Device and method for testing prestress loss of PCCP (prestressed concrete cylinder pipe)

Abstract

The invention discloses a PCCP prestress loss testing device and method, and relates to the technical field of PCCP prestress loss testing, and the method comprises the following steps: S1, determining an equivalent bending curvature radius according to a target pipe diameter, and selecting a test section bending baffle plate matched with the equivalent bending curvature radius, on the basis of the equivalent bending curvature radius, concrete with the strength equal to that of the target pipe core concrete is poured at the position of the bending baffle of the test section, curing is conducted till the preset strength is achieved through the test, and the concrete contact formwork with the curvature is obtained. The main machine can separate the specific influence rule of each single factor on the prestress loss rate, real decoupling analysis is achieved, prototype pipe tests are replaced with modular combination, the working state of the PCCP prestressed steel wire is truly simulated, meanwhile, the test period is effectively shortened, and the test cost is reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of PCCP prestress loss testing, and specifically to a PCCP prestress loss testing device and method. Background Art

[0002] The existing PCCP prestress loss testing method is to paste sensors on the prestressed high-strength steel wires of a complete finished pipe to carry out a static loss test. It has large material consumption (requiring a whole finished pipe), a long test cycle (the pipeline needs to be cured to the service state), few test times, and many test interference factors. The present invention truly simulates the actual working state of PCCP through an equal-proportion model, and carries out prestress loss tests through a data integration device. It can be reused in parallel, greatly reducing the test cost and shortening the test cycle. During the actual test process, multiple parameters such as the diameter of the prestressed tendon (5-9 mm), the initial tensile stress (800-1500 MPa), the concrete strength (C30-C60), the mortar protective layer strength (20-50 MPa), and the pipe diameter (DN2200-DN4000) act together. The traditional method cannot independently control a single test variable, while the present invention can carry out repeated tests to independently control each parameter to obtain more accurate results. Summary of the Invention

[0003] Aiming at the deficiencies of the existing technology, the present invention provides a PCCP prestress loss testing device and method.

[0004] To achieve the above object, the technical solution of the present invention is as follows:

[0005] A PCCP prestress loss testing device and method includes the following steps:

[0006] S1: Determine the equivalent bending curvature radius according to the target pipe diameter, select a test section bending baffle that matches the equivalent bending curvature radius, and pour concrete with the same strength as the target pipe core concrete at the test section bending baffle. Cure it until the test reaches the preset strength to obtain a concrete contact template with curvature.

[0007] S2: Pass the anchoring section of the test tendon through the anchoring section baffle and tighten the nut. Place a stress sensor between the nut and the anchoring section baffle to monitor the stress change of the test tendon in real time.

[0008] S3: Bend the measuring section of the test tendon along the bending curvature of the concrete contact template and attach it to the contact interface of the concrete contact template.

[0009] S4: Pass the tensioning section of the test tendon through the tensioning section baffle, apply a preset initial tensile stress, tighten the nut after reaching the preset value, remove the temporary loading device and let it stand for a preset time to eliminate the residual stress.

[0010] S5: Paste grating strain sensors at the maximum moment point and the inflection point of the measurement section of the test tendon. After maintaining the load for a specified time stably, synchronously collect the data of the stress sensors in the anchorage section and the data of the grating strain sensors in the measurement section, and calculate the prestress loss rate through the host computer;

[0011] Among them, through the independent control of the bending curvature radius in S1 and the concrete strength, and the stress stabilization process in S4, calculate and analyze the collected data to realize the decoupled analysis of the following parameters:

[0012] The influence of the tendon diameter on the prestress loss rate;

[0013] The influence of the tendon bending curvature on the prestress loss rate;

[0014] The influence of the concrete strength on the prestress loss rate.

[0015] Preferably, in S5, starting from one end of the measurement section of the test tendon close to the tensioning section, the maximum moment point is at the midpoint of the measurement section of the test tendon, and the inflection point is at the quarter position of the measurement section of the test tendon.

[0016] Preferably, grating strain sensors are pasted on the top and the outer side of the maximum moment point and the inflection point.

[0017] Preferably, the prestress loss rate in S5 The calculation formula is:

[0018] ;

[0019] Among them, is the slip amount at the tendon-concrete interface, =80 - 120GPa / mm is the slip influence coefficient, is the preset initial tensioning stress, is the tendon elastic modulus, is the tendon cross-sectional area, is the coordinate of the maximum moment point.

[0020] Preferably, the curvature radius of the bending baffle in the test section in S1 satisfies: ;

[0021] Among them, is the target pipe diameter, and the range of the target pipe diameter is 2200mm ≤ ≤ 4000mm, is the pipe wall thickness compensation coefficient, and the range of the pipe wall thickness compensation coefficient is 50mm ≤ ≤ 100mm.

[0022] Preferably, in S1, the diameter range of the test tendon is 5 - 9 mm, and the concrete strength range is C30 - C60.

[0023] Preferably, the standing time in S4 satisfies: ;

[0024] wherein, is the stress relaxation factor, and its value range is .

[0025] A PCCP prestress loss test device includes:

[0026] A base plate, an anchorage section baffle, and a tensioning section baffle, and all three are independently arranged;

[0027] Multiple test section bending baffles, and multiple said test section bending baffles are welded on the base plate with different preset curvatures, and the overall prototype pipe to be tested is simulated proportionally through a detachable combined structure to truly simulate the actual working state of PCCP;

[0028] Transverse reinforcing ribs, which are evenly distributed on the top of the test section bending baffles along the bending path of the test section bending baffles to ensure the integrity of the device and prevent the test tendons from being pulled off.

[0029] Preferably, triangular braces are arranged on the nut side surface of the anchorage section baffle and the bending inner surface of the test section bending baffle.

[0030] Preferably, a detachable hollow jack is arranged on one side of the tensioning section baffle, and the hollow jack is used to apply a preset initial tensile stress to the test tendons.

[0031] Compared with the prior art, the beneficial effects of the present invention are:

[0032] By systematically changing the tendon diameter, bending curvature, and concrete strength, the present invention can obtain multiple groups of experimental data. Through the established variable independent control ability and the provided accurate and stable loss rate data, the host computer can separate the specific influence law of each single factor on the prestress loss rate, realize true decoupling analysis, and through modular combination to replace the prototype pipe test, while truly simulating the working state of PCCP prestressed steel wires, effectively shortening the test cycle, reducing the test cost, and can be recycled. At the same time, through replaceable modules, independent adjustment of the tendon diameter, tendon bending diameter, concrete strength, and mortar strength can be realized, and precise and effective control of various influencing parameters in the PCCP prestress loss test can be achieved. The detachable combined structure is used to simulate the overall prototype pipe, and the independent adjustment modules of the tendon diameter, tendon bending diameter, concrete strength, and mortar strength are integrated to realize the prestress loss test of multi-parameter physical decoupling, improving the test accuracy and reliability. Description of the Drawings

[0033] The disclosure of the present invention will be described with reference to the accompanying drawings. It should be understood that the drawings are for illustrative purposes only and are not intended to limit the scope of protection of the present invention. In the drawings, the same reference numerals are used to refer to the same components. Among them:

[0034] Figure 1 is a schematic diagram of the overall structure of the test device of the present invention;

[0035] Figure 2 is the present invention Figure 1 is an enlarged view of the structure at location A of the present invention;

[0036] Figure 3 is a right view of the test device of the present invention;

[0037] Figure 4 is a front view of the second embodiment of the present invention;

[0038] Figure 5 is a rear view of the second embodiment of the present invention.

[0039] Explanation of the markings in the figure: 1. Substrate; 2. Tensioning section baffle; 3. Movable steel plate; 4. Hollow jack; 5. Staddle; 6. Triangular diagonal brace; 7. Anchorage section steel pipe; 8. Main machine; 9. Fiber Bragg grating demodulator; 10. Test reinforcing bar; 11. Concrete contact formwork; 12. Test section bending baffle; 13. Transverse reinforcing rib; 14. Anchorage section baffle; 15. Tensioning section steel pipe; 16. Fiber optic lead; 17. Grating strain sensor. Specific embodiments

[0040] It is easily understood that according to the technical solution of the present invention, without changing the essence of the present invention, those of ordinary skill in the art can propose various interchangeable structural forms and implementation methods. Therefore, the following specific embodiments and the accompanying drawings are only exemplary descriptions of the technical solution of the present invention, and should not be regarded as the whole of the present invention or as a limitation or restriction on the technical solution of the present invention.

[0041] As Figures 1-5 shown, a PCCP prestress loss test device and method includes the following steps:

[0042] S1: Determine the equivalent bending curvature radius according to the target pipe diameter, select the test section bending baffle 12 that matches the equivalent bending curvature radius, and pour concrete with the same strength as the target pipe core concrete at the test section bending baffle 12 based on the equivalent bending curvature radius, and cure until the test reaches the preset strength to obtain the concrete contact formwork 11 with curvature;

[0043] Specifically, the bending geometry of the test section bending baffle 12 and the test section bending baffle 12 is accurately controlled according to the target pipe diameter, and the equal-proportion restored bending geometry is ensured, which ensures that the curvature radius of the measurement section of the test reinforcement 10 is consistent with the target working condition. This is the key basic variable for studying the influence of "bending curvature".

[0044] Furthermore, by independently controlling the concrete strength and selecting a matching concrete strength grade according to the target pipe diameter, pouring concrete of the test strength in the concrete mold, and testing to reach the test strength after 28 days of curing, this variable can be set independently of the curvature radius. This is the key basic variable for studying the influence of "concrete strength".

[0045] Furthermore, the cured concrete contact formwork 11 provides a hard, stable and contact surface with the properties of actual engineering materials for the test reinforcement 10, simulating the bonding and restraint state between the reinforcement and the concrete in the actual structure, and providing a rigid and real contact interface for the test experiment.

[0046] Furthermore, by independently controlling the curvature and the concrete strength grade, one variable can be changed while the other is fixed in the subsequent test experiments, so as to separate their respective influences on the prestress loss, thus realizing the decoupling basis of the "curvature" and "strength" variables.

[0047] S2: Pass the anchorage section of the test reinforcement 10 through the anchorage section baffle 14 and tighten the nut. Place a stress sensor between the nut and the anchorage section baffle 14 to monitor the stress change of the test reinforcement 10 in real time;

[0048] Specifically, after manufacturing the test reinforcement 10, pass the two ends of the test reinforcement 10 through the anchorage section steel pipe 7 and the tension section steel pipe 15 respectively, and carry out anchoring by pouring a bonded anchor of epoxy resin and cement into the anchorage section steel pipe 7 and the tension section steel pipe 15. The anchorage section steel pipe 7 and the tension section steel pipe 15 are polished with sandpaper and cleaned with alcohol to remove rust. The epoxy resin is left standing at room temperature for 7 days to ensure full curing. The anchorage section steel pipe 7 and the tension section steel pipe 15 are hollow threaded steel pipes. [[ID=!16]]

[0049] Furthermore, pass the anchorage section steel pipe 7 at one end of the test reinforcement 10 through the anchorage section baffle 14. After placing a stress sensor between the nut and the anchorage section baffle 14, tighten the nut to provide a stable reaction point for the tensioning process and ensure the effective progress of the test. The stress sensor can directly and real-time measure the actual stress state at the anchorage end, which is one of the most critical input data for calculating the prestress loss rate. It directly reflects that after the tensioning is completed, due to various loss factors, the test reinforcement 10 maintains an effective stress at the anchorage end.

[0050] S3: Bend the measurement section of the test reinforcement 10 along the bending curvature of the concrete contact formwork 11 and attach it to the contact interface of the concrete contact formwork 11;

[0051] Specifically, through the contact interface where the concrete touches the formwork 11, the measuring section of the test tendon 10 is precisely presented with the target curvature, thus simulating the actual working condition of the bent tendon and ensuring that the geometric shape of the test tendon 10 in the bending section is consistent with the experimental design.

[0052] S4: Pass the tensioning section of the test tendon 10 through the tensioning section baffle 2, apply a preset initial tensioning stress, tighten the nut after reaching the preset value, remove the temporary loading device and let it stand for a preset time to eliminate the residual stress.

[0053] Specifically, pass the steel pipe 15 of the tensioning section at one end of the test tendon 10 through the tensioning section baffle 2, nut, stool 5, hollow jack 4, movable steel plate 3 and nut in sequence, and tighten the nut at the movable steel plate 3.

[0054] Furthermore, use the hollow jack 4 to start applying the load, thereby applying a preset initial tensioning stress to the test tendon 10, applying a controllable and known initial stress level in the test tendon 10, and establishing an initial prestressed state.

[0055] Furthermore, when the preset tensioning stress is reached, tighten the nut at the tensioning section baffle 2 to lock the stress state, loosen the nut at the movable steel plate 3, remove the hollow jack 4, and let it stand for a preset time. The main purpose of the standing process is to allow some instantaneous and time-independent losses (such as anchor deformation, compaction of the spacer gap, etc.) and the internal residual stress generated during the tensioning process to fully occur and stabilize. The locked initial tensioning stress provides a starting value for calculating the prestress loss rate for calculating the prestress loss rate.

[0056] S5: Paste the fiber Bragg grating strain sensor 17 at the maximum bending moment point and the inflection point of the measuring section of the test tendon 10. After maintaining the load stably for a specified time, synchronously collect the data of the stress sensor in the anchorage section and the data of the fiber Bragg grating strain sensor 17 in the measuring section, and calculate the prestress loss rate through the mainframe 8.

[0057] Among them, through the independent control of the bending curvature radius and concrete strength in S1, and the stress stabilization process in S4, calculate and analyze the collected data to realize the decoupled analysis of the following parameters:

[0058] The influence of tendon diameter on the prestress loss rate;

[0059] The influence of tendon bending curvature on the prestress loss rate;

[0060] The influence of concrete strength on the prestress loss rate.

[0061] Specifically, the fiber grating strain sensor 17 is connected to the fiber grating demodulator 9 through a fiber optic lead 16. The fiber grating demodulator 9 acquires the data collected by the fiber grating strain sensor 17 and transmits the data to the host computer 8. By systematically changing the tendon diameter (replacing the test tendons with different diameters), the bending curvature (replacing the bending baffle 12 of the test section of S1), and the concrete strength (using concretes with different strengths in S1), and repeating the steps of S2 - S5, multiple sets of experimental data can be obtained. Utilizing the variable independent control ability established in S1 and the accurate and stable loss rate data provided by S4 / S5, the host computer can isolate the specific influence law of each single factor (diameter, curvature, strength) on the prestress loss rate, achieve true decoupling analysis, and through modular combination to replace the prototype pipe test, while truly simulating the working state of the PCCP prestressed steel wire, effectively shortening the test cycle and reducing the test cost.

[0062] In S5, taking one end of the measurement section of the test tendon 10 near the tensioning section as the starting point, the midpoint of the measurement section of the test tendon 10 is the point with the maximum bending moment, and the inflection point is at the quarter position of the measurement section of the test tendon 10.

[0063] Specifically, when the test tendon 10 bends along the arc of the radius of curvature, if the measurement section is a symmetric arc section (such as a semi - circle or a 1 / 4 circle), the curvature at the midpoint position is the largest, and the peak value of the tensile stress generated by the tendon under bending appears here. The fiber grating strain sensor 17 at the midpoint directly monitors the most unfavorable stress point of the test tendon 10 in the bending state, reflects the tensile deformation and local stress concentration caused by the maximum bending moment, and through the data at this point, the sensitivity of the tendon diameter and bending curvature to the prestress loss can be analyzed, and the bending effect influence can be quantified.

[0064] Furthermore, in the symmetric bending section, the theoretical value of the bending moment at the inflection point (such as the 1 / 4 arc position) is zero. Here, the tendon is only subjected to axial tensile force and there is no additional bending stress. The strain data at the inflection point only reflects the action of the axial tensile force. The difference from the midpoint data can isolate the additional stress caused by pure bending, thus separating the bending effect and the friction effect. If the strain value at the inflection point is lower than the stress conversion value at the anchorage end, it indicates the existence of friction slip loss at the tendon - concrete interface, and this loss is related to the concrete strength and the surface characteristics of the tendon, thus identifying the interface friction loss. By comparing the inflection point data of different concrete specimens, the influence of concrete strength on the interface bond slip (friction loss) can be independently analyzed, thus decoupling the influence of concrete strength.

[0065] Furthermore, the selection of the midpoint and the 1 / 4 point utilizes the symmetry of the bending section to ensure that the theoretical mechanical state of the measuring point position is clear (the bending moment at the midpoint is the largest, and the bending moment at the 1 / 4 point is zero), avoiding errors caused by random point selection. The 1 / 4 point is located in the transition zone at the beginning and end of the bending section, where the curvature changes significantly, and it can sensitively capture the local detachment or slip behavior between the tendon and the concrete, thus optimizing the sensor layout.

[0066] The grating strain sensors 17 are pasted on both the top and the outer side of the point with the maximum bending moment and the inflection point.

[0067] Specifically, when the reinforcing material is bent, there is a tensile and compressive stress gradient in the cross-section. The top (convex side) is dominated by tensile stress, and the outer side (concave side) is dominated by compressive stress. The two-way pasted sensors can simultaneously monitor the maximum tensile strain (top) and the maximum compressive strain (outer side) within the same cross-section.

[0068] Furthermore, the contact pressure distribution between the reinforcing material and the concrete formwork is uneven. The contact pressure on the concave side (outer side) is greater, and the friction effect is stronger. The friction on the convex side (top) may decrease due to micro-separation. The spatial non-uniformity of the interface constraint can be quantified by comparing the data in both directions.

[0069] The prestress loss rate in S5 The calculation formula is:

[0070] ;

[0071] Wherein, is the slip amount of the reinforcing material-concrete interface, =80 - 120GPa / mm is the slip influence coefficient, is the preset initial tensile stress, is the elastic modulus of the reinforcing material, is the cross-sectional area of the reinforcing material, is the coordinate of the point with the maximum bending moment.

[0072] The radius of curvature of the bending baffle in the test section in S1 Satisfies: ;

[0073] Wherein, is the target pipe diameter, and the range of the target pipe diameter is 2200mm ≤ ≤ 4000mm, is the pipe wall thickness compensation coefficient, and the range of the pipe wall thickness compensation coefficient is 50mm ≤ ≤ 100mm.

[0074] The diameter range of the test reinforcing material 10 in S1 is 5 - 9mm, and the concrete strength range is C30 - C60.

[0075] The standing time in S4 Satisfies: ;

[0076] Wherein, is the stress relaxation factor, and the value range is .

[0077] A PCCP prestress loss test device, comprising:

[0078] A base plate 1, an anchorage section baffle 14 and a tensioning section baffle 2, and all three are independently arranged;

[0079] A plurality of test section bending baffles 12, and the plurality of test section bending baffles 12 are welded to the base plate 1 with different preset curvatures, and the overall prototype pipe to be tested is simulated in proportion through a detachable combined structure to truly simulate the actual working state of the PCCP;

[0080] Transverse reinforcing ribs 13, which are evenly distributed on the top of the test section bending baffle 12 along the bending path of the test section bending baffle 12 to ensure the integrity of the device and prevent the test reinforcement from being pulled off.

[0081] Triangular braces 6 are arranged on both the nut side surface of the anchorage section baffle 14 and the bending inner surface of the test section bending baffle 12.

[0082] Specifically, the stability of the anchorage section baffle 14 and the test section bending baffle 12 is enhanced by the arranged triangular braces 6.

[0083] A detachable hollow jack 4 is arranged on one side of the tensioning section baffle 2, and the hollow jack 4 is used to apply a preset initial tensile stress to the test reinforcement.

[0084] Example 1: Bending test

[0085] Target parameter combination

[0086] Target pipe diameter: ;

[0087] Equivalent curvature radius: ;

[0088] Reinforcement diameter: ;

[0089] Concrete strength: ;

[0090] Initial tensile stress: ;

[0091] Static time: 72 hours.

[0092] S1: Determine the equivalent bending curvature radius according to the target pipe diameter , select the test section bending baffle 12 that matches the equivalent bending curvature radius, and pour concrete with the same strength as the target pipe core concrete at the test section bending baffle 12 based on the equivalent bending curvature radius , cure for 28 days until the test reaches the preset strength to obtain the concrete contact template 11 with curvature;

[0093] S2: Pass the anchorage section of the test tendon 10 through the anchorage section baffle 14 and tighten the nut. Place a stress sensor between the nut and the anchorage section baffle 14 to monitor the stress change of the test tendon 10 in real time;

[0094] S3: Bend the measurement section of the test tendon 10 along the bending curvature of the concrete contact formwork 11 and attach it to the contact interface of the concrete contact formwork 11;

[0095] S4: Pass the tension section of the test tendon 10 through the tension section baffle 2 and apply a preset initial tensile stress , after reaching the preset value, tighten the nut, remove the temporary loading device and let it stand for 72 hours to eliminate the residual stress;

[0096] S5: Paste the fiber Bragg grating strain sensor 17 at the maximum bending moment point and the inflection point of the measurement section of the test tendon 10. After maintaining the load stably for a specified time, synchronously collect the data of the stress sensor in the anchorage section and the data of the fiber Bragg grating strain sensor 17 in the measurement section, and calculate the prestress loss rate through the mainframe 8:

[0097] Midpoint:

[0098] 1 / 4 point:

[0099]

[0100] Traditional loss rate:

[0101] Formula correction:

[0102] Decouple the influence of tendon diameter on the prestress loss rate, the influence of tendon bending curvature on the prestress loss rate, and the influence of concrete strength on the prestress loss rate according to the data, and obtain an analysis report.

[0103] Example 2: Straight line test (control group)

[0104] Parameter configuration (only the curvature is different from Example 1), other parameters are the same as in Example 1;

[0105] S1: Remove the test section bending baffle 12;

[0106] S2: Pass the anchorage section of the test tendon 10 through the anchorage section baffle 14 and tighten the nut. Place a stress sensor between the nut and the anchorage section baffle 14 to monitor the stress change of the test tendon 10 in real time;

[0107] S3: Pass the tension section of the test tendon 10 through the tension section baffle 2 to make the test tendon 10 in a straight line state, and apply a preset initial tensile stress , after reaching the preset value, tighten the nut, remove the temporary loading device and let it stand for 72 hours to eliminate the residual stress;

[0108] S4: After maintaining the load steadily for the specified time, synchronously collect the data of the stress sensors in the anchorage section and the data of the grating strain sensors 17 in the measurement section, and calculate the prestress loss rate through the host computer 8:

[0109]

[0110] Midpoint strain:

[0111] Traditional loss rate:

[0112] Formula correction: Strain difference (approaching 0), slip , no curvature correction is required.

[0113] According to the calculated data, compare the bending data with the straight-line data, decouple the influence of the tendon diameter on the prestress loss rate, the influence of the tendon bending curvature on the prestress loss rate, and the influence of the concrete strength on the prestress loss rate, and obtain an analysis report.

[0114] The technical scope of the present invention is not limited to the content in the above description. Those skilled in the art can make various deformations and modifications to the above embodiments without departing from the technical idea of the present invention, and these deformations and modifications should all fall within the protection scope of the present invention.

Claims

1. A method for testing the prestress loss of PCCP, characterized in that, It includes the following steps: S1: Determine the equivalent bending curvature radius according to the target pipe diameter, select a test section bending baffle that matches the equivalent bending curvature radius, pour concrete with the same strength as the target pipe core concrete at the test section bending baffle based on the equivalent bending curvature radius, cure it until the test reaches the preset strength, and obtain a concrete contact template with curvature; S2: Pass the anchorage section of the test reinforcement through the anchorage section baffle and tighten the nut. Place a stress sensor between the nut and the anchorage section baffle to monitor the stress change of the test reinforcement in real time; S3: Bend the measuring section of the test reinforcement along the bending curvature of the concrete contact template and attach it to the contact interface of the concrete contact template; S4: Pass the tensioning section of the test reinforcement through the tensioning section baffle, apply a preset initial tensioning stress, tighten the nut after reaching the preset value, remove the temporary loading device and let it stand for a preset time to eliminate the residual stress; S5: Paste grating strain sensors at the maximum bending moment point and the inflection point of the measuring section of the test reinforcement. After maintaining the load stably for a specified time, synchronously collect the data of the stress sensor in the anchorage section and the data of the grating strain sensor in the measuring section, and calculate the prestress loss rate through the host computer; Among them, through the independent control of the bending curvature radius and concrete strength in S1, and the stress stabilization process in S4, the collected data is calculated and analyzed to realize the decoupled analysis of the following parameters: The influence of the reinforcement diameter on the prestress loss rate; The influence of the reinforcement bending curvature on the prestress loss rate; The influence of the concrete strength on the prestress loss rate.

2. The method for testing the prestress loss of PCCP according to claim 1, wherein: In S5, starting from one end of the measuring section of the test reinforcement close to the tensioning section, the maximum bending moment point is the midpoint of the measuring section of the test reinforcement, and the inflection point is at the quarter position of the measuring section of the test reinforcement.

3. A method for testing the prestress loss of PCCP according to claim 2, characterized in that: Grating strain sensors are pasted on the top and outer sides of the maximum bending moment point and the inflection point.

4. A method for testing the prestress loss of PCCP according to claim 3, characterized in that: The prestress loss rate in S5 The calculation formula is as follows: ； Among them, is the slip amount at the interface between the reinforcement and concrete, = 80 - 120 GPa / mm is the slip influence coefficient, is the preset initial tension stress, is the elastic modulus of the reinforcement, is the cross-sectional area of the reinforcement, is the coordinate of the point with the maximum bending moment.

5. A method for testing the prestress loss of PCCP according to claim 1, characterized in that: The radius of curvature of the bending baffle in the test section in S1 Satisfies: ; Among them, is the target pipe diameter, and the range of the target pipe diameter is 2200mm ≤ ≤ 4000mm, is the pipe wall thickness compensation coefficient, and the range of the pipe wall thickness compensation coefficient is 50mm ≤ ≤ 100mm.

6. A method for testing the prestress loss of PCCP according to claim 5, characterized in that: In S1, the diameter range of the test reinforcement is 5 - 9 mm, and the concrete strength range is C30 - C60.

7. A method for testing the prestress loss of PCCP according to claim 4, characterized in that: The standing time in S4 satisfies: ; Among them, is the stress relaxation factor, and its value range is .

8. A PCCP prestress loss testing device, according to any one of claims 1-7, a PCCP prestress loss testing method, characterized in that, It includes: A base plate, an anchorage section baffle, and a tensioning section baffle, and all three are independently arranged; Multiple test section bending baffles. The multiple test section bending baffles are welded on the base plate with different preset curvatures, and the overall prototype pipe to be tested is simulated proportionally through a detachable combined structure to truly simulate the actual working state of PCCP; Transverse stiffeners, which are evenly distributed on the top of the test section bending baffle along the bending path of the test section bending baffle to ensure the integrity of the device and prevent the test reinforcement from being pulled off.

9. The PCCP prestress loss testing device according to claim 8, characterized in that: Triangular braces are arranged on the side surface of the nut of the anchorage section baffle and the inner bending surface of the test section bending baffle.

10. A PCCP prestress loss testing device according to claim 9, characterized in that: A detachable hollow jack is arranged on one side of the tensioning section baffle, and the hollow jack is used to apply a preset initial tensioning stress to the test reinforcement.

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