A kind of intelligent cable for steel strand with self-diagnosis and self-positioning

Abstract

The present invention provides a self-diagnostic and self-positioning steel strand smart cable, which is mainly made of multiple bundles of optical fiber Brillouin sensing smart steel strands that are parallel or twisted into bundles and hot-extruded with polyethylene protective sleeves. Each bundle of optical fiber Brillouin sensing smart steel strands has an optical fiber Brillouin sensing smart tendon as the central wire and a high-ductility metal foil wrapped on its surface, and then is reversely twisted with the outer wires of the steel strand in the order of stripping ordinary steel strands. The diameter of the optical fiber Brillouin sensing smart tendon is the same as the central wire of the ordinary steel strand. The self-diagnostic and self-positioning steel strand smart cable proposed by the present invention has distributed, full-scale real-time monitoring characteristics, and can realize real-time diagnosis and precise positioning of common forms of local damage occurring to any outer wire of any steel strand of any bundle of optical fiber Brillouin sensing smart steel strands in the cable, and can be widely used in the health monitoring of cable-type structures such as bridge hangers and inclined cables, and provide important support for their service safety.

Description

Technical Field

[0001] The present invention belongs to the technical field of health monitoring of cable structures, and in particular relates to a real-time diagnosis and positioning technology for damage of a steel stranded intelligent cable based on Brillouin distributed sensing. Background Art

[0002] Steel strands are widely used in structures such as prestressed concrete, bridge cables (such as cable-stayed cables of cable-stayed bridges, hangers of arch bridges, hangers and main cables of suspension bridges), anchor cables for rock and soil and slope support, and cable nets for large-span structures. Steel strands are prone to corrosion and fatigue damage due to structural characteristics, environmental corrosion, fatigue accumulation, and other reasons, and steel strands are key load-bearing components of these structures. Among the many types of steel strand diseases, broken wires, corrosion, and cable tension relaxation are three extremely common and extremely harmful diseases. Diseases should be discovered in a timely manner to prevent sudden accidents, and full-life monitoring of the status of steel strands during service is urgently needed.

[0003] With the development of fiber optic sensing technology, many scholars at home and abroad have applied fiber optic sensing technology to study the stress and strain monitoring of steel strands. Among them, the research group of Ou Jinping, one of the inventors of the present invention, has conducted a relatively systematic study in this regard. They embedded fiber gratings into fiber reinforced resin to make smart tendons, and then compounded them with steel strands to develop smart steel strands. The smart steel strand can achieve high-precision monitoring of local stress and strain at the measuring points, which is of great significance. However, the existing smart steel strands in the early stage did not pay attention to the precise positioning of the random local damage of the cable itself, such as broken wires and corrosion.

[0004] Based on the distributed measurement characteristics of optical fiber Brillouin, the present invention invents optical fiber Brillouin sensing intelligent steel strands and damage self-diagnosis and self-positioning steel strand intelligent cables composed of multiple bundles of optical fiber Brillouin sensing intelligent steel strands. The present invention realizes damage self-diagnosis and self-positioning distributed monitoring of the entire cable, solves the problem that optical fiber Bragg grating intelligent steel strands cannot be monitored at all scales, and realizes real-time diagnosis and positioning of common damages such as cable breakage, corrosion, and cable tension relaxation. The invented intelligent cables can be used in cable structures such as bridge hangers and inclined cables. Summary of the invention

[0005] The purpose of the present invention is to provide a self-diagnostic and self-positioning steel strand intelligent cable for real-time diagnosis and positioning.

[0006] The technical solution of the present invention:

[0007] A damage self-diagnostic and self-positioning steel strand intelligent cable, comprising a plurality of optical fiber Brillouin sensing intelligent steel strands 1 bundled in parallel or twisted into a bundle and hot-extruded with a polyethylene protective sleeve 2; each bundle of optical fiber Brillouin sensing intelligent steel strands 1 comprises an optical fiber Brillouin sensing intelligent tendon 3 as a central wire and 2 to 3 layers of high-ductility metal foil 4 are wound on the surface thereof, and then reversely twisted with the outer wires 5 of the steel strands in the order of stripping of ordinary steel strands, and the diameter of the optical fiber Brillouin sensing intelligent tendon 3 is the same as the middle wire of the ordinary steel strands before stripping; the optical fiber Brillouin sensing intelligent tendon 3 comprises an optical fiber 6 as an intermediate bundle and a melted high-strength fiber composite material, the optical fiber 6 is located at the center line of the formed high-strength fiber composite material, and optical fibers 6 are stripped from both ends of the optical fiber Brillouin sensing intelligent tendon 3 to serve as test jumper heads.

[0008] The self-diagnosis and self-positioning method of the damage self-diagnosis and self-positioning steel strand intelligent cable is as follows: after any bundle of optical fiber Brillouin sensing intelligent steel strands 1 is pulled, the outer wire 5 of the steel strand squeezes the central wire optical fiber Brillouin sensing intelligent tendon 3, and the central wire and the outer wire 5 of the steel strand are deformed together along the length direction of the axis of the steel strand. Therefore, when any one of the outer wires 5 of the steel strand is damaged at a certain position, the axial strain of the central wire optical fiber Brillouin sensing intelligent tendon 3 at and near the position will be significantly increased, and the optical fiber Brillouin sensing intelligent tendon 3 has the function of distributed strain measurement, and can sense the axial strain changes at or near the damaged position in real time; the present invention realizes real-time self-diagnosis and self-positioning of damage to the outer wire 5 of the steel strand based on this principle; the self-diagnosis and self-positioning steel strand intelligent cable is composed of multiple bundles of optical fiber Brillouin sensing intelligent steel strands 1, and the distributed signal of each bundle of optical fiber Brillouin sensing intelligent steel strands 1 is tested and converted into distributed strain in its axial direction, so as to realize real-time diagnosis and positioning of damage to any outer wire of any bundle of optical fiber Brillouin sensing intelligent steel strands 1 in the intelligent cable.

[0009] Beneficial effects of the present invention: The central fiber Brillouin sensing intelligent tendon 3 of each bundle of fiber optic Brillouin sensing intelligent steel strand 1 in the damage self-diagnosis and self-positioning steel strand intelligent cable proposed by the present invention has the advantages of high strength, good durability, strong anti-electromagnetic interference ability, good stability, etc., so that the damage self-diagnosis and self-positioning steel strand intelligent cable of the invention has the real-time damage diagnosis and positioning capability of full-scale for any outer wire 5 of the steel strand, can automatically and timely detect its local damage online and accurately locate it, providing active support for the service safety of the cable structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 This is a schematic cross-sectional view of the damage self-diagnosis and self-positioning steel strand smart cable proposed in the present invention.

[0011] Figure 2 Schematic diagram of a bundle of optical fiber Brillouin sensing smart steel strands.

[0012] Figure 3 A schematic diagram of the cross section of a bundle of optical fiber Brillouin sensing smart steel strands.

[0013] Figure 4 The distributed axial strain calculated by the numerical model of the fiber optic Brillouin sensing smart steel strand when it is damaged at 5m.

[0014] Figure 5 The distributed axial strain calculated by the numerical model of the fiber optic Brillouin sensing smart steel strand when it is damaged at 1.5m and 8.5m respectively.

[0015] In the figure: 1. Fiber optic Brillouin sensing smart steel strand; 2. Polyethylene protective sleeve; 3. Fiber optic Brillouin sensing smart tendon; 4. High ductility metal foil; 5. Steel strand outer wire; 6. Optical fiber. DETAILED DESCRIPTION

[0016] In order to explain the working principle and implementation method of the damage self-diagnosis and self-positioning steel strand intelligent cable of the invention in more detail and intuitively, the specific working process of the invention is now explained in conjunction with the accompanying drawings; this example does not limit the actual scope of use of the invention.

[0017] The verification of the present invention can be carried out by the following experimental methods:

[0018] Step 1, select two bundles of manufactured optical fiber Brillouin sensing intelligent steel strands 1. Select one from the six steel strand outer wires 5 of the first bundle of optical fiber Brillouin sensing intelligent steel strands, and weaken its cross section at 5m from the fixed end; select two from the six steel strand outer wires 5 of the second bundle of optical fiber Brillouin sensing intelligent steel strands, weaken the first one at 2.5m from the fixed end, and weaken the second one at 7.5m from the fixed end. The weakened side wires of the first and second bundles of optical fiber Brillouin sensing steel strands will break first during the stress process.

[0019] Step 2: The two damaged optical fiber Brillouin sensing smart steel strands 1 in step 1 and other multiple lossless optical fiber Brillouin sensing smart steel strands 1 are made into a damage self-diagnosis and self-positioning steel strand smart cable.

[0020] Step three, fix one end of the manufactured damage self-diagnostic and self-positioning steel strand intelligent cable with an anchor, and axially tension the other end until the damaged side wires of the two weakened optical fiber Brillouin sensing steel strands 1 in step one break, then stop tensioning, record the readings on the demodulator, and calculate the axial tensile strain of the undamaged optical fiber Brillouin sensing intelligent steel strand 1 and the axial tensile strain of the weakened optical fiber Brillouin sensing intelligent steel strand based on the change in the optical fiber wavelength.

[0021] The axial strain diagram of each distributed measuring point of the undamaged optical fiber Brillouin sensing intelligent steel strand 1 is approximately a horizontal line; the axial strain of each distributed measuring point of the damaged optical fiber Brillouin sensing intelligent steel strand 1 will increase at the damaged part and its surroundings, among which there is an obvious strain wave peak at the damaged part, and the strain near the damaged part gradually decreases until the strain value of the undamaged area at a certain distance from the damage is approximately on the same horizontal line. Based on this phenomenon, local damage such as broken wires and corrosion can be diagnosed and located in real time.

[0022] In addition, a finite element model of the steel strand was established based on ANSYS software to verify the feasibility of the present invention:

[0023] Step 1: Use ANSYS software to establish finite element models of three fiber optic Brillouin sensing smart steel strands 1 with a length of 10 m each; Model 1 is a numerical model of an intact fiber optic Brillouin sensing smart steel strand; Model 2 is a fiber optic Brillouin sensing smart steel strand model with a side wire having cross-sectional damage at a distance of 5 m from the fixed end; Model 3 is a fiber optic Brillouin sensing smart steel strand model with two side wires having different side wire damages, one having cross-sectional damage at a distance of 1.5 m from the fixed end, and the other having cross-sectional damage at a distance of 8.5 m from the fixed end.

[0024] In step 2, one end of each of the three models is fixed and constrained, while the other end is tensioned.

[0025] Step 3: Model 1 is intact, so its axial strain is approximately a horizontal line. The simulation results of single damage model 2 and double damage model 3 are shown in Figure 3. Figure 4 and Figure 5 As shown in the figure, the axial strain at the damaged section in model 2 increased by 24.17% compared with the normal uniform load section at the intact section far from the damaged section in the model; the axial strain at the two damaged sections at 1.5m and 8.5m away from the fixed end in model 3 increased by 24.06% and 24.74% respectively compared with the normal uniform load section at the intact section far from the damaged section in the model. Figure 4 and Figure 5 It can be seen that the simulation results of Model 2 for the single damage condition and Model 3 for the double damage condition both successfully diagnosed and located the location of local damage.

[0026] Simulation results show that the damage self-diagnosing and self-locating steel strand intelligent cable proposed in the present invention can perform real-time diagnosis and location of its local damage.

Claims

1. A self-diagnostic and self-positioning steel strand smart cable, characterized in that: The damage self-diagnosis and self-positioning steel strand intelligent cable is mainly composed of a plurality of optical fiber Brillouin sensing intelligent steel strands (1) bundled in parallel or twisted and hot-extruded with a polyethylene protective sleeve (2); Each bundle of optical fiber Brillouin sensing intelligent steel strand (1) is composed of an optical fiber Brillouin sensing intelligent tendon (3) as a central wire and 2 to 3 layers of high-ductility metal foil (4) are wound around the surface of the central wire, and then reversely twisted with the outer wire of the steel strand (5) in the order of stripping the ordinary steel strand. The diameter of the optical fiber Brillouin sensing intelligent tendon (3) is the same as the central wire of the ordinary steel strand before stripping. The optical fiber Brillouin sensing smart rib (3) is formed by integrating an optical fiber (6) as an intermediate bundle with a melted high-strength fiber composite material, the optical fiber (6) is located at the center line of the formed high-strength fiber composite material, and optical fibers (6) are stripped from both ends of the optical fiber Brillouin sensing smart rib (3) to serve as test jumper heads; an optical fiber (6) is arranged in the optical fiber Brillouin sensing smart rib (3); When any bundle of optical fiber Brillouin sensing intelligent steel strands (1) is pulled, the outer wire (5) of the steel strand squeezes the central wire optical fiber Brillouin sensing intelligent tendon (3), and the central wire and the outer wire deform together along the length direction of the steel strand axis. In the lossless state, the strain curve monitored by the optical fiber Brillouin sensing intelligent tendon (3) is approximately a horizontal line. When any outer wire of the steel strand outer wire (5) is damaged at a certain position, the axial strain of the central wire optical fiber Brillouin sensing intelligent tendon (3) at and near the position will increase significantly, with an obvious peak, and gradually decrease as it moves away from the broken wire position, and return to an approximate horizontal line. The strain at the peak increases by 24.17%, 24.06% and 24.74% compared with the normal uniformly stressed section. The optical fiber Brillouin sensing intelligent tendon (3) has a distributed strain measurement function and can sense the axial strain changes at or near the damaged position in real time. Based on this principle, real-time self-diagnosis and self-positioning of steel strand outer wire damage can be achieved. The damage self-diagnosing and self-positioning steel strand smart cable is composed of a plurality of optical fiber Brillouin sensing smart steel strands (1). The distributed signal of each optical fiber Brillouin sensing smart steel strand (1) is tested and converted into distributed strain in its axial direction, thereby achieving real-time diagnosis and positioning of damage to any outer wire of any optical fiber Brillouin sensing smart steel strand (1) in the smart cable.

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