JP2002131024A - How to fix optical fiber cable - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fix an optical fiber cable for strain measurement to a structure in a state where uniform elastic elongation strain is given in a longitudinal direction and to maintain the state for a long period of time. Provide a secure fixing method. SOLUTION: An optical fiber cable 2 is brought into contact with or close to the surface of a structure 1 to be attached in a state where a tension for generating a desired elastic elongation strain is applied, and an area of at least half of the outer periphery of the cable is The surface of the structure is supported by covering the surface of the structure together with a reaction-curable resin-based composition containing an aggregate to form a coating layer 8 and then curing the resin-based composition. Fix as a surface. The coating layer 8 of the resin-based composition containing the aggregate retains the adhesive force over a long period of time and does not cause creep. Therefore, the optical fiber cable 2 can be uniformly elastically stretched over a long period of time. Can be fixed to the surface of the structure in the state where the surface is provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for fixing an optical fiber cable for strain detection to a structure for measuring the distribution of strain generated in a structure such as a bridge or a building.

[0002]

2. Description of the Related Art As an application technique of an optical fiber, there has been proposed a system for monitoring a distortion generated in a ground, a bridge, a tunnel or the like. In this method, an optical fiber cable composed of only optical fibers or an optical fiber cable in which an optical fiber is housed in a metal sheath material is attached to an object such as a bridge, and one end of the optical fiber cable is inserted into the optical fiber. Is used to measure the distribution of longitudinal strain generated in the optical fiber by measuring the Brillouin scattered light at the point (1), and to detect the fluctuation caused in the object by this. Up to now, when attaching an optical fiber cable to an object, the optical fiber cable must be placed along the object so that it does not slack as much as possible, and fixed at fixed intervals with fixing jigs such as clamps, Has been used in which the adhesive is fixed with an adhesive or an adhesive tape.

[0003]

However, strain detection using an optical fiber requires that a longitudinal strain be generated in the optical fiber in accordance with the strain of the object. When the optical fiber is fixed along the object so that there is no slack, strictly speaking, the optical fiber has a slight slack, and therefore, the elongation strain generated on the object cannot be detected within the range of the slack. Only the above large elongation strain could be detected. Also, no compressive strain of the object could be detected at all.

In order to solve these problems, when attaching an optical fiber cable to an object, an appropriate elastic elastic strain in the longitudinal direction is given to the optical fiber cable in advance.
It is conceivable that the object is fixed to the object in that state, whereby it is possible to detect not only a minute elongation strain generated in the object but also a compression strain.

However, there is a problem that it is extremely difficult to fix an optical fiber cable to an object in a state in which a uniform elastic elongation strain is given in the longitudinal direction and to maintain the state for a long period of time. Was. That is, in order to fix an optical fiber cable to a target object in a state where a desired elastic elongation strain is applied, the object is applied in a state where a desired tension is applied to the optical fiber cable to generate a desired elastic elongation strain. Along the way, while holding that state, a method of pressing at fixed intervals to the object with a holding jig or fixing the entire length to the object with adhesive or adhesive tape When using a jig, there is a delicate pressing method and uneven pressing pressure when fixing the holding jig to the object so that the optical fiber cable is pressed and fixed to the object. A great deal of trouble is required to ensure the uniformity of the initial elastic elongation strain in the optical fiber cable. In addition, in the method of fixing with an adhesive or adhesive tape, the initial elastic elongation strain of the optical fiber cable after fixing is uniform, but the deterioration of the adhesive or adhesive and creep progress over time, and the optical fiber cable And this phenomenon is noticeable especially outdoors.
There is a problem that it is not suitable for long-term use. Furthermore,
In the case of using an optical fiber cable in a form in which the optical fiber is housed in a metal sheath material, the stress relaxation of the metal sheath material and the holding jig progresses with the lapse of time even with the attachment by the holding jig,
Consideration must also be given to the situation where the tightening force of the holding jig can be reduced. In addition, there is an increase in cost for a feature for preventing the fastening interface from slipping due to rainfall and dew condensation moisture, and to prevent the contact portion corrosion due to the dissimilar metal contact corrosion action with the jig.

As a method for securely fixing an optical fiber cable using a metal sheath material to a metal object, a welding method may be used. However, when the welding method is used, the surface of the object is melted or significantly affected by heat, and therefore, application to bridges and buildings, which are important structures, has not been approved. In addition, when the anticorrosive coating has already been applied to the target object, it takes a great deal of trouble to remove and repair the coating film over a wide range that is affected by the heat of welding.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and enables an optical fiber cable to be fixed to a structure to be mounted in a state in which elastic stretching strain in a longitudinal direction is uniformly applied, and can be performed for a long time. It is an object of the present invention to provide a method of fixing an optical fiber cable capable of maintaining the state throughout.

[0008]

According to the present invention, an optical fiber cable is brought into contact with or close to the surface of a structure to be mounted in a state where a tension for generating a desired elastic elongation strain is applied. After covering half or all of the outer periphery of the cable with the aggregate structure-containing reaction-curable resin base composition together with the surrounding structure surface, the resin base composition is cured, and then the structure surface is cured. Is fixed as a support surface. With this configuration, when coating and covering the surface of the optical fiber cable and the structure with the resin-based composition, since the composition has fluidity, an unnecessary external force is applied to the optical fiber cable. Therefore, the resin-based composition can be easily applied to form a coating layer without changing the longitudinal elastic elongation strain uniformly occurring in the optical fiber cable, and the subsequent curing. In some cases, the aggregate incorporated suppresses the curing shrinkage, and the resin-based composition cures while being applied, so that no extra external force is applied to the optical fiber cable from this point as well. Thus, the optical fiber cable can be fixed to the surface of the structure with the cured coating layer provided with uniform elastic elongation. In addition, since the coating layer adheres to at least half of the outer periphery of the optical fiber cable, the adhesive area to the optical fiber cable is large, and the optical fiber cable is fixed with a large strength to the structure surface, and the cured composition The aggregate contained in the product suppresses the creep of the resin-based composition, so that no creep occurs in the coating layer. Therefore, the optical fiber cable can be kept in the initially attached state for a long period of time. That is, the state where the elastic elastic strain is imparted is fixed to the surface of the structure. Thus, the strain of the structure can be accurately detected over a long period of time. Incidentally, the adhesive strength of the resin-based composition is generally about 100 kg / cm ² , and if it covers the entire outer circumference of the currently used metal sheath tube diameter of 2 mm and the outer circumference of about 6 mm, it covers 100 mm in length. 6
It can withstand a longitudinal stress of 00 kg.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The optical fiber cable used in the present invention has any structure as long as it has an optical fiber capable of measuring the distribution of longitudinal strain by measuring Brillouin scattered light. For example, the optical fiber may be composed of only the optical fiber, but the optical fiber is preferably covered with a metal sheath material, and the optical fiber is fixed to the sheath material by caulking at an appropriate interval. . When an optical fiber cable having this configuration is used, the metal sheath material protects the internal optical fiber well, so that it is possible to prevent the optical fiber from being damaged at the time of attaching the optical fiber cable and during long-term use. The advantage that it can be obtained is obtained.

The structure to which the optical fiber cable is to be attached is arbitrary, such as a bridge, tunnel, building, etc., as long as strain measurement is required. Any material can be used as long as it can adhere the base composition.

The reaction-curable resin-based composition used in the present invention is optional as long as it has an appropriate fluidity when applied and firmly adheres to an optical fiber cable and a structure when cured. Those having long-term durability so that they can be used without deterioration over a long period of time are preferable. The resin-based composition preferably has anticorrosion so that the optical fiber cable and the structure can be covered and protected. Further, when the resin-based composition is applied so as to cover the optical fiber cable, it is necessary to maintain fluidity within an appropriate time required to complete the application operation of a desired length. It is preferable because the work can be easily performed, and it has a characteristic that it gradually cures when curing, so that it hardens without applying an uneven external force to the optical fiber cable to form the optical fiber cable. It is preferable because it can be fixed to an object. Therefore, the resin-based composition is not cured immediately after application, but is at least one cured or semi-cured.
Those that require more than time are preferred. Specific examples of the resin-based composition having these characteristics include resin coatings such as epoxy resin coatings, urethane resin coatings, and polyester resin coatings. Other examples include silicone resin paints and vinyl ester resins.

The aggregate to be incorporated into the resin-based composition contributes to thickening to enable thick coating so that the optical fiber cable can be almost embedded in the applied resin-based composition. And suppresses the shrinkage of the resin-based composition during curing and creep during long-term use. Examples of the material include talc, limestone, silica stone, granules such as alumina, mica flake, and glass flake. , Glass fiber, ceramic fiber and the like.
Fine powders of kaolinite, titanium white, carbon black, and the like, which are blended for the purpose of corrosion prevention, light resistance, coloring, and the like, may be used in combination as appropriate. In addition, the size (medium particle size) of the aggregate is set to 0.
It is preferably about 1 to 1 mm, and the ratio of the aggregate in the mixture of the aggregate and the resin base composition is preferably about 10 to 50% by volume. Specific examples of the reaction-curable resin-based composition containing such an aggregate include commercially available thick-film paints and super-thick-film paints. It is preferable to use an ultra-thick film type epoxy resin paint which is excellent in corrosion resistance and can maintain a large adhesive force for a long period of time.

[0013] The surface of the structure to which the optical fiber cable is to be attached may be painted or unpainted. However, the strength of fixing the optical fiber cable to the structure surface is increased to measure the strain. In order to improve accuracy,
It is preferable to have a surface without painting, for example, a bare steel surface without a coating film or the like. Such a bare steel surface needs to be subjected to an anticorrosion treatment. However, if a resin base composition having anticorrosion properties is used as the resin base composition used in the present invention, the optical fiber cable is made of a steel base material using the resin base composition. When fixed to the surface, the resin-based composition forms an anticorrosion film covering the steel material surface. Therefore, the anticorrosion treatment of the exposed steel surface and the fixing of the optical fiber cable can be performed simultaneously, and the process can be simplified. Before the optical fiber cable is fixed to the surface of the structure with the resin-based composition, the surface of the structure, for example, the surface of the exposed steel material is subjected to ground treatment, primer application, undercoating, intermediate coating, etc. as necessary. May be.

When an optical fiber cable is fixed to a surface of a structure in a painted state, a material having good adhesion to an existing coating film on the surface of the structure (a resin-based composition used for the fixing) may be used. For example, if the existing coating is epoxy-based, the resin-based composition is also selected from epoxy-based paint)
Like the repainting, roughen the existing coating surface,
By applying a resin-based composition after a treatment such as degreasing, the resin-based composition can be satisfactorily adhered to the surface of the structure to fix the optical fiber cable.

Next, a method of fixing an optical fiber cable to a structure will be described with reference to the drawings. FIG. 1 is a schematic perspective view showing a state where an optical fiber cable is fixed to a structure, FIG. 2A is a schematic sectional view taken along the line AA of FIG.
FIG. 2B is a schematic cross-sectional view showing the same part as FIG. 2A with the optical fiber cable covered with a reaction-curable resin-based composition containing an aggregate, and FIG. It is a schematic sectional drawing which shows the modification of (b). 1 and 2, 1
Is an object to be subjected to strain detection. Here, an H-shaped steel is shown as an example. 2 is an optical fiber cable. In fixing the optical fiber cable to a desired mounting area B on the surface of the structure 1, first, the optical fiber cable 2 is guided along the surface of the mounting area B of the structure 1 by the guide rollers 5, 5, and the surface thereof. And the optical fiber cable is fixed outside the guide rollers 5 and the fixed clamp 3 and the movable clamp 4
Hold with. Then, the movable clamp 4 is moved in a direction indicated by an arrow C by a driving mechanism (not shown), and tension is applied to the optical fiber cable 2 between the fixed clamp 3 and the movable clamp 4 to generate elastic stretching strain in the longitudinal direction. Let it.

Here, the elastic stretching strain in the longitudinal direction caused in the optical fiber cable 2 is caused by the members constituting the optical fiber cable (the optical fiber when the optical fiber cable is composed of only the optical fiber, the optical fiber and the sheath member). Each of the optical fiber and the sheath body in the case where the optical fiber cable and the sheath body are stretched within a range having elasticity, thereby generating a tensile stress inside them. It is selected so that the thermal stress is not absorbed by the tensile stress when the expansion is attempted, so that the members constituting the optical fiber cable do not sag (the tensile stress remains). Specifically, it is preferable to select the elastic elongation strain applied to the optical fiber cable 2 so that the elongation strain of the optical fiber itself is in the range of 0.05 to 1.0%. This is because, if the elongation strain of 0.05% or more is given, the slack due to the daily change such as the temperature difference is sufficiently canceled. In addition, elongation strain is 1.0
%, The elongation allowance for measuring the elongation strain caused by the strain of the structure to which the optical fiber cable is attached can be sufficiently left (the elongation limit of the optical fiber itself is 1.5. ~ 2%). The optical fiber cable 2 may be composed of only an optical fiber, but is often composited with another member such as a sheath, and the optical fiber is fixed to another member such as the sheath in a tension state. In some cases, the above 0.05% may be 0.01% for an optical fiber cable. The above 1.0% may correspond to 1.2% in an optical fiber cable. That is, the stretching strain applied to the optical fiber cable 2 is 0.01 to 1.
2% is a preferable range.

When the movable clamp 4 is moved to cause elastic stretching in the longitudinal direction in the optical fiber cable 2, a control method for setting the elastic stretching strain to a desired value is as follows. After measuring the amount of movement of the movable clamp 4 (corresponding to the extensional strain of the optical fiber cable 2) after the state, the movable clamp 4 is moved until the desired elastic extensional strain is generated in the optical fiber cable 2.
Is moved (elongation strain control method), the relationship between the elastic elongation and the tension of the optical fiber cable 2 is measured in advance,
A method of controlling the moving position of the moving clamp 4 so that the tension applied to the optical fiber cable 2 is measured by an appropriate tension meter so that the tension becomes a tension causing a desired elastic elongation strain (a tension control method); A tension is applied to the fiber cable 2, and the strain distribution in the optical fiber at that time is measured by measuring the Brillouin scattered light in the optical fiber from one end of the optical fiber, and the strain at the portion to be fixed becomes a predetermined value. Control method (actual distortion measurement method).

After the optical fiber cable 2 is brought into contact with or close to the surface of the structure 1 while applying a desired tension,
In that state, as shown in FIG. 2B or FIG.
The optical fiber cable 2 is connected to the surface of the structure nearby,
The covering layer 8 is formed by covering with a reaction curable resin base composition containing an aggregate, and then the covering layer 8 is cured to fix the structure surface as a support surface. Here, since the reaction-curable resin-based composition containing the aggregate is in a fluid state when the optical fiber cable 2 is covered, it is impossible for the optical fiber cable 2 to be covered at the time of covering the optical fiber cable 2. The coating can be easily and evenly applied along the optical fiber cable 2 without applying force. In addition, at the time of subsequent curing, the aggregate added suppresses shrinkage of the resin-based composition, so that the coating 8 hardens almost without shrinking, and fixes the optical fiber cable 2 to the surface of the structure 1. For this reason, the optical fiber cable 2 does not receive an extraneous external force at the time of the fixing work to the structure 1, and therefore, the optical fiber cable 2 is maintained in a state where a uniform elastic elongation strain applied in advance is maintained. It can be fixed to the structure 1 as it is.

The area in which the optical fiber cable 2 is covered with the coating layer 8 of the resin-based composition may be such that a part of the outer periphery of the optical fiber cable 2 is exposed as shown in FIG. As shown in FIG. 2 (b), it is not only possible to increase the fixing force of the optical fiber cable 2 to the structure 1 but also to make the optical fiber cable 2 completely cover the entire circumference of the optical fiber cable 2. This is preferable because it can be protected by the coating layer 8. As shown in FIG. 2C, when a part of the outer periphery of the optical fiber cable 2 is exposed, a region of at least half of the outer periphery of the optical fiber cable 2 is covered so as to securely restrain the optical fiber cable 2. It is covered with layer 8.

The covering width w of the surface of the structure 1 by the coating layer 8 of the resin-based composition is preferably as large as possible because the adhesive strength of the coating layer 8 to the surface of the structure can be increased. It is no longer necessary to increase the adhesive strength. For this reason, the covering width w is limited by the optical fiber cable 2
Is preferably about 3 to 30 times the thickness (outer diameter).

As shown in FIG. 2B, when the entire circumference of the optical fiber cable 2 is covered with the coating layer 8 of the resin-based composition, the cover thickness t of the optical fiber cable portion is not so small. Since the meaning of covering with the coating layer 8 disappears,
Although it is necessary to increase the thickness to a certain extent, if a certain thickness is ensured, even if the thickness is further increased, it is not enough to improve the adhesion of the optical fiber cable 2 and the protection of the optical fiber cable 2. No longer contributes. Therefore, this cover thickness t
Is preferably about 0.1 to 2.0 times the thickness of the optical fiber cable 2.

In the longitudinal direction of the optical fiber cable 2, the range in which the optical fiber cable 2 is covered with the coating layer 8 of the resin-based composition depends on the total length of the optical fiber cable 2 located in the mounting area B of the structure 1. However, if the optical fiber cable 2 can be adhered to the structure so that the optical fiber cable 2 is integrally deformed with the structure 1, only the region having an appropriate interval in the longitudinal direction may be used. As described above, the adhesive strength of the resin-based composition is sufficiently large, and sufficient tension can be maintained even in intermittent coating.

Prior to covering the optical fiber cable 2 with the coating layer 8 of the resin base composition and fixing it to the structure 1, if necessary, the optical fiber cable 2 is applied to the surface of the structure 1 by using an appropriate means. May be temporarily stopped. The temporary fixing is performed when the optical fiber cable 2 is covered with the coating layer 8 of the resin-based composition.
This is for keeping the optical fiber cable 2 in contact with or close to the surface of the structure 1.
When the optical fiber cable 2 is mounted horizontally on a vertical surface of the structure 1 or on a ceiling surface, as shown in FIG.
Is preferably used when there is a risk of bending downward due to its own weight. The means used for the temporary fixing is such that, when the optical fiber cable 2 in a tensioned state is temporarily fixed, an extra external force is not applied to the optical fiber cable 2 so that the stretching strain is not made non-uniform. It is preferable to use an instantaneous adhesive such as a cyanoacrylate instant adhesive or an epoxy instant adhesive, or an adhesive tape such as an aluminum adhesive tape or a stainless steel adhesive tape. These temporary fixing means may be removed while covering the optical fiber cable 2 with a resin-based composition,
If there is no problem, it may be left as it is and embedded in the coating layer 8 made of the resin-based composition.

The fixing of the optical fiber cable 2 to the surface of the structure 1 is performed by using the optical fiber cable mounting area B on the surface of the structure 1.
When the length of the mounting area B is short, the entire length of the mounting area B is performed at a stretch by the above-described method. However, when the mounting area B is long, it is not necessary to perform the entire processing at a stretch over the entire length. Good. At that time, after fixing the optical fiber cable 2 with the resin-based composition coating layer 8 in one section,
A method of shifting to the fixing operation of the adjacent section may be adopted, or only the temporary fixing of the optical fiber cable 2 is sequentially performed for a plurality of sections, and the temporary fixing of the appropriate number of sections is performed. A method of applying a resin-based composition to the section to form the coating layer 8 and curing the coating layer 8 to fix the optical fiber cable may be adopted.

As described above, the optical fiber cable 2 fixed to the surface of the structure 1 is coated with the resin-based composition while the desired elastic elongation strain is uniformly applied to the optical fiber cable 2. By 8, it is fixed to the surface of the structure 1. Since the coating layer 8 of the resin-based composition adheres to the outer periphery of the optical fiber cable 2 and the surface of the structure 1 in a wide area, the adhesive force of the optical fiber cable 2 to the surface of the structure 1 is large. For this reason, when the structure 1 undergoes an extension strain or a contraction strain, the optical fiber cable 2 is distorted integrally with the structure 1, and the optical fiber cable 2 has an extension strain generated in the structure 1. Alternatively, an elongation strain or a contraction strain corresponding exactly to the contraction strain occurs. For this reason, the Brillouin scattered light in the optical fiber cable 2 is measured from one end of the optical fiber cable 2 to measure the distribution of longitudinal strain, thereby accurately detecting the strain occurring in the structure 1. Can be. The optical fiber cable 2 is used for a long period of time for strain measurement while being fixed to the surface of the structure 1, and the aggregate mixed in the cured coating layer 8 is made of a resin-based composition. Since creep is suppressed, the optical fiber cable 2 is maintained in a state of being fixed to the surface of the structure for a long period of time in an initial mounted state, that is, in a state in which uniform elastic elongation is imparted. You. Therefore, it is possible to accurately detect the distortion of the structure over a long period of time. Also, from the viewpoint of maintenance and maintenance, since the present method embeds a half or entire circumference of the optical fiber cable 2 in the coating layer 8, the exposure of the optical fiber cable 2 is far less than that of the conventional method. Alternatively, the optical fiber cable 2 is not exposed at all, and
The optical fiber cable 2 is protected by the coating layer 8, for example,
Cutting and deformation of the optical fiber cable due to negligence, damage by small animals, deformation of the optical fiber cable due to contact with or intrusion of the invertebrate, and the like have a great practical advantage.

[0026]

[Example 1] An incoloy-coated optical fiber (outer diameter of an incoloy tube: 2 mm) was prepared as an optical fiber cable, and the structure to which the optical fiber cable was attached was 200 mm high, 100 mm wide, and long. An H-section steel for general structure having a length of 7 m, a web thickness of 3.2 mm, and a flange thickness of 6.0 mm was prepared. Then, the optical fiber cable 2 is stretched in the longitudinal direction of the H-shaped steel in the form shown in FIG. 1, and the tension is applied to the optical fiber cable 2 using a tension meter. The tension (approximately 30 kg) generated is set, and in this state, an ultra thick film type epoxy resin paint Napco Barrier 2M (manufactured by Kansai Paint Co., Ltd.) is applied to the entire length of the optical fiber cable along the H-section steel.
Was applied so as to form a coating layer having the shape shown in FIG. 2 (b), and was kept in that state for 24 hours to cure the coating layer. Then, from the optical fiber cable 2 to the fixing clamp 3
And the moving clamp 4 was removed, and curing was performed for 3 days. The maximum thickness of the formed coating layer was 3 mm, and the width w was 20 mm.

Comparative Example 1 The same H-section steel as in Example 1 was used.
The same optical fiber cable 2 is stretched along with the same tension applied, and a cyanoacrylate instant adhesive Arteco M (manufactured by Alpha Giken Co., Ltd.) is applied and bonded to the entire length of the optical fiber cable aligned with the H-shaped steel. After 30 minutes, the fixed clamp 3 and the movable clamp 4 were removed from the optical fiber cable 2.

Comparative Example 2 The same H-section steel as in Example 1 was used.
The same optical fiber cable 2 is stretched along with the same tension applied, and the holding jig 10 shown in FIG.
The fixing clamp 3 and the moving clamp 4 were removed from the optical fiber cable 2 immediately after fixing with a gilt (not shown).

With respect to the optical fiber cables 2 in the test pieces of Example 1 and Comparative Examples 1 and 2 prepared as described above, the respective initial strain rates were measured using an optical fiber strain / loss analyzer AQ8602 manufactured by Ando Electric Co., Ltd. AQ86
Using 02B, measurements were made at 1 m pitch (measurement points a to g). At the time of measurement, a normal strain gauge was also attached to each H-shaped steel, and the measurement was performed after confirming that no strain was generated. Table 1 shows the measurement results. The unit of the distortion rate in the table is%.

[0030]

[Table 1]

As is evident from Table 1, in Comparative Example 2, considerable variation was observed in the initial strain rate. This is due to the delicate way of pressing and the change in pressing pressure when the holding jig 10 is applied to the optical fiber cable 2 and fixed with a shim.
This is presumably because non-uniform external forces acted on the optical fiber cable 2 to cause non-uniform elongation strain. On the other hand, in Example 1 and Comparative Example 1, the initial strain rate was close to the set value, and the variation was small. This is because the optical fiber cable was fixed with an ultra-thin film type epoxy resin paint (Example 1) or a cyanoacrylate-based instant adhesive (Comparative Example 1). Therefore, it is considered that the optical fiber cable was fixed while maintaining the initially applied uniform elongation strain.

Next, the test pieces of Example 1 and Comparative Examples 2 and 3 were left outdoors for 3 months, and then the same measurement was performed. Table 2 shows the results.

[0033]

[Table 2]

As is clear from Table 2, in Example 1, there was no change in the distortion factor. Therefore, the strain of the H-shaped steel can be accurately measured using the optical fiber cable. On the other hand, in Comparative Example 1, the optical fiber cable was peeled off from the H-shaped steel, and the strain could no longer be measured. In Comparative Example 2, a decrease in the measured strain rate was observed even though no strain occurred in the H-section steel. This is because the sheath material of the optical fiber cable 2 pressed against the H-shaped steel by the holding jig 10 causes a phenomenon such as creep over time, and the fixing force of the holding jig 10 decreases to cause slippage. This is probably because the elastic elongation strain initially applied to the optical fiber cable was reduced. Therefore, in this state, even if an attempt is made to measure the strain of the H-shaped steel using the optical fiber cable, a large error occurs. As described above, in Comparative Examples 1 and 2, when used for a long time, the strain measurement of the H-section steel becomes impossible, or the measurement error increases. In contrast, in Example 1, it was confirmed that good strain measurement was possible over a long period of time. Further, in Comparative Examples 1 and 2, H
Corrosion was observed around the optical fiber cable fixing portion of the section steel, but no such corrosion was observed in Example 1.
Therefore, in Example 1, it was confirmed that the coating layer used for fixing the optical fiber also had an anticorrosion action, and that it was not necessary to separately perform anticorrosion treatment.

[0035]

As described above, according to the method of the present invention, an optical fiber cable is firmly fixed on a surface of a structure whose strain is to be measured in a state where a uniform longitudinal elastic stretching strain is applied. And the state can be maintained for a long period of time. For this reason, if the optical fiber cable is fixed to a structure by the method of the present invention, even if any of longitudinal elongational strain and compressive strain occurs in the structure, the optical fiber cable responds to the elongational strain and compressive strain. Elongational and compressive strains also occur in the fiber cable in the longitudinal direction. Therefore, by measuring the strain distribution in the optical fiber cable, the strain generated in the structure can be measured. Can be measured with high accuracy.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a state where an optical fiber cable is fixed to a structure.

2A is a schematic sectional view taken along the line AA of FIG. 1; FIG. 2B is a schematic sectional view showing the same part as FIG. 1A with the optical fiber cable covered with a resin base composition; (C) is a schematic sectional view showing a modification of (b).

FIG. 3 is a schematic sectional view showing a fixed state of an optical fiber cable in Comparative Example 2.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Structure 2 Optical fiber cable 3 Fixed clamp 4 Moving clamp 5 Guide roller 8 Coating layer 10 Holding jig

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) H02G 3/30 H02G 9/00 D 9/00 3/26 L (72) Inventor Yoshimasa Hiramatsu Kawasaki-shi, Kanagawa 2-17-8 Tonomachi, Kawasaki-ku Dai-ichi Kogyo Kogyo Co., Ltd. (72) Inventor Yasunori Tsuchiya 2-17-8 Tonomachi, Kawasaki-ku, Kawasaki-shi, Kanagawa Prefecture F-term in Dai-ichi Kogyo Kogyo Co., Ltd. 2F065 AA65 CC14 CC40 FF41 LL02 PP01 2H038 AA05 CA33 5G363 AA04 BA10 DA20 DB40 5G369 AA16 BA01 BB03 CB01 EA01 EA04

Claims (5)

[Claims] 1. A method for fixing a strain-detecting optical fiber cable to a structure while applying tension to the structure in order to measure the distribution of strain generated in the structure. An optical fiber cable in a tensioned state causing an elongation strain is brought into contact with or in proximity to the surface of the structure, and a half or entire circumference of the outer circumference of the cable is maintained while the tension is applied to the surface of the structure in the vicinity. A method for fixing an optical fiber cable, comprising fixing a structure surface as a support surface by covering the structure with an aggregate-containing reaction-curable resin-based composition and then curing the resin-based composition. 2. The method of fixing an optical fiber cable according to claim 1, wherein the covering width of the resin-based composition is set to be 3 to 30 times the thickness of the optical fiber cable. 3. The entire circumference of the optical fiber cable is covered with the resin-based composition, and the cover thickness of the optical fiber cable portion is set to 0.1% of the thickness of the optical fiber cable.
The method for fixing an optical fiber cable according to claim 1 or 2, wherein the ratio is up to 2.0 times. 4. The volume ratio of the aggregate in the aggregate-containing reaction-curable resin-based composition is set to 10 to 50%.
4. The method for fixing an optical fiber cable according to any one of items 1 to 3. 5. The method for fixing an optical fiber cable according to claim 1, wherein the aggregate-containing reaction-curable resin-based composition is a super-thick film type epoxy resin paint.