KR100756056B1 - Fiber optic composite stranded wire. Manufacturing method and strain measurement method of optical fiber composite strand - Google Patents

Abstract

An optical fiber composite wire strand, a manufacturing method thereof, and a strain measuring method are provided to prevent a fiber bragg grating sensor from being damaged by external shock, by disposing the fiber bragg grating sensor in a through-hole of a first steel wire, thereby exactly measuring the strain rate. In an optical fiber composite wire strand(20), a through-hole(211) is formed on at least one of first and second steel wires(21,22) of the wire strand in a longitudinal direction of the steel wire. The first steel wire is positioned in the center. Six strands of the second steel wires are twisted with surrounding the first steel wire. An optical fiber sensor is disposed in the through-hole. In particular, a fiber bragg grating sensor(10) having grating sensing units arranged on an optical fiber at regular intervals is used.

Description

Fiber optic composite stranded wire. Optical Fiber embeded Wire Strand, Production method of Julia and Strain Measurement Method for

1 is a conceptual diagram for explaining the principle of OTDR which is a kind of light intensity sensor.

2 is a conceptual diagram for explaining the principle of the Mach-Zehnder interference type optical fiber sensor.

3 is a conceptual diagram for explaining the principle of the Michelson interference type optical fiber sensor.

4 is a conceptual diagram for explaining the principle of an optical fiber Bragg grating sensor.

5 is a perspective view of an optical fiber composite strand in accordance with an embodiment of the present invention.

FIG. 6 is a cross sectional view taken along the line VI-VI shown in FIG. 5; FIG.

7A to 7D are views for explaining a method for manufacturing the optical fiber composite strand according to one embodiment of the present invention.

** Explanation of symbols for the main parts of the drawing **

10 fiber optic grating sensor 11 grating detection unit

20: stranded wire 21: the first steel wire

22: second steel wire 211: through hole

The present invention, the optical fiber composite stranded wire. The present invention relates to a method for manufacturing a stranded wire and a strain measurement method using the optical fiber composite strand. More specifically, a through hole is formed in the strand and the fiber Bragg grating sensor is embedded in the through hole to protect the fiber Bragg grating sensor and at the same time. An optical fiber composite strand that can provide efficient and accurate measurement of the strain of a structure and provide short and long term measurement data to estimate the degree of damage and deterioration of the structure. A method for manufacturing the optical fiber composite strand and a strain measuring method.

Most of the purpose of the construction of the infrastructure is to pursue convenience and comfort in human life, and when designing or constructing such facilities, functionality and safety become important factors. However, most structures gradually lose their function and performance due to the constant change of load conditions and deterioration of structural members during the service life, and even cause large collapse accidents that threaten human life and property rights. Structures such as bridges, buildings, and dams, which are one of the important infrastructures, can be damaged due to unexpected environmental changes such as earthquakes, typhoons, and floods. Can be. In this situation, in recent years, a lot of short- and long-term measurement systems have been introduced to acquire basic data necessary for the determination of structural damage and deterioration or structural problems.

However, the electric resistance sensor system, which has been commonly used in the past, has difficulty in securing long-term durability due to the self-heating effect, and the cable length becomes longer when it is required to be installed in the tens and hundreds of kilometers such as a bridge. According to this or when the exposure to the electromagnetic wave includes a variety of noise in the measurement value has a disadvantage that the reliability of the measurement value is sharply lowered.

On the contrary, the optical fiber sensor is small in size, excellent in durability, easy to be inserted or integrated into the material, and because the main component is made of glass, it is resistant to corrosion and does not generate noise by electromagnetic waves. It has many advantages such as excellent construction ability because it can measure strain, and it has been spotlighted as an optimal next-generation sensor type that can replace the existing sensor in the trend of large-scale and large-scale construction of social infrastructure recently constructed. have.

In general, optical fiber sensors are classified into light intensity sensor, interference type optical fiber sensor, and fiber optic Bragg grating sensor according to the measurement method.

Optical Time Domain Reflectometry (OTDR), which is a representative type of the light intensity sensor, is characterized in that the optical loss increases depending on the extent to which the optical fiber is tensioned or bent due to external stimulus, cracks, etc. Due to this, when the optical fiber is cut, the reflected light appears on the cut surface. After injecting the pulsed light into the OTDR using this characteristic, it is possible to observe the change in the external physical quantity (strain, pressure, etc.) by measuring the optical loss according to the optical fiber length of the back scattered (back scattered) light. In addition, it is possible to know the cutting point by measuring the reflected light generated from the cutting plane, and by identifying the cutting point, it is possible to estimate the crack occurrence position of the structure. In FIG. 1, scattering or reflection occurs at a portion indicated by z1, z2, and z3, and the occurrence of scattering or reflection means that a change in physical quantity occurs at that portion. Therefore, it is possible to determine the location where the damage to the structure is estimated by identifying the location of the points z1, z2, z3, by analyzing the backscattered signal shown in the lower part of Figure 1 t1, t2 By measuring t3, the damaged area is estimated.

As shown in FIG. 2, the interference type optical fiber sensor having a higher sensitivity than the light intensity sensor includes a measurement optical fiber 1, a reference optical fiber 2, an interconnector 3, a light source 4, and a photodetector 5. It consists of. The output signal is measured by the photodetector 5, and the phase difference and magnitude of the signal detected by the photodetector 5 are related to external physical quantities (strain, temperature, pressure, etc.). Light and other conditions irradiated from the light source 4 act in the same way on the measurement optical fiber 1 and the reference optical fiber 2, and pass through the measurement optical fiber 1 on the basis of the physical quantity of light passing through the reference optical fiber 2. Since the physical quantity of light is corrected, the change of the physical quantity generated in the desired measurement optical fiber 1 is calculated | required, and it is excellent in accuracy. The most representative interference type sensors include the Mach-Zehnder interference type optical fiber sensor shown in FIG. 2 and the Michelson interference type optical fiber sensor shown in FIG. 3.

The optical fiber Bragg grating sensor transmits ultraviolet light (Excimer Laser) to the optical fiber and generates a plurality of grating detection units 11 in the optical fiber 10 as shown in FIG. 4. When l) is irradiated to the optical fiber 10, the wavelength component corresponding to the Bragg condition is reflected by the grating detection unit 11, and the remaining wavelength component is used as it passes. The reflected light and the light passed as it is can be measured by the photodetector 5 to measure changes in various physical quantities. The Bragg wavelength, which is the wavelength of the light reflected by the grating detector 11, is a function of the effective refractive index and the grating spacing. When the distance of the fiber grating detector 11 is changed by an external physical quantity such as temperature or load, the grating detector ( Since the Bragg wavelength, which is the wavelength of the light reflected by 11), is also changed, if the change in the Bragg wavelength is precisely measured, the unknown physical quantity (temperature, strain) applied to the optical fiber grating detector 11 may be calculated inversely.

However, as mentioned above, although the optical fiber sensor has various advantages, when the optical fiber sensor is directly attached to reinforcing bars or strands, the optical fiber sensor may be damaged not only the optical fiber but also the sensing unit by external stimulation. .

In order to protect the sensing part, when installing the optical fiber sensor in the reinforcing bar, make a groove in the part where the optical fiber is to be installed, insert the optical fiber sensor in the groove, grouting the remaining space, and then surface treatment or plastic for the protection of the sensor. After using a metal tube, there are cases where it is bonded to rebar or strand.

However, these methods are very cumbersome compared to the conventional method of attaching the electric resistance sensor, which not only acts as a detrimental factor in the widespread use of optical fiber sensors, but also requires very caution when installed in construction sites. .

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and the optical fiber composite stranded wire and the strain rate of the optical fiber composite stranded wire which can measure an effective strain while protecting the optical fiber sensor by embedding the optical fiber sensor in a part of the steel wire constituting the stranded wire Its purpose is to provide a measuring method and a manufacturing method.

In order to achieve the above object, the present invention,

The first steel wire or the second steel wire of the stranded wire including a first steel wire positioned at the center and six strands of second steel wires twisted around each other around the first steel wire and penetrate in the longitudinal direction of the steel wire. A ball is formed,

An optical fiber composite stranded wire is provided inside the through hole, wherein an optical fiber sensor is disposed.

The through hole is preferably formed in the first steel wire.

Preferably, the optical fiber sensor is an optical fiber Bragg grating sensor having a lattice detection unit formed at a predetermined interval on the optical fiber.

It is preferable that epoxy is filled in the said through-hole.

According to another aspect of the present invention,

Forming through-holes in the longitudinal direction of the steel wire in one steel wire constituting the stranded wire;

Manufacturing a stranded wire by arranging the steel wire in which the through hole is formed, in any one of a first steel wire in a central portion or six second steel wires surrounding the first steel wire; And

Inserting an optical fiber sensor in the through hole; provides a method for manufacturing an optical fiber composite strand.

It is preferable to arrange the stranded wire in which the through hole is formed in the first steel wire.

Preferably, the optical fiber is an optical fiber Bragg grating sensor in which a grating detection unit is formed at a predetermined interval on the optical fiber.

Insertion of the optical fiber Bragg grating sensor,

Inserting an intermediate member into one end of the through hole;

Vacuum sucking the other end of the through hole to expose the intermediate member to the outside of the other end of the through hole;

Connecting the optical fiber Bragg grating sensor to the intermediate member exposed at the other end;

And removing the intermediate member from the through hole at one end of the through hole and simultaneously inserting the optical fiber Bragg grating sensor into the through hole.

After the insertion stage of the fiber Bragg grating sensor

Filling the through-holes and curing the epoxy; preferably further comprises.

According to another aspect of the present invention,

The first steel wire or the second steel wire of the stranded wire including a first steel wire positioned at the center and six strands of second steel wires twisted around each other around the first steel wire and penetrate in the longitudinal direction of the steel wire. A strand preparation step of preparing a strand formed with a ball;

Preparing an optical fiber composite strand wire by inserting an optical fiber sensor into the through hole of the strand wire to prepare an optical fiber composite strand wire;

A construction step of constructing a structure using the stranded wire as a structural material;

A light irradiation step of irradiating light onto the optical fiber sensor of the strand; And,

It provides a strain measuring method of the optical fiber composite strand, including the step of measuring the strain of the strand by detecting the light passing through the optical fiber sensor.

The through hole is preferably formed in the first steel wire.

The optical fiber sensor is an optical fiber Bragg grating sensor formed with a grid sensing unit at a predetermined interval on the optical fiber,

The measuring step may be performed by detecting light reflected by a grating detector in the optical fiber Bragg grating sensor and light passing through the grating detector.

After the insertion stage of the fiber Bragg grating sensor

Filling the through-holes and curing the epoxy; preferably further comprises.

Hereinafter, with reference to the drawings will be described in detail with respect to the optical fiber composite strand in accordance with an embodiment of the present invention.

5 is a perspective view of an optical fiber composite strand according to an embodiment of the present invention, and FIG. 6 is a cross-sectional view of line VI-VI shown in FIG. 5.

The optical fiber composite stranded wire according to the present embodiment includes an optical fiber Bragg grating sensor 10 and a steel stranded wire 20.

As is well known, the strand wire 20 is twisted around the first steel wire 21 and the first steel wire 21 positioned in the center of the strand wire 20 and twisted together to be attached to the first steel wire 21. Six strands of the second steel wire 22 is included. The first steel wire 21 is also referred to as a "king cable", and is not formed twisted like the second steel wire 22 is formed straight in the longitudinal direction of the strand wire (20). That is, the strand 20 is formed by twisting six strands of the second strand 22 around each of the first steel wire 21 extending straight.

Through-holes 211 are formed in the first steel wire 21 in the longitudinal direction thereof.

The optical fiber Bragg grating sensor 10 is formed in the optical fiber grating detection unit 11 at a predetermined interval, and since it has been described in detail in the description of the prior art, further description of the configuration is omitted. The optical fiber Bragg grating sensor 10 is disposed in the through hole 211 formed in the first steel wire 211.

The remaining space other than the space occupied by the optical fiber Bragg grating sensor 10 in the through hole 211 is filled with epoxy 212, which is a grouting material, to fix the optical fiber Bragg grating sensor 10.

When the optical fiber Bragg grating sensor 10 is disposed in the through hole 211 formed in the first steel wire 21, the optical fiber Bragg grating sensor 10 may be effectively prevented from being damaged by an external impact. In addition, since the first steel wire 21 is formed to be straight, the strain of the stranded wire 20 and the strain of the first steel wire 21 can be seen to be almost the same, which also has the advantage of enabling more accurate measurement of the strain.

At this time, since the through-hole 211 is formed in the first steel wire 21, the cross section is reduced, but the change in the value of the secondary moment (I) due to the cross-sectional change is negligible, which impedes the performance of the structure. I do not give it.

Hereinafter, with reference to the manufacturing method drawings of the optical fiber composite strand according to the above-described embodiment will be described in detail.

7A to 7D are diagrams for describing a method of manufacturing an optical fiber composite strand according to an embodiment of the present invention.

In order to manufacture the above-mentioned optical fiber composite stranded wire, first, through holes in the longitudinal direction are formed in any one of the steel wires constituting the stranded wire 20. The strand 20 includes a first steel wire 21 disposed in the center and six strands of the second steel wire 22 surrounding each other while twisting the outer circumferential surface of the first steel wire 21. Through holes 211 are formed in the first steel wire 21. There may be a variety of methods for forming the through-holes in the steel wire, but in the present embodiment is by drawing. Pull-out molding is a continuous process for producing products with a constant cross-section in the longitudinal direction, such as rods, beams, channels, and tubes. Even in the case of steel wires having through holes, the cross-section in the longitudinal direction is constant, and thus can be manufactured by pull-molding. It is the method of manufacturing the steel wire which has the most through hole most efficiently.

When the through holes 211 are formed in the first steel wire 21, the strand wire 20 is manufactured using the first steel wire 21 as a material.

When the manufacture of the strand 20 is finished, the optical fiber Bragg grating sensor 10 is inserted into the through hole 211.

After arranging the second steel wires 22 around the first steel wire 21 to twist each other in the manufacturing process of the strand 20, the ultrasonic heat treatment is performed while heating to about 400 degrees or more to prevent relaxation. Since the grating sensor 10 is heated to 200 degrees or more, damage due to heat occurs, and thus the grating sensor 10 cannot function properly. Therefore, the grating sensor 10 is inserted after the manufacture of the strand.

In order to insert the optical fiber Bragg grating sensor 10 into the through hole 211, it is preferable to use the intermediate member 30. As shown in FIG. 7A, the intermediate member 30 is made of a flexible linear material like a thread, and at one end thereof, a head 31 having a diameter of about 90% of the diameter of the through hole 211 is provided. .

The head 31 is inserted into one end of the through hole 211, and the head 31 is vacuum sucked by using the vacuum pump 32 on the other end side of the through hole 211. ) Is exposed to the other end side of the through hole 211.

When the head 31 is exposed, as shown in FIG. 7B, one end of the optical fiber Bragg grating sensor 10 is connected to the head 31, and the intermediate member 30 is disposed at one end of the through hole 211. At the same time, the intermediate member 30 is removed from the through hole, and the optical fiber Bragg grating sensor 10 is inserted into the through hole 211.

In the case where the length of the strand 20 is short, the optical fiber Bragg grating sensor 10 may be inserted into the through hole 211 without using the intermediate member 30. However, in some structures, a strand of more than 30 meters may be used. When such a long strand 20 is used as a structural member of the structure, it is advantageous to use an intermediate member. On the other hand, a method of directly sucking the optical fiber Bragg grating sensor 10 by using the vacuum pump 32 can be considered, but when the optical fiber Bragg grating sensor 10 is directly sucked by the vacuum pump 32 at a very high speed. Since damage may occur in the process because it moves, it is more effective to insert the optical fiber Bragg grating sensor 10 into the through hole 211 using the intermediate member 30.

When the optical fiber Bragg grating sensor 10 is inserted into the through hole 211, it is necessary to fix the optical fiber Bragg grating sensor 10 by filling a grouting material in the inside of the through hole 211. To this end, as shown in FIG. 7D, the other end of the through hole 211 is vacuum sucked using the vacuum pump 32 while one end of the through hole 211 is immersed in the epoxy storage container 33. 211) After filling the space other than the optical fiber grating Bragg sensor 10 inside with epoxy 212, the epoxy 211 is cured after a predetermined time, and the optical fiber grating Bragg sensor is cured by curing the epoxy 212. 10 is fixed to the strand 20.

When the optical fiber grating Bragg sensor 10 is fixed to the strand 20 by the epoxy 212, the manufacturing of the optical fiber composite strand is finished, by using it as a structural material it is possible to measure the strain in the long term.

Hereinafter, an embodiment of a method of measuring strain of an optical fiber composite strand using an optical fiber composite strand according to the above-described embodiment will be described.

First, the strand wire 20 having the through hole 211 is formed in the first steel wire 21 positioned in the center of the strand wire.

When the strand 20 is provided, the structure is constructed using the strand 20 as a structural material. The structure using the strand 20 as a structural material includes a prestressed concrete bridge or earth anchor, etc., and can be applied to many other structures.

After constructing the structure using the strand wire 20, the optical fiber grating Bragg sensor 10 is inserted into the through hole 211 formed in the first steel wire 21 of the strand wire 20. Insertion of the optical fiber grating Bragg sensor 10 may be used as described in the manufacturing method of the optical fiber composite strand.

When the optical fiber grating Bragg sensor 10 is inserted into the through hole 211, the internal space of the through hole 211 is filled with epoxy 212 and cured. In this case, the method described in the manufacturing method of the optical fiber composite strand may be used as it is. Can be.

After filling the space in the through hole 211 with an epoxy 212 and curing, the strain is measured after the optical fiber grating Bragg sensor 10 is fixed to the strand 20.

In order to measure the strain, the strain of the strand 20 is irradiated by irradiating light into the optical fiber grating Bragg sensor 10 and detecting and analyzing the light reflected by the grating detector 11 and the light passing through the grating detector 11. To measure.

The strain measurement of the strand 20 is performed immediately after construction and continuously performed at regular intervals to observe the change in strain. By using the stress-strain relationship, the stress change of the strand is observed. Abnormalities due to deterioration of the structure can also be identified.

In this embodiment, after constructing the structure using the strand 20 having the through hole 211, the optical fiber grating Bragg sensor 10 was inserted and the epoxy 212 was charged, but the optical fiber grating Bragg sensor 10 was used. After inserting into the through hole 211 and filling up the epoxy 212, the structure may be constructed using the strand 20.

In this embodiment, an embodiment in which the optical fiber Bragg grating sensor is used as the optical fiber sensor has been described. The fiber Bragg grating sensor is not necessarily to be used, and may be replaced by another type of optical fiber sensor, and the implementation by such a replacement should not be considered to be inconsistent with the technical spirit of the present invention.

Although the preferred embodiments of the present invention have been described above, the technical spirit of the present invention is not limited to the described embodiments, and various types of optical fiber composite stranded wires and optical fibers thereof without departing from the technical spirit of the present invention. It will be apparent to those skilled in the art that the present invention can be embodied as a method for manufacturing a composite strand and a strain measuring method.

As described above, according to the present invention, a method of manufacturing a fiber composite stranded wire and a method of measuring a strained fiber composite stranded wire which can measure an effective strain by embedding an optical fiber sensor in a portion of the steel wire constituting the stranded wire and at the same time can efficiently measure the strain. Can be provided.

Claims (13)

The first steel wire or the second steel wire of the stranded wire including a first steel wire positioned at the center and six strands of second steel wires twisted around each other around the first steel wire and penetrate in the longitudinal direction of the steel wire. A ball is formed, An optical fiber composite stranded wire, wherein an optical fiber sensor is disposed inside the through hole. The method of claim 1, And the through hole is formed in the first steel wire. The method of claim 2, The optical fiber sensor is an optical fiber composite strand, characterized in that the optical fiber Bragg grating sensor is formed in the optical fiber at a predetermined interval. The method of claim 1, The optical fiber composite stranded wire, wherein the through hole is filled with epoxy. Forming through-holes in the longitudinal direction of the steel wire in one steel wire constituting the stranded wire; Manufacturing a stranded wire by arranging the steel wire in which the through hole is formed, in any one of a first steel wire in a central portion or six second steel wires surrounding the first steel wire; And And inserting an optical fiber sensor into the through hole. The method of claim 5, The method of manufacturing an optical fiber composite stranded wire, characterized in that the stranded wire formed with the through hole is disposed in the first steel wire. The method of claim 6, The optical fiber is a manufacturing method of the optical fiber composite stranded wire, characterized in that the optical fiber Bragg grating sensor is formed at a predetermined interval on the optical fiber. The method of claim 7, wherein Insertion of the optical fiber Bragg grating sensor, Inserting an intermediate member into one end of the through hole; Vacuum sucking the other end of the through hole to expose the intermediate member to the outside of the other end of the through hole; Connecting the optical fiber Bragg grating sensor to the intermediate member exposed at the other end; Pulling the intermediate member at one end of the through hole to remove the intermediate member from the through hole and simultaneously inserting the optical fiber Bragg grating sensor into the through hole. Manufacturing method. The method of claim 5, After the insertion stage of the fiber Bragg grating sensor Filling and curing the epoxy through the through-hole; The method of manufacturing an optical fiber composite strand. The first steel wire or the second steel wire of the stranded wire including a first steel wire positioned at the center and six strands of second steel wires twisted around each other around the first steel wire and penetrate in the longitudinal direction of the steel wire. A strand preparation step of preparing a strand formed with a ball; Preparing an optical fiber composite strand wire by inserting an optical fiber sensor into the through hole of the strand wire to prepare an optical fiber composite strand wire; A construction step of constructing a structure using the stranded wire as a structural material; A light irradiation step of irradiating light onto the optical fiber sensor of the strand; And, And measuring a strain of the stranded wire by detecting the light passing through the optical fiber sensor. The method of claim 10, The through-hole is formed in the first steel wire strain measurement method of the optical fiber composite strand. The method of claim 11, The optical fiber sensor is an optical fiber Bragg grating sensor formed with a grid sensing unit at a predetermined interval on the optical fiber, The measuring step is a strain measurement method of the optical fiber composite strand, characterized in that for detecting the light reflected by the grating detection unit in the optical fiber Bragg grating sensor and the light passing through the grating detection unit. The method of claim 10, After the insertion stage of the fiber Bragg grating sensor Filling the through-holes and curing the epoxy; Strain measurement method of the optical fiber composite strand further comprising a.

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