A device and method for measuring the size of cable force based on anchor cup strain

Abstract

The application relates to a cable force size measuring device and method based on an anchor cup strain, which comprises the following: an anchor base body, one end of which is a U-shaped ear end, and the other end is a round table-shaped anchor cup end; eight resistance strain gauges, four of which are longitudinally arranged on the anchor cup end and used for measuring the axial strain of the anchor cup end, and four of which are transversely arranged on the anchor cup end and used for measuring the circumferential strain of the anchor cup end, the four longitudinally arranged resistance strain gauges are connected in series to form a first branch and a fourth branch, the four transversely arranged resistance strain gauges are connected in series to form a second branch and a third branch, and the four branches are connected in parallel to form a Wheatstone full-bridge circuit; and a signal acquisition and transmission device connected to the Wheatstone full-bridge circuit through wires. The application can realize real-time and accurate measurement of the cable force size during the service of the cable, and can be used for the construction and service stage of the cable net structure in a building structure and the bridge cable.

Description

Technical Field

[0001] This invention relates to the field of cable force monitoring technology, specifically to a device and method for measuring cable force based on the strain of the anchor cup. Background Technology

[0002] As engineering systems such as large bridges, cable-net structures, and super high-rise buildings continue to develop towards larger spans and more complex forms, the stress state of cables, as the main load-bearing components, has a decisive impact on the overall safety and service performance of the structure. Accurately grasping the cable stress level is not only crucial for the reliability of design calculations and construction tension control, but also a key link in long-term structural health monitoring and safety assessment. Abnormal fluctuations in cable stress can lead to reduced structural stiffness, amplified dynamic response, and even serious problems such as instability. Therefore, achieving high-precision, stable, and real-time monitoring of cable stress has significant engineering value for ensuring the safe operation of engineering structures.

[0003] Currently, commonly used methods for testing cable force in engineering practice include vibration method, displacement method, strain method, hydraulic pressure gauge method, pressure sensor method, and magnetic flux method. The vibration method calculates cable force by inversely using the cable's natural frequency. While it has advantages such as being non-contact and having high measurement sensitivity, it is easily affected by temperature changes, boundary constraints, and multi-mode coupling in practical applications, leading to deviations in the calculation results. The displacement method obtains cable force information by observing cable elongation, but its reliability is difficult to maintain in long-term monitoring due to limitations in the layout of on-site reference points and environmental stability. The hydraulic pressure gauge method and pressure sensor method are mainly used in the tensioning construction stage, estimating cable force by recording changes in internal hydraulic pressure or force. Although simple to operate, they are not suitable for continuous monitoring during the structural service life. The magnetic flux method calculates cable force based on the change in magnetic permeability after the cable is stressed. It has the advantage of being non-contact, but it is easily affected by the material's magnetic properties, temperature changes, and electromagnetic noise, limiting its applicability. In contrast, the classical strain method directly obtains the axial strain of the cable by attaching or embedding strain gauges on the surface of the cable, thereby calculating the cable force. It has the advantages of simple structure, controllable cost, and rapid response, and is a more common measurement method in engineering applications.

[0004] Nevertheless, cable stress testing based on the classical strain gauge method is inevitably subject to interference from various factors in practical engineering monitoring. The complex service environment of cables, including temperature fluctuations, material relaxation, variations in strain gauge installation quality, and noise during signal acquisition, can all affect measurement accuracy. Furthermore, traditional strain monitoring systems often experience calibration difficulties, signal drift, and data instability during long-term operation, limiting their performance in continuous and reliable monitoring. Therefore, while maintaining the advantages of the classical strain gauge method's simple structure and ease of implementation, further improving its measurement accuracy, environmental adaptability, and system reliability has become a key focus of current cable stress monitoring technology research and engineering practice. Summary of the Invention

[0005] In view of the shortcomings of the prior art, the main objective of the present invention is to provide a device and method for measuring the magnitude of cable force based on the strain of the anchor cup, so as to realize the real-time and accurate calculation of the magnitude of cable force when the cable is under stress.

[0006] The technical solution of the present invention is as follows:

[0007] This invention proposes a device for measuring the magnitude of cable force based on the strain of the anchor cup, comprising:

[0008] The anchor body has a U-shaped lug end for connecting to the main structure and a frustum-shaped anchor cup end for fixing to the cable anchor head.

[0009] Eight resistance strain gauges are provided, of which four resistance strain gauges are arranged longitudinally at the end of the anchor cup to measure the axial strain of the anchor cup end, and four resistance strain gauges are arranged laterally at the end of the anchor cup to measure the circumferential strain of the anchor cup end. The four longitudinally arranged resistance strain gauges are connected in series in pairs to form the first branch and the fourth branch, and the four laterally arranged resistance strain gauges are connected in series in pairs to form the second branch and the third branch. The four branches are connected in parallel to form a Wheatstone full-bridge circuit.

[0010] The signal acquisition and transmission device is connected to the Wheatstone full-bridge circuit via wires to acquire the bridge output voltage of the Wheatstone full-bridge circuit and provide the bridge excitation voltage.

[0011] In some embodiments, four longitudinally arranged resistive strain gauges are uniformly disposed on the outer circumferential surface of the anchor cup end along the direction of the anchor cup end generatrix, and four transversely arranged resistive strain gauges are uniformly disposed on the outer circumferential surface of the anchor cup end along the direction perpendicular to the anchor cup end generatrix.

[0012] In some embodiments, four longitudinally arranged resistive strain gauges are distributed at 90° intervals on the outer circumferential surface of the anchor cup end, and four transversely arranged resistive strain gauges are distributed at 90° intervals on the outer circumferential surface of the anchor cup end.

[0013] In some embodiments, the cable force measuring device further includes an annular sleeve, which is fitted onto the end of the anchor cup and fixedly connected to the end of the anchor cup, for protecting the resistive strain gauge and its connecting wires.

[0014] In some embodiments, the cable force measuring device further includes an output plug, which is mounted on the annular sleeve and connected to the Wheatstone full-bridge circuit via a wire for external connection to the signal acquisition and transmission equipment.

[0015] The present invention also proposes a method for determining the magnitude of cable force based on the above-mentioned measuring device, comprising the following steps:

[0016] The measuring device is installed on the cable to be tested; wherein, the two resistive strain gauges in the first branch are resistive strain gauge R1 and resistive strain gauge R1', the two resistive strain gauges in the second branch are resistive strain gauge R2 and resistive strain gauge R2', the two resistive strain gauges in the third branch are resistive strain gauge R3 and resistive strain gauge R3', and the two resistive strain gauges in the fourth branch are resistive strain gauge R4 and resistive strain gauge R4', and the resistance of each resistive strain gauge is R;

[0017] The signal acquisition and transmission device provides the bridge excitation voltage U to the Wheatstone full-bridge circuit. i And collect the bridge output voltage U0 of the Wheatstone full-bridge circuit under the action of cable force;

[0018] Based on the relationship between the resistance and strain of any resistance strain gauge in the four branches, the relationship between the strain of each resistance strain gauge in the four branches and the cable force F, as well as the bridge output voltage U0 and the bridge excitation voltage U... i The cable force F is determined by the relationship between the resistance of the eight resistance strain gauges in the four branches.

[0019] In some embodiments, the relationship between the resistance and strain of any of the four branches of the resistive strain gauge satisfies the following equation:

[0020]

[0021] In the formula, K s Let R represent the strain sensitivity coefficient of any resistance strain gauge in the four branches, and let ΔR represent the resistance of any resistance strain gauge in the four branches. iε represents the magnitude of the change in resistance of any resistive strain gauge in the four branches caused by strain. i This indicates the strain at any position of the resistance strain gauge in the four branches.

[0022] In some embodiments, the relationship between the strain of each resistance strain gauge in the four branches and the cable force F satisfies the following Equation 2:

[0023] ;

[0024] ;

[0025] In the formula, ε1 and ε1' represent the strain at positions of resistance strain gauges R1 and R1' in the first branch, respectively; ε2 and ε2' represent the strain at positions of resistance strain gauges R2 and R2' in the second branch, respectively; ε3 and ε3' represent the strain at positions of resistance strain gauges R3 and R3' in the third branch, respectively; and ε4 and ε4' represent the strain at positions of resistance strain gauges R4 and R4' in the fourth branch, respectively. This represents the strain measured by longitudinally arranged resistance strain gauges. This represents the strain measured by the horizontally arranged resistance strain gauges. α represents the spurious strain caused by temperature, F represents the cable force, E represents the elastic modulus of the anchor cup end material, r1 represents the radius of the circular cross section on the upper surface of the frustum at the anchor cup end, r2 represents the radius of the circular cross section on the lower surface of the frustum at the anchor cup end, α represents the angle between the generatrix of the frustum at the anchor cup end and the central axis, and μ represents the Poisson's ratio of the anchor cup end material.

[0026] In some embodiments, the bridge output voltage U0 and the bridge excitation voltage U i The relationship between the resistance of the eight resistance strain gauges in the four branches and the resistance of the strain gauges satisfies the following relationship (Equation 3):

[0027]

[0028] In the formula, This indicates the magnitude of the change in resistance of the resistive strain gauge R1 caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R1' caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R2 caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R2' caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R3 caused by strain. This indicates the magnitude of the change in resistance of the resistance strain gauge R3' caused by strain. This indicates the magnitude of the change in resistance of the resistance strain gauge R4 caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R4' caused by strain.

[0029] In some embodiments, determining the cable force involves substituting equation one and equation two into equation three:

[0030]

[0031] In the formula, The above formula can be simplified to:

[0032]

[0033] The cable force F is:

[0034] .

[0035] The advantages of this invention compared to existing technologies are as follows: This invention proposes a cable force measurement device based on anchor cup strain. This device, through optimized anchor structure, strain gauge layout, and bridge circuit design, combined with rigorous theoretical formula derivation, achieves high-precision, interference-resistant, and long-term stable cable force monitoring, providing a reliable technical means for the safety assessment of bridges, buildings, and other engineering structures. Specifically, it has at least the following practical effects:

[0036] In this invention, eight resistance strain gauges are firmly fixed to the side surface of the anchor cup by welding or bonding. The anchor cup is directly connected to the cable. The arrangement of the strain gauges takes into account both the lateral strain and circumferential strain of the anchor cup, which can monitor the cable force in real time and accurately, thereby improving the overall structural safety of the cable during service.

[0037] In this invention, eight resistance strain gauges are permanently installed on the anchor cup end. During the construction phase and the service life of the cable, the cable force is monitored in real time based on the constructed Wheatstone full-bridge circuit, which greatly reduces labor costs.

[0038] In this invention, the geometric parameters of the anchor cup end are adjustable, making it suitable for cables of different diameters; the strain gauge layout is flexible and can be extended to other structural stress monitoring scenarios.

[0039] In this invention, the output voltage and cable force are linearly related through the Wheatstone full-bridge circuit design, simplifying the calculation process and improving real-time performance.

[0040] In this invention, four longitudinally arranged resistive strain gauges are connected in series in pairs to form the first and fourth branches, while four laterally arranged resistive strain gauges are connected in series in pairs to form the second and third branches. When two strain gauges in the same branch are connected in series, under the same cable force, the resistance changes of the two strain gauges will be superimposed, increasing the total resistance change of that branch. In the bridge circuit, this increased resistance change leads to a more significant change in the bridge output voltage, thereby improving the bridge's sensitivity to cable force changes and enabling more precise detection of minute changes in cable force. This provides more accurate data support for structural health monitoring and safety assessment.

[0041] In this invention, annular sleeves are placed on the outside of eight resistance strain gauges. The annular sleeves can effectively protect the resistance strain gauges and their connecting lines, and are connected to signal acquisition and transmission equipment through the output plug, ensuring the long-term stable operation of the resistance strain gauges and resisting external environmental interference.

[0042] In this invention, the cable force measuring device does not cause any cross-sectional weakening or structural damage to the original structure of the cable anchor, thus ensuring the integrity of the mechanical properties of the cable anchor.

[0043] It should be understood that the description in the Summary of the Invention is not intended to limit the key or essential features of the embodiments of the present invention, nor is it intended to restrict the scope of the invention. Other features of the invention will become readily apparent from the following description. Furthermore, implementation of any embodiment of the present invention does not imply the simultaneous possession or achievement of multiple or all of the aforementioned beneficial effects. Attached Figure Description

[0044] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings in the following description are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0045] The structures, proportions, sizes, etc. illustrated in this specification are only for the purpose of assisting those skilled in the art in understanding and reading the content disclosed herein, and are not intended to limit the conditions under which the present invention can be implemented. Therefore, they have no substantial technical significance. Any modifications to the structure, changes in the proportions, or adjustments to the size, without affecting the effects and objectives that the present invention can produce, should still fall within the scope of the technical content disclosed in the present invention.

[0046] Figure 1 This is a schematic diagram of the cable force measurement device based on anchor cup strain according to some embodiments of the present invention;

[0047] Figure 2 This is a schematic diagram of the arrangement of eight resistance strain gauges in some embodiments of the present invention;

[0048] Figure 3 This is a schematic diagram of a Wheatstone full-bridge circuit formed by connecting eight resistive strain gauges according to some embodiments of the present invention.

[0049] Figure 4 This is a schematic diagram illustrating the cable force calculation principle of the cable force measuring device based on anchor cup strain in some embodiments of the present invention;

[0050] Figure 5 This is a schematic diagram of the connection of a cable force measuring device based on anchor cup strain according to some embodiments of the present invention.

[0051] Marked in the image:

[0052] 1-Anchor base; 101-Ear end; 1011-Ear hole; 102-Anchor cup end;

[0053] 2-Resistance strain gauge;

[0054] 2a1 - First branch; 2a1R1 - Resistance strain gauge R1; 2a1R1' - Resistance strain gauge R1';

[0055] 2a2 - Second branch; 2a2R2 - Resistance strain gauge R2; 2a2R2' - Resistance strain gauge R2';

[0056] 2a3 - Third branch; 2a3R3 - Resistance strain gauge R3; 2a3R3' - Resistance strain gauge R3';

[0057] 2a4 - Fourth branch; 2a4R4 - Resistance strain gauge R4; 2a4R4' - Resistance strain gauge R4';

[0058] 3-Annular sleeve;

[0059] 4- Output plug;

[0060] 5-Earplate;

[0061] 6-Pin;

[0062] 7- Cable anchor head;

[0063] 8-Wire.

[0064] The same or corresponding marks in the diagram indicate the same or corresponding parts. Detailed Implementation

[0065] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Here, the illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0066] In this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," "linking," and "fixing," etc., should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0067] It should be understood that the terms "comprising / including," "consisting of," or any other variations are intended to cover non-exclusive inclusion, such that a product, apparatus, process, or method that comprises a list of elements includes not only those elements but may also include, where necessary, other elements not expressly listed, or elements inherent to such a product, apparatus, process, or method. Without further limitation, an element defined by the phrases "comprising / including," "consisting of," does not exclude the presence of additional identical elements in the product, apparatus, process, or method that includes said element.

[0068] It should also be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device, component or structure referred to must have a specific orientation, be constructed or operated in a specific orientation, and should not be construed as a limitation of the present invention.

[0069] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature. In the description of this invention, "a plurality of" means two or more, unless otherwise explicitly specified.

[0070] The implementation of the present invention will be described in detail below with reference to preferred embodiments.

[0071] See Figures 1 to 5This invention provides a cable force monitoring device based on anchor cup strain, comprising an anchor body 1, eight resistance strain gauges 2, and a signal acquisition and transmission device. One end of the anchor body 1 is a U-shaped lug end 101 for connection to the main structure, and the other end is a frustum-shaped anchor cup end 102 for fixed connection to the cable anchor head 7. The eight resistance strain gauges 2 are evenly distributed on the anchor cup end 102. The signal acquisition and transmission device is connected to the eight resistance strain gauges 2 via wires.

[0072] The signal acquisition and transmission device is connected to eight resistance strain gauges 2 via wires 8. One of its main functions is to acquire the strain signals sensed by the resistance strain gauges 2 in real time. When the resistance strain gauge 2 is subjected to strain at the anchor cup end 102, its resistance value will change accordingly. The signal acquisition and transmission device can accurately convert this resistance change into an electrical signal and acquire it, providing basic data for subsequent data processing and analysis.

[0073] In this embodiment, the anchor base 1 serves as the load-bearing skeleton of the entire device, and its U-shaped lug end 101 is adapted to connect with the main structure through the lug plate 5. The U-shaped lug end 101 is made of high-strength steel to ensure good rigidity and stability under long-term stress.

[0074] Specifically, ear holes 1011 are provided on both sides of the U-shaped insert end 101. One end of the ear plate 5 is placed in the opening space of the U-shaped insert end 101, which provides a precise positioning and accommodation space for the ear plate 5. The ear plate 5 has the same hole at the corresponding position of the ear hole 1011. The ear plate 5 and the U-shaped insert end 101 are connected by a pin 6 passing through the ear hole 1011 and the corresponding hole, forming a rotating connection that can transmit axial tensile force.

[0075] The other end of the ear plate 5 is fixedly connected to the main structure (not shown in the figure). This connection method ensures that the cable has a reasonable degree of rotational freedom when under stress. When the cable is subjected to dynamic loads such as wind loads and seismic loads, the ear plate 5 can rotate around the pin 6 within a certain range to release some stress, avoid stress concentration or damage at the connection point due to excessive constraint, and at the same time effectively transfer the tension of the cable to the main structure.

[0076] As is easy to understand, the main structure includes, but is not limited to, bridge anchorage systems, cable net structure nodes, or truss supports for high-rise buildings.

[0077] The frustum-shaped anchor cup end 102 of the anchorage base 1 is firmly connected to the cable anchor head 7 through extrusion and other methods. During the extrusion process, specialized extrusion equipment and process parameters are used to generate sufficient friction and mechanical interlocking force between the steel wire of the cable anchor head 7 and the inner wall of the anchor cup end 102, thereby reliably transferring all the axial tension of the cable to the anchorage base 1. The cable force acts directly through the anchor cup end 102, resulting in a direct and stable relationship between the strain of the anchor cup end 102 and the cable force, laying the foundation for accurate measurement.

[0078] In this embodiment, the eight resistance strain gauges 2 include four longitudinally arranged resistance strain gauges 2 and four transversely arranged resistance strain gauges 2. The four longitudinally arranged resistance strain gauges 2 are uniformly arranged along the generatrix direction (i.e., axial direction) of the anchor cup end 102, and are used to measure the axial strain generated by the anchor cup end 102 under the action of cable force. The four transversely arranged resistance strain gauges 2 are uniformly arranged along a direction perpendicular to the generatrix of the anchor cup end 102 (i.e., circumferential direction), and are used to measure the circumferential strain generated by the anchor cup end 102 under the action of cable force.

[0079] In this embodiment, the resistance strain gauge 2 can be firmly fixed to the outer circumferential surface of the anchor cup end 102 by welding or bonding, or a groove can be made on the outer circumferential surface of the anchor cup end 102 to embed the resistance strain gauge 2 into the groove for fixation. Of course, the arrangement method is not limited to this, and other equivalent methods that can achieve stable fixation of the resistance strain gauge 2 can also be used.

[0080] See Figure 3 The four longitudinally arranged resistance strain gauges 2 include resistance strain gauges R1 2a1R1, R1' 2a1R1', R4 2a4R4, and R4' 2a4R4'. The four transversely arranged resistance strain gauges 2 include resistance strain gauges R2 2a2R2, R2' 2a2R2', R3 2a3R3, and R3' 2a3R3'.

[0081] Among them, the resistance strain gauges R1 2a1R1, R1' 2a1R1', R4 2a4R4 and R4' 2a4R4' are arranged in four quadrants, and the resistance strain gauges R2 2a2R2, R2' 2a2R2', R3 2a3R3 and R3' 2a3R3' are arranged in their corresponding positions to form an eight-point strain measurement system.

[0082] More specifically, resistance strain gauges R1 2a1R1 and R1' 2a1R1' are connected in series to form the first branch 2a1; resistance strain gauges R4 2a4R4 and R4' 2a4R4' are connected in series to form the fourth branch 2a4; resistance strain gauges R2 2a2R2 and R2' 2a2R2' are connected in series to form the second branch 2a2; and resistance strain gauges R3 2a3R3 and R3' 2a3R3' are connected in series to form the third branch 2a3. The first branch 2a1, the second branch 2a2, the third branch 2a3, and the fourth branch 2a4 are connected in parallel to form a Wheatstone full-bridge circuit (a full-bridge Wheatstone bridge). The signal acquisition and transmission equipment is connected to this Wheatstone full-bridge circuit via wires to acquire the bridge output voltage of the Wheatstone full-bridge circuit and provide the bridge excitation voltage.

[0083] In this invention, resistive strain gauges are connected in pairs in series to form a Wheatstone bridge circuit, which can improve the sensitivity of the bridge to a certain extent. According to the working principle of the Wheatstone bridge, the output voltage of the bridge is proportional to the change in resistance of the strain gauges. When two strain gauges in the same branch are connected in series, under the same cable force, the changes in resistance of the two strain gauges will be superimposed, increasing the total change in resistance of that branch. In the bridge circuit, this increased resistance change leads to a more significant change in the bridge output voltage, thereby improving the bridge's sensitivity to changes in cable force. This allows for more precise detection of minute changes in cable force, providing more accurate data support for structural health monitoring and safety assessment.

[0084] In this invention, strain gauge branches arranged longitudinally and laterally are connected in parallel to form a Wheatstone bridge circuit, which can simultaneously collect strain information from both longitudinal and lateral directions. The output signal of the bridge circuit comprehensively reflects the strain changes in these two directions. By analyzing and processing the output signal, the axial and circumferential strain values ​​at the anchor cup end under cable force can be obtained, thus providing more comprehensive data support for evaluating the mechanical performance and safety of the structure. For example, in bridge cable force monitoring, understanding the multi-directional strain at the anchor cup end helps to determine whether the cable force distribution is uniform and whether there are potential problems such as excessive local stress.

[0085] In this invention, the circuit design has significant advantages: on the one hand, when the ambient temperature changes, the resistance of the eight resistive strain gauges will increase or decrease synchronously. Through the differential output principle of the Wheatstone full-bridge circuit, the false strain signals caused by temperature changes can be effectively canceled, greatly improving the system's environmental adaptability and long-term stability; on the other hand, the output voltage of the circuit has a good linear relationship with the cable force, which simplifies the subsequent data processing and calculation process and is conducive to realizing fast and real-time cable force monitoring.

[0086] Preferably, four longitudinally arranged resistance strain gauges 2 are distributed at 90° intervals on the outer circumferential surface of the anchor cup end 102, and four transversely arranged resistance strain gauges 2 are distributed at 90° intervals on the outer circumferential surface of the anchor cup end 102.

[0087] Longitudinal and transverse resistance strain gauges 2 are alternately distributed at 90° intervals on the outer circumference of the anchor cup end 102, forming a full-circumferential, multi-dimensional strain sensing network. By simultaneously acquiring axial and circumferential strain information, the stress state of the anchor cup end 102 can be more comprehensively reflected, which helps to improve the overall accuracy and robustness of the measurement.

[0088] See Figure 2 Resistance strain gauges R1 2a1R1, R1' 2a1R1', R4 2a4R4, and R4' 2a4R4' are located at four positions (0°, 90°, 180°, 270°) on the frustum-shaped side surface of the anchor cup end 102, respectively. Their measurement direction is along the generatrix of the frustum of the anchor cup end 102, and they are used to measure the axial strain of the anchor cup end 102. Resistance strain gauges R2 2a2R2, R2' 2a2R2', R3 2a3R3, and R3' 2a3R3' are located at four positions (0°, 90°, 180°, 270°) on the frustum-shaped side surface of the anchor cup end 102, respectively. Their measurement direction is perpendicular to the generatrix of the frustum of the anchor cup end 102, and they are used to measure the circumferential strain of the anchor cup end 102.

[0089] Preferably, the longitudinally arranged resistance strain gauges R1 2a1R1 and the transversely arranged resistance strain gauges R2 2a2R2 are arranged at the same angle, and the transversely arranged resistance strain gauges R2 2a2R2 are positioned directly below the longitudinally arranged resistance strain gauges R1 2a1R1; the longitudinally arranged resistance strain gauges R1' 2a1R1' and the transversely arranged resistance strain gauges R2' 2a2R2' are arranged at the same angle, and the transversely arranged resistance strain gauges R2' 2a2R2' are positioned directly below the longitudinally arranged resistance strain gauges R1' 2a1R1'; the longitudinally arranged resistance strain gauges R4 2a4R4 and the transversely arranged resistance strain gauges R3 2a3R3 are arranged at the same angle, and the transversely arranged resistance strain gauges R3 2a3R3 are positioned above the longitudinally arranged resistance strain gauges R4 Directly below 2a4R4; the longitudinally arranged resistance strain gauges R4' 2a4R4' and the transversely arranged resistance strain gauges R3' 2a3R3' are arranged at the same angle, and the transversely arranged resistance strain gauges R3' 2a3R3' are arranged directly below the longitudinally arranged resistance strain gauges R4' 2a4R4'.

[0090] In a Wheatstone bridge, resistance strain gauges 2 in the same direction can be connected in series; however, resistance strain gauges 2 in different directions (longitudinal and transverse) cannot be connected in series, but can be connected in parallel. Since the anchor cup end 102 is a geometrically symmetrical body about an arbitrary axis, when arranging the circuit, resistance strain gauges 2 in the same direction on the same axis are selected for series connection. This better adapts to the symmetrical characteristics of the anchor cup end 102, ensuring stable circuit performance and accurate measurement data.

[0091] Continue reading Figure 1 The cable force measuring device also includes an annular sleeve 3, which is fitted onto the outside of the anchor cup end 102 and fixedly connected to it. The annular sleeve 3 has a reserved space inside to accommodate the resistance strain gauge 2 and the wire 8, which are fixed by welding or bolts to protect the strain gauge from external forces, humid environments, concrete covering, or temperature effects, thus improving the reliability of long-term monitoring.

[0092] More precisely, the main function of the annular sleeve 3 is to protect the eight resistance strain gauges 2 and the connecting wires 8 attached to the anchor cup end 102 from damage caused by external environmental factors such as on-site construction, rainwater erosion, dust accumulation, and accidental collisions. This ensures the long-term reliable operation of the Wheatstone full-bridge circuit and resists external environmental interference. While achieving effective protection, this design does not weaken the original structure of the anchor base 1 in any way, ensuring the integrity of the mechanical properties of the cable anchoring system.

[0093] Continue reading Figure 1 The cable force measuring device also includes an output plug 4, which is mounted on the annular sleeve 3 and connected to the Wheatstone full-bridge circuit via internal wires 8. The output plug 4 serves as the external interface of the device, facilitating convenient and quick connection to external signal acquisition and transmission equipment, enabling remote and real-time transmission of monitoring data. This design results in neat and orderly on-site wiring and makes the maintenance and replacement of signal acquisition equipment extremely convenient.

[0094] In some embodiments, to ensure the bonding quality of the resistance strain gauge 2, the surface of the anchor cup end 102 needs to be treated as follows:

[0095] 1. Use a grinding wheel to polish the area where the resistance strain gauge is bonded until it has a metallic luster;

[0096] 2. Clean surface oil stains with anhydrous ethanol or acetone;

[0097] 3. Polish further with fine sandpaper to make the surface smooth.

[0098] Attachment of resistance strain gauge 2:

[0099] 1. Attach longitudinal resistance strain gauges at the design orientations of 0°, 90°, 180°, and 270°;

[0100] 2. Attach the transversely arranged resistance strain gauge 2 at the same position as the longitudinally arranged resistance strain gauge 2;

[0101] 3. Use a special adhesive for curing to avoid air bubbles;

[0102] 4. After curing, cover with a waterproof layer.

[0103] After the resistance strain gauge electrode is welded to the wire 8, it is led out through the annular sleeve 3. The weld joint is then potted to improve the waterproof rating. The annular sleeve 3 fits tightly with the anchor cup end 102 and is fixed with bolts or welds to ensure that it will not loosen during long-term service.

[0104] Embodiments of the present invention also provide a method for determining the cable force based on the monitoring device provided in the above embodiments, specifically including the following steps:

[0105] The cable force measuring device is installed on the actual cable to be tested; wherein, the two resistive strain gauges 2 of the first branch 2a1 are resistive strain gauge R1 2a1R1 and resistive strain gauge R1' 2a1R1' respectively, the two resistive strain gauges 2 of the second branch 2a2 are resistive strain gauge R2 2a2R2 and resistive strain gauge R2' 2a2R2' respectively, the two resistive strain gauges 2 of the third branch 2a3 are resistive strain gauge R3 2a3R3 and resistive strain gauge R3' 2a3R3' respectively, and the two resistive strain gauges 2 of the fourth branch 2a4 are resistive strain gauge R4 2a4R4 and resistive strain gauge R4' 2a4R4' respectively, and the resistance of each resistive strain gauge 2 is R;

[0106] The bridge excitation voltage U is provided to the Wheatstone full-bridge circuit through signal acquisition and transmission equipment. i And collect the bridge output voltage U0 of the Wheatstone full-bridge circuit under the action of cable force;

[0107] Based on the relationship between the resistance and strain of any resistance strain gauge in the four branches, the relationship between the strain of each resistance strain gauge in the four branches and the cable force F, as well as the bridge output voltage U0 and the bridge excitation voltage U... i The cable force is determined by the relationship between the resistance of the eight resistance strain gauges in the four branches.

[0108] Furthermore, based on the resistivity-strain effect of metals, that is, the phenomenon where the resistance of a metal wire changes accordingly with its mechanical deformation (tension or compression), the resistance of the metal wire in its free state is:

[0109]

[0110] In the formula, R is the resistance (Ω), ρ is the resistivity (Ω·m), l is the length of the metal wire (m), and S is the cross-sectional area of ​​the metal wire (m²). 2 ).

[0111] When a metal wire stretches due to tension, its resistance changes. Taking the total differential of the above equation:

[0112]

[0113] The relative change in resistance is then:

[0114]

[0115] In the formula, dl / l represents the relative change in the length of the metal wire, which, according to mechanics of materials, is equal to the axial strain of the metal wire ε=dl / l. dS / S represents the relative change in cross-sectional area, since S=πr 2 Therefore, dS / S = 2dr / r, ε r =dr / r is called the radial strain of the metal wire, ε r =-με (μ is the Poisson's ratio of the material), dρ / ρ is the relative change in resistivity.

[0116] Based on the above parameter definitions, the above equation becomes:

[0117]

[0118] make:

[0119]

[0120] In the formula, K s is the strain sensitivity coefficient of the metal wire, which physically represents the relative change in resistance caused by a unit strain.

[0121] Experiments have shown that within the elastic deformation range of the metal wire, dR / R is proportional to the axial strain ε, therefore K s It is a constant, that is:

[0122]

[0123] The formula shows that the axial strain of the metal wire is directly proportional to the relative change in its resistance. When the metal wire is under tension, it produces positive strain and the resistance increases linearly; when it is under compression, it produces negative strain and the resistance decreases linearly.

[0124] Therefore, based on the resistance strain effect of metals, the relationship between the resistance and strain of any resistance strain gauge 2 in the four branches satisfies Equation 1, which is:

[0125]

[0126] In the formula, K s Let R represent the strain sensitivity coefficient of any resistive strain gauge 2 in the four branches, and let ΔR represent the resistance of any resistive strain gauge 2 in the four branches. i ε represents the magnitude of the change in resistance of any resistive strain gauge 2 in the four branches caused by strain. i This indicates the strain at any position of the resistance strain gauge in the four branches.

[0127] Furthermore, according to the principles of mechanics of materials, the relationship between the strain of each resistance strain gauge 2 in the four branches and the cable force F satisfies Equation 2, which is:

[0128] ;

[0129]

[0130] In the formula, ε1 and ε1' represent the strain at positions R1 2a1R1 and R1'2a1R1' in the first branch 2a1, respectively; ε2 and ε2' represent the strain at positions R2 2a2R2 and R2' 2a2R2' in the second branch 2a2, respectively; ε3 and ε3' represent the strain at positions R3 2a3R3 and R3' 2a3R3' in the third branch 2a3, respectively; and ε4 and ε4' represent the strain at positions R4 2a4R4 and R4' 2a4R4' in the fourth branch 2a4, respectively. This represents the strain measured by the longitudinally arranged resistance strain gauge 2. This represents the strain measured by the laterally arranged resistance strain gauge 2. α represents the spurious strain caused by temperature, F represents the cable force, E represents the elastic modulus of the material of anchor cup end 102, r1 represents the radius of the circular cross section of the upper surface of the frustum of anchor cup end 102, r2 represents the radius of the circular cross section of the lower surface of the frustum of anchor cup end 102, α represents the angle between the generatrix of the frustum of anchor cup end 102 and the central axis, and μ represents the Poisson's ratio of the material of anchor cup end 102.

[0131] Furthermore, according to the Wheatstone bridge principle, the bridge output voltage U0 and the bridge excitation voltage U i The relationship between the resistances of the eight resistive strain gauges 2 in the four branches and the resistances of the strain gauges 2 in the four branches satisfies Equation 3, which is:

[0132]

[0133] In the formula, This indicates the magnitude of the change in resistance of the resistive strain gauge R1 2a1R1 caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R1' 2a1R1' caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R2 2a2R2 caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R2' 2a2R2' caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R3 2a3R3 caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R3' 2a3R3' caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R4 2a4R4 caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R4' 2a4R4' caused by strain.

[0134] Furthermore, determining the cable force involves substituting Equations 1 and 2 into Equation 3, including:

[0135]

[0136] In the formula, since Therefore, the above formula can be simplified to:

[0137]

[0138] The cable force F is:

[0139] .

[0140] From the formula for determining the cable force F above, it can be seen that... Let be a calculable constant, and another Then we have:

[0141]

[0142] In actual monitoring, when the bridge output voltage is U0, the cable force is:

[0143]

[0144] Specifically, data can be sent to a data processing center or data processing terminal through signal acquisition and transmission equipment. At the center, specific equipment is used to run the formula to calculate the cable force value in real time. Finally, the results are stored and displayed on a remote monitoring platform for staff to view and analyze.

[0145] The processed signals need to be transmitted to a data processing center or data processing terminal via signal acquisition and transmission equipment. This equipment can use wired transmission (such as Ethernet, fiber optic, etc.) or wireless transmission (such as Wi-Fi, Bluetooth, 4G / 5G, etc.) to transmit the acquired strain data to a designated location in real time and accurately, realizing remote sharing and centralized management of cable stress monitoring data, and facilitating staff to monitor and analyze cable stress status anytime and anywhere.

[0146] The cable force measurement device based on anchor cup strain proposed in this invention achieves high-precision, anti-interference, and long-term stable cable force monitoring by optimizing the anchor structure, strain gauge layout, and bridge circuit design, combined with rigorous theoretical formula derivation. This provides a reliable technical means for the safety assessment of engineering structures such as bridges and buildings.

[0147] It will be readily understood by those skilled in the art that, without conflict, the above-mentioned preferred solutions can be freely combined and superimposed.

[0148] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A device for measuring the magnitude of cable force based on the strain of the anchor cup, characterized in that, include: The anchor body has a U-shaped lug end for connecting to the main structure and a frustum-shaped anchor cup end for fixing to the cable anchor head. Eight resistance strain gauges are provided, of which four resistance strain gauges are arranged longitudinally at the end of the anchor cup to measure the axial strain of the anchor cup end, and four resistance strain gauges are arranged laterally at the end of the anchor cup to measure the circumferential strain of the anchor cup end. The four longitudinally arranged resistance strain gauges are connected in series in pairs to form the first branch and the fourth branch, and the four laterally arranged resistance strain gauges are connected in series in pairs to form the second branch and the third branch. The four branches are connected in parallel to form a Wheatstone full-bridge circuit. The signal acquisition and transmission device is connected to the Wheatstone full-bridge circuit via wires to acquire the bridge output voltage of the Wheatstone full-bridge circuit and provide the bridge excitation voltage.

2. The measuring device according to claim 1, characterized in that, The four longitudinally arranged resistive strain gauges are evenly distributed on the outer circumferential surface of the anchor cup end along the direction of the anchor cup end generatrix, and the four transversely arranged resistive strain gauges are evenly distributed on the outer circumferential surface of the anchor cup end along the direction perpendicular to the anchor cup end generatrix.

3. The measuring device according to claim 1, characterized in that, The four longitudinally arranged resistive strain gauges are distributed at 90° intervals on the outer circumferential surface of the anchor cup end, and the four transversely arranged resistive strain gauges are distributed at 90° intervals on the outer circumferential surface of the anchor cup end.

4. The measuring device according to claim 1, characterized in that, The cable force measuring device also includes an annular sleeve, which is fitted onto the end of the anchor cup and fixedly connected to the end of the anchor cup, for the purpose of protecting the resistive strain gauge and its connecting wires.

5. The measuring device according to claim 4, characterized in that, The cable force measuring device also includes an output plug, which is mounted on the annular sleeve and connected to the Wheatstone full-bridge circuit via a wire for external connection to the signal acquisition and transmission equipment.

6. A method for determining the magnitude of cable force based on the measuring device according to any one of claims 1 to 5, characterized in that, Includes the following steps: The measuring device is installed on the cable to be tested; wherein, the two resistive strain gauges in the first branch are resistive strain gauge R1 and resistive strain gauge R1', the two resistive strain gauges in the second branch are resistive strain gauge R2 and resistive strain gauge R2', the two resistive strain gauges in the third branch are resistive strain gauge R3 and resistive strain gauge R3', and the two resistive strain gauges in the fourth branch are resistive strain gauge R4 and resistive strain gauge R4', and the resistance of each resistive strain gauge is R; The signal acquisition and transmission device provides the bridge excitation voltage U to the Wheatstone full-bridge circuit. i And collect the bridge output voltage U0 of the Wheatstone full-bridge circuit under the action of cable force; Based on the relationship between the resistance and strain of any resistance strain gauge in the four branches, the relationship between the strain of each resistance strain gauge in the four branches and the cable force F, as well as the bridge output voltage U0 and the bridge excitation voltage U... i The cable force F is determined by the relationship between the resistance of the eight resistance strain gauges in the four branches.

7. The determination method according to claim 6, characterized in that, The relationship between the resistance and strain of any of the four resistance strain gauges satisfies the following equation: In the formula, K s Let R represent the strain sensitivity coefficient of any resistance strain gauge in the four branches, and let R represent the resistance of any resistance strain gauge in the four branches. ΔR i ε represents the magnitude of the change in resistance of any of the four strain gauges caused by strain. i This indicates the strain at any position of the resistance strain gauge in the four branches.

8. The determination method according to claim 7, characterized in that, The relationship between the strain of each resistance strain gauge in the four branches and the cable force F satisfies the following Equation 2: ； ； In the formula, ε1 and ε1' represent the strain at positions of resistance strain gauges R1 and R1' in the first branch, respectively; ε2 and ε2' represent the strain at positions of resistance strain gauges R2 and R2' in the second branch, respectively; ε3 and ε3' represent the strain at positions of resistance strain gauges R3 and R3' in the third branch, respectively; and ε4 and ε4' represent the strain at positions of resistance strain gauges R4 and R4' in the fourth branch, respectively. This represents the strain measured by longitudinally arranged resistance strain gauges. This represents the strain measured by the horizontally arranged resistance strain gauges. α represents the spurious strain caused by temperature, F represents the cable force, E represents the elastic modulus of the anchor cup end material, r1 represents the radius of the circular cross section on the upper surface of the frustum at the anchor cup end, r2 represents the radius of the circular cross section on the lower surface of the frustum at the anchor cup end, α represents the angle between the generatrix of the frustum at the anchor cup end and the central axis, and μ represents the Poisson's ratio of the anchor cup end material.

9. The determination method according to claim 8, characterized in that, The bridge output voltage U0 and the bridge excitation voltage U i The relationship between the resistance of the eight resistance strain gauges in the four branches and the resistance of the strain gauges satisfies the following relationship (Equation 3): In the formula, This indicates the magnitude of the change in resistance of the resistive strain gauge R1 caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R1' caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R2 caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R2' caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R3 caused by strain. This indicates the magnitude of the change in resistance of the resistance strain gauge R3' caused by strain. This indicates the magnitude of the change in resistance of the resistance strain gauge R4 caused by strain. This indicates the magnitude of the change in resistance of the resistive strain gauge R4' caused by strain.

10. The determination method according to claim 9, characterized in that, The determination of the cable force is achieved by substituting equation one and equation two into equation three: In the formula, The above formula can be simplified to: The cable force F is: 。

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