JPH0443540B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION <<Industrial Application Field>> The present invention relates to a method for seismically reinforcing concrete column members of existing structures.

《Conventional technology》 Some existing structures have been built according to old design standards and guidelines, and therefore have poor earthquake resistance and require seismic reinforcement, or earthquake resistance is required for reasons such as increasing the number of building floors when extending or renovating a structure. There are cases where reinforcement is required.

Typical conventional seismic reinforcement methods include surrounding existing column members with steel plates, or surrounding existing column members with welded wire mesh or reinforcing bar cages, mainly to improve the toughness of the column members, in other words, to prevent cracks and Reinforcement methods have been proposed that are intended to not reduce the loading capacity and energy consumption capacity even after some damage.

[Problems to be solved by the invention] However, this reinforcement method requires welding of the steel plates on site, and unless the welding is performed reliably by a highly skilled person, the desired reinforcement cannot be achieved. is not obtained.

Additionally, mortar, etc., will be injected between the existing column members and the steel plates, welded wire mesh, and reinforcing bar cages in order to transmit stress, but it is not possible to fill the injected mortar densely between these. It was difficult.

Furthermore, in the above-mentioned reinforcement methods, slits are generally provided at the ends of reinforcing members such as steel plates in order to increase only the shear strength of existing column members and maintain the same bending strength as before reinforcement. In the case of members located in this area, the rainwater is not well protected in this area, and as a result, water leakage accidents are more likely to occur.

Furthermore, in the reinforcing method using steel plates, rust prevention measures must be taken on the steel plates, resulting in an increase in maintenance and management costs.

The present invention was made in view of the above-mentioned problems, and its purpose is to effectively reinforce earthquake resistance of existing column members by a simple operation of winding high-strength long fiber strands around existing columns. be.

《Means for solving the problem》 The applicant of the present application previously proposed a method of winding high-strength long fiber strands in a spiral shape on the surface of reinforced concrete columns as an earthquake reinforcement method (Japanese Patent Application No. 1983).
−273357). This method allows the high-strength long fiber strands as a reinforcing material to function as a spiral hoop for reinforced concrete columns, and is expected to have the effect of both increasing the strength and toughness of the columns.

However, when the above-mentioned strands and concrete column members are strongly bonded, once the concrete cracks, stress concentrates only on the strands near the cracks, and the strands break at a relatively early stage of cracking. It was found that the reinforcing effect decreases. Furthermore, when examining the deformation of columns due to earthquakes, it was discovered that the upper and lower ends of the column are relatively more deformed than the middle, and cracks are more likely to occur.

The present invention has been made based on the above knowledge, and according to the seismic reinforcement method for existing columns, high-strength long fiber strands are attached to the outer periphery of column members of existing structures in the height direction. In a method for seismically reinforcing existing columns by winding them in a spiral,
In the upper and lower parts of the column member, the strand and the column member are unbonded or weakly bonded, and in the middle part of the column member, the strand and the column member are bonded. do.

<<Examples>> Preferred embodiments of the present invention will be described below with reference to the accompanying drawings.

In the figure, 1 indicates an existing pillar, and this existing pillar 1
is divided into an upper part 1a, a lower part 1c, and an intermediate part 1b, and a high-strength long fiber strand 2 is wound around the existing column 1 in a continuous spiral shape. The high-strength long fiber strand 2 is made by bundling approximately 6,000 carbon fiber monofilaments and impregnating them with a resin in advance, or by winding them and impregnating them into a strand. However, the fibers used are not limited to carbon fibers, but also glass fibers,
Vinylon fiber or aramid fiber may also be used. The resin is not particularly limited as long as it is used for fiber-reinforced resins, but epoxy resins and the like are generally used. Note that the number of filaments can be determined as appropriate.

In addition, as is well known, the high-strength long fiber strand 2 has several times the strength of the prestressed steel material conventionally used in such fields, and therefore can be used in small amounts. As a result, it achieves the same strength as PC steel with less winding work, and
When winding the strand 2, it can be properly attached to the existing pillar 1 by wrapping it double or triple.Furthermore, it is lightweight and flexible before being impregnated with resin, making it easy to wrap the strand 2 around it. It is easy to work and can be wrapped around an existing pillar 1 having a steep corner such as a prismatic pillar without loosening. In particular, as is well known, the strand 2 is an anisotropic material that has directionality in terms of strength, and although it exhibits its original strength against loads along the longitudinal direction of the fiber, for example, However, it has a property of being weak against loads applied in a direction perpendicular to its longitudinal direction. Therefore, in the present invention, in order to provide seismic reinforcement by winding the strand 2, which has the various advantages described above and exhibits extremely excellent strength in the axial direction of the material, around the existing column 1, the strand 2 In order to take advantage of the characteristics of the high-strength long fiber strands 2 and ensure seismic reinforcement by taking advantage of the characteristics of the high-strength long fiber strands 2, the following measures were taken for the existing columns 1: A combination method such as this is adopted.

In the present invention, of the strand 2 wound spirally as described above, the upper part 1a and the lower part 1c are unbonded or weakly bonded to the existing column 1, and the middle part 16 is bonded. It is.

In other words, in the intermediate portion 1b of the existing column 1, shear cracks diagonal to the column's material axis are predominant, and from the point of view of preventing these cracks from opening and ensuring improved strength, bond bonding is is effective. A proposal constructed in consideration of such diagonal shear cracks was proposed in the above-mentioned patent application filed in 1983, in which the strand was wound in a spiral shape.
It is number 273357. On the other hand, in the upper part 1a and lower part 1c of the existing column 1, bending cracks are dominant, where the load is applied from the horizontal direction, that is, from the diagonal direction for the strand 2 wound spirally. Then, the wrapped strand 2
There is a concern that the material may break. Therefore, in order to prevent such breakage of the strands 2, it was decided to use unbond or weak bonding for the upper and lower parts 1a and 1c of the existing columns 1. In short, the present invention is based on the knowledge of the occurrence of cracks in the deformation of the existing column 1 mentioned above,
By partially unbonding the upper and lower parts 1a and 1c, we can prevent the strand 2 from breaking due to cracks, and by partially bonding the middle part 1b, we can improve the strength. This is what it was designed to achieve.

An example of unbonded bonding is to first attach a polyethylene film as an edge trimming material to the surface of the existing pillar 1, and then wind the above-mentioned strands over the film. In addition, as an example of weak bond connection, without any treatment of the surface of the existing pillar,
The strand is wound directly onto this using a weak adhesive. Another example of weak bonding is to partially bond the strand 2 to the existing column 1 at predetermined intervals in the circumferential direction of the existing column. In this case, if the existing pillar 1 is a square pillar, as shown in FIG. do. This means that if a crack occurs in the pillar, a large crack will not occur in the corner part 3.
This is because a crack with a large width occurs in the middle part of corners adjacent in the circumferential direction.This middle part is unbonded to prevent stress concentration, and the corner part 3 is bonded to obtain a high restraint effect.

In the present invention, the upper and lower middle portions 1b of the existing pillar 1 are bonded to the strand 2. As an example of this bonding, an epoxy primer is applied to the surface of the existing pillar to perform a base treatment, and then the strand 2 is bonded to the surface of the existing pillar. All you have to do is turn it around.

Also, after winding strand 2 around the existing pillar,
Once the resin is impregnated and cured, the monofilaments of the strand are integrally bonded to each other, providing greater tensile strength.

<<Effects>> As described above, in the seismic reinforcement method for an existing column according to the present invention, when winding high-strength long fiber strands in a spiral shape around a column member of an existing structure, the upper and lower parts of the column member are In , the strand and the column member are unbonded or weakly bonded, so even if cracks occur at the ends where the concrete deforms greatly, even force is applied to the strand, and the strand is prevented from stress concentration. As a result, the reinforcing effect of the strands works effectively without breaking. In addition, in the middle part of the column member where the cracks in the concrete are small, unreasonable stress is less likely to be applied to the strand, and since the strand and the column member are bonded in this part,
Even if a small crack occurs, the bonded strands will prevent the crack from progressing, and the overall effect of reinforcing the existing column will be extremely good.

Furthermore, since no steel material is used, there is no need for anti-corrosion treatment, and no welding work is required. Also, since there are no slits on the top and bottom ends of the pillars, there is no need to worry about rain.

[Brief explanation of drawings]

FIG. 1 is an explanatory diagram showing a method for reinforcing an existing column according to the present invention, and FIG. 2 is a plan cross-sectional view showing an example of an existing column reinforced according to the present invention. 1... Existing column, 1a, 1c... Upper and lower parts of existing column, 1b... Middle part of existing column, 2... Strand.

Claims (1)

[Scope of Claims] 1. A method for seismically reinforcing an existing column in which a high-strength long fiber strand is spirally wound around the outer periphery of the column member in the height direction of the column member. An existing column characterized in that the strand and the column member are unbonded or weakly bonded in the upper and lower parts, and the strand and the column member are bonded in the middle part of the column member. seismic reinforcement method. 2. The strand and the column member are bonded at intervals in the circumferential direction of the column member in the upper part and the lower part of the column member to form a weak bond connection. Seismic reinforcement method for existing columns as described in Section 1. 3. When the pillar member is a prismatic pillar, the prismatic pillar and the strand are bonded together only at the corners of the prismatic pillar to form a weak bond connection. Earthquake reinforcement method.