Electromagnetic elastic absolute strain monitoring device and method

Abstract

The invention discloses an electromagnetic elastic type absolute strain monitoring device and method. The device comprises a stress element, an electromagnetic elastic type absolute stress sensor and a magnetoelastic instrument, the method comprises the following steps: determining an absolute strain monitoring position according to a monitoring requirement, pouring a structural body, burying a stress element and a sensor at a corresponding position, calculating absolute stress generated by the stress element due to cooperative deformation according to a signal collected by the sensor during working, and calculating the absolute stress of the stress element according to a constitutive relation of the stress element. And the absolute stress of the stressed element can be converted into absolute strain. Meshing threads are machined on the surface of the stress element, supporting connectors are arranged at the two ends of the stress element, the stress element and the structural body can cooperatively deform without sliding, and therefore the absolute strain of the stress element is the absolute strain of the structural body of the tested area. The absolute strain is directly monitored, compared with a traditional relative strain monitoring method, the precision is higher, the service life is longer, the anti-risk capacity is higher, the installation survival rate is high, the influence of the environment is small, and long-term absolute strain monitoring can be achieved.

Description

Technical Field

[0001] The present invention belongs to the technical field of civil engineering structure health monitoring, and in particular relates to an electromagnetic elastic absolute strain monitoring device and method. Background Art

[0002] During use, engineering structures are affected by various environmental factors such as loads, wind, complex geological conditions, and other interference factors, resulting in varying degrees of static and dynamic deformation. When the deformation of an engineering structure exceeds the specified limit, it will affect its normal use, and in severe cases, it may cause structural failure and endanger human life. For example, the famous Quebec Bridge in Canada collapsed due to excessive strain during installation due to an error in the calculation of strain, causing huge losses. Therefore, it is particularly important to conduct long-term and accurate monitoring of the deformation of engineering structures under construction and in use. Strain, as a very important indicator of structural deformation, is generally very small in value and is difficult to monitor in large-scale structures. Therefore, various strain sensors are needed; however, the monitoring accuracy, continuity, and installation convenience of various sensors are all very important and urgent issues to be addressed.

[0003] Existing strain monitoring equipment has some key issues to be resolved when monitoring absolute strain. For example, Chinese patent application publication number CN107367339A proposes an absolute strain detection method and a dedicated strip pattern. It uses the change in resistance of a metal conductor when it is strained to monitor structural strain. Before monitoring strain, the resistance strain gauge must first be bridge balanced. If the bridge is balanced at the moment of zero strain, the absolute strain can be measured. However, unpredictable power outages will cause the bridge to rebalance, and the strain measured thereafter will be relative strain. The existing technology does not mention how to overcome the rebalancing problem after a power outage. Even in short-term testing, assuming that the bridge rebalancing problem caused by power outages does not occur, this method requires the strip specimen with the strain gauge attached to it to be completely cut and separated from the surface of the concrete structure, which not only destroys the structure to be tested, but is also very cumbersome and inefficient. Chinese patent application publication number CN221404224U proposes a vibrating-wire strain gauge that uses changes in the vibration frequency of a tensioned wire to monitor structural strain. Theoretically, absolute strain can be measured as long as the structural strain is zero during installation. However, metal wires can fatigue under long-term tension, affecting the accuracy and long-term stability of strain monitoring. Furthermore, the installation process of vibrating-wire strain gauges is complex, with strict requirements on the installation environment, and precise fixation is required to ensure measurement accuracy.

[0004] In addition, a Chinese patent application with publication number CN118347420A proposes a method for indirectly measuring the deflection of a bridge mid-span through strain measurement. The method uses a fiber Bragg grating (FBG) strain sensor to contact-measure the absolute strain at the bridge mid-span. Although the fiber Bragg grating (FBG) strain sensor can ensure accuracy and stability, it is prone to breakage when embedded in concrete and is prone to breakage under large deformation when installed on the outside of concrete to measure strain. It has a low survival rate and is relatively expensive.

[0005] Therefore, it is an urgent need to develop a concrete absolute strain monitoring device with high precision, long-term stability and low cost. Summary of the Invention

[0006] In view of the above, the present invention provides an electromagnetic elastic absolute strain monitoring device and method, which can overcome the shortcomings of traditional strain monitoring sensors, such as short life and inability to perform long-term monitoring, and can more accurately monitor the absolute strain within the allowable error range of the engineering project without the need for complex calculations. It has a simple principle, high monitoring efficiency, and can achieve long-term continuous monitoring, providing a simple and efficient absolute strain monitoring solution for bridge projects with high strain monitoring requirements.

[0007] An electromagnetic elastic absolute strain monitoring device, comprising: The force-bearing element is embedded in the structure of the measured area (such as concrete) or welded (or pasted) to the surface of the structure of the measured area, and is consistent with the force direction of the structure of the measured area; The electromagnetic elastic absolute stress sensor is installed on the stress-bearing element and is used to collect the magnetic characteristic electrical signal at the stress-bearing element; The magnetoelastic instrument calculates and determines the absolute stress of the load-bearing element based on the magnetic characteristic electrical signal, and then converts the absolute stress of the load-bearing element into the absolute strain of the structure in the measured area based on the constitutive relationship of the load-bearing element calibrated in the laboratory.

[0008] Furthermore, the electromagnetic elastic absolute stress sensor includes a supporting frame and a magnetic field generating element and a magnetoelectric sensing element fixed on the supporting frame. The magnetic field generating element is controlled by the magnetoelastic instrument and is used to generate a magnetic field in the measured area, thereby magnetizing the force-bearing element; the magnetoelectric sensing element generates a magnetic characteristic electrical signal representing the magnetic induction intensity at the force-bearing element through electromagnetic induction.

[0009] In order to ensure that the electromagnetic elastic absolute stress sensor can accurately measure the absolute stress of the stress-bearing element, the stress-bearing element is further made of steel wire, steel strand or screw (with a smaller diameter), and is in an elastic stage inside or on the surface of the structure in the measured area, which can avoid the influence of the plastic area on the measurement results.

[0010] In order to ensure that the absolute strain of the load-bearing element is the absolute strain of the structure, measures need to be taken to ensure sufficient contact between the structure and the load-bearing element and no relative slippage occurs; further, the load-bearing element is processed with interlocking threads to increase the interlocking force and resistance between the structure and the element surface.

[0011] In order to ensure the integrity of the force-bearing element and the structure and avoid slippage, further, support joints are fixed at both ends of the force-bearing element to limit its slippage along the structure; if the force-bearing element is a steel wire or steel strand, the support joint can be made of steel plate welded with the steel wire or steel strand; if the force-bearing element is a screw, the support joint can be threaded with a nut.

[0012] Furthermore, the magnetoelastic instrument receives magnetic characteristic electrical signals collected from electromagnetic elastic absolute stress sensors, and calculates and determines the absolute stress of the stressed element based on the magnetic characteristic electrical signal curves of the stressed element under different stress magnitudes, and then converts the absolute stress into the absolute strain of the stressed element based on the constitutive relationship of the stressed element calibrated in the laboratory. Since there is a cooperative deformation relationship between the structure and the stressed element, the absolute strain of the stressed element is the absolute strain of the structure in the measured area.

[0013] Furthermore, the electromagnetic elastic absolute strain monitoring device also includes an information interaction device, through which the magnetic elastic instrument can transmit the absolute stress of the force-bearing element and the absolute strain of the structure in the measured area to the host computer for display for user viewing.

[0014] The application method of the electromagnetic elastic absolute strain monitoring device comprises the following steps: (1) Determine the absolute strain monitoring area based on the project monitoring requirements; (2) Using an electromagnetic elastic absolute stress sensor to collect the magnetic characteristic electrical signals at the stressed element under different stress magnitudes, the magnetic characteristic electrical signal curves of the stressed element under different stress magnitudes are obtained by fitting; (3) Casting a structure in the monitoring area and burying force-bearing elements and electromagnetic elastic absolute stress sensors at corresponding positions in the monitoring area during the process, or welding (or gluing) force-bearing elements on the surface of the structure and sleeve electromagnetic elastic absolute stress sensors on the force-bearing elements; (4) When the structure in the monitoring area is deformed by an external force, the magnetoelastic instrument receives the magnetic characteristic electric signal at the stress-bearing element collected by the electromagnetic elastic absolute stress sensor, and calculates and determines the absolute stress of the stress-bearing element based on the magnetic characteristic electric signal curve; (5) The magnetoelastic instrument converts the absolute stress into the absolute strain of the load-bearing element based on the constitutive relationship of the load-bearing element calibrated in the laboratory. Since there is a cooperative deformation relationship between the structure and the load-bearing element, the absolute strain of the load-bearing element is the absolute strain of the structure in the monitoring area.

[0015] Based on the above technical solution, the creativity of the present invention is mainly reflected in the following aspects: 1. The strain measured by this method is absolute strain. Compared to resistive strain gauges, since the relationship between absolute stress and magnetic characteristic quantities is pre-calibrated, even if power is suddenly turned off and on during monitoring, the relationship between absolute stress and magnetic characteristic quantities remains unchanged, without any impact on the monitoring results. The measured absolute strain of the structure remains, making it suitable for long-term monitoring and providing stable monitoring results.

[0016] 2. This invention transforms absolute strain monitoring of a structure into absolute strain monitoring of a load-bearing element. By specially treating the surface and boundaries of the load-bearing element, providing interlocking threads on the surface of the load-bearing element, and installing steel plates or nuts at both ends, the load-bearing element can be tightly connected to the structure, thereby achieving coordinated deformation. The absolute strain of the structure can be monitored by indirectly monitoring the absolute strain of the ferromagnetic element, providing a new approach to absolute strain monitoring of the structure.

[0017] 3. Since the sensor is directly embedded within the structure, the configured sensor can be directly embedded in a specific position of the structure during the casting process, making the installation process convenient. The structure can also be cleverly used as its own protective layer, eliminating the need for specially designed protective measures and minimizing environmental impact. Compared with sensors that are exposed to the environment for a long time, the sensor has a longer service life.

[0018] 4. Fiber Bragg gratings (FBGs) are inherently brittle materials and easily break under impact or excessive bending. Therefore, improper handling during embedment can easily lead to breakage and a low survival rate. Compared to embedded FBG strain sensors, the load-bearing elements used in this invention are primarily steel wire, stranded steel, or threaded rod. These elements are inherently stronger and are not subject to damage during sensor installation or structural casting, resulting in a high survival rate.

[0019] The present invention transforms absolute strain monitoring of a structure into absolute strain monitoring of a stress-bearing element by coordinating deformation between the stress-bearing element and the structure, thus proposing a simple and effective absolute strain monitoring method. Compared with the prior art, the present invention has at least the following beneficial technical effects: 1. Compared with vibrating-wire strain gauges, which monitor strain by measuring the frequency of a taut metal wire, this type of strain gauge is prone to fatigue. The present invention uses materials such as steel wire, stranded steel wire, or threaded rod, eliminating the need for pre-stretching during installation. Furthermore, because the absolute strain monitoring range remains within the elastic operating phase of the load-bearing element, fatigue is less likely to occur, resulting in high long-term stability.

[0020] 2. Compared with resistance strain gauges, resistance strain gauges require bridge balancing before measurement and rebalancing after power failure, which is difficult to achieve during the monitoring process. The absolute strain monitoring effect is poor and the risk resistance is weak. The present invention only requires simple calibration of the load-bearing element before installation to continuously and stably monitor absolute strain after installation. Even power failure will not affect the strain monitoring results, and the risk resistance is strong.

[0021] 3. Compared with embedded fiber Bragg grating strain sensors, fiber Bragg gratings are inherently brittle materials and easily break under impact or excessive bending. Therefore, if improperly handled during embedment, they are prone to breakage and have a low survival rate. The force-bearing elements used in the present invention are mainly steel wires, steel strands, or threaded rods. Therefore, they are inherently stronger, less susceptible to damage during installation, and have a higher survival rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 It is a structural schematic diagram of the electromagnetic elastic absolute strain monitoring device of the present invention.

[0023] Figure 2 Schematic diagram of the arrangement of sensors and force-bearing elements for an embodiment of absolute strain monitoring of concrete in the compression zone of a bridge.

[0024] Figure 3 The figure is a flow chart of a monitoring method using the electromagnetic elastic absolute strain monitoring device of the present invention.

[0025] Figure 4 This is a schematic diagram of the pressure-magnetic characteristic electrical signal calibration curve of the force-bearing element. F To calibrate the axial pressure applied to the load-bearing element, x is the magnetic characteristic electric signal, red is the calibration point, and blue is the fitting curve.

[0026] Figure 5 The diagram is a schematic diagram of the calibration curve of compressive stress-compressive strain of the load-bearing element. σ is the compressive stress of the load-bearing element, ε is the compressive strain under the corresponding stress, red is the calibration point, and blue is the fitting curve.

[0027] Figure 6 The diagram is a diagram showing the relationship between the compressive strain and the magnetic characteristic electric signal of the stressed element. ε is the strain of the load-bearing element, x Refers to the corresponding magnetic characteristic quantity, red is the calibration point, and blue is the fitting curve.

[0028] Figure 7 Schematic diagram comparing the monitoring results of the system of the present invention and the monitoring results of the vibrating wire strain gauge.

[0029] Figure 8 A schematic diagram of one of the embedding methods of an electromagnetic elastic absolute stress sensor. DETAILED DESCRIPTION

[0030] In order to describe the present invention more specifically, the technical solution of the present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0031] like Figure 1 As shown, the electromagnetic elastic absolute strain monitoring device of the present invention includes a force element 3-01, an electromagnetic elastic absolute stress sensor 3-04 and a magnetic elastic instrument 3-05, wherein the force element 3-01 is buried in the concrete of the measured area and is consistent with the force direction of the concrete in the measured area; the electromagnetic elastic absolute stress sensor 3-04 is installed on the force element 3-01 and is used to collect the magnetic characteristic electric signal at the force element 3-01; the magnetic elastic instrument 3-05 calculates and determines the absolute stress of the force element 3-01 based on the magnetic characteristic electric signal, and then converts the absolute stress of the force element 3-01 into the absolute strain σ of the concrete in the measured area based on the constitutive relationship of the force element 3-01 calibrated in the laboratory. S .

[0032] The load-bearing element 3-01 can be made of steel wire, steel strand, or a small-diameter screw rod, and is in the elastic phase within the concrete in the test area. Engaging threads 3-02 are machined on the load-bearing element 3-01 to increase the engagement and resistance between the concrete and the element surface. Support joints 3-03 are fixed at both ends to prevent slippage along the concrete. If the load-bearing element 3-01 is a steel wire or steel strand, the support joints 3-03 can be made of a steel plate welded to the wire or steel strand. If the load-bearing element 3-01 is a screw rod, the support joints 3-03 can be threaded with a nut.

[0033] The electromagnetic elastic absolute stress sensor 3-04 comprises a support frame, a magnetic field generating element, and a magnetoelectric sensing element mounted on the support frame. The magnetic field generating element, controlled by the magnetoelastic instrument 3-05, generates a magnetic field in the measured area, thereby magnetizing the force-bearing element 3-01. The magnetoelectric sensing element generates a magnetic characteristic electrical signal representing the magnetic field strength at the force-bearing element 3-01 through electromagnetic induction. The magnetic field generating element can be implemented using an excitation coil, and the magnetoelectric sensing element can be implemented using a Hall element. No external power supply or integration is required.

[0034] The magnetoelastic instrument 3-05 receives the magnetic characteristic electrical signal collected by the electromagnetic elastic absolute stress sensor 3-04, and calculates the absolute stress of the stressed element 3-01 based on the magnetic characteristic electrical signal curve of the stressed element 3-01 under different stress magnitudes. Then, based on the constitutive relationship of the stressed element 3-01 calibrated in the laboratory, the absolute stress is converted into the absolute strain of the stressed element 3-01. Due to the cooperative deformation relationship between the concrete and the stressed element 3-01, the absolute strain of the stressed element 3-01 is the absolute strain of the concrete in the measured area, and is finally displayed on the host computer through interaction.

[0035] The method flow for monitoring the absolute strain of concrete using the above system is as follows: Figure 3 As shown: In the preparation stage, appropriate load-bearing elements are selected based on the target concrete structure strain monitoring range. The requirements for load-bearing elements are as follows: ① Since the load-bearing elements need to deform in coordination with the concrete, they should be in the elastic stage within the rated strain range and not enter the plastic stage.

[0036] ②The load-bearing element needs to be a threaded steel wire, steel strand or screw.

[0037] Then, the electromagnetic elastic absolute stress sensor is mounted on the selected stress-bearing element, and the stress-bearing element is installed on the calibration frame and fixed at both ends with nuts; the sensor is connected to the magnetic elastic instrument, which has a temperature sensor inside; the sensor is energized, and pressure is applied to the stress-bearing element through the jack. At this time, the electromagnetic elastic absolute stress sensor receives the change in this characteristic, converts it into voltage data, and transmits it to the magnetic elastic instrument. Since the magnetic elastic instrument has an embedded calibration program, it will give the corresponding relationship between voltage and tension at a given temperature, thus completing the calibration work and obtaining the calibration curve of the pressure-magnetic characteristic electrical signal of the stress-bearing element as shown below. Figure 4 shown.

[0038] Then, constitutive tests are carried out on the load-bearing components and their stress-strain curves are plotted, such as Figure 5 It should be noted that in the above calibration process, the load-bearing element always deforms in the elastic stage, and plastic deformation cannot occur in the load-bearing element to avoid irreversible plastic strain.

[0039] After the above calibration, the relationship curve between strain of the force element and magnetic characteristic electric signal can be further obtained as follows: Figure 6 As shown, the calibration work before installation is completed.

[0040] During the pouring stage, the absolute strain monitoring position is first determined according to the monitoring requirements of the engineering project, the load-bearing element with the electromagnetic elastic absolute stress sensor is firmly tied to the corresponding position of the steel cage, and then the concrete is poured.

[0041] During the working stage, when the concrete deforms, the electromagnetic elastic absolute stress sensor is used to collect the magnetic characteristic electrical signal at the stress element and provide it to the magnetoelastic instrument. The magnetoelastic instrument calculates the absolute stress of the stress element based on the magnetic characteristic electrical signal curve of the stress element under different stress levels. , and then according to the constitutive relationship of the load-bearing element calibrated in the laboratory (i.e. stress and strain The absolute stress of the load-bearing element Converted into absolute strain of the load-bearing element ; Due to the cooperative deformation relationship between concrete and load-bearing elements, the absolute strain of the load-bearing elements The absolute strain of the concrete in the tested area is , and output the final result.

[0042] Example The electromagnetic elastic absolute strain monitoring device and method of the present invention can theoretically be used for absolute strain monitoring of any concrete structure or other material components. This embodiment uses the absolute strain monitoring of concrete in the tensile zone of a reinforced concrete bridge as an example. The arrangement of the various components and sensors in the system is as follows: Figure 2 As shown, the specific implementation is as follows: First, bury the force-bearing element 3-01 at the location where strain monitoring is required. The process of burying the force-bearing element is as follows: tie up the steel cage before pouring the concrete structure. After determining the absolute strain monitoring position, tie up the force-bearing element equipped with the electromagnetic elastic absolute stress sensor and install it at the corresponding position of the steel cage. Then pour concrete to complete the embedding of the sensor. Figure 8 As shown, the entire process is simple and installation is easy. The orientation of the load-bearing element 3-01 should align with the actual force applied to that location within the bridge's concrete structure. Sensor placement is tailored to the specific requirements of the project structure, and multiple sensors can be embedded within the same structure. For simply supported beam bridges, the sensors in this embodiment can be placed on the mid-span compression side.

[0043] In order to ensure that the concrete absolute strain monitoring system 3 can accurately monitor the strain, the load-bearing element 3-01 should be prevented from entering the plastic stage. Therefore, when designing the sensor, a suitable load-bearing element should be selected to make it elastic within the strain range that needs to be monitored.

[0044] After the concrete is poured, the preliminary work is completed, and the unstressed state at this time is the initial reference state.

[0045] When a concrete structure or component is in operation, it will be deformed at the corresponding position due to its own gravity and various external forces. Accordingly, the force-bearing element 3-01 will also deform in coordination with the concrete due to the special thread treatment on the surface and the restrictions of the steel plates or nuts on both sides, thereby generating stress. The magnitude of the stress will be collected by the electromagnetic elastic absolute stress sensor 3-04 in the form of magnetic characteristic electrical signals and transmitted and displayed on the magnetic elastic instrument 3-05.

[0046] The stress-strain relationship of the load-bearing element 3-01 has been calibrated in the laboratory before installation. Therefore, the absolute stress measured by the electromagnetic elastic absolute stress sensor 3-04 can be converted into the absolute strain of the load-bearing element 3-01 based on this relationship. .

[0047] The shape of the force-bearing element 3-01 in the concrete absolute strain monitoring system 3 of this embodiment is as follows: Figure 1 As shown: To ensure that the absolute strain of the load-bearing element is the absolute strain of the concrete, measures need to be taken to ensure sufficient contact between the concrete and the load-bearing element to prevent relative slippage. An engaging thread 3-02 is provided on the load-bearing element 3-01 to increase the engaging force and resistance between the concrete and the element surface.

[0048] In order to ensure the integrity of the load-bearing element and the concrete and avoid slippage, two support joints 3-04 are fixed at both ends of the load-bearing element 3-01 to limit the slippage between the concrete and the element.

[0049] Due to the above treatment, it can be considered that the bridge concrete 1 and the load-bearing element 3-01 are deformed in coordination, and the absolute strains of the two should be equal, that is, .

[0050] Since the monitoring is based on the unstressed state of the structure as the initial reference state, the concrete strain obtained is the absolute strain of the bridge concrete 1. .

[0051] Verification Example In order to monitor the absolute strain of concrete materials under tension, we must first select a suitable load-bearing element. Here, we select a steel strand with a treated surface as the load-bearing element. The force-magnetic characteristic electric signal relationship is calibrated at different temperatures on a laboratory calibration frame to obtain a force-magnetic characteristic electric signal relationship curve. Then, the constitutive relationship curve of the elastic stage is calibrated for the same load-bearing element. The constitutive relationship curve is as follows: Figure 5 As shown, the stress-strain relationship satisfies (Mpa); The relationship curve between strain and magnetic characteristic can be obtained from the above two calibration results, such as Figure 7 As shown. Connect and install the calibrated force-bearing element with the electromagnetic elastic absolute stress sensor. Figure 8 The load-bearing element is embedded in the appropriate position. During operation, gravity and external loads will cause deformation on the compressive side of the concrete, resulting in strain. Since the load-bearing element is not subjected to axial compression or tension when the sensor is embedded, the strain measured in the load-bearing element is the absolute strain of the concrete.

[0052] Table 1

[0053] According to the results in the above table and Figure 7 It can be seen that the error between the absolute strain of concrete measured by the present invention and that measured by the vibrating wire strain gauge is within 5%, thus having relatively good accuracy.

[0054] The above description of the embodiments is intended to facilitate understanding and application of the present invention by those skilled in the art. It is apparent that those skilled in the art can readily make various modifications to the above embodiments and apply the general principles described herein to other embodiments without requiring creative effort. Therefore, the present invention is not limited to the above embodiments. Any improvements or modifications made by those skilled in the art based on the disclosure of the present invention should fall within the scope of protection of the present invention.

Claims

1. An electromagnetic elastic absolute strain monitoring device, characterized in that: include: The force-bearing element is embedded in the structure of the measured area or welded to the surface of the structure of the measured area, and its force direction is consistent with that of the structure of the measured area; The electromagnetic elastic absolute stress sensor is installed on the stress-bearing element and is used to collect the magnetic characteristic electrical signal at the stress-bearing element; The magnetoelastic instrument calculates and determines the absolute stress of the load-bearing element based on the magnetic characteristic electrical signal, and then converts the absolute stress of the load-bearing element into the absolute strain of the structure in the measured area based on the constitutive relationship of the load-bearing element calibrated in the laboratory.

2. The electromagnetic elastic absolute strain monitoring device according to claim 1, characterized in that: The electromagnetic elastic absolute stress sensor includes a supporting frame and a magnetic field generating element and a magnetoelectric sensing element fixed on the supporting frame. The magnetic field generating element is controlled by the magnetoelastic instrument and is used to generate a magnetic field in the measured area, thereby magnetizing the force-bearing element; the magnetoelectric sensing element generates a magnetic characteristic electrical signal representing the magnetic induction intensity at the force-bearing element through electromagnetic induction.

3. The electromagnetic elastic absolute strain monitoring device according to claim 1, characterized in that: The force-bearing element is made of steel wire, steel strand or screw, and is in an elastic stage inside or on the surface of the structure in the tested area.

4. The electromagnetic elastic absolute strain monitoring device according to claim 3, characterized in that: The force-bearing element is processed with engaging threads.

5. The electromagnetic elastic absolute strain monitoring device according to claim 4, characterized in that: Support joints are fixed at both ends of the force-bearing element. If the force-bearing element is a steel wire or steel strand, the support joints are welded with steel plates and the steel wire or steel strand; if the force-bearing element is a screw, the support joints are threaded with a nut.

6. The electromagnetic elastic absolute strain monitoring device according to claim 1, characterized in that: The magnetoelastic instrument receives magnetic characteristic electrical signals collected from electromagnetic elastic absolute stress sensors, and calculates and determines the absolute stress of the stressed element based on the magnetic characteristic electrical signal curves of the stressed element under different stress magnitudes. Then, based on the constitutive relationship of the stressed element calibrated in the laboratory, the absolute stress is converted into the absolute strain of the stressed element. Due to the cooperative deformation relationship between the structure and the stressed element, the absolute strain of the stressed element is the absolute strain of the structure in the measured area.

7. The electromagnetic elastic absolute strain monitoring device according to claim 1, characterized in that: The monitoring system also includes an information interaction device, through which the magnetoelastic instrument transmits the absolute stress of the force-bearing element and the absolute strain of the structure in the measured area to a host computer for display so that the user can view it.

8. The method for using the electromagnetic elastic absolute strain monitoring device according to any one of claims 1 to 7, comprising the following steps: (1) Determine the absolute strain monitoring area based on the project monitoring requirements; (2) Using an electromagnetic elastic absolute stress sensor to collect the magnetic characteristic electrical signals at the stressed element under different stress magnitudes, the magnetic characteristic electrical signal curves of the stressed element under different stress magnitudes are obtained by fitting; (3) Casting a structure in the monitoring area and burying force-bearing elements and electromagnetic elastic absolute stress sensors at corresponding positions in the monitoring area during the process, or welding force-bearing elements on the surface of the structure and installing electromagnetic elastic absolute stress sensors on the force-bearing elements; (4) When the structure in the monitoring area is deformed by an external force, the magnetoelastic instrument receives the magnetic characteristic electric signal at the stress-bearing element collected by the electromagnetic elastic absolute stress sensor, and calculates and determines the absolute stress of the stress-bearing element based on the magnetic characteristic electric signal curve; (5) The magnetoelastic instrument converts the absolute stress into the absolute strain of the load-bearing element based on the constitutive relationship of the load-bearing element calibrated in the laboratory. Since there is a cooperative deformation relationship between the structure and the load-bearing element, the absolute strain of the load-bearing element is the absolute strain of the structure in the monitoring area.

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