A stress and strain monitoring system for the foundation structure of an offshore wind farm jacket

Abstract

The invention discloses a stress strain monitoring system for a jacket foundation structure of an offshore wind farm in the field of marine platform structure monitoring technology, comprising a jacket, wherein the jacket has a point stress measurement section, a cross-section axial force measurement section and a cross-section bending moment measurement section; four point stress measurement components are distributed at 90° intervals in the point stress measurement section and connected to a data acquisition module to form a Wheatstone single-arm bridge; two cross-section axial force measurement components are distributed along the main wind direction in the cross-section axial force measurement section and connected to the data acquisition module positively and negatively to form a Wheatstone full bridge; two cross-section bending moment measurement components are distributed along the main wind direction in the cross-section bending moment measurement section and connected to the data acquisition module positively and negatively to form a Wheatstone full bridge. The invention can not only measure the structural strain of a single point, but also measure the axial force and bending moment of the entire cross section of the structure through the Wheatstone bridge principle, comprehensively improving the current offshore wind power structure load monitoring means, and providing measurement data for iterative optimization of underwater foundation structures.

Description

Technical Field

[0001] The present invention relates to the technical field of marine platform structure monitoring, and in particular to a stress and strain monitoring system for a jacket foundation structure of an offshore wind farm. Background Art

[0002] The jacket foundation is one of the main foundation types used in offshore wind farms, with advantages such as good stability and good adaptability to water depth. However, the jacket foundation of offshore wind turbines will be affected by complex dynamic environments during long-term operation. Therefore, in order to timely grasp the health status of the jacket foundation of offshore wind farms and ensure the safety, integrity, applicability and durability of the long-term service of offshore wind farms, it is necessary to conduct safety monitoring of the jacket foundation.

[0003] Stress and strain monitoring is one of the most important monitoring items for the jacket foundation. Common strain monitoring equipment includes vibrating-wire static strain gauges, resistive full-bridge strain gauges, and fiber Bragg grating strain gauges. However, the mainstream static steel plate strain gauges currently installed on the jacket have a low acquisition frequency, with a maximum frequency of only 3 Hz. The output data does not have the ability to perform fatigue analysis and can only make basic judgments on the health of the structure. The full-bridge strain gauges currently used have poor accuracy and can only measure the strain value of a single point, making it impossible to monitor the internal force of the cross section. Fiber Bragg grating strain gauges have disadvantages such as easy breakage of the optical cable after engraving and harsh installation conditions.

[0004] With the large-scale development and construction of offshore wind power projects, effective risk assessment and optimization iteration of wind turbine foundation structures are imminent. Therefore, there is an urgent need for an offshore wind farm jacket foundation structure stress and strain monitoring system with high accuracy, good real-time performance, and the ability to monitor multiple structural physical quantities. Summary of the invention

[0005] In view of this, the object of the present invention is to provide a stress and strain monitoring system for a jacket foundation structure of an offshore wind farm in order to solve the above technical problems, so as to perform remote online automatic monitoring of the stress and strain of the jacket foundation structure.

[0006] The technical solution adopted by the present invention is: a stress and strain monitoring system for a jacket foundation structure of an offshore wind farm, comprising:

[0007] A conductor frame, the conductor frame having a point stress measurement section, a cross-sectional axial force measurement section and a cross-sectional bending moment measurement section;

[0008] A data acquisition module, wherein the data acquisition module is installed on the top of the catheter rack;

[0009] Point stress measurement components, four of which are distributed at intervals of 90° along the circumferential direction on the point stress measurement section, and the resistance strain gauges of the four point stress measurement components are connected to the data acquisition module through a four-core cable to form a Wheatstone single-arm bridge;

[0010] A cross-sectional axial force measurement assembly, wherein two cross-sectional axial force measurement assemblies are distributed at intervals of 180° along the main wind direction on the cross-sectional axial force measurement section, and the first T-shaped assembled resistance strain gauges of the two cross-sectional axial force measurement assemblies are connected to the data acquisition module via a four-core cable to form a Wheatstone full bridge;

[0011] A section bending moment measurement assembly, wherein two of the section bending moment measurement assemblies are arranged at intervals of 180° along the main wind direction at the section bending moment measurement section, and the second T-shaped assembled resistance strain gauges of the two section bending moment measurement assemblies are connected to the data acquisition module through a four-core cable to form a Wheatstone full bridge.

[0012] Preferably, the conductor rack includes a fixedly connected column and a connecting pipe, and the point stress measurement section is arranged on the column and is located above and / or below the connection position between the column and the connecting pipe; the cross-sectional axial force measurement section is arranged on the column and is located above the connection position between the column and the connecting pipe; the cross-sectional bending moment measurement section is arranged on the connecting pipe.

[0013] Preferably, the point stress measurement assembly includes a resistive strain gauge, a strain gauge protection cover, protective putty and a welding terminal, the resistive strain gauge is adhesively fixed to the outer wall of the catheter frame, the strain gauge protection cover is arranged on the outside of the resistive strain gauge and is fixedly connected to the catheter frame, the welding terminal is fixedly connected to one end of the resistive strain gauge, the four-core cable passes through the strain gauge protection cover and is fixedly connected to the welding terminal, and the protective putty is filled between the resistive strain gauge and the strain gauge protection cover.

[0014] Preferably, the welding terminal is fixedly connected to the bottom end of the resistive strain gauge, and the end of the four-core cable passes through the top end of the strain gauge protection cover and is fixedly connected to the welding terminal.

[0015] Preferably, a signal transmission protection component is provided on the outside of the four-core cable, and the signal transmission protection component includes a seamless steel pipe, a gasket and a junction box. A plurality of the gaskets are linearly welded and fixed on the outer wall of the conductor frame. The seamless steel pipe is sleeved on the outside of the four-core cable, and the seamless steel pipe is fixedly connected to the gasket. The junction box is fixedly welded on the outer wall of the conductor frame, and a circular hole is opened on the side wall of the junction box, and the end of the seamless steel pipe extends axially into the circular hole.

[0016] Preferably, the sampling frequency of the data acquisition module is not less than 50 Hz, and the data acquisition module includes multiple channels. The data acquisition module is connected to the server electrical signal through a switch, a submarine optoelectronic composite cable, and the server has a built-in data analysis module for calculating point stress, cross-sectional axial stress and bending moment.

[0017] Preferably, the calculation formula of the point stress is:

[0018] U=ε / 4*K1

[0019] F=ε*E

[0020] Among them, U is the output voltage, K1 is the strain gauge coefficient, ε is the strain, E is the elastic modulus, and F is the stress.

[0021] Preferably, the calculation formula of the cross-sectional axial stress is as follows:

[0022] U=(ε1-ε2-ε3+ε4) / C1*K

[0023] ε m1 =(ε1-ε2-ε3+ε4) / C1

[0024] F n =ε m1 *E

[0025] Among them, U is the output voltage, K is the strain gauge coefficient, C1 is the bridge coefficient, ε1-ε2-ε3+ε4 are the strains generated by the resistance strain gauges R1~R4 constituting the two first T-type assembled resistance strain gauges, ε m1 is the cross-sectional axial strain, E is the elastic modulus, F n is the axial force of the section.

[0026] Preferably, the calculation formula of the section bending moment is as follows:

[0027] U=(ε1-ε2+ε3-ε4) / C2*K

[0028] ε m2 =(ε1-ε2+ε3-ε4) / C2

[0029] F y =ε m2 *E

[0030] M y =F y *L

[0031] Among them, U is the output voltage, K is the strain gauge coefficient, C2 is the bridge coefficient, ε1-ε2+ε3-ε4 are the strains generated by the resistance strain gauges R1~R4 constituting the two second T-type assembled resistance strain gauges, εm2 is the cross-sectional bending strain, E is the elastic modulus, F y is the radial force, M y is the bending moment and L is the lever arm.

[0032] Beneficial effects of the present invention:

[0033] The present invention arranges strain gauges at predetermined test points of the conductor frame, protects the strain gauges, and bridges the strain gauges according to the Wheatstone bridge principle. The data is transmitted to a data acquisition module through a four-core cable. The data acquisition module transmits the data to a server through a communication device. The server is installed with data analysis software. The monitoring data is processed by the data analysis software to realize online conversion of voltage signals into physical quantities such as strain, bending moment, and axial force, thereby realizing structural point strain monitoring, structural section axial force monitoring, and structural section bending moment monitoring, thereby realizing remote online automatic monitoring of stress and strain of the conductor frame foundation structure.

[0034] The present invention is no longer limited to the monitoring of strain at a single point, but is expanded to the load test of the entire jacket foundation, adding stress and strain monitoring parameters for the jacket foundation structure of the offshore wind farm, improving the stress and strain monitoring means for the jacket foundation structure of the offshore wind farm, providing an accurate assessment for the safe operation of the entire wind farm, and providing measured and effective data for the iterative optimization of the underwater foundation structure. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a structural schematic diagram of the offshore wind power conductor frame foundation structure stress and strain monitoring system of the present invention;

[0036] Figure 2 It is a structural schematic diagram of the point stress measurement assembly of the present invention;

[0037] Figure 3 It is a structural schematic diagram of the signal transmission protection component of the present invention;

[0038] Figure 4 Wheatstone bridge diagram for point strain monitoring;

[0039] Figure 5 Wheatstone bridge diagram for cross-section axial force monitoring;

[0040] Figure 6 Wheatstone bridge diagram for section bending moment monitoring;

[0041] Figure 7 This is a network topology diagram of the offshore wind power conductor frame foundation structure stress and strain monitoring system of the present invention.

[0042] Description of reference numerals in the figures:

[0043] 100. Conductor rack;

[0044] 110, point stress measurement section; 120, cross-sectional axial force measurement section; 130, cross-sectional bending moment measurement section; 140, column; 150, connecting pipe;

[0045] 200. Data acquisition module;

[0046] 300. Point stress measurement assembly; 310. Resistive strain gauge; 320. Strain gauge protection cover; 330. Protective glue; 340. Welding terminal.

[0047] 400, cross-sectional axial force measurement assembly; 410, first T-shaped assembled resistance strain gauge;

[0048] 500, section bending moment measurement assembly; 510, second T-type assembled resistance strain gauge;

[0049] 600, four-core cable;

[0050] 700, signal transmission protection component;

[0051] 710, seamless steel pipe; 720, gasket; 730, junction box; 740, round hole. DETAILED DESCRIPTION

[0052] The specific embodiments of the present invention are further described in detail below in conjunction with the accompanying drawings. These embodiments are only used to illustrate the present invention, but not to limit the present invention.

[0053] In the description of the present invention, it should be noted that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are used for descriptive purposes only and cannot be understood as indicating or implying relative importance.

[0054] In the description of the present invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installed", "connected", and "connected" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0055] Furthermore, in the description of the present invention, unless otherwise specified, “plurality” means two or more.

[0056] Examples, such as Figure 1-Figure 7 As shown, a stress and strain monitoring system for the foundation structure of a jacket of an offshore wind farm is used for remote online automatic monitoring of the stress and strain of the jacket foundation structure; the system comprises:

[0057] The jacket 100 has a point stress measurement section 110 , a cross-sectional axial force measurement section 120 , and a cross-sectional bending moment measurement section 130 at a predetermined test position.

[0058] A data acquisition module 200, which is installed on the top of the catheter rack 100;

[0059] The point stress measurement components 300 are four in number, and the four point stress measurement components 300 are distributed at the position of the point stress measurement section 110 at 90° intervals along the circumferential direction, and the resistive strain gauges 310 of the four point stress measurement components 300 are connected to the data acquisition module 200 through a four-core cable 600 to form a Wheatstone single-arm bridge.

[0060] The cross-sectional axial force measurement assembly 400 has two cross-sectional axial force measurement assemblies 400, and the two cross-sectional axial force measurement assemblies 400 are distributed at intervals of 180° along the main wind direction on the cross-sectional axial force measurement section 120, and the first T-shaped assembled resistance strain gauges 410 of the two cross-sectional axial force measurement assemblies 400 are connected to the data acquisition module 200 via a four-core cable 600 to form a Wheatstone full bridge.

[0061] The cross-sectional bending moment measurement assembly 500 has two cross-sectional bending moment measurement assemblies 500, and the two cross-sectional bending moment measurement assemblies 500 are arranged at a cross-sectional bending moment measurement section 130 at an interval of 180° along the main wind direction, and the second T-shaped assembled resistance strain gauges 510 of the two cross-sectional bending moment measurement assemblies 500 are connected to the data acquisition module 200 via a four-core cable 600 in positive and negative directions to form a Wheatstone full bridge.

[0062] The present application arranges strain gauges at predetermined test points of the conductor frame 100, protects the strain gauges, and bridges the strain gauges according to the Wheatstone bridge principle, and transmits the data to the data acquisition module 200 through a four-core cable 600. The data acquisition module 200 transmits the data to a remote server through a communication device. The server is installed with data analysis software, and the monitoring data is processed by the data analysis software to realize online conversion of voltage signals into physical quantities such as strain, bending moment, and axial force, that is, to realize structural point strain monitoring, structural section axial force monitoring, and structural section bending moment monitoring, thereby realizing remote online automatic monitoring of stress and strain of the conductor frame foundation structure.

[0063] In a specific implementation, Figure 1 As shown, the jacket 100 includes a column 140 and a connecting pipe 150 that are fixedly connected, and the predetermined test position of the jacket 100 is a T-shaped connection node between the column 140 and the connecting pipe 150 .

[0064] Specifically, the point stress measurement section 110 is provided on the column 140, and the point stress measurement section 110 is located above and / or below the connection position between the column 140 and the connecting pipe 150. The cross-sectional axial force measurement section 120 is provided on the column 140, and the cross-sectional axial force measurement section 120 is located above the connection position between the column 140 and the connecting pipe 150. The cross-sectional bending moment measurement section 130 is provided on the connecting pipe 150.

[0065] For example, at the connection position between the column 140 and the connecting pipe 150, there are two point stress measurement sections 110, a cross-sectional axial force measurement section 120 and a cross-sectional bending moment measurement section 130. The point stress measurement section 110 and the cross-sectional axial force measurement section 120 are arranged on the column 140, and the two point stress measurement sections 110 are located above and below the cross-sectional axial force measurement section 120, respectively.

[0066] In a specific implementation, Figure 2 As shown, the point stress measurement assembly 300 includes a resistive strain gauge 310, a strain gauge protection cover 320, a protective putty 330 and a welding terminal 340, wherein the resistive strain gauge 310 is bonded and fixed to the outer wall of the catheter frame 100 in parallel, that is, the resistive strain gauge 310 is bonded and fixed to the outer wall surface of the column 140 along the axial direction of the column 140; the strain gauge protection cover 320 covers the outer side of the resistive strain gauge 310, and the strain gauge protection cover 320 is welded and fixedly connected to the catheter frame 100, the welding terminal 340 is fixedly connected to the resistive strain gauge 310, and the four-core cable 600 passes through the strain gauge protection cover 320 and is fixedly connected to the welding terminal 340; the protective putty 330 is filled between the resistive strain gauge 310 and the strain gauge protection cover 320.

[0067] This arrangement is because: the resistance strain gauge 310 and the welding terminal 340 are installed on the outer wall surface of the catheter frame 100 through an adhesive. After the adhesive is oxidized, the resistance strain gauge 310 will fall off, thereby causing monitoring failure. In this embodiment, a strain gauge protection cover 320 is provided on the outer side of the resistance strain gauge 310, and a protective glue 330 is filled between the strain gauge protection cover 320 and the resistance strain gauge 310, which can not only prevent the adhesive from being oxidized, but also ensure the stability of the connection between the resistance strain gauge 310 and the catheter frame 100.

[0068] Preferably, the welding terminal 340 is fixedly connected to the bottom end of the resistive strain gauge 310 , and the end of the four-core cable 600 passes through the top end of the strain gauge protection cover 320 and is fixedly connected to the welding terminal 340 .

[0069] This arrangement is because: the four-core cable 600 passes through the top of the strain gauge protection cover 320 and is connected to the bottom of the resistive strain gauge 310 through the welding terminal 340, so that the inlet and outlet directions of the four-core cable 600 should be opposite, thereby preventing damage caused by inadequate protection of the core wires.

[0070] It should be noted that strain gauge protection covers are provided on the outside of the first T-shaped assembled resistance strain gauge 410 and the second T-shaped assembled resistance strain gauge 510, and protection glue is filled inside the strain gauge protection covers.

[0071] In a specific implementation, Figure 3 As shown, a signal transmission protection component 700 is provided outside the four-core cable 600 for protecting the four-core cable 600. The signal transmission protection component 700 includes a seamless steel pipe 710, a gasket 720 and a junction box 730, wherein the number of the gaskets 720 is multiple, and the multiple gaskets 720 are linearly welded and fixed on the outer wall of the conduit frame 100, that is, the gaskets 720 are welded and fixed on the outer wall of the column 140 and the connecting pipe 150 of the conduit frame 100 along the extension direction of the four-core cable 600; the seamless steel pipe 710 is sleeved on the outside of the four-core cable 600, that is, the four-core cable 600 is passed through The interior of the seamless steel pipe 710 is used to protect the four-core cable 600, and the seamless steel pipe 710 is fixedly connected to the gasket 720 to fix the seamless steel pipe 710 to the conductor frame 100; the junction box 730 is fixedly welded to the outer wall of the column 140 of the conductor frame 100, and a circular hole 740 is opened on the side wall of the junction box 730. The end of the seamless steel pipe 710 extends axially into the circular hole 740, which is used to collect and lead the four-core cables 600 at multiple cross-sectional positions.

[0072] Specifically, the junction box 730 is welded together by five steel plates, namely an upper steel plate, a lower steel plate, a left steel plate, a right steel plate and a front steel plate, and circular holes 740 matching the size of the seamless steel pipe 710 are opened on the upper steel plate, the lower steel plate, the left steel plate and the right steel plate. The front steel plate should be welded and sealed after the four-core cable 600 is threaded.

[0073] In a specific embodiment, if Figure 1 and Figure 7As shown, the data acquisition module 200 is located in the monitoring cabinet at the top of the conductor rack 100, and the sampling frequency of the data acquisition module 200 is not less than 50HZ; the data acquisition module 200 includes multiple channels, each channel can collect a set of monitoring data, each channel input end is an analog signal, and the output end is a digital signal; the data acquisition module 200 is connected through a switch, a submarine optoelectronic composite cable and a server electrical signal, and is used to transmit the digital signal to the server to realize remote online automatic monitoring; the server has a built-in data analysis module, and the data analysis module (data analysis software) is used to process the monitoring data and realize the online conversion of voltage signals into physical quantities such as strain, bending moment, axial force, etc., so as to realize the calculation of point stress, cross-sectional axial stress and bending moment.

[0074] Specifically, Figure 4 As shown, when performing point strain measurement, four resistive strain gauges 310 are distributed at 90° intervals around the circumferential direction of the column 140 at the position of the point stress measurement section 110, and the four resistive strain gauges 310 form four Wheatstone 1 / 4 bridges with the data acquisition module 200 through signal lines, thereby transmitting the voltage signal to the data acquisition module 200. The calculation formula of the point stress is:

[0075] U=ε / 4*K1

[0076] F=ε*E

[0077] Among them, U is the output voltage, K1 is the strain gauge coefficient, ε is the strain, E is the elastic modulus, and F is the stress.

[0078] like Figure 5 As shown, when measuring the cross-sectional axial stress, at the cross-sectional axial force measurement section 120 of the column 140, two groups of first T-type assembled resistance strain gauges 410 are arranged on the outer wall of the column 140 at intervals of 180° along the main wind direction, that is, the connection line of the two groups of first T-type assembled resistance strain gauges 410 is the same as the main wind direction. To judge the stress state of the cross-sectional axial force measurement section 120, where tension is "+" and compression is "-", through the Wheatstone bridge principle, the "I" and "-" signal judgments on both sides should be consistent, and the positive and negative of the four strain gauges are connected to form a full bridge. The calculation formula for the cross-sectional axial stress is as follows:

[0079] U=(ε1-ε2-ε3+ε4) / C1*K

[0080] ε m1 =(ε1-ε2-ε3+ε4) / C1

[0081] F n =ε m1 *E

[0082] Among them, U is the output voltage, K is the strain gauge coefficient, C1 is the bridge coefficient, ε1-ε2-ε3+ε4 are the strains generated by the resistance strain gauges R1~R4 constituting the two first T-type assembled resistance strain gauges, ε m1 is the cross-sectional axial strain, E is the elastic modulus, F n is the axial force of the section.

[0083] like Figure 6 As shown, when measuring the cross-sectional bending moment, at the cross-sectional bending moment measuring section 130 of the connecting pipe 150 of the conductor frame 100, two sets of second T-shaped assembled resistance strain gauges 510 are arranged on the outer wall of the column 140 at intervals of 180° along the main wind direction, that is, the connection line of the two sets of second T-shaped assembled resistance strain gauges 510 is the same as the main wind direction. The stress state of the cross-sectional bending moment measuring section 130 is judged, where tension is "+" and compression is "-". Through the Wheatstone bridge principle, the "I" and "-" signals on both sides are judged to be opposite, and the positive and negative of the four strain gauges are connected to form a full bridge. The calculation formula of the cross-sectional bending moment is as follows:

[0084] U=(ε1-ε2+ε3-ε4) / C2*K

[0085] ε m2 =(ε1-ε2+ε3-ε4) / C2

[0086] F y =ε m2 *E

[0087] M y =F y *L

[0088] Among them, U is the output voltage, K is the strain gauge coefficient, C2 is the bridge coefficient, ε1-ε2+ε3-ε4 are the strains generated by the resistance strain gauges R1~R4 constituting the two second T-type assembled resistance strain gauges, ε m2 is the cross-sectional bending strain, E is the elastic modulus, F y is the radial force, M y is the bending moment and L is the lever arm.

[0089] The working principle of the monitoring system of the present invention is as follows:

[0090] Through three arrangements, structural point strain monitoring, structural section axial force monitoring and structural section bending moment monitoring are realized respectively; firstly, through the force calculation of the conductor frame structure, the key parts are selected to arrange strain gauges, and then the strain gauges are protected. At the same time, different physical quantities are measured according to the Wheatstone bridge principle, and transmitted to the data acquisition module through cables. The sampling frequency of the acquisition module is not less than 50HZ, and the interference signals caused by temperature drift and zero drift can be eliminated; the collected data are transmitted to the remote server through communication equipment, and the data are analyzed and processed by the data analysis software in the server to obtain the strain and internal force of the structure, thereby providing measured effective data for the optimization and iteration of the structure.

[0091] Compared with the prior art, this application has at least the following beneficial technical effects:

[0092] The offshore wind farm jacket foundation structure stress and strain monitoring system in this application can not only measure the structural strain at a single point, but also measure the axial force and bending moment of the entire cross-section of the structure through the Wheatstone bridge principle, which comprehensively improves the current offshore wind power structure load monitoring methods and provides measurement data for iterative optimization of underwater foundation structures.

[0093] The above are only preferred embodiments of the present invention. It should be pointed out that, for ordinary technicians in this technical field, several improvements and substitutions can be made without departing from the technical principles of the present invention. These improvements and substitutions should also be regarded as the scope of protection of the present invention.

Claims

1. A stress and strain monitoring system for an offshore wind farm jacket foundation structure, characterized in that: include: A catheter frame (100), the catheter frame (100) having a point stress measurement section (110), a cross-sectional axial force measurement section (120), and a cross-sectional bending moment measurement section (130); A data acquisition module (200), wherein the data acquisition module (200) is installed on the top of the catheter rack (100); Point stress measurement components (300), wherein four of the point stress measurement components (300) are distributed at intervals of 90 degrees along the circumferential direction on the point stress measurement section (110), and the resistance strain gauges (310) of the four point stress measurement components (300) are connected to the data acquisition module (200) via a four-core cable (600) to form a Wheatstone single-arm bridge; A cross-sectional axial force measurement assembly (400), wherein two cross-sectional axial force measurement assemblies (400) are distributed at intervals of 180° along the main wind direction on the cross-sectional axial force measurement section (120), and the first T-shaped assembled resistance strain gauges (410) of the two cross-sectional axial force measurement assemblies (400) are connected to the data acquisition module (200) via a four-core cable (600) to form a Wheatstone full bridge; A cross-sectional bending moment measurement assembly (500), wherein two cross-sectional bending moment measurement assemblies (500) are arranged at intervals of 180° along the main wind direction at the cross-sectional bending moment measurement section (130), and the second T-shaped assembled resistance strain gauges (510) of the two cross-sectional bending moment measurement assemblies (500) are connected to the data acquisition module (200) via a four-core cable (600) to form a Wheatstone full bridge.

2. The offshore wind farm jacket foundation structure stress and strain monitoring system according to claim 1, characterized in that: The catheter rack (100) comprises a column (140) and a connecting pipe (150) that are fixedly connected, and the point stress measurement section (110) is arranged on the column (140) and is located above and / or below the connection position between the column (140) and the connecting pipe (150); the cross-sectional axial force measurement section (120) is arranged on the column (140) and is located above the connection position between the column (140) and the connecting pipe (150); and the cross-sectional bending moment measurement section (130) is arranged on the connecting pipe (150).

3. The offshore wind farm jacket foundation structure stress and strain monitoring system according to claim 1, characterized in that: The point stress measurement assembly (300) comprises a resistive strain gauge (310), a strain gauge protection cover (320), a protective glue (330) and a welding terminal (340); the resistive strain gauge (310) is bonded and fixed to the outer wall of the catheter frame (100); the strain gauge protection cover (320) is arranged on the outside of the resistive strain gauge (310) and is fixedly connected to the catheter frame (100); the welding terminal (340) is fixedly connected to one end of the resistive strain gauge (310); the four-core cable (600) passes through the strain gauge protection cover (320) and is fixedly connected to the welding terminal (340); and the protective glue (330) is filled between the resistive strain gauge (310) and the strain gauge protection cover (320).

4. The offshore wind farm jacket foundation structure stress and strain monitoring system according to claim 3, characterized in that: The welding terminal (340) is fixedly connected to the bottom end of the resistance strain gauge (310), and the end of the four-core cable (600) passes through the top end of the strain gauge protection cover (320) and is fixedly connected to the welding terminal (340).

5. The offshore wind farm jacket foundation structure stress and strain monitoring system according to claim 1, characterized in that: A signal transmission protection component (700) is provided on the outside of the four-core cable (600), and the signal transmission protection component (700) includes a seamless steel pipe (710), a gasket (720) and a junction box (730). A plurality of the gaskets (720) are linearly welded and fixed on the outer wall of the conduit frame (100). The seamless steel pipe (710) is sleeved on the outside of the four-core cable (600), and the seamless steel pipe (710) and the gasket (720) are fixedly connected. The junction box (730) is fixedly welded on the outer wall of the conduit frame (100), and a circular hole (740) is opened on the side wall of the junction box (730), and the end of the seamless steel pipe (710) extends axially into the circular hole (740).

6. The offshore wind farm jacket foundation structure stress and strain monitoring system according to claim 1, characterized in that: The sampling frequency of the data acquisition module (200) is not less than 50 Hz, and the data acquisition module (200) comprises a plurality of channels. The data acquisition module (200) is connected to a server through a switch, a submarine optoelectronic composite cable and an electrical signal. The server has a built-in data analysis module for calculating point stress, cross-sectional axial stress and bending moment.

7. The offshore wind farm jacket foundation structure stress and strain monitoring system according to claim 6, characterized in that: The calculation formula of the point stress is: U=ε / 4*K1 F=ε*E Among them, U is the output voltage, K1 is the strain gauge coefficient, ε is the strain, E is the elastic modulus, and F is the stress.

8. The offshore wind farm jacket foundation structure stress and strain monitoring system according to claim 6, characterized in that: The calculation formula of the cross-section axial stress is as follows: U=(ε1-ε2-ε3+ε4) / C1*K e m1 =(ε1-ε2-ε3+ε4) / C1 F n =e m1 *E Among them, U is the output voltage, K is the strain gauge coefficient, C1 is the bridge coefficient, ε1-ε2-ε3+ε4 are the strains generated by the resistance strain gauges R1~R4 constituting the two first T-type assembled resistance strain gauges, ε m1 is the cross-sectional axial strain, E is the elastic modulus, F n is the axial force of the section.

9. The offshore wind farm jacket foundation structure stress and strain monitoring system according to claim 6, characterized in that: The calculation formula of the section bending moment is as follows: U=(ε1-ε2+ε3-ε4) / C2*K e m2 =(ε1-ε2+ε3-ε4) / C2 F y =e m2 *E M y =F y *L Among them, U is the output voltage, K is the strain gauge coefficient, C2 is the bridge coefficient, ε1-ε2+ε3-ε4 are the strains generated by the resistance strain gauges R1~R4 constituting the two second T-type assembled resistance strain gauges, ε m2 is the cross-sectional bending strain, E is the elastic modulus, F y is the radial force, M y is the bending moment and L is the lever arm.

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