System and method for detecting effective preload force of cable clamp screw of long-span suspension bridge

Abstract

The present invention discloses a system and method for detecting the effective pre-tightening force of a cable clamp screw of a long-span suspension bridge. A nut clamp is sleeved on the cable clamp nut of the suspension bridge cable clamp, and a sensor for detecting the contact state of the cable clamp nut is provided on the nut clamp; a hydraulic screw puller can be connected to the exposed section of the cable clamp screw of the suspension bridge cable clamp and abut against the upper cable clamp surface of the suspension bridge cable clamp. The present invention can apply tension to the exposed section of the cable clamp screw through the hydraulic screw puller to achieve pulling of the cable clamp screw. The detection result of the sensor provided on the nut clamp can be used to determine whether the cable clamp nut is separated from the upper cable clamp surface, so as to determine the timing of the cable clamp nut being separated from the upper cable clamp surface. When it is determined that the cable clamp nut is separated from the upper cable clamp surface, the effective pre-tightening force value of the suspension bridge cable clamp is determined according to the tension value applied by the hydraulic screw puller at this time. The present invention is low in cost and does not damage the screw, and has obvious technical advantages over similar screw pre-tightening force detection methods.

Description

Technical Field

[0001] The present invention relates to the field of bridge engineering, and in particular to a system and method for detecting the effective pre-tightening force of a cable clamp screw of a long-span suspension bridge. Background Art

[0002] The suspender cables transmit the tensile forces generated by structural dead loads and vehicle live loads to the main cables, making them crucial force-transmitting components of suspension bridges. Clamp screws apply a preload to secure the clamps in place on the cables, counteracting the downward forces generated by the cable tension and preventing clamp slippage and cable system failure. Clamp screw preload is crucial for force distribution throughout the structure's load-bearing system. If the clamp screw preload is too low, the clamps will slip, redistributing forces in adjacent cables and altering the main girder alignment. This process has a divergent effect, making it irreversible and extremely difficult to recover from. Section 3.5.9 of the "Code for Maintenance of Highway Bridges and Culverts" (JTG 5120-2021) requires inspection of "cable clamps between the upper ends of suspension bridge hangers and the main cables for looseness, displacement, and damage." Section 7.2.1 of the "Standard for Technical Condition Assessment of Highway Bridges" (JTG TH21-2011) also considers clamp slippage exceeding 10mm a serious defect. Existing methods for detecting the preload force of cable clamp screws in suspension bridges include torque wrench method, piezoelectric impedance method and ultrasonic detection method. In actual applications, the torque wrench method is easily affected by factors such as the friction coefficient of the screw contact surface and the threaded part, which can cause large measurement errors. The piezoelectric impedance technology is still in the qualitative analysis stage for screw connection status detection and cannot yet achieve quantitative detection of the screw's axial stress. It also requires effective coupling of the piezoelectric element with the component being tested, which makes the operation cumbersome and complicated in actual applications. The ultrasonic detection method is divided into single-wave method and dual-wave method. The single-wave method indirectly obtains the axial stress of the screw by measuring the transit time of the ultrasonic wave in the screw being tested. However, in actual projects, the screw has been installed on the cable clamp and cannot be accurately measured. Therefore, the measurement error is large in actual projects. The dual-wave method requires the simultaneous installation of two ultrasonic probes, longitudinal wave and shear wave, for testing. The shear wave is less sensitive to stress changes, and it is also difficult to use shear waves to measure the transit time in actual applications. Generally, a small section of the screw will be exposed at both ends for the convenience of installation and tensioning. When the ultrasonic detection method detects the screw preload, the exposed section is in a stress-free state, which will lead to certain errors in the test results. It can be seen that the existing technology still has various problems in detecting the pre-tightening force of the cable clamp screw of the suspension bridge, so a technical solution that can accurately detect the pre-tightening force of the cable clamp screw of the suspension bridge is needed. Summary of the Invention

[0003] In order to solve the problems existing in the prior art, the purpose of the present invention is to provide a system and method for detecting the effective pre-tightening force of the cable clamp screw of a large-span suspension bridge. The present invention has the advantages of high precision and relatively accurate detection results for the pre-tightening force detection of the cable clamp screw of the suspension bridge.

[0004] The technical solution adopted in the present invention is as follows:

[0005] Long-span suspension bridge cable clamp screw effective preload detection system, including nut clamp and hydraulic screw puller;

[0006] The nut clamp is sleeved on the cable clamp nut of the suspension bridge cable clamp, and the nut clamp is provided with a sensor for detecting the contact state of the cable clamp nut;

[0007] The hydraulic screw puller can be connected to the exposed section of the cable clamp screw of the suspension bridge cable clamp and abut against the upper cable clamp surface of the suspension bridge cable clamp. The hydraulic screw puller can apply tension to the cable clamp screw.

[0008] Preferably, the sensor includes at least one of a micro pressure gauge, positive and negative electrode sheets and a steel strain gauge, the micro pressure gauge is arranged on the side of the nut clamp close to the upper cable clamp surface of the suspension bridge cable clamp; the positive and negative electrode sheets are arranged on the side of the nut clamp close to the upper cable clamp surface of the suspension bridge cable clamp; the steel strain gauge is arranged on the part of the nut clamp that contacts the side wall of the cable clamp nut of the suspension bridge cable clamp.

[0009] Preferably, the nut clamp includes a first clamp locking head, a first clamp short section, a second clamp short section, a third clamp short section, a fourth clamp short section and a second clamp locking head, one end of the first clamp locking head is hinged to one end of the first clamp short section, the other end of the first clamp short section is hinged to one end of the second clamp short section, the other end of the second clamp short section is hinged to one end of the third clamp short section, the other end of the third clamp short section is hinged to one end of the fourth clamp short section, the other end of the fourth clamp short section is hinged to one end of the second clamp locking head, and the other end of the second clamp locking head is detachably fastened to the other end of the first clamp locking head;

[0010] The inner ring of the nut clamp is adapted to the outer ring structure of the cable clamp nut. When the nut clamp is sleeved on the cable clamp nut of the suspension bridge cable clamp, the first clamp locking head, the first clamp short section, the second clamp short section, the third clamp short section, the fourth clamp short section and the second clamp locking head are in contact with the six side surfaces of the cable clamp nut respectively.

[0011] At least one of the first clamp pup section, the second clamp pup section, the third clamp pup section, and the fourth clamp pup section is provided with a sensor for detecting a contact state of the cable clamp nut.

[0012] Preferably, when the sensor includes a micro pressure gauge, at least one of the first clamp short section, the second clamp short section, the third clamp short section, and the fourth clamp short section is provided with the micro pressure gauge;

[0013] When the sensor includes positive and negative electrode sheets, at least one of the first clamp short section, the second clamp short section, the third clamp short section, and the fourth clamp short section is provided with the positive and negative electrode sheets;

[0014] When the sensor includes a steel strain gauge, at least one of the first clamp pup section, the second clamp pup section, the third clamp pup section, and the fourth clamp pup section is provided with the steel strain gauge;

[0015] The sensor includes a micro pressure gauge and positive and negative electrode sheets, and the micro pressure gauge and the positive and negative electrode sheets are not arranged on the first clamp short section, the second clamp short section, the third clamp short section or the fourth clamp short section at the same time. The number of the micro pressure gauge is at least one, and the number of the positive and negative electrode sheets is at least one;

[0016] When the sensor includes a micro pressure gauge and a steel strain gauge, at least one of the first clamp pup section, the second clamp pup section, the third clamp pup section, and the fourth clamp pup section is provided with the micro pressure gauge and the steel strain gauge;

[0017] When the sensor includes positive and negative electrode sheets and a steel strain gauge, at least one of the first clamp pup section, the second clamp pup section, the third clamp pup section and the fourth clamp pup section is provided with the positive and negative electrode sheets and the steel strain gauge;

[0018] When the sensor includes a micro pressure gauge, positive and negative electrode sheets and a steel strain gauge, at least one of the first clamp pup section, the second clamp pup section, the third clamp pup section and the fourth clamp pup section is provided with the micro pressure gauge; at least one of the first clamp pup section, the second clamp pup section, the third clamp pup section and the fourth clamp pup section is provided with the positive and negative electrode sheets; and the micro pressure gauge and the positive and negative electrode sheets are not provided on the first clamp pup section, the second clamp pup section, the third clamp pup section or the fourth clamp pup section at the same time, the number of micro pressure gauges is at least one, and the number of positive and negative electrode sheets is at least one; at least one of the first clamp pup section, the second clamp pup section, the third clamp pup section and the fourth clamp pup section is provided with the steel strain gauge.

[0019] Preferably, the other end of the second clamp locking head is detachably fastened to the other end of the first clamp locking head via a quick-release structure.

[0020] Preferably, the hydraulic screw puller includes a threaded clamping set, a hydraulic telescopic mechanism and a reaction bridge, the threaded clamping set is provided with a central threaded hole that is threadably matched with the exposed section of the cable clamp screw; the hydraulic telescopic mechanism is provided with a central hole, and the hydraulic telescopic mechanism is sleeved on the outside of the threaded clamping set through the central hole;

[0021] The reaction bridge adopts a cylindrical structure. The reaction bridge is sleeved on the outside of the exposed section of the cable clamp screw and is located between the hydraulic telescopic mechanism and the upper cable clamp. The reaction bridge is sleeved on the outer ring of the nut clamp. The two ends of the reaction bridge are respectively against the surface of the upper cable clamp and one end of the hydraulic telescopic mechanism; the other end of the hydraulic telescopic mechanism is connected to or against the threaded clamping set. When the hydraulic telescopic mechanism is extended, the hydraulic telescopic mechanism can make the exposed section of the cable clamp screw bear tension through the threaded clamping set and the reaction bridge.

[0022] Preferably, the hydraulic telescopic mechanism includes an oil cylinder, which includes an annular outer shell and a telescopic ring coaxially sealed with the annular outer shell, the telescopic ring serves as the piston rod of the oil cylinder, the outer shell is sleeved on the outside of the threaded clamping set through the inner hole, the end of the telescopic ring is connected to or offset with the threaded clamping set, and the reaction bridge is offset with the outer shell.

[0023] Preferably, the threaded clamping sleeve is provided with an outer flange, and the other end of the hydraulic telescopic mechanism abuts against the outer flange of the threaded clamping sleeve;

[0024] A groove for embedding the end of the reaction bridge is provided at a position on the hydraulic telescopic mechanism that abuts against the reaction bridge.

[0025] The present invention further provides a method for detecting the effective pre-tightening force of a cable clamp screw of a long-span suspension bridge. The method is performed using the long-span suspension bridge cable clamp screw effective pre-tightening force detection system of the present invention, comprising the following steps:

[0026] S1. Slide the nut fixture onto the cable clamp nut of the suspension bridge cable clamp, and place the sensor on the nut fixture in the detection position;

[0027] S2, a hydraulic screw puller is connected to the exposed section of the clamp screw of the suspension bridge cable clamp and abuts against the upper clamp surface of the suspension bridge cable clamp;

[0028] S3. Apply tension to the exposed section of the cable clamp screw of the suspension bridge cable clamp through a hydraulic screw puller, detect the stress state of the cable clamp nut in real time through a sensor on the nut clamp, and determine whether the cable clamp nut is detached from the upper cable clamp surface based on the detection signal of the sensor. When the cable clamp nut is detached from the upper cable clamp surface, obtain the tension value applied by the hydraulic screw puller at this time, and the tension value is used as the effective preload force of the cable clamp screw of the long-span suspension bridge.

[0029] Preferably, the sensor includes at least one of a micro pressure gauge, a positive and negative electrode sheet, and a steel strain gauge; when performing S1, the micro pressure gauge is in close contact with a raised gasket on the upper clamp surface of the suspension bridge clamp;

[0030] The positive and negative electrodes are in close contact with the raised gaskets on the upper cable clamp surface of the suspension bridge cable clamp. When the upper cable clamp surface is provided with a coating, the coating is removed to expose the metal surface, and the positive and negative electrodes are in close contact with the metal surface of the upper cable clamp; the steel strain gauge is in close contact with the side wall of the cable clamp nut of the suspension bridge cable clamp.

[0031] The present invention has the following beneficial effects:

[0032] In the present invention, a system for detecting the effective preload force of a cable clamp screw for a long-span suspension bridge utilizes a hydraulic screw puller to apply tension to the exposed section of the cable clamp screw, thereby pulling the cable clamp screw. A nut clamp is provided, and a sensor is provided on the nut clamp for detecting the contact state of the cable clamp nut. The sensor's detection result can be used to determine whether the cable clamp nut has disengaged from the upper cable clamp surface, thereby determining the timing of the cable clamp nut's disengagement from the upper cable clamp surface. When the cable clamp nut is determined to have disengaged from the upper cable clamp surface, the effective preload force of the cable clamp screw for the long-span suspension bridge can be obtained based on the tension value applied by the hydraulic screw puller at that time. It can be seen that the system for detecting the effective preload force of a cable clamp screw for a long-span suspension bridge of the present invention has a simple structure and convenient force application. The sensor can accurately determine the timing of the cable clamp nut's disengagement from the upper cable clamp surface, thereby effectively obtaining the effective preload force of the cable clamp screw for the long-span suspension bridge, and the obtained result is more accurate. Therefore, the present invention has the advantages of high precision and relatively accurate detection results. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 This is a connection diagram of the effective pre-tightening force detection system for the cable clamp screw of a long-span suspension bridge of the present invention;

[0034] Figure 2 This is a vertical exploded view of the hydraulic screw puller of the present invention;

[0035] Figure 3 This is a connection plan view of the hydraulic screw puller of the present invention;

[0036] Figure 4 This is a cross-sectional view of the hydraulic screw puller of the present invention;

[0037] FIG5( a ) is a top view of the nut clamp sleeve of the present invention; FIG5( b ) is a bottom view of the nut clamp sleeve of the present invention;

[0038] FIG6( a ) is a first three-dimensional structural diagram of a nut clamp sleeve of the present invention; FIG6( b ) is a second three-dimensional structural diagram of a nut clamp sleeve of the present invention;

[0039] FIG7( a ) is a first three-dimensional structural diagram of the positive and negative electrode clamps according to an embodiment of the present invention; FIG7( b ) is a second three-dimensional structural diagram of the positive and negative electrode clamps according to an embodiment of the present invention;

[0040] FIG8( a ) is a first three-dimensional structural diagram of a pressure gauge fixture according to an embodiment of the present invention; FIG8( b ) is a second three-dimensional structural diagram of a pressure gauge fixture according to an embodiment of the present invention;

[0041] Figure 9 A three-dimensional structural diagram of the clamp tightening device according to an embodiment of the present invention;

[0042] FIG10( a ) is a first three-dimensional structural diagram of a clamp fastening a pressure plate according to an embodiment of the present invention; FIG10( b ) is a second three-dimensional structural diagram of a clamp fastening a pressure plate according to an embodiment of the present invention;

[0043] Figure 11 A three-dimensional structural diagram of a fastening screw and a fastening nut in an embodiment of the present invention;

[0044] FIG12( a ) is a first three-dimensional structural diagram of the A-type clamp lock head in an embodiment of the present invention; FIG12( b ) is a second three-dimensional structural diagram of the A-type clamp lock head in an embodiment of the present invention;

[0045] FIG13( a ) is a first three-dimensional structural diagram of the B-type clamp lock head (14) of the present invention; FIG13( b ) is a second three-dimensional structural diagram of the B-type clamp lock head (14) of the present invention;

[0046] FIG14( a ) is a diagram showing pressure changes in an embodiment of the present invention; FIG14( b ) is a diagram showing strain changes in an embodiment of the present invention; and FIG14( c ) is a diagram showing voltage changes in an embodiment of the present invention.

[0047] In the figure, 1-thread clamping set, 2-expansion ring, 3-oil cylinder, 4-oil inlet, 5-oil outlet, 6-reaction bridge, 7-nut clamp, 8-cable clamp screw, 9-cable clamp nut, 10-upper cable clamp, 11-lower cable clamp, 12-hydraulic oil, 13-A type clamp lock, 14-B type clamp lock, 15-positive and negative clamps, 16-pressure gauge clamp, 17-circuit wire, 18-fastening screw, 19-fastening nut, 20-clamp fastening pressure piece, 21-connecting pin, 22 -Pressing plate fixing hole, 23-Pressing plate fixing buckle, 24-Positive and negative electrode plates, 25-Micro pressure gauge, 26-Steel strain gauge, 27-Strain gauge line hole, 28-Positive and negative electrode line holes, 29-Connecting pin hole, 30-Main line hole, 31-Micro pressure gauge hole, 32-Hydraulic screw puller, 33-Signal amplifier, 34-Signal collector, 35-Laptop computer, 36-Sling hole, 37-Main cable through hole, 38-Interface, 39-Oil pipe, 40-Data acquisition system. DETAILED DESCRIPTION

[0048] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0049] This invention addresses the issues of low detection accuracy, large errors, and a cumbersome detection process for the preload force of cable clamp screws in suspension bridges. By incorporating the principle of equivalent substitution, we have developed a system and method for detecting the effective preload force of cable clamp screws in large-span suspension bridges. By integrating multiple technologies to monitor the contact state between the nut and the preload bolt in real time, this invention enables precise detection of the preload force of cable clamp screws in suspension bridges. This new screw preload force detection device boasts high detection accuracy (error can be controlled within 5%) and is non-destructive to the screw, offering significant advantages over similar screw preload force detection devices.

[0050] See also Figures 1 to 13(b) The present invention provides a long-span suspension bridge cable clamp screw effective pre-tightening force detection system comprising a nut clamp 7, a hydraulic screw puller 32 and a data acquisition system 40.

[0051] The cable clamp of a suspension bridge usually includes an upper cable clamp 10, a lower cable clamp 11, a plurality of cable clamp screws 8 and a cable clamp nut 9. The upper cable clamp 10 and the lower cable clamp 11 are fastened together by the cable clamp screw 8 and the cable clamp nut 9. The upper cable clamp 10 and the lower cable clamp 11 are semi-annular special-shaped structures, and the material is ZG20Mn. After the upper cable clamp 10 and the lower cable clamp 11 are closed, the middle part is the main cable through hole 37, through which the main cable of the suspension bridge passes. There are a plurality of bolt through holes on the upper surface of the rectangular block special-shaped structures on both sides of the upper cable clamp 10 and the lower cable clamp 11. The cable clamp screw 8 and the cable clamp nut 9 cooperate to fasten the upper cable clamp 10 and the lower cable clamp 11. For details of the structure, see Figures 1 and 2 .

[0052] The main body of the nut clamp 7 includes an A-type clamp lock head 13, a B-type clamp lock head 14, positive and negative electrode clamps 15, a pressure gauge clamp 16 and a sensor, and also includes other accessories such as a circuit wire 17, a fastening screw 18, a fastening nut 19, a clamp fastening pressure plate 20, a connecting pin 21 and a pressure plate fixing buckle 23. The sensor includes positive and negative electrode plates 24, a micro pressure gauge 25 and a steel strain gauge 26.

[0053] The hydraulic screw puller 32 includes a thread clamping set 1 , a telescopic ring 2 , a cylinder 3 and a reaction bridge 6 .

[0054] The data acquisition system 40 includes a signal amplifier 33 , a signal collector 34 and a laptop computer 35 .

[0055] The thread clamping set 1 is a cylindrical structure composed of upper and lower rings, made of 45 steel. The outer diameter of the upper ring (which serves as a protruding flange) is 260mm, the inner diameter is 90mm, and the height is 80mm; the outer diameter of the lower ring is 150mm, the inner diameter is 90mm, and the height is 190mm. The inner wall of the thread clamping set 1 is provided with an internal thread within the height range, which can be threadedly connected to the exposed section of the cable clamp screw 8. For detailed structure, see Figures 3 and 4 .

[0056] The telescopic ring 2 is a cylindrical structure composed of upper and lower rings, made of 45 steel. The upper ring has an outer diameter of 280mm, an inner diameter of 160mm, and a height of 20mm; the lower ring has an outer diameter of 260mm, an inner diameter of 190mm, and a height of 80mm. The thread clamping set 1 is assembled by embedding the telescopic ring 2 in the lower ring. Figures 3 and 4 .

[0057] The oil cylinder 3 is annular and cylindrical, with groove structures on the upper and lower end faces, and is made of 45# steel. The outer diameter is 300mm, the inner diameter is 150mm, and the height is 130mm; the upper annular groove is 35mm wide and 80mm deep; the lower annular groove is 244mm in diameter and 20mm in depth. There are two circular holes on the outer wall of the oil cylinder 3, with a diameter of 24mm and a depth of 26mm. The inner walls of the holes are threaded, and the holes are connected to the bottom of the upper annular groove, with a connecting port diameter of 12mm. The telescopic ring 2 is assembled by embedding the lower circular ring in the upper groove of the oil cylinder 3. Hydraulic oil 12 can be injected into the groove through the connecting port to play the role of oil pressure. For details of the structure, see Figure 4 .

[0058] Interface 38 is a cylindrical structure made of 45 steel, 76mm long and 24mm in diameter, with a circular hole in the middle and a diameter of 12mm. The outer wall is threaded, and 26mm away from one end there is a section of cylinder with a diameter of 40mm and a height of 20mm, which divides the thread into two ends. One end of interface 38 is threadedly connected to the hole in the outer wall of cylinder 3. Figure 4 .

[0059] The oil inlet 4 is a cylindrical special-shaped structure, made of 45 steel, with a length of 150mm. One end is a hexagonal column with a side length of 20mm, a distance of 34.6mm across the sides, and a height of 30mm. There is a circular hole in the middle with a diameter of 12mm, which is connected to the oil pipe 39. The oil pipe 39 pressurizes the oil cylinder 3 by connecting to the pressure port of the hydraulic pump; the other end is a hexagonal column with a side length of 20mm, a distance of 34.6mm across the sides, and a height of 30mm. There is a circular hole in the middle with a diameter of 24mm. The inner wall is threaded and can be threadedly connected to the interface 38; the middle of the oil inlet 4 is a cylindrical structure with a diameter of 50mm and a height of 50mm. There is a circular hole inside with a diameter of 12mm. The oil outlet 5 is the same item as the oil inlet 4, but the functions are different. The oil outlet 5 is connected to the pressure relief port of the hydraulic pump through the oil pipe 39 to relieve the pressure on the oil cylinder 3. See the structure for details. Figure 4 .

[0060] The hydraulic pump injects or discharges hydraulic oil 12 into the oil cylinder 3 through the motor to raise or lower the telescopic ring 2 to achieve the effect of stretching or releasing the cable clamp screw 8.

[0061] The reaction bridge 6 is a circular cylindrical structure made of 45 steel. The outer diameter is 240mm, the inner diameter is 200mm, and the height is 150mm. The reaction bridge 6 is assembled through the groove at the bottom of the embedded oil cylinder 3, and plays the role of applying the reaction force of the cable clamp screw 8 to the upper cable clamp 10. Figures 3 and 4 .

[0062] The nut clamp 7 is a mechanical combination structure, the main structure includes an A-type clamp lock head 13, a B-type clamp lock head 14, two positive and negative clamps 15, two pressure gauge clamps 16, two fastening screws 18, two fastening nuts 19, a clamp fastening plate 20 and five connecting pins 21. Figures 5(a) to 6(b) .

[0063] The A-type clamp lock head 13 is a cubic, irregularly shaped structure made of PVC, 37.8 mm long, 25 mm wide, and 30 mm thick. One end features two bolt holes with a diameter of 6 mm and a center-to-center distance of 14 mm, through which fastening screws 18 pass. A semicircular platform extends from the center of the other end. The platform is 25 mm long, 25 mm wide, and 10 mm thick. It also features a connecting pin hole 29 with a diameter of 6 mm, extending parallel to the thickness. See Figures 12(a) and 12(b) for details.

[0064] The B-type clamp lock head 14 is a square-shaped structure made of PVC, with a length of 37.8mm, a width of 25mm, and a thickness of 30mm. One end has two bolt holes with a diameter of 6mm and a center distance of 14mm between the two holes, through which the fastening screw 18 passes. Two semicircular platforms extend outward from the middle of the other end of the B-type clamp lock head 14. The platforms are 25mm long, 25mm wide, and 10mm thick. Each platform has a connecting pin hole 29 with a diameter of 6mm, and the line connecting the centers of the two connecting pin holes 29 is parallel to the thickness direction. A pressure plate fixing hole 22 with a diameter of 2mm is also provided on one of the semicircular platforms, into which a pressure plate fixing buckle 23 can be inserted. It is used to fix the clamp fastening pressure plate 20 and prevent the fixed clamp fastening pressure plate 20 from generating relative displacement with the B-type clamp lock head 14, which would interfere with the operation of the clamp under dynamic load cycles. The structure is detailed in Figures 13(a) and 13(b).

[0065] The clamp fastening plate 20 is a shaped, sheet-like structure made of aluminum alloy, 44mm long, 5mm wide, and 5.6mm thick. Three semicircular platforms, each 5mm in diameter, extend from one end. Each platform has a 3mm-diameter circular bolt hole through which the fastening screw 18 passes. A 2mm-diameter plate fixing hole 22 is located on the top surface of the clamp fastening plate 20, which accepts the plate fixing clip 23. See Figures 10(a) and 10(b) for details of the structure.

[0066] The fixing screw 18 is a threaded cylindrical structure, made of 45# steel, with a diameter of 5.4mm; a cylindrical ring structure is left at the end, with an outer diameter of 9mm and an inner diameter of 3mm, and the direction of the ring opening is perpendicular to the axis of the screw. Figure 11 The fixing nut 19 is a hexagonal columnar structure made of 45# steel with a round hole in the middle. The hexagonal side length is 5mm, the vertical distance between the opposite sides is 8.59mm, the hole diameter is 5.8mm and the inner wall is threaded. Figure 11 .

[0067] The A-type clamp locking head 13 , the B-type clamp locking head 14 and the clamp fastening pressing piece 20 are detachably connected as one body through the fastening screw 18 and the fastening nut 19 to form a quick-release structure.

[0068] The positive and negative electrode fixture 15 is a block-shaped special-shaped structure made of PVC, with a length of 30mm, a width of 25mm, and a thickness of 30mm. One end extends from the midpoint of the thickness direction a semicircular platform with a length of 25mm, a width of 25mm, a thickness of 10mm, a semicircular radius of 12.5mm, and an opening parallel to the thickness direction of the connecting pin hole 29 with a diameter of 6mm. The other end extends two semicircular platforms with a length of 25mm, a width of 25mm, a thickness of 10mm, and a semicircular radius of 12.5mm. Each platform has A connecting pin hole 29 with a diameter of 6mm is located parallel to the thickness of the fixture. The center of each of the two connecting pin holes 29 is parallel to the thickness of the fixture. A steel strain gauge 26 is embedded in the inner surface of the positive and negative electrode fixtures 15. The strain gauge is 10mm long, 4mm wide, and 0.2mm thick. One end of a circuit conductor 17 connects to the steel strain gauge 26 through a reserved strain gauge hole 27 in the fixture 15. The other end extends to the other side and connects to the main line hole 30. The data line of the steel strain gauge 26 enters the main line hole 30 through the strain gauge hole 27. Two positive and negative electrode sheets 24 are located at the bottom of the fixture 15. The positive and negative electrode sheets are 12mm long, 4mm wide, and 0.2mm thick. The fixture 15 is used to detect the contact between the nut fixture 7 and the upper cable clamp 10. When the positive and negative electrode fixtures 15 make contact with the upper cable clamp 10, the circuit is connected, indicating that the detection nut fixture 7 and the upper cable clamp 10 are in close contact. If the opposite is true, it indicates that the test nut clamp 7 is disengaged from the upper cable clamp 10. Circuit wires 17 connected to the positive and negative electrode sheets 24 extend through the positive and negative electrode wire holes 28 built into the positive and negative electrode clamps 15 to the main wire hole 30. See Figures 7(a) and 7(b) for details of the structure.

[0069] The pressure gauge fixture 16 is a rectangular block-shaped special-shaped structure made of PVC, with a length of 30mm, a width of 25mm and a thickness of 30mm. A semicircular platform extends from the midpoint of the thickness direction at one end. The platform is 25mm long, 25mm wide, 10mm thick, and has a semicircular radius of 12.5mm. There is also a connecting pin hole 29 with an opening parallel to the thickness direction and a diameter of 6mm. Two semicircular platforms extend from the other end. The platform is 25mm long, 25mm wide, 10mm thick, and has a semicircular radius of 12.5mm. Each platform has a connecting pin hole 29 with an opening parallel to the thickness direction and a diameter of 6mm. The line connecting the centers of the two connecting pin holes 29 is parallel to the thickness direction. A steel strain gauge 26 is embedded in the side surface on one side. The strain gauge is 10mm long, 4mm wide and 0.2mm thick. The contact part of the steel strain gauge 26 with the pressure gauge fixture 16 is covered with insulating material to prevent it from interfering with the current signal. A strain gauge line hole 27 is reserved at one end of the steel strain gauge 26. The strain gauge line hole 27 is a circular hole with a diameter of 4 mm. It extends to the other side and is connected to the main line hole 30. The circuit wire 17 of the steel strain gauge 26 enters the main line hole 30 through the strain gauge line hole 27; the main line hole 30 is a circular hole with a diameter of 4 mm. The hole passes through the pressure gauge fixture 16 along the length direction; a micro pressure gauge hole 31 with a diameter of 20 mm is set at the bottom of the pressure gauge fixture 16, and the micro pressure gauge 25 is embedded in it. The micro pressure gauge 25 is tightly compounded with the micro pressure gauge hole 31, and an insulating material is provided in the middle to prevent interference with circuit signals during use; the micro pressure gauge hole 31 extends to the main line hole 30, and the data line of the micro pressure gauge 25 enters the main line hole 30 through the micro pressure gauge hole 31. The micro-pressure gauge 25 monitors the contact between the pressure gauge fixture 16 and the nut fixture 7. As the hydraulic screw puller 32 operates, when the pressure reading on the micro-pressure gauge 25 gradually decreases to a minimum, it indicates that the pressure gauge fixture 16 has completely disengaged from the nut fixture 7. The structure of the pressure gauge fixture 16 is detailed in Figures 8(a) and 8(b).

[0070] The two positive and negative electrode clamps 15 are connected to the two pressure gauge clamps 16 by interactive pins. Together with the A-type clamp lock 13 and the B-type clamp lock 14, they form a closed ring-shaped nut clamp 7, which secures the clamp nut 9. A micro pressure gauge 25 is located at the bottom of the pressure gauge clamp 16, contacting a raised pad on the upper cable clamp surface. The positive and negative electrode plates 24 are located at the bottom of the positive and negative electrode clamps 15, also contacting raised pads on the upper cable clamp surface. The clamp fastening tab 20 and tightening screw 18 securely connect the A-type clamp lock 13 and the B-type clamp lock 14. The data lines of the positive and negative electrodes 24 pass through the positive and negative electrode holes 28 and enter the main line hole 30. The data line of the micro pressure gauge 25 passes through the micro pressure gauge hole 31 and enters the main line hole 30. The data line of the steel strain gauge 26 passes through the strain gauge hole 27 and enters the main line hole 30. Finally, they are combined into the circuit conductor 17. The circuit conductor 17 is connected to the signal amplifier 33 and transmits the data to the signal collector 34. Finally, it is connected to the laptop computer 35 for signal acquisition and processing. Figure 1 、 Figure 5(a) to Figure 5(b) .

[0071] According to the principle of static equilibrium, the effective preload force of the clamp screw 8 is equal to the tension applied to the clamp screw 8 during the initial separation of the clamp nut 9 from the upper clamp 10. After the nut clamp 7 clamps the clamp nut 9, a tight connection is established. Continued tension from the hydraulic screw puller 32 causes the clamp nut 9 and upper clamp 10 to tend to separate. By monitoring the status of the clamp nut 9 and upper clamp 10 in real time, the effective preload force of the clamp screw 8 can be accurately determined.

[0072] During use, the nut clamp 7 is pre-clamped around the cable clamp nut 9, ensuring that the micro pressure gauge 25 and the positive and negative electrodes 24 at the bottom of the nut clamp 7 are in close contact with the raised gaskets on the top of the upper cable clamp 10. If the upper cable clamp 10 has a waterproof coating, it is necessary to first remove the coating near the nut to expose the metal surface (and then spray an anti-corrosion coating again after the test is completed), so that the positive and negative electrodes 24 and the upper cable clamp 10 form a partial circuit.

[0073] A certain amount of preload is applied downward to the nut clamp 7, creating an initial pressure value between it and the upper cable clamp 10. Simultaneously, the clamp tightening pressure plate 20 is rotated to secure the nut clamp 7 to the outer periphery of the cable clamp nut 9, and a certain tightening force is then applied. The pressure plate fixing clip 23 is then inserted into the pressure plate fixing hole 22 to prevent the nut clamp 7 from loosening during the tensioning of the cable clamp screw 8. This process ensures that the steel strain gauge 26 on the inside of the nut clamp 7 is in close contact with the cable clamp nut 9. The preload force creates a certain constraint between the steel strain gauge 26 and the outer wall of the cable clamp nut 9, placing the steel strain gauge 26 in a triaxial stress state. Stress changes in the cable clamp nut 9 are reflected on the steel strain gauge 26.

[0074] Then, the circuit wires 17 of the positive and negative electrodes 24, micro pressure gauge 25, and steel strain gauge 26 are connected to the signal amplifier 33, then to the signal collector 34, and finally to the laptop computer 35. At this point, the laptop computer 35 measures the initial pressure value P0 of the micro pressure gauge 25, the initial strain value ε0 of the steel strain gauge 26, and the circuit closure indication signal of the positive and negative electrodes 24.

[0075] The hydraulic screw puller 32 is passed through the cable clamp screw 8, with its bottom contacting the upper cable clamp 10. The top threaded clamping set 1 clamps the threads of the cable clamp screw 8. The nut clamp 7 is located on the inner side of the bottom of the hydraulic screw puller 32 and has no contact with the hydraulic screw puller 32. Pressure is applied through the oil inlet 4 of the hydraulic pump, causing the telescopic ring 2 to rise, thereby stretching the cable clamp screw 8. The threaded clamping set 1 is threadedly connected to the cable clamp screw 8, so it drives the cable clamp screw 8 upward and the cable clamp nut 9 also moves upward. Before the hydraulic screw puller 32 is tensioned, the cable clamp nut 9 is in a compressive stress state due to the presence of preload, tightly adhering to the surface of the upper cable clamp 10. As the cable clamp screw 8 gradually stretches, the contact stress between the cable clamp nut 9 and the upper cable clamp 10 gradually decreases, and the cable clamp nut 9 slowly begins to separate from the surface of the upper cable clamp 10.

[0076] When the initial voltage value V0 of the positive and negative electrodes 24 drops to 0 and remains constant, the initial pressure value P0 of the micro pressure gauge 25 drops to P1 and remains constant, and the initial strain value ε0 of the steel strain gauge 26 drops to ε1 and remains constant, it can be determined that the cable clamp nut 9 has disengaged from the surface of the upper cable clamp 10. The tension value corresponding to the oil pressure value represents the effective preload in the cable clamp screw 8. Due to certain errors in engineering applications, three measurement methods are used to comprehensively determine the disengagement state of the cable clamp nut 9. Generally, the micro pressure gauge 25 is the most sensitive, and a DYHW-108 high-precision micro pressure sensor can be used. The transition between the contact and semi-contact state of the positive and negative electrodes 24 causes a slight delay in the tension reading when the cable clamp nut 9 disengages. The steel strain gauge 26 has a lower sensitivity when monitoring strain changes. The three methods are used in combination: when the cable clamp nut 9 is disengaged, the tension value reading of the micro pressure gauge 25 is used as the standard value. When the error between the tension value reading of the positive and negative electrodes 24 and the tension value reading of the micro pressure gauge 25 is less than 10%, the tension value reading of the micro pressure gauge 25 at this time can be determined as the effective preload force of the screw, and the tension value reading corresponding to the steel strain gauge 26 is used for secondary calibration to ensure that there will be no excessive error. The tension value change diagram is shown in Figures 14(a) to 14(c) It can be seen that the present invention uses three technical means to comprehensively detect the effective preload of the screw, with high detection accuracy (the error can be controlled within 5%), low cost and no damage to the screw, which has obvious technical advantages over similar screw preload detection methods.

Claims

1. The effective preload force detection system for the cable clamp screw of a long-span suspension bridge is characterized by: It includes a nut clamp (7) and a hydraulic screw puller (32); The nut clamp (7) is sleeved on a cable clamp nut (9) of a suspension bridge cable clamp, and a sensor for detecting a contact state of the cable clamp nut (9) is provided on the nut clamp (7); The hydraulic screw puller (32) can be connected to the exposed section of the cable clamp screw (8) of the suspension bridge cable clamp and abut against the surface of the upper cable clamp (10) of the suspension bridge cable clamp. The hydraulic screw puller (32) can apply tension to the cable clamp screw (8); The sensor comprises at least one of a micro pressure gauge (25), a positive and negative electrode sheets (24) and a steel strain gauge (26); the micro pressure gauge (25) is arranged on one side of the nut clamp (7) close to the surface of the upper cable clamp (10) of the suspension bridge cable clamp; the positive and negative electrode sheets (24) are arranged on one side of the nut clamp (7) close to the surface of the upper cable clamp (10) of the suspension bridge cable clamp; and the steel strain gauge (26) is arranged on a portion of the nut clamp (7) that contacts a side wall of a cable clamp nut (9) of the suspension bridge cable clamp; The nut clamp (7) comprises a first clamp locking head, a first clamp short section, a second clamp short section, a third clamp short section, a fourth clamp short section and a second clamp locking head, one end of the first clamp locking head is hinged to one end of the first clamp short section, the other end of the first clamp short section is hinged to one end of the second clamp short section, the other end of the second clamp short section is hinged to one end of the third clamp short section, the other end of the third clamp short section is hinged to one end of the fourth clamp short section, the other end of the fourth clamp short section is hinged to one end of the second clamp locking head, and the other end of the second clamp locking head is detachably fastened to the other end of the first clamp locking head; The inner ring of the nut clamp (7) is adapted to the outer ring structure of the cable clamp nut (9); when the nut clamp (7) is sleeved on the cable clamp nut (9) of the suspension bridge cable clamp, the first clamp locking head, the first clamp short section, the second clamp short section, the third clamp short section, the fourth clamp short section and the second clamp locking head are in contact with six side surfaces of the cable clamp nut (9) respectively; At least one of the first clamp short section, the second clamp short section, the third clamp short section and the fourth clamp short section is provided with a sensor for detecting the contact state of the cable clamp nut (9); The hydraulic screw puller (32) comprises a threaded clamping set (1), a hydraulic telescopic mechanism and a reaction bridge (6); the threaded clamping set (1) is provided with a central threaded hole that matches the exposed thread section of the cable clamp screw (8); the hydraulic telescopic mechanism is provided with a central hole, and the hydraulic telescopic mechanism is sleeved on the outside of the threaded clamping set (1) through the central hole; The reaction bridge (6) adopts a cylindrical structure. The reaction bridge (6) is sleeved on the outside of the exposed section of the cable clamp screw (8) and is located between the hydraulic telescopic mechanism and the upper cable clamp (10). The reaction bridge (6) is sleeved on the outer ring of the nut clamp (7). The two ends of the reaction bridge (6) are respectively abutted against the surface of the upper cable clamp (10) and one end of the hydraulic telescopic mechanism; the other end of the hydraulic telescopic mechanism is connected to or abutted against the threaded clamping set (1). When the hydraulic telescopic mechanism is extended, the hydraulic telescopic mechanism can make the exposed section of the cable clamp screw (8) bear the tensile force through the threaded clamping set (1) and the reaction bridge (6).

2. The effective preload force detection system for cable clamp screws of a long-span suspension bridge according to claim 1 is characterized in that: When the sensor includes a micro pressure gauge (25), at least one of the first clamp short section, the second clamp short section, the third clamp short section, and the fourth clamp short section is provided with the micro pressure gauge (25); When the sensor includes positive and negative electrode sheets (24), at least one of the first clamp short section, the second clamp short section, the third clamp short section, and the fourth clamp short section is provided with the positive and negative electrode sheets (24); When the sensor includes a steel strain gauge (26), at least one of the first clamp short section, the second clamp short section, the third clamp short section, and the fourth clamp short section is provided with the steel strain gauge (26); When the sensor comprises a micro pressure gauge (25) and positive and negative electrode sheets (24), the micro pressure gauge (25) and the positive and negative electrode sheets (24) are not simultaneously arranged on the first clamp short section, the second clamp short section, the third clamp short section or the fourth clamp short section, the number of the micro pressure gauge (25) is at least one, and the number of the positive and negative electrode sheets (24) is at least one; When the sensor comprises a micro pressure gauge (25) and a steel strain gauge (26), at least one of the first clamp short section, the second clamp short section, the third clamp short section and the fourth clamp short section is provided with the micro pressure gauge (25) and the steel strain gauge (26); When the sensor comprises positive and negative electrode sheets (24) and a steel strain gauge (26), at least one of the first clamp short section, the second clamp short section, the third clamp short section and the fourth clamp short section is provided with the positive and negative electrode sheets (24) and the steel strain gauge (26); When the sensor comprises a micro pressure gauge (25), a positive and negative electrode sheets (24) and a steel strain gauge (26), at least one of the first clamp short section, the second clamp short section, the third clamp short section and the fourth clamp short section is provided with the micro pressure gauge (25); at least one of the first clamp short section, the second clamp short section, the third clamp short section and the fourth clamp short section is provided with the positive and negative electrode sheets (24); and the micro pressure gauge (25) and the positive and negative electrode sheets (24) are not provided on the first clamp short section, the second clamp short section, the third clamp short section or the fourth clamp short section at the same time, the number of the micro pressure gauge (25) is at least one, and the number of the positive and negative electrode sheets (24) is at least one; and at least one of the first clamp short section, the second clamp short section, the third clamp short section and the fourth clamp short section is provided with the steel strain gauge (26).

3. The effective preload force detection system for cable clamp screws of a long-span suspension bridge according to claim 1 is characterized in that: The other end of the second clamp locking head is detachably and fastened to the other end of the first clamp locking head via a quick release structure.

4. The effective preload force detection system for cable clamp screws of a long-span suspension bridge according to claim 1 is characterized in that: The hydraulic telescopic mechanism comprises an oil cylinder (3), the oil cylinder (3) comprising an annular outer shell and a telescopic ring (2) coaxially sealed with the annular outer shell, the telescopic ring (2) serving as a piston rod of the oil cylinder (3), the outer shell being sleeved on the outside of a threaded clamping set (1) through an inner hole, the end of the telescopic ring (2) being connected to or abutting against the threaded clamping set (1), and the reaction bridge (6) abutting against the outer shell.

5. The effective preload force detection system for cable clamp screws of a long-span suspension bridge according to claim 1 is characterized in that: An outer flange is provided on the threaded clamping sleeve (1), and the other end of the hydraulic telescopic mechanism abuts against the outer flange of the threaded clamping sleeve (1); A groove for embedding the end of the reaction bridge (6) is provided at a position on the hydraulic telescopic mechanism that abuts against the reaction bridge (6).

6. A method for detecting the effective preload force of a cable clamp screw of a long-span suspension bridge, characterized in that: The method is carried out using the long-span suspension bridge cable clamp screw effective preload force detection system according to any one of claims 1 to 5, and comprises the following steps: S1, sleeve the nut clamp (7) onto the cable clamp nut (9) of the suspension bridge cable clamp, and place the sensor on the nut clamp (7) at a detection position; S2, a hydraulic screw puller (32) is connected to the exposed section of the cable clamp screw (8) of the suspension bridge cable clamp and abuts against the surface of the upper cable clamp (10) of the suspension bridge cable clamp; S3. A tension is applied to the exposed section of the cable clamp screw (8) of the suspension bridge cable clamp by a hydraulic screw puller (32), and the stress state of the cable clamp nut (9) is detected in real time by a sensor on the nut clamp (7). It is determined whether the cable clamp nut (9) is detached from the surface of the upper cable clamp (10) based on the detection signal of the sensor. When the cable clamp nut (9) is detached from the surface of the upper cable clamp (10), the tension value applied by the hydraulic screw puller (32) at this time is obtained, and the tension value is used as the effective pre-tightening force of the cable clamp screw of the long-span suspension bridge.

7. The method for detecting effective preload force of a cable clamp screw of a long-span suspension bridge according to claim 6, characterized in that: When performing step S1, the micro pressure gauge (25) is in close contact with the raised gasket on the surface of the upper cable clamp (10) of the suspension bridge cable clamp; The positive and negative electrode sheets (24) are in close contact with the raised gaskets on the surface of the upper cable clamp (10) of the suspension bridge cable clamp. When the surface of the upper cable clamp (10) is provided with a coating, the coating is removed to expose the metal surface, and the positive and negative electrode sheets (24) are in close contact with the metal surface of the upper cable clamp (10); the steel strain gauge (26) is in close contact with the side wall of the cable clamp nut (9) of the suspension bridge cable clamp.

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