KR102323526B1 - Prestressing force monitoring system of prestressins strand using smart anchoring plate based on distributed optical fiber sensor, and method for the same - Google Patents

Abstract

By forming a groove on the outer circumferential surface of the smart fixing plate installed between the prestressed concrete (PSC) member and the fixing head and easily attaching an optical fiber sensor having a gentle curvature, it is possible to ensure the consistency of the strain measurement direction of the PS stranded wire. , In addition, using the fact that the optical signal (Brillouin frequency or FBG wavelength) change measured through distributed optical fiber sensing based on Brillouin scattering or fiber Bragg grating (FBG) has a linear relationship with the strain according to tension, PS strands A system and method for monitoring the tension of a prestressed strand using a distributed optical fiber sensor-based smart anchoring plate, which can monitor and manage the tension during the life cycle of a PSC structure by estimating the tension of the PSC structure, are provided.

Description

Prestressing tension monitoring system and method of prestressed strand using distributed optical fiber sensor-based smart fixing plate

The present invention relates to a distributed optical fiber sensor-based smart anchoring plate, and more specifically, distributed to monitor the tension of a PS strand installed in a PSC structure such as a Pre-Stressed Concrete (PSC) bridge. It relates to a tension monitoring system for a PC strand using a type optical fiber sensor-based smart fixing plate and a method therefor.

In general, a PSC structure has a structure in which the deflection and cracking properties of a concrete structure are efficiently improved by using individual steel wires and tendons, and the core element of such a PSC structure is a tendon that provides tension (compressive force) to the PSC member. As a PS strand.

A typical PSC structure loses tension due to various causes over time, and this loss greatly affects the performance of the PSC structure, and in the worst case, it may cause a collapse accident. Therefore, efficient monitoring of the tension applied to these PSC structures is required.

As a method of measuring the tendon tension of a PSC structure according to the prior art, 1) a tension monitoring method using a strain gauge-based load cell, 2) a vibration method using vibration characteristics according to the tension force, 3) a strand including a sensor capable of measuring tendon strain There is a method of monitoring tension force using , and 4) a method of measuring magnetic field change according to tension force, such as EM (Electro-Magnetic) or MFL (Magnetic Flux Leakage) sensors.

Specifically, Figure 1 is a view showing a PSC member for measuring the tension force using a load cell according to the prior art.

A strain gauge-based tension monitoring method using a load cell according to the prior art, as shown in FIG. 1, installs the load cell 5 between the PSC member 2 and the fixing head 4, and uses the sheath Measure the tension of the PS strand (1) in the tube (3). At this time, since calibration of the load cell 5 is difficult, there is a problem in that it is difficult to use for a long period of time.

In addition, in the case of the vibration method using the vibration characteristic according to the tension force according to the related art, the tension force is measured after measuring the vibration characteristic of the tendon using an acceleration sensor or the like. However, in the case of the vibration method using the vibration characteristics according to the tension force, it can be applied only to the external tendon, and there is a problem in that it lacks accuracy due to the boundary condition of both ends of the tendon and the uncertainty of the mass. In other words, it lacks practical applicability because it is a method that does not consider actual field conditions.

In addition, FIG. 2 is a view showing that an optical fiber sensor is embedded in a steel core wire for measuring tension according to the related art.

As shown in FIG. 2, the method for monitoring tension using a strand (smart strand) including a sensor capable of measuring tendon strain, such as a fiber optic grating sensor according to the prior art, is a method of monitoring a tension force using a core wire in the lateral line (1a) of the strand as an optical fiber sensor. (6) Measure the tension force using the smart strand replaced by the embedded FRP core wire (1b). At this time, since it is a method of calculating the tension applied to the individual strands, the tension of the individual strands may be different depending on the method of tensioning the strands. Accordingly, when estimating the total tension force based on the tension force calculated from individual strands, there is a problem that accuracy may be lacking, and also, there is a problem in that it is difficult to replace the corresponding strand when damage occurs in the smart strand.

In addition, Figure 3 is a view showing the measurement of the tension force using the EM sensor according to the prior art.

In the case of magnetic field change measurement method according to tension force, such as EM (Electro-Magnetic) or MFL (Magnetic Flux Leakage) sensor according to the prior art. It is a method of estimating the tension force by calculating the relational expression between the magnitude of the tension force and the rate of change of the magnetic field in advance. However, in the case of such an EM sensor, as shown in a) and b) of FIG. 3, it is difficult to use for a bundled strand due to its bulkiness, and accuracy may be a problem when reinforcing bars or the like are around, and also , there is a problem that the accuracy of the initial measurement may be lacking due to demagnetization over time.

On the other hand, as a prior art, Korean Patent Registration No. 10-1408954 discloses an invention entitled "a strain sensing device for a structural strand and a sensing system having the same", which will be described with reference to FIGS. 4A and 4B.

4A and 4B are diagrams showing an exploded perspective view of a strain sensing device for a stranded structure and an anchor head of the strain sensing device according to the related art, respectively.

As shown in FIG. 4A, the strain sensing device of the stranded structure according to the related art is mounted on the outer surface of the strand installed in the structure to measure and manage the tension of the strand 1 in real time. As an apparatus, it is configured to include a first outer cylinder 10 , a second outer cylinder 20 , a tubule 30 , an optical fiber 40 having a strain sensor, and an optical fiber fixing means 50 .

The first outer cylinder 10 is mounted at one point of the strand, and the second outer cylinder 20 is mounted at another point of the strand to be spaced apart from the first outer cylinder 10, in this case, the first outer cylinder 10 and the second Each of the outer cylinders 20 is configured to include a cylindrical body 11 , a guide hole 19 formed in the body 11 , a strand mounting hole 17 , and a fastening hole 13 . Specifically, the body 11 is a hollow cylindrical member made of steel such as metal, and a guide hole 19 connected to the tubule 30 and a strand mounting hole 17 into which the strand 1 is inserted are formed, A fastening hole 13 for fixing the body 11 to the strand is formed through the side surface.

At least one tube 30 is an inner hollow tube, and one end is connected to the first outer tube 10 , and the other end is connected to the second outer tube 20 .

The optical fiber 40 passes through the first outer tube 10 , the tubule 30 , and the second outer tube 20 , and a Bragg grating sensor is formed in the optical fiber 40 .

As shown in Fig. 4b, the anchor head 60 corresponds to a component for installing the strand 1 in the structure, and fixing each strand 1 pulled out after curing the cement mortar. The anchor head 60 is provided with a plurality of anchorages 62 into which the externally drawn strand 1 is fitted. In particular, the optical fiber 40 extending from the strain sensing device installed on the strand is drawn out of the cement mortar. An optical fiber lead-out hole 61 is formed together so that it can be used.

In the case of a strain sensing device of a stranded structure according to the prior art, since it is based on an optical fiber strain sensor, the measurement sensitivity is very excellent, and it is possible to simultaneously monitor and measure the tension at multiple points in real time. In addition, since it can be installed in a simple mounting method on the existing stranded wire, there is no need to make a separate order according to the structure, it can prevent damage caused by external stimuli of the optical fiber sensor, and it can be attached separately from the stranded wire. It is easy to cut, pre-treat and finish the stranded wire.

However, in the case of the strain sensing device of a stranded structure according to the prior art, the first outer cylinder 10 , the second outer cylinder 20 , the tubule 30 , the optical fiber 40 having the strain sensor and the optical fiber fixing means 50 ), and the structure is complicated, and there is a problem in that it is not easy to install.

Republic of Korea Patent No. 10-1408954 (Registration Date: June 11, 2014), Title of Invention: "Strain sensing device for structural strands and sensing system having the same" Republic of Korea Patent No. 10-1326859 (Registration Date: November 1, 2013), Title of Invention: "Induced Brillouin Scattering Based Fiber Optic Sensor Device Using Optical Frequency Modulation" Republic of Korea Patent No. 10-1182650 (Registration Date: September 7, 2012), Title of Invention: "Sensing Method Using Distributed Fiber Optic Sensor and Brillouin Scattering" Republic of Korea Patent No. 10-968533 (Registration Date: June 30, 2010), Title of Invention: "Stranded Wire with Optical Fiber Sensor" Republic of Korea Patent Publication No. 2019-107583 (published on September 20, 2019), title of invention: "Smart concrete composition and smart concrete anchorage system for monitoring tension loss" Republic of Korea Patent Publication No. 2010-26145 (published date: March 10, 2010), title of invention: "Method for measuring tension or strain using an optical fiber Bragg grating sensor"

The technical problem to be achieved by the present invention for solving the above problems is to form a groove on the outer peripheral surface of a smart fixing plate installed between a PSC member and a fixing head, and easily attach an optical fiber sensor having a gentle curvature, PS An object of the present invention is to provide a system and method for monitoring the tension of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate, which can ensure the consistency of the strain measurement direction of the strand.

Another technical problem to be achieved by the present invention is that the change in the optical signal (Brillouin frequency or FBG wavelength) measured through distributed optical fiber sensing based on Brillouin scattering or fiber Bragg grating (FBG) is linearly related to strain according to tension. By estimating the tension of the PS strand using that with it is to do

As a means for achieving the above-mentioned technical problem, the system for monitoring the tension of the prestressed strand using the distributed optical fiber sensor-based smart fixing plate according to the present invention is a system for monitoring the tension of the PS strand installed in the PSC structure, the outer peripheral surface A smart fixing plate in which a groove is formed and installed between the PSC member and the fixing head of the PSC structure to fix the PC strand; an optical fiber sensor attached along the groove formed on the outer peripheral surface of the smart fixing plate to measure the tension force introduced into the PC strand; a distributed optical fiber sensor interrogator connected to the optical fiber sensor to measure a Brillouin frequency or FBG wavelength, which is an optical signal in a longitudinal direction of the optical fiber; a linear relational expression deriving unit for experimentally deriving a linear relational expression between the tension force and the optical signal; an optical signal-tensile force inversion unit for inverting the optical signal measured by the distributed optical fiber sensor interrogator into a tension force according to the linear relational expression; and a tension monitoring unit for monitoring the change in tension of the PSC member, wherein the smart fixing plate measures the distribution of strain generated in the PC strand through an optical fiber sensor attached to the outer peripheral surface based on a distributed optical fiber sensor, the The smart fixing plate is manufactured in a hollow cylindrical shape corresponding to the size of the anchorage of the PSC member of the PSC structure, and a groove is formed on the outer peripheral surface of the smart fixing plate.

delete

Here, it is preferable that the groove of the smart fixing plate is formed to a depth of 0.3 mm substantially equal to the thickness of the optical fiber sensor by CNC precision machining.

Here, the groove may be created to have a predetermined gentle curvature along the outer peripheral surface of the smart fixing plate, and the optical fiber sensor may be attached thereto.

Here, the groove is formed in the center of the outer peripheral surface of the smart fixing plate, so that the optical fiber sensor can be wound horizontally several times.

Here, the optical fiber sensor may be attached with a CN (Cyanoacrylate) adhesive along the groove of the smart fixing plate.

Here, the outer peripheral surface of the smart fixing plate to which the optical fiber sensor is attached is preferably coated to protect the optical fiber sensor.

Here, the distributed optical fiber sensor interrogator is a Brillouin Optical Correlation Domain Analysis (BOCDA) interrogator that measures Brillouin frequency or an FBG-based quasi-distributed resonance frequency mapping interrogator that measures FBG wavelength. can be

Here, the BOCDA interrogator may be connected to lead wires drawn out from both ends of the optical fiber sensor to measure the Brillouin frequency from the optical fiber sensor in response to the tension force introduced to the PC strand.

Here, the FBG-based quasi-distributed resonant frequency mapping interrogator (RFMI) is connected to a lead wire drawn out from one end of the optical fiber sensor using the reflected wave of the FBG, and in response to the tension force introduced into the PC strand, the optical fiber sensor FBG reflected wave can be measured from

Here, after experimentally measuring the Brillouin frequency or FBG wavelength according to the tension force using a UTM (universal material testing machine) of the PC strand to which the optical fiber sensor is attached through a distributed optical fiber sensor interrogator, the measured data It is characterized in that the linear relational expression of the optical signal-tensile force is derived in advance.

로 주어지고, 여기서,

는 브릴루앙 주파수 또는 FBG 파장을 나타내며,

및

는 UTM(만능재료시험기)을 활용한 선형관계식 도출 과정에서 산출할 수 있고, 상기 긴장력은 상기 계측된 브릴루앙 주파수 또는 FBG 파장으로부터 역산되는 것을 특징으로 한다.Here, the linear relation is

is given, where,

represents the Brillouin frequency or FBG wavelength,

and

can be calculated in the process of deriving a linear relation using UTM (Universal Material Testing Machine), and the tension force is inversely calculated from the measured Brillouin frequency or FBG wavelength.

On the other hand, as another means for achieving the above-mentioned technical problem, the method of monitoring the tension of the prestressed strand using the distributed optical fiber sensor-based smart fixing plate according to the present invention is a method of monitoring the tension of the PS strand installed in the PSC structure. In, a) attaching the optical fiber sensor along the groove formed on the outer peripheral surface of the smart fixing plate; b) installing the smart fixing plate to which the optical fiber sensor is attached between the PSC member and the fixing head; c) introducing a tension force to the PC strand installed on the PSC member using a tension force introduction device; d) measuring the optical signal from the optical fiber sensor attached to the smart fixing plate using a distributed optical fiber sensor interrogator; e) inversely calculating the measured optical signal as a tension force using a pre-calculated linear relationship between the optical signal and the tension force; and f) monitoring the change in tension of the PSC member while repeating steps d) and e) according to the tension monitoring plan of the PSC member, wherein the smart fixing plate includes an optical fiber sensor attached to the outer circumferential surface A distribution type optical fiber sensor-based measurement of the strain distribution occurring in the PC strand through the smart fixing plate is manufactured in a hollow cylindrical shape corresponding to the size of the anchorage of the PSC member of the PSC structure, but the outer circumferential surface of the smart fixing plate It is characterized in that the groove is formed.

According to the present invention, by forming a groove on the outer circumferential surface of the smart fixing plate installed between the PSC member and the fixing head and easily attaching an optical fiber sensor having a gentle curvature, it is possible to ensure the consistency of the direction of measuring the strain of the PS strand. have.

According to the present invention, using the fact that the optical signal (Brillouin frequency or FBG wavelength) change measured through the Brillouin scattering-based or fiber Bragg grating (FBG)-based distributed optical sensing has a linear relationship with the strain according to the tension force. By estimating the tension of the PS strand, it is possible to monitor and manage the tension during the life cycle of the PSC structure.

1 is a view showing a PSC member for measuring the tension force using a load cell according to the prior art.
FIG. 2 is a view showing that an optical fiber sensor is embedded in a steel core wire for measuring tension according to the related art.
3 is a view illustrating measuring the tension force using the EM sensor according to the prior art.
4A and 4B are views showing an exploded perspective view of a strain sensing device for a stranded structure and an anchor head of the strain sensing device according to the related art, respectively.
5 is a diagram for explaining the difference between a point (FBG) optical fiber sensor and a distributed optical fiber sensor.
6 is a diagram illustrating a tension monitoring system of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention.
7 is a view for explaining the tension monitoring of the fixing unit according to the strain-optical fiber sensor measurement signal relationship in the tension monitoring system of the prestressed strand using the distributed optical fiber sensor-based smart fixing plate according to the embodiment of the present invention.
8A and 8B show the derivation of a linear relationship between the Brillouin optical signal and the tension in the tension monitoring system of the prestressed strand using the BOCDA interrogator-based smart fixing plate, which is a type of distributed optical fiber sensor according to an embodiment of the present invention. It is a drawing for explanation.
9 is a view showing the Brillouin frequency change for each fiber length according to the change in the tension in the tension monitoring system of the prestressed strand using the distributed optical fiber sensor-based smart fixing plate according to the embodiment of the present invention.
10 is a diagram specifically illustrating a distributed optical fiber sensor-based smart fixing plate in a tension monitoring system of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention.
11 is an operation flowchart of a method for monitoring tension of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings so that those of ordinary skill in the art can easily implement them. However, the present invention may be embodied in many different forms and is not limited to the embodiments described herein. And in order to clearly explain the present invention in the drawings, parts irrelevant to the description are omitted, and similar reference numerals are attached to similar parts throughout the specification.

Throughout the specification, when a part "includes" a certain element, it means that other elements may be further included, rather than excluding other elements, unless otherwise stated. In addition, terms such as “…unit” described in the specification mean a unit that processes at least one function or operation, which may be implemented as hardware or software or a combination of hardware and software.

First, FIG. 5 is a diagram for explaining the difference between a point (FBG) optical fiber sensor and a distributed optical fiber sensor, and FIG. 5 a) shows a point optical fiber sensor using a fiber Bragg grating (FBG). , FIG. 5 b) shows a distributed optical fiber sensor using Brillouin scattering correlation domain analysis (BOCDA), respectively.

As shown in FIG. 5 a), the point optical fiber sensor using a fiber Bragg grating (FBG) indicates that measurement is possible at only several points on one optical fiber, and as shown in FIG. 5 b) , The distributed optical fiber sensor using Brillouin Scattering Correlation Area Analysis (BOCDA) indicates that measurements can be performed at multiple consecutive points on one optical fiber.

Specifically, as shown in FIG. 5 b), the optical fiber sensor based on Brillouin scattered light can continuously measure the distribution of strain and temperature in the entire section to which the optical fiber sensor is attached, and thus a large structure with a large size. It is known to be effectively used for monitoring of long-distance lines. At this time, the method of continuously measuring the strain occurring in the longitudinal direction of the optical fiber by using that the strain applied to the optical fiber and the Brillouin frequency change is a linear relationship is called Brillouin-based distributed optical fiber sensing. That is, distributed optical fiber sensing is a method of using the entire optical fiber as a strain sensor, and has the same effect as installing a large number of strain sensors in the longitudinal direction of the optical fiber sensor. This Brillouin scattering correlation area (BOCDA) analysis method is a distributed optical fiber sensing technique having a high spatial resolution of 5 cm, and can use a distributed optical fiber sensor interrogator.

The system for monitoring the tension of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention may use either a Brillouin scattering-based sensing technique or an FBG-based quasi-distributed sensing technique. Accordingly, the distributed optical fiber interrogator is, for example, a BOCDA interrogator using a Brillouin scattering-based sensing technique or a resonance frequency mapping interrogator using an FBG-based quasi-distributed sensing technique ( RFMI).

Hereinafter, as an embodiment of the present invention, the tension monitoring system of the prestressed strand using the smart fixing plate is described as using the distributed optical fiber sensor-based smart fixing plate shown in FIG. ), a fiber Bragg grating (FBG)-based smart fixing plate shown in Fig.

[Tension monitoring system of prestressed strands using distributed optical fiber sensor-based smart fixing plate]

6 is a diagram showing a tension monitoring system of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention, and FIG. 7 is a distributed optical fiber sensor-based smart fixing according to an embodiment of the present invention. It is a diagram to explain the tension monitoring of the anchorage according to the strain-optical fiber sensor measurement signal relationship in the tension monitoring system of the prestressed strand using a plate.

6 and 7, the system 100 for monitoring the tension of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention, the tension of the PS strand 230 installed in the PSC structure As a monitoring system, a smart fixing plate 110, an optical fiber sensor 120, a distributed optical fiber sensor interrogator 130, a linear relational expression derivation unit 140, an optical signal-tensile force inversion unit 150, and a tension monitoring unit (160).

The smart fixing plate 110 has a groove 111, for example, a spiral groove formed on the outer peripheral surface, and is installed between the PSC member 210 and the fixing head 240 of the PSC structure to fix the PC strand 230. At this time, the smart fixing plate 110 is manufactured in a hollow cylindrical shape corresponding to the size of the anchorage of the PSC member 210 of the PSC structure, and a groove 111 on the outer peripheral surface of the smart fixing plate 110, for example A spiral groove may be formed. In particular, the groove 111 of the smart fixing plate 110 is preferably formed to a depth of 0.3 mm substantially equal to the thickness of the optical fiber sensor 120 by CNC (Computer Numerical Control) precision processing. In addition, the groove 111 is formed to have a gentle curvature along the outer peripheral surface of the smart fixing plate 110, so that the optical fiber sensor 120 can be attached to have a gentle curvature. In addition, the groove 111 may be formed in the center of the outer peripheral surface of the smart fixing plate to wind the optical fiber sensor 120 horizontally several times.

The optical fiber sensor 120 is attached along the groove 111 formed on the outer peripheral surface of the smart fixing plate 110 to measure the tension force introduced into the PC strand 230 . In this case, the optical fiber sensor 120 may utilize a general inexpensive optical fiber, and may be attached with a CN (Cyanoacrylate) adhesive along the groove 111 of the smart fixing plate 110 . In addition, the outer peripheral surface of the smart fixing plate 110 to which the optical fiber sensor 120 is attached is preferably coated to protect the optical fiber sensor 120 .

The distributed optical fiber sensor interrogator 130 is connected to the optical fiber sensor 120 to measure the Brillouin frequency or FBG wavelength, which is an optical signal in the length direction of the optical fiber. Here, the distributed optical fiber sensor interrogator is a Brillouin Optical Correlation Domain Analysis (BOCDA) interrogator that measures Brillouin frequency or an FBG-based quasi-distributed resonance frequency mapping interrogator that measures FBG wavelength. can be For example. The distributed optical fiber sensor interrogator is connected to lead wires drawn out from both ends of the optical fiber sensor 120 to measure the Brillouin frequency from the optical fiber sensor in response to the tension force introduced to the PC strand 230 . In addition, the FBG-based quasi-distributed resonant frequency mapping interrogator (RFMI) is connected to a lead wire drawn out from one end of the optical fiber sensor 120 using the reflected wave of the FBG, and the tension force introduced into the PC strand 230 In response, it is possible to measure the FBG reflected wave from the optical fiber sensor 120 .

The linear relational expression deriving unit 140 experimentally derives a linear relational expression between the tension force and the optical signal. That is, the optical signal according to the tension force is experimentally measured through the distributed optical fiber sensor interrogator 130 using a UTM (universal material testing machine) for the PC strand 230 to which the optical fiber sensor 120 is attached, A linear relational expression of the optical signal-tension force is derived in advance through the measured data.

로 주어지고, 여기서,

는 브릴루앙 주파수 또는 FBG 파장을 나타내며,

및

는 UTM을 활용한 선형관계식 도출 과정에서 산출할 수 있고, 상기 긴장력은 상기 계측된 브릴루앙 주파수 또는 FBG 파장으로부터 역산될 수 있다.The optical signal-tensile force inversion unit 150 inversely calculates the optical signal measured by the distributed optical fiber sensor interrogator 130 as a tension force according to the linear relational expression. For example, the linear relation

is given, where,

represents the Brillouin frequency or FBG wavelength,

and

may be calculated in the process of deriving a linear relation using UTM, and the tension force may be inversely calculated from the measured Brillouin frequency or FBG wavelength.

The tension monitoring unit 160 monitors the change in tension of the PSC member 210 .

Accordingly, the smart fixing plate 110 can measure the strain distribution occurring in the PC strand 230 through the optical fiber sensor 120 attached to the outer peripheral surface of the distributed optical fiber sensor-based.

In other words, in the case of the prestressed strand tension monitoring system 100 using the distributed optical fiber sensor-based smart fixing plate according to the embodiment of the present invention, as shown in FIG. 6 , the fixing head 240 and the PSC member ( The smart fixing plate 110 is installed between 210).

At this time, as shown in FIG. 7 , the smart fixing plate 110 is compressed according to the tension applied to the PSC member 210 , and accordingly, the horizontal and vertical directions of the smart fixing plate 210 . Strain occurs in each direction. The strain generated at this time can be measured through the optical fiber sensor 120 wound around the smart fixing plate 210, and the measured strain can be inversely calculated as a tension force according to a linear relational expression.

Meanwhile, FIGS. 8A and 8B show a Brillouin optical signal in a tension monitoring system of a prestressed strand using a BOCDA interrogator-based smart fixing plate, which is a type of distributed optical fiber sensor according to an embodiment of the present invention. As a diagram for explaining the derivation, FIG. 8A shows that the smart fixing plate 110 is installed between the PSC member 210 and the fixing head 240, and FIG. 8B is a diagram showing that a linear relational expression is derived.

As shown in Figure 8a, when the smart fixing plate 110 is pressed by the tension (compressive force) acting on the fixing head 240, the smart fixing plate 110 is deformed in the circumferential direction. Thus, it is possible to calculate the tension (compression force) of the fixing head 240 . At this time, since the wedge for fixing the PC strand 230 is fixed to the fixing head 240 , the stress and strain distribution is very complicated, so it is easy to calculate the tension (compressive force) from the strain measurement value of the fixing head 240 don't In addition, as a means for measuring the strain of the smart fixing plate 110, an electrical resistance strain gauge can be used, but it is difficult to accurately install, and when a plurality of these electrical resistance strain gauges are installed, it is difficult to process the lead wire. it is not

In addition, the tension (compressive force) acting on the smart fixing plate 110 from the fixing head 240 may not be uniform and uneven due to various factors. In this case, since the size of the strain in the circumferential direction of the smart fixing plate 110 is also uneven, it is preferable to measure the strain at as many positions as possible. measure

Since the optical fiber sensor 120 has excellent durability and can measure strain at many positions with one fiber, in the embodiment of the present invention, the optical fiber sensor 120 is wound around the outer peripheral surface of the smart fixing plate 110 and the optical fiber sensor 120 ) can be measured to calculate the tension force (compressive force). In this case, it is apparent to those skilled in the art that the optical fiber sensor 120 may be a commonly used Fiber Bragg Grating (FBG) optical fiber sensor or a Brillouin scattering-based distributed optical fiber sensor.

On the other hand, as shown in FIG. 8B, the Brillouin frequency and the tension force applied to the anchorage have a linear relationship, and similarly, the FBG wavelength and the tension force applied to the anchorage have a linear relationship. This linear relational expression represents the relationship between the actual measurement data and the tension force, and the smart fixing plate 110 using the linear relational expression calculated in advance for the Brillouin frequency or the FBG wavelength measured by the distributed optical fiber sensor interrogator 130 . The tension applied to the can be inversely calculated.

Meanwhile, FIG. 9 is a view showing the Brillouin frequency change for each fiber length according to the change in tension in the tension monitoring system of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention.

In the case of the tension monitoring system 100 of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention, the optical fiber attached to the outer peripheral surface of the smart fixing plate 110 through a high spatial resolution of 5 cm The strain distribution generated through the sensor 120 can be measured, and FIG. 9 shows that the measured Brillouin frequency is linearly changed according to the tension force, and the FBG wavelength is linearly changed according to the tension force. This has the same effect as attaching tens or hundreds of strain gauges to the anchorage, and high measurement accuracy and reliability can be secured through multiple measurement points.

The optical fiber sensor 120 attached to the smart fixing plate 110 is not affected by noise by an external electromagnetic field, and has high durability because it uses an optical fiber made of silica, for example, as a stable sensor during the common life of the PSC bridge. can be utilized

On the other hand, FIG. 10 is a view specifically showing a distributed optical fiber sensor-based smart fixing plate in a tension monitoring system of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention, FIG. ) indicates that a groove is formed on the outer peripheral surface of the smart fixing plate, and b) of FIG. 10 indicates that an optical fiber sensor is inserted and attached to the groove.

The smart fixing plate 110 in the prestressed strand tension monitoring system 100 using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention can improve high workability and measurement reliability.

As shown in FIG. 10 a), the outer peripheral surface of the smart fixing plate 110 through CNC (Computer Numerical Control) precision processing so that a plurality of grooves 110 having a depth of 0.3 mm have a gentle curvature θ. to form in Through this, it is possible to easily attach the optical fiber sensor 120 and to ensure the consistency of the strain measurement direction.

In particular, the distributed optical fiber sensor 120 has a limitation in that it lacks measurement reliability as light loss occurs when a sudden change in curvature occurs. In order to solve this limitation, the smart fixing plate 110 according to an embodiment of the present invention is manufactured in a form as shown in FIG. 10 b). Through this, a predetermined gentle curvature θ can be maintained, and high measurement reliability can be secured.

In other words, the smart fixing plate 110 forms a groove 111 having a certain direction and angle through CNC precision processing, so that the optical fiber sensor 120 can be easily attached along the groove 111, It is possible to ensure the consistency of the strain measurement direction. In addition, measurement reliability can be secured by minimizing optical loss through a gentle curvature θ of the generated groove, for example, a gentle curvature change at an angle of 2° to 4°.

[Method for monitoring tension of prestressed strands using distributed optical fiber sensor-based smart fixing plate]

11 is an operation flowchart of a method for monitoring tension of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention.

Referring to FIG. 11 , the method for monitoring the tension of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention is a fiber optic sensor along the groove 111 formed on the outer peripheral surface of the smart fixing plate 110 . (120) is attached (S110). At this time, the smart fixing plate 110 is manufactured in a hollow cylindrical shape corresponding to the size of the anchorage of the PSC member 210 of the PSC structure, and a groove 111 is formed on the outer peripheral surface of the smart fixing plate 110 . In particular, the groove 111 of the smart fixing plate 110 is preferably formed to a depth of 0.3 mm substantially equal to the thickness of the optical fiber sensor 120 by CNC (Computer Numerical Control) precision processing. In addition, the groove 111 may be created to have a gentle curvature along the outer circumferential surface of the smart fixing plate 110 to attach the optical fiber sensor 120 . In addition, the groove 111 may be formed in the center of the outer peripheral surface of the smart fixing plate to wind the optical fiber sensor 120 horizontally several times.

Next, the smart fixing plate 110 to which the optical fiber sensor 120 is attached is installed between the PSC member 210 and the fixing head 240 (S120). In this case, the optical fiber sensor 120 may be attached with a CN (Cyanoacrylate) adhesive along the groove 111 of the smart fixing plate 110 . In addition, the outer peripheral surface of the smart fixing plate 110 to which the optical fiber sensor 120 is attached is preferably coated to protect the optical fiber sensor 120 .

Next, a tension force (compressive force) is introduced into the PC strand 230 installed in the PSC member 210 using a tension force introduction device (S130).

Next, the optical signal is measured from the optical fiber sensor 120 attached to the smart fixing plate 110 using the distributed optical fiber sensor interrogator 130 (S140). Here, the distributed optical fiber sensor interrogator is a Brillouin Optical Correlation Domain Analysis (BOCDA) interrogator that measures Brillouin frequency or an FBG-based quasi-distributed resonance frequency mapping interrogator that measures FBG wavelength. can be For example. The distributed optical fiber sensor interrogator is connected to lead wires drawn out from both ends of the optical fiber sensor 120 to measure the Brillouin frequency from the optical fiber sensor in response to the tension force introduced to the PC strand 230 . In addition, the FBG-based quasi-distributed resonant frequency mapping interrogator (RFMI) is connected to a lead wire drawn out from one end of the optical fiber sensor 120 using the reflected wave of the FBG, and the tension force introduced into the PC strand 230 In response, it is possible to measure the FBG reflected wave from the optical fiber sensor 120 .

Next, the measured Brillouin frequency is inversely calculated as the tension force using the pre-calculated linear relationship between the optical signal and the tension force (S150). At this time, after experimentally measuring the Brillouin frequency according to the tension force of the PC strand 230 to which the optical fiber sensor 120 is attached using a UTM (universal material testing machine) through the distributed optical fiber sensor interrogator 130 , a linear relational expression of optical signal-tension force is derived in advance through the measured data.

로 주어지고, 여기서,

는 브릴루앙 주파수 또는 FBG 파장을 나타내며,

및

는 UTM을 활용한 선형관계식 도출 과정에서 산출할 수 있고, 상기 긴장력은 상기 계측된 브릴루앙 주파수 또는 FBG 파장으로부터 역산될 수 있다.At this time, the Brillouin frequency or FBG wavelength measured by the distributed optical fiber sensor interrogator 130 is inversely calculated as a tension force according to the linear relational expression. For example, the linear relation is

is given, where,

represents the Brillouin frequency or FBG wavelength,

and

can be calculated in the process of deriving a linear relation using UTM, and the tension force can be inversely calculated from the measured Brillouin frequency or FBG wavelength.

Next, according to the tension monitoring plan of the PSC member 210, the change in tension of the PSC member 210 can be monitored while repeating the S140 step of measuring the Brillouin frequency and the S150 step of inversely calculating the tension force ( S170).

Accordingly, in the method for monitoring the tension of a prestressed strand using a distributed optical fiber sensor-based smart fixing plate according to an embodiment of the present invention, the smart fixing plate 110 is connected to the PC through the optical fiber sensor 120 attached to the outer circumferential surface. The distribution of strain generated in the strand 230 can be measured based on a distributed optical fiber sensor.

After all, according to an embodiment of the present invention, by forming a groove on the outer circumferential surface of the smart fixing plate installed between the prestressed concrete (PSC) member and the fixing head and easily attaching an optical fiber sensor having a gentle curvature, It is possible to ensure the consistency of the strain measurement direction. In addition, using the fact that the optical signal (Brillouin frequency or FBG wavelength) change measured through distributed optical fiber sensing based on Brillouin scattering or fiber Bragg grating (FBG) has a linear relationship with the strain according to tension, By estimating the tension, it is possible to monitor and manage the tension during the life cycle of the PSC structure.

The above description of the present invention is for illustration, and those of ordinary skill in the art to which the present invention pertains can understand that it can be easily modified into other specific forms without changing the technical spirit or essential features of the present invention. will be. Therefore, it should be understood that the embodiments described above are illustrative in all respects and not restrictive. For example, each component described as a single type may be implemented in a dispersed form, and likewise components described as distributed may be implemented in a combined form.

The scope of the present invention is indicated by the following claims rather than the above detailed description, and all changes or modifications derived from the meaning and scope of the claims and their equivalent concepts should be interpreted as being included in the scope of the present invention. do.

100: PC strand tension monitoring system
110: smart fixing plate 120: optical fiber sensor (optical fiber cable)
130: distributed optical fiber sensor interrogator 140: linear relational expression derivation unit
150: optical signal-tension inversion unit 160: tension monitoring unit
210: PSC structure (PSC bridge) 220: sheath pipe
230: pre-stretched (PC) strand 240: fixing head
111: home

Claims (24)

In the system for monitoring the tension of the PS strand installed in the PSC structure,
A smart fixing plate 110 having a groove 111 formed on the outer circumferential surface and installed between the PSC member 210 and the fixing head 240 of the PSC structure to fix the PC strand 230;
an optical fiber sensor 120 attached along the groove 111 formed on the outer peripheral surface of the smart fixing plate 110 to measure the tension force introduced into the PC strand 230;
a distributed optical fiber sensor interrogator 130 connected to the optical fiber sensor to measure Brillouin frequency or FBG wavelength, which is an optical signal in the optical fiber length direction;
a linear relational expression deriving unit 140 for experimentally deriving a linear relational expression between the tension force and the optical signal;
an optical signal-tensile force inversion unit 150 for inverting the optical signal measured by the distributed optical fiber sensor interrogator 130 into a tension force according to the linear relational expression; and
Including a tension monitoring unit 160 for monitoring the change in tension of the PSC member 210,
The smart fixing plate 110 measures the distribution-type optical fiber sensor-based strain distribution occurring in the PC strand 230 through the optical fiber sensor 120 attached to the outer circumferential surface; The smart fixing plate 110 is manufactured in a hollow cylindrical shape corresponding to the size of the anchorage of the PSC member 210 of the PSC structure, characterized in that a groove 111 is formed on the outer peripheral surface of the smart fixing plate 110 A tension monitoring system for prestressed strands using a distributed fiber optic sensor-based smart fixing plate. delete According to claim 1,
Distributed optical fiber sensor-based, characterized in that the groove 111 of the smart fixing plate 110 is formed to a depth of 0.3 mm substantially equal to the thickness of the optical fiber sensor 120 by CNC (Computer Numerical Control) precision machining. A tension monitoring system for prestressed strands using a smart fixing plate. According to claim 1,
The groove 111 is created to have a predetermined gentle curvature (θ) along the outer circumferential surface of the smart fixing plate, and the optical fiber sensor 120 can be attached thereto. A tension monitoring system for prestressed strands using plates. According to claim 1,
The groove 111 is formed in the center of the outer peripheral surface of the smart fixing plate, and the optical fiber sensor 120 is horizontally wound several times. According to claim 1,
The optical fiber sensor 120 is a distributed optical fiber sensor-based smart fixing plate, characterized in that it is attached with CN (Cyanoacrylate) adhesive along the groove 111 of the smart fixing plate 110, tension monitoring system of the prestressed strand . 7. The method of claim 6,
The outer peripheral surface of the smart fixing plate 110 to which the optical fiber sensor 120 is attached is coated to protect the optical fiber sensor 120. Monitoring of tension of the prestressed strand using a distributed optical fiber sensor-based smart fixing plate. system. According to claim 1,
The distributed optical fiber sensor interrogator 130 is a Brillouin Optical Correlation Domain Analysis (BOCDA) interrogator that measures Brillouin frequency or an FBG-based quasi-distributed resonance frequency mapping interrogator that measures the FBG wavelength. Distributed optical fiber sensor-based tension monitoring system of prestressed strands using a smart fixing plate, characterized in that it is a gator. 9. The method of claim 8,
The BOCDA interrogator is connected to lead wires drawn out from both ends of the optical fiber sensor 120 and measures the Brillouin frequency from the optical fiber sensor 120 in response to the tension force introduced into the PC strand 230. A tension monitoring system for prestressed strands using a distributed optical fiber sensor-based smart fixing plate. 9. The method of claim 8,
The FBG-based quasi-distributed resonant frequency mapping interrogator (RFMI) is connected to a lead wire drawn out from one end of the optical fiber sensor 120 using the reflected wave of the FBG to correspond to the tension force introduced into the PC strand 230 Distributed optical fiber sensor-based smart fixing plate, characterized in that to measure the FBG reflected wave from the optical fiber sensor, the tension monitoring system of the prestressed strand. According to claim 1,
The PC strand 230 to which the optical fiber sensor 120 is attached was experimentally measured using a UTM (universal material testing machine) to measure the Brillouin frequency or FBG wavelength according to the tension through the distributed optical fiber sensor interrogator 130. Then, the optical signal-tension monitoring system using the distributed optical fiber sensor-based smart fixing plate, characterized in that the linear relational expression of the tension force is derived in advance through the measured data. 12. The method of claim 11,
The linear relation is

is given, where,

represents the Brillouin frequency or FBG wavelength,

and

can be calculated in the process of deriving a linear relation using UTM, and the tension is inversely calculated from the measured Brillouin frequency or FBG wavelength. system. In the method of monitoring the tension of the PS strand installed in the PSC structure,
a) attaching the optical fiber sensor 120 along the groove 111 formed on the outer peripheral surface of the smart fixing plate 110;
b) installing the smart fixing plate 110 to which the optical fiber sensor 120 is attached between the PSC member 210 and the fixing head 240;
c) introducing a tension force to the PC strand 230 installed on the PSC member 210 using a tension force introduction device;
d) measuring an optical signal from the optical fiber sensor 120 attached to the smart fixing plate 110 using the distributed optical fiber sensor interrogator 130;
e) inversely calculating the measured optical signal as a tension force using a pre-calculated linear relationship between the optical signal and the tension force; and
f) monitoring the change in tension of the PSC member 210 while repeating steps d) and e) according to the tension monitoring plan of the PSC member 210,
The smart fixing plate 110 measures the distribution of strain generated in the PC strand 230 through the optical fiber sensor 120 attached to the outer peripheral surface based on a distributed optical fiber sensor, and the smart fixing plate 110 is a PSC Distributed optical fiber sensor-based smart fixing plate, characterized in that a groove 111 is formed on the outer peripheral surface of the smart fixing plate 110 but manufactured in a hollow cylindrical shape corresponding to the size of the anchorage of the PSC member 210 of the structure. A method for monitoring tension of prestressed strands using delete 14. The method of claim 13,
Distributed optical fiber sensor-based, characterized in that the groove 111 of the smart fixing plate 110 is formed to a depth of 0.3 mm substantially equal to the thickness of the optical fiber sensor 120 by CNC (Computer Numerical Control) precision machining. A method of monitoring the tension of a prestressed strand using a smart fixing plate. 14. The method of claim 13,
The groove 111 is created to have a predetermined gentle curvature (θ) along the outer circumferential surface of the smart fixing plate, and the optical fiber sensor 120 can be attached thereto. A method for monitoring the tension of a prestressed strand using a plate. 14. The method of claim 13,
The groove 111 is formed in the center of the outer peripheral surface of the smart fixing plate, and the optical fiber sensor 120 is horizontally wound several times. 14. The method of claim 13,
The optical fiber sensor 120 is a distributed optical fiber sensor-based smart fixing plate, characterized in that it is attached with CN (Cyanoacrylate) adhesive along the groove 111 of the smart fixing plate 110. A method for monitoring tension of a prestressed strand . 19. The method of claim 18,
The outer peripheral surface of the smart fixing plate 110 to which the optical fiber sensor 120 is attached is coated to protect the optical fiber sensor 120. Monitoring of tension of the prestressed strand using a distributed optical fiber sensor-based smart fixing plate. Way. 14. The method of claim 13,
The distributed optical fiber sensor interrogator 130 is a distributed optical fiber sensor-based, characterized in that it is a BOCDA interrogator that measures Brillouin frequency or an FBG-based quasi-distributed resonant frequency mapping interrogator that measures FBG wavelength. A method of monitoring the tension of a prestressed strand using a smart fixing plate. 21. The method of claim 20,
In step d), the distributed optical fiber sensor interrogator 130 is connected to lead wires drawn out from both ends of the optical fiber sensor 120 to respond to the tension force introduced into the PC strand 230, the optical fiber sensor 120. Distributed optical fiber sensor-based smart fixing plate, characterized in that the Brillouin frequency is measured from the prestressed strand tension monitoring method. 21. The method of claim 20,
The FBG-based quasi-distributed resonant frequency mapping interrogator (RFMI) is connected to a lead wire drawn out from one end of the optical fiber sensor 120 using the reflected wave of the FBG to correspond to the tension force introduced into the PC strand 230 Distributed optical fiber sensor-based smart fixing plate, characterized in that to measure the FBG reflected wave from the optical fiber sensor, the tension monitoring method of the prestressed strand. 14. The method of claim 13,
In step e), the optical signal according to the tension using the PC strand 230 to which the optical fiber sensor 120 is attached is experimentally transmitted through the distributed optical fiber sensor interrogator 130 using a universal material testing machine (UTM). After the measurement, the optical signal-tension monitoring method using the distributed optical fiber sensor-based smart fixing plate, characterized in that the linear relational expression of the tension force is derived in advance through the measured data. 23. The method of claim 22,
The linear relation is

is given, where,

represents the Brillouin frequency or FBG wavelength,

and

can be calculated in the process of deriving a linear relationship using UTM (Universal Material Testing Machine), and the tension force is inversely calculated from the measured Brillouin frequency or FBG wavelength. Using a distributed optical fiber sensor-based smart fixing plate A method for monitoring tension in prestressed strands.

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