Prestress same-bundle non-uniformity detection method

Abstract

The invention provides a method for detecting unevenness of the same pre-stress bundle, which comprises the following steps of: simultaneously performing counter-pulling on counter-pulling sections of a whole bundle of steel strands by adopting tension test equipment, and stretching the whole bundle of steel strands; with the stretching of the steel strands, the steel strands in the working anchor are sequentially withdrawn batch by batch from the working anchor from small to large according to the originally applied prestress, and corresponding time sequence impact response data are generated; and the unevenness value of the same bundle is obtained by analyzing the time sequence impact response data and reversely decomposing the reverse pulling process data of the whole bundle of steel strands. According to the one-time counter-pulling method for the whole steel strand, the problems that in one-by-one counter-pulling, instruments and equipment are difficult to install, the steel strand in the center of a working anchor is missed in detection, the detection result is inaccurate, and the detection efficiency is low can be solved, the accuracy of the effective prestress non-uniformity detection result is improved, the implementation efficiency of the detection work is improved, and the detection cost is reduced. The labor intensity of field detection work is reduced, and the repeatability of detection instrument equipment installation and data acquisition work is reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of prestressed anchor cable detection, and particularly relates to a method for detecting the unevenness of the same bundle of prestress. Background Art

[0002] In prestressed engineering structures, for prestressed tendons with large continuous lengths, large single-bundle steel bar contents, and high tensioning tonnages, wedge-type multi-hole anchorages are often used for prestress anchoring. Since the steel strands inevitably cross and wind around each other during the process of threading through the ducts, it is difficult to ensure the synchronous and uniform stress of each steel strand during tensioning. Some steel strands with larger forces may be close to or exceed the yield strength and are extremely prone to fracture, while some steel strands with smaller forces are extremely prone to slippage. An excessively high unevenness of prestress tensioning is not only a quality hazard for the early fatigue or even fracture of prestressed tendons but also directly leads to serious quality problems in the subsequent engineering structure.

[0003] Currently, for the detection of effective prestress, the most widely used and mature method in the industry is the reverse tension method, also known as the pull-off method, re-tension method, lift-off method, etc. The basic principle is to perform reverse tension on the anchored prestressed steel strands, establish a force balance relationship between the inside (anchored section) and the outside (reverse tension section) of the prestressed component with the basic position of the actual anchoring point as the center, and determine the effective prestress under the anchor by analyzing the stress-strain relationship of the steel strands during the reverse tension process using the inflection point method. For example, a prestress wedge-type anchor under-tensioning force testing device disclosed in CN201610474275.8, or a cable anchor force detection device disclosed in CN201922213724.5.

[0004] Generally, when the number of steel strands in the same duct is not large and the steel strand combing and threading process is strictly controlled, and each steel strand can be basically guaranteed to be parallel to each other and not wind around in the duct, the method of detecting the effective prestress under the anchor by detecting the prestress of each strand one by one is applicable to checking the unevenness of the same bundle of effective prestress under the anchor. However, in actual situations, the number of steel strands in a large number of prestressed ducts is large and the ducts are long, especially the longitudinal prestressed tendons in long-span bridge projects and the large-tonnage prestressed anchor cables in slope or foundation pit anchoring projects. When using the method of detecting the prestress of each strand one by one to detect the unevenness of the effective prestress under the anchor of the same bundle, the following technical problems mainly exist: 1) One is the problem that it cannot be detected during the implementation process. Due to the limited position size space on the anchor of the steel strand, it is impossible to install a jack for tensioning each strand one by one during the reverse tension process, and only a few steel strands at the edge positions can be selected for detection; 2) The other is the problem that the actual result cannot be accurately detected. Since the distribution and mutual influence of the steel strands in the duct are unknown, the accuracy of the result detected by tensioning each strand one by one cannot be evaluated, and the credibility of the detected value is reduced; 3) The third problem is the low detection efficiency. Due to the large number of steel strands and the long exposed sections after tensioning, the installation of instruments and equipment for testing each strand is demanding, difficult, time-consuming and labor-intensive.

[0005] After searching, no similar technical solution to the present invention has been disclosed. Summary of the invention

[0006] The present invention aims to solve the technical problems existing in the prior art, and the purpose of the present invention is to provide a method for detecting the non-uniformity of prestressed same-beam.

[0007] To achieve the above-mentioned purpose, the present invention adopts the following technical scheme: a method for detecting the non-uniformity of the same bundle of prestressed wires, comprising the following steps: using a tensioning test device to simultaneously perform a reverse pulling on the reverse pulling section of the entire bundle of steel strands, and the entire bundle of steel strands is stretched; during the reverse pulling process, as the steel strands are stretched, the steel strands in the working anchor are withdrawn from the working anchor in batches from small to large according to the original applied prestress, and corresponding time series impulse response data are generated; by analyzing the time series impulse response data, the reverse pulling process data of the entire bundle of steel strands is reversely decomposed to obtain the non-uniformity value of the same bundle.

[0008] The above technical scheme adopts the method of pulling back the whole bundle of steel strands at one time, which can avoid the problems of difficulty in installing instruments and equipment, missed detection of steel strands at the center of the working anchor, inaccurate detection results, and low detection efficiency in the method of pulling back one by one. It improves the accuracy of the effective prestress unevenness detection results, improves the implementation efficiency of the detection work, reduces the labor intensity of on-site detection work, reduces the repetitiveness of the installation of detection instruments and equipment and data collection work, and can be used to detect the effective prestress unevenness caused by the influence and interference of various factors during construction.

[0009] In a preferred embodiment of the present invention, during the process of unanchoring in batches, the number k of steel strands to be unanchored in the batch is determined, wherein the impulse response of each steel strand is: , in, is the time point when the i-th steel strand is unanchored, i is a positive integer, For The impulse response of the steel strand being unanchored at any moment. is The natural frequency of the strand at the moment of unmooring, is The stiffness coefficient of the steel strand unanchored at time The quality of the steel strand that is being unanchored at all times, is the damped oscillation frequency, ε is the damping ratio of the steel strand, is a step function; Time - series impulse response of the total output of the whole - bundle steel strands during the batch - by - batch anchor - withdrawal process , perform Fourier transform on and ; ; ; Obtain , perform inverse Fourier transform to obtain , wherein, is the Fourier transform operation, is the inverse Fourier transform operation, is the prestress of the steel strands that are anchor - withdrawn at time ; Obtain the prestresses of all steel strands , , ……, , where m is the total number of steel strands; Calculate the average prestress value: ; The in - bundle non - uniformity .

[0010] In the above - mentioned technical solution, by analyzing the time - series impulse response data, decomposing the data of the reverse - pulling process of the whole - bundle steel strands in reverse, obtaining the prestresses of all steel strands, the in - bundle non - uniformity value can be obtained; moreover, considering the situation that multiple steel strands in a batch are anchor - withdrawn simultaneously because the originally applied prestresses are the same, the missed detection is avoided, making the result more accurate. Additionally, the impulse response of the steel strands also takes into account the natural frequency and damped oscillation frequency of the anchor - withdrawn steel strands, making the detection result more accurate.

[0011] In a preferred embodiment of the present invention, the steps to determine the number k of the steel strands that are anchor - withdrawn in this batch are as follows: Obtain the number of saw - tooth waves after the effective prestress point in the time - series impulse response of the total output of the whole - bundle steel strands, that is, the total number J of batches of anchor - withdrawal; Obtain the difference between the ordinates of the peak and valley of the j - th saw - tooth wave , Determine the number of steel strands that are anchor - withdrawn corresponding to the j - th saw - tooth wave , , where M is the total number of steel strands, is rounding. If is calculated to be 0, then replace the 0 value with 1, and correspondingly subtract 1 from the smallest value corresponding to the decimal part of that exceeds 0.5. ​

[0012] The above technical solution adopts the rounding method when determining the number k of the steel strands to be unanchored in this batch, and takes into account the processing situation where the calculation result is 0, so that the result is more accurate.

[0013] In a preferred embodiment of the present invention, the strand bundle outside the prestressed component is fixed by a working anchor, the working anchor has a plurality of conical clip holes and a plurality of groups of working clips corresponding to the number of the whole strand bundle, the strands pass through the conical clip holes and are locked and fixed by the working clips; the tension test equipment includes a measurement and control device, a through-core jack and a tool anchor which are sequentially arranged and sleeved outside the whole strand bundle, the tool anchor has a plurality of conical clip holes and a plurality of groups of tool clips corresponding to the number of the whole strand bundle, the strands pass through the conical clip holes and are locked and fixed by the tool clips; the through-core jack The jack is used to pull back the whole bundle of steel strands at the same time. The measurement and control device includes a force sensor connected to the through-hole jack and arranged outside the whole bundle of steel strands. The signal output end of the force sensor is connected to the input end of the control system. The control system outputs the time-series impulse response of the total output of the whole bundle of steel strands. The inflection point method is used to determine the effective prestress under the anchor. When the effective prestress is reached, the steel strands are unanchored from the working anchor in batches from small to large. The impulse response of each steel strand is determined according to the unanchoring time. The measurement and control device collects the time-series impulse response of the total output of the whole bundle of steel strands during the unanchoring process in real time.

[0014] In the above technical scheme, the working anchor and the working clip are used to fix the part of the steel strand outside the prestressed component, the tool anchor and the tool clip are used to fix the steel strand with reaction force, the whole bundle of steel strands is tensioned by the through-hole jack, and the force sensor of the measurement and control device is used to collect the time-series impulse response of the total output of the whole bundle of steel strands during the unanchoring process by unanchoring in batches, the impulse response of each steel strand is determined according to the unanchoring time, and then the non-uniformity of the same bundle is obtained according to the aforementioned formula.

[0015] In a preferred embodiment of the present invention, a clip limit device is further provided between the working anchor and the measurement and control device. The clip limit device acts on the working anchor and has no direct effect on the working clip. It is used to limit the retreat distance of the working clip. The two ends of the force sensor are respectively abutted against the clip limit device and the through-hole jack.

[0016] The above technical solution limits the retraction length of the working clamp by setting a clamp limit device, eliminating the need for people to observe the retraction length of the working clamp with their eyes, thereby preventing the steel strand from being stretched too long and damaged.

[0017] In a preferred embodiment of the present invention, a limiting groove is provided on the clip limiting device to prevent the working clip from coming out too much.

[0018] In the above technical solution, the limiting groove limits the clamping piece, and the structure is simple and reliable.

[0019] In a preferred embodiment of the present invention, the clip limiting device has a plurality of threading holes corresponding to the number of the entire bundle of steel strands, and a limiting groove with a diameter larger than that of the working clip is provided at the front end of each threading hole, and a limiting step is formed between the limiting groove and the threading hole.

[0020] In the above technical solution, all the working clamps retreat in a limiting groove and are limited by a limiting step. Compared with providing a limiting groove for each working clamp, this solution has a simpler structure.

[0021] Additional aspects and advantages of the present invention will be given in part in the following description, and in part will become apparent from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which: Figure 1 It is a time-series impulse response diagram of the total output of the entire bundle of steel strands during the batch-by-batch anchor withdrawal process in the embodiment, and each fold in the diagram is the impact of anchor withdrawal.

[0023] Figure 2 It is a structural schematic diagram of the tension test equipment in the present invention.

[0024] The figure marks in the drawings of the specification include: prestressed component 1, steel strand 2, working anchor 3, working clip 4, clip limiting device 5, measurement and control device 6, through-core jack 7, tool anchor 8, tool clip 9, limiting groove 10. DETAILED DESCRIPTION

[0025] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and cannot be understood as limiting the present invention.

[0026] In the description of the present invention, it is to be understood that the terms “longitudinal”, “lateral”, “vertical”, “up”, “down”, “front”, “back”, “left”, “right”, “vertical”, “horizontal”, “top”, “bottom”, “inside” and “outside” etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore should not be understood as a limitation on the present invention.

[0027] In the description of the present invention, unless otherwise specified and defined, it should be noted that the terms "installation", "connection", and "linkage" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the communication inside two components. It can be directly connected or indirectly connected through an intermediate medium. For those of ordinary skill in the art, the specific meanings of the above terms can be understood according to specific circumstances.

[0028] The present invention provides a method for detecting the inhomogeneity of prestressed strands. As Figure 1 and Figure 2 shown, in a preferred embodiment, the detection method includes the following steps: Step 1: As Figure 2 shown, use a tension test device to simultaneously reverse-pull the reverse-pull section of the entire strand of steel strands 2. The entire strand of steel strands is stretched. Specifically, it can be done by hydraulic means, and a through-hole jack 7 is used to outwardly tension the entire strand of steel strands.

[0029] Step 2: During the reverse-pulling process, as the steel strands are stretched, each steel strand in the working anchor 3 is gradually released from the working anchor in ascending order according to the originally applied prestress magnitude (that is, the working clamping pieces 4 outside the steel strands 2 are gradually disengaged from the working anchor 3), and corresponding time-sequence impact response data as Figure 1 shown is generated.

[0030] Step 3: By analyzing the time-sequence impact response data, reverse-decompose the data of the reverse-pulling process of the entire strand of steel strands to obtain the inhomogeneity value of the same strand.

[0031] During the process of batch-by-batch release of the anchor, the impulse response of the steel strand is: , where is the time point when the i-th steel strand is released from the anchor, i is a positive integer, is the impulse response of the steel strand released from the anchor at moment, is the natural frequency of the steel strand released from the anchor at moment, is the stiffness coefficient of the steel strand released from the anchor at moment, m is the mass of the steel strand released from the anchor at moment, is the damped oscillation frequency, ε is the damping ratio of the steel strand, which can be determined through experiments, is the step function. Among them, when obtaining the damping ratio ε of the steel strand, a small perturbation is applied to the steel strand and then released to let it vibrate freely; record the change of the vibration attenuation amplitude with time; through the analysis of the vibration attenuation curve, use The damping ratio of the steel strand is calculated by a formula. A1 and A2 are the amplitudes of two adjacent vibration periods.

[0032] The time - series impulse response of the total output of the entire bundle of steel strands during the batch - by - batch anchor - releasing process , for and perform Fourier transform; ; ; Obtain , perform inverse Fourier transform, and obtain , wherein, is the Fourier transform operation, is the inverse Fourier transform operation, is the prestress of the steel strand when the anchor is released at time ; Obtain the prestresses of all steel strands , , ……, , m is the total number of steel strands; Calculate the average prestress value: ; The in - bundle non - uniformity .

[0033] Among them, the steps to determine the number k of steel strands for this batch of anchor - releasing are as follows: Obtain the number of saw - tooth waves after the effective prestress point in the time - series impulse response of the total output of the entire bundle of steel strands during anchor - releasing, that is, the total number J of batches of anchor - releasing; Obtain the difference between the ordinates of the peak and valley of the j - th saw - tooth wave , Determine the number of steel strands corresponding to the j - th saw - tooth wave during anchor - releasing , , where M is the total number of steel strands, is rounding. If a calculated value is 0, then replace the 0 value with 1, and correspondingly subtract 1 from the smallest value corresponding to the fractional part exceeding 0.5 in . For example, if there is a calculated result of 0.4 and the others are 0.8, 2.5, 2.6, 3.7 in , then the value of corresponding to 0.4 is taken as 1; the value of corresponding to 0.8 is taken as 1; the value of corresponding to 2.5 is taken as round(1.5)=2; the value of The value is 3; the corresponding value for 3.7 is 4.

[0034] As Figure 2 shown, in the art, the steel strand 2 located outside the prestressed member 1 in the steel strand 2 bundle is usually fixed by the working anchor 3. Among them, the working anchor 3 has a plurality of tapered wedge holes and multiple groups of working wedges 4 corresponding to the number of the entire steel strand 2 bundle. The steel strand 2 passes through the tapered wedge holes and is locked and fixed by the working wedges 4. The multiple tapered wedge holes of the working anchor 3 are adapted to the distribution of the entire steel strand 2 bundle. The working wedges 4 are of two-piece type and sleeved outside the steel strand 2. The working wedges 4 are inserted into the tapered wedge holes, and their tapered surfaces are matched to fix the steel strand 2, which is the prior art.

[0035] As Figure 2 shown, in the present invention, the tensioning test device includes a wedge limiting device 5, a measurement and control device 6, a through-hole jack 7, and a tool anchor 8 that are sequentially arranged outside the working anchor 3 from the outside and sleeved outside the entire steel strand 2 bundle. The tool anchor 8 has a plurality of tapered wedge holes and multiple groups of tool wedges 9 corresponding to the number of the entire steel strand 2 bundle. The steel strand 2 passes through the tapered wedge holes and is locked and fixed by the tool wedges 9. The structures of the tool anchor 8 and the tool wedges 9 are the same as those of the working anchor 3 and the working wedges 4, and are used for reaction force fixation of the steel strand 2. The wedge limiting device 5, the measurement and control device 6, and the through-hole jack 7 are clamped between the working anchor 3 and the tool anchor 8 and can transmit the acting force.

[0036] Among them, the measurement and control device 6 includes a force sensor (a force measuring ring) that is looped outside the entire steel strand 2 bundle and abuts against the wedge limiting device 5 and the through-hole jack 7 at both ends respectively. The signal output end of the force sensor is connected to the input end of the control system. The wedge limiting device 5 acts on the working anchor 3 and has no direct effect on the working wedges 4, and is used to limit the retraction distance of the working wedges 4 to prevent the steel strand 2 from being stretched too long and damaged. The through-hole jack 7 is sleeved outside the entire steel strand 2 bundle, and the through-hole jack 7 is used to simultaneously tension the entire steel strand 2 bundle.

[0037] When the through-hole jack 7 is tensioning, the force sensor of the measurement and control device 6 collects data, and the control system outputs the time-sequence impulse response of the total output of the entire steel strand bundle. The graph is as Figure 1 shown. The inflection point method is used to determine the effective prestress under the anchor. When the effective prestress is reached, multiple steel strands 2 are successively and gradually retracted from the working anchor 3 in ascending order. According to the retraction time, the impulse response of each batch of steel strands 2 is determined, and the measurement and control device 6 real-time collects the time-sequence impulse response of the total output of the entire steel strand bundle during the retraction process.

[0038] Specifically, as Figure 2As shown in the figure, the wedge clip limiting device 5 is provided with a limiting groove 10 for preventing the excessive withdrawal of the working wedge clip 4. The rear end of the wedge clip limiting device 5 has a plurality of wire passing holes corresponding to the number of the whole bundle of steel strands 2 for the steel strands 2 to pass through. The limiting groove 10 is arranged at the front end of the wedge clip limiting device 5 and communicates with each wire passing hole. The limiting groove 10 can cover all the wire passing holes, and a limiting step for restricting the backward distance of the working wedge clip 4 is formed between the limiting groove 10 and the wire passing holes.

[0039] During reverse pulling, slowly apply hydraulic oil pressure to jack out the hole-through jack 7, and tension the whole bundle of steel strands 2 outward ( Figure 2 to the right in the figure). Specifically, tensioning the steel strands 2 by the hole-through jack 7 is the prior art. Since the prestress applied to each steel strand 2 in the whole bundle of steel strands 2 is different, when the hole-through jack 7 reversely pulls the whole bundle of steel strands 2 with the same tensile force, the steel strands 2 with smaller prestress are more likely to be stretched, and the working wedge clips 4 outside them will first disengage from the working anchor 3 (that is, this steel strand 2 will first de-anchor), and then the steel strands 2 in the working anchor 3 will de-anchor in batches from the working anchor 3 in ascending order according to the prestress applied originally, and generate Figure 1 the corresponding time-sequence impact response data as shown in the figure.

[0040] It should be noted that the loading rate and data sampling rate during the tensioning process can be obtained through experiments to accurately obtain the impulse response of each steel strand 2.

[0041] In the description of this specification, the description with reference to terms such as "preferred embodiment", "one embodiment", "some embodiments", "example", "specific example" or "some examples" means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0042] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purposes of the present invention. The scope of the present invention is defined by the claims and their equivalents.

Claims

1. A method for detecting prestressed bundle non-uniformity, characterized in that: The steps include: The tension test equipment is used to simultaneously tension the tensioning section of the entire bundle of steel strands, and the entire bundle of steel strands is stretched; During the back-pulling process, as the steel strands are stretched, the steel strands in the working anchor are withdrawn from the working anchor in batches from small to large according to the original prestress applied, and the corresponding time-series impulse response data are generated; By analyzing the time series impulse response data, the reverse pulling process data of the whole bundle of steel strands is reversely decomposed to obtain the non-uniformity value of the same bundle.

2. A method for detecting prestressed strand non-uniformity according to claim 1, characterized in that: In the process of unanchoring in batches, the number k of steel strands to be unanchored in this batch is determined, where the impulse response of each steel strand is: ， in, is the time point when the i-th strand is unanchored, i is a positive integer, For The impulse response of the steel strand being unanchored at any moment. is The natural frequency of the strand at the moment of unmooring, is The stiffness coefficient of the steel strand unanchored at time The quality of the steel strand that is being unanchored at all times, is the damped oscillation frequency, ε is the damping ratio of the steel strand, is a step function; Time series impulse response of the total output of the whole strand during the batch withdrawal process ,right and Perform Fourier transform; ； ； get , perform inverse Fourier transform, and we get , in, is the Fourier transform operation, is the inverse Fourier transform operation, for The prestress of the steel strand when the anchor is withdrawn is ; Get the prestress of all steel strands , ,……, , m is the total number of steel strands; Calculate the average prestress value: ; Inhomogeneity of the same beam .

3. A method for detecting prestressed strand non-uniformity according to claim 2, characterized in that: The steps for determining the number k of the steel strands to be unanchored in this batch are: Obtain the number of sawtooth waves of anchor withdrawal after the effective prestressing point in the time series impulse response of the total output of the entire bundle of steel strands, that is, the total number of batches of anchor withdrawal J; Get the difference between the ordinates of the peak and trough of the jth sawtooth wave , Determine the number of unanchored steel strands corresponding to the jth sawtooth wave , , where M is the total number of steel strands, For rounding, if If the calculated value is 0, replace the 0 value with 1, and The smallest value whose decimal part exceeds 0.5 corresponds to Minus 1.

4. A method for detecting prestressed strand non-uniformity according to any one of claims 1 to 3, characterized in that: The steel strand bundle outside the prestressed component is fixed by a working anchor, wherein the working anchor has a plurality of conical clip holes and a plurality of groups of working clips corresponding to the number of the whole bundle of steel strands, and the steel strands pass through the conical clip holes and are locked and fixed by the working clips; The tension test equipment comprises a measurement and control device, a through-hole jack and a tool anchor which are sequentially arranged outside the whole bundle of steel strands, wherein the tool anchor has a plurality of conical clip holes and a plurality of sets of tool clips corresponding to the number of the whole bundle of steel strands, and the steel strands pass through the conical clip holes and are locked and fixed by the tool clips; The through-hole jack is used to simultaneously pull back the entire bundle of steel strands. The measurement and control device includes a force sensor connected to the through-hole jack and arranged outside the entire bundle of steel strands. The signal output end of the force sensor is connected to the input end of the control system. The control system outputs the time-series impulse response of the total output of the entire bundle of steel strands, and uses the inflection point method to determine the effective prestress under the anchor. When the effective prestress is reached, the steel strands are unanchored from the working anchor in batches from small to large. The impulse response of each steel strand is determined according to the unanchoring time, and the measurement and control device collects the time-series impulse response of the total output of the entire bundle of steel strands during the unanchoring process in real time.

5. A method for detecting prestressed strand non-uniformity according to claim 4, characterized in that: A clip limit device is also provided between the working anchor and the measurement and control device. The clip limit device acts on the working anchor and has no direct effect on the working clip. It is used to limit the retreat distance of the working clip. The two ends of the force sensor are respectively abutted against the clip limit device and the through-hole jack.

6. A method for detecting prestressed strand non-uniformity according to claim 5, characterized in that: The clip limiting device is provided with a limiting groove for preventing the working clip from coming out too much.

7. A method for detecting prestressed strand non-uniformity according to claim 6, characterized in that: The rear end of the clip limiting device has a plurality of threading holes corresponding to the number of the entire bundle of steel strands for the steel strands to pass through, the limiting groove is arranged at the front end of the clip limiting device and is connected to each threading hole, and a limiting step is formed between the limiting groove and the threading hole to limit the retreat distance of the working clip.

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