JP2006250647A - Wire cable, and tension measurement system and method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To measure the correct tension of the wire cable to be used for a structure at a remote place without leaving the place at all, at the requested time. <P>SOLUTION: A strain detection means for detecting the strain in the axial direction is built in the wire cable which is stranded with a plurality of strands. For the strain detection means, an optical fiber sensor 3 formed with an optical fiber cable 2 is built in the wire cable so as to deform corresponding to expansion and contraction of the wire cable. From the deformation of the optical fiber sensor 3, the variation of frequency of the incident light, or reflection, refraction or interference of the light is detected. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wire cable for supporting a structure, particularly a wire cable for a bridge, and a tension measuring system and a tension measuring method using the cable.

  With respect to a structure that supports a member that is a wire cable, various methods have conventionally been tried as a method for measuring the tension of the wire cable. For example, a technique of attaching a strain gauge to a wire cable and obtaining the tension of the wire cable based on the output of the strain gauge is an alternative. Recently, it is the mainstream to measure tension by a technique called vibration method.

  This vibration method is, for example, as shown in Patent Document 1, in which a predetermined vibration is applied to a wire cable, and the tension is obtained from the natural frequency of the wire cable using a differential equation relating to the vibration of the string. Is the method.

JP 2001-255222 A

  However, when the object of measurement is a wire cable of a bridge, the chance of measuring the tension is limited due to traffic conditions. For this reason, with the technique using strain gauges, there are only a few chances, such as during a simultaneous inspection of a bridge, except when a bridge is installed.

  In addition, as described above, the vibration method is a method for indirectly obtaining the tension from the natural frequency of the cable, so an error is inevitably generated between the tension obtained by the vibration method and the actual tension.

  The present invention has been made in view of such problems, and an object of the present invention is to provide a wire cable, a tension measurement system, and a tension measurement method that can obtain accurate tension at a desired time.

  In the present invention, in order to solve the above-mentioned problems, the following solution means is adopted.

  The first adopted is a wire cable formed by twisting together a plurality of strands, and a strain detection means for detecting axial strain of the wire cable is incorporated in the wire cable, The strain detection means is an optical fiber sensor made of an optical fiber, and this optical fiber sensor is incorporated in the wire cable so as to be deformed as the wire cable expands and contracts, and the frequency of the incident light is changed by the deformation of the optical fiber sensor. A wire cable that detects changes or reflection, refraction, or interference of light.

  With regard to such a wire cable, in the present invention, an insertion hole formed along the axial direction is formed in one of the strands, the optical fiber sensor is inserted into the insertion hole, and the axial direction is It was configured to expand and contract with the expansion and contraction of the strands.

  Secondly, a tension measuring system for measuring the tension of a wire cable formed by supporting a member constituting a structure in a fixed posture and twisting a plurality of strands to each other, A strain detection unit that is incorporated in the wire cable and detects strain of the wire cable; a tension calculation unit that calculates a tension acting on the wire cable based on detection of the strain detection unit; and detection of the strain detection unit An optical fiber formed by using a part of the optical fiber cable, the signal communication means being an optical fiber cable, and transmitting the signal from the strain detection means to the tension calculating means. This optical fiber sensor is incorporated in the wire cable so as to deform as the wire cable expands and contracts, and the optical fiber A change in the frequency of light incident on the optical fiber sensor or reflection, refraction, or interference of light is detected by deformation of the sensor, and the tension calculation means detects the wire cable based on the detection content of the optical fiber sensor. It is the tension measurement system which calculates the tension | tensile_strength of.

  Thirdly, a part of the optical fiber cable is used to measure the tension of the wire cable formed by supporting the members constituting the structure in a fixed posture and twisting the strands together. The optical fiber sensor formed as described above is incorporated into the wire cable, the optical fiber sensor is deformed as the wire cable expands and contracts, and the change in the frequency of light incident on the optical fiber sensor is generated along with the deformation. Or a tension measuring method that detects reflection, refraction, or interference of light and calculates the tension of the wire cable by a tension calculation means based on a change in the detected frequency of light, or reflection, refraction, or interference of light. Adopted.

  According to the present invention, when the tension of a wire cable is measured, the tension can be directly measured from the strain generated in the wire cable. For this reason, it becomes possible to suppress the occurrence of an error between the measurement result and the tension actually generated in the wire cable as much as possible, and an accurate value can be measured.

  Further, since the optical fiber sensor is used as the strain measuring means, an optical fiber cable already provided as a communication network can be used as the communication means. As a result, it is possible to perform measurement even from a base site or an office building that is remote from the structure to be measured, for example, a measuring device.

  In particular, when the object of measurement is a wire cable that connects a bridge column and a floor slab, measurement on site is limited due to traffic. However, according to the present invention, since it can be measured from a remote place, the tension of the wire cable can be measured at any time regardless of traffic.

  Furthermore, by using an optical fiber communication network, centralized management can be performed at a single location for a plurality of structures.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 schematically shows a tension measurement system for a wire cable 13 used as a cable for a cable-stayed bridge according to an embodiment of the present invention. This tension measuring system includes an optical fiber sensor 3 incorporated in a wire cable 13, an office building 20 provided with a computer 7 for performing various control and calculation processes necessary for measurement, and a bridge in which the optical fiber sensor 3 is incorporated. 10 and an optical fiber cable 2 as a communication network for connecting the office building 20 to each other.

  As shown in FIG. 2, the bridge 10 includes columns 11 at regular intervals in the extending direction of the floor slab 12. For each column 11, the floor slab 12 and the column 11 include a plurality of wires. They are connected by a cable 13. These wire cables 13 obliquely connect the support column 11 and the floor slab 12 so as to be symmetric with respect to the extending direction of the floor slab 12 around the support column 11. This tension measuring system is intended to measure the tension of the wire cable 13.

  FIG. 3 is an enlarged view of one of the connecting portions of the support column 11 and the wire cable 13.

  A plurality of holding brackets 14 are fixed to the upper portion of the support 11 so as to be arranged in the height direction, and the tips of the wire cables 13 are held by the support 11 so as to face each other. The holding bracket 14 includes a fixing surface 15 that is fixed to the support column 11, and a holding surface 16 that extends obliquely upward from both front and rear sides of the fixing surface 15 and is formed in a divergent shape. Through holes are formed in the holding surface 16, and the tip of the cable for the inclined bridge is passed through the hole and held by the holding bracket 14.

  Further, a cylindrical cable guide 17 that protrudes obliquely downward is provided on the front and rear surfaces of the column 11. A through hole is formed in the center of the cable guide 17 so as to penetrate the cable guide 17 in the axial direction, and the wire cable 13 extending obliquely is passed through the through hole. The cable guide 17 guides the wire cable 13 extending from the floor slab 12 toward the column 11 toward the holding bracket 14.

  On the other hand, an end socket 18 is provided at the tip of the wire cable 13. The end socket 18 projects outward in the radial direction of the wire cable 13 like a flange, and serves as a stopper for preventing the wire cable 13 passed through the through hole of the holding bracket 14 from coming out of the holding bracket 14. Function.

  As shown in FIG. 4, the tip of the optical fiber cable 2 is incorporated in the tip of the wire cable 13 thus provided. A tip portion of the optical fiber cable 2 is formed as an optical fiber sensor 3.

  FIGS. 5 and 6 are examples of an enlarged model of the tip of the wire cable 13 in which the optical fiber sensor 3 is incorporated.

  The wire cable 13 is formed as a single cable by twisting together a plurality of strands 23 made of steel wires. Of the strands 23 constituting the cable-stayed bridge cable, an insertion hole 25 extending in the axial direction from the end portion is formed in the strand 23 located in the center and having no twist. The optical fiber sensor 3 is inserted into the insertion hole 25. The inserted optical fiber sensor 3 is fixed to insertion holes 25 on both sides in the axial direction with a diffraction grating 4 to be described later interposed therebetween, and expands and contracts integrally with the extension and contraction of the strands 23 in the axial direction. It is configured to

  The optical fiber sensor 3 may be incorporated at the tip of the wire cable 13 as shown in FIGS. In this embodiment, the optical fiber sensor 3 is inserted between the strands 23 constituting the wire cable 13 and incorporated into the tip of the wire cable 13 so as to be sandwiched between the strands 23. . Also in this case, the both sides of the optical fiber sensor 3 in the axial direction sandwiching the diffraction grating 4 are fixed to the strands 23, and as the strands 23 extend and contract in the axial direction, they extend and contract integrally therewith. It is configured.

  Here, the principle of the optical fiber sensor 3 used in this tension measuring system will be described.

  In general, the optical fiber sensor 3 includes (1) FBG (Fiber Bragg Grating) that uses a change in wavelength, (2) BOTDR (Brillouin Optical Time Domain Reflectmeter) that uses the frequency of Brillouin scattered light, and (3) interference of light. There are those using various properties such as SOFO (Surveillance 'Ouvrages par Fibers Optiques) using properties, (4) OSMOS (Optical Stand Monitoring System) using bending loss of optical fiber cable 2 of transmitted light .

  As the optical fiber sensor 3 used in this tension measuring system, it is optimal to use an FBG type optical fiber sensor, but any of these may be used.

  FIG. 9 is a diagram schematically showing the outline of the FBG type optical fiber sensor 3. The optical fiber sensor 3 is formed with a diffraction grating 4 that reflects light. The diffractive grating 4 is composed of a pair of gratings 40 arranged with a small distance d in the axial direction of the optical fiber sensor 3.

  When the optical fiber sensor 3 having the diffraction grating 4 is distorted by ε in the axial direction, the grating interval d is also changed accordingly.

  The diffraction grating 4 has a characteristic of reflecting only incident light having a specific frequency out of incident light incident on the optical fiber cable 2 and allowing light of other frequencies to pass through as it is.

  Here, the wavelength λ of the incident light having a specific frequency reflected by the diffraction grating 4 is expressed by the following Expression 1. In Equation 1, n is the average refractive index of the core portion, and d is the lattice spacing.

      λ = 2nd (Formula 1)

  When the optical fiber sensor 3 is distorted in the axial direction by ε and the grating interval d is changed, the wavelength of the incident light reflected by the diffraction grating 4 is expressed by Equation 2 with respect to the incident light. To change.

Δλ = λ (1-P) ε (Expression 2)
P represents the Poisson's ratio.

In the optical fiber sensor 3, it is possible to measure the strain and tension of an object to which the optical fiber sensor 3 is attached by measuring a change in wavelength. The wavelength is linear with respect to the strain of the optical fiber sensor 3. Although the amount of change in wavelength depends on the wavelength of incident light, it is about 1.2 × 10 ⁻¹² m / μStrain.

  Such an FBG is most suitable for the system. However, as described above, BOTDR, SOFO, and OSMOS can be used. Hereinafter, the principle of these methods will be briefly described.

  BOTDR uses “strain dependency” in which Brillouin scattered light causes a frequency change linearly with respect to a change in strain of an optical fiber.

  FIG. 10 illustrates a distortion image, and FIG. 11 illustrates a linearity image. As shown in FIG. 10, when tension is applied to the optical fiber and distortion occurs, the frequency peak shifts due to the spectral distribution of the Brillouin scattered light. Further, for example, the linearity of the frequency shift due to the strain dependency of the incident light having the wavelength λ = 1.55 μm is shown in FIG.

  Thus, since the relationship between the frequency of Brillouin scattered light and strain has linearity, it can be applied to strain measurement by measuring the frequency shift amount of Brillouin scattered light.

This BOTDR can be used as a distributed sensor. That is, a pulse wave is incident on the optical fiber, and the return time and intensity of the Brillouin scattered light as the back scattered light that has returned are measured. The distance L to the measurement position of the scattered light data returned from this time can be obtained by the following equation 3.

L = CT / 2n (Expression 3)
C: Speed of light
T: Time until detection
n: Refractive index of optical fiber

  Then, by performing the same measurement while gradually changing the frequency of the incident light, the spectrum distribution of the frequency shift of the Brillouin scattered light is obtained for each distance. FIG. 12 illustrates the image.

  For example, when it is desired to know the distortion value at a certain position, the distortion is obtained from the frequency distribution of each distance portion to that position. In the example shown in FIG. 12, the shift amount is obtained from the spectrum when the figure is crossed diagonally right upward from the position of Z1, and converted into distortion. This operation is performed for each distance to obtain a continuous strain distribution.

  In the figure, the strain values of ε1 and ε2 are obtained for each length of ΔL. The length of ΔL can be expressed by the following expression 4 where c is a coefficient and the incident pulse width is ω.

      ΔL = cω / 2n (Expression 4)

  In this resolution, ΔL propagates at a certain angle from both sides of the pulse width of the incident pulsed light. And when two scattered lights overlap on a straight line, two scattered lights are not isolate | separated. Therefore, the distortion value is measured in the length corresponding to the distance between these two (both sides of the pulse width).

  Next, the principle of SOFO will be described.

  13 and 14 schematically show the principle when a SOFO type optical fiber sensor is used.

  The SOFO type optical fiber sensor 50 uses two optical fibers 53 and 54 as shown in FIG. One is a measurement optical fiber 53 and the other is a reference optical fiber 54. The two optical fibers 53 and 54 are branched by a coupler 56 connected to the optical fiber sensor 50, and are paralleled by a pair of fixing portions 52 arranged at a predetermined interval in the axial direction of the optical fiber sensor 50. It is fixed in this way. A mirror 55 is connected to the tips of these two optical fibers 53 and 54. Between the fixed parts 52 is a movable part 51. The measurement optical fiber 53 is pre-tensioned, while the reference optical fiber 54 is spirally wound.

  In this SOFO type optical fiber sensor 50, when the movable portion 51 is displaced, the length of the measurement optical fiber 53 changes. However, the length of the reference optical fiber 54 is unchanged.

  FIG. 14 shows an example in which the SOFO system optical fiber sensor 50 and the leading unit 60 are connected by an optical fiber cable 71 and a relay box 70 to complete the SOFO system.

  According to this SOFO system, first, white light is sent from the LED 64 as a light source to each optical fiber sensor 50 via the connector 68, the optical fiber cable 71, and the relay box 70. The light transmitted to each optical fiber sensor 50 is branched into the measurement optical fiber 53 and the reference optical fiber 54 by the coupler 56 of the respective optical fiber sensor 50. Then, the light is reflected by the mirror 55 provided at the tip, condensed again on the coupler 56, and returned to the reading unit.

  At this time, since the measurement optical fiber 53 and the reference optical fiber 54 are different in length (original length difference + displacement amount of the movable portion), interference occurs in the returned light. Therefore, the light is split into the fixed portion 65 and the movable portion 66 built in the reading unit 60 by the coupler 62 arranged inside the reading unit 60. And it reflects with the mirror 67 provided in the fixed part 65 and the movable part 66, respectively, and finds a peak interference position. However, correction regarding the difference in length between the two optical fibers 53 and 54 in the optical fiber sensor 50 is performed at this time.

  The SOFO system is a method for measuring the displacement amount generated in the movable portion 51 of the optical fiber sensor 50 as light interference and measuring it as described above. Note that a personal computer 61 is connected to the coupler 62 via the PD 63 in order to perform specific data analysis. Further, by connecting to the communication means using the modem 69, data analysis at a remote place can be performed.

  Finally, the principle of OSMOS will be described.

  The OSMOS is a sensor to which the concept of light bending loss (microbending) is applied.

  As regards the light refraction, considering the manner in which light is incident on the small grad I from the core II having a large refractive index, the three embodiments shown in FIG.

  A mode A is a case where the light A1 is incident at an angle of θA and is divided into a refracted light A2 that is refracted at a refraction angle θA2 and a reflected light A3 that is reflected at an angle θA.

  In the mode B, the incident angle of light is a certain angle θB, the refraction angle θB2 is 90 degrees, and the light travels along the boundary surface. The incident angle θB at this time is called a critical angle.

  And the aspect of C is a case where incident angle (theta) C is more than a critical angle. In this case, the light is not refracted but undergoes total reflection, and all becomes reflected light C2.

  In the optical fiber, light propagates with total reflection as in the case of C. Bending loss of light occurs when the incident angle becomes less than the critical angle. FIG. 16 illustrates this concept. When light enters the optical fiber, the light propagates through the core while being totally reflected. When the light reaches the bent portion as shown in FIG. 16, a portion having a small incident angle is generated, and light radiated out of the core is generated. This loss amount depends on the radius of curvature R of the light.

  OSMOS measures distortion by measuring this loss.

  In the present invention, any of these methods can be used. In the following, the case where the FBG type optical fiber sensor 3 is used will be described as an example with reference to FIGS. 1 to 9 again.

  The optical fiber sensor 3 is obtained by processing the tip of the optical fiber cable 2 as described above. The optical fiber cable 2 including the optical fiber sensor 3 is provided as a general communication network, and connects the bridge 10 and the office building 20.

  The office building 20 is provided with an optical unit 6 and a computer 7 connected to the optical unit 6. The optical unit 6 is a light source that makes light having a predetermined wavelength incident on the optical fiber sensor 3 via the optical fiber cable 2, a light receiving unit that receives light reflected from the optical fiber sensor 3, and light received by the light receiving unit. It has a function such as an interface for converting to an electrical signal, and the optical unit 6 measures the tension.

  The computer 7 connected to the optical unit 6 functions as a controller that sends commands such as measurement start / end to the optical unit 6 and processes the measurement data obtained by the optical unit 6 into a desired shape. Or function as a data processing unit, such as recording measurement data on a recording medium.

  The optical unit 6 calculates the distortion of the wire cable 13 based on the change in the wavelength detected by the optical fiber sensor 3 based on the reflected light signal transmitted from the optical fiber sensor 3 via the optical fiber cable 2. Then, based on the calculated strain, stress and tension are calculated.

  If the system is designed so that the optical unit 6 generates a trigger at regular time intervals and repeats the measurement every time the trigger is raised, how does the tension of the target wire cable 13 change over time? Can be automatically measured.

  According to the tension measurement system having the above configuration, the tension of the wire cable 13 is measured by the following procedure.

  First, light enters the optical fiber cable 2 from the optical unit 6. Incident light is transmitted through the optical fiber cable 2 and reaches the bridge 10. As described above, the tip of the optical fiber cable 2 is processed as the optical fiber sensor 3 and is incorporated in the tip of the wire cable 13 of the bridge 10, so that incident light finally reaches the tip of the wire cable 13. . Of the incident light reaching the optical fiber sensor 3, incident light having a specific frequency is reflected by the diffraction grating 4.

  Here, since the wire cable 13 connects the support column 11 and the floor slab 12 in a state where a certain tension is applied in advance, the wire cable 13 is distorted in the extending direction. And since the optical fiber sensor 3 is being fixed to the strand 23 so that distortion may be integrated with the distortion of this wire cable 13, the optical fiber sensor 3 is also distorted in the extending direction similarly. For this reason, the space | interval d of the grating | lattice 40 which comprises the diffraction grating 4 is expanded rather than the state with no load of the optical fiber sensor 3. FIG.

  When incident light is reflected by the diffraction grating 4, the wavelength λ of the incident light also changes by Δλ as the grating interval changes.

  The reflected light with the changed wavelength is again received by the optical unit 6 provided in the office building 20 through the optical fiber cable 2 as a communication network. The optical unit 6 measures the wavelength change Δλ from the wavelength of the received reflected light and the wavelength of the incident light, and calculates the distortion based on this. Then, stress and tension are calculated from the calculated strain.

  The calculated tension is processed into a desired format, such as graphed or recorded on a data sheet of a predetermined format, by a computer 7 connected to the optical unit 6. Further, the calculated data is recorded on a recording medium, and the data is stored. At this time, as the division of roles between the optical unit 6 and the computer 7, the optical unit 6 may simply measure only the wavelength change Δλ, and the computer 7 may perform the subsequent processing. If the data processing and storage are performed for each of the plurality of wire cables 13 provided on the bridge 10, it is possible to immediately identify which wire cable 13 has an abnormality, and to take a quick response. Furthermore, if measurement is performed on all the columns 11 provided on the bridge 10, the entire bridge 10 can be always placed on the basis of monitoring.

  As described above, the case where the tension measurement system is applied only to the bridge 10 installed in one place has been described. However, if the bridge 10 is installed in an area where the optical fiber cable 2 as a communication network extends, one place is provided. Can measure the wire cables 13 of the plurality of bridges 10 at the same time.

  The optical fiber sensor has been described so as to be embedded inside the outer edge of the wire cable, such as by incorporating the optical fiber sensor inside the wire of the wire cable. However, the optical fiber cable is attached to the surface portion of the wire cable. May be provided.

  In FIG. 17, the end socket 18 of the wire cable 13 is provided with an insertion hole 18a in the axial direction of the wire cable 13, and the optical fiber cable 2 is inserted through the insertion hole 18a. And the optical fiber sensor 3 provided at the front-end | tip of the optical fiber cable 2 is arrange | positioned between the outer surface of the wire cable 13, and the coating | coated part 13a, and the optical fiber sensor 3 is located in the outer surface of the wire cable 13. The wire 23 is bonded with an adhesive. Then, the optical fiber sensor 3 is covered with a coating material 45 from the outside.

  Thus, even if the optical fiber sensor 3 is bonded to the outer surface of the wire cable 13, the optical fiber sensor 3 detects the distortion of the wire cable 13.

  18 and 19 show another embodiment in which the optical fiber sensor 3 is bonded to the outer surface of the wire cable 13.

  In this embodiment, a cut portion 49 is formed in a part of the covering portion 13 a in the vicinity of the end socket 18 of the wire cable 13. The cut portion 49 partially exposes the outer surface of the wire cable 13 disposed inside the covering portion 13a. The optical fiber sensor 3 is bonded to the strand 23 located on the outer surface of the wire cable 13 at the notch 49. The bonded optical fiber sensor 3 is covered with a covering material 45 from the outside. In addition, although the cut | notch part 49 may be formed in the coating | coated part 13a previously, you may cut and form the coating | coated part 13a partially in the field.

  The optical fiber sensor 3 used in this embodiment is connected to the tip of an optical fiber cable 2 that is cut short to a predetermined length. A connector 46 for connection is provided at the rear end of the optical fiber cable 2 and is configured to be connected to a communication optical fiber cable (not shown) via the connector 46.

  Note that the method of bonding the optical fiber sensor 3 to the outer surface of the wire cable 13 is not limited to the form in which the optical fiber sensor 3 is provided near the end of the wire cable 13, and any position in the axial direction of the wire cable 13 can be used. Can be provided.

  In this case, the optical fiber sensor 3 may be provided as follows.

  In the embodiment shown in FIG. 20, a clamp 80 is used. The clamp 80 is formed in an annular shape and includes a covering portion 81 that covers the outer peripheral surface of the wire cable, and a tightening portion 82 that expands and contracts the covering portion 81 in the radial direction. The covering portion 81 is formed with an axially extending slit having a predetermined gap in a part in the radial direction. The tightening portion 82 is formed such that two plate members arranged at the same interval as the width of the slit project outward in the radial direction of the wire cable 13. Then, three fastening bolts 83 are arranged in the axial direction of the wire cable 13 and attached to each plate material constituting the fastening portion 82.

  The clamp 80 is configured to tighten the tightening bolt 83 to narrow the width of the slit formed in the covering portion 81, thereby tightening the outer peripheral surface of the wire cable 13.

  The optical fiber sensor 3 is bonded to a strand located on the outer surface of the wire cable 13, and the outside is covered with a clamp 80. The optical fiber sensor 3 is tightened from the outside by a clamp 80 and firmly adhered to the outer peripheral surface of the wire cable 13. Thereby, peeling is prevented and distortion of the wire cable 13 is reliably detected.

  As a means for bringing the optical fiber sensor 3 into close contact with the outer surface of the wire cable 13, a taping 85 may be used as shown in FIG.

  Also in this embodiment, the optical fiber sensor 3 is bonded to the strand located on the outer surface of the wire cable 13. The bonded optical fiber sensor 3 is covered from the outside with an iron plate 48 having a thin plate pressure formed in an elongated rectangular shape. Then, the taping 85 is wound around the outer peripheral surface of the wire cable 13, and the optical fiber sensor 3 is brought into close contact with the outer peripheral surface of the wire cable 13 by the taping 85 together with the iron plate 47. The taping 85 is wound around a range longer than the length of the iron plate 48 in the axial direction of the wire cable 13 so that the optical fiber sensor 3 is completely hidden. The taping 85 may be a commonly used vinyl tape, gum tape or the like.

1 is a schematic diagram of a tension measurement system according to an embodiment of the present invention. The side view of the bridge which shows an example of the bridge provided with the wire cable used as the object of tension measurement. The elements on larger scale which show the edge part of the wire cable hold | maintained at the support | pillar of the bridge. The figure which shows the edge part of a wire cable. The cross-sectional view of the wire cable which shows typically an example of the aspect of the optical fiber sensor integrated in the strand of the wire cable. The longitudinal cross-sectional view which looked at the assembly state of the optical fiber sensor shown in FIG. 5 from the side of the strand. FIG. 6 is a cross-sectional view of a wire cable schematically showing a state in which an optical fiber sensor is incorporated in a mode different from FIG. 5. The longitudinal cross-sectional view which looked at the assembly state of the optical fiber sensor shown in FIG. 7 from the side of the strand. Explanatory drawing which shows the principle of a FBG type optical fiber sensor. Explanatory drawing which shows the image of the shift of the peak of a frequency in a BOTDR type | formula fiber sensor. The graph which shows the linearity of distortion and the amount of frequency changes. Explanatory drawing which shows the image of spectrum distribution and distance distribution in a BOTDR type fiber sensor. The figure which simplifies and shows the structure of a SOFO type | formula optical fiber sensor. The block diagram which shows an example of a SOFO system. Explanatory drawing which shows the aspect of refraction of light. Illustration showing the concept of optical fiber bending loss The perspective view of the vicinity of the end socket concerning one Embodiment at the time of making an optical fiber sensor adhere to the outer surface of a wire cable. FIG. 18 is a perspective view of the vicinity of an end socket according to an embodiment in which optical fiber sensors are arranged in a different manner from FIG. 17. The expanded sectional view of a notch part. The figure which shows the aspect which stuck the optical fiber sensor to the outer surface of the wire cable with the clamp. The figure which shows the aspect which stuck the optical fiber sensor to the outer surface of the wire cable by taping.

Explanation of symbols

2 .... Optical fiber cable 3,50 ... Optical fiber sensor 4 .... Diffraction grating 40 ... Grating 6 .... Optical part 7 .... Computer 10 ... Bridge 13 ... Wire cable 23 ... Wire 25 ... Insertion hole

Claims (4)

A wire cable formed by twisting together a plurality of strands,
The strain detection means for detecting the strain in the axial direction of the wire cable is incorporated in the wire cable,
The strain detection means is an optical fiber sensor comprising an optical fiber,
This optical fiber sensor is incorporated in the wire cable so as to be deformed as the wire cable expands and contracts, and the deformation of the optical fiber sensor detects a change in frequency of incident light, or reflection, refraction, or interference of light. A wire cable characterized by that.   An insertion hole formed along the axial direction is formed in one of the strands, and the optical fiber sensor is inserted into the insertion hole, and the axial direction expands and contracts with expansion and contraction of the strands. The wire cable according to claim 1. A tension measuring system that supports members constituting a structure in a fixed posture and measures the tension of a wire cable formed by twisting together a plurality of strands,
A strain detector that is incorporated in the wire cable and detects strain of the wire cable;
A tension calculating means for calculating a tension acting on the wire cable based on the detection of the strain detecting means;
Signal communication means for transmitting detection of the strain detection means from the strain detection means to the tension calculation means,
The signal communication means is an optical fiber cable;
The strain detection means is an optical fiber sensor formed using a part of an optical fiber cable,
This optical fiber sensor is incorporated in the wire cable so as to be deformed as the wire cable expands and contracts, and the deformation of the optical fiber sensor changes the frequency of light incident on the optical fiber sensor, or reflects, refracts or refractions the light. Detect the interference,
The tension measurement system characterized in that the tension calculation means calculates the tension of the wire cable based on the detection content of the optical fiber sensor. In measuring the tension of a wire cable formed by supporting a member constituting a structure in a fixed posture and twisting a plurality of strands together,
An optical fiber sensor formed using a part of the optical fiber cable is incorporated into the wire cable,
As the wire cable expands and contracts, the optical fiber sensor is deformed, and a change in the frequency of light incident on the optical fiber sensor, or a reflection, refraction, or interference of the light that occurs along with the deformation is detected.
A tension measuring method, comprising: calculating a tension of the wire cable by a tension calculating unit based on a change in a detected frequency of light or reflection, refraction, or interference of light.

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