A prestressed tendon fatigue performance test device and method under high stress amplitude

Abstract

The application discloses a prestressed tendon fatigue performance test device under high stress amplitude, which comprises a fatigue testing machine, a testing machine chuck is arranged on the fatigue testing machine, and a fatigue testing assembly is connected to the testing machine chuck; the fatigue testing assembly comprises a stress reducing piece, a working anchor plate connected to the stress reducing piece, a working clamp plate arranged in the working anchor plate and a damping layer; the damping layer is arranged on the inner wall of the working anchor plate and extends to be connected to the stress reducing piece. The test device is simple in structure, simple and safe to operate, and can effectively avoid the situation that the prestressed tendon is prone to be broken at the clamping position during the test. The application further provides a prestressed tendon fatigue performance test method under high stress amplitude.

Description

Technical Field

[0001] This invention belongs to the field of prestressed tendon fatigue performance testing technology, specifically relating to a prestressed tendon fatigue performance testing device and method under high stress amplitude state. Background Technology

[0002] In cable-stayed bridge engineering, cables operate continuously under cyclic loading conditions. The fatigue performance of these cables is crucial to bridge safety. Prestressed tendons, as a vital component of the cables, are a significant factor influencing their fatigue performance. Typically, the stress amplitude for fatigue testing of prestressed tendons used in cables is 300 MPa. The national standard GB / T21839-2019, "Test Methods for Steel for Prestressed Concrete," stipulates that if a prestressed tendon fractures within the clamp or within 2d of the clamp in a fatigue performance test, the test is considered invalid. However, when using existing fatigue testing equipment and methods for prestressed tendon fatigue testing, various fracture scenarios easily occur at the clamping location, especially in high-stress amplitude fatigue tests. The vast majority of fractures occur at the clamping location, rendering the test results invalid and making it impossible to accurately determine the fatigue performance of the prestressed tendons.

[0003] Patent application number CN201510084675.3 discloses a double-layer clamp and its installation process for fatigue tensile testing of ordinary steel bars and prestressed tendons. The clamp includes a clamp head composed of a load-reducing clamp and a load-holding clamp, which is connected to the testing machine via a connecting device. The load-reducing clamp includes a load-reducing clamp clip, a load-reducing clamp base, and a load-reducing clamp bottom cover. The load-reducing clamp clip is located inside the load-reducing clamp base, which is connected to the connecting device. The load-reducing clamp bottom cover is located at the end where the load-reducing clamp base connects to the connecting device. The load-holding clamp is a common prestressed tendon tensioning tool anchor, including a load-holding clamp base and a load-holding clamp clip. The load-holding clamp clip is located in the innermost layer, inside the load-holding clamp base, which is inside the load-holding clamp base.

[0004] The following problems exist when using the above-mentioned fixture for fatigue tensile testing: First, as shown in the attached diagram, steps are provided at the clamping plates and base of the unloading fixture. Stress concentration may occur during loading or testing, and the two may not match well. During loading, the clamping plates of the unloading fixture cannot follow the prestressing tendon, and misalignment may occur under high stress amplitude, affecting the test and making it impossible to accurately determine the fatigue performance of the prestressing tendon. Second, when using the above-mentioned fixture for pre-tightening loading, in order to ensure that the unloading fixture fully anchors the prestressing tendon and that the force on the end face of the clamping plates is equal to the longitudinal tensile force received by the prestressing tendon, it is necessary to tighten the pre-tightening nuts one and two others with a wrench. However, before the loading process, the prestressing tendon has already been stretched at a uniform speed of 2kN / s until the tensile force exceeds 20% of the upper limit of the test design load. At this point, the tensile force is large, and manual tightening of the pre-tightening nuts is dangerous. Summary of the Invention

[0005] To address the aforementioned problems, this invention aims to provide a testing device and method for the fatigue performance of prestressed tendons under high stress amplitude conditions.

[0006] To achieve the above objectives, the present invention adopts the following technical solution:

[0007] A fatigue performance testing device for prestressed tendons under high stress amplitude conditions includes a fatigue testing machine, wherein a testing machine clamp is provided on the fatigue testing machine, and a fatigue testing component is connected to the testing machine clamp.

[0008] A fatigue testing assembly includes a stress-reducing component, a working anchor plate connected to the stress-reducing component, a working clip and a damping layer disposed within the working anchor plate; the damping layer is disposed on the inner wall of the working anchor plate and extends to be connected to the stress-reducing component.

[0009] Preferably, the stress-reducing component includes a support nut, a stress-reducing anchor plate connected to the support nut, and a stress-reducing clip disposed within the stress-reducing anchor plate.

[0010] Preferably, the working anchor plate is provided with a first conical hole for installing the working clamping piece, and a cylindrical hole communicating with the first conical hole for installing the damping layer; the damping layer is disposed in the cylindrical hole and extends to connect with the inner wall of the stress-reducing clamping piece.

[0011] Preferably, the stress-reducing anchor plate is provided with a second conical hole for installing stress-reducing clips.

[0012] Preferably, the fatigue test assembly is configured as two sets, respectively located at the first end and the second end of the prestressing tendon.

[0013] Preferably, the two sets of fatigue test components are respectively installed in the test machine clamps via support fixtures.

[0014] Preferably, the fatigue test assembly and the support fixture are connected by threads.

[0015] Preferably, it also includes a top-pressing fixture used in conjunction with the fatigue testing assembly; the top-pressing fixture includes a top-pressing support cylinder and a top-pressing head connected to the fatigue testing assembly, a top-pressing Haver gasket disposed between the top-pressing support cylinder and the top-pressing head, and a top-pressing press connected to the top-pressing head.

[0016] Preferably, the top-pressure Haver pad ring consists of two half-rings.

[0017] A method for testing the fatigue performance of prestressed tendons under high stress amplitude conditions includes the following steps:

[0018] S1. Insert the first end of the prestressing tendon into the working anchor plate and working wedge, and connect it to the jacking fixture. Apply jacking pressure F to the working wedge and working anchor plate using the jacking press. d This allows the working clamps to pre-engage the first end of the prestressing tendon;

[0019] S2. Remove the top-pressure fixture from the first end of the prestressing tendon, turn it around, and insert it into the second end of the prestressing tendon to connect the two sets of stress-reducing components; then insert the second end of the prestressing tendon into another set of working anchor plates and working wedges, and connect it to the second end of the prestressing tendon. At the same time, place the first end of the prestressing tendon in the top-pressure support cylinder, and then apply the top pressure Fd to the working wedges and working anchor plates corresponding to the second end of the prestressing tendon, so that the corresponding working wedges pre-engage the second end of the prestressing tendon;

[0020] S3. Remove the top pressing fixture at the second end of the prestressed tendon. Damping layers are respectively installed on the working anchor plates corresponding to the first and second ends of the prestressed tendon. Then, move the two sets of stress-reducing components to the first and second ends of the prestressed tendon until they contact and connect with the corresponding working anchor plates. The damping layers are clamped by stress-reducing clips and fixed by support nuts.

[0021] S4. Install the first and second ends of the prestressed tendons in S3 and their corresponding fatigue test components into the support fixtures respectively. Install the two support fixtures into the test machine chucks and tighten them. Move the position of the test machine chucks to adjust the distance between the two support fixtures.

[0022] S5. Apply a loading force to the fatigue test assembly using a fatigue testing machine, adjust the parameters, and then begin the fatigue test; the test is terminated when one or more steel wires in the prestressing tendon break or remain undamaged and the number of cycles specified in the standard is reached;

[0023] Among them, F d The top pressure is used to pre-engage the prestressing tendons in the working clamps.

[0024] In step S5, the applied force is gradually increased from 0 to the maximum force F of the prestressed tendon fatigue test. up and in F up The fatigue test component is held under the applied force for a specified time T to allow it to fully adhere and compact with the prestressed tendon. The applied force is then increased to the median fatigue test stress F0, with parameters including the stress amplitude F set. r , frequency f;

[0025] Among them, F up The maximum force during the fatigue test is given by F, where T is the holding time of the maximum force before the fatigue test, F0 is the median load during the fatigue test, and F... r denoted as σ, where f is the stress amplitude in the fatigue test, and f is the load cycle frequency in the fatigue test.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] This invention discloses a fatigue performance testing device for prestressed tendons under high stress amplitude conditions, comprising a fatigue testing machine with a testing machine clamp connected to it, and a fatigue testing assembly. The fatigue testing assembly includes a stress-reducing component, a working anchor plate connected to the stress-reducing component, a working clamp within the working anchor plate, and a damping layer. The damping layer is located on the inner wall of the working anchor plate and extends to connect with the stress-reducing component. This testing device has a simple structure, is easy and safe to operate, and effectively avoids the risk of prestressed tendons breaking at the clamping position during testing.

[0028] In this invention, stress-reducing components and a damping layer are provided. The damping layer fully compresses and wraps the prestressing tendon, which reduces the stress amplitude transmitted to the working clamp and working anchor plate during the prestressing tendon fatigue test. This ensures that the fracture location of the prestressing tendon during the fatigue performance test is at the free segment of the prestressing tendon, thereby obtaining effective test data and ensuring that the magnitude of the fatigue test stress amplitude has no effect on the efficiency of the test results.

[0029] In this invention, by setting up a top-pressing tool to press the working clamp and the working anchor plate, the tooth surface of the working clamp fully engages with the prestressing tendon, so that the microscopic movement of the prestressing tendon held by the tooth surface of the working clamp is minimized during the fatigue test, and there is no adverse effect on the fatigue performance of the free section of the prestressing tendon.

[0030] In this invention, an electro-hydraulic servo fatigue testing machine is used to conduct fatigue tests on prestressed tendons. The load force value accuracy is high, and the loading error range and stress error range far meet the requirements of the test method standard, providing reliable data for evaluating the fatigue performance of prestressed tendons. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the specific embodiments of the present invention, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of a prestressed tendon fatigue performance testing device under high stress amplitude state according to the present invention.

[0033] Figure 2 This is a schematic diagram illustrating the use of the top-pressing tool in this invention;

[0034] Figure 3 This is a schematic diagram of the assembly of the top-pressure fixture and the fatigue testing assembly in this invention;

[0035] Figure 4 This is a schematic diagram of the fatigue testing assembly in this invention;

[0036] Reference numerals: 1-Fatigue testing machine, 100-Fatigue testing assembly, 101-Testing machine clamp, 2-Stress-reducing component, 21-Support nut, 22-Stress-reducing anchor plate, 23-Stress-reducing clamp, 3-Working anchor plate, 4-Working clamp, 5-Damping layer, 6-Support clamp, 7-Top pressure support cylinder, 8-Top pressure head, 9-Top pressure Haver washer ring, 10-Top pressure press, 11-Prestressing tendon. Detailed Implementation

[0037] The present invention will be further described below with reference to the accompanying drawings and specific embodiments. However, it should not be construed that the scope of the subject matter of the present invention is limited to the following embodiments. All modifications, substitutions and alterations made based on ordinary technical knowledge and common practices in the art without departing from the above-described technical concept of the present invention are included within the scope of the present invention.

[0038] Combined with reference Figures 1 to 4 The present invention discloses a fatigue performance testing device for prestressed tendons under high stress amplitude, comprising a fatigue testing machine 1, wherein a testing machine chuck 101 is provided on the fatigue testing machine 1, and a fatigue testing component 100 is connected to the testing machine chuck 101; the fatigue testing machine 1 in the present invention adopts an existing type, such as the PWS-300 fatigue testing machine or the WAW-300B universal testing machine, and the testing machine chuck 101 is a part of the fatigue testing machine 1.

[0039] The fatigue test assembly 100 is configured in two sets, located at the first and second ends of the prestressing tendon 11, respectively. Each fatigue test assembly 100 includes a stress-reducing component 2, a working anchor plate 3 connected to the stress-reducing component 2, a working clamping piece 4 disposed within the working anchor plate 3, and a damping layer 5. The damping layer 5 is disposed on the inner wall of the working anchor plate 3 and extends to connect with the stress-reducing component 2. The damping layer 5 can be made of metallic or non-metallic materials. Metallic materials include soft metal sheets such as aluminum sheets, copper sheets, copper foil, aluminum foil, and nickel sheets, while non-metallic materials include rubber sheets, nylon sheets, and PE sheets.

[0040] The stress-reducing component 2 includes a support nut 21, a stress-reducing anchor plate 22 connected to the support nut 21, and a stress-reducing clamping piece 23 disposed within the stress-reducing anchor plate 22. Specifically, a second conical hole is provided in the stress-reducing anchor plate 22, and a stress-reducing clamping piece 23 adapted thereto is installed in the second frustum.

[0041] The working anchor plate 3 has a first conical hole for installing the working clamping piece 4, and a cylindrical hole communicating with the first conical hole for installing the damping layer 5; the damping layer 5 is disposed in the cylindrical hole and extends to connect with the inner wall of the stress-reducing clamping piece 23. Specifically, the damping layer 5 is disposed in the cylindrical hole of the working anchor plate 3 and extends to connect with the inner wall of the stress-reducing clamping piece 23, and the total length of the damping layer 5 is the sum of the total length of the cylindrical hole and the total length of the stress-reducing clamping piece 23. The supporting nut 21, the stress-reducing anchor plate 22, the stress-reducing clamping piece 23, the working anchor plate 3, and the working clamping piece 4 are coaxially arranged, and the prestressing tendon 11 passes through its middle.

[0042] Two sets of fatigue testing components 100 are respectively installed in the testing machine chuck 101 via support clamps 6. Specifically, the testing machine chuck 101 has a groove for installing the support clamp 6. The shape of the groove matches the outer shape of the support clamp 6, and the two opposite sides of the groove are connected. The support clamp 6 is installed in the testing machine chuck 101 along one side of the groove. The fatigue testing components 100 and the support clamp 6 are connected by threads. Specifically, the outer wall of the support nut 21 is provided with external threads, and the inner wall of the support clamp 6 is provided with corresponding internal threads. The two are connected by internal and external threads.

[0043] The testing apparatus also includes a top-pressure fixture used in conjunction with the fatigue testing assembly 100; the top-pressure fixture includes a top-pressure support cylinder 7 and a top-pressure head 8 connected to the fatigue testing assembly 100, a top-pressure Haver ring 9 disposed between the top-pressure support cylinder 7 and the top-pressure head 8, and a top-pressure press 10 connected to the top-pressure head 8. In this embodiment, the top-pressure Haver ring 9 consists of two half-rings. This arrangement facilitates the removal of the fatigue testing assembly 100 from the top-pressure support cylinder 7 when the top-pressure fixture is used in conjunction with the fatigue testing assembly 100 for testing.

[0044] A method for testing the fatigue performance of prestressed tendons under high stress amplitude conditions includes the following steps:

[0045] S1. Insert the first end of the prestressing tendon 11 into the working anchor plate 3 and the working wedge 4, and connect it to the jacking fixture. Apply a jacking pressure F to the working wedge 4 and the working anchor plate 3 through the jacking press. d The working clamp 4 pre-engages with the first end of the prestressing tendon 11;

[0046] S2. Remove the jacking fixture from the first end of the prestressing tendon 11, reverse its direction, and insert it into the connection of the two sets of stress-reducing components 2 from the second end of the prestressing tendon 11; then insert the second end of the prestressing tendon 11 into another set of working anchor plates 3 and working clamps 4, connecting them to the second end of the prestressing tendon 11, while the first end of the prestressing tendon 11 is placed inside the jacking support cylinder 7, and then apply the jacking force F to the working clamps 4 and working anchor plates 3 corresponding to the second end of the prestressing tendon 11. d This allows the corresponding working clamp 4 to pre-engage the second end of the prestressing tendon 11;

[0047] S3. Remove the top pressing fixture at the second end of the prestressed tendon 11. Damping layers 5 are respectively set on the working anchor plates 3 corresponding to the first and second ends of the prestressed tendon 11. Then, move the two sets of stress-reducing parts 2 to the first and second ends of the prestressed tendon 11 until they contact and connect with the corresponding working anchor plates 3. The damping layers 5 are clamped by the stress-reducing clips 23 and fixed by the support nuts 21.

[0048] S4. Install the first and second ends of the prestressed tendon 11 in S3 and its corresponding fatigue test assembly 100 into the support fixture 6 respectively. The two support fixtures 6 are installed in the test machine chuck 101 and tightened. Move the position of the test machine chuck 101 to adjust the distance between the two support fixtures 6.

[0049] S5. Apply a loading force to the fatigue test assembly 100 using the fatigue testing machine 1, adjust the parameters, and then begin the fatigue test; the test is terminated when one or more steel wires in the prestressed tendon 11 break or are not damaged and the number of cycles specified in the standard is reached;

[0050] Among them, F d The top pressure of the prestressing tendon 11 is used to pre-engage the working clamp 4.

[0051] In step S5, the loading force is gradually increased from 0 to the maximum force F of the prestressed tendon 11 during fatigue testing. up and in F up The fatigue test component 100 and the prestressed tendon 11 are held under the applied force for a specified time T, allowing them to fully adhere and compact with each other. The applied force is then applied to the fatigue test stress median F0, with parameters including the stress amplitude F. r, frequency f;

[0052] Among them, F up The maximum force during the fatigue test is given by F, where T is the holding time of the maximum force before the fatigue test, F0 is the median load during the fatigue test, and F... r denoted as σ, where f is the stress amplitude in the fatigue test, and f is the load cycle frequency in the fatigue test.

[0053] Example 1

[0054] Using the above-mentioned test apparatus and method, the prestressed tendon 11 was subjected to a maximum force of 0.45F. ptk Fatigue performance test with a stress amplitude of 450MPa and a cycle count of 2 million.

[0055] The specific experiment is as follows: (Refer to...) Figure 2 S1. After inserting the first end of the prestressing tendon 11 into the working anchor plate 3 and the working clamp 4, the top pressure head 8 is installed at the end of the working anchor plate 3 with the first conical hole and connected to the first end of the prestressing tendon 11. A top pressure press is installed on the top pressure head 8; a top pressure Haver ring 9 is connected to the end of the working anchor plate 3 with the cylindrical hole, and the top pressure Haver ring 9 is installed on the top pressure support cylinder 7. That is, the first end of the prestressing tendon 11 is connected to the top pressure head 8, and the second end of the prestressing tendon 11 passes through the working clamp 4, the cylindrical hole of the working anchor plate 3 and the top pressure Haver ring 9 in sequence and is placed on the top pressure support cylinder 7. Then, a top pressure of 208kN (i.e., 0.8F) is applied to the working clamp 4 and the working anchor plate 3 by the top pressure press. ptk F ptk (For the nominal ultimate tensile strength of the prestressing tendon 11), the working wedge 4 pre-engages the first end of the prestressing tendon 11. The engagement of the working wedge 4 with the prestressing tendon 11 can be achieved by the anchor tensioning method of the prestressing tendon 11.

[0056] Reference Figure 3 S2. Remove the top-pressing fixture from the first end of the prestressing tendon 11, reverse its direction, and insert it into the second end of the prestressing tendon 11, connecting two sets of stress-reducing components 2. Each set of stress-reducing components 2 includes a support nut 21, a stress-reducing anchor plate 22 connected to the support nut 21, and a stress-reducing clamp 23 disposed within the stress-reducing anchor plate 22. Then, insert the second end of the prestressing tendon 11 into another set of working anchor plates 3 and working clamps 4, connecting it to the second end of the prestressing tendon 11. At the same time, place the first end of the prestressing tendon 11, the corresponding working anchor plate 3, working clamp 4, and the installed stress-reducing components 2 into the top-pressing support cylinder 7. The connection method between the top-pressing fixture and the second end of the prestressing tendon 11 is the same as the connection method between the top-pressing fixture and the first end of the prestressing tendon 11 in step S1. Then, apply a top pressure of 208kN (i.e., 0.8F) to the working clamp 4 and working anchor plate 3 corresponding to the second end of the prestressing tendon 11. ptk F ptk(for the nominal ultimate tensile strength of prestressing tendon 11), so that the corresponding working clamp 4 pre-engages the second end of prestressing tendon 11;

[0057] Reference Figure 4 S3. Remove the top pressing fixture from the second end of the prestressed tendon 11. Damping layers 5 are respectively installed on the working anchor plates 3 corresponding to the first and second ends of the prestressed tendon 11. Then, move the two sets of stress-reducing parts 2 to the first and second ends of the prestressed tendon 11 until they contact and connect with the corresponding working anchor plates 3. The damping layers 5 are clamped by the stress-reducing clips 23 and fixed by the support nuts 21.

[0058] Reference Figure 1 S4. Install the first and second ends of the prestressing tendon 11 and its corresponding fatigue test assembly 100 in the support fixtures 6 respectively. That is, the first end of the prestressing tendon 11 and the fatigue test assembly 100 connected to it are installed in one support fixture 6, and the second end of the prestressing tendon 11 and the fatigue test assembly 100 connected to it are installed in another support fixture 6. The two support fixtures 6 are installed in the testing machine chuck 101 and tightened. Move the position of the testing machine chuck 101 to adjust the distance between the two support fixtures 6.

[0059] S5. Apply a loading force to the fatigue test assembly 100 using the fatigue testing machine 1. The loading force value is gradually increased from 0 to the upper limit load of the prestressed tendon 11 fatigue test, which is 117kN (i.e., 0.45F). ptk F ptk For the prestressed tendon (nominal ultimate tensile strength 11), and at 0.45F ptk The force value is maintained at the specified time for 30 minutes to allow the fatigue test assembly 100 and the prestressing tendon 11 to fully adhere and compact. The parameters are adjusted to apply the force value to the median fatigue test stress of 90 kN, with a stress amplitude of 450 MPa, a frequency of 10 Hz, and a cycle count of 2 million. The fatigue test can then begin. The test terminates when one or more wires in the prestressing tendon 11 break or remain undamaged, and the specified number of cycles is reached.

[0060] In this invention, by setting the top-pressing tool to press the working clamp 4 and the working anchor plate 3, the tooth surface of the working clamp 4 fully engages with the prestressing tendon 11, so that the microscopic movement of the prestressing tendon 11 held by the tooth surface of the working clamp 4 is minimized during the fatigue test, and there is no adverse effect on the fatigue performance of the free section of the prestressing tendon 11.

[0061] In this invention, the stress-reducing component 2 and the damping layer 5 are provided. The damping layer 5 fully compresses and wraps the prestressing tendon 11, which reduces the stress amplitude transmitted to the working clamp 4 and the working anchor plate 3 during the fatigue test of the prestressing tendon 11. This ensures that the fracture location of the prestressing tendon 11 during the fatigue performance test is at the free section of the prestressing tendon 11, thereby obtaining effective test data and ensuring that the magnitude of the fatigue test stress amplitude has no effect on the effectiveness of the test results.

[0062] In this invention, an electro-hydraulic servo fatigue testing machine is used to conduct fatigue tests on the prestressed tendon 11. The load force value accuracy is high, and the loading error range and stress error range far meet the test method standard requirements, providing reliable data for evaluating the fatigue performance of the prestressed tendon 11.

[0063] In this invention, the test device has a simple structure, is easy to operate and safe, and effectively avoids the situation where the prestressing tendon 11 is prone to breakage at the clamping position during the test.

[0064] The foregoing has provided a detailed description of the testing device and method for the fatigue performance of prestressed tendons under high stress amplitude conditions provided by this invention. Specific examples have been used to illustrate the structure and working principle of this invention. The descriptions of the embodiments above are merely for the purpose of helping to understand the method and core ideas of this invention. It should be noted that those skilled in the art can make various improvements and modifications to this invention without departing from its principles, and these improvements and modifications also fall within the scope of protection of the claims of this invention.

Claims

1. A method for testing the fatigue performance of prestressed tendons under high stress amplitude conditions, characterized in that: The fatigue performance test device for prestressed tendons is used. The device includes a fatigue testing machine (1), a testing machine chuck (101) is provided on the fatigue testing machine (1), and a fatigue testing component (100) is connected to the testing machine chuck (101). The fatigue test assembly (100) includes a stress-reducing component (2), a working anchor plate (3) connected to the stress-reducing component (2), a working clip (4) disposed within the working anchor plate (3), and a damping layer (5); the damping layer (5) is disposed on the inner wall of the working anchor plate (3) and extends to be connected to the stress-reducing component (2); The stress-reducing component (2) includes a support nut (21), a stress-reducing anchor plate (22) connected to the support nut (21), and a stress-reducing clip (23) disposed in the stress-reducing anchor plate (22). It also includes a top-pressing fixture used in conjunction with the fatigue testing assembly (100); the top-pressing fixture includes a top-pressing support cylinder (7) and a top-pressing head (8) connected to the fatigue testing assembly (100), a top-pressing Haver gasket (9) disposed between the top-pressing support cylinder (7) and the top-pressing head (8), and a top-pressing press (10) connected to the top-pressing head (8). The method for testing the fatigue performance of prestressed tendons under high stress amplitude conditions includes the following steps: S1. Insert the first end of the prestressing tendon (11) into the working anchor plate (3) and the working wedge (4), and connect it to the top pressing fixture. Apply the top pressure F to the working wedge (4) and the working anchor plate (3) through the top pressing press (10). d , so that the working clamp (4) pre-engages with the first end of the prestressing tendon (11); S2. Remove the top-pressure fixture from the first end of the prestressing tendon (11), reverse its direction, and insert it into the connection of the two sets of stress-reducing components (2) from the second end of the prestressing tendon (11); then insert the second end of the prestressing tendon (11) into another set of working anchor plates (3) and working wedges (4), connecting it to the second end of the prestressing tendon (11), while the first end of the prestressing tendon (11) is placed inside the top-pressure support cylinder (7), and then apply the top pressure F to the working wedges (4) and working anchor plates (3) corresponding to the second end of the prestressing tendon (11). d , so that the corresponding working clamp (4) pre-engages with the second end of the prestressing tendon (11); S3. Remove the top pressing fixture from the second end of the prestressed tendon (11), and set damping layers (5) on the working anchor plates (3) corresponding to the first and second ends of the prestressed tendon (11). Then move the two sets of stress-reducing parts (2) to the first and second ends of the prestressed tendon (11) respectively until they contact and connect with the corresponding working anchor plates (3), and clamp the damping layer (5) with stress-reducing clips (23) and fix it with support nuts (21). S4. Install the first and second ends of the prestressed tendon (11) in S3 and its corresponding fatigue test assembly (100) into the support clamp (6), and install the two support clamps (6) into the test machine chuck (101) and tighten them; move the position of the test machine chuck (101) to adjust the distance between the two support clamps (6); S5. Apply a loading force to the fatigue test assembly (100) using the fatigue testing machine (1), adjust the parameters, and then start the fatigue test; the test is terminated when one or more wires in the prestressed tendon (11) break or are not damaged and the number of cycles specified in the standard is reached; Among them, F d The top pressure of the prestressing tendon (11) is used to pre-engage the working clamp (4).

2. The method for testing the fatigue performance of prestressed tendons under high stress amplitude state according to claim 1, characterized in that: The working anchor plate (3) is provided with a first conical hole for installing the working clamp (4) and a cylindrical hole that communicates with the first conical hole and is used for installing the damping layer (5); the damping layer (5) is provided in the cylindrical hole and extends to connect with the inner wall of the stress-reducing clamp (23).

3. The method for testing the fatigue performance of prestressed tendons under high stress amplitude state according to claim 1, characterized in that: The stress-reducing anchor plate (22) is provided with a second conical hole for installing the stress-reducing clip (23).

4. The method for testing the fatigue performance of prestressed tendons under high stress amplitude state according to claim 1, characterized in that: The fatigue test assembly (100) is set in two groups, respectively located at the first and second ends of the prestressed tendon (11).

5. The method for testing the fatigue performance of prestressed tendons under high stress amplitude state according to claim 4, characterized in that: The two fatigue test components (100) are installed in the test machine chuck (101) by the support clamp (6).

6. The method for testing the fatigue performance of prestressed tendons under high stress amplitude state according to claim 5, characterized in that: The fatigue test assembly (100) is connected to the support fixture (6) by a thread.

7. The method for testing the fatigue performance of prestressed tendons under high stress amplitude state according to claim 1, characterized in that: In step S5, the loading force value is gradually increased from 0 to the maximum force value F of the prestressed tendon (11) during fatigue testing. up and in F up The force value is maintained for a specified time T to allow the fatigue test component (100) and the prestressed tendon (11) to fully adhere and clamp together; the loading force value is applied to the fatigue test stress median F0, and the parameters set include the stress amplitude F. r , frequency f; Among them, F up The maximum force during the fatigue test is given by F, where T is the holding time of the maximum force before the fatigue test, F0 is the median load during the fatigue test, and F... r denoted as σ, where f is the stress amplitude in the fatigue test, and f is the load cycle frequency in the fatigue test.

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