Integrated monitoring device and method for prestressing and hole defects of new structures

Abstract

The present invention discloses an integrated monitoring device and method for prestress and duct defects of a newly constructed structure. The device includes an integrated monitoring sensor embedded in a concrete structure. The integrated monitoring sensor is wrapped around the periphery of the prestressed tendon in the form of a sleeve and arranged in an array along the length direction of the prestressed tendon. The sensor can simultaneously realize the functions of an electromagnetic elastic absolute stress sensor and a magnetostrictive ultrasonic guided wave transducer. The outer coil in the sensor can simultaneously serve as an excitation coil of the electromagnetic elastic absolute stress sensor and a bias magnetization coil of the magnetostrictive ultrasonic guided wave transducer. The magnetoelectric conversion element is used to collect the magnetic characteristic signal of the prestressed tendon to be measured. The inner coil is used to excite and receive ultrasonic guided waves. The reflection and transmission signals between different sensors can be compared to realize damage location and quantification. The present invention can simultaneously measure various damages, stresses and other information inside the component, and has the characteristics of convenient operation, long-term monitoring, and high monitoring accuracy.

Description

Technical Field

[0001] The invention belongs to the technical field of nondestructive testing of civil engineering, and in particular relates to a device and method for integrated monitoring of prestress and duct defects of a newly constructed structure. Background Art

[0002] Internal prestressed concrete structures are common in engineering, and the health status of the prestress has attracted much attention, mainly including damage detection and measurement of prestress size.

[0003] For monitoring internal defects in the pores of prestressed concrete structures, the Chinese invention patent technology with publication number CN118169246A uses a point-contact ultrasonic probe to divide the anchor area from the outside to the inside, and uses the abnormal amplitude of the reflected wave to determine the broken wires and corrosion damage of the anchor area cables, but does not locate the damage. The Chinese patent application technology with publication number CN106855539A determines the length of the debonding area based on the echo time and group velocity, but does not achieve positioning. In practice, prestressed tendons may have grouting voids and rust at the same time. How to jointly monitor the degree of damage of both is a difficult problem, and no relevant research has been seen so far.

[0004] In addition, the current detection methods mainly conduct separate detection of the prestress and damage of prestressed tendons, and cannot achieve simultaneous detection. Moreover, for the measurement of absolute stress of prestressed tendons, the electromagnetic elastic absolute stress sensor has higher accuracy; for prestressed tendon damage detection, the ultrasonic guided wave method has higher accuracy.

[0005] Therefore, we need to develop sensors that have fast detection speed, good working performance and integrate the dual functions of stress and damage detection for newly built prestressed concrete structures. Summary of the invention

[0006] In view of the above, the present invention provides an integrated monitoring device and method for prestress and hole defects of a newly built structure, which can solve the problems of insufficient detection accuracy of prestressed tendons inside the structure and difficulty in damage detection, and realizes the unification of electromagnetic elastic absolute stress sensors and magnetostrictive sensors, so that they have the dual functions of stress detection and damage detection, thereby improving detection efficiency.

[0007] An integrated monitoring device for prestressing and pore defects of a newly constructed structure comprises an integrated monitoring sensor embedded in a concrete structure. The integrated monitoring sensor is wrapped around the periphery of the prestressed tendons in the form of a sleeve and arranged in an array along the length direction of the prestressed tendons. The integrated monitoring sensor can simultaneously realize the functions of an electromagnetic elastic absolute stress sensor and a magnetostrictive ultrasonic guided wave transducer.

[0008] Furthermore, the integrated monitoring sensor includes a coil frame, an inner coil, an outer coil and a magneto-electric conversion element which are sleeved on the prestressed tendons, wherein the inner coil and the outer coil are both wound on the coil frame, and the magneto-electric conversion element is sleeved on the coil frame and is located between the inner coil and the outer coil.

[0009] Furthermore, the magnetoelectric conversion element is used as part of the electromagnetic elastic absolute stress sensor to collect magnetic characteristic signals of the prestressed tendons under the action of DC pulses; the outer coil is used as the excitation coil of the electromagnetic elastic absolute stress sensor and is also the bias magnetization coil of the magnetostrictive ultrasonic guided wave transducer; the inner coil is used as part of the magnetostrictive ultrasonic guided wave transducer to excite and receive ultrasonic guided waves.

[0010] Furthermore, the integrated monitoring sensor is in the shape of a circular sleeve, and both the inner and outer coils are solenoid coils, and are wound on a coil frame using pure copper enameled wire, and the number of turns and layers of the coil are designed in advance according to the ultrasonic guided wave frequency and detection signal amplitude required during detection.

[0011] Furthermore, the prestress and damage joint monitoring device also includes a host computer, which is used to analyze the signal characteristics of the ultrasonic guided waves received by the inner coil of each integrated monitoring sensor, so as to locate and quantitatively monitor the damage of the prestressed tendons; at the same time, based on the magnetic characteristic signals collected by the magnetoelectric conversion elements of each integrated monitoring sensor and the relationship between the prestress size and the magnetic characteristic signals, the prestress levels at different positions of the prestressed tendons to be tested are calculated.

[0012] The monitoring method of the above-mentioned integrated monitoring device for prestress and pore defects of newly built structures is as follows: when only one DC pulse is applied to the outer coil in the integrated monitoring sensor, the integrated monitoring sensor simultaneously realizes the functions of an electromagnetic elastic absolute stress sensor and a magnetostrictive ultrasonic guided wave transducer. Specifically, a DC pulse is first applied to the outer coil. When the integrated monitoring sensor is used as an electromagnetic elastic absolute stress sensor, a magnetoelectric conversion element is used to collect the magnetic characteristic signal of the prestressed tendon to be measured, and then the prestress level of the prestressed tendon to be measured is calculated according to the relationship curve between the prestress size and the magnetic characteristic signal; during the period of the DC pulse, a burst AC signal is applied to the inner coil, so that the integrated monitoring sensor is used as a magnetostrictive ultrasonic guided wave transducer, that is, the inner coil uses the magnetostrictive effect to excite ultrasonic guided waves in the prestressed tendon to be measured, and by comparing the transmitted wave signals between different sensors and the corresponding signals in a lossless state, the positioning and quantitative monitoring of the damage to the prestressed tendon to be measured is realized.

[0013] Furthermore, when the prestressed tendon to be tested has corrosion damage and the damage is located between two adjacent integrated monitoring sensors a and b, part of the ultrasonic guided wave energy emitted by the inner coil of the integrated monitoring sensor a is reflected at the damage, thereby reducing the ultrasonic guided wave energy transmitted from the damage. The more severe the corrosion is, the smaller the transmitted ultrasonic guided wave energy is. Combined with the arrival time of the reflected wave signal and the group velocity of the ultrasonic guided wave transmission in the prestressed tendon to be tested, the corrosion damage of the prestressed tendon to be tested can be located and monitored. At the same time, the inner coil of the integrated monitoring sensor b is used to receive the peak value of the transmitted wave signal, and compared with the peak value of the transmitted wave signal in the lossless state to obtain the corrosion degree coefficient, thereby quantitatively monitoring the corrosion damage of the prestressed tendon to be tested.

[0014] Furthermore, when a grouting cavity is generated in the prestressed tendon to be tested and the cavity is located between two adjacent integrated monitoring sensors a and b, the ultrasonic guided wave emitted by the inner coil of the integrated monitoring sensor a will be reflected at the interface generated by the cavity. Combined with the arrival time of the reflected wave signal and the group velocity of the ultrasonic guided wave transmission in the prestressed tendon to be tested, the grouting cavity of the prestressed tendon to be tested can be located and monitored; at the same time, the cavity will reduce the ultrasonic guided wave energy scattered into the surrounding concrete and increase the ultrasonic guided wave energy transmitted to the integrated monitoring sensor b. The peak value of the transmitted wave signal is received by the inner coil of the integrated monitoring sensor b, and compared with the peak value of the transmitted wave signal in the non-destructive case to obtain the grouting density coefficient, thereby quantitatively monitoring the grouting density of the prestressed tendon to be tested.

[0015] Furthermore, in the area where grouting voids occur, the prestressed tendons to be tested are in a non-anchored state, which increases the group velocity of ultrasonic guided wave transmission. The arrival time t1 of the transmission wave signal received by the inner coil of the integrated monitoring sensor b is combined with the group velocity of ultrasonic guided wave transmission in the prestressed tendons to be tested in the anchored and free states, thereby monitoring the length of the grouting voids of the prestressed tendons to be tested. The specific calculation expression is as follows:

[0016] t1=L a / v a +L fm / v f , L=L a +L fm

[0017] Where: L fm is the length of the grouting cavity, L a is the length of the anchorage section of the prestressed tendon to be tested under cavity damage, L is the length between the integrated monitoring sensors a and b, v a is the group velocity of ultrasonic guided waves in the prestressed tendons to be tested in the anchored state, v f is the group velocity of ultrasonic guided waves in the prestressed tendons to be tested in the free state.

[0018] Based on the above technical solution, the present invention has the following beneficial technical effects:

[0019] 1. The integrated monitoring sensor proposed in the present invention can simultaneously monitor the prestressing level and corrosion and grouting cavity damage, solving the current technical problems in the field.

[0020] 2. The integrated monitoring sensor proposed in the present invention can realize the dual functions of the electromagnetic bomb sensor and the retractable sensor within the time of applying only one DC pulse, which greatly shortens the detection time and reduces the energy consumption of the sensor.

[0021] 3. The present invention embeds the sensor into the prestressed concrete structure by pre-embedding. The position of the sensor is fixed and there is no need to move it repeatedly, so long-term monitoring can be achieved.

[0022] 4. The present invention can detect the prestress level at different positions of the prestressed tendons inside the prestressed concrete by arranging sensors in an array, thereby reflecting the prestressed service status of the entire structure.

[0023] 5. The present invention solves the problem of rapid energy attenuation and limited detection distance of ultrasonic guided waves in anchoring components by arranging sensors in an array.

[0024] 6. The monitoring method of the present invention has a simple process, is easy to operate, has low cost, can be applied to prestressed concrete structures of different specifications, has strong applicability, and is conducive to popularization and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a structural schematic diagram of the prestress and damage combined monitoring sensor of the present invention.

[0026] Figure 2 It is a schematic diagram of the arrangement of the prestress and damage joint monitoring sensor of the present invention in the component to be tested.

[0027] Figure 3 It is a schematic flow chart of the integrated monitoring method for prestressing and pore defects of a newly constructed structure according to the present invention.

[0028] Figure 4 It is a calibration curve diagram of the magnetic characteristic signal of the prestressed tendon and the prestress size in the verification example of the present invention.

[0029] Figure 5 Schematic diagram of direct wave signals under lossless and different lossy conditions in the verification example of the present invention.

[0030] In the figure: 1—ultrasonic guided wave, 2—rust damage, 3—grouting cavity damage, 4—integrated monitoring sensor, 5—prestressed tendons, 6—coil skeleton, 7—inner coil, 8—magnetoelectric conversion element, 9—outer coil, 10—sensor protection cover. DETAILED DESCRIPTION

[0031] In order to describe the present invention more specifically, the technical solution of the present invention is described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0032] like Figure 2 As shown, the integrated monitoring device for prestress and pore defects of the newly constructed structure of the present invention includes a plurality of integrated monitoring sensors 4 for joint monitoring of prestress and damage. The integrated monitoring sensors 4 are embedded in the concrete structure, wrapped around the periphery of the prestressed tendons 5 in the form of sleeves and arranged at intervals along the length direction of the prestressed tendons 5. The integrated monitoring sensors 4 can simultaneously realize the functions of an electromagnetic elastic absolute stress sensor and a magnetostrictive ultrasonic guided wave transducer, and have a plurality of working modes such as pulse echo, single-transmit single-receive, and single-transmit multiple-receive.

[0033] like Figure 1 As shown, the integrated monitoring sensor 4 is mainly composed of a coil skeleton 6, an inner coil 7, a magnetoelectric conversion element 8, an outer coil 9, a sensor protection cover 10 and other parts, wherein the outer coil 9 (main coil) can be used as an excitation coil of the electromagnetic elastic absolute stress sensor and a bias magnetization coil of the magnetostrictive ultrasonic guided wave transducer at the same time, the magnetoelectric conversion element 8 as a part of the electromagnetic elastic absolute stress sensor is used to receive the magnetic characteristic signal of the prestressed tendon 5, and the inner coil 7 (auxiliary coil) as a part of the magnetostrictive ultrasonic guided wave transducer is used to excite and receive the ultrasonic guided wave 1, and the number of turns and layers of the coil can be designed in advance according to the ultrasonic guided wave frequency and detection signal amplitude required during detection.

[0034] The integrated monitoring sensor 4 has a circular sleeve shape and is wrapped around the periphery of the prestressed tendon 5. The outer coil 9 and the inner coil 7 are both solenoid coils and are wound on the sensor coil frame 6 with pure copper enameled wire. The wire diameter of the outer coil is 0.57 mm, and the wire diameter of the inner coil is 1 mm. The width of the outer coil 9 is greater than that of the inner coil 7 to ensure the uniformity of the excitation / bias magnetic field at the inner coil 7, and the outer coil 9, the inner coil 7, and the magnetoelectric conversion element 8 are all arranged at the center of the integrated monitoring sensor 4.

[0035] like Figure 3 As shown, the implementation process of the integrated monitoring method for prestressing and duct defects of the newly constructed structure of the present invention is as follows:

[0036] First, determine the model of the component to be tested, and complete the design and production of the integrated monitoring sensor in advance according to the specifications of the prestressed tendon to be tested, including the number of layers and turns of the inner coil 7 and the outer coil 9, the inner and outer diameters of the magnetoelectric conversion element 8 and the coil skeleton 6, etc., to ensure that when installed on the prestressed tendon 5 to be tested, the inner wall of the integrated monitoring sensor 4 fits tightly with the prestressed tendon 5 (that is, the inner diameter of the sensor 4 is equal to the outer diameter of the prestressed tendon 5 to be tested), to ensure the working performance of the integrated monitoring sensor 4 during stress measurement and damage detection, and to prevent the influence of coil parameters and lifting distance on the quality intensity of the measurement signal.

[0037] An integrated monitoring sensor 4 is installed on the prestressed tendon standard sample, and the magnetoelectric conversion element 8 collects magnetic characteristic signals under different prestressed tendon stress levels, that is, a hydraulic jack is used to apply prestress to the prestressed tendon standard sample step by step, and the magnetic characteristic signals under each level of prestress load are recorded; then, a relationship curve between the prestress size and the magnetic characteristic signal is obtained by fitting according to the prestress size and its corresponding magnetic characteristic signal.

[0038] Since the prestressed tendon standard sample and the prestressed tendon 5 to be tested are products of the same specifications, an integrated monitoring sensor 4 is used to be sleeved on the periphery of the prestressed tendon 5 to be tested during actual measurement. The built-in outer coil 9 completes the excitation function, and the magneto-electric conversion element 8 completes the function of receiving the magnetic characteristic signal. The magnetic characteristic signal of the prestressed tendon 5 to be tested is acquired and combined with the above-mentioned relationship curve to obtain the prestress level of the prestressed tendon 5 to be tested.

[0039] At the same time, the prestressed concrete specimens are cast in advance, and integrated monitoring sensors are embedded in the array inside the specimens (with the same sensor spacing) to obtain the direct wave signals of adjacent sensors in a non-destructive manner and calibrate the group velocity of ultrasonic guided waves in the anchored and free states.

[0040] During the specific implementation process, the integrated monitoring sensor is wrapped around the periphery of the prestressed tendon to be tested and arranged in an array along the elongation direction of the prestressed tendon (the sensor arrangement spacing is the same as that during measurement), waiting for the component to complete prestressing and casting.

[0041] The working mode of the integrated monitoring sensor 4 in this embodiment is as follows:

[0042] First, a DC pulse is applied to the outer coil 9, and the magnetoelectric conversion element 8 is used to collect the magnetic characteristic signal of the prestressed tendon 5 to be tested, and then the prestress value of the prestressed tendon 5 to be tested is calculated according to the relationship curve between the prestress size and the magnetic characteristic signal; and during the period of the DC pulse, a burst AC signal is applied to the inner coil 7, and the inner coil 7 uses the magnetostrictive effect to excite the ultrasonic guided wave 1 in the prestressed tendon 5 to be tested. The upper computer determines the degree of damage to the structure of the prestressed tendon 5 to be tested by analyzing the characteristics of the reflected wave and the transmitted wave signals. The power-on time of the DC pulse needs to be greater than the total time of transmitting and receiving the guided wave signal.

[0043] When measuring the stress of the prestressed tendon 5, the stress values ​​at different positions can be obtained through the magnetic characteristic signals of sensors arranged at different positions (1, 2, ..., n, where n is the number of arranged sensors) in the array; when measuring component damage, sensor i is used to transmit ultrasonic guided wave 1, and sensors i-1 and i+1 (i = 2, 3, 4, ..., n-1) receive ultrasonic guided wave 1. By comparing the difference between the two received signals, the quantification and positioning of the damage can be achieved.

[0044] like Figure 2 As shown, when the prestressed tendon 5 to be tested has corrosion damage, part of the ultrasonic guided wave energy emitted by the inner coil 7 of the sensor i is reflected at the corrosion damage site 2, thereby reducing the ultrasonic guided wave energy transmitted from the corrosion damage site 2. The more serious the corrosion, the smaller the transmitted ultrasonic guided wave energy. The upper computer combines the arrival time of the reflected wave signal received by the inner coil 7 of the sensor i and the group velocity transmitted by the ultrasonic guided wave 1 in the prestressed tendon 5 to be tested, and can locate and monitor the corrosion damage site 2 of the prestressed tendon 5 to be tested; at the same time, the upper computer uses the inner coil 7 of the sensor i-1 to receive the peak value of the transmitted wave signal, and compares it with the peak value of the transmitted wave signal received by the inner coil 7 of the sensor i-1 in the lossless state to obtain the corrosion degree coefficient, so as to quantitatively monitor the corrosion damage of the prestressed tendon 5 to be tested.

[0045] like Figure 2 As shown, in the grouting cavity damage area 3, the prestressed tendon 5 to be tested is in a non-anchored state, which will increase the group velocity of the ultrasonic guided wave 1. The host computer receives the arrival time t1 of the transmission wave signal through the inner coil 7 of the sensor i+1. Combined with the group velocity of the ultrasonic guided wave 1 transmitted in the prestressed tendon 5 to be tested in the anchored and free states, the grouting cavity length of the prestressed tendon 5 to be tested is monitored. The specific calculation expression is as follows:

[0046] t1=L a / v a +L fm / v f , L=L a +L fm

[0047] Where: L fm is the length of the grouting cavity, L a is the length of the anchorage section of the prestressed tendon 5 to be tested under cavity damage, L is the length between sensor i and sensor i+1, v a is the transmission group velocity of the ultrasonic guided wave 1 in the prestressed tendon 5 to be tested in the anchored state, v f It is the transmission group velocity of the ultrasonic guided wave 1 in the prestressed tendon 5 to be tested in the free state.

[0048] like Figure 2As shown, when a grouting cavity is generated in the prestressed tendon 5 to be tested, the ultrasonic guided wave 1 emitted by the inner coil 7 of the sensor i will be reflected at the interface generated at the grouting cavity damage 3. The host computer can locate and monitor the grouting cavity damage 3 of the prestressed tendon 5 to be tested by combining the arrival time of the reflected wave signal received by the inner coil 7 of the sensor i and the group velocity transmitted by the ultrasonic guided wave 1 in the prestressed tendon 5 to be tested; at the same time, the cavity will reduce the ultrasonic guided wave energy scattered into the surrounding concrete and increase the ultrasonic guided wave energy transmitted to the sensor i+1. The host computer uses the inner coil 7 of the sensor i+1 to receive the peak value of the transmitted wave signal, and compares it with the peak value of the transmitted wave signal received by the inner coil 7 of the sensor i+1 in the lossless condition to obtain the grouting density coefficient, so as to quantitatively monitor the grouting density of the prestressed tendon 5 to be tested.

[0049] Verification Example

[0050] We selected a steel strand with an outer diameter of 15.2mm, a length of 3m, a density of 7850kg / m3, an elastic modulus of 209Gpa, and a Poisson's ratio of 0.29; the concrete beam material is C40, with a cross-sectional size of 0.1m*0.1m and a length of 2.8m. Three integrated monitoring sensors are arranged on the prestressed concrete steel bars in the beam, numbered ①②③, and the sensor spacing is 1.2m. A 0.1m uniform rust damage is embedded between sensors ① and ② (using electrochemical corrosion, the steel bars are corroded for one week before the test piece is made), and a 0.6m grouting cavity is embedded between sensors ② and ③. Then the sensor is calibrated in advance to determine the relationship between the magnetic characteristic signal and the prestress of this model of steel strand. The calibration curve is shown below. Figure 4 As shown in the figure, a 3-cycle Hanning window modulated sine wave with a center frequency of 15kHz is selected as the excitation signal, and the direct wave signal of the L(0,1) mode of the adjacent sensors in the lossless state is obtained, and the group velocity of the ultrasonic guided wave L(0,1) mode transmitted in the anchored state and free state in the steel strand is calibrated to be 3165m / s and 4987m / s respectively. The ultrasonic guided wave is excited in sensor ②, and the ultrasonic guided wave signal is received by sensors ① and ③. The measured signal is as follows Figure 5 shown.

[0051] Under the above conditions, the wave packet arrival time of sensor ① is 0.37ms, which is close to the lossless signal, and it is judged that there is no grouting cavity damage; the wave packet arrival time of sensor ③ is 3.11ms, and the grouting cavity length calculated according to the formula is 0.59m, which is close to the length of the pre-buried grouting cavity, indicating the effectiveness of the algorithm of the present invention. The amplitude of the lossless signal is 2.50, the direct wave amplitude of sensor ① is 1.34, and the direct wave amplitude received by sensor ③ is 3.16. The corrosion degree coefficient is 0.536 and the grouting density coefficient is 1.264. The smaller the calculated corrosion degree, the more serious the corrosion damage, and the smaller the calculated grouting density coefficient, the higher the grouting density.

[0052] The above description of the embodiments is to facilitate the understanding and application of the present invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments. Improvements and modifications made by those skilled in the art to the present invention based on the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A new structure prestressing and duct defect integrated monitoring device, characterized by: It includes an integrated monitoring sensor embedded in the concrete structure, which is wrapped around the periphery of the prestressed tendon in the form of a sleeve and arranged in an array along the length direction of the prestressed tendon, and can simultaneously realize the functions of an electromagnetic elastic absolute stress sensor and a magnetostrictive ultrasonic guided wave transducer; The integrated monitoring sensor comprises a coil frame, an inner coil, an outer coil and a magnetoelectric conversion element sleeved on the prestressed tendon, wherein the inner coil and the outer coil are both wound on the coil frame, and the magnetoelectric conversion element is sleeved on the coil frame and located between the inner coil and the outer coil; The magnetoelectric conversion element is used as a part of the electromagnetic elastic absolute stress sensor to collect the magnetic characteristic signal of the prestressed tendon under the action of a DC pulse; the outer coil is used as the excitation coil of the electromagnetic elastic absolute stress sensor and is also the bias magnetization coil of the magnetostrictive ultrasonic guided wave transducer; the inner coil is used as a part of the magnetostrictive ultrasonic guided wave transducer to excite and receive ultrasonic guided waves.

2. The integrated monitoring device for prestressing and hole defects of a newly constructed structure according to claim 1 is characterized by: The integrated monitoring sensor is in the shape of a circular sleeve, and both the inner and outer coils are solenoid coils, and are wound on a coil frame with pure copper enameled wire. The number of turns and layers of the coil are designed in advance according to the ultrasonic guided wave frequency and detection signal amplitude required during detection.

3. The integrated monitoring device for prestressing and hole defects of a newly constructed structure according to claim 1 is characterized by: The integrated monitoring device also includes a host computer, which is used to analyze the signal characteristics of the ultrasonic guided waves received by the inner coil of each integrated monitoring sensor, so as to locate and quantitatively monitor the damage of the prestressed tendons; at the same time, based on the magnetic characteristic signals collected by the magnetoelectric conversion elements of each integrated monitoring sensor and the relationship between the prestress size and the magnetic characteristic signals, the prestress levels at different positions of the prestressed tendons to be tested are calculated.

4. A monitoring method for the integrated monitoring device for prestressing and duct defects of a newly constructed structure according to any one of claims 1 to 3, characterized in that: When only one DC pulse is applied to the outer coil in the integrated monitoring sensor, the integrated monitoring sensor can realize the functions of an electromagnetic elastic absolute stress sensor and a magnetostrictive ultrasonic guided wave transducer at the same time. Specifically: first, a DC pulse is applied to the outer coil. When the integrated monitoring sensor is used as an electromagnetic elastic absolute stress sensor, a magnetoelectric conversion element is used to collect the magnetic characteristic signal of the prestressed tendon to be measured, and then the prestress level of the prestressed tendon to be measured is calculated according to the relationship curve between the prestress size and the magnetic characteristic signal; during the DC pulse, a burst AC signal is applied to the inner coil, so that the integrated monitoring sensor is used as a magnetostrictive ultrasonic guided wave transducer, that is, the inner coil uses the magnetostrictive effect to excite ultrasonic guided waves in the prestressed tendon to be measured, and by comparing the transmitted wave signals between different sensors and the corresponding signals in a lossless state, the positioning and quantitative monitoring of the damage of the prestressed tendon to be measured is achieved.

5. The monitoring method according to claim 4, characterized in that: When the prestressed tendon to be tested has corrosion damage and the damage is located between two adjacent integrated monitoring sensors a and b, part of the ultrasonic guided wave energy emitted by the inner coil of the integrated monitoring sensor a is reflected at the damage, thereby reducing the ultrasonic guided wave energy transmitted from the damage. The more serious the corrosion is, the smaller the transmitted ultrasonic guided wave energy is. Combined with the arrival time of the reflected wave signal and the group velocity of the ultrasonic guided wave transmission in the prestressed tendon to be tested, the corrosion damage of the prestressed tendon to be tested can be located and monitored. At the same time, the peak value of the transmitted wave signal is received by the inner coil of the integrated monitoring sensor b, and compared with the peak value of the transmitted wave signal in the lossless case to obtain the corrosion degree coefficient, so as to quantitatively monitor the corrosion damage of the prestressed tendon to be tested.

6. The monitoring method according to claim 4, characterized in that: When a grouting cavity is generated in the prestressed tendon to be tested and the cavity is located between two adjacent integrated monitoring sensors a and b, the ultrasonic guided wave emitted by the inner coil of the integrated monitoring sensor a will be reflected at the interface generated by the cavity. Combined with the arrival time of the reflected wave signal and the group velocity of the ultrasonic guided wave transmission in the prestressed tendon to be tested, the grouting cavity of the prestressed tendon to be tested can be located and monitored. At the same time, the cavity will reduce the ultrasonic guided wave energy scattered into the surrounding concrete and increase the ultrasonic guided wave energy transmitted to the integrated monitoring sensor b. The peak value of the transmitted wave signal is received by the inner coil of the integrated monitoring sensor b, and compared with the peak value of the transmitted wave signal in the non-destructive case to obtain the grouting density coefficient, so as to quantitatively monitor the grouting density of the prestressed tendon to be tested.

7. The monitoring method according to claim 6, characterized in that: In the area where grouting voids occur, the prestressed tendons to be tested are in a non-anchored state, which increases the group velocity of ultrasonic guided wave transmission. The arrival time t1 of the transmitted wave signal received by the inner coil of the integrated monitoring sensor b is combined with the group velocity of ultrasonic guided wave transmission in the prestressed tendons to be tested in the anchored and free states, so as to monitor the length of the grouting voids of the prestressed tendons to be tested. The specific calculation expression is as follows: t1=L a / v a +L fm / v f ,L=L a +L fm Where: L fm is the length of the grouting cavity, L a is the length of the anchorage section of the prestressed tendon to be tested under cavity damage, L is the length between the integrated monitoring sensors a and b, v a is the group velocity of ultrasonic guided waves in the prestressed tendons to be tested in the anchored state, v f is the group velocity of ultrasonic guided waves in the prestressed tendons to be tested in the free state.

Images