A model test measurement method for cross-sectional load of a semi-submersible floating foundation

Abstract

This invention discloses a model test measurement method for the cross-sectional load of a semi-submersible floating foundation, relating to the field of wind power generation technology. The method employs a multi-body segmented structure, dividing the semi-submersible floating foundation into multiple independent sub-structure models. These sub-structure models are connected using connectors to form a complete segmented floating foundation model. The connectors serve as connecting components for assembling the segmented floating foundation models and also as measurement carriers for strain sensors, acting as measurement elements for the cross-sectional load, with the cross-section to be measured positioned at their location. Based on the strain measurement method, FBG fiber grating strain sensors are used to measure the cross-sectional load, which includes axial force and bending moment. The FBG strain sensors are deployed on the surface of the measurement element. This invention utilizes a multi-body segmented structure to simulate wind turbine foundations and obtains the internal forces within the cross-section based on the strain measurement method, improving the research efficiency of floating wind turbine model tests and providing technical support for safety design.

Description

Technical Field

[0001] This invention relates to the field of wind power generation technology, and in particular to a model test measurement method for the cross-sectional load of a semi-submersible floating foundation. Background Technology

[0002] Wind energy is an important clean energy source, and the development of clean energy, primarily wind energy, has become a key focus and important development trend in China's energy policy. Floating wind turbines, with their wide range of applicable water depths, low installation costs, and flexible deployment, are considered the main equipment for the large-scale development and utilization of next-generation offshore wind energy. Developing floating wind turbine technology has become an important direction for future offshore wind energy development.

[0003] Currently, there are four main types of foundations used for floating wind turbines: single-column foundations, semi-submersible foundations, tension leg foundations, and barge foundations. Compared to the other three types, semi-submersible foundations offer better stability. Pool model testing is a crucial research method in the design and verification process of floating wind turbines. Current experimental research on semi-submersible floating wind turbines mainly focuses on the overall dynamic response characteristics of the turbine system. Current turbine model tests primarily use integrated foundation models to simulate the semi-submersible floating wind turbine foundation. However, the integrated foundation model method can only obtain the overall response characteristics of the foundation and cannot obtain the local structural internal forces of the foundation. Furthermore, there is a lack of effective experimental measurement methods for the structural internal forces (cross-sectional loads) of the semi-submersible foundation platform.

[0004] Therefore, those skilled in the art are dedicated to developing a model test measurement method for the cross-sectional load of a semi-submersible floating foundation. Summary of the Invention

[0005] In view of the above-mentioned deficiencies of the prior art, the technical problem to be solved by the present invention is that the integrated foundation model can only obtain the overall response characteristics of the foundation, but cannot obtain the local structural internal forces of the foundation, and lacks effective experimental measurement means for the structural internal forces of the foundation platform.

[0006] To achieve the above objectives, this invention provides a model test measurement method for the cross-sectional load of a semi-submersible floating foundation. The method employs a multi-body segmented structure, dividing the semi-submersible floating foundation into multiple independent sub-structure models. These sub-structure models are connected using connectors to form a complete segmented model of the semi-submersible floating foundation. The connectors serve as connecting components for assembling the segmented floating foundation models and also as measurement carriers for FBG fiber grating strain sensors. The connectors act as measuring elements for the cross-sectional load of the semi-submersible floating foundation, with the cross-section to be measured positioned at the location of the measuring element. The measurement method is based on strain measurement, using the FBG fiber grating strain sensor to measure the load on the cross-section of the semi-submersible floating foundation. The cross-sectional load includes the axial force and bending moment of the cross-section, and the FBG fiber grating strain sensor is disposed on the surface of the measuring element.

[0007] Furthermore, the substructure model includes one central substructure and multiple side substructures, wherein,

[0008] The central substructure includes a central column and a first pontoon. The central column is connected and fixed by the first pontoon. There are multiple first pontoons, and the number of the first pontoons is the same as the number of the side substructures.

[0009] The side substructure includes a side column and a second buoy, wherein the side column is connected and fixed by the second buoy;

[0010] Both the first and second pontoons have cross-sections, which are perpendicular to the central axes of the first and second pontoons, respectively. The cross-sections are sealed and thickened, and screw holes are provided for connection with the connector.

[0011] Furthermore, the substructure is configured as a hollow shell structure, and the hollow shell structure can hold weights to adjust the structural mass and inertia distribution. The outer shell of the substructure extends into an extended shell at the cross-section. After being connected to the connector, the extended shell covers the connector to reduce the change in the original topological shape of the first float and the second float at the cross-section to be measured.

[0012] Furthermore, the extended housing is provided with a live part and a detachable part to facilitate the threaded assembly of the connector with the substructure. The extended housing is made of resin glass to enable visualization of the connector inside the extended housing.

[0013] Furthermore, the connector includes a cylinder and end flanges. The cylinder is a hollow cylinder with a uniform cross-section, and the two ends of the cylinder are the end flanges. The shape of the end flanges is consistent with the cross-section of the first float and the second float. The end flanges are provided with screw holes for connection with the cross-section.

[0014] Furthermore, the connector is made of metal, the number of connectors is consistent with the number of side substructures, and the length-to-diameter ratio of the connector cylinder is greater than 5.

[0015] Furthermore, the FBG fiber grating strain sensor is arranged along the axial direction of the connecting cylinder on the cross-section to be measured. The FBG fiber grating strain sensor is arranged at the endpoints of the horizontal and vertical neutral axes of the cross-section to be measured. The FBG fiber grating strain sensor is fixedly bonded to the outer surface of the connecting cylinder by waterproof and insulating rigid adhesive. The cross-section to be measured is the cross-section where the midpoint of the central axis of the connecting cylinder is located. The number of FBG fiber grating strain sensors is 4.

[0016] Furthermore, the strain monitored by the FBG fiber grating strain sensor includes temperature strain, installation strain, and load strain. The installation strain is removed by zeroing the strain value before the test. The temperature strain is solved using the temperature compensation method and / or the strain difference method. The load on the cross-section is solved using the load strain.

[0017] ε=ε load +ε inst +ε temp

[0018] ε represents the strain monitored by the FBG fiber grating strain sensor. load ε is the strain caused by the cross-sectional load. inst ε represents the installation strain caused by sensor installation. temp This refers to the temperature strain caused by ambient temperature.

[0019] Furthermore, the temperature compensation method employs one or more temperature compensation plates, each using an FBG fiber grating strain sensor of the same specifications. The temperature compensation plate is attached to a piece of material of the same material as the component being tested but does not participate in deformation, and is subjected to the same temperature conditions as the component being tested. The strain monitored by the temperature compensation plate is the temperature strain ε of the FBG fiber grating strain sensor. temp The load on the cross section is:

[0020]

[0021] Where, ε load,iLet F be the load strain of the i-th FBG fiber grating strain sensor, i = a, b, c, d, where a and b are FBG fiber grating strain sensors at the upper endpoint of the vertical neutral axis, and c and d are FBG fiber grating strain sensors at the upper endpoint of the horizontal neutral axis. N M is the axial force on the cylindrical cross-section of the connector. hori M is the horizontal bending moment component of the cylindrical cross-section of the connector. vert Let E be the bending moment component in the vertical direction of the cylindrical cross-section of the connector, A be the elastic modulus of the connector, W be the cross-sectional area of ​​the cylindrical cross-section of the connector, and W be the section modulus of the cylindrical cross-section of the connector.

[0022] Furthermore, the strain difference method utilizes the fact that the temperature strain of the FBG fiber grating strain sensors on the same cross-section under test is the same, thereby solving for the bending moment value of that cross-section.

[0023]

[0024]

[0025] Where, ε i The strain data of the i-th FBG fiber grating strain sensor after initialization to zero, ε load,i Let M be the load strain of the i-th FBG fiber grating strain sensor, i = a, b, c, d, where a and b are FBG fiber grating strain sensors at the upper endpoint of the vertical neutral axis, and c and d are FBG fiber grating strain sensors at the upper endpoint of the horizontal neutral axis. hori M is the horizontal bending moment component of the cylindrical cross-section of the connector. vert Let E be the bending moment component in the vertical direction of the cylindrical cross-section of the connector, and W be the section modulus of the connecting component.

[0026] In a preferred embodiment of the present invention, the present invention has the following advantages over the prior art:

[0027] 1. This invention utilizes a multi-body segmented structure to simulate a wind turbine foundation. At the cross-section of interest, the integral foundation is divided into a multi-body structure. Elastic components are used to reassemble multiple substructures into an "integrated" foundation platform. At the same time, based on the strain measurement method, the elastic components are used as strain measurement carriers to measure the strain of the component cross-section, thereby obtaining the internal forces of the cross-section of the wind turbine foundation structure.

[0028] 2. This invention can simultaneously simulate and measure the overall response and local internal force characteristics of a floating wind turbine foundation in the same test, which helps to expand the research scope of wind turbine pool model tests, improves the research efficiency of floating wind turbine model tests, and provides technical support for the safe design of floating wind turbines.

[0029] The following will further explain the concept, specific structure, and technical effects of the present invention in conjunction with the accompanying drawings, so as to fully understand the purpose, features, and effects of the present invention. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the unassembled basic substructure and connectors of a preferred embodiment of the present invention;

[0031] Figure 2 This is a schematic diagram of the assembled semi-submersible foundation segment model according to a preferred embodiment of the present invention;

[0032] Figure 3 This is a schematic diagram of a connector and an FBG fiber optic grating sensor according to a preferred embodiment of the present invention.

[0033] Among them: 1-side substructure, 2-connector, 3-living body and detachable shell, 4-central substructure, 5-FBG fiber optic strain sensor, 6-cylinder, 7-end flange, 8-screw hole. Detailed Implementation

[0034] The following description, with reference to the accompanying drawings, illustrates several preferred embodiments of the present invention to make its technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0035] In the accompanying drawings, components with the same structure are indicated by the same numerical designation, and components with similar structures or functions are indicated by similar numerical designations. The dimensions and thicknesses of each component shown in the drawings are arbitrary, and the present invention does not limit the dimensions and thicknesses of each component. To make the illustrations clearer, the thickness of some components has been appropriately exaggerated in the drawings.

[0036] This invention proposes a method for measuring the cross-sectional load of semi-submersible foundations based on FBG fiber grating sensing technology. This method is applicable to water tank model tests. Unlike traditional floating wind turbine model tests, this method abandons the integrated foundation model approach used in traditional model tests and adopts a multi-body segmented structure mode. The floating foundation is divided into multiple independent sub-structure models, which are then connected by connectors to form a complete segmented floating foundation model. The connectors also serve as measuring elements for the cross-sectional load of the foundation, with the measuring element's location corresponding to the cross-section to be measured. Based on the strain measurement method, the cross-sectional load measurement uses higher-precision and more interference-resistant FBG fiber grating strain sensors, which are deployed on the surface of the measuring element. Thus, the segmented semi-submersible foundation model possesses both the integrity of a traditional integrated foundation model, enabling experimental simulation of an integrated foundation, and simultaneously satisfies the requirement for measuring the cross-sectional load of the foundation.

[0037] like Figure 1 As shown in the figure, the present invention provides a model test measurement method for the cross-sectional load of a semi-submersible floating foundation. This method employs a multi-body segmented structure, dividing the semi-submersible floating foundation into multiple independent sub-structure models. Connectors 2 are used to connect these sub-structure models, assembling them into a complete segmented model of the semi-submersible floating foundation. Figure 2 As shown.

[0038] like Figure 1 As shown, the substructure model includes one central substructure 4 and multiple side substructures 1. The substructures are designed as hollow shell structures, capable of holding weights to adjust the structural mass and inertia distribution. The substructure shell extends into an extended shell at the cross-section. After connecting to the connector 2, the extended shell covers the connector 2 to reduce changes in the original topological shape of the first and second floats at the measured cross-section. The extended shell is equipped with a 3-living body and a detachable shell 3 (including, for example...). Figure 1 (3a, 3b, 3c) facilitates the threaded assembly of connector 2 with the substructure. The extended housing is made of resin glass to enable visualization of the connectors inside the extended housing.

[0039] Central substructure 4 (e.g.) Figure 1 4d) includes a central column and a first pontoon. The central column is connected and fixed by the first pontoon. There are multiple first pontoons. The number of first pontoons is consistent with the number of side substructures 1.

[0040] Side substructure 1 (including such as Figure 1 1a, 1b, and 1c) include side columns and a second buoy, with the side columns being connected and fixed by the second buoy.

[0041] Both the first and second pontoons are provided with cross-sections, which are perpendicular to the central axes of the first and second pontoons, respectively. The cross-sections are sealed and thickened, and screw holes are reserved for connection with the connector 2.

[0042] Preferably, the number of side substructures 1 is 3, and the number of first floats is also 3.

[0043] like Figure 1 As shown, connector 2 (including as follows) Figure 1 2a, 2b, and 2c) are the connecting components for assembling the floating foundation segment model, and also the FBG fiber optic strain sensor 5 (including, for example, Figure 3The measuring carriers in sections 5a, 5b, and 5c) use connector 2 as the measuring element for the cross-sectional load of the semi-submersible floating foundation. The measuring element is positioned with the cross-section to be measured. Connector 2 includes a cylinder 6 and end flanges 7. The cylinder 6 is a hollow cylinder with a uniform cross-section. Both ends of the cylinder 6 are end flanges 7. The shape of the end flanges 7 is consistent with the cross-section of the first and second floats. The end flanges 7 have pre-drilled bolt holes 8 for connection with the cross-section.

[0044] Preferably, the connector 2 is made of metal, and the number of connectors 2 is consistent with the number of side substructures 1, both being 3. The length-to-diameter ratio of the cylinder 6 of the connector 2 is greater than 5.

[0045] The measurement method is based on strain measurement, using FBG fiber grating strain sensors 5 to measure the load on the cross-section of the semi-submersible floating foundation. The cross-sectional load includes the axial force and bending moment of the cross-section. The FBG fiber grating strain sensors 5 are arranged on the surface of the measuring element. The FBG fiber grating strain sensors 5 are arranged along the axial direction of the cylinder 6 on the cross-section to be measured, at the endpoints of the horizontal and vertical neutral axes of the cross-section to be measured. The FBG fiber grating strain sensors 5 are fixedly bonded to the outer surface of the cylinder 6 with waterproof and insulating rigid adhesive. The cross-section to be measured is the cross-section located at the midpoint of the central axis of the cylinder 6, and a total of 4 FBG fiber grating strain sensors 5 are used.

[0046] The FBG fiber grating strain sensor 5 monitors temperature strain, installation strain, and load strain. Installation strain is removed by zeroing the strain value before the test. Temperature strain is solved using the temperature compensation method and / or the strain difference method. The load on the cross-section is calculated using the load strain.

[0047] ε=ε load +ε inst +ε temp

[0048] ε represents the strain monitored by the FBG fiber grating strain sensor 5. load ε is the strain caused by the cross-sectional load. inst ε represents the installation strain caused by sensor installation. temp This refers to the temperature strain caused by ambient temperature.

[0049] The temperature compensation method involves setting up one or more temperature compensation plates. These temperature compensation plates utilize FBG fiber optic strain sensors 5 of the same specifications. The temperature compensation plates are attached to a piece of material of the same material as the component being measured but do not participate in deformation, and are subjected to the same temperature conditions as the component. The strain monitored by the temperature compensation plates is the temperature strain ε of the FBG fiber optic strain sensor 5. temp This allows us to calculate the load on the cross section, specifically:

[0050]

[0051] Where, ε load，i Let F be the load strain of the i-th FBG fiber grating strain sensor, i = a, b, c, d, where a and b are the FBG fiber grating strain sensors at the upper endpoints of the vertical neutral axis, and c and d are the FBG fiber grating strain sensors at the upper endpoints of the horizontal neutral axis. N M is the axial force on the cylindrical cross-section of the connector. hori M is the horizontal bending moment component of the cylindrical cross-section of the connector. vert Let E be the bending moment component in the vertical direction of the cylindrical cross-section of the connector, A be the elastic modulus of the connector, W be the cross-sectional area of ​​the cylindrical cross-section of the connector, and W be the section modulus of the cylindrical cross-section of the connector.

[0052] The strain difference method utilizes the fact that the temperature strain of the FBG fiber grating strain sensor 5 is the same on the same cross-section to be measured, thereby solving for the bending moment value of that cross-section.

[0053]

[0054]

[0055] Where, ε i The strain data of the i-th FBG fiber grating strain sensor 5 after initial value reset to zero, ε load,i Let M be the load strain of the i-th FBG fiber grating strain sensor 5, i = a, b, c, d, where a and b are the FBG fiber grating strain sensors 5 at the upper endpoint of the vertical neutral axis, and c and d are the FBG fiber grating strain sensors 5 at the upper endpoint of the horizontal neutral axis. hori M is the horizontal bending moment component of the cylindrical cross-section of the connector. vert Let E be the bending moment component in the vertical direction of the cylindrical cross-section of the connector, and W be the section modulus of the connecting component.

[0056] This invention addresses the problem that current wind turbine model tests primarily use integrated foundation models to simulate semi-submersible floating wind turbine foundations. While the integrated foundation model method can obtain the overall response characteristics of the foundation, it cannot capture the local structural internal forces. This invention utilizes a multi-body segmented structure to simulate the wind turbine foundation. At the cross-section of interest / to be measured, the integrated foundation is divided into multi-body structures. Elastic components are used to reassemble these multiple substructures into a "one-body" foundation platform. Simultaneously, based on strain measurement, the elastic components are used as strain measurement carriers to measure the cross-sectional strain of the components, thereby obtaining the cross-sectional internal forces of the wind turbine foundation structure. By restoring the geometric topology and mechanical properties of the integrated foundation model using a multi-body segmented model, and applying the stress-strain linear elasticity theory of the elastic components, this invention can simultaneously simulate and measure the overall response and local internal force characteristics of the floating wind turbine foundation in the same test. This helps expand the research scope of wind turbine pool model tests, improves the research efficiency of floating wind turbines, and provides technical support for the safe design of floating wind turbines.

[0057] The present invention will now be described in detail with reference to preferred embodiments.

[0058] For the foundation structure of semi-submersible floating wind turbines, this invention proposes a test measurement method for the foundation cross-sectional load model based on FBG fiber grating sensing technology.

[0059] The technical solution of the present invention is as follows:

[0060] 1. Semi-submersible foundation segment model

[0061] The semi-submersible foundation segment model mainly consists of multiple foundation substructures and connectors.

[0062] The substructure is divided into a central substructure 4 and side substructures 1, depending on the number of semi-submersible foundation pontoons and the number of cross-sections to be measured. For structural symmetry, the number and position of the cross-sections to be measured on each pontoon must be consistent. Typically, a semi-submersible foundation consists of one central column and three or four side columns, which are connected and fixed to the central column by pontoons and cross braces. Using the position of the cross-section to be measured on the pontoon as a reference, and considering the length of the connector 2, the position of the substructure cross-section can be determined. The number of substructures in the semi-submersible foundation segment model should be greater than or equal to 4. For example, for a three-sided column, three-pontoon semi-submersible foundation, each pontoon has only one cross-section to be measured. Taking the cross-section to be measured as the section at the midpoint of the axis of connector 2, extending 1 / 2 the length of the connector to both sides of the pontoon, the position of the pontoon cross-section can be obtained. Using this position as a reference, the foundation is divided into one central substructure 4 (composed of a central column and part of the pontoons) and three side substructures 1 (composed of side columns and part of the pontoons), for a total of 4 substructures. The cross-section must be perpendicular to the central axis of the pontoon. The cross-section of the substructure must be sealed and thickened to prevent water from entering, and screw holes must be provided for connection with connector 2.

[0063] Connector 2 is a connecting component for assembling the floating foundation segment model and also serves as the measurement carrier for the FBG fiber grating strain sensor 5. The number of connectors 2 is greater than or equal to three, consistent with the number of cross-sections to be measured. Connector 2 consists of one hollow cylinder 6 with a uniform cross-section and two end flanges 7. Connector 2 is typically made of metal with sufficient material strength to ensure that the metal cylinder 6 does not undergo significant deformation during the experiment, thus maintaining the stability of the geometric topology of the semi-submersible foundation segment model. Furthermore, metal is a homogeneous, continuous, isotropic, and variable solid with stable mechanical properties, making it an excellent strain measurement carrier and beneficial for the FBG fiber grating strain sensor 5 to measure local strain. Additionally, the length-to-diameter ratio of the connector cylinder 6 should be greater than 5 to ensure that the stress-strain relationship of the measurement carrier conforms to the range of elastic theory. The metal cylinder 6 has end flanges 7 at both ends, with a shape consistent with the cross-section of the float, and pre-drilled bolt holes 8 for connection to the substructure cross-section.

[0064] In addition, the substructure should be a hollow shell structure to allow for the placement of weights inside to adjust the structural mass and inertia distribution. The substructure shell should extend beyond the cross-section, covering connector 2 after connection, thus minimizing changes in the original topological shape of the base segment model's pontoons at the test section. The shell extension length should be close to but less than half the length of connector 2, ensuring a narrow pre-reserved gap (usually about 1 cm wide) at the test section after the two substructures are assembled via connectors, preventing collisions between the extended shell structures due to minor deformations of the cylinder 6 of connector 2. For ease of installation, the extended shell should have a removable and detachable portion to facilitate threaded assembly between connector 2 and the substructure. After assembly, this extended shell portion should be reinstalled and fixed to the substructure. Typically, this portion of the shell can be made of resin glass, meeting the strength requirements of the base segment model while allowing visualization of the internal connectors, facilitating observation of test accidents such as strain sensor detachment.

[0065] 2. FBG fiber optic strain sensor layout and cross-sectional load calculation method

[0066] The FBG fiber grating strain sensor 5 measures strain by relying on the axial deformation of the strain gauge. It is a uniaxial strain sensor, supporting only the measurement of deformation in a single direction. The cross-section located at the midpoint of the central axis of the cylinder 6 of the connector 2 is the cross-section to be measured. To obtain the cross-sectional load of the cross-section, four FBG strain sensors need to be arranged along the axial direction of the cylinder 6 on the cross-section, located at the endpoints of the horizontal and vertical neutral axes of the cross-section. The strain sensors attached to the component under test are usually called working gauges.

[0067] The FBG fiber grating strain sensor 5 is fixedly bonded to the outer surface of the cylinder 6 of the connector 2 using waterproof and insulating rigid adhesive to ensure no relative slippage between the FBG fiber grating strain sensor 5, the adhesive, and the cylinder 6. Simultaneously, the metal connector, the FBG fiber grating strain sensor 5, and the rigid adhesive are all elastic materials, and the small deformations they undergo under load all conform to the range of linear elasticity theory. The strain of the FBG fiber grating strain sensor 5 can be simultaneously affected by load and temperature. Therefore, during the experiment, the strain of the sensor consists of three parts: temperature strain, installation strain, and load strain, i.e.:

[0068] ε=ε load +ε inst +ε temp (1)

[0069] In the formula, ε is the strain monitored by the FBG fiber grating strain sensor 5, ε load ε is the strain caused by the cross-sectional load. inst ε represents the installation strain caused by sensor installation.temp This refers to the temperature strain caused by ambient temperature.

[0070] For the sensor installation strain ε inst After the rigid adhesive has solidified, this portion of the strain no longer changes. Therefore, this effect can be eliminated by zeroing the strain values ​​before the test. After zeroing, the strain measured on the working piece only includes the cross-sectional load strain ε. load and temperature strain ε temp Two points. For four working pieces on the same cross-section to be measured, their ambient temperature can be considered the same, therefore the temperature strain of the four working pieces is the same. However, considering that the ambient temperature changes over time, simply zeroing the temperature cannot completely eliminate the influence of the environment on the strain. Generally, environmental strain can be considered using the following two methods:

[0071] Method 1: Temperature Compensation Method

[0072] This method requires at least one additional FBG fiber optic strain sensor 5 of the same specifications. This sensor is attached to a piece of material of the same material as the component being measured but does not participate in deformation, and is subjected to the same temperature conditions as the component being measured. This sensor is usually called a temperature compensation plate. The temperature compensation plate is only affected by the ambient temperature, and its monitored strain is ε. temp By removing the compensation plate data from the working plate data, the strain ε caused by the cross-sectional load can be obtained. load Based on the linear elastic theory of stress and strain, the strain in the cylindrical cross-section of the connector is generated by the superposition of axial force and bending moment on the cross-section, that is:

[0073]

[0074] In the formula, ε load，i Let F be the load strain of the i-th FBG fiber grating strain sensor 5, where i = a, b, c, d, a and b are the FBG fiber grating strain sensors 5 at the upper endpoint of the vertical neutral axis, and c and d are the FBG fiber grating strain sensors 5 at the upper endpoint of the horizontal neutral axis. N M is the axial force on the cylindrical cross-section of the connector. hori M is the horizontal bending moment component of the cylindrical cross-section of the connector. vert Let F be the bending moment component in the vertical direction of the cylindrical cross-section of the connector, E be the elastic modulus of the connector, A be the cross-sectional area of ​​the cylindrical connector, and W be the section modulus of the cylindrical connector. In formula (2), only F... N M hori and M vert The loads on the three cross sections are unknown. The load-strain values ​​ε of any three working sections on the cross section to be measured are... load Substituting into formula (2), the axial force and bending moment data of the cross section can be obtained.

[0075] Method 2: Strain Difference Method

[0076] As mentioned earlier, after the initial value of the working piece is returned to zero, the strain measured by the working piece only includes the cross-sectional load strain ε. load and temperature strain ε temp Both conditions apply, and for the four working pieces on the same cross-section, the ambient temperature is the same, resulting in the same temperature strain. Considering that the four working pieces are located at the endpoints of the horizontal and vertical neutral axes of the cross-section, the strain of the working pieces after the initial values ​​are reset to zero can be expressed as:

[0077]

[0078] In the formula, ε i The strain data after the initial values ​​of the working pieces are reset to zero are given by i = a, b, c, d, where working pieces a, b and c, d are located at the endpoints of the vertical and horizontal neutral axes, respectively. Subtracting each pair of equations in formula (3) yields:

[0079]

[0080] Formula (4) contains only two unknown bending moment components. After the initial values ​​of any four working pieces on the cross section to be measured are zeroed, the strain is substituted into formula (4) to obtain the bending moment data of the cross section.

[0081] 3. Assembly method of semi-submersible foundation segment model

[0082] The assembly steps of the semi-submersible foundation segment model and the installation steps of the FBG fiber grating strain sensor 5 are as follows:

[0083] Step 1: Determine and mark the fixed tracks of the FBG fiber optic strain sensor 5. These tracks are generally located on the cross-section at the midpoint of the axis of the metal cylinder 6 of the connector 2, and parallel to the central axis of the connector 2. The FBG strain sensor 5 is a slender sensor; when marking the tracks, avoid any angle between the sensor's length direction and the central axis of the connector 2 to prevent measurement errors. To obtain the cross-sectional load, four fixed tracks need to be marked on each cylinder 6 of the connector 2. Each track is parallel to the axis of the cylinder 6, and the four tracks are located at the intersections of the horizontal and vertical neutral axes of the cylinder 6's cross-section with the cylinder surface, respectively. Figure 3 As shown in AA.

[0084] Step 2: Assemble the end flange 7 of connector 2 to the cross-section of the central substructure 4 using threads. When assembling with screws, ensure they are tightened securely to prevent relative movement during the test due to looseness between connector 2 and the substructure. This also prevents water from entering the substructure through loose screw holes, which could affect the experimental results. After completing the threaded assembly, apply waterproof adhesive around the screws and screw holes 8 to further prevent water seepage at the threaded connection.

[0085] Step 3: By assembling with connector 2, the central substructure 4 and the side substructure 1 can be assembled together. During assembly, ensure that the three axes are collinear, that is, the central axis of the float of the side substructure 1, the central axis of the float of the central substructure 4, and the central axis of connector 2 are collinear. At the same time, ensure that the central column axis of the central substructure 4 is coplanar with the side column axis of the side substructure 1.

[0086] Step 4: Use insulating adhesive to attach the FBG fiber grating strain sensor 5 to the preset track line of the cylinder 6 of the connector 2, ensuring that the sensor's trajectory coincides with the marked track line. Simultaneously, attach the wires connecting the strain gauge of the FBG fiber grating strain sensor 5 to the cylinder 6 to prevent deformation of the FBG fiber grating strain sensor 5 due to wire movement during the test. After the adhesive has cured, apply waterproof insulating adhesive to the entire surface of the cylinder of the connector to further ensure the waterproof performance of the FBG fiber grating strain sensor 5.

[0087] Step 5: After completing the assembly of the side substructure 1, the central substructure 4, the connector 2, and the FBG strain sensor 5, re-glu the living body and the detachable shell 3 to the ends of each substructure. At this point, the semi-submersible foundation segment model is assembled. According to the specific test requirements, anchor chains, fans, other motion and force sensors and other test equipment can be installed to carry out water tank model tests.

[0088] Before starting the formal test, it is necessary to clarify the calculation method of the cross-sectional load of the semi-submersible foundation. If the temperature compensation method is used, an FBG fiber optic strain sensor 5 of the same specification needs to be added. This sensor is attached to a piece of material of the same material as the component being tested but does not participate in the deformation, and is under the same temperature conditions as the component being tested (i.e., temperature compensation plate). If the strain difference method is used, this operation is not required.

[0089] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A model test measurement method for the cross-sectional load of a semi-submersible floating foundation, characterized in that, The method employs a multi-body segmented structure, dividing the semi-submersible floating foundation into multiple independent sub-structure models. These sub-structure models are connected using connectors to form a complete semi-submersible floating foundation segment model. The connectors serve as connecting components for assembling the floating foundation segment models and also as measurement carriers for FBG fiber grating strain sensors. The connectors act as measuring elements for the cross-sectional load of the semi-submersible floating foundation, with the cross-section to be measured positioned at the location of the measuring element. The measurement method is based on strain measurement, using the FBG fiber grating strain sensor to measure the load on the cross-section of the semi-submersible floating foundation. The cross-sectional load includes the axial force and bending moment of the cross-section, and the FBG fiber grating strain sensor is positioned on the surface of the measuring element.

2. The method as described in claim 1, characterized in that, The substructure model includes one central substructure and multiple side substructures, wherein, The central substructure includes a central column and a first pontoon. The central column is connected and fixed by the first pontoon. There are multiple first pontoons, and the number of the first pontoons is the same as the number of the side substructures. The side substructure includes a side column and a second buoy, wherein the side column is connected and fixed by the second buoy; Both the first and second pontoons have cross-sections, which are perpendicular to the central axes of the first and second pontoons, respectively. The cross-sections are sealed and thickened, and screw holes are provided for connection with the connector.

3. The method as described in claim 2, characterized in that, The substructure is configured as a hollow shell structure, and the hollow shell structure can hold weights to adjust the structural mass and inertia distribution. The outer shell of the substructure extends into an extended shell at the cross-section. After being connected to the connector, the extended shell covers the connector to reduce the change in the original topological shape of the first float and the second float at the cross-section to be measured.

4. The method as described in claim 3, characterized in that, The extended housing has a live part and a detachable part to facilitate the threaded assembly of the connector with the substructure. The extended housing is made of resin glass to make the internal connector visible.

5. The method as described in claim 4, characterized in that, The connector includes a cylinder and end flanges. The cylinder is a hollow cylinder with a uniform cross-section. The two ends of the cylinder are the end flanges. The shape of the end flanges is consistent with the cross-section of the first float and the second float. The end flanges are provided with screw holes for connection with the cross-section.

6. The method as described in claim 5, characterized in that, The connector is made of metal, and the number of connectors is consistent with the number of side substructures. The length-to-diameter ratio of the connector cylinder is greater than 5.

7. The method as described in claim 6, characterized in that, The FBG fiber grating strain sensors are arranged along the axial direction of the connecting cylinder on the cross-section to be measured. The FBG fiber grating strain sensors are arranged at the endpoints of the horizontal and vertical neutral axes of the cross-section to be measured. The FBG fiber grating strain sensors are fixedly bonded to the outer surface of the connecting cylinder by waterproof and insulating rigid adhesive. The cross-section to be measured is the cross-section where the midpoint of the central axis of the connecting cylinder is located. The number of FBG fiber grating strain sensors is 4.

8. The method as described in claim 7, characterized in that, The strain monitored by the FBG fiber grating strain sensor includes temperature strain, installation strain, and load strain. The installation strain is removed by zeroing the strain value before the test. The temperature strain is solved using the temperature compensation method and / or the strain difference method. The load on the cross-section is solved using the load strain. For monitoring strain using FBG fiber grating strain sensors, The load strain caused by the cross-sectional load, Installation strain caused by sensor installation. This refers to the temperature strain caused by ambient temperature.

9. The method as described in claim 8, characterized in that, The temperature compensation method employs one or more temperature compensation plates, each using an FBG fiber optic strain sensor of the same specifications. The temperature compensation plate is attached to a piece of material of the same material as the component being tested but does not participate in deformation, and is subjected to the same temperature conditions as the component. The strain monitored by the temperature compensation plate is the temperature strain of the FBG fiber optic strain sensor. The load on the cross section is: in, For the first i Load strain of an FBG fiber grating strain sensor , a and b An FBG fiber grating strain sensor located at the upper end of the vertical neutral axis. c and d An FBG fiber optic strain sensor located at the upper end of the horizontal neutral axis. The axial force is the cross-sectional area of ​​the cylindrical connector. The bending moment component in the horizontal direction is the cross-section of the cylindrical connector. The bending moment component in the vertical direction is the cross-section of the cylindrical component of the connector. E The elastic modulus of the connector, A The cross-sectional area of ​​the connecting cylinder is given. W is the section modulus of the bending moment of the cylindrical cross-section of the connector.

10. The method as described in claim 8, characterized in that, The strain difference method utilizes the fact that the temperature strain of the FBG fiber grating strain sensors on the same cross-section under test is the same, thereby solving for the bending moment value of that cross-section. in, The first time after the initial value is reset to zero i Strain data from an FBG fiber grating strain sensor For the first i Load strain of an FBG fiber grating strain sensor , a and b An FBG fiber grating strain sensor located at the upper end of the vertical neutral axis. c and d An FBG fiber optic strain sensor located at the upper end of the horizontal neutral axis. The bending moment component in the horizontal direction is the cross-section of the cylindrical connector. The bending moment component in the vertical direction is the cross-section of the cylindrical component of the connector. E The elastic modulus of the connector, W is the section modulus of the bending moment of the cylindrical cross-section of the connector.

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