Prestressed tendon shrinkage loss detection method and system based on unloading flow detection

Abstract

The present invention belongs to the field of anchoring engineering technology, and specifically discloses a method and system for detecting prestressed tendon shrinkage loss based on unloading flow detection. The method comprises the following steps: no-load debugging, collecting the total stroke of the jack piston and the cumulative flow corresponding to the total stroke, calculating the cross-sectional area of ​​the oil cavity of the jack piston cylinder as a fixed calibration parameter; load debugging, setting the force level of the jack, obtaining a first-order or second-order curve force calibration equation representing the jack output force under stable output of different force levels using the oil pump pressure value, and using the coefficient in the curve calibration equation as the force calibration parameter; determining the maximum output force F of the jack in the load-holding state max , jack piston displacement L max , the displacement of the jack piston in the anchored state L min , calculate the reverse displacement of the jack piston movement and the prestressed tendon shrinkage loss. Using this technical solution, based on unloading flow detection, the prestressed tendon shrinkage loss can be automatically, accurately and in real time measured.

Description

Technical Field

[0001] The present invention belongs to the technical field of anchoring engineering, and relates to a method and system for detecting shrinkage loss of prestressed tendons based on unloading flow detection. Background Art

[0002] During the anchoring process, prestressed tendons shrink due to relative displacement between the various components of the anchor and between the anchor and the tendon, as well as local plastic deformation. Prestressed anchoring processes using clip-type anchors rely on tendon shrinkage to achieve anchorage, while also requiring precise control of the prestress loss caused by this shrinkage to establish accurate prestress in the structure and ensure the quality and safety of the engineering structure. Therefore, accurate measurement and calculation of tendon shrinkage loss has become a fundamental requirement for determining engineering design parameters, controlling construction processes, and evaluating quality inspections.

[0003] Currently, there are two main methods for measuring prestressed tendon shrinkage in the industry: traditional manual measurement and automatic measurement using displacement sensors. Manual measurement uses a steel ruler or micrometer to directly measure the extended length of the jack cylinder after tensioning to a controlled stress, minus the exposed length of the cylinder after unloading. Automatic measurement using displacement sensors uses linear displacement meters, such as pull-rod displacement meters, wire displacement meters, and laser displacement meters, attached to the jack to measure the change in cylinder length during tensioning.

[0004] For example, patent CN105841577A discloses a method for accurately measuring the shrinkage of prestressed aqueduct loops or vertical prestressed tendons. This method uses a structural frame composed of steel bars, steel plates, and screws, and then uses a magnetic base to mount a micrometer for measurement. This method still falls under the traditional manual measurement method. The device installation, operation control, reading and recording, and data processing during the measurement process rely entirely on manual labor, failing to effectively eliminate interference from human factors. Furthermore, the process requires close observation and recording of data by personnel, which also poses certain safety risks. Patent CN103306488A discloses a prestressed tendon tensioning shrinkage automatic control system. This system achieves automatic measurement by mounting a displacement sensor on the outside of the hydraulic jack of the automatic tensioning system. However, the frequent disassembly and movement of the jack during use results in a high rate of damage to the displacement sensor, frequently leading to unreliable measurement results. Furthermore, the shrinkage itself is a small variable (the standard requires less than 6 mm), which is affected by various factors such as the machining accuracy of the attached device, installation errors, and wear and tear of the jack during operation. This makes it difficult to reliably guarantee the accuracy of the measurement results. Summary of the Invention

[0005] The purpose of the present invention is to provide a method and system for detecting prestressed tendon shrinkage loss based on unloading flow detection, so as to achieve accurate and real-time measurement of prestressed tendon shrinkage loss.

[0006] In order to achieve the above-mentioned object, the basic scheme of the present invention is: a method for detecting prestressed tendon shrinkage loss based on unloading flow detection, comprising the following steps:

[0007] During no-load debugging, collect the total stroke of the jack piston and the cumulative flow corresponding to the total stroke, and calculate the cross-sectional area of ​​the oil cavity of the jack piston cylinder as a fixed calibration parameter;

[0008] Load debugging, set the force level of the jack, obtain the first-order or second-order curve force calibration equation of the jack output force expressed by the oil pump pressure value under stable output of different force levels, and the coefficient in the curve calibration equation is used as the force calibration parameter;

[0009] Select a reference entity structure to perform prestressing according to the force level, obtain a first-order or second-order curve displacement calibration equation in which the piston displacement is expressed in terms of cumulative flow, and use the coefficients in the calibration equation as displacement value calibration parameters for the data acquisition device;

[0010] When the actual tensioning construction begins, according to the operating pressure P of the oil pump t , flow Q t Flow rate V t and flow direction The value and state changes of the load holding state and anchoring state during the tensioning process are determined and the data of this stage are extracted. The maximum output force F of the jack in the load holding state is determined using the force calibration equation and force calibration parameters. max , using the displacement calibration equation and displacement value calibration parameters to obtain the jack piston displacement L max , using fixed calibration parameters to obtain the jack piston displacement L in the anchored state min ;

[0011] The maximum output force F of the jack in the load-holding state is obtained max , jack piston displacement L max , jack piston displacement L min Calculate the reverse displacement of the jack piston motion;

[0012] Based on the theory of prestressed tendon tension loss, the prestressed tendon shrinkage loss is calculated using the reverse displacement of the jack piston movement.

[0013] The working principle and beneficial effects of this basic solution are: this technical solution is based on unloading flow detection, system debugging and static parameter acquisition, and static parameter configuration. In subsequent detection, the jack output force value can be calculated in real time based on the collected pressure value.

[0014] To accurately measure the jack's output force and its corresponding displacement, the data acquisition device needs to be dynamically calibrated based on actual on-site construction conditions, and the flow-displacement calculation parameters within the data acquisition device need to be corrected. Data acquisition is performed at the start of tensioning construction to identify the state and calculate the actual shrinkage of the prestressed tendons during the tensioning process. This allows for automatic, accurate, and real-time measurement of prestressed tendon shrinkage losses, providing a reliable basis for determining design parameters, construction parameters, and quality inspection parameters for prestressed engineering projects, thereby avoiding the problems of insufficient reliability, accuracy, precision, and pertinence found in existing technologies.

[0015] Furthermore, during no-load debugging, the total stroke of the jack piston and the cumulative flow corresponding to the total stroke are collected, and the cross-sectional area of ​​the oil cavity of the jack piston cylinder is calculated as a fixed calibration parameter method:

[0016] Use a vernier caliper to measure the total stroke L of the piston of the tension jack cylinder J , that is, the displacement range during the tensioning construction process;

[0017] Obtain the cumulative flow Q corresponding to the total no-load stroke through the flow sensor J , calculate the cross-sectional area A of the oil chamber inside the piston cylinder of the jack J ,for:

[0018]

[0019] During no-load debugging, collect the total stroke of the jack piston and the cumulative flow corresponding to the total stroke, and calculate the cross-sectional area of ​​the oil cavity of the jack piston cylinder to facilitate subsequent use.

[0020] Furthermore, load debugging is performed to set the force level of the jack, and the first-order or second-order curve force calibration equation is obtained, in which the output force of the jack is expressed by the oil pump pressure value under stable output of different force levels. The coefficient in the curve calibration equation is used as the force calibration parameter in the following way:

[0021] Install the jack and standard dynamometer on the reaction device, start the tensioning hydraulic oil pump, drive the jack to operate, start from 10% or 20% of the rated force of the jack, and load step by step in increasing order until the maximum force value, and the force points at each level are distributed as evenly as possible;

[0022] During the load state debugging, after the force value points at each level remain stable, record the corresponding standard dynamometer and pressure values ​​to obtain the tension jack output force F t The pressure value P of the sensor of the data acquisition device t The linear or quadratic force calibration equation is:

[0023] F t =aP t2 +bP t +c, or F t =aP t +b

[0024] Among them, a, b, and c are the coefficients of the fitting curve.

[0025] Install a jack and a standard dynamometer on the reaction device (a portal frame or tension rod with sufficient rigidity and stability) and perform load adjustment for easy use.

[0026] Furthermore, a reference entity structure is selected to perform prestressing according to the force level, and a first-order or second-order curve displacement calibration equation representing the piston displacement in terms of cumulative flow is obtained. The coefficients in the calibration equation are used as displacement calibration parameters of the data acquisition device in the following method:

[0027] The displacement L of the jack piston during the tensioning process is obtained t The accumulated flow rate Q of the sensor with the data acquisition device t The linear or quadratic curve displacement calibration equation is:

[0028] L t =a′Q t 2 +b′Q t +c′ or L t =a′Q t +b′;

[0029] The parameters a′, b′, and c′ in the calibration equation are used as displacement calibration parameters, and the displacement value of the jack cylinder piston is calculated in real time according to the collected flow value.

[0030] The coefficients in the calibration equation serve as the displacement value calibration parameters of the data acquisition device. Through dynamic debugging, the working state condition parameters of the data acquisition device are determined and configured, including but not limited to the mode conversion trigger threshold (such as starting pressure, starting flow, etc.), sampling parameters (such as sampling frequency, start time, end time, etc.), data processing parameters (storage capacity, storage time, transmission rules, etc.), equipment identity information (such as pump station number, jack number, sensor number, etc.), etc.

[0031] Furthermore, the maximum output force F of the jack in the load-holding state is obtained. max , jack piston displacement L max , jack piston displacement L min The steps to calculate the reverse displacement of the jack piston motion are:

[0032] When the tensioning construction begins, the hydraulic oil pump starts and drives the jack to tension. When the starting pressure or starting flow reaches the preset trigger threshold, the pressure P of the oil pump during the tensioning process ist , flow Q t Flow rate V t and flow direction Conduct real-time detection;

[0033] By pressure P t , flow Q t Flow rate V t and flow direction The value and state changes of are associated with the tensioning oil pump and forward working state to establish a state relationship diagram of the tensioning construction process;

[0034] The real-time detection data obtained through the state relationship diagram can identify the status of the oil pump and jack and the state of the tensioning construction process. When , it means the oil pump and jack are in the unloading working state, and the tensioning construction process is in the anchoring state;

[0035] Using the calibration parameters, the maximum output force F of the jack in the load-holding state is calculated. max and the jack piston displacement L max and the displacement L of the jack piston in the anchored state min , using the formula L draw =L max -L min Calculate and obtain the reverse displacement L of the jack during the unloading and anchoring process draw , which is the actual shrinkage of the prestressed tendons during the tensioning process.

[0036] Simple operation and easy calculation.

[0037] Furthermore, based on the theory of prestressed tendon tension loss and using the reverse displacement of the jack piston movement, the method for calculating the prestressed tendon shrinkage loss is as follows:

[0038] According to the prestressed tendon tension loss theory, the shrinkage loss value σ is calculated draw :

[0039]

[0040] Among them, L eff is the length of the prestressed tendons in tensioning construction, A P is the cross-sectional area of ​​the prestressed anchor cable, E P is the elastic modulus of the prestressed anchor cable, L draw It is the reverse displacement of the jack during the unloading and anchoring process, that is, the actual shrinkage of the prestressed tendons during the tensioning process.

[0041] According to the theory of prestressed tendon tensioning loss, the shrinkage loss value is calculated with high accuracy.

[0042] The present invention also provides a prestressed tendon shrinkage loss detection system based on unloading flow detection, comprising a data acquisition module and a processing module, wherein the data acquisition module is installed between the hydraulic passage of the tensioning hydraulic oil pump and the tensioning jack and is used to collect information on pressure, flow, flow velocity, and flow direction;

[0043] The input end of the processing module is connected to the output end of the data acquisition module, and the processing module executes the method of the present invention to perform prestressed tendon shrinkage loss detection.

[0044] This system uses data acquisition modules and processing modules to achieve automatic, accurate and real-time measurement of prestressed tendon shrinkage loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Figure 1 It is a flow chart of the prestressed tendon shrinkage loss detection method based on unloading flow detection of the present invention. DETAILED DESCRIPTION

[0046] The following describes embodiments of the present invention in detail. 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 intended only to explain the present invention and are not to be construed as limiting the present invention.

[0047] In the description of the present invention, it should be understood that the terms "longitudinal", "transverse", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention.

[0048] In the description of the present invention, unless otherwise specified and limited, it should be noted that the terms "installed", "connected" and "connected" should be understood in a broad sense. For example, it can be a mechanical connection or an electrical connection, or it can be the internal communication between two components. It can be a direct connection or an indirect connection through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms can be understood according to the specific circumstances.

[0049] The present invention discloses a method for detecting prestressed tendon shrinkage loss based on unloading flow detection, which realizes automatic, accurate and real-time measurement of prestressed tendon shrinkage loss, provides a true and reliable basis for determining design parameters, construction parameters and quality inspection parameters of prestressed engineering, and avoids the problems of insufficient reliability, accuracy, precision and pertinence in the prior art. Figure 1 As shown in FIG, the prestressed tendon shrinkage loss detection method includes the following steps:

[0050] A data acquisition device is installed between the hydraulic circuits of the tensioning hydraulic oil pump and the tensioning jack. The installation location can be at the oil outlet of the pump station, at the oil inlet of the tensioning jack, or at any position of the hydraulic oil pipe between the oil outlet of the pump station and the oil inlet of the jack. Various installation methods can be used, such as ferrule joints, articulated joints, flange joints, crimping joints, and quick joints. The specific specifications and models can be selected or processed according to the actual conditions of the oil pump and jack. The data acquisition device is internally integrated with sensor modules, sensor signal processing modules, and data processing modules for sensing and measuring multiple parameters such as pressure, flow, flow velocity, and flow direction. During the tensioning construction process, the working status and operating parameters of the oil pump and jack are collected, processed, stored, and transmitted in real time.

[0051] During no-load debugging, collect the total stroke of the jack piston and the cumulative flow corresponding to the total stroke, and calculate the cross-sectional area of ​​the oil cavity of the jack piston cylinder as a fixed calibration parameter;

[0052] Load debugging, set the force level of the jack, obtain the first-order or second-order curve force calibration equation of the jack output force expressed by the oil pump pressure value under stable output of different force levels, and the coefficient in the curve calibration equation is used as the force calibration parameter;

[0053] Select a reference entity structure to perform prestressing according to the force level, obtain a first-order or second-order curve displacement calibration equation in which the piston displacement is expressed in terms of cumulative flow, and use the coefficients in the calibration equation as displacement value calibration parameters for the data acquisition device;

[0054] When the actual tensioning construction begins, according to the operating pressure P of the oil pump t , flow Q t Flow rate V t and flow direction The value and state changes of the load holding state and anchoring state during the tensioning process are determined and the data of this stage are extracted. The maximum output force F of the jack in the load holding state is determined using the force calibration equation and force calibration parameters. max , using the displacement calibration equation and displacement value calibration parameters to obtain the jack piston displacement L max , using fixed calibration parameters to obtain the jack piston displacement L in the anchored state min ;

[0055] The maximum output force F of the jack in the load-holding state is obtained max , jack piston displacement L max , jack piston displacement L min Calculate the reverse displacement of the jack piston motion;

[0056] Based on the theory of prestressed tendon tension loss, the prestressed tendon shrinkage loss is calculated using the reverse displacement of the jack piston movement.

[0057] In a preferred embodiment of the present invention, during no-load debugging, the total stroke of the jack piston and the cumulative flow corresponding to the total stroke are collected, and the cross-sectional area of ​​the oil cavity of the jack piston cylinder is calculated as a fixed calibration parameter. The method is as follows:

[0058] Under no-load conditions, start the tensioning hydraulic oil pump with the data acquisition device installed, drive the jack, test the jack's piston movement during oil inlet and oil return, and check that all pipe connections are unobstructed, tight, and leak-free. Simultaneously, start the data acquisition device debugging mode and check its operating status, including sensor detection, signal acquisition and processing, and data storage and transmission functions.

[0059] Use a vernier caliper to measure the total stroke L of the piston of the tension jack cylinder J , that is, the displacement range during the tensioning construction process;

[0060] The cumulative flow Q corresponding to the total no-load stroke is obtained through the flow sensor in the data acquisition device J , calculate the cross-sectional area A of the oil chamber inside the piston cylinder of the jack J ,for:

[0061]

[0062] In a preferred embodiment of the present invention, load debugging is performed to set the force level of the jack, and a first-order or second-order curve force calibration equation is obtained in which the jack output force is expressed by the oil pump pressure value under stable output of different force levels. The coefficients in the curve calibration equation are used as force calibration parameters in the following manner:

[0063] Install the jack and standard dynamometer on the reaction device (a portal frame or tension rod with sufficient rigidity and stability), start the tensioning hydraulic oil pump with the data acquisition device installed, drive the jack to operate, and start loading from 10% or 20% of the rated force of the jack, in increasing order, until the maximum force value is reached. The force points at each level should be distributed as evenly as possible, generally not less than 5 points;

[0064] Test the operation of the hydraulic pump and jack under various load conditions, and check whether all pipe connections are unobstructed, tight, and leak-free. Simultaneously, activate the data acquisition device debugging mode and check the operating status of the data acquisition device, including sensor detection, signal acquisition and processing, data storage, and transmission functions.

[0065] During the load state debugging, after the force value points at each level remain stable, record the corresponding standard dynamometer and pressure values ​​to obtain the tension jack output force Ft The pressure value P of the sensor of the data acquisition device t The linear or quadratic force calibration equation is:

[0066] F t =aP t 2 +bP t +c, or F t =aP t +b

[0067] Among them, a, b, c are the coefficients and constant terms of the fitting curve, F t =aP t 2 +bP t In the equation a and b are the coefficients of the fitting curve, c is the constant term, and F t =aP t In +b, a is the coefficient of the fitting curve and b is the constant term.

[0068] The cross-sectional area A of the oil chamber of the piston cylinder inside the jack obtained during the no-load commissioning J As fixed parameters, they are configured into the system software. In subsequent tests, the displacement of the jack's top cylinder piston can be calculated in real time based on the collected flow value. Parameters a, b, and c in the calibration equation obtained during load commissioning are used as force calibration parameters for the data acquisition device and configured into the system software. In subsequent tests, the jack's output force can be calculated in real time based on the collected pressure value.

[0069] In a preferred embodiment of the present invention, a reference entity structure is selected to be prestressed according to the force level, a linear or quadratic displacement calibration equation is obtained in which the piston displacement is expressed as a cumulative flow rate, and the coefficients in the calibration equation are used as displacement calibration parameters of the data acquisition device in the following manner:

[0070] After the design values ​​(such as structural form, bundle arrangement, control stress, etc.), construction process parameters (such as initial stress value, tensioning grade value, tensioning sequence, theoretical elongation value, etc.), material parameters (such as steel strand length, cross-sectional area, elastic modulus, etc.), and equipment parameters (such as oil pump, jack specifications and models, and matching anchor fixture dimensions, etc.) are determined, in order to accurately measure the output force of the jack and its displacement at the corresponding moment, it is necessary to dynamically calibrate the data acquisition device in combination with the actual on-site construction conditions and correct the flow displacement calculation parameters inside the data acquisition device.

[0071] Select a physical structure with representative parameters for prestressing. After the preparation is completed, perform prestressing step by step according to the control stress of 10%, 20%, 40%, 60%, 80%, and 100%. After the force and displacement at each level remain stable, use a vernier caliper to measure the displacement value L of the oil cylinder piston.c , and record the cumulative flow value Q of the numerical acquisition device at the same time i and the displacement values ​​calculated based on the initial parameters

[0072] The displacement L of the jack piston during the tensioning process is obtained by the least squares method t The accumulated flow rate Q of the sensor with the data acquisition device t The linear or quadratic curve displacement calibration equation is:

[0073] L t =a′Q t 2 +b′Q t +c′ or L t =a′Q t +b′;

[0074] The parameters a′, b′, and c′ in the calibration equation are used as displacement value calibration parameters and configured into the system software. In subsequent tests, the displacement value of the jack cylinder piston can be calculated in real time based on the collected flow value.

[0075] Through dynamic debugging, the working state condition parameters of the data acquisition device are determined and configured, including but not limited to mode conversion trigger thresholds (such as starting pressure, starting flow, etc.), sampling parameters (such as sampling frequency, start time, end time, etc.), data processing parameters (storage capacity, storage time, transmission rules, etc.), equipment identity information (such as pump station number, jack number, sensor number, etc.), etc.

[0076] In a preferred embodiment of the present invention, the maximum output force F of the jack in the load-holding state is obtained. max , jack piston displacement L max , jack piston displacement L min The steps to calculate the reverse displacement of the jack piston motion are:

[0077] When the tensioning construction begins, the hydraulic oil pump starts and drives the jack to tension. When the starting pressure (such as P t ≥0.5MPa) or start flow (such as Q t ≥0) reaches the preset trigger threshold, the working mode of the data acquisition device is converted from the dormant state to the monitoring state, and the pressure P of the oil pump during the tensioning process is t , flow Q t Flow rate V t and flow direction Conduct real-time detection;

[0078] By pressure P t , flow Q t Flow rate V t and flow direction The value and state change of are associated with the tensioning oil pump and forward working state to establish the tensioning construction process state relationship diagram, as shown in Table 1;

[0079] Table 1 Status relationship of tensioning construction process

[0080]

[0081] Through the state relationship diagram and the real-time detection data obtained by the data acquisition device, the oil pump and jack status and the tensioning construction process status are identified. When , it means the oil pump and jack are in the unloading working state, and the tensioning construction process is in the anchoring state;

[0082] By extracting the data of the holding state and anchoring state during the tensioning process, the maximum output force F of the jack in the holding state is calculated using the above calibration parameters and calculation formula. max and the jack piston displacement L max and the displacement L of the jack piston in the anchored state min , using the formula L draw =L max -L min Calculate and obtain the reverse displacement L of the jack during the unloading and anchoring process draw , which is the actual shrinkage of the prestressed tendons during the tensioning process.

[0083] In a preferred embodiment of the present invention, based on the theory of prestressed tendon tension loss, the method for calculating the prestressed tendon shrinkage loss is to use the reverse displacement of the jack piston movement:

[0084] According to the prestressed tendon tension loss theory, the shrinkage loss value σ is calculated draw :

[0085]

[0086] Among them, L eff is the length of the prestressed tendons in tensioning construction, A P is the cross-sectional area of ​​the prestressed anchor cable, E P is the elastic modulus of the prestressed anchor cable, L draw It is the reverse displacement of the jack during the unloading and anchoring process, that is, the actual shrinkage of the prestressed tendons during the tensioning process.

[0087] The present invention also provides a prestressed tendon shrinkage loss detection system based on unloading flow detection, including a data acquisition module and a processing module. The data acquisition module is installed between the hydraulic passages of the tensioning hydraulic oil pump and the tensioning jack, and is used to collect pressure, flow, flow velocity, and flow direction information.

[0088] The input of the processing module is electrically connected to the output of the data acquisition module, and the processing module executes the method of the present invention to detect prestressed tendon shrinkage loss. This system utilizes the data acquisition module and the processing module to achieve automatic, accurate, and real-time measurement of prestressed tendon shrinkage loss.

[0089] Throughout this specification, reference to terms such as "one embodiment," "some embodiments," "examples," "specific examples," or "some examples" means that a specific feature, structure, material, or characteristic described in conjunction with that embodiment or example is included in at least one embodiment or example of the present invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

[0090] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to the embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the claims and their equivalents.

Claims

1. A method for detecting prestressed tendon shrinkage loss based on unloading flow detection, characterized in that: The steps include: During no-load debugging, collect the total stroke of the jack piston and the cumulative flow corresponding to the total stroke, and calculate the cross-sectional area of ​​the oil cavity of the jack piston cylinder as a fixed calibration parameter; Load debugging, set the force level of the jack, obtain the first-order or second-order curve force calibration equation of the jack output force expressed by the oil pump pressure value under stable output of different force levels, and the coefficient in the curve calibration equation is used as the force calibration parameter; Select a reference entity structure to perform prestressing according to the force level, obtain a first-order or second-order curve displacement calibration equation in which the piston displacement is expressed in terms of cumulative flow, and use the coefficients in the calibration equation as displacement value calibration parameters for the data acquisition device; When the actual tensioning construction begins, according to the operating pressure P of the oil pump t , flow Q t Flow rate V t and flow direction The value and state changes of the load holding state and anchoring state during the tensioning process are determined and the data of this stage are extracted. The maximum output force F of the jack in the load holding state is determined using the force calibration equation and force calibration parameters. max , using the displacement calibration equation and displacement value calibration parameters to obtain the jack piston displacement L max , using fixed calibration parameters to obtain the jack piston displacement L in the anchored state min ; The maximum output force F of the jack in the load-holding state is obtained max , jack piston displacement L max , jack piston displacement L min Calculate the reverse displacement of the jack piston motion; Based on the theory of prestressed tendon tension loss, the prestressed tendon shrinkage loss is calculated using the reverse displacement of the jack piston movement; The maximum output force F of the jack in the load-holding state is obtained max , jack piston displacement L max , jack piston displacement L min The steps to calculate the reverse displacement of the jack piston motion are: When the tensioning construction begins, the hydraulic oil pump starts and drives the jack to tension. When the starting pressure or starting flow reaches the preset trigger threshold, the pressure P of the oil pump during the tensioning process is t , flow Q t Flow rate V t and flow direction Conduct real-time detection; By pressure P t , flow Q t Flow rate V t and flow direction The value and state changes of are associated with the tensioning oil pump and forward working state to establish a state relationship diagram of the tensioning construction process; The real-time detection data obtained through the state relationship diagram can identify the status of the oil pump and jack and the state of the tensioning construction process. When , it means the oil pump and jack are in the unloading working state, and the tensioning construction process is anchoring in progress, where ↑ means increase or positive; ↓ means decrease or reverse; Using the calibration parameters, the maximum output force F of the jack in the load-holding state is calculated. max and the jack piston displacement L max and the displacement L of the jack piston in the anchored state min , using the formula L draw =L max -L min Calculate and obtain the reverse displacement L of the jack during the unloading and anchoring process draw , which is the actual shrinkage of the prestressed tendons during the tensioning process; Based on the theory of prestressed tendon tension loss and the reverse displacement of the jack piston movement, the method for calculating the prestressed tendon shrinkage loss is as follows: According to the prestressed tendon tension loss theory, the shrinkage loss value σ is calculated draw : Among them, L eff is the length of the prestressed tendons in tensioning construction, A P is the cross-sectional area of ​​the prestressed anchor cable, E P is the elastic modulus of the prestressed anchor cable, L draw It is the reverse displacement of the jack during the unloading and anchoring process, that is, the actual shrinkage of the prestressed tendons during the tensioning process.

2. The method for detecting prestressed tendon shrinkage loss based on unloading flow detection according to claim 1, characterized in that: During no-load debugging, collect the total stroke of the jack piston and the cumulative flow corresponding to the total stroke, and calculate the cross-sectional area of ​​the oil cavity of the jack piston cylinder as a fixed calibration parameter: Use a vernier caliper to measure the total stroke L of the piston of the tension jack cylinder J , that is, the displacement range during the tensioning construction process; Obtain the cumulative flow Q corresponding to the total no-load stroke through the flow sensor J , calculate the cross-sectional area A of the oil chamber inside the piston cylinder of the jack J ,for:

3. The method for detecting prestressed tendon shrinkage loss based on unloading flow detection according to claim 1, characterized in that: Load debugging, set the force level of the jack, obtain the first-order or second-order curve force calibration equation of the jack output force expressed by the oil pump pressure value under stable output of different force levels, and the coefficient in the curve calibration equation is used as the force calibration parameter as follows: Install the jack and standard dynamometer on the reaction device, start the tensioning hydraulic oil pump, drive the jack to operate, start from 10% or 20% of the rated force of the jack, and load step by step in increasing order until the maximum force value, and the force points at each level are distributed as evenly as possible; During the load state debugging, after the force value points at each level remain stable, record the corresponding standard dynamometer and pressure values ​​to obtain the tension jack output force F t The pressure value P of the sensor of the data acquisition device t The linear or quadratic force calibration equation is: F t =aP t 2 +bP t +c, or F t =aP t +b Among them, a, b, and c are the coefficients and constant terms of the fitting curve.

4. The method for detecting prestressed tendon shrinkage loss based on unloading flow detection according to claim 1, characterized in that: Select a reference entity structure and perform prestressing according to the force level, obtain a first-order or second-order curve displacement calibration equation in which the piston displacement is expressed as cumulative flow, and use the coefficients in the calibration equation as displacement calibration parameters of the data acquisition device as follows: The displacement L of the jack piston during the tensioning process is obtained t The accumulated flow rate Q of the sensor with the data acquisition device t The linear or quadratic curve displacement calibration equation is: L t =a′Q t 2 +b′Q t +c′ or L t =a′Q t +b′; The parameters a′, b′, and c′ in the calibration equation are used as displacement calibration parameters, and the displacement value of the jack cylinder piston is calculated in real time according to the collected flow value.

5. A prestressed tendon shrinkage loss detection system based on unloading flow detection, characterized in that: It includes a data acquisition module and a processing module. The data acquisition module is installed between the hydraulic passage of the tensioning hydraulic oil pump and the tensioning jack and is used to collect pressure, flow, flow velocity and flow direction information; The input end of the processing module is connected to the output end of the data acquisition module, and the processing module executes the method according to any one of claims 1 to 4 to perform prestressed tendon shrinkage loss detection.

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