FRP prestress tensioning device and method for reduced scale model test

Abstract

The invention discloses an FRP prestress tensioning device and method for a reduced scale model test. The FRP prestress tensioning device comprises a fixed reaction frame, an integrated clamp, a limiting stopper, a screw rod, a force sensor and a common bolt. The fixed counter-force frame is arranged at the end, to be tensioned, of a component, the integrated clamp penetrates through an upper steel plate and a lower steel plate of FRP in a fastened mode through common bolts, the limiting stopper limits the screw to drive the integrated clamp to rotate in the tensioning process, it is guaranteed that the position of the integrated clamp is straight, and the screw is sequentially connected with the integrated clamp, the force sensor and the fixed counter-force frame. The invention further discloses an FRP prestress tensioning method for the reduced scale model test, and the screw rod is adjusted to reach the prestress meeting the design requirement by monitoring the change of the real-time tensioning force of the force sensor. The method has the characteristics of high efficiency, simplicity, convenience, high precision, low cost, high repeated utilization rate and the like, and can be applied to indoor tests and construction sites of reduced scale model tests.

Description

Technical Field

[0001] The invention relates to the field of prestressed structural engineering, and in particular to an FRP prestressed tensioning device and method for scaled model testing. Background Art

[0002] Fiber reinforced composite materials (FRP for short) have excellent mechanical properties, such as high strength, light weight, and corrosion resistance. Therefore, as a new type of material, they are widely used in structural reinforcement, bridge construction and other fields. Prestressed tensioned FRP can effectively reduce the deadweight and inertial load of the structure, improve the overall performance and seismic performance of the structure, and provide a reliable guarantee for the safe operation of the structure. In addition, FRP materials have excellent prestress retention performance. Even under long-term stress, they can maintain a stable prestress level, are not prone to relaxation and creep, and ensure the long-term stability of the structure.

[0003] Commonly used devices for FRP prestressing include tensioning machines, prestressing anchors and prestressing systems. Tensioning machines are key equipment for applying prestress, usually driven by a hydraulic system, and can apply the tension required for FRP. Prestressing anchors are used to fix the prestressed FRP material, and their design requires that they can effectively transfer prestress to the structure. The prestressing system is used to control the process of prestressing, including monitoring and adjusting the tensioning force to ensure stable application of prestress.

[0004] In the field of structural engineering, scaled model tests are a common method for evaluating the performance of structures under different loading conditions. For scaled model tests of complex structures, it is usually necessary to simulate the prestressing in real structures to accurately evaluate their behavior in actual engineering. However, there are some limitations to traditional prestressing devices. First, traditional devices are usually designed for prestressing of large structures, and their size and operation methods may not be suitable for scaled model tests. This leads to problems such as inconvenient operation and excessive space occupation when using traditional devices in scaled tests, which limits the flexibility and operability of the experiment. Secondly, the application range of traditional prestressing devices may not be flexible enough to meet the needs of scaled model tests. Since the structural size and load in scaled tests are relatively small, the force requirements for prestressing may be different from those for prestressing of traditional large structures. Therefore, traditional devices may not be able to accurately control the amount of prestress applied, affecting the accuracy and reliability of the test. In addition, the high cost of traditional devices, including equipment purchase, maintenance and operation costs, may increase the economic cost of the test and limit its widespread use in scientific research and engineering applications.

[0005] However, there is currently a lack of dedicated FRP prestressed tensioning devices and methods for scaled model tests. Existing FRP prestressed tensioning devices are usually used for structural reinforcement in actual engineering projects, such as the invention patent with announcement number CN110485748B, which discloses an anchoring structure and anchoring method for a carbon fiber plate. Although multiple fixing clamps are connected in series to anchor the carbon fiber plate, which can share the tension on the carbon fiber plate, it fails to meet the scaled model test's demand for precise control of the prestressed tensioning force. Therefore, a FRP prestressed tensioning device and method dedicated to scaled model tests are developed to meet the special needs of the experiment and improve the accuracy, efficiency and reliability of the experiment.

[0006] Therefore, some people are currently applying for the following application to solve the above problems; Technical comparison with patent CN212693484U "A long-term load-holding test device for FRP tendon pulling specimens based on spring principle" Patent CN212693484U, with the help of spring principle, designed a long-term load-holding test device for FRP tendon pulling specimens, which is mainly used to study the bonding performance of the FRP tendon and the internal interface of concrete. We prestress the FRP plate or cloth at the bottom of the concrete to achieve a stable and safe prestressed tensioning state.

[0007] Patent CN212693484U uses an oil pump with an annular pressure sensor to determine the loading level. The S-shaped tension pressure sensor we use has threaded holes at both ends of the sensor that match the tension rod, which can monitor the loading status in real time with an accuracy level of C2 or C3.

[0008] Technical comparison with patent CN104264998B "Self-anchored prestressing machine for quantitative control of FRP" In patent CN104264998B, a jack is used to apply reaction force to prestress FRP. In addition to using a through-type jack, our design can also use a simpler manual torque method.

[0009] Patent CN104264998B uses a self-anchoring method with a locking function for prestressing. We use a ground anchoring method fixed on the ground or supporting structure for prestressing, which is more reliable.

[0010] Technical comparison with patent CN107700867A "A flexible FRP sheet prestressing device and method" Patent CN107700867A uses the dual effects of end winding and corrugated clamping to prevent the flexible FRP sheet from sliding in the clamp. We use roughening of the contact surface, which can be wedge-shaped or tooth-shaped in addition to corrugated clamping, and can adopt a more flexible clamping form according to the loading level and FRP form.

[0011] Patent CN107700867A solves a relatively ideal horizontal prestressed FRP tensioning method. In order to solve the rotation problem that may occur during the actual tensioning process, we use an easily removable limiter to ensure that the FRP can be tensioned horizontally. Summary of the invention

[0012] In order to solve the above technical problems, the present invention proposes an FRP prestressing tensioning device and method for scaled model testing, which is efficient and simple, has high precision, low cost and high reuse rate.

[0013] To achieve the above object, the technical solution adopted by the present invention is: A FRP prestressed tensioning device for scale model testing comprises a fixed reaction frame, an integrated fixture, a stopper, a screw, a force sensor and ordinary bolts; the fixed reaction frame is arranged at the end of the FRP to be tensioned, the integrated fixture fastens the FRP by ordinary bolts, one side of the stopper is fixed to the fixed reaction frame by ordinary bolts, and the other side contacts the upper surface of the integrated fixture, one end of the screw passes through the middle of the U-shaped steel plate of the integrated fixture and is fixed by bolts, the other end of the screw passes through the outer end bracket of the fixed reaction frame and is fixed by bolts, the force sensor is between the integrated fixture and the outer end bracket of the fixed reaction frame, and the force sensor is S-shaped and passed through by the screw.

[0014] As a further improvement of the structure of the present invention, the fixed reaction frame is composed of five steel plates, namely, two left and right side plates, two front and rear end plates and a bottom plate, wherein the left and right side plates each have two circular holes, the end plate away from the component has a circular hole, and the upper surface of the end plate close to the component is flush with the lower surface of the integrated clamp.

[0015] As a further improvement of the structure of the present invention, the integrated clamp is composed of a U-shaped steel plate, an upper steel plate, a lower steel plate and ordinary bolts, wherein the U-shaped steel plate is chamfered inside and has a circular hole in the center, the lower steel plate is integrally formed or welded with the U-shaped steel plate, the upper steel plate is detachable, and its width is 5 to 20 mm less than that of the lower steel plate, the upper and lower steel plates correspond to two rows of circular holes respectively, and the number of circular holes in each row is 2 to 4.

[0016] As a further improvement of the structure of the present invention, the contact surfaces of the upper and lower steel plates of the integrated clamp are roughened and are wedge-shaped, wave-shaped or tooth-shaped.

[0017] As a further improvement of the structure of the present invention, the limiter is an angle steel or a channel steel, and the side plate connected to the fixed reaction frame has two circular holes.

[0018] As a further improvement of the structure of the present invention, the screw threaded connection force sensor, and the matching nut are respectively connected through holes to fix the outer side of the reaction frame and the inner side of the U-shaped steel plate of the integrated clamp, medium assembly or rough assembly; ordinary bolts are connected through holes to fix the reaction frame, the integrated clamp and the limiter, medium assembly or rough assembly.

[0019] As a further improvement of the structure of the present invention, the force sensor is an S-shaped tension and pressure sensor with digital display or signal output function, a threaded hole at the top and bottom, a measuring range of 0~100 kN, and an accuracy level of C2 or C3.

[0020] As a further improvement of the structure of the present invention, the FRP is an FRP plate or an FRP cloth, and the length of the clamped section is the length of the upper and lower steel plates of the integrated clamp along the FRP direction.

[0021] The present invention provides an operating method of an FRP prestressing tensioning device for scale model testing, and the specific steps are as follows: (a) FRP fixing: FRP passes through the upper and lower steel plates of the integrated fixture and is fastened with ordinary bolts of the integrated fixture; (b) Centering: Tighten the ordinary bolts of the limiter to ensure that the reaction frame, integrated fixture, force sensor and screw are horizontally aligned; (c) Force sensor debugging: connect the force sensor and the data acquisition system, set and adjust the data acquisition parameters; (d) Prestressing: Use a wrench to turn the nut of the screw or a through-hole jack to drive the screw, and apply stress in stages, which are 25%, 50%, 75%, 100%, and 103% of the designed prestressing stress. Stabilize for 2 to 3 minutes, observe the force value changes of the data acquisition system, and determine whether the FRP slips. If slip occurs, slowly unload it, remove the ordinary bolts of the integrated fixture, and repeat the operation according to steps (a) to (d). (e) Fixing of FRP tensioning end: Install the FRP tensioning end anchorage. The installation process should be symmetrical and there should be no looseness or misalignment after installation. (f) FRP holding and screw unloading: The FRP is loaded to the design requirement, and the force value changes of the data acquisition system are observed during the process. When no abnormal situation occurs, the nut in contact with the fixed reaction frame is slowly unloaded. If the nut is difficult to remove, the nut in contact with the integrated fixture can be loosened; (g) Device dismantling and FRP treatment: Remove the limiter, screw, and force sensor in turn, loosen the ordinary bolts of the integrated fixture, and cut off the excess FRP.

[0022] The beneficial effects of the present invention are: The FRP prestressed tensioning device for scaled model testing described in the present invention comprises a fixed reaction frame, an integrated clamp, a stopper, a screw, and a force sensor; the fixed reaction frame is arranged at the end of the component to be tensioned, the integrated clamp fastens the FRP by ordinary bolts, one side of the stopper is fixed to the fixed reaction frame by ordinary bolts, and the other side contacts the upper surface of the integrated clamp, and the screw is divided into two sections, which are respectively connected to the integrated clamp, the force sensor and the fixed reaction frame. Through the above structural design, the prestressed tensioning device adopts a modular design, so that each component can be quickly disassembled and combined, which can simplify the assembly and adjustment process of the device, improve assembly efficiency, and flexibly select components according to needs to reduce costs. The screw adopts a segmented design, which can flexibly adjust the length according to different test requirements and improve the reuse rate.

[0023] Another beneficial effect of the present invention is: The FRP prestressing tensioning method for scale model test described in the present invention comprises the following process steps, specifically: (a) FRP fixing: FRP passes through the upper and lower steel plates of the integrated fixture, and the ordinary bolts of the integrated fixture are tightened; (b) centering: tighten the ordinary bolts of the limiter to ensure that the horizontal center of the fixed reaction frame, the integrated fixture, the force sensor and the screw are aligned; (c) force sensor debugging: connect the force sensor and the data acquisition system, set and adjust the data acquisition parameters; (d) prestressing tensioning: use a wrench to turn the nut of the screw or a through-hole jack to drive the screw, and apply stress by graded tensioning, which is 25%, 50%, 75%, 100%, and 103% of the designed tensioning stress, respectively, and stabilize for 2 to 3 minutes, observe the force value change of the data acquisition system, and judge whether the FRP slips. If slip occurs, slowly unload, remove the ordinary bolts of the integrated fixture, and repeat the operation according to steps (a) to (d); (e) FRP tensioning end fixation: Install the FRP tensioning end anchor, and operate symmetrically during the installation process. There will be no loosening or misalignment after installation. (f) FRP holding and screw unloading: FRP is loaded to the design requirements, and the force value changes of the data acquisition system are observed during the period. If there are no abnormalities, slowly unload the nut in contact with the fixed reaction frame. If the nut is not easy to remove, loosen the nut in contact with the integrated fixture. (g) Device removal and FRP processing: Remove the limiter, screw, and force sensor in turn, loosen the ordinary bolts of the integrated fixture, and cut off the excess FRP. Through the guidance of the above process steps, the accuracy and precision of each operation link are ensured, and the force conditions can be monitored in real time and the operation can be adjusted in time. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a structural schematic diagram of the prestressed tensioning device of the present invention; Figure 2 It is a structural schematic diagram of a fixed reaction frame of the present invention; Figure 3 It is a structural schematic diagram of the integrated clamp of the present invention; Figure 4 It is a schematic diagram of the structure of the limiter of the present invention; Figure 5 It is a structural schematic diagram of the screw of the present invention; Figure 6 It is a schematic structural diagram of the force sensor of the present invention.

[0025] exist Figures 1 to 6 Included are: 1. Fixed reaction frame, 2. Integrated clamp, 3. Limiter, 4. Screw, 5. Force sensor, 6. Ordinary bolt, 7. FRP. DETAILED DESCRIPTION

[0026] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments: like Figures 1 to 6 As shown, an FRP prestressed tensioning device for scaled model test includes a fixed reaction frame 1, an integrated clamp 2, a limiter 3, a screw rod 4, a force sensor 5, and a common bolt 6.

[0027] The fixed reaction frame 1 is set at the end of the component to be tensioned according to the design requirements, and is fixed to the ground or the supporting structure by using an appropriate connection method. The integrated clamp 2 fastens the FRP 7 by ordinary bolts 6. The tightening force of the ordinary bolts does not exceed the bearing capacity of the FRP material to avoid damage or failure of the material. One side of the limiter 3 is fixed to the fixed reaction frame 1 by ordinary bolts 6, and the other side contacts the upper surface of the integrated clamp 2. One end of the screw 4 passes through the middle of the U-shaped steel plate of the integrated clamp 2 and is fixed by bolts. The other end of the screw 4 passes through the outer end bracket of the fixed reaction frame 1 and is fixed by bolts. The force sensor 5 is between the integrated clamp 2 and the outer end bracket of the fixed reaction frame 1. The force sensor 5 is S-shaped and passed through by the screw 4.

[0028] Furthermore, the fixed reaction frame 1 is composed of five steel plates, namely, two left and right side plates, two front and rear end plates and a bottom plate.

[0029] It should be further pointed out that the left and right side plates of the fixed reaction frame 1 each have two circular holes, the end plate away from the component has one circular hole, and the upper surface of the end plate close to the component is flush with the lower surface of the integrated fixture 2.

[0030] It should be further pointed out that the integrated fixture 2 is composed of a U-shaped steel plate, an upper steel plate, a lower steel plate and ordinary bolts 6. The gap between the inside of the U-shaped steel plate and the upper and lower steel plates is 50-100 mm, which is convenient for tightening the ordinary bolts 6.

[0031] It should be further pointed out that the U-shaped steel plate of the integrated fixture 2 is chamfered internally and has a circular hole in the center. The lower steel plate and the U-shaped steel plate are integrally formed or welded. The upper steel plate is detachable and 5 to 20 mm wider than the lower steel plate. The upper and lower steel plates correspond to two rows of circular holes respectively, and the number of circular holes in each row is 2 to 4, which reduces the overall failure risk caused by single point failure.

[0032] It should be further pointed out that the contact surfaces of the upper and lower steel plates of the integrated fixture 2 are roughened and may be wedge-shaped, corrugated or tooth-shaped.

[0033] It should be further pointed out that the limiter 3 can be an angle steel or a channel steel, and the side plate connected to the fixed reaction frame has two circular holes.

[0034] It should be further pointed out that the screw rod 4 is connected to the force sensor 5 through a thread, and the matching nut is respectively connected through holes to the outer side of the fixed reaction frame 1 and the inner side of the U-shaped steel plate of the integrated clamp 2, which is medium assembly or rough assembly; the ordinary bolt 6 is connected through holes to the fixed reaction frame 1, the integrated clamp 2 and the limiter 3, which is medium assembly or rough assembly.

[0035] It should be further pointed out that when the screw rod 4 and the ordinary bolt 6 are connected through the through hole, a spring washer and a flat washer are installed in sequence between the nut and the connected part, and the spring washer should be replaced in time when reused.

[0036] It should be further pointed out that the screw rod 4 can be of grade 8.8, 10.9 or 12.9, with a nominal diameter of 10 to 18 mm, and is provided with two nuts; the ordinary bolt 6 can be of grade 4.8, 5.6 or 8.8, with a nominal diameter of 12 to 18 mm.

[0037] It should be further pointed out that when the tension force is 0~40 kN, the screw rod 4 adopts grade 8.8 or 10.9, with a nominal diameter of 10~14 mm, and the ordinary bolt 6 adopts grade 4.8 or 5.6, with a nominal diameter of 12~16 mm; when the tension force is 40~100 kN, the screw rod 4 adopts grade 10.9 or 12.9, with a nominal diameter of 14~18 mm, and the ordinary bolt 6 adopts grade 5.6 or 8.8, with a nominal diameter of 16~18 mm.

[0038] It should be further pointed out that the force sensor 5 is an S-shaped tension and pressure sensor with a digital display or output signal function, a threaded hole at the top and a threaded hole at the bottom, a measuring range of 0 to 100 kN, and an accuracy level of C2 or C3.

[0039] It should be further pointed out that FRP7 is an FRP plate or an FRP cloth, and the length of the clamped section is the length of the upper and lower steel plates of the integrated clamp 2 along the FRP direction.

[0040] Therefore, based on the above structural design, the FRP prestressed tensioning device of the present invention has the advantages of simple assembly, low cost and high reuse rate, and is suitable for various scale model tests and construction sites with a tensioning force of less than 10 t.

[0041] like Figures 1 to 6 As shown in the figure, a FRP prestressing method for scale model test includes the following process steps, specifically: (a) FRP fixing: FRP 7 passes through the upper and lower steel plates of the integrated fixture 2, and the ordinary bolts 6 of the integrated fixture 2 are tightened; (b) Centering: Tighten the ordinary bolts 6 of the limiter 3 to ensure that the reaction frame 1, the integrated fixture 2, the force sensor 5 and the screw 4 are horizontally aligned; (c) Force sensor debugging: Connect the force sensor 5 and the data acquisition system, set and adjust the data acquisition parameters; (d) Prestressing: Use a wrench to turn the nut of the screw 4 or a through-hole jack to drive the screw 4, and apply stress by graded tensioning, which is 25%, 50%, 75%, 100%, and 103% of the designed tensioning stress in turn, stabilize for 2 to 3 minutes, observe the force value change of the data acquisition system, and judge whether FRP 7 slips. If slip occurs, slowly unload it, remove the ordinary bolts 6 of the integrated fixture 2, and repeat the operation according to steps (a) to (d); (e) Fixing of FRP tensioning end: Install the FRP7 tensioning end anchor. The installation process is symmetrical. There is no looseness or misalignment after installation. (f) FRP holding and screw unloading: FRP7 is loaded to the design requirement. During this period, the force value change of the data acquisition system is observed. If there is no abnormality, the nut in contact with the fixed reaction frame 1 is slowly unloaded. If the nut is difficult to remove, the nut in contact with the integrated fixture 2 can be loosened. (g) Device dismantling and FRP processing: Remove the limiter 3, screw 4, and force sensor 5 in turn, loosen the ordinary bolt 6 of the integrated fixture 2, and cut off the excess FRP7.

[0042] Through the above process steps, the present invention can effectively complete the prestressing of FRP, and the operation is simple, accurate and controllable.

[0043] The above description is only a preferred embodiment of the present invention and does not constitute any other form of limitation to the present invention. Any modification or equivalent change made based on the technical essence of the present invention still falls within the scope of protection required by the present invention.

Claims

1. A FRP prestressing tensioning device for scale model test, characterized in that: The invention comprises a fixed reaction frame (1), an integrated clamp (2), a stopper (3), a screw (4), a force sensor (5) and a common bolt (6); the fixed reaction frame (1) is arranged at the end of the FRP (7) to be tensioned, the integrated clamp (2) fastens the FRP (7) by means of the common bolt (6), one side of the stopper (3) is fixed to the fixed reaction frame (1) by means of the common bolt (6), and the other side contacts the upper surface of the integrated clamp (2), one end of the screw (4) passes through the middle of the U-shaped steel plate of the integrated clamp (2) and is fixed by means of the bolt, the other end of the screw (4) passes through the outer end bracket of the fixed reaction frame (1) and is fixed by means of the bolt, the force sensor (5) is between the integrated clamp (2) and the outer end bracket of the fixed reaction frame (1), and the force sensor (5) is S-shaped and is passed through by the screw (4).

2. The FRP prestressing tensioning device for scale model test according to claim 1, characterized in that: The fixed reaction frame (1) is composed of five steel plates, namely, two left and right side plates, two front and rear end plates and a bottom plate, wherein the left and right side plates each have two circular holes, the end plate away from the component has a circular hole, and the upper surface of the end plate close to the component is flush with the lower surface of the integrated clamp (2).

3. The FRP prestressing tensioning device and method for scale model testing according to claim 1, characterized in that: The integrated clamp (2) is composed of a U-shaped steel plate, an upper steel plate, a lower steel plate and ordinary bolts (6), wherein the U-shaped steel plate is internally chamfered and has a circular hole in the center; the lower steel plate and the U-shaped steel plate are integrally formed or welded; the upper steel plate is detachable and has a width 5 to 20 mm less than the lower steel plate; the upper and lower steel plates correspond to two rows of circular holes respectively, and the number of circular holes in each row is 2 to 4.

4. The FRP prestressing tensioning device and method for scale model testing according to claim 3, characterized in that: The contact surfaces of the upper and lower steel plates of the integrated clamp (2) are roughened and are wedge-shaped, wave-shaped or tooth-shaped.

5. The FRP prestressing tensioning device and method for scale model testing according to claim 1, characterized in that: The stopper (3) is an angle steel or a channel steel, and a side plate connected to the fixed reaction frame has two circular holes.

6. The FRP prestressing tensioning device and method for scale model testing according to claim 1, characterized in that: The screw rod (4) is threadedly connected to the force sensor (5), and the matching nut is respectively connected through holes to the outer side of the fixed reaction frame (1) and the inner side of the U-shaped steel plate of the integrated clamp (2), and is medium-assembled or coarse-assembled; the ordinary bolt (6) is connected through holes to the fixed reaction frame (1), the integrated clamp (2) and the limiter (3), and is medium-assembled or coarse-assembled.

7. The FRP prestressing tensioning device and method for scale model testing according to claim 1, characterized in that: The force sensor (5) is an S-shaped tension and pressure sensor, having a digital display or output signal function, a threaded hole at the top and a threaded hole at the bottom, a measurement range of 0 to 100 kN, and an accuracy level of C2 or C3.

8. The FRP prestressing tensioning device and method for scale model testing according to claim 1, characterized in that: The FRP (7) is an FRP plate or an FRP cloth, and the length of the clamped section is the length of the upper and lower steel plates of the integrated clamp (2) along the FRP direction.

9. The method for operating the FRP prestressing tensioning device for scale model testing according to any one of claims 1 to 8, characterized in that: The specific steps are as follows: (a) FRP fixing: The FRP (7) passes through the upper and lower steel plates of the integrated fixture (2) and is fastened with ordinary bolts (6) of the integrated fixture (2); (b) Centering: Tighten the common bolt (6) of the stopper (3) to ensure that the fixed reaction frame (1), the integrated clamp (2), the force sensor (5) and the screw (4) are horizontally aligned; (c) Force sensor debugging: connect the force sensor (5) and the data acquisition system, set and adjust the data acquisition parameters; (d) Prestressing: Use a wrench to turn the nut of the screw rod (4) or a through-hole jack to drive the screw rod (4) to apply stress in stages, which are 25%, 50%, 75%, 100%, and 103% of the designed prestressing stress, respectively. Stabilize for 2 to 3 minutes, observe the force value change of the data acquisition system, and determine whether the FRP (7) has slipped. If slippage occurs, slowly unload it, remove the ordinary bolts (6) of the integrated fixture (2), and repeat the operation according to steps (a) to (d); (e) Fixing of FRP tensioning end: Install the FRP (7) tensioning end anchor. The installation process should be symmetrical and there should be no looseness or misalignment after installation. (f) FRP holding load and screw unloading: The FRP (7) is loaded to the design requirement, and the force value change of the data acquisition system is observed during the process. When no abnormality is found, the nut in contact with the fixed reaction frame (1) is slowly unloaded. If the nut is difficult to remove, the nut in contact with the integrated fixture (2) can be loosened; (g) Device removal and FRP treatment: Remove the stopper (3), screw (4), and force sensor (5) in sequence, loosen the ordinary bolts (6) of the integrated fixture (2), and cut off the excess FRP (7).

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