A bridge cable force increment precision measurement device and measurement method

Abstract

The present invention provides a precise measurement device and method for the incremental force of a bridge cable, wherein the 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 collector, wherein the upper clamping ring and the lower clamping ring are connected by four connecting rods, 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, a temperature compensation strain gauge is installed in the middle of one of the four connecting rods, and the temperature compensation strain gauge and the four strain gauges are all connected to the strain collector; the measurement method is carried out based on the above-mentioned measurement device. The device of the present invention can overcome the disadvantage that strain gauges cannot be installed on cables, has the advantages of simple principle and high test accuracy, and the measurement method enables dynamic and long-term monitoring, providing reliable guarantee for the measurement of cable force.

Description

Technical Field

[0001] The invention relates to the technical field of cables, and in particular to a device and method for accurately measuring the increment of cable force of a bridge cable. Background Art

[0002] Cables are important load-bearing structures of modern bridges, including cables of cable-stayed bridges, hangers of arch bridges, and external prestressing of some bridges. The determination of the state of bridge structures requires the measurement of cable forces, and the commonly used methods include: magnetic flux method, pressure ring method, and frequency method. Among them, the magnetic flux method has few practical cases in China and is not technically mature enough. The pressure ring method has high test accuracy and can meet the test requirements of cable force increments. However, the disadvantage of this method is that the pressure ring needs to be pre-set when the cable is installed. This method cannot be used on existing bridges, and the price of this method is very expensive and cannot be popularized on a large scale. The frequency method includes contact measurement and non-contact measurement. Both methods calculate the cable force through the relationship between frequency and cable force. Although it is very convenient in engineering application, the accuracy is not high. Obviously, all three methods have the problem of large errors, especially when used on short cables. In view of the above problems in the industry, it is urgent to propose a precise measurement device and method for the incremental force of bridge cables with simple testing and high testing accuracy. Summary of the invention

[0003] In order to achieve the above object, the technical solution adopted by the present invention is:

[0004] A bridge cable force increment precision measurement device, comprising a cable force tester, a transmission layer and a display layer; the cable force tester comprises 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 opposite, and the middle of the two has a clamping through hole for the cable to pass through, the aperture of the clamping through hole is slightly smaller than the cable diameter, 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. 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, and 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 through a 4G / 5G signal transmitter; the display layer includes a terminal device, and the terminal device is wirelessly connected to the cloud.

[0005] Preferably, the upper clamping ring and the lower clamping ring have the same structure, the upper clamping ring is in the shape of a circular ring and is evenly divided into two semicircular rings, both ends of each semicircular ring in the arc length direction are welded with ear plates, each ear plate is provided with a bolt hole, and the two semicircular rings are connected into a circular ring by inserting high-strength bolt threads into the bolt holes, and the inner ring of the circular ring is the clamping through hole.

[0006] Preferably, a thread structure is engraved on the wall of the clamping through hole.

[0007] Preferably, all the connecting rods have the same length, all the force transmission rods have the same material and size, all the force transmission rods are made of metal or alloy, and their cross-sections in the vertical length direction are circular structures.

[0008] Preferably, all the deformable rods are made of the same material and have the same size. All the deformable rods are made of metal or alloy, and their cross-section in the vertical length direction is a rectangular structure. The cross-sectional dimensions are smaller than the cross-sectional dimensions of the cable and the cross-sectional dimensions of the force transmission rod, and the elastic modulus of the deformable rod is smaller than the elastic modulus of the force transmission rod.

[0009] Preferably, the terminal device is a computer, a mobile phone or a tablet.

[0010] In addition, the present invention also provides a method for accurately measuring the increment of bridge cable force, the method adopting the above-mentioned device for accurately measuring the increment of bridge cable force to perform measurement, and comprises the following steps:

[0011] (1) Calibration of cable force tester;

[0012] (2) Install a cable force tester on the cable to be tested;

[0013] (3) Instrument connection, where all strain gauges and temperature compensation strain gauges of the cable force tester are connected to the strain acquisition instrument, which is connected to the cloud via the 4G / 5G signal transmitter of the transmission layer, and the terminal equipment of the display layer is wirelessly connected to the cloud;

[0014] (4) Setting parameters related to the cable to be tested, specifically setting the parameters of the cable to be tested on the terminal device, the parameters mainly including the elastic modulus E and the cross-sectional area A of the cable to be tested;

[0015] (5) Collection of cable force increments.

[0016] Preferably, in step (1), when the elastic modulus E and the cross-sectional area A of the cable to be tested are unknown, the range of the cable force tester is calibrated by experiment before the cable is installed. The specific steps are as follows:

[0017] 1) Select a cable of the same model as the cable to be tested;

[0018] 2) Install a cable force tester in the middle of the selected cable;

[0019] 3) Install both ends of the selected cable on the MTS universal testing machine;

[0020] 4) Apply different levels of load to the MTS universal testing machine and measure the strain data on the cable force tester at the same time;

[0021] 5) The tensile stiffness EA of the cable can be calibrated by the following formula:

[0022]

[0023] Where ΔF is the cable force increment, L d is the length of the deformed rod, L c is the distance between the upper clamping ring and the lower clamping ring, ε i is the strain value of the ith strain gauge, ε a is the strain value of the temperature compensation strain gauge, L T is the length of the dowel rod.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention provides a device for accurately measuring the increment of cable force in a bridge, which has the following advantages: wide applicability, simple operation, economical and reusable;

[0026] (2) The cable force tester of the present invention realizes strain amplification by utilizing the difference in tensile strength between the force transmission rod and the deformation rod, thereby improving the accuracy of the cable force increment test; at the same time, by arranging a temperature compensation sheet on the force transmission rod, the interference of temperature on the test result is effectively eliminated, thereby further improving the accuracy of the cable force measurement;

[0027] (3) The present invention provides a method for measuring the incremental force of bridge cables. The method can utilize wireless networks to achieve real-time data transmission, making monitoring dynamic and long-term, providing a reliable guarantee for the measurement of cable force, and also filling the gap in the field of dynamic cable monitoring. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 It is a structural schematic diagram of the cable force tester of the present invention.

[0029] Figure 2 It is a schematic diagram of the system structure of the measuring device of the present invention.

[0030] Main component symbols

[0031] In the figure: upper clamping ring 1, lower clamping ring 2, deformation rod 3, bolt 4, strain gauge 5, temperature compensation strain gauge 6, force transmission rod 7, cable tension tester 10, 4G / 5G signal transmitter 20, cloud 30, terminal device 40.

[0032] The following specific implementation manner will further illustrate the present invention in conjunction with the above-mentioned drawings. DETAILED DESCRIPTION

[0033] See also Figure 1 to Figure 2 In a preferred embodiment of the present invention, a device for accurately measuring the increment of bridge cable tension includes a cable tension tester 10, a transmission layer and a display layer.

[0034] The cable tension tester 10 includes an upper clamping ring 1, a lower clamping ring 2, four connecting rods, four strain gauges 5, a temperature compensation strain gauge 6, and a strain collector. The upper clamping ring 1 and the lower clamping ring 2 are parallel and opposite to each other, and the middle part of both has a clamping through hole for the cable to pass through. The aperture of the clamping through hole is slightly smaller than the cable diameter. The upper clamping ring 1 and the lower clamping ring 2 are connected by four connecting rods. The four connecting rods are arranged at intervals and surround the circumference of the clamping through hole. Each connecting rod is composed of two force transmission rods 7 and a deformation rod 3 connected in series, wherein the deformation rod 3 is located between the two force transmission rods 7, and a strain gauge 5 is installed in the middle of each deformation rod 3. A temperature compensation strain gauge 6 is installed in the middle of one of the force transmission rods 7 of one of the four connecting rods, and the temperature compensation strain gauge 6 and the four strain gauges 5 are all connected to the strain collector. The cable tension tester 10 of the present invention clamps the cable to be tested through the clamping through holes of the upper clamping ring 1 and the lower clamping ring 2, and connects the upper clamping ring 1 and the lower clamping ring 2 through a connecting rod, wherein the connecting rod is composed of a force transmission rod 7 and a deformation rod 3, and the deformation rod 3 can be deformed synchronously when the upper clamping ring 1 and the lower clamping ring 2 are displaced as the cable is subjected to force, and the deformation is detected by the strain gauge 5 on the deformation rod 3. The deformation of the cable can be known through the detection result of the strain gauge 5. In addition, the temperature compensation strain gauge 6 arranged on the force transmission rod 7 can be used to measure the deformation caused by temperature change, thereby improving the accuracy of the test of the device.

[0035] In this embodiment, the upper clamping ring 1 and the lower clamping ring 2 have the same structure. The upper clamping ring 1 is in the shape of a circular ring and is evenly divided into two semicircular rings. Ear plates are welded at both ends of each semicircular ring in the arc length direction. Bolt holes are provided on each ear plate. The two semicircular rings are connected into a circular ring by high-strength bolts 4 threadedly inserted into the bolt holes. The inner ring of the circular ring is the clamping through hole. Preferably, the hole wall of the clamping through hole is engraved with a threaded structure to increase the friction force of the upper clamping ring 1 and the lower clamping ring 2 clamping the cable. Preferably, all connecting rods have the same length, all force transmission rods 7 have the same material and size, and all force transmission rods 7 are made of metal or alloy, specifically, metal or alloy with light weight, large elastic modulus, and low temperature sensitivity, and the cross section in the vertical length direction is a circular structure. All the deformable rods 3 are made of the same material and have the same size. All the deformable rods 3 are made of metal or alloy, specifically, metal or alloy with light weight, small elastic modulus and low temperature sensitivity. The cross section of the deformable rod 3 in the vertical length direction is a rectangular structure. The cross section size is smaller than the cross section size of the cable and the cross section size of the force transmission rod 7. Specifically, the cross section size of the deformable rod 3 is much smaller than the cross section size of the cable and the cross section size of the force transmission rod 7, so that when the deformable rod 3 and the force transmission rod 7 are subjected to the same tensile force, the deformation degree of the deformable rod 3 is much greater than the deformation degree of the force transmission rod 7, and the deformation of the deformable rod 3 can be synchronized with the deformation of the cable, and the tensile force shared by the deformable rod 3 can be ignored. In addition, the elastic modulus of the deformable rod 3 is smaller than the elastic modulus of the force transmission rod 7, specifically, it is much smaller than the elastic module of the force transmission rod 7, so that the tensile stiffness of the force transmission rod 7 is much greater than the tensile stiffness of the deformable rod 3. Therefore, when the cable is deformed, only the deformable rod 3 is deformed, and the force transmission rod 7 is not deformed.

[0036] The transmission layer includes a 4G / 5G signal transmitter 20 and a cloud 30. The strain collector is connected to the cloud 30 via the 4G / 5G signal transmitter 20. The strain collector is used to collect strain signals detected by the strain gauge 5 and the temperature compensation strain gauge 6, and convert the electrical signal collected by the strain gauge 5 into a digital signal, and transmit the digital signal to the cloud 30 via the 4G / 5G signal transmitter 20. The display layer includes a terminal device 40. The terminal device 40 is wirelessly connected to the cloud 30, specifically in a wireless connection mode, so as to receive data from the cloud 30 in real time through the Internet, and set the relevant parameters of the cable to be tested on the terminal device 40. The parameters are combined with the data transmitted from the cloud 30 to obtain the cable force increment of the cable to be tested. Preferably, the terminal device 40 is a computer, a mobile phone or a tablet.

[0037] In the present invention, the measuring principle of the cable force increment to be measured is as follows:

[0038] The upper clamping ring 1 and the lower clamping ring 2 of the cable force tester 10 are clamped with the cable force to be measured. Since the tensile stiffness of the force transmission rod 7 is much greater than that of the deformation rod 3, when the cable is deformed, only the deformation rod 3 is deformed. Let the cable force increment be ΔF, then the following relationship is obtained:

[0039] ΔF=EAε c (1)

[0040] Where EA is the tensile stiffness of the cable, ε c is the cable strain.

[0041] At the same time, the strain ε of the deformed rod 3 d and the cable strain ε c The following relationship exists:

[0042]

[0043] Where, L d is the length of the deformed rod 3, L c is the distance between the upper clamping ring 1 and the lower clamping ring 2.

[0044] The deformation rod 3 strain ε caused by temperature change T for:

[0045]

[0046] In the formula, ε a is the strain value of the temperature compensation strain gauge 6, L T is the length of the force transmission rod 7.

[0047] Combining the deformation caused by tension and the deformation caused by temperature change, the following deformation bar 3 strain ε is obtained: d :

[0048]

[0049] In the formula, ε i is the strain value of the i-th strain gauge 5.

[0050] It can be seen from formula (2) that due to L d Much smaller than L c Therefore, the strain on the deformable rod 3 will be much greater than the strain on the cable, thereby achieving strain amplification, thereby greatly improving the test accuracy; at the same time, the present invention can achieve the accuracy of the cable force increment test at different temperatures by installing a strain compensation sheet on the force transmission rod 7.

[0051] Based on the above principle, it can be known that after the cable tension tester 10 clamps the cable, the strain value ε measured by the strain gauge 5 is i , the strain value ε of the temperature compensation strain gauge 6 is obtained by measuring the temperature compensation strain gauge 6a , combining all the strain values ​​and substituting them into equation (4), we can get the strain ε of the deformed rod 3 d , when the tensile stiffness of the cable to be tested is known, the calculated strain ε of the deformed rod 3 is d Substituting into equation (2), we get the cable strain ε c , the cable strain ε c Substituting into equation (1) can obtain the cable force increment ΔF. Therefore, the measuring device provided by the present invention can be used to measure the cable force increment of a bridge cable, and the measurement is simple and convenient, and the use is convenient.

[0052] Based on the above measurement principle and measurement device, the present invention also provides a method for accurately measuring the increment of bridge cable force. The method uses the above-mentioned device for accurately measuring the increment of bridge cable force to perform measurement, and comprises the following steps:

[0053] (1) Calibration of the cable force tester 10;

[0054] (2) Installing a cable force tester 10 on the cable to be tested;

[0055] (3) Instrument connection, wherein all strain gauges 5 and temperature compensation strain gauges 6 of the cable force tester 10 are connected to the strain collector, the strain collector is connected to the cloud 30 via the 4G / 5G signal transmitter 20 of the transmission layer, and the terminal device 40 of the display layer is wirelessly connected to the cloud 30;

[0056] (4) Setting parameters related to the cable to be tested, specifically setting parameters of the cable to be tested on the terminal device 40, the parameters mainly being the elastic modulus E and the cross-sectional area A of the cable to be tested;

[0057] (5) Collection of cable force increments.

[0058] Preferably, in step (1), when the elastic modulus E and the cross-sectional area A of the cable to be tested are unknown, the range of the cable force tester 10 is calibrated by experiment before the cable is installed. The specific steps are as follows:

[0059] 1) Select a cable of the same model as the cable to be tested;

[0060] 2) Installing a cable force tester 10 in the middle of the selected cable;

[0061] 3) Install both ends of the selected cable on the MTS universal testing machine;

[0062] 4) Apply different levels of load to the MTS universal testing machine and measure the strain data on the cable force tester 10 at the same time;

[0063] 5) The tensile stiffness EA of the cable can be calibrated by the following formula:

[0064]

[0065] Where ΔF is the cable force increment, L d is the length of the deformed rod 3, L c is the distance between the upper clamping ring 1 and the lower clamping ring 2, ε i is the strain value of the i-th strain gauge 5, ε a is the strain value of the temperature compensation strain gauge 6, L T is the length of the force transmission rod 7.

[0066] The calculation formula for the bending stiffness of the cable is deduced from the above formulas (1)-(4), and the test calibration is a calibration method selected when direct calibration is not satisfied. That is, in actual testing, the E and A of the cable to be tested may not necessarily be accurate.

[0067] In addition, in the above step 5), when calculating the tensile stiffness EA of the cable, the average value is adopted.

[0068] The above description is a detailed description of the preferred feasible embodiments of the present invention, but the embodiments are not intended to limit the scope of the patent application of the present invention. All equivalent changes or modified changes completed under the technical spirit suggested by the present invention should fall within the patent scope covered by the present invention.

Claims

1. A method for accurately measuring the incremental force of bridge cables, characterized in that: The measuring method adopts a bridge cable force increment precise measuring device for measuring, the bridge cable force increment precise measuring device comprises a cable force tester, a transmission layer and a display layer; the cable force tester comprises an upper clamping ring, a lower clamping ring, four connecting rods, four strain gauges, a temperature compensation strain gauge, and a strain collector, 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 cable to pass through, the aperture of the clamping through hole is slightly smaller than the cable diameter, the upper clamping ring and the lower clamping ring are connected by four connecting rods, and the four connecting rods are arranged at intervals The connecting rods are arranged in a circumferential direction around 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, and 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 a terminal device, and the terminal device is wirelessly connected to the cloud; The measuring method comprises the following steps: (1) Calibration of the cable force tester: When the elastic modulus E and cross-sectional area A of the cable to be tested are unknown, the range of the cable force tester is calibrated by test. The calibration is done before the cable is installed. The specific steps are as follows: 1) Select a cable of the same model as the cable to be tested; 2) Install a cable force tester in the middle of the selected cable; 3) Install both ends of the selected cable on the MTS universal testing machine; 4) Apply different levels of load to the MTS universal testing machine and measure the strain data on the cable force tester at the same time; 5) The tensile stiffness EA of the cable can be calibrated by the following formula: Where ΔF is the cable force increment, L d is the length of the deformed rod, L c is the distance between the upper clamping ring and the lower clamping ring, ε i is the strain value of the ith strain gauge, ε a is the strain value of the temperature compensation strain gauge, L T is the length of the dowel rod; (2) Install a cable force tester on the cable to be tested; (3) Instrument connection, where all strain gauges and temperature compensation strain gauges of the cable force tester are connected to the strain acquisition instrument, which is connected to the cloud via the 4G / 5G signal transmitter of the transmission layer, and the terminal equipment of the display layer is wirelessly connected to the cloud; (4) Setting parameters related to the cable to be tested, specifically setting the parameters of the cable to be tested on the terminal device, the parameters mainly including the elastic modulus E and the cross-sectional area A of the cable to be tested; (5) Collection of cable force increments.

2. The method for accurately measuring the increment of bridge cable force according to claim 1, characterized in that: The upper clamping ring and the lower clamping ring have the same structure. The upper clamping ring is in the shape of a circular ring and is divided into two semicircular rings. Ear plates are welded at both ends of each semicircular ring in the arc length direction. A bolt hole is opened on each ear plate. The two semicircular rings are connected into a circular ring by inserting high-strength bolts through the bolt holes. The inner ring of the circular ring is the clamping through hole.

3. The method for accurately measuring the increment of bridge cable force according to claim 1, characterized in that: The hole wall of the clamping through hole is engraved with a thread structure.

4. The method for accurately measuring the increment of bridge cable force according to claim 1, characterized in that: All the connecting rods have the same length, all the force transmission rods have the same material and size, all the force transmission rods are made of metal, and the cross-sections thereof in the vertical length direction are circular structures.

5. The method for accurately measuring the increment of bridge cable force according to claim 1, characterized in that: All the deformable rods are made of the same material and have the same size. All the deformable rods are made of metal, and their cross-section in the vertical length direction is a rectangular structure. The cross-section size is smaller than the cross-section size of the cable and the cross-section size of the force transmission rod. The elastic modulus of the deformable rod is smaller than the elastic modulus of the force transmission rod.

6. The method for accurately measuring the increment of bridge cable force according to claim 1, characterized in that: The terminal device is a computer.

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