Intelligent parallel steel wire inhaul cable capable of automatically monitoring broken wire damage position and number in real time

Abstract

The invention discloses an intelligent parallel steel wire inhaul cable capable of automatically monitoring broken wire damage positions and the number of wires in real time. The parallel steel wire intelligent inhaul cable is formed by slightly twisting a common high-strength steel wire and a plurality of optical fiber intelligent wires placed at proper positions of a cable body or completely parallelly bundling the common high-strength steel wire and the optical fiber intelligent wires, and thermally extruding a polyethylene sheath. The optical fiber intelligent wire is packaged and protected by embedding a slotted steel wire into a sensing optical fiber which is arranged in a full-length manner, or the optical fiber is directly used as a middle beam and is prepared together with a high-strength fiber composite material. According to the intelligent inhaul cable with the parallel steel wires, any steel wire in the cable body can be monitored in real time, when the steel wire is broken, the broken wire position can be recognized and positioned in the first time, the number of the broken wires is quantitatively judged, and the service state of the inhaul cable is grasped in real time through timely early warning. The intelligent parallel steel wire inhaul cable can be widely applied to cable bearing bridges, large-span space structures, cable net structures and the like, and important support is provided for health monitoring of inhaul cable structures.

Description

Technical Field

[0001] The invention relates to a parallel steel wire intelligent cable with self-monitoring of broken wires applied in a large-span cable load-bearing system structure, and in particular to a real-time monitoring method for locating broken wires and quantifying the number of broken wires in a parallel steel wire intelligent cable. Background Art

[0002] Cables are important load-bearing components in structures such as cable-supported lattice shells, cable-supported dome structures, space structures, and cable-supported bridges. Parallel wire cables have smaller wind loads due to their good force uniformity, reliable anchoring, small on-site construction cable adjustment workload, and small cable diameter, making them more suitable for large-span structures such as large-span bridges. However, due to factors such as fatigue and corrosion, they often suffer from problems such as wire breakage, corrosion, or loose anchor heads during service, posing a major threat to structural safety. Therefore, it is crucial to identify these defects in a timely manner.

[0003] Fiber optic sensing technology, especially distributed fiber optic sensing measurement, has achieved the integration of multiple densely distributed sensors on the optical fiber arranged throughout the length, solving the problem of not being able to monitor the structure at all scales. The patent "A smart cable for distributed fiber optic strain monitoring of bridges" (CN201611186964.5) has developed a smart cable for distributed fiber optic strain monitoring of bridges, the cable includes multiple cable steel strands and at least one strain armored optical cable, wherein the strain armored optical cable includes steel wire, tight-wrapped optical fiber and sheath, there are multiple steel wires in the sheath, the middle of the sheath is a tight-wrapped optical fiber and the steel wire armor structure is formed by winding steel wire, which is used to realize the function of distributed fiber optic strain sensing. The cable combines distributed fiber optic strain measurement technology with traditional cable steel strand technology, thereby solving the problem of cable health monitoring. Based on relevant research, the present invention will explore a real-time self-monitoring method for locating the damage of broken wires and quantifying the number of broken wires inside parallel steel wire cables.

[0004] The present invention proposes a parallel steel wire intelligent cable with real-time self-monitoring of broken wire damage position and number, which solves the problems that the original fiber grating intelligent cable cannot monitor the entire scale and the traditional distributed intelligent cable cannot accurately locate the local damage of the cable body. Summary of the invention

[0005] The technical solution of the present invention:

[0006] A parallel steel wire intelligent cable with real-time self-monitoring of the position and number of broken wire damage, wherein the parallel steel wire intelligent cable is composed of a plurality of optical fiber intelligent wires 1 and steel wires 2 placed at the designed position of the cable body, which are slightly twisted or completely parallel to form a steel wire bundle, and an integral hot-extruded polyethylene sheath tube 3 is formed on the outer side of the steel wire bundle; the arrangement principle of the optical fiber intelligent wires 1 in the parallel steel wire intelligent cable is that any steel wire 2 and optical fiber intelligent wire 1 in the cable body has an adjacent optical fiber intelligent wire 1, but the arrangement method is not unique; each optical fiber intelligent wire 1 can monitor the stress state of the six adjacent steel wires 2 and / or optical fiber intelligent wires 1 around it, and when a plurality of optical fiber intelligent wires 1 are arranged at the designed position of the cable body, the distributed stress monitoring of any steel wire 2 and optical fiber intelligent wire 1 in the parallel steel wire intelligent cable can be realized;

[0007] Among them, the methods for locating broken wire damage and quantifying the number of broken wire roots under different damage conditions are as follows:

[0008] Working condition where one or more steel wires 2 are damaged at the same position: when any steel wire 2 in the cable body breaks, due to the occurrence of local stress redistribution, the optical fiber smart wire 1 adjacent to the broken wire will sense the stress change. Within the range of stress redistribution, the optical fiber smart wire 1 that was originally uniformly stressed will be subjected to greater stress. The stress within this range reaches a peak value at the place where the wire breaks, and gradually decreases with the increase of the distance from the broken wire, thereby presenting a triangle in a certain section of the strain curve. The occurrence of the broken wire can be identified by the change in the strain curve; the specific position of the broken wire can be identified by the peak of the triangular strain curve; at the same time, when multiple steel wires 2 are broken in the same position, the peak of the triangular strain curve will become higher, and the ratio of the strain maximum value of the triangular waveform part, that is, the peak value, to the waveform of the horizontal line part outside the triangular waveform range, that is, the strain value of the stable segment waveform is defined as the strain value. The strain increase coefficient is related to the number of broken wires. Through the sensitivity analysis of the cable body parameters, including the wire diameter d, the wire helix angle θ, the cable body length l, the sheath gripping force p, the friction coefficient u between the wires, the cable force f, and the number of wire coils n in the cable body, the influence of the strain increase coefficient on the selection of the quantitative threshold of the number of broken wires is obtained, so as to give the recommended threshold range of the strain increase coefficient for judging the number of broken wires: when the strain increase coefficient is 1.05-1.1, it is a single broken wire condition; when the strain increase coefficient is 1.1-1.15, it is a double broken wire condition; when the strain increase coefficient is 1.15-1.25, it is a three-broken wire condition; when the strain increase coefficient is 1.25-1.4, it is a four-broken wire condition; when the strain increase coefficient is 1.4-1.65, it is a five-broken wire condition; when the strain increase coefficient is above 1.65, it is a six-broken wire condition;

[0009] Working condition where one or more steel wires 2 are damaged at multiple positions: If a single or multiple wires are broken at different positions, multiple single or superimposed triangular waveforms will be generated, and the strain magnitude at the peak value will also be different; it can be regarded as a random combination of damage conditions at the same position. When the triangular waveforms do not affect each other, the position of the broken wire can be determined by the peak, and the number of broken wires can be determined by the strain increase coefficient; when the waveforms affect and superimpose each other, because the waveforms are triangular, the position of the broken wire can still be determined by the peak position even if they are superimposed; the number of broken wires can be determined by the strain increase coefficient.

[0010] Methods for improving the accuracy of broken wire identification, positioning and quantification: Since the strain data of the optical fiber intelligent wire 1 test has good repeatability, the damage information can be amplified by using the difference method of the strain data before and after the break (i.e., the strain data after the break minus the strain data before the break). This method can solve the problem of covering up the damage information due to insufficient test data accuracy.

[0011] Beneficial effects of the present invention: The parallel steel wire intelligent cable with real-time self-monitoring of the position and number of broken wire damage proposed by the present invention can perform real-time diagnosis, positioning and early warning for any one or more broken wires at any position in the cable body, providing method support for the service safety of the cable structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 Schematic diagram of the cross section of the proposed parallel steel wire intelligent cable with real-time self-monitoring of broken wire damage location and number.

[0013] Figure 2 This is a schematic diagram of the first method of making optical fiber smart yarn.

[0014] Figure 3 Schematic diagram of the second method of making optical fiber smart yarn.

[0015] Figure 4 Schematic diagram of the cross-sectional arrangement of the sawn steel wire and optical fiber smart wire in the experiment.

[0016] Figure 5 This is the axial strain data diagram of the optical fiber smart wire adjacent to the sawn steel wire under normal stress state in the test under various levels of load.

[0017] Figure 6 This is the axial strain data diagram of the adjacent optical fiber smart wires under 796.5MPa after a single wire breakage of three steel wires in the test.

[0018] Figure 7 This is the axial strain data diagram of the adjacent optical fiber smart wires under 796.5MPa after the three steel wires broke at different positions in the experiment.

[0019] Figure 8This is a graph showing the change in strain increase coefficient calculated by the numerical model after six steel wires around a certain optical fiber smart wire in the proposed parallel steel wire smart cable are broken one after another; (a)-(f) are the strain increase coefficients corresponding to the number of broken wires 1 to 6, respectively.

[0020] Fig. 9 The axial strain data of the adjacent optical fiber smart wire under 796.5MPa after two steel wires are broken at different positions in the numerical model; among them, (a) the working condition is that the two steel wire break points are 4.5m apart, (b) the working condition is that the two steel wire break points are 3m apart, (c) the working condition is that the two steel wire break points are 1.5m apart, and (d) the working condition is that the two steel wire break points are 0.5m apart.

[0021] In the figure: 1 optical fiber smart wire; 2 steel wire; 3 polyethylene sheath tube; 4 notch; 5 optical fiber; 6 fiber reinforced material composite wire; 7 ordinary steel wire to be sawed. DETAILED DESCRIPTION

[0022] In order to explain in detail and intuitively the parallel steel wire intelligent cable working method with real-time self-monitoring of the broken wire damage position and the number of wires of the invention, a specific description is given in conjunction with the accompanying drawings.

[0023] There are two types of optical fiber smart wires 1: the first type is to open a long thin groove (4) on the steel wire 2, and encapsulate the optical fiber (5) into the thin groove (4) and protect it; the other type is to process the optical fiber (5) and the high-strength fiber composite material together, and make the optical fiber (5) at the center of the formed optical fiber smart wire 1. After the parallel steel wire smart cable is pulled, all the steel wires in the cable body are deformed in coordination, and each optical fiber smart wire 1 can monitor the stress state of the other six steel wires 2 and / or optical fiber smart wires 1 adjacent to it.

[0024] The verification of the present invention can be carried out by the following test:

[0025] Step 1: Select 33 ordinary steel wires and 4 optical fiber smart steel wires, and make them into parallel steel wire smart cables with real-time self-monitoring of broken wire damage position and number according to the cable manufacturing standard steps. The effective cable length is 51m, and its cross-sectional layout is as follows: Figure 4 shown.

[0026] Step 2: calibrate the parallel steel wire intelligent cable to obtain its elastic modulus and the strain sensing coefficient of the four optical fiber intelligent wires.

[0027] Step three, the parallel steel wire intelligent cable is normally tensioned under non-destructive conditions, and the axial strain data of the four optical fiber intelligent wires under different loads are recorded and plotted.

[0028] Step 4: strip off the sheath at the 24.33m of the measurement data of the parallel steel wire intelligent cable, saw off an ordinary steel wire adjacent to a certain optical fiber intelligent wire, and then constrain the cross section with an annular clamp to keep the cross section in its original shape.

[0029] Step 5: tension the wires under the damage condition and record the strain data of the four optical fiber smart wires under different loads. Then, continue sawing at the place where the wire was sawed off in step 4. Figure 4 The remaining steel wires to be sawed off are marked, and the strain data of the four optical fiber smart wires under different loads in each working condition are recorded respectively.

[0030] Step 6: Continue to remove the sheath at the 33.85m of the parallel steel wire intelligent cable measurement data, and saw off the sheath in sequence according to steps 4 and 5. Figure 4 The wire to be sawn off is marked, and the strain data of the four optical fiber smart wires under each working condition are recorded in turn. The strain data before the wire break is subtracted from the strain data after the wire break, and a graph is drawn, which can show the damage information.

[0031] Reference Figure 5-7 It can be seen that when the wire is not broken, the strain data graph of any optical fiber smart wire of the parallel steel wire smart cable is approximately a horizontal straight line, and only fluctuates in a small range near the center value, proving that the entire cable is uniformly stressed. After the wire is broken, a triangular waveform will be generated in the stress redistribution area. As the number of broken wires increases and the position changes, multiple triangular waveforms of different sizes, either single or overlapping, will be generated. Based on the appearance and change of the waveform, the position of the peak and the increase coefficient of the peak strain, the broken wire can be identified, located and warned in real time.

[0032] Based on ANSYS software, a relevant finite element model is established to verify the accuracy of the test case data, expand more working conditions, and improve the parallel steel wire intelligent cable working method for real-time self-monitoring of the position and number of broken wire damage proposed in the present invention. Based on the numerical model, a sensitivity analysis is performed on the cable body parameters of steel wire diameter d, steel wire helix angle θ, cable body length l, sheath gripping force p, friction coefficient u between steel wires, cable force f, and number of steel wire turns n in the cable body. The results show that among these parameters, only the number of steel wire turns n in the cable body has an impact on the quantitative threshold; and there is a corresponding threshold value n = 4 (that is, the number of steel wires is greater than or equal to 37), and the impact will become very weak when this threshold is reached or exceeded, which once again proves that the strain increase coefficient of the wave peak can be used as a powerful indicator for judging the number of broken wires. Therefore, the recommended threshold range for judging the number of broken wires based on the peak strain increase coefficient is given: when the strain increase coefficient is 1.05-1.1, it is a single broken wire condition; when the strain increase coefficient is 1.1-1.15, it is a double broken wire condition; when the strain increase coefficient is 1.15-1.25, it is a three broken wire condition; when the strain increase coefficient is 1.25-1.4, it is a four broken wire condition; when the strain increase coefficient is 1.4-1.65, it is a five broken wire condition; when the strain increase coefficient is above 1.65, it is a six broken wire condition; at the same time, if Figure 6 , 7 As shown in Figure 9, the occurrence and specific location of broken wires are determined by the generation of triangular waveforms and the position of the wave crest. The mean values ​​of the strain increase coefficients of the wave crests under different numbers of broken wires also fall within Figure 8 Within the corresponding range of broken wire number conditions, the average strain increase coefficient of a single broken wire is 1.054 and 1.062, the average strain increase coefficient of double broken wires is 1.112 and 1.131, and the average strain increase coefficient of three broken wires is 1.181 and 1.219; the strain increase coefficients of broken wires at different positions are 1.059 and 1.064, 1.06 and 1.067, 1.074 and 1.077, and 1.098 and 1.099, respectively, which are also within the recommended threshold value of the strain increase coefficient under the condition of a single broken wire, and increase with the decrease of the distance between the broken wire points, gradually approaching the recommended threshold value of the strain increase coefficient under the condition of double broken wires, that is, the experiment and numerical model are in good agreement.

[0033] In summary, the parallel steel wire intelligent cable with real-time self-monitoring of the position and number of broken wire damage proposed in the present invention can locate and warn any one or more broken steel wires of the cable body in real time.

Claims

1. A parallel steel wire intelligent cable with real-time self-monitoring of the position and number of broken wires, characterized in that: The parallel steel wire intelligent cable is composed of a plurality of optical fiber intelligent wires (1) and steel wires (2) placed at the designed position of the cable body, which are slightly twisted or completely parallel to form a steel wire bundle, and a polyethylene sheath tube (3) is integrally hot-extruded on the outside of the steel wire bundle; the optical fiber intelligent wires (1) in the parallel steel wire intelligent cable are arranged in the principle that any steel wire (2) and optical fiber intelligent wire (1) in the cable body have an optical fiber intelligent wire (1) adjacent to it, but the arrangement method is not unique; Each optical fiber intelligent wire (1) can monitor the stress state of the six adjacent steel wires (2) and / or optical fiber intelligent wires (1) around it. When a plurality of optical fiber intelligent wires (1) are arranged at the designed position of the cable body, distributed stress monitoring of any steel wire (2) and optical fiber intelligent wire (1) in the parallel steel wire intelligent cable can be realized. Among them, the methods for locating broken wire damage and quantifying the number of broken wire roots under different damage conditions are as follows: Working condition where one or more steel wires (2) are damaged at the same position: when any steel wire (2) in the cable body is broken, the optical fiber smart wire (1) adjacent to the broken wire will sense the stress change, and the optical fiber smart wire (1) originally subjected to uniform stress will be subjected to greater stress. Within the stress redistribution range, the stress magnitude reaches a peak at the point where the wire is broken, and gradually decreases as the distance from the broken wire increases, thereby presenting a triangle in a certain section of the strain curve. The occurrence of the broken wire can be identified by the change in the strain curve; the specific position of the broken wire can be identified by the peak of the triangular strain curve; at the same time, when multiple steel wires (2) are broken at the same position, the peak of the triangular strain curve becomes higher, defining the maximum strain value of the triangular waveform part, that is, the peak value. The ratio of the strain value of the waveform that maintains the horizontal line outside the triangular waveform range, that is, the strain value of the stable waveform, is the strain increase coefficient. The strain increase coefficient is related to the number of broken wires. The recommended threshold range of the strain increase coefficient for judging the number of broken wires is: when the strain increase coefficient is 1.05-1.1, it is a single broken wire condition; when the strain increase coefficient is 1.1-1.15, it is a double broken wire condition; when the strain increase coefficient is 1.15-1.25, it is a three broken wire condition; when the strain increase coefficient is 1.25-1.4, it is a four broken wire condition; when the strain increase coefficient is 1.4-1.65, it is a five broken wire condition; when the strain increase coefficient is above 1.65, it is a six broken wire condition; Working condition where one or more steel wires (2) are damaged at multiple locations: If one or more wires are broken at different locations, multiple single or superimposed triangular waveforms will be generated, and the strain magnitudes at the peak values ​​will also be different; one or more steel wires (2) damaged at multiple locations are regarded as a random combination of damage conditions at the same location, and the real-time monitoring method is the same as above.

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