method and RC winding construction method, which are conventional seismic reinforcement methods for columns.

[Explanation of symbols]

1 ... spiral hoop muscle, 1f ... loop surface, 11 ... frame member, 1
1a ... horizontal member, 11b ... central axis, 12 ... support portion, 12a ...
Vertical axis, 13 ... Bogie, 14 ... Track, 15 ... Rail, 1
6 ... Rack gear, 18 ... Wheels, 20 ... Motor, 21 ... Pinion gear, 22 ... Generator, 24 ... Locking pin, 27 ...
Bearings, 51 ... Existing columns, 57 ... Sprayed mortar, 58 ...
Braces.

─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Yoshinori Nakano 2-2-2 Matsuzaki-cho, Abeno-ku, Osaka-shi, Osaka Okumura-gumi Co., Ltd. (56) Reference JP-A-6-50006 (JP, A) JP Sho 61-6231 (JP, B1) Japanese Patent Publication 6-56061 (JP, B2) (58) Fields investigated (Int.Cl. ⁷ , DB name) E04G 23/02 E04C 5/01

Claims (3)

(57) [Claims] 1. A spiral hoop muscle formed into a shape along the outer peripheral shape of an existing column and bundled, is rotated in a direction in which the bundle is unwound.
Thus, a method for seismic reinforcement of an existing column, characterized in that the existing column and the spiral hoop muscle are covered with a mortar by arranging the existing column around the outer peripheral surface of the existing column at a constant interval. 2. A spiral hoop muscle formed into a shape along the outer peripheral shape of an existing column and bundled, is rotated in a direction in which the bundle is unwound.
As a result, spiral hoop muscles are arranged around the existing pillar at a constant distance from the outer peripheral surface of the existing pillar, and while filling the gap between the existing pillar and the spiral hoop muscle with mortar, the spiral hoop is also filled. A method for seismic retrofitting existing columns, characterized by covering the muscles with mortar. 3. An existing pillar and an outer peripheral shape of the existing pillar before being arranged on the outer circumference of the existing pillar.
And has a shape along the Jo, existing, characterized in that it comprises a helical hoop being disposed at a predetermined interval from the outer peripheral surface of the existing columns, the mortar covering the existing columns and spiral hoop Seismic reinforcement structure for columns.