Prestressed tendon pull-back device

Abstract

The present invention provides a prestressed tendon pullback device, comprising: a precise cable force increment measurement device, mounted on the prestressed tendon, for monitoring whether the cable force of the prestressed tendon at the location thereof has increased; a prestressed tendon fixed pullback device, mounted on the prestressed tendon and spaced apart from the precise cable force increment measurement device, comprising two fixing devices, at least two screws, and a crank; the two fixing devices being spaced apart and both removably clamped to the prestressed tendon; the two fixing devices being connected by screws; all the screws being parallel and spaced apart; one end of each screw being rotatably connected to the same fixing device, the other end being threaded through another fixing device, one of the screws being provided with a crank at the other end, and all the screws rotating synchronously; a fiber optic Bragg grating (FBG) mounted on each screw for measuring the stress applied to each screw; and a receiving and transmitting device connected to each fiber optic Bragg grating. The device is capable of operating at high altitudes, is convenient to use, and provides accurate measurements.

Description

Technical Field

[0001] The invention relates to the technical field of prestressed steel measurement in civil engineering, in particular to a prestressed steel bar pulling-back device. Background Art

[0002] Prestressed structures are widely used in large structures such as large bridges, due to their advantages of improving component crack resistance and stiffness, enhancing fatigue resistance, saving materials, and reducing deadweight. The safety of prestressed structures during their service life is closely related to the amount of prestress within them. However, as the structure's service life increases, the prestress within the structure gradually decreases, diminishing the advantages provided by prestressed structures and seriously threatening their safety. Therefore, it is necessary to measure the effective prestress within prestressed structures to ensure their safety.

[0003] Chinese invention patent application number CN201910443598.4 provides an in-situ testing method for the mechanical properties of corroded prestressed tendons. The testing apparatus employed in this method consists of a main steel arm, side steel arms, a screw, a nut, a jack, a pressure sensor, an extensometer, and a clip. The two side steel arms are connected to the main steel arms via screws and nuts at one end to form a loading frame. Tapered holes are provided at the other end. The test prestressed tendons are anchored in the tapered holes of the two steel arms via clips. Jacks and pressure sensors are positioned sequentially inside the two steel arms, and pressure is applied via the jacks to form a lever-loaded system. An extensometer is used to measure tendon deformation. By extrapolating the readings from the extensometer and pressure sensor, mechanical properties such as the load-deformation relationship of the corroded prestressed tendons can be determined. This measurement method enables in-situ testing of the mechanical properties of corroded prestressed tendons, providing a true reflection of the tendon's stress state and avoiding the errors associated with traditional testing methods that involve tensioning and removing the tendons before conducting mechanical property tests. However, this method requires applying force to one section of the prestressed tendon through a jack, and then measuring the stress of the prestressed tendon. As we know, bridges are suspended. To use a jack for measurement, the jack needs to be moved to a high altitude. The jack is heavy and not easy to move. In addition, the jack requires oil to support its work. It is not convenient to replenish the oil source during high-altitude operations. Therefore, the existing measurement method is not convenient for measuring the prestress of prestressed structures at high altitudes. Summary of the Invention

[0004] In view of the above, it is necessary to provide a prestressed tendon pull-back device that can be used at high altitudes and is easy to use and accurate in measurement.

[0005] In order to achieve the above object, the technical solution adopted by the present invention is:

[0006] A prestressed tendon pull-back device, comprising

[0007] The cable force increment precision measuring device is installed on the prestressed tendon to monitor whether the cable force of the prestressed tendon at the location has increased;

[0008] A prestressed tendon fixing and pulling-back device is installed on the prestressed tendon and is spaced apart from the cable force increment precision measuring device. The device comprises two fixing devices, at least two screw rods and a crank. The two fixing devices are spaced apart and can be detachably clamped on the prestressed tendon. The two fixing devices are connected by screw rods. All the screw rods are parallel and spaced apart. One end of each screw rod is rotatably connected to the same fixing device, and the other end is threaded through another fixing device. One of the screw rods is provided with a crank at the other end, and all the screw rods rotate synchronously.

[0009] Fiber Bragg grating (FBG), installed on each lead screw, used to measure the stress on each lead screw;

[0010] The receiving and transmitting device is installed on the screw rod and is not located on the end of the screw rod through which the fixing device is threaded. The receiving and transmitting device is connected to each fiber Bragg grating and is used to receive the detection value of the fiber Bragg grating and transmit it to the terminal device of the central control system;

[0011] The above-mentioned prestressed tendons are located at the opening of the prestressed component to be tested, and both ends thereof are affected by the prestressed component to be tested.

[0012] Preferably, the fixing device includes two fixing plates, the middle parts of the two fixing plates are clamping areas, the clamping areas of the two together form a clamping space for clamping the prestressed tendons, and the two ends of the two fixing plates are detachably connected by connecting parts; each fixing plate is provided with a wire rod.

[0013] Preferably, four screw rods are provided, and the four screw rods are arranged around the circumference of the prestressed tendon.

[0014] Preferably, all the screw rods are linked together by a synchronous connection assembly.

[0015] Preferably, the synchronous connection assembly is detachably mounted on the screw rod.

[0016] Preferably, the cable force increment precision measurement device includes a cable force tester, a transmission layer and a display layer; the cable force tester includes an upper clamping ring, a lower clamping ring, four connecting rods, four strain gauges, a temperature compensation strain gauge, and a strain acquisition instrument. The upper clamping ring and the lower clamping ring are parallel and facing each other, and the middle part of the two has a clamping through hole for the prestressed tendons to pass through. The aperture of the clamping through hole is slightly smaller than the diameter of the prestressed tendons. The upper clamping ring and the lower clamping ring are connected by four connecting rods, which are arranged at intervals and surround the circumference of the clamping through hole. Each connecting rod is composed of two force transmission rods and a deformation rod connected in series, wherein the deformation rod is located between the two force transmission rods, a strain gauge is installed in the middle of each deformation rod, and a temperature compensation strain gauge is installed in the middle of one of the force transmission rods of one of the four connecting rods. The temperature compensation strain gauge and the four strain gauges are all connected to the strain collector; the transmission layer includes a 4G / 5G signal transmitter and a cloud, and the strain collector is connected to the cloud via a 4G / 5G signal transmitter; the display layer includes the terminal device, and the terminal device is wirelessly connected to the cloud.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention discloses a prestressed tendon pull-back device. Compared with the previous method of applying force with a jack and then measuring with a strain gauge, the pull-back device has the advantages of being easy to move, easy to use, and capable of high-altitude operation. It can easily, accurately, and efficiently realize the pull-back work of the prestressed tendon and obtain the original prestress in the prestressed tendon, which is convenient for the subsequent measurement of the prestress inside the prestressed structure, and then timely reinforce or take other remedial measures for structures with low prestress values ​​or large losses to ensure structural safety.

[0019] 2. The present invention fills the gap in previous prestressed tendon pull-back devices and has guiding significance for the development and setting of subsequent prestressed tendon pull-back devices.

[0020] 3. The present invention has wide applicability, is easy to construct, has simple structural calculations, is easy to operate, and has high promotion value. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 1. It is a schematic structural diagram of the prestressed tendon pull-back device of the present invention when it is installed on the prestressed tendon;

[0022] Figure 2 It is a structural schematic diagram of a cable force tester in the cable force increment precision measurement device of the present invention;

[0023] Figure 3 It is a side view of the fixing device of the present invention.

[0024] Description of main component symbols

[0025] In the figure: cable tension tester 1, upper clamping ring 1.1, lower clamping ring 1.2, deformation rod 1.3, bolt 1.4, strain gauge 1.5, temperature compensation strain gauge 1.6, force transmission rod 1.7, fixing device 2, fixing plate 2.1, connecting piece 2.2, screw 3, transmission assembly 4, crank 5, prestressed tendon 6.

[0026] The following specific embodiments will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0027] See also Figures 1 to 3 In a preferred embodiment of the present invention, a prestressed tendon pull-back device comprises

[0028] A precise cable force increment measuring device is installed on the prestressed tendon 6 to monitor whether the cable force of the prestressed tendon 6 at the location thereof has increased;

[0029] A prestressed tendon fixing and pulling-back device is installed on the prestressed tendon 6 and is spaced apart from the cable force increment precision measuring device. It includes two fixing devices 2, at least two screw rods 3, and a crank 5. The two fixing devices 2 are spaced apart and can be detachably clamped on the prestressed tendon 6. The two fixing devices 2 are connected by screw rods 3. All screw rods 3 are parallel and spaced apart. One end of each screw rod 3 is rotatably connected to the same fixing device 2, and the other end is threaded through another fixing device 2. One of the screw rods 3 is provided with a crank 5 at the other end. All screw rods 3 rotate synchronously.

[0030] A fiber Bragg grating (FBG) is provided on each screw rod 3 and is used to measure the stress on each screw rod 3;

[0031] The receiving and transmitting device is installed on the screw rod 3 and is not located on the end of the screw rod 3 where the fixing device 2 is threaded through the screw rod 3. It is connected to each fiber Bragg grating and is used to receive the detection value of the fiber Bragg grating and transmit it to the terminal device of the central control system;

[0032] The above-mentioned prestressed tendons 6 are located at the opening of the prestressed component to be tested, and both ends thereof are affected by the prestressed component to be tested.

[0033] The present invention clamps and fixes a section of prestressed tendon 6 exposed to the outside through a prestressed tendon fixing and pulling-back device, and is able to pull back this section of prestressed tendon 6, and the pulling-back only acts on this section of prestressed tendon 6. When the pulling-back force is greater than the prestress of this section of prestressed tendon 6, the pulling-back force acts on the peripheral prestressed tendon 6 connected to this section of prestressed tendon 6. That is, when the pulling-back force of this section of prestressed tendon 6 is not large, the peripheral prestressed tendon 6 will not be affected by the pulling-back device and maintains its original state. When the pulling-back force is large, the pulling-back force applied by the pulling-back device not only offsets the original prestress of this section of prestressed tendon 6, but also generates additional tensile force. The additional tensile force acts on the peripheral prestressed tendon 6, which will cause the prestressed tendon 6 to deform. Therefore, by observing whether the peripheral prestressed tendon 6 is deformed, it is possible to know whether the pulling-back force is appropriate, and the original prestress of the prestressed tendon 6 can be known based on the pulling-back force at the moment of deformation, thereby realizing the measurement of the internal prestress of the prestressed tendon 6.

[0034] In the present invention, the prestressed tendon fixing and pulling back device clamps and fixes a section of prestressed tendon 6 through two fixing devices 2, connects the two fixing devices 2 through a screw rod 3 and applies force to the two fixing devices 2 to achieve pulling back, and the screw rod 3 is driven to rotate by the crank 5. Compared with the jack, it is easier to achieve high-altitude operation, and it is easier to move and disassemble.

[0035] In this embodiment, considering that the two ends of the prestressed tendon 6 are not open, the existing prestressed tendon 6 anchor cannot be used directly. The two fixing devices 2 are specifically clamped and fixed on the prestressed tendon 6 in the following manner: Figure 3The fixing device 2 includes two fixing plates 2.1, and the middle parts of the two fixing plates 2.1 are clamping areas. The clamping areas of the two together form a clamping space for clamping the prestressed tendon 6. The two ends of the two fixing plates 2.1 are detachably connected by a connecting piece 2.2. The connecting piece 2.2 can be a bolt and nut assembly, or it can be other structures; a wire rod 3 is provided on each fixing plate 2.1; before clamping and fixing, the two fixing plates 2.1 are separated. When clamping and fixing are required, the two fixing plates 2.1 are facing each other, and the prestressed tendon 6 is placed in the clamping area of ​​the two, and then the two ends of the two fixing plates 2.1 are connected respectively by the bolt and nut assembly until the two fixing plates 2.1 are both against the prestressed tendon 6 to achieve clamping and fixing, and then the wire rod 3 is rotated to bring the two fixing devices 2 closer to each other, so as to pull back a section of the prestressed tendon 6 clamped by the two. It should be noted that, in order to facilitate installation, in actual production, the two fixing plates 2.1 of the two fixing devices 2 are connected one by one, that is, the two fixing plates 2.1 are connected at the same time by means of a screw rod 3, and the two fixing plates 2.1 are not two on the same fixing device 2, wherein one end of the screw rod 3 is rotatably connected to a fixing plate 2.1, and the other end is threaded through another fixing plate 2.1, and when the fixing device 2 clamps the prestressed tendon 6, the other end of the screw rod 3 is linked with the other screw rods 3 through the transmission assembly 4, so that shaking one screw rod 3 can drive the other screw rods 3 to rotate, that is, the transmission assembly 4 is a synchronous connection assembly, and all the screw rods 3 are linked and connected through the synchronous connection assembly.

[0036] As can be seen from the above, the screw rod 3 of the present invention is used as a pullback driving device. Preferably, four screw rods 3 are provided, and the four screw rods 3 are arranged around the circumference of the prestressed tendon 6 to balance the force of the fixing device 2 to pull back the prestressed tendon 6, so that the pullback effect is better, that is, two screw rods 3 are arranged at intervals on each fixed plate 2.1, and the two screw rods 3 are located on opposite sides of the clamping area of ​​the fixed plate 2.1, and the two are connected by a transmission assembly 4. In this way, the screw rods 3 on the same fixed plate 2.1 can rotate synchronously.

[0037] To facilitate installation, in particular, to facilitate the connection of the screw rods 3 between two fixing plates 2.1 on the same fixing device 2, preferably, the synchronous connection assembly is detachably mounted on the screw rod 3. In particular, the synchronous connection assembly of the screw rods 3 not on the same fixing plate 2.1 is detachably connected, and the synchronous connection assembly of two screw rods 3 on the same fixing plate 2.1 may be detachably connected or may not be detachably mounted on the screw rod 3. The synchronous connection assembly may be a gear assembly, a gear rack assembly, a synchronous belt, or a synchronous chain assembly.

[0038] In summary, it can be known that whether the peripheral prestressed tendon 6 is deformed or not is known by pulling back the prestressed tendon fixing and pulling back device, thereby measuring the prestress of the prestressed tendon 6. In the present invention, the force applied by the prestressed tendon fixing and pulling back device is measured by fiber optic Bragg grating, and all the screw rods 3 exert a force on the fixing device 2. Therefore, the stress measured by the fiber optic Bragg grating on all the screw rods 3 is added together to obtain the pull-back force applied by the prestressed tendon fixing and pulling back device. When the pull-back force happens to cause the peripheral prestressed tendon 6 to deform, the pull-back force at the moment of deformation is the original prestress of the prestressed tendon 6. Therefore, by obtaining the stress measured by the fiber optic Bragg grating at that moment, the original prestress of the prestressed tendon 6 can be obtained.

[0039] In the present invention, whether the peripheral prestressed tendons 6 are deformed during the application of the pull-back force is detected by a precise cable force increment measurement device. In this embodiment, the structure of the precise cable force increment measurement device is based on the prior art. For details, please refer to the Chinese utility model patent publication number CN 213301544 U for a precise cable force increment measurement device for bridge cables. The main structure of the precise cable force increment measurement device is as follows: Figure 2 The cable force increment precision measurement device includes a cable force tester 1, a transmission layer and a display layer; the cable force tester 1 includes an upper clamping ring 1.1, a lower clamping ring 1.2, four connecting rods, four strain gauges 1.5, a temperature compensation strain gauge 1.6, and a strain collector. The upper clamping ring 1.1 and the lower clamping ring 1.2 are parallel and facing each other, and the middle part of the two has a clamping through hole for the prestressed tendon 6 to pass through. The aperture of the clamping through hole is slightly smaller than the diameter of the prestressed tendon 6. The upper clamping ring 1.1 and the lower clamping ring 1.2 are connected by four connecting rods. The four connecting rods are arranged at intervals and surround the circumference of the clamping through hole. A connecting rod is composed of two force transmission rods 1.7 and a deformation rod 1.3 connected in series, wherein the deformation rod 1.3 is located between the two force transmission rods 1.7, and a strain gauge 1.5 is installed in the middle of each deformation rod 1.3. A temperature compensation strain gauge 1.6 is installed in the middle of one of the force transmission rods 1.7 of one of the four connecting rods, and the temperature compensation strain gauge 1.6 and the four strain gauges 1.5 are all connected to a strain collector; the transmission layer includes a 4G / 5G signal transmitter and a cloud, and the strain collector is connected to the cloud via the 4G / 5G signal transmitter; the display layer includes the terminal device, and the terminal device is wirelessly connected to the cloud.

[0040] That is, the aforementioned precise cable force increment measurement device clamps the peripheral prestressed tendons 6 through the clamping holes of the upper clamping ring 1.1 and the lower clamping ring 1.2 of the cable force tester 1. The upper clamping ring 1.1 and the lower clamping ring 1.2 are connected by a connecting rod. The connecting rod is composed of a force transmission rod 1.7 and a deformation rod 1.3. The deformation rod 1.3 can synchronously deform when the upper clamping ring 1.1 and the lower clamping ring 1.2 are displaced by the prestressed tendon 6 under force. This deformation is detected by the strain gauge 1.5 on the deformation rod 1.3. The deformation of the prestressed tendon 6 can be determined through the detection results of the strain gauge 1.5. The detection results of the strain gauge 1.5 are transmitted to the terminal device via the strain acquisition instrument and the transmission layer.

[0041] The specific measurement principle and other structures of the above-mentioned precise measurement device for increasing cable force are detailed in the existing patents and will not be described in detail here.

[0042] The specific implementation process of the prestressed tendon pull-back device provided by the present invention is as follows:

[0043] S1: Open the prestressed component to be tested for prestressing to expose the prestressed tendons 6 inside;

[0044] S2: The fixing device 2 is placed on the prestressed tendon 6 and clamped and fixed by the connector 2.2. Then the cable force increment precision test device is installed on the outer prestressed tendon 6 outside the prestressed tendon fixing and pulling device. The structure formed is as follows: Figure 1 As shown;

[0045] S3: By rotating the crank 5 and continuously applying force, monitor whether the incremental force of the peripheral prestressed tendons 6 changes until it reaches the critical point between incremental change and invariance. The force value measured by the fiber optic Bragg grating on the screw rod 3 corresponding to the critical point is the pull-back force value corresponding to the prestressed tendon fixed pull-back device, and the pull-back force value is the original prestress value inside the measured prestressed component.

[0046] The above description is a detailed description of the preferred embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. Any equivalent changes or modifications completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A prestressed tendon pull-back device, characterized in that: include The cable force increment precision measuring device is installed on the prestressed tendon to monitor whether the cable force of the prestressed tendon at the location has increased; A prestressed tendon fixing and pulling-back device is installed on the prestressed tendon and is spaced apart from the cable force increment precision measuring device. The device comprises two fixing devices, at least two screw rods and a crank. The two fixing devices are spaced apart and can be detachably clamped on the prestressed tendon. The two fixing devices are connected by screw rods. All the screw rods are parallel and spaced apart. One end of each screw rod is rotatably connected to the same fixing device, and the other end is threaded through another fixing device. One of the screw rods is provided with a crank at the other end, and all the screw rods rotate synchronously. Fiber Bragg grating (FBG), installed on each lead screw, used to measure the stress on each lead screw; The receiving and transmitting device is installed on the screw rod and is not located on the end of the screw rod through which the fixing device is threaded. The receiving and transmitting device is connected to each fiber Bragg grating and is used to receive the detection value of the fiber Bragg grating and transmit it to the terminal device of the central control system; The above-mentioned prestressed tendons are located at the opening of the prestressed component to be tested, and both ends thereof are affected by the prestressed component to be tested.

2. A prestressed tendon pull-back device according to claim 1, characterized in that: The fixing device includes two fixing plates, the middle parts of the two fixing plates are clamping areas, and the clamping areas of the two together form a clamping space for clamping prestressed tendons. The two ends of the two fixing plates are detachably connected by connecting pieces; each fixing plate is provided with a wire rod.

3. The prestressed tendon pull-back device according to claim 1, characterized in that: The four screw rods are arranged around the circumference of the prestressed tendons.

4. The prestressed tendon pull-back device according to claim 1, characterized in that: All the screw rods are linked together through synchronous connection components.

5. The prestressed tendon pull-back device according to claim 4, characterized in that: The synchronous connection assembly is detachably mounted on the screw rod.

6. The prestressed tendon pull-back device according to claim 1, characterized in that: The cable force increment precision measurement device includes a cable force tester, a transmission layer and a display layer; the cable force tester includes an upper clamping ring, a lower clamping ring, four connecting rods, four strain gauges, a temperature compensation strain gauge, and a strain acquisition instrument. The upper clamping ring and the lower clamping ring are parallel and facing each other, and the middle part of the two has a clamping through hole for the prestressed tendons to pass through. The aperture of the clamping through hole is slightly smaller than the diameter of the prestressed tendons. The upper clamping ring and the lower clamping ring are connected by four connecting rods. The four connecting rods are arranged at intervals and surround the circumference of the clamping through hole. A connecting rod is composed of two force transmission rods and a deformation rod connected in series, wherein the deformation rod is located between the two force transmission rods, a strain gauge is installed in the middle of each deformation rod, and a temperature compensation strain gauge is installed in the middle of one of the force transmission rods of one of the four connecting rods. The temperature compensation strain gauge and the four strain gauges are all connected to a strain collector; the transmission layer includes a 4G / 5G signal transmitter and a cloud, and the strain collector is connected to the cloud via a 4G / 5G signal transmitter; the display layer includes the terminal device, and the terminal device is wirelessly connected to the cloud.

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