CN117704991A - Multi-span concrete beam prestress on-line monitoring system and method based on fiber bragg grating sensing - Google Patents
Multi-span concrete beam prestress on-line monitoring system and method based on fiber bragg grating sensing Download PDFInfo
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- 239000004567 concrete Substances 0.000 title claims abstract description 138
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- 238000012544 monitoring process Methods 0.000 title claims abstract description 31
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- 239000013307 optical fiber Substances 0.000 claims abstract description 120
- 229910000831 Steel Inorganic materials 0.000 claims abstract description 100
- 239000010959 steel Substances 0.000 claims abstract description 100
- 238000012545 processing Methods 0.000 claims abstract description 23
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- WABPQHHGFIMREM-UHFFFAOYSA-N lead(0) Chemical compound [Pb] WABPQHHGFIMREM-UHFFFAOYSA-N 0.000 claims description 4
- 238000004806 packaging method and process Methods 0.000 claims description 4
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- 229920001971 elastomer Polymers 0.000 description 1
- 239000000806 elastomer Substances 0.000 description 1
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- 239000000463 material Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003287 optical effect Effects 0.000 description 1
- 239000011513 prestressed concrete Substances 0.000 description 1
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Abstract
The invention discloses a multi-span concrete beam prestress on-line monitoring system based on fiber bragg grating sensing, which comprises the following steps: the steel strand is internally packaged with a temperature fiber grating sensing optical fiber and a strain fiber grating sensing optical fiber, and the temperature fiber grating sensing optical fiber and the strain fiber grating sensing optical fiber penetrate through two ends of the slotted steel wire and are outwards extended and packaged into a strain fiber lead and a temperature fiber lead; the demodulation unit transmits light beams, the light beams enter the temperature fiber grating sensing optical fiber and the strain fiber grating sensing optical fiber, after passing through each grating in sequence, each grating reflects the light beams back into the demodulation unit according to time difference and wavelength of received light signals, the demodulation unit records wavelength signal changes of each grating one by one to form electric signals for storage, and demodulation is realized; the data processing unit calculates the prestress value of each concrete-crossing beam according to the electric signals of each grating, and the invention is applicable to the dense and accurate monitoring requirements of the prestress of the concrete Liang Yancheng with various types and total spans not exceeding 5 km.
Description
Technical Field
The invention relates to the field of multi-span concrete beam prestress on-line monitoring. More particularly, the invention relates to a multi-span concrete beam prestress on-line monitoring system and method based on fiber grating sensing.
Background
A large number of prestressed steel strand technologies are applied in concrete structures. The prestress steel strand is a core stress member in the prestress member, and in the construction tensioning and service process, the prestress level is reduced and the prestress distribution is uneven due to superposition of various factors such as material characteristics, pipeline friction, inflection points, uneven grouting and the like, and the change of the prestress level along the steel strand directly influences the bearing capacity change of the stress structure. If the prestress loss of the steel strand is too large, the stress member may be greatly deformed or even be damaged without symptoms in the construction or use process, so that quality safety accidents are caused.
The existing steel strand prestress detection or monitoring means comprise a pressure ring method, a fiber grating method, a vibration frequency method, a pressure sensor measuring point method, a strain gauge measuring point method, a magnetic flux detection method, a stress release method and the like. The force measuring ring is arranged between the anchor rope backing plate and the anchor cup, and is simple and convenient to install and use and visual in measuring effect. But the method is easily affected by unbalanced load during construction and installation, and the precision is not high. The resistance strain gauge is directly stuck on the elastomer, and has simple structure and high measurement precision, but is easy to damage and has poor durability. The output of the resistance strain type sensor and the output of the differential resistance type sensor are analog signals, so that long-distance transmission cannot be performed, and the requirement of long-distance monitoring cannot be met. The magnetic flux sensor of the magnetic flux method can only be arranged outside the steel strand, is easily affected by electromagnetic interference and a corrugated pipe sleeve during working, cannot accurately measure the prestress state, and can only be used for static measurement. The stress release method measures the actual stress of different positions of the steel strand through the strain gauge, and the severe error is controlled to be about 2%, but the method belongs to the local damage technology, the stress redistribution of the steel strand can be caused during mechanical cutting, and meanwhile, the false strain output can be formed by the released heat during the cutting of the steel strand, so that the measurement accuracy is greatly influenced. In summary, the existing bridge steel strand prestress monitoring method has a plurality of problems, and particularly cannot acquire the distribution condition of the steel strand along-path prestress.
Therefore, the system and the method for on-line monitoring the prestress of the multi-span concrete beam based on fiber bragg grating sensing are provided, and the problems of few monitoring points, low monitoring precision and high monitoring cost on the prestress of the steel strand of the concrete box beam in the prior art are solved.
Disclosure of Invention
To achieve these objects and other advantages and in accordance with the purpose of the invention, as embodied and broadly described herein, there is provided an on-line monitoring system for prestress of a multi-span concrete beam based on fiber grating sensing, comprising:
the steel strand is internally packaged with a temperature fiber bragg grating sensing optical fiber and a strain fiber bragg grating sensing optical fiber;
the steel strand comprises side wires and a slotted steel wire, a plurality of side wires are wrapped outside the slotted steel wire, at least two accommodating grooves are formed in the surface of the slotted steel wire along the length direction of the slotted steel wire and used for accommodating the strain fiber bragg grating sensing optical fiber and the temperature fiber bragg grating sensing optical fiber, and the strain fiber bragg grating sensing optical fiber and the temperature fiber bragg grating sensing optical fiber penetrate through the two ends of the slotted steel wire and outwards extend and are packaged into a strain fiber lead and a temperature fiber lead;
the demodulation unit is used for storing electric signals formed by recording the wavelength signal changes of each grating one by one according to the time difference and the wavelength of the received light signals, so as to realize demodulation;
the demodulation unit is also connected with the data processing unit, and the data processing unit calculates the prestress value of each cross concrete beam according to the electric signals of each grating.
In another preferred technical scheme, optical fiber lead transition pipes are respectively arranged at two ends of the steel strand, and the strain optical fiber lead and the temperature optical fiber lead penetrate out of two ends of the slotted steel wire and continuously penetrate through the optical fiber lead transition pipes.
In another preferable technical scheme, the diameters of the temperature fiber grating sensing optical fiber and the strain fiber grating sensing optical fiber are 0.15-1.2mm, and the hinging pitch of the side wire is kept within 180-250 mm.
In another preferred technical scheme, the data processing unit calculates prestress value of each cross concrete beam according to the electric signals of each grating, wherein,
when the data processing unit directly processes the strain fiber grating wavelength signal into a concrete beam prestress value, the following formula is adopted:
f i ＝X i *K i
the fusion algorithm considering the temperature fiber grating wavelength signal compensation is as follows:
F i ＝(X i -T i )*K i
in the above, f i The prestress value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; x is X i The wavelength variation value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; k (K) i The corresponding value of the wavelength and the cable force of the corresponding steel strand of the ith strain grating measuring point of the multi-span concrete Liang Yancheng is calibrated in a factory; f (F) i Taking the prestress value after temperature compensation into consideration for the ith strain grating measuring point of the multi-span concrete Liang Yancheng; t (T) i The wavelength change value of the ith temperature grating measuring point of the multi-span concrete Liang Yancheng.
In another preferred technical scheme, the grating spacing between the temperature fiber grating sensing fiber and the strain fiber grating sensing fiber is 1m, and the reflectivities of all gratings are the same and are not more than 1%.
On the other hand, the invention also provides a multi-span concrete beam prestress on-line monitoring method based on fiber bragg grating sensing, which comprises the following steps:
the method comprises the following steps:
s1, prefabricating a plurality of steel strands, and internally packaging a temperature fiber grating sensing optical fiber 1 and a strain fiber grating sensing optical fiber 10-3;
s2, penetrating a plurality of steel strands into a prestressed corrugated pipe of the 1 st span concrete beam and tensioning the steel strands in place during the construction of the 1 st span concrete beam steel strand prestressed beam of the multi-span concrete beam; when the 2 nd cross concrete beam steel strand prestress beam is constructed, penetrating a plurality of steel strands into the 2 nd cross concrete prestress corrugated pipe and tensioning the steel strands in place; when the steel strand prestressed bundles of the ith cross concrete beam are constructed, penetrating a plurality of steel strands into the prestressed corrugated pipe of the ith cross concrete beam and tensioning the steel strands into place, and repeating until all the steel strands in the cross concrete beam are installed;
s3, welding or mechanically connecting a strain optical fiber lead and a temperature optical fiber lead in the 1 st span concrete Liang Nagang stranded wire and a strain optical fiber lead and a temperature optical fiber lead in the 2 nd span concrete Liang Nagang stranded wire at the joint of the 1 st span concrete beam and the 2 nd span concrete beam; sequentially connecting a strain optical fiber lead and a temperature optical fiber lead of the ith cross-concrete Liang Nagang stranded wire and a strain optical fiber lead and a temperature optical fiber lead of the (i+1) th cross-concrete Liang Nagang stranded wire until the temperature optical fiber grating sensing optical fibers and the strain optical fiber grating sensing optical fibers in all the steel stranded wires in each cross along the multi-cross-concrete beam are connected in series;
s4, connecting a strain optical fiber lead wire and a temperature optical fiber lead wire of the initial section or the final section of the steel strand which are connected in series with a demodulation unit, enabling the demodulation unit to emit 1510-1590 nm bandwidth light beams, enabling the light beams to enter a temperature optical fiber grating sensing optical fiber and a strain optical fiber grating sensing optical fiber, enabling each grating to reflect light beams back into the demodulation unit according to time difference and wavelength of received light signals after the light beams sequentially pass through each grating, and enabling the demodulation unit to record wavelength signal changes of each grating one by one to form electric signals for storage, so that demodulation is achieved;
and the data processing unit calculates the prestress value of each cross-concrete beam according to the electric signals of each grating.
In another preferred technical scheme, after S3 completes the serial connection of the temperature fiber grating sensing fibers and the strain fiber grating sensing fibers in all steel strands in each span along the multi-span concrete beam, the concrete beam joint can be poured, and a plurality of concrete beams are changed into continuous concrete beams.
In another preferred technical scheme, the data processing unit calculates prestress value of each cross concrete beam according to the electric signals of each grating, wherein,
when the data processing unit directly processes the strain fiber grating wavelength signal into a concrete beam prestress value, the following formula is adopted:
f i ＝X i *K i
the fusion algorithm considering the temperature fiber grating wavelength signal compensation is as follows:
F i ＝(X i -T i )*K i
in the above, f i The prestress value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; x is X i The wavelength variation value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; k (K) i The corresponding value of the wavelength and the cable force of the corresponding steel strand of the ith strain grating measuring point of the multi-span concrete Liang Yancheng is calibrated in a factory; f (F) i Taking the prestress value after temperature compensation into consideration for the ith strain grating measuring point of the multi-span concrete Liang Yancheng; t (T) i The wavelength change value of the ith temperature grating measuring point of the multi-span concrete Liang Yancheng.
The invention at least comprises the following beneficial effects:
(1) The multi-span concrete beam prestress on-line monitoring system based on fiber bragg grating sensing is applicable to the concrete Liang Yancheng prestress dense accurate monitoring requirements of various types with total spans not exceeding 5 km.
(2) According to the invention, the steel stranded wires of the packaging temperature and strain fiber bragg grating sensing optical fibers are buried into the concrete beam during the construction of the prestressed beam, and the advantages of large composite amount of the weak grating array grating and dense grating measuring points are utilized to form a concrete Liang Duokua long-distance prestress on-line monitoring network, so that the prestress of the prestressed concrete beam structure is measurable, and the structural safety is ensured.
(3) Furthermore, the invention is based on the fiber grating array sensing technology, and the monitoring system has good synchronism, high measurement accuracy and long service life by utilizing the optical signal measuring points.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention.
Drawings
FIG. 1 is a schematic structural diagram of a multi-span concrete beam prestress on-line monitoring system based on fiber grating sensing in an embodiment of the invention;
FIG. 2 is a schematic view of a steel strand according to an embodiment of the present invention;
FIG. 3 is a schematic view showing the structure of a slotted steel wire in an embodiment of the present invention;
FIG. 4 is a schematic diagram of on-line monitoring of prestressing of a multi-span concrete beam according to an embodiment of the present invention;
reference numerals: 1. 1 st cross concrete beam; 2. a concrete beam joint; 3. 2 nd cross concrete beam; 4. ith cross-concrete beam; 21. a data processing unit; 31. a demodulation unit; 10. steel strand; 10-1, edge yarn; 10-2, grooving steel wire; 10-3, a strain fiber bragg grating sensing optical fiber; 10-4, a temperature fiber grating sensing optical fiber; 11. an optical fiber lead transition tube; 12. a strained fiber optic lead; 13. and (5) temperature optical fiber leads.
Detailed Description
The present invention is described in further detail below with reference to the drawings to enable those skilled in the art to practice the invention by referring to the description.
The following description is presented to enable one of ordinary skill in the art to make and use the invention. The preferred embodiments in the following description are by way of example only and other obvious variations will occur to those skilled in the art. The basic principles of the invention defined in the following description may be applied to other embodiments, variations, modifications, equivalents, and other technical solutions without departing from the spirit and scope of the invention.
It will be appreciated by those skilled in the art that in the present disclosure, the terms "longitudinal," "transverse," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," "outer," etc. refer to an orientation or positional relationship based on that shown in the drawings, which is merely for convenience of description and to simplify the description, and do not indicate or imply that the apparatus or elements referred to must have a particular orientation, be constructed and operated in a particular orientation, and therefore the above terms should not be construed as limiting the present invention.
It will be understood that the terms "a" and "an" should be interpreted as referring to "at least one" or "one or more," i.e., in one embodiment, the number of elements may be one, while in another embodiment, the number of elements may be plural, and the term "a" should not be interpreted as limiting the number.
As shown in fig. 1-4, a preferred embodiment of the present invention provides a multi-span concrete beam prestress on-line monitoring system based on fiber grating sensing, comprising:
the steel strand 10 is internally packaged with a temperature fiber bragg grating sensing fiber 10-4 and a strain fiber bragg grating sensing fiber 10-3;
the steel strand 10 comprises edge wires 10-1 and slotted steel wires 10-2, wherein a plurality of edge wires 10-1 are wrapped outside the slotted steel wires 10-2, at least two accommodating grooves are formed in the surface of the slotted steel wires 10-2 along the length direction of the slotted steel wires, the accommodating grooves are used for accommodating strain fiber bragg grating sensing optical fibers 10-3 and temperature fiber bragg grating sensing optical fibers 10-4, and the strain fiber bragg grating sensing optical fibers 10-3 and the temperature fiber bragg grating sensing optical fibers 10-4 penetrate out of two ends of the slotted steel wires 10-2 and are outwards extended and packaged into strain fiber leads 12 and temperature fiber lead 13;
the strain optical fiber lead 12 and the temperature optical fiber lead 13 are both connected to the demodulation unit 31, the demodulation unit 31 transmits 1510nm-1590nm bandwidth light beams, the light with the wavelength exceeding the range has larger transmission loss in the optical fiber, long-distance transmission is not facilitated, the light beams enter the temperature optical fiber grating sensing optical fiber 10-4 and the strain optical fiber grating sensing optical fiber 10-3, after sequentially passing through each grating, each grating reflects the light beams back into the demodulation unit 31 according to the time difference and the wavelength of the received light signals, and the demodulation unit 31 records the wavelength signal change of each grating one by one to form an electric signal for storage, so that demodulation is realized;
the demodulation unit 31 is also connected with a data processing unit, and the data processing unit calculates the prestress value of each cross-concrete beam according to the electric signals of each grating.
In the technical scheme, the diameter of the steel strand 10 is 15.2mm, the diameter of the 10-2-diameter of the slotted steel wire is 5.2mm, the depth of the accommodating groove is not smaller than the diameters of the strain fiber bragg grating sensing optical fiber 10-3 and the temperature fiber bragg grating sensing optical fiber 10-4, so that the two fiber bragg grating sensing optical fibers can be better protected, the diameters of the temperature fiber bragg grating sensing optical fiber 10-4 and the strain fiber bragg grating sensing optical fiber 10-3 are 0.15-1.2mm, the reaming pitch of the edge wire 10-1 is kept within 180-250mm, and the steel strand is used as a carrier of the fiber bragg grating to protect the fiber bragg grating.
The strain fiber bragg grating sensing optical fiber 10-3 and the temperature fiber bragg grating sensing optical fiber 10-4 have the advantages of large array grating multiplexing amount and dense grating measuring points, are packaged in the steel stranded wires, can cover all multi-span concrete beams along with the installation of the steel stranded wires in the whole process, and finally can form a concrete Liang Duokua long-distance prestress on-line monitoring network.
In another technical scheme, two ends of the steel strand 10 are respectively provided with an optical fiber lead transition pipe 11, and the strain optical fiber lead 12 and the temperature optical fiber lead 13 penetrate out of two ends of the slotted steel wire 10-2 and continuously pass through the optical fiber lead transition pipe 11, which is equivalent to protecting the connection positions of the strain optical fiber lead 12, the temperature optical fiber lead 13, the temperature optical fiber grating sensing optical fiber 10-4 and the strain optical fiber grating sensing optical fiber 10-3 by utilizing the optical fiber lead transition pipe 11.
In another technical scheme, the data processing unit calculates the prestress value of each cross-concrete beam according to the electric signals of each grating, wherein,
when the data processing unit directly processes the strain fiber grating wavelength signal into a concrete beam prestress value, the following formula is adopted:
f i ＝X i *K i
the fusion algorithm considering the temperature fiber grating wavelength signal compensation is as follows:
F i ＝(X i -T i )*K i
in the above, f i The prestress value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; x is X i The wavelength variation value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; k (K) i The corresponding value of the wavelength and the cable force of the corresponding steel strand of the ith strain grating measuring point of the multi-span concrete Liang Yancheng is calibrated in a factory; f (F) i Taking the prestress value after temperature compensation into consideration for the ith strain grating measuring point of the multi-span concrete Liang Yancheng; t (T) i The wavelength change value of the ith temperature grating measuring point of the multi-span concrete Liang Yancheng. .
In another technical scheme, the grating spacing between the temperature fiber bragg grating sensing fiber 10-4 and the strain fiber bragg grating sensing fiber 10-3 is 1m, and the reflectivity of all gratings is equal to or less than 1%.
The other technical scheme also provides a multi-span concrete beam prestress on-line detection method based on fiber grating array sensing, which comprises the following steps:
s1, prefabricating a plurality of steel strands, and internally packaging a temperature fiber grating sensing optical fiber 10-4 and a strain fiber grating sensing optical fiber 10-3;
s2, penetrating a plurality of steel strands 10 into a prestressed corrugated pipe of the 1 st span concrete beam 1 and tensioning the steel strands in place during the construction of the 1 st span concrete beam 1 steel strand prestressed bundles of the multi-span concrete beam; when the 2 nd cross concrete beam 3 steel strand prestress beam is constructed, a plurality of steel strands 10 are penetrated into the 2 nd cross concrete beam 3 prestress corrugated pipe and stretched in place; when the prestressed bundles of the steel strands of the ith cross concrete beam 4 are constructed, penetrating a plurality of steel strands 10 into the prestressed corrugated pipe of the ith cross concrete beam 3 and tensioning the steel strands in place, and repeating until all the steel strands in the cross concrete beam are installed;
s3, welding or mechanically connecting a strain optical fiber lead 12 and a temperature optical fiber lead 13 in a steel strand 10 in the 1 st cross concrete beam 1 and a strain optical fiber lead 13 and a temperature optical fiber lead 13 in a steel strand 10 in the 2 nd cross concrete beam 3 at a concrete beam joint 2 of the 1 st cross concrete beam 1 and the 2 nd cross concrete beam 3; the strain optical fiber lead 12 and the temperature optical fiber lead 13 of the steel strands 10 in the ith cross concrete beam 4 and the strain optical fiber lead 12 and the temperature optical fiber lead 13 of the (i+1) th cross concrete Liang Nagang) strand 10 are sequentially connected until the temperature optical fiber grating sensing optical fibers 10-4 and the strain optical fiber grating sensing optical fibers 10-3 in all the steel strands 10 in each cross along the multi-cross concrete beam are connected in series; pouring can be performed on the concrete beam joints 2, and a plurality of concrete beams are changed into continuous concrete beams.
S4, connecting a strain optical fiber lead 12 and a temperature optical fiber lead 13 of the initial section or the final section of the steel strand 10 which are connected in series, and connecting the demodulation unit 31, wherein the demodulation unit 31 transmits 1510-1590 nm bandwidth light beams, the light beams enter the temperature optical fiber grating sensing optical fiber 10-4 and the strain optical fiber grating sensing optical fiber 10-3, after passing through each grating in sequence, each grating reflects the light beams back into the demodulation unit 31 according to time difference and wavelength of a received light signal, and the demodulation unit 31 records the wavelength signal change of each grating one by one to form an electric signal for storage, so that demodulation is realized;
the data processing unit 21 calculates prestress values of each cross concrete beam according to the electric signals of the gratings.
Wherein the data processing unit 21 calculates prestress values of each cross-concrete beam according to the electric signals of the gratings, wherein,
when the data processing unit directly processes the strain fiber grating wavelength signal into a concrete beam prestress value, the following formula is adopted:
f i ＝X i *K i
the fusion algorithm considering the temperature fiber grating wavelength signal compensation is as follows:
F i ＝(X i -T i )*K i
in the above, f i The prestress value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; x is X i The wavelength variation value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; k (K) i The corresponding value of the wavelength and the cable force of the corresponding steel strand of the ith strain grating measuring point of the multi-span concrete Liang Yancheng is calibrated in a factory; f (F) i Taking the prestress value after temperature compensation into consideration for the ith strain grating measuring point of the multi-span concrete Liang Yancheng; t (T) i The wavelength change value of the ith temperature grating measuring point of the multi-span concrete Liang Yancheng.
Although embodiments of the present invention have been disclosed above, it is not limited to the details and embodiments shown and described, it is well suited to various fields of use for which the invention would be readily apparent to those skilled in the art, and accordingly, the invention is not limited to the specific details and illustrations shown and described herein, without departing from the general concepts defined in the claims and their equivalents.
Claims (8)
1. The multi-span concrete beam prestress on-line monitoring system based on fiber bragg grating sensing is characterized by comprising:
the steel strand is internally packaged with a temperature fiber bragg grating sensing optical fiber and a strain fiber bragg grating sensing optical fiber;
the steel strand comprises side wires and a slotted steel wire, a plurality of side wires are wrapped outside the slotted steel wire, at least two accommodating grooves are formed in the surface of the slotted steel wire along the length direction of the slotted steel wire and used for accommodating the strain fiber bragg grating sensing optical fiber and the temperature fiber bragg grating sensing optical fiber, and the strain fiber bragg grating sensing optical fiber and the temperature fiber bragg grating sensing optical fiber penetrate through the two ends of the slotted steel wire and outwards extend and are packaged into a strain fiber lead and a temperature fiber lead;
the demodulation unit is used for storing electric signals formed by recording the wavelength signal changes of each grating one by one according to the time difference and the wavelength of the received light signals, so as to realize demodulation;
the demodulation unit is also connected with the data processing unit, and the data processing unit calculates the prestress value of each cross concrete beam according to the electric signals of each grating.
2. The fiber bragg grating sensing-based multi-span concrete beam prestress on-line monitoring system according to claim 1, wherein fiber lead transition pipes are respectively arranged at two ends of the steel strand, and the strain fiber lead and the temperature fiber lead penetrate out of two ends of the slotted steel wire to continuously penetrate through the fiber lead transition pipes.
3. The multi-span concrete beam prestress on-line monitoring system based on fiber bragg grating sensing according to claim 1, wherein the diameters of the temperature fiber bragg grating sensing fiber and the strain fiber bragg grating sensing fiber are 0.15-1.2mm, and the hinging pitch of the edge wire is kept within 180-250 mm.
4. The fiber grating sensing-based multi-span concrete beam prestress on-line monitoring system of claim 1, wherein the data processing unit calculates each span concrete beam prestress value according to the electric signals of the gratings, wherein,
when the data processing unit directly processes the strain fiber grating wavelength signal into a concrete beam prestress value, the following formula is adopted:
f i ＝X i *K i
the fusion algorithm considering the temperature fiber grating wavelength signal compensation is as follows:
F i ＝(X i -T i )*K i
in the above, f i The prestress value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; x is X i The wavelength variation value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; k (K) i The corresponding value of the wavelength and the cable force of the corresponding steel strand of the ith strain grating measuring point of the multi-span concrete Liang Yancheng is calibrated in a factory; f (F) i Taking the prestress value after temperature compensation into consideration for the ith strain grating measuring point of the multi-span concrete Liang Yancheng; t (T) i The wavelength change value of the ith temperature grating measuring point of the multi-span concrete Liang Yancheng.
5. The fiber bragg grating sensing-based multi-span concrete beam prestress on-line monitoring system according to claim 1, wherein the grating spacing between the temperature fiber bragg grating sensing optical fiber and the grating inscribed on the strain fiber bragg grating sensing optical fiber is 1m, and the reflectivity of all gratings is the same and is not more than 1%.
6. The on-line detection method of the multi-span concrete beam prestress on-line monitoring system based on fiber bragg grating sensing according to any one of claims 1 to 5, which is characterized by comprising the following steps:
s1, prefabricating a plurality of steel strands, and internally packaging a temperature fiber grating sensing optical fiber 1 and a strain fiber grating sensing optical fiber 10-3;
s2, penetrating a plurality of steel strands into a prestressed corrugated pipe of the 1 st span concrete beam and tensioning the steel strands in place during the construction of the 1 st span concrete beam steel strand prestressed beam of the multi-span concrete beam; when the 2 nd cross concrete beam steel strand prestress beam is constructed, penetrating a plurality of steel strands into the 2 nd cross concrete prestress corrugated pipe and tensioning the steel strands in place; when the steel strand prestressed bundles of the ith cross concrete beam are constructed, penetrating a plurality of steel strands into the prestressed corrugated pipe of the ith cross concrete beam and tensioning the steel strands into place, and repeating until all the steel strands in the cross concrete beam are installed;
s3, welding or mechanically connecting a strain optical fiber lead and a temperature optical fiber lead in the 1 st span concrete Liang Nagang stranded wire and a strain optical fiber lead and a temperature optical fiber lead in the 2 nd span concrete Liang Nagang stranded wire at the joint of the 1 st span concrete beam and the 2 nd span concrete beam; sequentially connecting a strain optical fiber lead and a temperature optical fiber lead of the ith cross-concrete Liang Nagang stranded wire and a strain optical fiber lead and a temperature optical fiber lead of the (i+1) th cross-concrete Liang Nagang stranded wire until the temperature optical fiber grating sensing optical fibers and the strain optical fiber grating sensing optical fibers in all the steel stranded wires in each cross along the multi-cross-concrete beam are connected in series;
s4, connecting a strain optical fiber lead wire and a temperature optical fiber lead wire of the initial section or the final section of the steel strand which are connected in series with a demodulation unit, enabling the demodulation unit to emit 1510-1590 nm bandwidth light beams, enabling the light beams to enter a temperature optical fiber grating sensing optical fiber and a strain optical fiber grating sensing optical fiber, enabling each grating to reflect light beams back into the demodulation unit according to time difference and wavelength of received light signals after the light beams sequentially pass through each grating, and enabling the demodulation unit to record wavelength signal changes of each grating one by one to form electric signals for storage, so that demodulation is achieved;
and the data processing unit calculates the prestress value of each cross-concrete beam according to the electric signals of each grating.
7. The method for on-line monitoring of prestress of multi-span concrete beams based on fiber bragg grating sensing according to claim 6, wherein after the completion of the serial connection of the temperature fiber bragg grating sensing fiber and the strain fiber bragg grating sensing fiber in all steel strands in each span along the multi-span concrete beams in S3, concrete beam joints can be poured, and a plurality of concrete beams are changed into continuous concrete beams.
8. The method for on-line monitoring of prestress of multi-span concrete beams based on fiber grating sensing according to claim 6, wherein the data processing unit calculates prestress value of each span concrete beam according to electric signals of each grating, wherein,
when the data processing unit directly processes the strain fiber grating wavelength signal into a concrete beam prestress value, the following formula is adopted:
f i ＝X i *K i
the fusion algorithm considering the temperature fiber grating wavelength signal compensation is as follows:
F i ＝(X i -T i )*K i
in the above, f i The prestress value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; x is X i The wavelength variation value of the ith strain grating measuring point of the multi-span concrete Liang Yancheng; k (K) i The corresponding value of the wavelength and the cable force of the corresponding steel strand of the ith strain grating measuring point of the multi-span concrete Liang Yancheng is calibrated in a factory; f (F) i Taking the prestress value after temperature compensation into consideration for the ith strain grating measuring point of the multi-span concrete Liang Yancheng; t (T) i The wavelength change value of the ith temperature grating measuring point of the multi-span concrete Liang Yancheng.
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