Fatigue damage prediction method and system for floating platform based on actually measured sea condition data

Abstract

The invention relates to the technical field of offshore oil engineering, and provides a floating platform fatigue damage prediction method and system based on actually measured sea condition data, and the method comprises the steps: building an overall finite element model of a floating platform; determining a stress transfer function of a local structure of each fatigue sensitive position in the floating platform under different loading conditions under different wave direction angles; combining the stress transfer function with wave spectrums of different short-term actually-measured sea conditions to obtain fatigue stress energy spectrum density functions under different actually-measured sea conditions; determining fatigue damage values under different short-term actual measurement sea conditions according to the fatigue stress energy spectrum density functions under different actual measurement sea conditions and the SN curve, and constructing a fatigue damage array; the fatigue damage array is searched according to the current loading working condition of the floating platform and the short-term actually-measured sea condition data and the wave direction angle of each sea condition duration recorded in real time, the fatigue damage value of the local structure of the fatigue sensitive position in the corresponding short-term actually-measured sea condition recording time period is obtained, and the prediction result is more accurate and reliable.

Description

Technical Field

[0001] The present invention relates to the field of offshore oil engineering technology, and in particular to a method and system for predicting fatigue damage of a floating platform based on measured sea condition data. Background Art

[0002] For offshore oil floating platforms in service, environmental loads (waves, wind, currents, etc.) cause the floating platforms to be under alternating loads for a long time, which will cause fatigue problems for the floating platforms. In the field of marine engineering, regular inspections (annual inspections, special inspections, docking inspections, etc.) and maintenance measures are used to avoid structural fatigue failures. However, if the real-time fatigue damage of the structure cannot be quantified relatively accurately, especially for offshore oil floating platforms in service in the middle and late stages, it is difficult to assess the remaining fatigue life of the structure, and then the integrity and reliability of the offshore oil floating platforms cannot be guaranteed. In addition, for some special moments that may have an adverse effect on fatigue (such as abnormal waves and typhoons), conventional numerical calculations cannot count such isolated time fatigue damage.

[0003] The floating platform condition monitoring and evaluation methods provided in the prior art are mainly based on the numerical simulation of sensor data to achieve fatigue life analysis. For example, based on the hull structure strain data collected by the sensor, the mechanical properties and fatigue life and other characteristic parameters of the hull structure are evaluated in real time; for example, the fatigue analysis method of the inner turret mooring system based on measured data uses various monitoring methods to obtain position, load and environmental data, and calculates and evaluates the remaining life of the inner turret mooring system through empirical formulas and algorithms. Through the analysis of the above fatigue life analysis methods, it can be seen that the fatigue life analysis based on the numerical simulation method of sensor data can only obtain fatigue life results at individual positions. If you want to obtain more position results, you need to increase the number of sensor arrangements, and the difficulty of arrangement will increase accordingly. And as the use time increases, the sensor will also be damaged, and the accuracy of the returned data will decrease. In addition, this type of analysis method also has certain limitations in focusing on the fatigue life of the entire floating platform and the fatigue life of multiple important structures. Summary of the invention

[0004] In view of the above problems, the present invention is proposed to provide a method and system for predicting fatigue damage of a floating platform based on measured sea condition data, which overcomes the above problems or at least partially solves the above problems.

[0005] One aspect of the present invention provides a method for predicting fatigue damage of a floating platform based on measured sea condition data, the method comprising: Establish the overall finite element model of the floating platform; Determine the stress transfer function of the local structure at each fatigue-sensitive location in the floating platform under different loading conditions at all specified wave angles within the preset wave frequency range ; The obtained stress transfer functions are Wave spectra of different short-term measured sea conditions Combination, the fatigue stress energy spectrum density function under different measured sea conditions is obtained : ,in, is the wave direction angle, is the wave frequency, For the meaningful wave height, It is a zero-crossing cycle; According to the fatigue stress energy spectrum density function under different measured sea conditions and the preset SN curve, the fatigue damage values ​​under different short-term measured sea conditions are determined, and the fatigue damage array D (i, n, , , ), where i represents different fatigue sensitive position local structures, n represents different loading conditions, and Different wave angles, , ) represent different short-term measured sea conditions; When fatigue damage prediction is performed on the target floating platform to be predicted, the short-term measured sea condition data of each preset sea condition duration in the sea area is recorded in real time ( , ) and wave angle; According to the current loading condition of the target floating platform and the recorded short-term measured sea state data for each preset sea state duration ( , ) and wave direction angle to find the fatigue damage array to obtain the fatigue damage value of the local structure at each fatigue-sensitive position of the target floating platform during the corresponding short-term measured sea condition record period.

[0006] Furthermore, the method further comprises: Obtain the fatigue damage values ​​of all short-term measured sea condition record periods of the local structure at any fatigue sensitive position of the target floating platform during its service life and perform linear addition to obtain the fatigue damage prediction result of the local structure at the current fatigue sensitive position, and / or The remaining fatigue life of the local structure at the current fatigue sensitive position is calculated based on the fatigue damage prediction result of the local structure at the current fatigue sensitive position and the preset life limit.

[0007] Furthermore, the method of determining fatigue damage values ​​under different short-term measured sea conditions according to the fatigue stress energy spectrum density function under different measured sea conditions and the preset SN curve includes: Calculate the corresponding fatigue stress probability density function based on the fatigue stress energy spectrum density function under different measured sea conditions : Among them, S is the fatigue stress envelope corresponding to the short-term measured sea conditions; = , is the zero-order spectral moment of the fatigue stress energy spectral density function corresponding to the short-term measured sea conditions; Among them, the nth order spectral moment of the fatigue stress energy spectral density function is The calculation is as follows: ; According to the fatigue stress probability density function under different measured sea conditions Combined with SN curve , and the fatigue damage under different measured sea conditions is obtained: is the fatigue damage occurring in the i-th short-term measured sea condition, To describe the preset physical parameters of the SN curve, is the duration of the short-term sea condition, is the zero-crossing frequency of the stress response, , is the second-order spectral moment of the fatigue stress energy spectral density function corresponding to the short-term measured sea conditions, is the probability density function of fatigue stress.

[0008] Furthermore, the establishing of the overall finite element model of the floating platform by the finite element analysis method comprises: The floating platform structure model is established through the finite element analysis method. The local structure models of fatigue-sensitive positions are grouped according to the characteristics of the floating platform. The weight of each profession is loaded according to the spectral fatigue design condition, and the boundary constraints are set to obtain the overall finite element model.

[0009] Further, according to the current loading condition of the target floating platform and the recorded short-term measured sea state data ( , ) and wave direction angle before searching the fatigue damage array, the method further comprises: Searching a preset wave direction angle correction corresponding relationship table according to the wave direction angle in the currently recorded short-term measured sea state data to obtain a wave direction angle correction value corresponding to the wave direction angle in the currently recorded short-term measured sea state data, wherein the wave direction angle correction corresponding relationship table includes a corresponding relationship between a wave direction angle range interval of the measured sea state data and a wave direction angle in a fatigue damage array; According to the fatigue damage array The current recorded short-term measured sea state data is Round up to get Correction value; According to the fatigue damage array The current recorded short-term measured sea state data is Round up to get Correction value.

[0010] Furthermore, after obtaining the fatigue damage value of the local structure at each fatigue-sensitive position of the target floating platform during the corresponding short-term measured sea condition recording period, the method further includes: According to the structural form of the local structure at each fatigue-sensitive position, when the manufacturing tolerance of the local structure at the fatigue-sensitive position exceeds the tolerance implied by the SN curve, the fatigue damage value corresponding to the local structure at the current fatigue-sensitive position is multiplied by the stress concentration factor corresponding to the structural form of the local structure at the current fatigue-sensitive position for correction.

[0011] Further, the overall finite element model of the floating platform includes a wet surface model, an overall structure model, a mass model and a Morrison model; The wet surface model contains all the external contour information of the floating platform below the water plane; The mass model is used to load the weight of the floating platform, cabin loading and the weight of the equipment carried; The overall structural model is used for the meshing of the floating platform structure and the application of boundary conditions; The Morrison model is used to calculate the stress conditions of small-scale structural components below the waterline in waves.

[0012] Another aspect of the present invention further provides a floating platform fatigue damage prediction system based on measured sea condition data, the system comprising: A model building module, used to build an overall finite element model of the floating platform by using a finite element analysis method; The first stress analysis module is used to analyze the overall finite element model using a preset frequency domain hydrodynamic analysis software to determine the stress transfer function of the local structure of each fatigue sensitive position in the floating platform under different loading conditions at all specified wave direction angles within a preset wave frequency range. ; The second stress analysis module is used to obtain the stress transfer function Wave spectra of different short-term measured sea conditions Combination, the fatigue stress energy spectrum density function under different measured sea conditions is obtained : ,in, is the wave direction angle, is the wave frequency, For the meaningful wave height, It is a zero-crossing cycle; The fatigue damage analysis module is used to determine the fatigue damage values ​​under different short-term measured sea conditions according to the fatigue stress energy spectrum density function under different measured sea conditions and the preset SN curve, and to construct the fatigue damage array D (i, n, , , ), where i represents different fatigue sensitive position local structures, n represents different loading conditions, and Different wave angles, , ) represent different short-term measured sea conditions; The sea condition monitoring module is used to record the short-term measured sea condition data of each preset sea condition duration in the sea area in real time when fatigue damage prediction is performed on the target floating platform to be predicted. , ) and wave angle; The fatigue damage prediction module is used to predict the fatigue damage of the target floating platform based on the current loading condition of the target floating platform and the short-term measured sea state data ( , ) and wave direction angle to find the fatigue damage array to obtain the fatigue damage value of the local structure at each fatigue-sensitive position of the target floating platform during the corresponding short-term measured sea condition record period.

[0013] Furthermore, the system further comprises: The fatigue damage statistics module is used to obtain the fatigue damage values ​​of all short-term measured sea condition record periods of the local structure at any fatigue sensitive position of the target floating platform during its service life and perform linear addition to obtain the fatigue damage prediction results of the local structure at the current fatigue sensitive position, and / or The remaining fatigue life statistics module is used to calculate the remaining fatigue life of the local structure at the current fatigue sensitive position based on the fatigue damage prediction result of the local structure at the current fatigue sensitive position and the preset life span.

[0014] Another aspect of the present invention provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein when the processor executes the computer program, the steps of the above-mentioned method for predicting fatigue damage of a floating platform based on measured sea condition data are implemented.

[0015] The floating platform fatigue damage prediction method and system based on measured sea condition data provided by the embodiment of the present invention can evaluate the cumulative fatigue damage results of the floating platform in a certain period of time in real time by importing the measured data of the field environment. Compared with the conventional method of evaluating the cumulative fatigue damage by only using the previous wave dispersion data, more accurate fatigue damage prediction results can be obtained, which has important guiding significance for the inspection and maintenance of the floating platform. At the same time, the present invention can be applied to the fatigue damage results of the floating platform under the "isolated severe sea conditions" at a special moment that cannot be evaluated by conventional calculations, effectively improving the safety and reliability of the floating platform during its in-place period.

[0016] In addition, the floating platform fatigue damage prediction method and system based on measured sea condition data provided by the embodiment of the present invention is relatively simple and reasonable in engineering application, and a miniaturized digital twin structure array is constructed to facilitate real-time calculation on the floating platform, which does not bring about a huge amount of calculation, improves calculation efficiency, simplifies the analysis process, and meets the timeliness of engineering projects. Moreover, the method of the present invention does not require the installation of real-time data collection sensors, saving engineering implementation costs and later equipment maintenance costs.

[0017] The above description is only an overview of the technical solution of the present invention. In order to more clearly understand the technical means of the present invention, it can be implemented according to the contents of the specification. In order to make the above and other purposes, features and advantages of the present invention more obvious and easy to understand, the specific implementation methods of the present invention are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Various other advantages and benefits will become apparent to those of ordinary skill in the art by reading the detailed description of the preferred embodiments below. The accompanying drawings are only for the purpose of illustrating the preferred embodiments and are not to be considered as limiting the present invention. Moreover, the same reference symbols are used throughout the accompanying drawings to represent the same components. In the accompanying drawings:

[0019] Figure 1 A flowchart of a method for predicting fatigue damage of a floating platform based on measured sea condition data provided by an embodiment of the present invention; Figure 2 A schematic diagram of a 4-dimensional array of fatigue damage at position i provided by an embodiment of the present invention; Figure 3 A flowchart of a method for predicting fatigue damage of a floating platform based on measured sea condition data provided by a specific embodiment of the present invention; Figure 4 This is a structural block diagram of a floating platform fatigue damage prediction system based on measured sea condition data proposed in an embodiment of the present invention. DETAILED DESCRIPTION

[0020] The exemplary embodiments of the present disclosure will be described in more detail below with reference to the accompanying drawings. Although the exemplary embodiments of the present disclosure are shown in the accompanying drawings, it should be understood that the present disclosure can be implemented in various forms and should not be limited by the embodiments set forth herein. On the contrary, these embodiments are provided to enable a more thorough understanding of the present disclosure and to fully convey the scope of the present disclosure to those skilled in the art.

[0021] Those skilled in the art will appreciate that, unless otherwise stated, the singular forms "a", "an", "said" and "the" used herein may also include plural forms. It should be further understood that the term "comprising" used in the specification of the present invention refers to the presence of the features, integers, steps, operations, elements and / or components, but does not exclude the presence or addition of one or more other features, integers, steps, operations, elements, components and / or groups thereof.

[0022] Those skilled in the art will understand that, unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as generally understood by those skilled in the art in the art to which the present invention belongs. It should also be understood that terms such as those defined in general dictionaries should be understood to have meanings consistent with the meanings in the context of the prior art, and will not be interpreted with idealized or overly formal meanings unless specifically defined.

[0023] Figure 1 The flowchart of a method for predicting fatigue damage of a floating platform based on measured sea state data according to an embodiment of the present invention is schematically shown. Figure 1 The method for predicting fatigue damage of a floating platform based on measured sea condition data according to an embodiment of the present invention specifically comprises the following steps:

[0024] S11. Establishing an overall finite element model of the floating platform. Specifically, the overall finite element model of the floating platform may be established by a finite element analysis method.

[0025] In an embodiment of the present invention, establishing an overall finite element model of a floating platform by a finite element analysis method specifically includes: establishing a floating platform structural model by a finite element analysis method, grouping local structural models of fatigue-sensitive positions according to characteristics of the floating platform, loading various professional weights according to spectral fatigue design conditions, setting boundary constraints, and obtaining an overall finite element model.

[0026] Specifically, according to the finite element calculation software model grouping numbering rules and modeling methods, combined with the characteristics of floating platforms, unified modeling grouping rules are formulated for the number, name and working conditions of different fatigue-sensitive positions. For example: horizontal truss toe area, structural mutation area, bilge fatigue area of ​​ship-type floating structures, unconventional thick plates in the area where the theoretical line difference of full penetration weld plate thickness exceeds 0.3t, module pier bracket toe area, fairlead reinforcement area, semi-submersible floating platform lower buoy and column connection area, cylindrical floating platform heave plate area, tension leg type floating platform tension tendon reinforcement area, etc. Under the finite element modeling software numbering rules, English and continuous digital numbers can be used in sections, and English and numbers are given corresponding model feature meanings respectively to group the required structures. The groups can be divided according to the horizontal height of the structure, such as girder2400, girder15000, etc.; they can be grouped and numbered according to the typical names of local structures, such as fairlead9000, bracing4800, node9000, bktoe1, etc.; they can be grouped and numbered according to the working condition category, such as transit12, operate22, ballast18, etc. Then, the floating platform structure model is established, and the grouping of local structure models at each fatigue-sensitive position is completed according to the grouping rules of step one. The weights of various professions are loaded according to the spectral fatigue design conditions, and the boundary constraints are set to obtain the overall finite element model. Under the action of all loads, the finite element model of the whole ship should be basically in a state of dynamic equilibrium. Furthermore, in order to avoid the rigid body motion of the overall structural model, six degrees of freedom static constraints must be applied.

[0027] Furthermore, in order to improve the simulation accuracy and calculation efficiency, the overall model can be decomposed and sub-models can be established based on the unified modeling rules for the local reinforcement areas that need to be calculated. Each sub-model can be modeled in parallel, and all sub-models use the same overall coordinate system direction and coordinate origin. The sub-model boundary condition loading should be extracted from the same position of the overall model. The sub-model can be divided into fine grids, and the rest of the overall model can maintain a relatively large size grid.

[0028] S12. Determine the stress transfer function of the local structure at each fatigue-sensitive position in the floating platform under different loading conditions at all specified wave angles within the preset wave frequency range. Specifically, the overall finite element model can be analyzed using a preset frequency domain hydrodynamic analysis software to determine the stress transfer function of the local structure at each fatigue sensitive position in the floating platform under different loading conditions at all specified wave angles within the preset wave frequency range. .

[0029] In the embodiment of the present invention, the overall finite element model file completed in step S11 is imported into the frequency domain hydrodynamic calculation software, the loading condition of the floating platform is adjusted, and the wave load transfer function of all wave directions within the range of 4 s to 36 s (such as within the range of 0°-315°, not more than 45° interval) is calculated. , and then calculate the stress transfer function Specifically, by calculating the wave loads and stresses of the local structure at each fatigue-sensitive position at a series of wave frequencies and wave angles, the stress results are the stresses of the local structure at the fatigue-sensitive position at different wave angles. The stress transfer function at .

[0030] In a specific example, the complex solutions of wave loads and stresses under a set of regularly specified wave angles with equal wave direction intervals between 0° and 360° can be calculated, where the real part corresponds to the regular wave crest at the horizontal coordinate 0, and the imaginary part corresponds to the regular wave zero-crossing point at the horizontal coordinate 0.

[0031] S13, respectively obtain the stress transfer function Wave spectra of different short-term measured sea conditions Combination, the fatigue stress energy spectrum density function under different measured sea conditions is obtained , can be obtained by the following formula ,in, is the wave direction angle, is the wave frequency, For the meaningful wave height, It is a zero-crossing cycle.

[0032] The short-term measured sea condition can be selected as a short-term sea condition with a sea condition duration of 3 hours. Specifically, the stress transfer function obtained in step S12 is Short-term sea conditions lasting 3 hours with unacceptable sea conditions ( , ) Wave spectrum The fatigue stress energy spectral density function under different measured sea conditions is obtained by combining the above two parameters.

[0033] S14, determine the fatigue damage values ​​under different short-term measured sea conditions according to the fatigue stress energy spectrum density function under different measured sea conditions and the preset SN curve, and construct a fatigue damage array D (i, n, , , ), where i represents different fatigue-sensitive local structures, n represents different loading conditions, and Different wave angles, , ) represents different short-term measured sea conditions. The strain damage array D (i, n, , , ) represents the fatigue sensitivity of any fatigue sensitive point i in load condition n Angular wave direction corresponds to significant wave height and zero-crossing cycles Fatigue damage under sea conditions forms a 5-dimensional array of fatigue damage results.

[0034] Among them, the SN curve is a curve with the fatigue strength of the standard specimen of the material as the vertical coordinate and the logarithm of the fatigue life lgN as the horizontal coordinate. It represents the relationship between the fatigue strength and fatigue life of the standard specimen under certain cycle characteristics, also known as the stress-life curve.

[0035] In the embodiment of the present invention, multiple analysis and calculation are performed to calculate the different positions i, different loading conditions n, and different wave directions. , different short-term measured sea conditions ( , ) are combined to obtain a 5-dimensional array D (i, n, , , ) numerical table, where the fatigue damage at position i is a 4-dimensional array, such as Figure 2 shown. Figure 2 Only the fatigue damage arrays of position i under two loading conditions (loading condition 1 and loading condition 2) are shown in FIG. It is understandable that the present invention is not limited to two loading conditions. The fatigue damage 3D array corresponding to position i under each loading condition n includes the fatigue damage arrays of different wave directions. , different short-term measured sea conditions ( , ) under fatigue damage.

[0036] S15. When fatigue damage prediction is performed on the target floating platform to be predicted, the short-term measured sea condition data of each preset sea condition duration in the sea area shall be recorded in real time ( , ) and wave angle.

[0037] When fatigue damage prediction is performed on a floating platform in service, the short-term sea conditions and wave direction of the sea area are recorded in real time every 3 hours. The signal data is transformed by Fourier transform to obtain multiple wave direction information as shown in Table 1. , wave height and cycle Real-time sea condition data table.

[0038] Table 1 About wave direction , wave height and cycle Real-time sea condition data table S16, according to the current loading condition of the target floating platform and the recorded short-term measured sea condition data of each preset sea condition duration ( , ) and wave direction angle to find the fatigue damage array to obtain the fatigue damage value of the local structure at each fatigue-sensitive position of the target floating platform during the corresponding short-term measured sea condition record period.

[0039] In an optional embodiment of the present invention, the method for predicting fatigue damage of a floating platform based on measured sea condition data further includes: obtaining fatigue damage values ​​of all short-term measured sea condition record periods of a local structure at any fatigue sensitive position of the target floating platform during service and performing linear addition to obtain fatigue damage prediction results of the local structure at the current fatigue sensitive position. In this embodiment, according to the linear cumulative damage theory, the fatigue damage return values ​​of the local structure area at the same fatigue sensitive position are linearly added to obtain the fatigue damage prediction results of the structure position during the service period of the platform.

[0040] In an optional embodiment of the present invention, the method for predicting fatigue damage of a floating platform based on measured sea condition data further includes: obtaining fatigue damage values ​​of all short-term measured sea condition record periods of a local structure at any fatigue sensitive position of the target floating platform during its service life and performing linear addition to obtain fatigue damage prediction results of the local structure at the current fatigue sensitive position, and calculating the remaining fatigue life of the local structure at the current fatigue sensitive position based on the fatigue damage prediction results of the local structure at the current fatigue sensitive position and a preset life span. In this embodiment, according to the linear cumulative damage theory, the fatigue damage return values ​​of the local structure area at the same fatigue sensitive position are linearly added to obtain the fatigue damage prediction results of the structural position at the platform service life.

[0041] The present invention combines the marine environmental condition monitoring data (wave direction every 3 hours) , Youyi Bogao , zero-crossing period ) can query the fatigue damage of any fatigue sensitive point and accumulate it with the historical fatigue damage data to obtain the actual fatigue damage value during the service life and the corresponding remaining fatigue life.

[0042] In the embodiment of the present invention, the short-term sea condition data recorded in Table 1 is returned to the fatigue damage array obtained in step S14, and a data table of fatigue damage values ​​of a certain local structure i in the recorded sea condition every 3 hours can be mapped. Furthermore, according to the linear cumulative damage theory, the fatigue damage return values ​​of the same structural area obtained are linearly added to obtain the approximate actual results of fatigue damage at the structural position during the service life of the platform, as shown in Tables 2 to 4.

[0043] Table 2 Fatigue damage value data of a local structure i every 3 hours in the sea conditions recorded on May 16, 2024 Table 3 Fatigue damage value data of a local structure i every 3 hours in the sea conditions recorded on May 17, 2024 Table 4 Fatigue damage value data of a local structure i every 3 hours in the sea conditions recorded on May 19, 2024 The floating platform fatigue damage prediction method based on measured sea condition data provided by the embodiment of the present invention can evaluate the cumulative fatigue damage results of the floating platform in a certain period of time in real time by importing the measured data of the field environment. Compared with the conventional method of evaluating the cumulative fatigue damage by only using the previous wave dispersion data, it can obtain more accurate fatigue damage prediction results, which has important guiding significance for the inspection and maintenance of the floating platform. At the same time, the present invention can be applied to the fatigue damage results of the floating platform under "isolated severe sea conditions" at certain special moments that cannot be predicted by conventional calculations, effectively improving the safety and reliability of the floating platform during its in-place period.

[0044] The floating platform fatigue damage prediction method based on measured sea condition data provided by the embodiment of the present invention is also applicable to the prediction of the floating platform fatigue damage results under "isolated severe sea conditions" at certain special moments. For some special events that may have an adverse effect on fatigue, such as abnormal waves, typhoons, etc., the impact of the special event on structural fatigue damage can be mapped according to steps S11 to S16 of the present invention by real-time recording of short-term sea condition data of special isolated events.

[0045] In one embodiment of the present invention, the step S14 determines the fatigue damage value under different short-term measured sea conditions according to the fatigue stress energy spectrum density function under different measured sea conditions and the preset SN curve, and specifically includes the following steps not shown in the accompanying drawings: S141. Calculate the corresponding fatigue stress probability density function based on the fatigue stress energy spectrum density function under different measured sea conditions .

[0046] In this embodiment, the fatigue stress envelope of any short-term sea condition is assumed to be Rayleigh distributed, and the 0th order moment m0 ​​of the fatigue stress envelope spectral density function is taken as the variance of the stress envelope Rayleigh distribution, and the apparent zero-crossing frequency f0 is calculated by the 0th order moment m0 ​​and the 2nd order moment m2 of the fatigue stress envelope spectral density function, then the Rayleigh distribution function of the fatigue stress envelope (the difference between adjacent stress peaks and valleys) of any 3-hour short-term sea condition can be obtained: Among them, S is the fatigue stress envelope corresponding to the short-term measured sea conditions; = , is the zero-order spectral moment of the fatigue stress energy spectral density function corresponding to the short-term measured sea conditions; Among them, the nth order spectral moment of the fatigue stress energy spectral density function is The calculation is as follows: ; S142, fatigue stress probability density function under different measured sea conditions Combined with SN curve , and the fatigue damage under different measured sea conditions is obtained: is the fatigue damage occurring in the i-th short-term measured sea condition, To describe the preset physical parameters of the SN curve, is the duration of the short-term sea condition, is the zero-crossing frequency of the stress response, , is the second-order spectral moment of the fatigue stress energy spectral density function corresponding to the short-term measured sea conditions, is the fatigue stress probability density function, It is the fatigue stress envelope corresponding to the short-term measured sea conditions.

[0047] In an embodiment of the present invention, according to the current loading condition of the target floating platform and the short-term measured sea condition data ( , ) and wave angle before searching the fatigue damage array, it also includes , The step of correcting the measured data according to the wave direction angle and the wave direction angle value standard. Specifically, it includes: searching the preset wave direction angle correction corresponding relationship table according to the wave direction angle in the currently recorded short-term measured sea state data to obtain the wave direction angle correction value corresponding to the wave direction angle in the currently recorded short-term measured sea state data, wherein the wave direction angle correction corresponding relationship table includes the corresponding relationship between the wave direction angle range interval of the measured sea state data and the wave direction angle in the fatigue damage array; according to the wave direction angle in the fatigue damage array The current recorded short-term measured sea state data is Round up to get Correction value; according to the fatigue damage array The current recorded short-term measured sea state data is Round up to get Correction value.

[0048] In a specific example, the wave direction angle of the short-term sea conditions in the sea area is recorded in real time every 3 hours. , wave height Sum wave period The three-dimensional array A ( , , )In mapping the fatigue damage five-dimensional array D(i, n, , , ) process, , , The mapping value should be modified. The specific examples are as follows: (1) Wave direction angle of the project’s measured sea condition data The interval should be consistent with the wave direction interval calculated in step 3. For examples of the wave direction angle correction range, please refer to the wave direction angle correction correspondence table 5.

[0049] Table 5 Corresponding relationship table of wave direction angle correction (2) Significant wave height The correction should be rounded up according to the data in the fatigue damage array; (3) Zero-crossing period The correction should be rounded up according to the data in the fatigue damage array.

[0050] Furthermore, when the duration of “isolated severe sea conditions” is greater than 3 hours, the three-dimensional array A can be obtained according to the actual duration of the “isolated severe sea conditions”. 孤立 ( , , ), and then return it to the fatigue damage five-dimensional array to obtain the fatigue damage result of “isolated severe sea conditions”.

[0051] In an embodiment of the present invention, after obtaining the fatigue damage value of each fatigue-sensitive position local structure of the target floating platform in the corresponding short-term measured sea condition recording period, the method further includes: according to the structural form of each fatigue-sensitive position local structure, when the manufacturing tolerance of the fatigue-sensitive position local structure exceeds the tolerance implied by the SN curve, the fatigue damage value corresponding to the current fatigue-sensitive position local structure is multiplied by the stress concentration factor corresponding to the structural form of the current fatigue-sensitive position local structure for correction. Specifically, for the structural form of the local structural area of ​​different fatigue-sensitive positions, when the manufacturing tolerance exceeds the tolerance implied by the SN curve, the fatigue damage result of the local structure should be multiplied by the stress concentration factor for correction. The correction factor stress concentration factor includes calculation or pre-determination based on the centerline difference of the plate thickness, the type of weld, the shape of the opening in the fatigue-sensitive area, the type of pipe node, etc.

[0052] In an embodiment of the present invention, the overall finite element model of the floating platform includes a wet surface model, an overall structural model, a mass model and a Morrison model, wherein: the wet surface model contains all external contour information of the floating platform below the waterline; the mass model is used to load the deadweight of the floating platform, the cabin loading and the weight information of the equipment carried; the overall structural model is used for the structural mesh division and boundary condition application of the floating platform; the Morrison model is used to calculate the stress conditions of small-scale structural components below the waterline in waves, that is, the characteristic size of the structural components below the waterline is much smaller than the wavelength of the incident wave, but still needs to transmit the wave load.

[0053] Figure 3 The flowchart of a method for predicting fatigue damage of a floating platform based on measured sea state data according to a specific embodiment of the present invention is schematically shown. The method for predicting fatigue damage of a floating platform based on measured sea state data proposed by the present invention first establishes an overall finite element model of the floating platform including a wet surface model, an overall structure model, a mass model and a Morrison model, imports different loading conditions n of the floating platform, and conducts hydrodynamic analysis to determine the stress transfer function of the local structure of each fatigue sensitive position in the floating platform under different loading conditions at different wave angles. , the stress transfer function Wave spectra of different short-term measured sea conditions Combination, the fatigue stress energy spectrum density function under different measured sea conditions is obtained , and construct different The angular wave direction corresponds to fatigue damage under different sea conditions, forming a 5-dimensional array D (i, n, , , ). Real-time monitoring of short-term sea conditions and wave direction in the sea area, and the wave direction can be obtained through Fourier transform , wave height and cycle Real-time sea state data table, according to the obtained real-time sea state data table, search the 5-dimensional array to obtain the real-time fatigue damage value of any local position i. Further, the total fatigue damage prediction result is obtained by linearly adding the real-time fatigue damage values.

[0054] For the method embodiments, for the sake of simplicity, they are all described as a series of action combinations, but those skilled in the art should know that the embodiments of the present invention are not limited by the order of the actions described, because according to the embodiments of the present invention, some steps can be performed in other orders or simultaneously. Secondly, those skilled in the art should also know that the embodiments described in the specification are all preferred embodiments, and the actions involved are not necessarily required by the embodiments of the present invention.

[0055] Figure 4The schematic diagram of the structure of the floating platform fatigue damage prediction system based on measured sea condition data according to an embodiment of the present invention is shown schematically. Figure 4 The floating platform fatigue damage prediction system based on measured sea state data of the embodiment of the present invention specifically includes a model building module 301, a first stress analysis module 302, a second stress analysis module 303, a fatigue damage analysis module 304, a sea state monitoring module 305 and a fatigue damage prediction module 306, wherein:

[0056] The model building module 301 is used to build an overall finite element model of the floating platform; specifically, it is used to build an overall finite element model of the floating platform by using a finite element analysis method.

[0057] The first stress analysis module 302 is used to determine the stress transfer function of the local structure of each fatigue sensitive position in the floating platform under different loading conditions at all specified wave angles within the preset wave frequency range; specifically, it is used to analyze the overall finite element model using a preset frequency domain hydrodynamic analysis software to determine the stress transfer function of the local structure of each fatigue sensitive position in the floating platform under different loading conditions at all specified wave angles within the preset wave frequency range. ; The second stress analysis module 303 is used to respectively obtain the stress transfer function Wave spectra of different short-term measured sea conditions Combination, the fatigue stress energy spectrum density function under different measured sea conditions is obtained : ,in, is the wave direction angle, is the wave frequency, For the meaningful wave height, It is a zero-crossing cycle; The fatigue damage analysis module 304 is used to determine the fatigue damage values ​​under different short-term measured sea conditions according to the fatigue stress energy spectrum density function under different measured sea conditions and the preset SN curve, and to construct a fatigue damage array D (i, n, , , ), where i represents different fatigue sensitive position local structures, n represents different loading conditions, and Different wave angles, , ) represent different short-term measured sea conditions; The sea condition monitoring module 305 is used to record the short-term measured sea condition data of each preset sea condition duration in the sea area in real time when fatigue damage prediction is performed on the target floating platform to be predicted. , ) and wave angle; The fatigue damage prediction module 306 is used to predict the fatigue damage of the target floating platform according to the current loading condition of the target floating platform and the short-term measured sea condition data of each preset sea condition duration ( , ) and wave direction angle to find the fatigue damage array to obtain the fatigue damage value of the local structure at each fatigue-sensitive position of the target floating platform during the corresponding short-term measured sea condition record period.

[0058] In one embodiment of the present invention, the system further comprises a fatigue damage statistics module. The fatigue damage statistics module is used to obtain fatigue damage values ​​of all short-term measured sea condition record periods of a local structure at any fatigue sensitive position of the target floating platform during its service life and perform linear addition to obtain fatigue damage prediction results of the local structure at the current fatigue sensitive position.

[0059] In another embodiment of the present invention, the system further includes a fatigue damage statistics module and a remaining fatigue life statistics module. The fatigue damage statistics module is used to obtain the fatigue damage values ​​of all short-term measured sea condition record periods of the local structure at any fatigue sensitive position of the target floating platform during its service life and perform linear addition to obtain the fatigue damage prediction result of the local structure at the current fatigue sensitive position. The remaining fatigue life statistics module is used to calculate the remaining fatigue life of the local structure at the current fatigue sensitive position based on the fatigue damage prediction result of the local structure at the current fatigue sensitive position and the preset life span.

[0060] As for the device embodiment, since it is basically similar to the method embodiment, the description is relatively simple, and the relevant parts can be referred to the partial description of the method embodiment.

[0061] The device embodiments described above are merely illustrative, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. Ordinary technicians in this field can understand and implement it without paying creative labor.

[0062] In addition, an embodiment of the present invention further provides a computer device, including a memory, a processor, and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the above-mentioned method for predicting fatigue damage of a floating platform based on measured sea condition data when executing the computer program. Figure 1 Steps S11 to S16 are shown.

[0063] The floating platform fatigue damage prediction method and system based on measured sea condition data provided by the embodiment of the present invention can evaluate the cumulative fatigue damage results of the floating platform in a certain period of time in real time by importing the measured data of the field environment. Compared with the conventional method of evaluating the cumulative fatigue damage by only using the previous wave dispersion data, more accurate fatigue damage prediction results can be obtained, which has important guiding significance for the inspection and maintenance of the floating platform. At the same time, the present invention can be applied to the fatigue damage results of the floating platform under the "isolated severe sea conditions" at a special moment that cannot be evaluated by conventional calculations, effectively improving the safety and reliability of the floating platform during its in-place period.

[0064] In addition, the floating platform fatigue damage prediction method and system based on measured sea condition data provided by the embodiment of the present invention is relatively simple and reasonable in engineering application, and a miniaturized digital twin structure array is constructed to facilitate real-time calculation on the floating platform, which does not bring about a huge amount of calculation, improves calculation efficiency, simplifies the analysis process, and meets the timeliness of engineering projects. Moreover, the method of the present invention does not require the installation of real-time data collection sensors, saving engineering implementation costs and later equipment maintenance costs.

[0065] Through the description of the above implementation methods, those skilled in the art can clearly understand that each implementation method can be implemented by means of software plus a necessary general hardware platform, and of course, can also be implemented by hardware. Based on this understanding, the above technical solution is essentially or the part that contributes to the prior art can be embodied in the form of a software product, and the computer software product can be stored in a computer-readable storage medium, such as ROM / RAM, a disk, an optical disk, etc., including a number of instructions for a computer device (which can be a personal computer, a server, or a network device, etc.) to execute the methods described in each embodiment or some parts of the embodiments.

[0066] In addition, those skilled in the art will appreciate that, although some embodiments herein include certain features included in other embodiments but not other features, the combination of features of different embodiments is meant to be within the scope of the present invention and form different embodiments. For example, any one of the claimed embodiments may be used in any combination.

[0067] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for predicting fatigue damage of a floating platform based on measured sea condition data, characterized in that: The method comprises: Establish the overall finite element model of the floating platform; Determine the stress transfer function of the local structure at each fatigue-sensitive location in the floating platform under different loading conditions at all specified wave angles within the preset wave frequency range ; The obtained stress transfer functions are Wave spectra of different short-term measured sea conditions Combination, the fatigue stress energy spectrum density function under different measured sea conditions is obtained : ,in, is the wave direction angle, is the wave frequency, For the meaningful wave height, It is a zero-crossing cycle; According to the fatigue stress energy spectrum density function under different measured sea conditions and the preset SN curve, the fatigue damage values ​​under different short-term measured sea conditions are determined, and the fatigue damage array D (i, n, , , ), where i represents different fatigue sensitive position local structures, n represents different loading conditions, and Different wave angles, , ) represent different short-term measured sea conditions; When fatigue damage prediction is performed on the target floating platform to be predicted, the short-term measured sea condition data of each preset sea condition duration in the sea area is recorded in real time ( , ) and wave angle; According to the current loading condition of the target floating platform and the recorded short-term measured sea state data for each preset sea state duration ( , ) and wave direction angle to find the fatigue damage array to obtain the fatigue damage value of the local structure at each fatigue-sensitive position of the target floating platform during the corresponding short-term measured sea condition record period.

2. The method according to claim 1, characterized in that The method further comprises: Obtain the fatigue damage values ​​of all short-term measured sea condition record periods of the local structure at any fatigue sensitive position of the target floating platform during its service life and perform linear addition to obtain the fatigue damage prediction result of the local structure at the current fatigue sensitive position, and / or The remaining fatigue life of the local structure at the current fatigue sensitive position is calculated based on the fatigue damage prediction result of the local structure at the current fatigue sensitive position and the preset life limit.

3. The method according to claim 1, characterized in that Determining fatigue damage values ​​under different short-term measured sea conditions according to fatigue stress energy spectrum density functions under different measured sea conditions and preset SN curves includes: Calculate the corresponding fatigue stress probability density function based on the fatigue stress energy spectrum density function under different measured sea conditions : Among them, S is the fatigue stress envelope corresponding to the short-term measured sea conditions; = , is the zero-order spectral moment of the fatigue stress energy spectral density function corresponding to the short-term measured sea conditions; Among them, the nth order spectral moment of the fatigue stress energy spectral density function is The calculation is as follows: ; According to the fatigue stress probability density function under different measured sea conditions Combined with SN curve , and the fatigue damage under different measured sea conditions is obtained: is the fatigue damage occurring in the i-th short-term measured sea condition, To describe the preset physical parameters of the SN curve, is the duration of the short-term sea condition, is the zero-crossing frequency of the stress response, , is the second-order spectral moment of the fatigue stress energy spectral density function corresponding to the short-term measured sea conditions, is the probability density function of fatigue stress.

4. The method according to claim 1, characterized in that The establishment of the overall finite element model of the floating platform comprises: The floating platform structure model is established through the finite element analysis method. The local structure models of fatigue-sensitive positions are grouped according to the characteristics of the floating platform. The weight of each profession is loaded according to the spectral fatigue design condition, and the boundary constraints are set to obtain the overall finite element model.

5. The method according to claim 1, characterized in that: According to the current loading condition of the target floating platform and the short-term measured sea state data ( , ) and wave direction angle before searching the fatigue damage array, the method further comprises: Searching a preset wave direction angle correction corresponding relationship table according to the wave direction angle in the currently recorded short-term measured sea state data to obtain a wave direction angle correction value corresponding to the wave direction angle in the currently recorded short-term measured sea state data, wherein the wave direction angle correction corresponding relationship table includes a corresponding relationship between a wave direction angle range interval of the measured sea state data and a wave direction angle in a fatigue damage array; According to the fatigue damage array The current recorded short-term measured sea state data is Round up to get Correction value; According to the fatigue damage array The current recorded short-term measured sea state data is Round up to get Correction value.

6. The method according to claim 1, characterized in that After obtaining the fatigue damage value of the local structure at each fatigue-sensitive position of the target floating platform during the corresponding short-term measured sea condition recording period, the method further includes: According to the structural form of the local structure at each fatigue-sensitive position, when the manufacturing tolerance of the local structure at the fatigue-sensitive position exceeds the tolerance implied by the SN curve, the fatigue damage value corresponding to the local structure at the current fatigue-sensitive position is multiplied by the stress concentration factor corresponding to the structural form of the local structure at the current fatigue-sensitive position for correction.

7. The method according to claim 1, characterized in that The overall finite element model of the floating platform includes a wet surface model, an overall structure model, a mass model and a Morrison model; The wet surface model contains all the external contour information of the floating platform below the water plane; The mass model is used to load the weight of the floating platform, cabin loading and the weight of the equipment carried; The overall structural model is used for the meshing of the floating platform structure and the application of boundary conditions; The Morrison model is used to calculate the stress conditions of small-scale structural components below the waterline in waves.

8. A floating platform fatigue damage prediction system based on measured sea condition data, characterized in that: The system comprises: Model building module, used to build the overall finite element model of the floating platform; The first stress analysis module is used to determine the stress transfer function of the local structure of each fatigue-sensitive position in the floating platform under different loading conditions at all specified wave angles within the preset wave frequency range. ; The second stress analysis module is used to obtain the stress transfer function Wave spectra of different short-term measured sea conditions Combination, the fatigue stress energy spectrum density function under different measured sea conditions is obtained : ,in, is the wave direction angle, is the wave frequency, For the meaningful wave height, It is a zero-crossing cycle; The fatigue damage analysis module is used to determine the fatigue damage values ​​under different short-term measured sea conditions according to the fatigue stress energy spectrum density function under different measured sea conditions and the preset SN curve, and to construct the fatigue damage array D (i, n, , , ), where i represents different fatigue sensitive position local structures, n represents different loading conditions, and Different wave angles, , ) represent different short-term measured sea conditions; The sea condition monitoring module is used to record the short-term measured sea condition data of each preset sea condition duration in the sea area in real time when fatigue damage prediction is performed on the target floating platform to be predicted. , ) and wave angle; The fatigue damage prediction module is used to predict the fatigue damage of the target floating platform based on the current loading condition of the target floating platform and the short-term measured sea state data ( , ) and wave direction angle to find the fatigue damage array to obtain the fatigue damage value of the local structure at each fatigue-sensitive position of the target floating platform during the corresponding short-term measured sea condition record period.

9. The system according to claim 8, characterized in that The system further comprises: The fatigue damage statistics module is used to obtain the fatigue damage values ​​of all short-term measured sea condition record periods of the local structure at any fatigue sensitive position of the target floating platform during its service life and perform linear addition to obtain the fatigue damage prediction results of the local structure at the current fatigue sensitive position, and / or The remaining fatigue life statistics module is used to calculate the remaining fatigue life of the local structure at the current fatigue sensitive position based on the fatigue damage prediction result of the local structure at the current fatigue sensitive position and the preset life span.

10. A computer device, characterized in that: The method comprises a memory, a processor and a computer program stored in the memory and executable on the processor, wherein the processor implements the steps of the method according to any one of claims 1 to 7 when executing the computer program.

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