Carbon fiber composite mooring line system and method for offshore floating structures

Abstract

The application discloses a kind of carbon fiber composite combined mooring cable system and self-monitoring method for offshore floating structure.The mooring cable system includes three sections of different materials, which are first mooring cable located in upper section, carbon fiber composite mooring cable located in middle section and second mooring cable located in lower section.The sections of cable system are connected by mechanical connection structure.The first mooring cable is guided to floating platform through fairlead and wound on winch.Tension meter is installed between first mooring cable and carbon fiber composite mooring cable.Displacement meter is installed in anchor of both ends of carbon fiber composite mooring cable.Stress meter is installed in second mooring cable.The end of second mooring cable is connected to gravity anchor foundation.The application combines the application of carbon fiber composite material in mooring cable of offshore engineering with advanced sensing technology such as optical fiber sensing, realizes the improvement of intelligent level of cable, and ensures the reliability of cable system and the accuracy of damage detection.

Description

Technical Field

[0001] This invention relates to the field of marine engineering technology, and in particular to a carbon fiber composite mooring cable system and method for offshore floating structures. Background Technology

[0002] Floating offshore structures, such as floating wind power platforms and floating docks, typically rely on mooring systems to maintain stability and safety. Mooring cables, as a key component of these structures, bear the important responsibility of supporting and securing them. Traditional mooring cables are mostly made of metal or synthetic fiber materials, such as steel anchor chains, steel wire ropes, and polyethylene cables. However, with the advancement of the construction of large deep-sea platforms exceeding 1,000 tons, traditional metal mooring cables will become unusable, and the high creep of synthetic fiber cables also limits their long-term durability. Therefore, it is necessary to apply new materials to mooring cables.

[0003] Carbon fiber composites possess advantages such as light weight, good corrosion resistance, high strength, and high stiffness. With improvements in performance and reductions in production costs, their application in marine engineering is gradually increasing, making them an ideal choice for mooring cable materials. During actual service, the area where mooring cables meet the air and seawater (splash zone) experiences the most severe corrosion and aging due to repeated seawater erosion. Compared to traditional mooring cable materials, carbon fiber composites, with their superior performance, are the best choice for the splash zone. Simultaneously, due to the requirements of floating platforms for the coiling and winding of mooring cables, and the weight requirements of seabed anchoring, traditional polymer synthetic fiber ropes and steel anchor chains can also be used. Combining carbon fiber composites and traditional mooring cables in suitable sections to form a new mooring cable system fully leverages the performance advantages of each material. With the advancement of major marine engineering projects, this new mooring cable system will face significant application needs. The mechanical properties of carbon fiber mooring cable systems are completely different from traditional mooring cables, requiring a redesign of the overall structure, which presents greater complexity and challenges. To meet the practical needs of carbon fiber composite mooring cables, a novel mooring cable with lightweight, long lifespan, and low creep was proposed through a special design of the overall structure of the carbon fiber composite mooring cable system.

[0004] Meanwhile, our understanding of the service performance of this novel carbon fiber composite mooring cable is still in its infancy, and relevant non-destructive testing and monitoring methods are needed to evaluate its performance in the marine environment. Currently, the following non-destructive testing techniques are available for cable structures:

[0005] Visual inspection relies on human observation, while manual inspection assesses the health of a structure through tapping or auditory observation. However, these methods are susceptible to subjective judgment and operator experience, leading to inconsistent results. They cannot provide precise quantitative data, offering only qualitative observations, and are limited in their effectiveness in detecting hidden or internal problems, such as deep cracks or concealed corrosion.

[0006] Structural dynamic response monitoring utilizes accelerometers or sensors to measure the vibration response of a structure under external excitation. While this method can reflect the overall vibration characteristics of the structure, it requires complex mathematical models and data analysis techniques to infer the structural health status. The complexity of data analysis and the accuracy of the model are its main challenges, and it is difficult to provide immediate feedback.

[0007] Strain measurement technology uses sensors such as strain gauges or strain meters mounted on structural surfaces to measure strain states under various operating conditions. However, once the mounting location of strain gauges is determined, it is difficult to change and is significantly affected by complex environmental conditions, such as high temperatures or the presence of chemicals. Furthermore, they can only measure surface strain, limiting their ability to detect deep or hidden structural problems.

[0008] Acoustic emission testing (AE) relies on monitoring the sounds produced by a structure under loading or stress to identify internal defects or deformations. However, this method is sensitive to environmental noise and interference, which can lead to false alarms or misdiagnosis. Its location accuracy is limited, typically only able to roughly pinpoint the location of the problem, and it struggles to provide centimeter-level precision, especially for complex or multi-layered structures.

[0009] Electromagnetic detection technology utilizes electromagnetic waves, such as ultrasound or electromagnetic induction, to detect defects or changes in material state within a structure. However, its application is limited by the structural materials and geometry, and it requires materials with specific electromagnetic responsiveness. Furthermore, the penetration and propagation capabilities of electromagnetic waves may be limited, making it difficult to completely detect all parts of complex structures.

[0010] While the aforementioned non-destructive testing and monitoring methods still hold value in certain scenarios, their limitations make them unsuitable for the inspection and monitoring of carbon fiber composite mooring cables in marine environments. In contrast, fiber optic sensing technology offers multiple advantages in the non-destructive testing of carbon fiber mooring cables. First, it can monitor key parameters such as tension and strain of the mooring cable in real time, and possesses high sensitivity, capable of detecting minute changes and fluctuations, including subtle alterations in structural deformation and stress distribution. This high sensitivity allows fiber optic sensing technology to detect potential fatigue cracks, damage, or other structural problems at an early stage, facilitating early detection of potential structural issues. Furthermore, fiber optic sensing technology offers remote monitoring capabilities; sensors can be distributed over long distances along the entire length of the mooring cable, enabling remote data transmission and monitoring. This remote monitoring capability not only reduces direct operator intervention but also lowers operational risks, especially in harsh or inaccessible marine environments.

[0011] Overall, fiber optic sensing technology demonstrates broad application prospects and significant technical advantages in the non-destructive testing of carbon fiber mooring cables. Its high flexibility and adaptability allow for customization and adjustment for different types and sizes of carbon fiber mooring cables, meeting the practical needs of complex and ever-changing marine environments. By monitoring key parameters of the mooring cable in real time, such as tension and strain, fiber optic sensors can provide a continuous data stream, helping maintenance personnel to identify potential structural problems early, thereby reducing the risk of emergencies and optimizing maintenance plans.

[0012] Currently, there are no specific non-destructive testing and monitoring methods for carbon fiber composite mooring cables. Furthermore, comprehensively monitoring the strain, stress, and anchorage slippage of mooring cables presents certain technical challenges. Given the practical need for carbon fiber composite mooring cables, this paper proposes a comprehensive monitoring system based on advanced sensing technology and structural system design to comprehensively monitor the stress, strain, and anchorage slippage of carbon fiber composite mooring cables under service conditions, assess their mechanical and anchorage performance, and thus test and verify the applicability of this novel mooring method. Summary of the Invention

[0013] To address the aforementioned technical problems, this invention proposes a carbon fiber mooring cable system for offshore floating structures. This cable system combines fiber optic sensing technology to monitor the cable strain in real time with vibrating wire stress gauge anchor chain links to monitor the stress of the anchor chain segments in real time, thereby achieving non-destructive testing of damage to the carbon fiber mooring cable system.

[0014] To achieve the above technical objectives, the present invention employs the following technical means:

[0015] A carbon fiber composite mooring cable system for offshore floating structures is disclosed. This system comprises three sections of mooring cables made of different materials: a first mooring cable in the upper section, a carbon fiber composite mooring cable in the middle section, and a second mooring cable in the lower section. The sections are connected by a mechanical connection structure.

[0016] The first mooring cable is guided onto the floating platform via a guide cable and wound onto the winch. A tension gauge is installed between the first mooring cable and the carbon fiber composite mooring cable. Displacement gauges are installed in the anchors at both ends of the carbon fiber composite mooring cable. The second mooring cable is equipped with a stress gauge. The end of the second mooring cable is connected to a gravity anchor foundation.

[0017] The data lines of the displacement gauge and the stress gauge extend naturally upwards to the platform;

[0018] In the carbon fiber composite mooring cable, some carbon fiber composite rods are embedded with optical fibers, forming intelligent carbon fiber composite rods. The optical fibers and tension meter data lines are led out from the end of the carbon fiber composite mooring cable and extended along the first mooring cable to the surface. The ends of the optical fibers are connected to relevant demodulation devices, and the ends of the tension meter data lines are connected to relevant data acquisition devices.

[0019] The carbon fiber composite mooring cable includes: carbon fiber composite rods, high-strength material strips, and protective sleeves. Multiple carbon fiber composite rods are arranged in parallel and twisted at a slight angle. The carbon fiber composite rod group is wrapped with high-strength material strips, and two layers of protective sleeves are added to protect the internal structure. The optical fiber is implanted in some of the carbon fiber composite rods.

[0020] The number of carbon fiber composite rods with embedded optical fibers in the carbon fiber composite mooring cable shall not be less than one-third of the total number of carbon fiber composite rods.

[0021] The first mooring cable is a polymer synthetic fiber rope.

[0022] The upper end of the carbon fiber composite mooring cable is anchored into the first anchor. The outer cylindrical surface of the first anchor is machined with external threads that are screwed into the internal threads of the inner hole of the first lifting lug. There is a space between the bottom plate of the first anchor and the bottom plate of the first lifting lug. The carbon fiber composite rod of the carbon fiber composite mooring cable passes through the bottom plate of the first anchor. A first displacement gauge is installed on several carbon fiber composite rods and connected to the first positioning screw. The optical fiber embedded in the carbon fiber composite rod is led out from the end of the carbon fiber composite rod and connected to the armored optical fiber in the space between the bottom plate of the anchor and the bottom plate of the first lifting lug. One armored optical fiber connects multiple fiber cores. A hole is opened on the bottom plate of the first lifting lug to lead the armored optical fiber in the bottom plate of the first lifting lug out of the first lifting lug, and waterproof glue is injected into the hole.

[0023] The armored optical fiber and tension meter data line are arranged in parallel and protected by a sleeve throughout. They are attached to the polymer synthetic fiber cable and led up to the floating platform together.

[0024] The upper end of the first lifting lug is connected to the insertion end of the first shackle. The upper part of the first shackle is connected to the second shackle. The second shackle is connected to the tension gauge. The upper end of the tension gauge is connected to the third shackle. The upper part of the third shackle is connected to the eyelet and the polymer synthetic fiber cable.

[0025] The second mooring cable is a steel anchor chain. The lower end of the carbon fiber composite mooring cable is anchored into the second anchor. The outer cylindrical surface of the second anchor is machined with external threads, which are screwed into the internal threads of the inner hole of the second lifting lug. There is a space between the bottom plate of the second anchor and the bottom plate of the second lifting lug. The carbon fiber composite rod of the carbon fiber composite mooring cable passes through the bottom plate of the second anchor. Several carbon fiber composite rods are selected from the carbon fiber composite rods that extend out of the bottom plate of the anchor. The center point of several carbon fiber composite rods is equidistant from the center of the anchor, and the center points of several carbon fiber composite rods are arranged in a centrally symmetrical manner with respect to the center of the anchor.

[0026] In a plurality of the carbon fiber composite rods, the end of each carbon fiber composite rod is connected to a probe of one of the displacement gauges via a connecting cap;

[0027] Two connecting metal plates are symmetrically clamped at one end on both sides of the displacement gauge and fixedly connected to the displacement gauge by the first fixing bolt; the other end is symmetrically clamped at both sides of the positioning screw and fixedly connected to the positioning screw by the second fixing bolt.

[0028] When the carbon fiber composite rod in the anchor slips relative to the anchor, the connecting cap moves axially with the carbon fiber composite rod, causing the probe of the displacement gauge to move axially. The average value of the displacement measured by several displacement gauges is the anchor slip.

[0029] The lower end of the second lifting lug is connected to the insertion end of the fourth shackle, and the lower end of the fourth shackle is connected to the steel anchor chain segment. The steel anchor chain segment is equipped with an anchor chain ring, and two stress gauges are welded on the anchor ring. The end of the steel anchor chain segment is fixed on a gravity anchoring foundation. The foundation adopts a square frustum shape with the bottom recessed inward.

[0030] Select three carbon fiber composite rods from the bottom plate of the anchorage. The center points of the three carbon fiber composite rods are equidistant from the center of the anchorage, and the lines connecting the center points of the three carbon fiber composite rods to the center of the anchorage form a 120° angle with each other.

[0031] The stress gauge is a vibrating wire stress gauge. One of the anchor rings in the anchor chain is cut into two half anchor rings. The vibrating wire stress gauge is connected between the two half anchor rings. The data line of the vibrating wire stress gauge is led outward from the adapter and is protected by a protective sleeve.

[0032] The displacement gauge is an underwater miniature displacement gauge.

[0033] This invention further discloses a self-monitoring method for the carbon fiber composite mooring cable system used in offshore floating structures.

[0034] Real-time strain data of the internal intelligent carbon fiber composite rod is obtained by using optical fibers embedded in the carbon fiber composite mooring cable.

[0035] By measuring stress data with a tension meter, the distribution of strain difference Δε along the cable length direction under a certain stress difference Δσ is obtained. For an intact composite rod, the distribution of strain difference Δε is a horizontal straight line. If a jump occurs in the distribution diagram, the jump section is the damaged section.

[0036] The stiffness distribution of the composite rod is calculated by E=Δσ / Δε. The damage stiffness value Cd of the damaged section is equal to the initial stiffness E0 minus the stiffness value Ed of the damaged section, that is, Cd=E0-Ed.

[0037] Finally, the location and size of the damage were determined based on the anchorage slippage detected by the displacement gauge inside the carbon fiber composite mooring cable, and the overall damage status of the carbon fiber composite mooring cable was judged.

[0038] The technical solution of the present invention has the following advantages compared with the prior art:

[0039] The present invention discloses a carbon fiber composite mooring cable system for offshore floating structures. This innovatively applies carbon fiber composite materials to mooring cables, and cleverly combines and connects them with other traditional mooring cable materials. Furthermore, the upper section is equipped with an anchor tension gauge, the anchor contains an underwater micro displacement gauge, and the anchor chain section is equipped with a vibrating wire stress gauge to monitor the tension, strain, and damage of the cable in real time. While improving the strength and corrosion resistance of the mooring cable, it also fully utilizes the role and advantages of traditional mooring cable materials, making the overall structure of the new mooring cable system more reliable.

[0040] The present invention discloses a carbon fiber composite mooring cable system for offshore floating structures, which combines carbon fiber composite materials with advanced fiber optic sensing technology. By analyzing and processing measured strain data of the fiber optic cables embedded in the carbon fiber composite mooring cables, damage to the carbon fiber composite mooring cables can be detected and monitored efficiently and accurately. Real-time data of the cables are obtained through tension gauges, displacement gauges, and vibrating wire stress gauges, giving the mooring cable system real-time monitoring capabilities and improving the intelligence level of the mooring cable system. Attached Figure Description

[0041] Figure 1 This is a schematic diagram of the overall structure of the intelligent carbon fiber composite mooring cable system of the present invention;

[0042] Among them, 1: floating platform main control room, 2: winch, 3: data line and transmission line, 4: cable rack, 5: guide wheel, 6: polymer synthetic fiber cable, 7: tension meter data line, 8: displacement meter transmission line, 9: tension meter, 10: armored optical fiber and tension meter data line, 11-1: first lifting lug, 11-2: second lifting lug, 12: anchor, 13: stress meter transmission line, 14: sling for fixing transmission line, 15: carbon fiber composite mooring cable, 16: vibrating wire stress meter, 17: steel anchor chain, 18: gravity anchor.

[0043] Figure 2 These are three views of the connection area between the carbon fiber composite mooring cable and the polymer synthetic fiber cable of the present invention;

[0044] Among them, 19-1: first shackle, 19-2: second shackle, 19-3: third shackle, 20: heart-shaped eyelet;

[0045] Figure 3 This is a longitudinal section view of the anchorage of the present invention;

[0046] Among them, 12-1: displacement gauge data cable, 12-2: displacement gauge, 12-3: connecting cap, 12-4: connecting metal plate, 12-5: anchor bottom plate, 12-6: positioning screw rod, 12-7: screw divider plate, 12-8: anchor cup, 12-9: nut, 12-10: second fixing bolt for metal plate, 12-11: bolt hole, 12-12: epoxy iron sand filling, 12-13: bottom plate carbon fiber composite rod opening; 12-14: first fixing bolt for metal plate.

[0047] Figure 4 This is a view of the anchor end face of the present invention;

[0048] Figure 5 This is a schematic cross-sectional view of the fiber embedded in the carbon fiber composite rod of the present invention.

[0049] Among them, 15-1: outer sheath, 15-2: inner sheath, 15-3: high-strength material strip, 15-4: carbon fiber composite rod without embedded optical fiber, and 15-5: intelligent carbon fiber composite rod.

[0050] Figure 6 This is a schematic diagram of the end face of the lifting lugs leading out of the upper and lower ends of the carbon fiber cable segment and the displacement gauge data line of the present invention.

[0051] Among them, 11-1: first lifting lug, 11-1-1: armored optical fiber outlet, 11-3-1: first lifting lug base plate, 11-1-2: displacement gauge data line outlet;

[0052] 11-2: Second lifting lug; 11-3-2: Base plate of the second lifting lug;

[0053] Figure 7This is a schematic diagram of the armored optical fiber and tension meter data line arrangement of the present invention;

[0054] Among them, 6-2: sheath, 15-5-1: armored optical fiber, 15-5-2: optical fiber core, 6-1: flexible material filling;

[0055] Figure 8 This is a schematic diagram of the customized vibrating wire stress gauge anchor ring of the present invention;

[0056] Among them, 16-1: half anchor ring, 16-2: vibrating wire stress gauge, 16-3: stress gauge data cable adapter, 16-4: data cable with protective sleeve;

[0057] Figure 9 This is a schematic diagram of the connection area between the carbon fiber composite mooring cable and the steel anchor chain of the present invention;

[0058] Among them, 11-2: the second lifting lug, 19-4: the fourth shackle;

[0059] Figure 10 This is a graph showing the measured strain difference distribution data of the optical fiber composite rod according to the present invention;

[0060] Figure 11 This is a graph showing the measured stiffness distribution of the optical fiber composite rod according to the present invention. Detailed Implementation

[0061] The present invention will be further described below with reference to the accompanying drawings and specific embodiments, so that those skilled in the art can better understand and implement the present invention. However, the embodiments described are not intended to limit the present invention.

[0062] This invention, based on the National Key Research and Development Program project "Carbon Fiber Composite Mooring Cables and Key Application Technologies for Major Marine Structures" (2023YFB3711500), provides a carbon fiber composite mooring cable system and method for marine floating structures.

[0063] Reference Figure 1 As shown, the present invention provides an intelligent carbon fiber composite mooring cable system. The overall cable system consists of three mooring cables made of different materials: the upper section is a polymer synthetic fiber cable 6, the middle section is a carbon fiber composite cable 15 with embedded optical fibers, and the lower section is a steel anchor chain 17 with a vibrating wire stress gauge 16.

[0064] The cable system is connected to its various sections via mechanical connectors and mechanical connectors with tension detection capabilities. A ship anchor chain tension gauge 9 is installed between the carbon fiber composite mooring cable 15 and the polymer synthetic fiber cable 6. Displacement gauges 12-2 are installed between the upper first anchor, the lower second anchor, and the first and second lifting lugs, respectively.

[0065] The lower section of the steel anchor chain 17 is connected to the gravity-type concrete anchor foundation 18 at its end.

[0066] The optical fiber embedded in the carbon fiber composite mooring cable is led out from the end of the lug and, together with the tension meter data line 7, is indexed onto the floating platform along the mooring cable. The end of the armored optical fiber 15-5-1 is connected to the relevant demodulation device, and the end of the tension meter data line 7 is connected to the relevant acquisition device.

[0067] Specifically, the carbon fiber composite mooring cable 15 is anchored into the anchor 12 at both ends. The external thread on the outer cylindrical surface of the anchor 12 is matched with the internal thread in the inner hole of the lug 11, that is, the anchor 12 and the lug 11 are connected by threads.

[0068] The carbon fiber composite mooring cable 15 and the steel anchor chain 17 are connected by mechanical fasteners, such as... Figure 9 As shown. The customized anchor chain link consists of two cut-off half anchor rings 16-1 and a vibrating wire stress gauge 16-2 connecting the two half anchor rings. The stress gauge is led outward from the stress gauge data cable adapter 16-3 and is equipped with a protective sleeve 16-4, as shown. Figure 8 As shown.

[0069] like Figure 9 As shown, a hole is made on the second lifting lug 11-2, one end of the fourth shackle 19-4 is inserted into the hole of the second lifting lug 11-2, and the other end of the fourth shackle 19-4 is directly inserted into the anchor chain ring of the steel anchor chain 17.

[0070] like Figure 2 As shown, the carbon fiber composite mooring cable 15 and the polymer synthetic fiber cable 6 are connected by a mechanical connector with tension detection. The first lug 11-1 has a hole, and one end of the first shackle 19-1 is inserted into the hole of the first lug 11-1. The upper part of the first shackle 19-1 is connected to the second shackle 19-2. The second shackle 19-2 is connected to the tension gauge 9. The upper end of the tension gauge 9 is connected to a third shackle 19-3. The upper part of the third shackle 19-3 is connected to the eyelet 20. The polymer synthetic fiber cable 6 is tied to the eyelet 20.

[0071] Select several carbon fiber composite rods from the carbon fiber composite rods extending from the bottom plate of the anchor. The center points of these carbon fiber composite rods are equidistant from the center of the anchor, and the center points of these carbon fiber composite rods are arranged in a centrally symmetrical manner with respect to the center of the anchor.

[0072] Among the selected carbon fiber composite rods, the end of each carbon fiber composite rod is connected to a probe of the displacement gauge via a connecting cap 12-3.

[0073] Two connecting metal plates 12-4 are symmetrically clamped at one end on both sides of the displacement gauge and fixedly connected to the displacement gauge by the first fixing bolt. The other end is symmetrically clamped at both sides of the positioning screw 12-6 and fixedly connected to the positioning screw 12-6 by the second fixing bolt.

[0074] When the carbon fiber composite rod in the anchor slips relative to the anchor, the connecting cap 12-3 moves axially along with the carbon fiber composite rod, causing the probe of the displacement gauge 12-2 to move axially, converting the anchor slippage into the displacement value measured by the displacement gauge 12-2. The average value of the real-time displacement measurements by the three displacement gauges is the anchor slippage amount.

[0075] Specifically, the center points of the three carbon fiber composite rods that install the connecting cap 12-3 should be approximately equal to the center of the anchor 12, and the lines connecting the center points of the three rods to the center of the anchor 12 should form a 120° angle with each other. Figure 4 As shown.

[0076] Specifically, the optical fiber embedded in the carbon fiber composite mooring cable 15 extends from the end of the composite rod and connects to the armored optical fiber 15-5-1 in the space between the end of the anchor 12 and the bottom plate of the lifting lug. One armored optical fiber 15-5-1 can connect to multiple optical fiber cores 15-5-2. At the same time, a displacement gauge 12-2 is installed between the threaded rod 12-6 on the anchor and the carbon fiber composite rod, and is connected by a metal plate 12-4 and a bolt 12-14 to bundle the displacement gauge data cable together.

[0077] The first lifting lug base plate has a hole at 11-3-1, as follows Figure 6 As shown, the armored optical fiber 15-5-1 and the bundled displacement gauge data line 8 inside the first lifting lug 11-1 are led out from the armored optical fiber outlet 11-1-1 and the displacement gauge data line outlet 11-1-2, respectively, and waterproof glue is injected into the hole to prevent water from entering the first lifting lug 11-1 and the first anchor.

[0078] Specifically, the armored optical fiber 15-5-1 and the tension gauge data line 7 are arranged in parallel and are fully wrapped and protected by the sleeve 6-2, such as... Figure 7 As shown.

[0079] Specifically, the carbon fiber composite mooring cable 15 consists of a standard carbon fiber composite rod 15-4, a smart carbon fiber composite rod 15-5, a high-strength material strip 15-3, an inner sheath 15-2, and an outer sheath 15-1, as follows: Figure 5As shown, multiple ordinary carbon fiber composite rods 15-4 and intelligent carbon fiber composite rods 15-5 are arranged in parallel and twisted at a slight angle. The carbon fiber composite rod assembly is wrapped with a high-strength material strip 15-3, and further protected by two layers of sheaths: an inner sheath 15-2 and an outer sheath 15-1. Distributed fiber optic sensors are embedded within the intelligent carbon fiber composite rods 15-5, with optical fibers extending from the ends of the composite rods. These embedded fiber optic sensors can be used in conjunction with demodulation equipment to acquire cable strain data.

[0080] Specifically, the number of intelligent carbon fiber composite rods 15-5 with embedded optical fibers in the carbon fiber composite mooring cable 15 should not be less than one-third of the total number of composite rods.

[0081] This invention provides a non-destructive testing method for a carbon fiber mooring cable system for offshore floating structures. Real-time strain data of the intelligent carbon fiber composite rod 15-5 within the carbon fiber composite mooring cable 15 is acquired via optical fibers embedded in the cable. Combined with measured stress data from a tension gauge 9, the distribution of strain difference Δε along the cable length under a given stress difference Δσ is obtained. For an intact composite rod, the strain difference Δε distribution is a horizontal straight line. If a jump occurs in the distribution diagram, the jump segment is the damaged segment. The stiffness distribution of the composite rod can be calculated using E=Δσ / Δε. The damage stiffness value Cd of the damaged segment is equal to the initial stiffness E0 minus the stiffness value Ed of the damaged segment, i.e., Cd=E0-Ed. Finally, based on the location and magnitude of damage to the intelligent carbon fiber composite rod 15-5 within the cable, the overall damage state of the carbon fiber composite mooring cable 15 is determined.

[0082] The following detailed description of the non-destructive testing method for the carbon fiber mooring cable system of the marine floating structure of the present invention, with reference to specific embodiments, is provided in detail.

[0083] Example 1

[0084] A smart carbon fiber composite mooring cable system was used on a floating structure in a certain sea area, such as... Figure 1 As shown, the upper section of the polymer synthetic fiber cable 6 extends underwater from the upper floating structure, and the lower end's eyelet 20 is connected to the first lifting lug 11-1 via a tension-detecting mechanical connector. The first lifting lug 11-1 is connected to the first anchorage via threads. One end of the carbon fiber composite cable 15 is anchored into the first anchorage, and the other end is anchored into the second anchorage. The second anchorage is connected to the second lifting lug 11-2 via threads. The second lifting lug 11-2 is connected to the anchor chain 17 with a vibrating wire strain gauge 16 via a mechanical connector. The anchor chain 17 is connected to the gravity anchoring foundation 18. This completes the assembly of the entire mooring system.

[0085] Among them, such as Figure 2As shown, in the mechanical connector with tension detection, the tension gauge 9 is connected to shackles at both ends. One end of the tension gauge 9 is sleeved on the eyelet ring 20 via the third shackle 19-3, and the other end is connected to the first shackle 19-1 via the second shackle 19-2. The first shackle 19-1 is then sleeved in the hole of the first lifting lug 11-1. Figure 9 As shown, in the mechanical connector connected to the lower anchor chain, the rear end of the second anchor is screwed onto the second lifting lug 11-2, the fourth shackle 19-4 is inserted into the hole of the second lifting lug 11-2, and then the fourth shackle is inserted onto an anchor chain ring at the end of the steel anchor chain 17.

[0086] Example 2

[0087] Seven optical fibers are embedded in the carbon fiber composite mooring cable 15 and led out from the end of the composite rod. Four armored optical fibers 15-5-1 are connected in the gap between the end of the first anchor and the bottom plate of the first lifting lug. One optical fiber leading out from the composite rod can be connected to one fiber core 15-5-2 of the armored optical fiber 15-5-1, using a total of two armored optical fibers 15-5-1. For example... Figure 6 As shown, two armored optical fibers 15-5-1 emerge from the armored optical fiber outlet 11-1-1 on the first lifting lug base plate 11-3-1, and the displacement gauge data line 12-1 emerges from the displacement gauge data line outlet 11-1-2. Waterproof glue is then injected into the hole to prevent water from entering the first lifting lug 11-1 and the first anchor.

[0088] The armored optical fiber 15-5-1 and the tension gauge data line 7, extending from the first lifting lug 11-1, are arranged in parallel and led up to the floating platform along the polymer synthetic fiber cable 6. The armored optical fiber 15-5-1 and the tension gauge data line 7 are together wrapped and protected by a sleeve 6-2. Figure 7 As shown. After the armored fiber optic cable 15-5-1 and the tension meter data cable 7 are led to the platform, the end of the armored fiber optic cable 15-5-1 is connected to the relevant demodulator device, and the end of the tension meter data cable 7 is connected to the relevant data acquisition device.

[0089] Example 3

[0090] Select three carbon fiber composite rods extending from the bottom plate of the anchorage. The center points of the three carbon fiber composite rods are equidistant from the center of the anchorage 12, and the lines connecting the center points of the three rods to the center of the anchorage 12 form a 120° angle with each other.

[0091] Of the three carbon fiber composite rods, the end of each carbon fiber composite rod is connected to a probe of one of the displacement gauges via a connecting cap 12-3.

[0092] Two connecting metal plates 12-4 are symmetrically clamped at one end on both sides of the displacement gauge and fixedly connected to the displacement gauge by the first fixing bolt 12-14. The other end is symmetrically clamped at both sides of the positioning screw 12-6 and fixedly connected to the positioning screw 12-6 by the second fixing bolt 12-10.

[0093] When the carbon fiber composite rod in the anchor slips relative to the anchor, the connecting cap 12-3 moves axially with the carbon fiber composite rod, causing the probe of the displacement gauge to move axially. The average value of the displacement measured by the three displacement gauges is the anchor slip.

[0094] Example 4

[0095] like Figure 9 As shown, the carbon fiber composite mooring cable 15 and the steel anchor chain 17 are connected by a mechanical connector, and the stress gauge is a vibrating wire stress gauge.

[0096] like Figure 8 As shown, one of the anchor chain rings is cut into two half anchor rings 16-1. The vibrating wire stress gauge 16-2 is connected between the two half anchor rings 16-1. The data line of the vibrating wire stress gauge 16-2 is led outward from the adapter and is provided with a protective sleeve 16-4.

[0097] Example 5

[0098] The carbon fiber composite cable 15 is composed of 37 parallel carbon fiber composite rods twisted together at a slight angle, such as... Figure 4 As shown. The elastic modulus of the carbon fiber composite rod is E0 = 180 GPa. The carbon fiber composite rod assembly is wrapped with a high-strength material strip 15-3, and an inner sheath 15-2 and an outer sheath 15-1 are added to protect the internal structure. Seven of the carbon fiber composite rods have distributed fiber optic sensors embedded in them, forming smart carbon fiber composite rods #1-#7 15-5. The remaining 29 carbon fiber composite rods are ordinary carbon fiber composite rods 15-4.

[0099] Real-time strain data is acquired through optical fibers embedded in the #1-#7 intelligent carbon fiber composite rods 15-5. By combining this with measured stress data from tension gauge 9, the distribution of strain difference Δε along the length direction within the 0-500mm length of the #1-#7 intelligent carbon fiber composite rods 15-5 is obtained under the condition of Δσ=100MPa. Figure 10 As shown in the diagram, the abrupt jumps in the strain difference Δε distribution map indicate the damaged sections. Damage is located based on the location of the abrupt change in strain difference. The locations of the damaged sections in the #1-#7 intelligent carbon fiber composite rod 15-5 are shown in Table 1.

[0100] Table 1. Location of damaged sections in intelligent carbon fiber composite rods (unit: mm)

[0101] ; The stiffness distribution of the #1-#7 intelligent carbon fiber composite rod 15-5 was calculated using E=Δσ / Δε, where Δσ=100MPa. The stiffness distribution along the length direction within the 0-500mm length range of the #1-#7 intelligent carbon fiber composite rod 15-5 is as follows: Figure 11 As shown. Damage stiffness value C of the damaged section. d Equals the initial stiffness E0 minus the stiffness value E of the damaged section. d C d =E0-E d The damage stiffness values ​​of the 15-5 damaged section of the #1-#7 intelligent carbon fiber composite rod are shown in Table 2.

[0102] Table 2 Damage Stiffness of Damaged Sections in Intelligent Carbon Fiber Composite Rods (Unit: GPa)

[0103] ; Based on the damage stiffness values ​​of the #1-#7 intelligent carbon fiber composite rods 15-5, it can be determined that the carbon fiber composite mooring cable 15 is in the range of 0-500mm, and the area where the #2-#5 intelligent carbon fiber composite rods 15-5 are located is more severely damaged.

[0104] This invention innovatively applies carbon fiber composite materials to mooring cables, while cleverly combining and connecting them with other traditional mooring cable materials. This fully leverages the superior properties of each material segment, resulting in a more reliable overall structure for the novel mooring cable system. Furthermore, tension gauges are installed in the upper section, fiber optic sensors are embedded in the carbon fiber composite rods, underwater miniature displacement gauges are installed in the anchorage, and vibrating wire stress gauges are installed in the anchor chain segment to monitor parameters such as cable tension, strain, and anchorage slippage in real time. This endows the mooring cable system with the ability to monitor damage in real time, improving the system's intelligence level.

[0105] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A carbon fiber composite composite mooring cable system for offshore floating structures, characterized in that, The mooring cable system consists of three sections of mooring cables made of different materials: a first mooring cable in the upper section, a carbon fiber composite mooring cable in the middle section, and a second mooring cable in the lower section. The sections of the cable system are connected by a mechanical connection structure. The first mooring cable is guided onto the floating platform via a guide cable and wound onto the winch. A tension gauge is installed between the first mooring cable and the carbon fiber composite mooring cable. Displacement gauges are installed in the anchors at both ends of the carbon fiber composite mooring cable. The second mooring cable is equipped with a stress gauge. The end of the second mooring cable is connected to a gravity anchor foundation. The data lines of the displacement gauge and the stress gauge extend naturally upwards to the platform; In the carbon fiber composite mooring cable, some carbon fiber composite rods are embedded with optical fibers, forming intelligent carbon fiber composite rods. The optical fibers and the tension meter data line are led out from the end of the carbon fiber composite mooring cable and guided along the first mooring cable to the surface above the water. The end of the optical fiber is connected to the relevant demodulation device, and the end of the tension meter data line is connected to the relevant acquisition device. The first mooring cable is a polymer synthetic fiber rope. The upper end of the carbon fiber composite mooring cable is anchored into the first anchor. The outer cylindrical surface of the first anchor is machined with external threads that are screwed into the internal threads of the inner hole of the first lifting lug. There is a space between the bottom plate of the first anchor and the bottom plate of the first lifting lug. The carbon fiber composite rod of the carbon fiber composite mooring cable passes through the bottom plate of the first anchor. A first displacement gauge is installed on several carbon fiber composite rods and connected to the first positioning screw. The optical fiber embedded in the carbon fiber composite rod is led out from the end of the carbon fiber composite rod and connected to the armored optical fiber in the space between the bottom plate of the anchor and the bottom plate of the first lifting lug. One armored optical fiber connects multiple fiber cores. A hole is opened on the bottom plate of the first lifting lug to lead the armored optical fiber in the bottom plate of the first lifting lug out of the first lifting lug, and waterproof glue is injected into the hole. The armored optical fiber and tension meter data line are arranged in parallel and protected by a sleeve throughout. They are attached to the polymer synthetic fiber cable and led up to the floating platform together. The upper end of the first lifting lug is connected to the insertion end of the first shackle. The upper part of the first shackle is connected to the second shackle. The second shackle is connected to the tension gauge. The upper end of the tension gauge is connected to the third shackle. The upper part of the third shackle is connected to the eyelet and the polymer synthetic fiber cable. The second mooring cable is a steel anchor chain. The lower end of the carbon fiber composite mooring cable is anchored into the second anchor. The outer cylindrical surface of the second anchor is machined with external threads, which are screwed into the internal threads of the inner hole of the second lifting lug. There is a space between the bottom plate of the second anchor and the bottom plate of the second lifting lug. The carbon fiber composite rod of the carbon fiber composite mooring cable passes through the bottom plate of the second anchor. Several carbon fiber composite rods are selected from the carbon fiber composite rods that extend out of the bottom plate of the anchor. The center point of several carbon fiber composite rods is equidistant from the center of the anchor, and the center points of several carbon fiber composite rods are arranged in a centrally symmetrical manner with respect to the center of the anchor. In a plurality of the carbon fiber composite rods, the end of each carbon fiber composite rod is connected to a probe of one of the displacement gauges via a connecting cap; Two connecting metal plates are symmetrically clamped at one end on both sides of the displacement gauge and fixedly connected to the displacement gauge by the first fixing bolt; the other end is symmetrically clamped at both sides of the positioning screw and fixedly connected to the positioning screw by the second fixing bolt. When the carbon fiber composite rod in the anchor slips relative to the anchor, the connecting cap moves axially with the carbon fiber composite rod, causing the probe of the displacement gauge to move axially. The average value of the displacement measured by several displacement gauges is the anchor slip. The lower end of the second lifting lug is connected to the insertion end of the fourth shackle, and the lower end of the fourth shackle is connected to the steel anchor chain segment. The steel anchor chain segment is equipped with an anchor chain ring, and two stress gauges are welded on the anchor ring. The end of the steel anchor chain segment is fixed on a gravity anchoring foundation. The foundation adopts a square frustum shape with the bottom recessed inward.

2. The carbon fiber composite composite mooring cable system for offshore floating structures according to claim 1, characterized in that, The carbon fiber composite mooring cable includes: carbon fiber composite rods, high-strength material strips, and protective sleeves. Multiple carbon fiber composite rods are arranged in parallel and twisted at a slight angle. The carbon fiber composite rod group is wrapped with high-strength material strips, and two layers of protective sleeves are added to protect the internal structure. The optical fiber is implanted in some of the carbon fiber composite rods.

3. The carbon fiber composite composite mooring cable system for offshore floating structures according to claim 2, characterized in that, The number of carbon fiber composite rods with embedded optical fibers in the carbon fiber composite mooring cable shall not be less than one-third of the total number of carbon fiber composite rods.

4. The carbon fiber composite composite mooring cable system for offshore floating structures according to claim 1, characterized in that, Select three carbon fiber composite rods from the bottom plate of the anchorage. The center points of the three carbon fiber composite rods are equidistant from the center of the anchorage, and the lines connecting the center points of the three carbon fiber composite rods to the center of the anchorage form a 120° angle with each other.

5. The carbon fiber composite composite mooring cable system for offshore floating structures according to claim 1, characterized in that, The stress gauge is a vibrating wire stress gauge. One of the anchor rings in the anchor chain is cut into two half anchor rings. The vibrating wire stress gauge is connected between the two half anchor rings. The data line of the vibrating wire stress gauge is led outward from the adapter and is protected by a protective sleeve.

6. The carbon fiber composite composite mooring cable system for offshore floating structures according to claim 1, characterized in that, The displacement gauge is an underwater miniature displacement gauge.

7. The self-monitoring method for a carbon fiber composite mooring cable system for offshore floating structures according to any one of claims 1 to 6, characterized in that: Real-time strain data of the internal intelligent carbon fiber composite rod is obtained by using optical fibers embedded in the carbon fiber composite mooring cable. By measuring stress data with a tension meter, the distribution of strain difference Δε along the cable length direction under a certain stress difference Δσ is obtained. For an intact composite rod, the distribution of strain difference Δε is a horizontal straight line. If a jump occurs in the distribution diagram, the jump section is the damaged section. The stiffness distribution of the composite rod is calculated by E=Δσ / Δε. The damage stiffness value Cd of the damaged section is equal to the initial stiffness E0 minus the stiffness value Ed of the damaged section, that is, Cd=E0-Ed. Finally, the location and size of the damage were determined based on the anchorage slippage detected by the displacement gauge inside the carbon fiber composite mooring cable, and the overall damage status of the carbon fiber composite mooring cable was judged.

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