CN210862556U - Bridge dynamic deflection monitoring system based on distributed optical fibers - Google Patents
Bridge dynamic deflection monitoring system based on distributed optical fibers Download PDFInfo
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- CN210862556U CN210862556U CN201921650362.XU CN201921650362U CN210862556U CN 210862556 U CN210862556 U CN 210862556U CN 201921650362 U CN201921650362 U CN 201921650362U CN 210862556 U CN210862556 U CN 210862556U
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Abstract
The utility model relates to a bridge dynamic deflection monitoring system based on distributed optical fiber in optical fiber sensing and bridge monitoring field comprises external optical fiber sensor, transmission optical cable, optical fiber demodulation appearance, monitoring host computer, narrow bandwidth laser light source. The utility model discloses a solve and to have among the current bridge dynamic deflection monitoring that measuring cycle is long, the timeliness is poor, economic effect is low, measuring speed is slow scheduling problem. A bridge dynamic deflection monitoring system based on distributed optical fibers is provided. The external optical fiber sensor is mainly bonded and fixed at the bottom of a main beam of the bridge, and is connected with an optical fiber demodulator by a transmission optical cable, and then the optical fiber demodulator is connected with a monitoring host. And the dynamic deflection of the bridge is automatically measured in real time by adopting an interference type optical time domain reflection technology. The bridge is mainly suitable for a bridge with medium and small span.
Description
Technical Field
The utility model relates to an optical fiber sensing and bridge monitoring field, in particular to bridge dynamic deflection monitoring system based on distributed optical fiber.
Background
The bridge is an important component in modern ground traffic, and can generate transverse, longitudinal and vertical deformation (deflection) under the action of external factors in the using process. If the deformation is too large, not only can various parts of the bridge be damaged to different degrees, the service life of the bridge is shortened, but also the passing of vehicles and pedestrians can be influenced. Therefore, the deformation of the bridge must be monitored in real time, which puts higher demands on the monitoring technology in the field.
The traditional deformation monitoring method comprises manual measuring methods such as precision distance measurement, wire measurement, leveling measurement, dial indicators and the like. The methods need a large amount of manpower and material resources and have monitoring blind spots, so that the method has complex procedures, large workload, difficult quantization and poor integrity for modern highways and railway bridges; for a large bridge, an observation platform needs to be built, traffic control is implemented and the like, so that normal traffic operation is seriously influenced; and the measurement period is long, the timeliness is poor, and real-time monitoring cannot be carried out.
The optical fiber sensing technology is started in the early 70 s of the 20 th century, and is widely applied to the fields of civil engineering, aerospace, electric power systems, medical treatment and the like due to the advantages of small volume, flexibility, safety, electromagnetic interference resistance, simple structure, high measurement precision and the like. The distributed optical fiber sensing technology originated in the end of the 20 th 70 s, and realizes real-time, accurate and distributed monitoring of the external environment by injecting laser pulses into an optical fiber and detecting the backscattered signal of the optical fiber. However, the existing fiber bragg grating sensing technology and Brillouin fiber sensing technology have the problems of low economic effect, low monitoring speed and the like, and the dynamic deflection monitoring of the bridge is difficult to realize.
The interference type optical time domain reflection technology is one of distributed optical fiber sensing technologies, and is characterized in that a beam of laser pulse is injected into an optical fiber, and backward Rayleigh scattering light is detected, so that the change of phase and intensity is demodulated, and the monitoring of external change is realized. The optical time domain reflection technology has the advantages of distributed optical fiber sensing, and has the characteristics of high measurement speed, high sensitivity, long measurement distance, severe environment resistance and no maintenance. At present, the optical time domain reflection technology is widely applied to the fields of perimeter security monitoring, weak vibration measurement, temperature and the like, but is not applied to the aspect of bridge dynamic deflection monitoring.
Disclosure of Invention
The utility model discloses a solve exist not enough in the current bridge dynamic deflection monitoring, provide a bridge dynamic deflection monitoring system based on distributed optical fiber, automatic, real-time, quick, accurate, effectual monitoring operation period bridge dynamic deflection ensures the normal operating of bridge.
The utility model adopts the technical proposal that: bridge dynamic deflection monitoring system based on distributed optical fiber mainly comprises external optical fiber sensor, transmission optical cable, optical fiber demodulator, monitoring host computer, narrow bandwidth laser light source, its characterized in that: the external optical fiber sensor is bonded and fixed at the bottom of the girder of the bridge, and is connected with the optical fiber demodulator by a transmission optical cable, and then the optical fiber demodulator is connected with the monitoring host. And the dynamic deflection of the bridge is automatically measured in real time by adopting an interference type optical time domain reflection technology. The working principle of the deflection monitoring software used in the monitoring host machine is as follows: according to the demodulated change quantity delta I of the backward Rayleigh scattered light intensity of each position in the optical fiber before and after the bridge is deformedi(x) Calculating the deflection of each position of the bridge by using the following formula, and displaying the deflection change curve of the bridge:
in the formula,. DELTA.I1(x)、ΔI2(x) The variation of the back scattered light intensity of each position in the optical fiber before and after the deformation of the bridge, h is the vertical distance from the optical fiber to the axis of the main beam, CIεIs the scattered light intensity strain coefficient.
The external optical fiber sensor is manufactured by the following steps:
a1, wrapping a polyethylene outer cladding layer with the thickness of 1mm outside the bare fiber to form a sensing fiber;
2, alternately laying sensing optical fibers in a U-shaped plastic thin plate in a snake-shaped mode in the transverse direction and the longitudinal direction, wherein the longitudinal sensing optical fibers are less than the transverse direction, fixing the laid sensing optical fibers by using strong glue, and reserving sensing optical fibers with certain lengths at two ends of the U-shaped plastic thin plate;
a3, filling the U-shaped plastic thin plate with epoxy resin;
a4, covering a rectangular plastic sheet on the U-shaped plastic sheet for packaging and fixing;
and a5, connecting optical fiber jumpers on the reserved sensing optical fibers in a dissolving mode.
The external optical fiber sensor is adhered to the bottom of the bridge girder by strong glue and then fixed by screws.
The invention has the beneficial effects that:
1. the external optical fiber sensor is bonded and fixed at the bottom of the girder of the bridge, and is connected with the optical fiber demodulator by a transmission optical cable, and then the optical fiber demodulator is connected with the monitoring host. The interference type optical time domain reflection technology is adopted to realize real-time, rapid, accurate and effective monitoring of the dynamic deflection of the bridge and ensure the normal operation of the bridge.
2. By adopting the external optical fiber sensor, the condition that the integrity of the structure is damaged by slotting on the beam is avoided, and better coordinated deformability between the sensor and the bridge is ensured, so that the accuracy of a measuring result is improved. The spatial resolution of the monitoring system is improved to a certain extent by the snake-shaped optical fiber arrangement mode, and external disturbance is amplified.
Drawings
FIG. 1 is a schematic diagram of a monitoring system
FIG. 2 is a diagram of an external optical fiber sensor
FIG. 3 shows a structure of a sensing fiber
In the figure, 1, a U-shaped plastic plate, 2, a rectangular plastic plate, 3, epoxy resin, 4, an optical fiber jumper, 5, a bare optical fiber, 6, a polyethylene outer cladding layer, 7, a bridge main beam, 8, an external optical fiber sensor, 9, a transmission optical cable, 10, an optical fiber demodulator, 11, a monitoring host and 12, a narrow-bandwidth laser source. 13. A sensing fiber.
Detailed Description
The present invention will be further explained with reference to the accompanying drawings.
The bridge dynamic deflection monitoring system is composed of an external optical fiber sensor 8, a transmission optical cable 9, an optical fiber demodulator 10, a monitoring host 11 and a narrow-bandwidth laser light source 12, and is characterized in that: an external optical fiber sensor 8 is bonded and fixed at the bottom of a main beam 7 of the bridge, the external optical fiber sensor 8 is connected with an optical fiber demodulator 10 through a transmission optical cable 9, and then the optical fiber demodulator 10 is connected with a monitoring host 11. The dynamic deflection of the bridge is automatically measured in real time by adopting an interference type optical time domain reflection technology, as shown in figure 1.
The working principle of the deflection monitoring software used in the monitoring host machine is as follows: according to the demodulated change quantity delta I of the backward Rayleigh scattered light intensity of each position in the optical fiber before and after the bridge is deformedi(x) Calculating the deflection of each position of the bridge by using the following formula, and displaying the deflection change curve of the bridge:
in the formula,. DELTA.I1(x)、ΔI2(x) The variation of the back scattered light intensity of each position in the optical fiber before and after the deformation of the bridge, h is the vertical distance from the optical fiber to the axis of the main beam, CIεIs the scattered light intensity strain coefficient.
The calculation principle is as follows:
the intensity of the backscattered light in the optical fiber is linear with strain, as shown in formula 1,
ΔI＝CIεΔε (1)
delta I in the formula (1) is the intensity change of backward scattering light at each position in the optical fiber before and after the deformation of the bridge, CIεFor the scattered light intensity strain coefficient, Δ ε is the amount of change in strain.
The vertical deformation in the bridge is small, a micro-section is taken at the whole length of the bridge, and the deflection theory is obtained by a material mechanics integral method.
In the formulas (2), (3) and (4), epsilon (x) is a strain value of the bridge girder, h is a vertical distance from the optical fiber to the axis of the girder, rho is a curvature radius corresponding to a neutral layer in the micro-segment, and dθIs the relative corner of two sections in the micro-section.
The bending curve of the bridge is shown in the combined formulas (1) and (4):
as shown in fig. 2, the external optical fiber sensor 8 is manufactured by the following steps:
1, alternately laying sensing optical fibers 13 in a U-shaped plastic thin plate 1 in a serpentine mode in the transverse direction and the longitudinal direction, wherein the number of the longitudinal sensing optical fibers 13 is less than that of the transverse direction, fixing the laid sensing optical fibers by using super glue, and reserving a certain length of sensing optical fibers 13 at two ends of the U-shaped plastic thin plate 1;
a2, filling the U-shaped plastic thin plate 1 with epoxy resin 3;
a3, covering a rectangular plastic sheet 2 on the U-shaped plastic sheet 1 for packaging and fixing;
a4, and connecting the optical fiber jumper 4 on the reserved sensing optical fiber 13 in a melting way.
As shown in FIG. 3, the sensing fiber 13 is manufactured by wrapping a polyethylene outer cladding 6 with a thickness of 1mm around the bare fiber 5.
Example (b):
1. processing the bare optical fiber: and wrapping a polyethylene outer cladding layer with the thickness of 1mm outside the bare optical fiber to form the sensing optical fiber.
2. Manufacturing an external optical fiber sensor:
1, alternately laying sensing optical fibers in a U-shaped plastic thin plate in a snake-shaped mode in the transverse direction and the longitudinal direction, wherein the longitudinal sensing optical fibers are less than the transverse direction, fixing the laid sensing optical fibers by using strong glue, and reserving sensing optical fibers with certain lengths at two ends of the U-shaped plastic thin plate;
a2, filling the U-shaped plastic thin plate with epoxy resin;
a3, covering a rectangular plastic sheet on the U-shaped plastic sheet for packaging and fixing;
and a4, connecting optical fiber jumpers on the reserved sensing optical fibers in a dissolving mode.
3. The external optical fiber sensor is bonded at the bottom of the bridge girder by strong glue and then fixed by screws. The external optical fiber sensor is connected with the optical fiber demodulator by the transmission optical cable, and then the optical fiber demodulator is connected with the monitoring host. And the dynamic deflection of the bridge is automatically measured in real time by adopting an interference type optical time domain reflection technology.
Claims (3)
1. Bridge dynamic deflection monitoring system based on distributed optical fiber mainly comprises external optical fiber sensor (8), transmission optical cable (9), optical fiber demodulator (10), monitoring host (11), narrow bandwidth laser light source (12), its characterized in that: the external optical fiber sensor (8) is fixedly bonded on the bridge, the external optical fiber sensor (8) is connected with the optical fiber demodulator (10) through the transmission optical cable (9), the optical fiber demodulator (10) is connected with the monitoring host (11), and the dynamic deflection of the bridge is automatically measured in real time by adopting an interference type optical time domain reflection technology.
2. The system for monitoring dynamic deflection of a bridge based on distributed optical fiber according to claim 1, wherein: the external optical fiber sensor (8) consists of a U-shaped plastic thin plate (1), a rectangular plastic thin plate (2), an optical fiber jumper (4) and a sensing optical fiber (13); the sensing optical fiber (13) is internally provided with a bare optical fiber (5), and the outside is provided with a polyethylene outer cladding (6) with the thickness of 1 mm; the sensing optical fibers (13) are laid and fixed in the U-shaped plastic thin plate (1) in a serpentine mode of being alternately arranged in the horizontal direction and the vertical direction less than the horizontal direction, the U-shaped plastic thin plate (1) with the sensing optical fibers (13) laid thereon is filled with epoxy resin (3), and the rectangular plastic thin plate (2) is packaged on the U-shaped plastic thin plate (1); the optical fiber jumper (4) is connected to the reserved sensing optical fiber (13) in a melting mode.
3. The system for monitoring dynamic deflection of a bridge based on distributed optical fiber according to claim 1, wherein: the external optical fiber sensor (8) is positioned at the bottom of the bridge girder (7) and is fixed by a screw.
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110514134A (en) * | 2019-09-30 | 2019-11-29 | 西南石油大学 | Bridge dynamic deflection monitoring method based on distribution type fiber-optic |
| CN111982002A (en) * | 2020-08-28 | 2020-11-24 | 株洲时代新材料科技股份有限公司 | Distributed optical fiber sensing-based vertical tidal current energy blade crack monitoring device and monitoring method |
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2019
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN110514134A (en) * | 2019-09-30 | 2019-11-29 | 西南石油大学 | Bridge dynamic deflection monitoring method based on distribution type fiber-optic |
| CN111982002A (en) * | 2020-08-28 | 2020-11-24 | 株洲时代新材料科技股份有限公司 | Distributed optical fiber sensing-based vertical tidal current energy blade crack monitoring device and monitoring method |
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