JP2000297540A - Reinforcing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reinforcing method capable of shortening a construction period by improving the workability of the reinforcing method and providing a stable reinforcing effect over a long period. SOLUTION: This method for reinforcing a structure comprises the steps of winding on the structure a reinforcing material formed of a prepreg obtained by impregnating a thermosetting resin in a reinforced sheet in which conductive tape or conductor 3 is woven as a vertical thread 1 in unidirectional sheet having the vertical thread 1 made substantially of aramid fiber or in a reinforced sheet 10 in which the conductive tape or conductor 3 is woven as the vertical thread 2 additionally in the reinforced sheet 10, and flowing a current through the conductive tape or conductor 3 so as to generate heat in order to cure the resin. The thermosetting resin is cured by at least two steps of heating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method of winding around an existing concrete column or the like, hardening an impregnated resin, and strengthening it against earthquake.

[0002]

2. Description of the Related Art Conventionally, a seismic retrofitting method using carbon fiber or aramid fiber is to prepare a unidirectional sheet of such fiber, wind it around an existing structure such as a concrete column requiring reinforcement, and cure at room temperature. A method of applying and impregnating a resin and leaving it to cure at room temperature is employed. The conventional construction method can use epoxy resin, vinyl ester resin, unsaturated polyester resin, phenol resin, etc. as thermosetting resin, but in terms of room temperature curing, it is practically limited to epoxy resin, and the number of days until curing is There is a disadvantage that it takes about 3 days to 1 week depending on the outside temperature, and the construction period is long. In addition, the amount of epoxy resin to be applied in such a coating and impregnating method is usually the same as the weight of the used fiber sheet and is used more than necessary, which is uneconomical. Further, as a method of solving the problem that the construction period is long, a method of heating the thermosetting resin in order to accelerate the curing of the thermosetting resin can be considered. However, if the material is rapidly heated to cure in a short time, a locally overheated portion occurs, and the thermosetting resin thermally decomposes to generate gas, which is taken in the resin as air bubbles, resulting in reduced curing performance. Problem.

[0003]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to reduce the amount of resin used by using a unidirectional sheet prepreg using aramid fiber, and to further reduce the amount of heat-curable resin by heat generated by energization for a short time. In addition to improving the conventional workability and shortening the construction period, thermal decomposition of the thermosetting resin occurs due to local overheating and the reinforcing effect is maintained for a long time without firing phenomenon caused by this An object of the present invention is to provide a method of reinforcing a structure that can be performed.

[0004]

Under such circumstances, the present inventors have conducted intensive studies and have found that a unidirectional sheet whose warp is substantially made of aramid fiber has a conductive tape or a conductive wire as a warp or a conductive tape or a conductive wire. After attaching a prepreg of a unidirectional sheet in which a tape or a conductive wire is woven as a warp and a weft to a structure, the conductive tape or the conductive wire is energized, and the thermosetting resin impregnated with heat generated by the energization is shortly applied. If it is cured, the work period can be shortened, the amount of epoxy resin used can be reduced, and the thermosetting resin does not thermally decompose due to local overheating, and the reinforcing effect can be maintained for a long period of time. And completed the present invention.

That is, according to the present invention, a reinforcing sheet in which a conductive tape or a conductive wire is woven as a warp in a unidirectional sheet whose warp is substantially made of aramid fiber, or a conductive tape or a conductive wire is further woven as a weft in the reinforcing sheet. In a method of winding a reinforcing material made of a prepreg impregnated with a thermosetting resin on a reinforcing sheet around a structure, applying an electric current to the conductive tape or the conductive wire, generating heat, curing the resin, and reinforcing the structure. The present invention also provides a reinforcing method characterized in that the thermosetting resin is cured by at least two stages of heating.

[0006]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, a reinforcing sheet to be prepreg will be described with reference to FIGS. FIG.
FIG. 2 is a schematic view of a reinforcing sheet according to the first embodiment, and FIG.
FIG. 2 is a schematic view showing a conductive tape or a conductive wire portion of FIG. 1. In the reinforcing sheet according to the first embodiment, the unidirectional sheet substantially made of aramid fiber refers to a woven fabric using aramid fiber as at least a main fiber of a warp,
The woven fabric is further woven with a conductive tape or a conductive wire as a warp. The outline of the appearance is, as shown in FIGS. 1 and 2, a unidirectional woven fabric sheet 10 using aramid fibers for the warp 1, and the warp 1 and the conductive tape or the conductive wire 3 are passed in the left-right direction. Formed. In FIG. 1, the gap between the warp yarns changes depending on the number of the warp yarns to be driven per unit width. The weft 2 is a continuous or discontinuous yarn that is passed through in the up-down direction while knitting the warp yarn 1 and is formed coarsely horizontally. Further, both ends 3a and 3b for connecting the conductive tape or the conductive wire 3 in parallel are connected to an energizing device not shown in the figure.

Aramid fibers used for warp are used to give strength. The aramid fiber is not particularly limited, but has a tensile strength of 15 g / d or more and a Young's modulus of 5 or more.
Aramid fibers of at least 00 g / d (d means denier) are preferred. The number of twists of the aramid fiber is preferably as small as possible, and the number of twists is 5 to 50.
Times / m. If the number of twists increases, the Young's modulus of the sheet decreases, and the effect of shear reinforcement or bending reinforcement, which is the purpose of seismic reinforcement, decreases, which is not preferable. The basis weight of the unidirectional sheet is usually 200 to 100, excluding the weight of the weft.
0 g / m ² . The number of warp yarns per unit width is easily determined from the thickness of the aramid fiber used and the basis weight of the unidirectional sheet.

In the present invention, the conductive tape used as a warp is not particularly limited as long as it is a tape-shaped heating element which generates heat by energization. For example, a composite of a tetrafluoroethylene resin and a conductive carbon And a tape-like material obtained by finely cutting the fluororesin sheet heating element. The width of the tape is preferably in the range of 1 to 10 mm, and the thickness of the tape is preferably in the range of 0.075 to 0.20 mm. If the width of the tape or the thickness of the tape is less than the above range, the resistance value per unit length of the tape becomes large, and the voltage at the time of energization becomes undesirably high. If the width of the tape or the thickness of the tape exceeds the above range, the rigidity of the tape increases and it is difficult to use the tape as a warp. Further, the conductive tape preferably has excellent heat resistance and cold resistance.

In the present invention, the conductor used as the warp is not particularly limited, but is preferably a metal having a good conductor and a large calorific value, and examples thereof include a nickel-chromium alloy and an iron-chromium alloy. The diameter of the conductor is preferably in the range of 0.05 to 1.0 mm. If the diameter of the conductor is too small, the resistance of the conductor will be too large,
The voltage during energization is increased, which is not preferable. If the diameter of the conducting wire is too large, it is difficult to use as a warp, and the rigidity of the reinforcing sheet is increased, the flexibility is impaired, and the sheet is hardly wound around the outer surface of the structure.

The weaving interval (also referred to as a driving interval, hereinafter referred to as "weaving interval") of each conductive tape or conductive wire used as a warp is preferably in the range of 1 to 5 cm. When the weaving interval is within this range, the entire surface of the prepreg-formed unidirectional sheet is uniformly heated by energization, so that the impregnated thermosetting resin such as an epoxy resin can be uniformly cured. If the weaving interval is less than the above range, more conductive wires and the like are required than necessary, which is wasteful and tends to cause problems in manufacturing. Further, even if the temperature exceeds the above range, the thermosetting resin cannot be uniformly heated and cured.

In the present invention, the weft is not particularly limited, and organic fibers such as nylon, polyester, cotton, and aramid fibers are used.

FIG. 3 is a schematic view of a reinforcing sheet according to the second embodiment, and FIG. 4 is a schematic view showing a conductive tape or a conductive wire portion of FIG. The difference between the reinforcing sheet 20 according to the second embodiment and the reinforcing sheet 10 according to the first embodiment is that the reinforcing sheet 20 according to the first embodiment is different from the reinforcing sheet 10 according to the first embodiment.
Furthermore, a conductive tape or conductive wire is woven into the weft so that the warp conductive tape or conductive wire and the weft conductive tape or conductive wire are in contact with each other. That is,
3 and 4, in the unidirectional woven sheet 20,
The warp 1 and the conductive tape or the conductive wire 3 are formed to pass in the left-right direction. The weft 2 and the conductive tape or the conductive wire 4 are passed vertically while knitting the warp 1, and are formed coarsely laterally. The weft 2 is a continuous or discontinuous yarn. At this time, the conductive tape or conductor 3 of the warp and the conductive tape or conductor 4 of the weft are in contact with each other to form a contact portion 5. Also,
Wefts 41, 41 located at both ends of the unidirectional sheet 20
Are connected at both ends to form loops 71a, 71
b, and both connection ends 7a, 7b extending from the loops 71a, 71b are connected to a current-carrying device, not shown.

The weaving interval between the conductive tape or the conductive wire 4 is preferably in the range of 10 to 40 cm. This is usually when a unidirectional sheet is made, then cut to a fixed length and wound around an existing concrete column that needs reinforcement.
It is determined by overlapping and winding both ends about 20 to 40 cm. That is, if the weft conductive tape or the conductive wire 3 is present in the overlapped portion, the entire surface of the prepreg-formed sheet can be uniformly heated, and it is convenient for the connection with the power supply device.

In order to bring the conductive tape or conductor 3 of the warp and the conductive tape or conductor 4 of the weft into contact with each other, an uncoated conductive tape or conductor may be used.
In addition, as the energizing method, the loop circuits 71a, 71
The method is not limited to a method of connecting a power supply to both connection ends 7a and 7b extending from 1b. For example, without forming a loop,
The ends 72a of the wefts 41 at both ends of the one-way sheet,
72b may be directly connected to an energizing device not shown in the figure. As described above, according to the second embodiment, since the conductive tapes or wires 3 and 4 of the warp and the weft are in contact with each other, all the conductive tapes or wires generate heat, and the warp It is not necessary to connect conductive tapes and conductive wires used in the parallel connection, and the workability is remarkably improved.

In the present invention, a method for producing a prepreg from the reinforcing sheet is not particularly limited, and is performed according to a known method. That is, a mixture of a thermosetting resin and a curing agent may be applied to a reinforcing sheet made of a unidirectional sheet and dried. As the thermosetting resin,
Phenol resins, epoxy resins, polyurethane resins, unsaturated polyester resins, vinyl ester resins, polyimide resins, and the like can be mentioned. Of these, epoxy resins and phenol resins are preferred in terms of strength, ease of handling, cost, and the like. The amount of resin impregnated in the reinforcing sheet to obtain the prepreg of the present invention is 5 to 5 weight of the prepreg.
It is 30%, preferably 10 to 25%. If the amount of the impregnated resin is small, the fiber cannot be sufficiently restrained to be cured, and if it is too large, the amount of the resin used is unnecessarily increased, which is uneconomical.

The procedure for reinforcing a structure using a reinforcing material comprising a prepreg of the present invention is as follows. First, a reinforcing material (preprep) is wound around a structure, and a current is applied to the conductive tape or conductive wire. When the resin is heated to cure the resin and reinforce the structure, the resin is cured by at least two stages of heating. The structure is not particularly limited, and is a portion requiring strength such as a civil structure such as a bridge, a tank and a steel tower; a road structure; a river, a harbor or a marine structure; Existing concrete columns or the like that require reinforcement for earthquake countermeasures and the like are suitable. First, a primer is applied to the concrete surface to keep the prepreg of the present invention in close contact with the surface of the concrete column. Next, the prepreg sheet cut into a fixed length is wound. Next, an electric current is applied to the conductive wires extending from both ends of the prepreg, and heat is generated by at least two-stage heating to cure the resin. When winding two or more layers, it is preferable to apply a primer each time. That is, the primer is applied on the cured sheet, and the same operation is repeated to wind the required number of sheets.
However, if the prepreg has tackiness (adhesiveness) and adheres to the concrete surface, the primer is unnecessary. Further, if necessary, a thermosetting resin can be applied to the prepreg before the resin is cured by the heat generated by the conductive wire.

In the present invention, the heating method by energization is 2
It is a method of heating according to the heating conditions of the stages. As at least a two-stage heating method, an operation of keeping the temperature in a certain temperature range artificially for a certain time is repeated two or more times, preferably two times. In the one-step rapid heating method, local heating is apt to occur, and foaming caused by thermal decomposition of the cured thermosetting resin occurs to lower the curing performance. In addition, when the composition is gradually cured by heating, the time until the curing becomes unnecessarily long, which is not preferable because a shortening of the construction period cannot be expected.

FIG. 5 shows an example of a two-stage heat curing method.
This will be described with reference to FIG. FIG. 5 is a heating characteristic diagram showing a heating step for performing two-stage heating, and FIG. 6 is a heating characteristic diagram showing a heating step for performing one-stage heating. In FIG.
The two-stage heating includes a first heating step of maintaining the _first temperature T ₁ for r ₁ hours, and a second temperature T higher than the first heating temperature.
_{With a second} heating step of holding at ₂ for r ₂ hours. T
₁ is preferably in a temperature range of from about 1 / 2-1 / 3 of the final heating and holding temperature T _2. Here, the final heating and holding temperature T _2, as shown in FIG. 6, the heating and holding temperature T ₂
Is applied for about 2 hours from the beginning (in FIG. 6,
resin equivalent) to t ₁ is the temperature at which curing. Such temperature T ₂ is determined beforehand by experiment. r ₁ is preferably set to a time corresponding to about １ ／ to 時間 of the time required for touch drying (corresponding to t _O in FIG. 6). Here, touch dry means a state in which the resin does not reach the finger even when touched with the finger,
The time t _O up to the touch drying also changes depending on the heating temperature. As shown in FIG. 6, the time t _O to the touch drying is the time to the touch drying when a voltage corresponding to the final heating holding temperature T ₂ is applied from the beginning. r ₂ hours is not particularly limited, the final resin to hold the temperature from reaching the heat holding temperature T ₂ of a time until the cure.

The rate of temperature rise from room temperature to the start of the first heating step is preferably 10 to 30 ° C./hour,
Further, the heating rate from the end of the first heating step to the start of the second heating step is preferably 30 to 50 ° C./hour. The temperature measurement location is not particularly limited as long as it is a resin portion impregnated in the unidirectional sheet.

[0020]

Next, the present invention will be described in more detail with reference to examples, but this is merely an example and does not limit the present invention. Example 1 (Preparation of reinforcing sheet) Aramid fiber "Twaron H" was used for the warp.
M "(manufactured by Akzo Nobel Co., Ltd.) using 3000 denier fiber, using 500 denier polyester fiber for the weft, and applying a weight of 415 g / m ² (excluding the weight of the weft) to the unidirectional sheet. A 1 mm nickel-chromium alloy wire was woven at 2 cm intervals using a warp to produce a reinforcing sheet. (Preparation of Prepreg) A mixture of bisphenol-type epoxy resin as a thermosetting resin and methyltetrahydrophthalic anhydride as a curing agent was applied to the reinforcing sheet and dried to obtain a prepreg having a resin component of about 25%.

(Reinforcement method) In order to keep the prepreg in close contact with the surface of the concrete column, an epoxy resin-based primer was applied to the concrete surface, and then a sheet of the prepreg cut into a fixed length was further wound. As shown in FIG. 2, the lead wires from both ends of the prepreg are connected to each other to supply a current, generate heat, and raise the temperature of the resin from normal temperature to 35 ° C. in 30 minutes.
(The first heating step), and thereafter, the resin temperature was raised to 70 ° C. of the final heating and holding temperature in 45 minutes, and then the resin was cured by holding the resin at 70 ° C. for 2 hours (second). Heating step). In the present example, the time t _O until the touch dryness was 60 minutes. According to this two-stage heating step, no foaming phenomenon occurred in the resin due to thermal decomposition of the resin. The amount of resin used was about 2
00 g / m ² (about 150 g / m
m ² , about 50 g / m ^{2 of} primer). The tensile strength of the seismic retrofitting material after curing of the resin is 61 tons /
m, and the elastic modulus was 11.0 ton weight / mm ² .

Example 2 (Preparation of reinforcing sheet) Aramid fiber "Twaron H" was used for the warp.
M "(manufactured by Akzo Nobel Co., Ltd.) using 3000 denier fiber, using 500 denier polyester fiber for the weft, and applying a weight of 415 g / m ² (excluding the weight of the weft) to the unidirectional sheet. A 1 mm nickel-chromium alloy wire was woven at 2 cm intervals as warp yarns, and a 0.1 mm-diameter nickel-chromium alloy wire was woven at 20 cm intervals on the weft to produce a reinforcing sheet. (Preparation of Prepreg) A mixture of bisphenol-type epoxy resin as a thermosetting resin and methyltetrahydrophthalic anhydride as a curing agent was applied to the reinforcing sheet and dried to obtain a prepreg having a resin component of about 22%.

(Reinforcement method) In order to keep the prepreg in close contact with the surface of the concrete column, an epoxy resin-based primer is applied to the concrete surface, and then both ends of the prepreg sheet cut to a fixed length overlap by 20 cm. In this way. Next, the wires coming from both ends of the prepreg are connected as shown in FIG. 4 to generate an electric current, generate heat, and raise the resin temperature from normal temperature to 40 ° C. in 35 minutes. (The first heating step), and then the resin temperature is raised to 90 ° C. of the final heating and holding temperature in 70 minutes.
The resin was cured by holding at 60 ° C. for 60 minutes (second heating step). In the present embodiment, the time t to the touch dryness is t.
_O was for 45 minutes. According to the two-stage heating step, no foaming phenomenon occurred due to the thermal decomposition of the resin in the resin. The amount of resin used was about 180 g / m ² (the amount of resin in the prepreg was about 130 g / m ² , and the amount of primer was about 50 g / m ²⁾
/ M ² ). Further, the tensile strength of the seismic retrofitting material after curing of the resin was 60 t / m, and the elastic modulus was 11.1 t / mm ² .

Comparative Example 1 3000 denier fiber of aramid fiber "Twaron HM" (manufactured by Akzo Nobel) was used for the warp and 500 for the weft.
Using denier polyester fiber, weight per unit 415g
/ M ² unidirectional sheet was woven at intervals of 2 cm using a nickel-chromium alloy conductive wire having a wire diameter of 0.1 mm as a warp. In order to keep the unidirectional sheet in close contact with the surface of the concrete column, an epoxy resin-based primer was applied to the concrete surface, and then the unidirectional sheet cut to a fixed length was further wound. Next, an epoxy resin curable at room temperature is applied from above, and the conductors extending from both ends of the reinforcing sheet are connected as shown in FIG. 2 to cause an electric current to flow and generate heat. Was raised to 70 ° C., and then kept at 70 ° C. for 2 hours to cure the resin. In the present embodiment, the time t to the touch dryness is t.
_O was 60 minutes. In this one-step heating step, foaming occurred in the resin due to thermal decomposition of the resin. The amount of the resin used was about 550 g / m ² , which was about 125% based on the total basis weight of the sheet. Further, the tensile strength of the reinforcing sheet after curing of the resin is 60 tons / m, and the elastic modulus is 10.
It was 3 tons weight / mm ² .

As is clear from the results of Examples 1 and 2 and Comparative Example 1, in each of the examples, no foaming phenomenon was observed inside the resin, and a stable cured resin could be obtained. On the other hand, in the comparative example, since foaming was observed inside the resin, a stable reinforcing effect over a long period of time may not be expected.

[0026]

According to the reinforcing method of the present invention, the applied thermosetting resin can be cured in a short time by the heat generated by energization, and the construction period required for construction can be greatly reduced.
By preventing foaming of the resin during heat curing, stable reinforcement can be realized for a long period of time. In addition, the reinforcement sheet after construction,
Physical properties such as tensile strength and elastic modulus are equivalent to those of the conventional method.

[Brief description of the drawings]

FIG. 1 is a schematic view of a reinforcing sheet according to a first embodiment used in the present invention.

FIG. 2 is a schematic view of a conductive tape or a conductive wire portion of FIG. 1;

FIG. 3 is a schematic view of a reinforcing sheet according to a second embodiment used in the present invention.

FIG. 4 is a schematic view of a conductive tape or a conductive wire portion of FIG. 3;

FIG. 5 is a temperature rise characteristic diagram showing a heating step of the two-stage heating method of the present invention.

FIG. 6 is a temperature rise characteristic diagram showing a heating step of the one-stage heating method.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Warp (aramid fiber) 2 Weft 3 Conductive tape or conductor as a warp 4 Conductive tape or conductor as a weft 4a, 4b, 7a, 7b Conductor part connected to an electricity supply device 5 Contact part 10, 20 Reinforcement sheet (Unidirectional sheet) T ₁ Holding temperature in the first heating step T ₂ Holding temperature in the second heating step (final holding temperature) r ₁ Holding time in the first heating step r ₂ Holding in the second heating step time to optimal dry to the touch at time t ₁ time to cure in the holding of the heating and holding temperature T ₂ for about 2 hours t _O heated holding temperature T ₂

 ──────────────────────────────────────────────────続 き Continued on the front page (72) Inventor Masayuki Shimizu 2-58-8 Higashishinagawa, Shinagawa-ku, Tokyo Inside Sumitomo Bakelite Co., Ltd. (72) Inventor Takao Ota 2-5-2-8 Higashishinagawa, Shinagawa-ku, Tokyo Sumitomo Bakelite Co., Ltd. (72) Inventor Fumio Yamamoto 6-1073 Minamitsukaguchi-cho, Amagasaki City, Hyogo Shinto Paint Co., Ltd. F-term (reference) 2E176 AA01 BB29 4L048 AA04 AA14 AA25 AA52 AA56 AB06 AB28 AC13 BA02 CA01 CA05 DA30 DA41

Claims (4)

[Claims] 1. A reinforcing sheet in which a conductive tape or a conductive wire is woven as a warp in a unidirectional sheet in which a warp is substantially made of aramid fiber, or a reinforcing sheet in which a conductive tape or a conductive wire is further woven as a weft into the reinforcing sheet. In the method of winding a reinforcing material made of a prepreg impregnated with a curable resin around a structure, applying an electric current to the conductive tape or the conductive wire to generate heat, curing the resin and reinforcing the structure, A reinforcing method characterized in that a reactive resin is cured by at least two stages of heating. 2. The reinforcing method according to claim 1, wherein the conductive tape is a tape-shaped material of a sheet heating element made of fluororesin, which is a composite of tetrafluoroethylene resin and conductive carbon. 3. The conductor according to claim 1, wherein the conductor is a nickel-chromium alloy or an iron-chromium alloy.
Reinforcement method described. 4. The reinforcing method according to claim 1, wherein the thermosetting resin is an epoxy resin or a phenol resin.