Offshore structure fatigue damage assessment method and related equipment

Abstract

The invention discloses an offshore structure fatigue damage assessment method and related equipment, and the method comprises the steps: obtaining the stress time history and duration of an offshore structure, and obtaining a power spectral density function through Fourier transform; spectral moment parameters are extracted, characteristic spectral width parameter pairs are constructed, and stress distribution moment parameters are established in combination with the reverse slope of the S-N curve of the material; and finally, the damage amount is calculated according to the S-N curve type, the fatigue damage amount is calculated by directly utilizing a stress distribution moment parameter, a spectrum moment parameter and a material constant when the slope is single, and a result is obtained through piecewise integration of multiple slopes through a bi-component probability density function. The method is based on frequency domain parameter analysis, does not need complete long-term stress recording, greatly reduces the calculation and storage cost, and meets the requirements of real-time evaluation and the like. Gaussian broadband signal features are accurately captured through spectral moment parameter and feature spectral width parameter pairs, and the prediction precision under complex working conditions is remarkably improved. A unified framework is constructed by means of stress distribution moment parameters, and different types of S-N curves and fatigue limit effects can be compatible.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of material fatigue analysis, more particularly to a method for evaluating fatigue damage of offshore structures and related equipment. BACKGROUND

[0002] Fatigue damage prediction of structures under random loads is a core technical problem in the field of offshore engineering, wind power equipment, etc., and is directly related to the safety and reliability of equipment in service. Offshore structures such as floating platforms and wind towers bear random loads such as wind, waves and currents for a long time, and their stress responses exhibit typical Gaussian broadband random process characteristics, with not only multi-band energy distribution but also often multi-peak spectral shape, which makes the accuracy and efficiency of fatigue damage evaluation a key demand that needs to be solved in the industry.

[0003] Current mainstream fatigue analysis methods are divided into two categories: time domain and frequency domain, both of which have defects that are difficult to avoid. Time domain methods rely on complete stress history records to identify load cycles through rainflow counting to calculate fatigue accumulation, although they have high precision, but they are highly dependent on long-term signal and multi-point data, leading to a sharp increase in calculation and storage, which completely cannot meet the engineering needs of real-time evaluation, online monitoring and large-scale working condition combination analysis. The frequency domain method estimates fatigue damage through spectral moment characteristic quantities, has the advantages of high calculation efficiency and easy connection with spectral analysis, however, most methods are based on narrowband assumption or empirical bandwidth correction, and the description of stress distribution characteristics of Gaussian broadband signals is seriously insufficient, and in the working conditions of wideband, multi-peak or significant spectral shape change, the prediction deviation is large. At the same time, the fatigue properties of a large number of metal materials in engineering are not fixed, there is a fatigue limit, and the fatigue characteristic curve often exhibits multi-slope characteristics, while traditional frequency domain models are mostly constructed for single-slope fatigue characteristic curves, even if the spectral width correction is introduced, there is also a lack of systematic mapping mechanism from power spectrum parameters to rainflow stress range probability distribution, which cannot naturally and uniformly handle such multi-slope characteristics and fatigue limit effects in the frequency domain.

[0004] Based on this, the present application proposes a fatigue damage prediction method, which can overcome the defects of the prior art and meet the urgent needs of the field. SUMMARY

[0005] The present application provides a method for evaluating fatigue damage of offshore structures and related equipment, which realizes low calculation and storage cost, high precision evaluation of fatigue damage of offshore structures and compatibility of fatigue characteristics of different materials.

[0006] A method for evaluating fatigue damage of offshore structures, comprising:

[0007] Obtaining the stress time history and duration of the offshore structure under random loads, and obtaining the power spectral density function through Fourier transform;

[0008] According to the power spectral density function, a spectral moment parameter characterizing frequency domain energy distribution is extracted, and a characteristic spectral width parameter pair is constructed;

[0009] Based on the characteristic spectral width parameter pair and the inverse slope of the offshore structure material S-N curve, a stress distribution moment parameter is established;

[0010] If the offshore structure material S-N curve is single-slope, then based on the stress distribution moment parameter, the spectral moment parameter and material constants, the fatigue damage amount is directly calculated in the frequency domain;

[0011] If the offshore structure material S-N curve is multi-slope, then based on the stress distribution moment parameter, the spectral moment parameter and the characteristic spectral width parameter pair, a dimensionless stress range distribution model is obtained by constructing a two-component probability density function, and the fatigue damage amount is calculated by piecewise damage integration.

[0012] Optionally, according to the power spectral density function, a spectral moment parameter characterizing frequency domain energy distribution is extracted, and a characteristic spectral width parameter pair is constructed, including:

[0013] According to the power spectral density function, by integrating the power spectral density with each order of frequency, 0-order, 1-order, 2-order and 4-order spectral moment parameters are extracted;

[0014] Based on the extracted spectral moment parameters, two characteristic spectral width parameters characterizing signal bandwidth and spectral shape distribution are constructed by combination operation to form a characteristic spectral width parameter pair.

[0015] Optionally, the calculation formula of the spectral moment parameter is:

[0016]

[0017] The two characteristic spectral width parameters characterizing signal bandwidth and spectral shape distribution are respectively:

[0018]

[0019] Among them, is the 2-order spectral moment parameter, is the power spectral density function, and is the characteristic spectral width parameter.

[0020] Optionally, based on the characteristic spectral width parameter pair and the inverse slope of the offshore structure material S-N curve, a stress distribution moment parameter is established, including:

[0021] obtain a calibration mapping function, the calibration mapping function is calibrated based on a Gaussian wideband stress signal sample and a corresponding accurate damage value, and takes a characteristic spectrum width parameter and a negative slope as input, and takes a statistical moment reflecting an actual damage distribution as a fitting target to obtain;

[0022] input the characteristic spectrum width parameter and the negative slope of the offshore structure material S-N curve into the calibration mapping function, and calculate a stress distribution moment parameter by mapping.

[0023] Optionally, the calculation formula of the fatigue damage amount in the single slope form is:

[0024]

[0025] wherein D is a fatigue damage amount, is a spectrum moment parameter, C is a material constant, is a stress distribution moment parameter, T is a time constant, is a negative slope.

[0026] Optionally, based on the stress distribution moment parameter, the spectrum moment parameter and the characteristic spectrum width parameter pair, a dimensionless stress range distribution model is obtained by constructing a two-component probability density function, and a fatigue damage amount is calculated by segment damage integration, comprising:

[0027] Based on the characteristic spectrum width parameter pair, a dimensionless stress range two-component probability density function composed of two exponential function components is constructed, and the dimensionless stress range two-component probability density function contains a plurality of undetermined coefficients;

[0028] The stress distribution moment parameter is equivalent to the statistical moment of the dimensionless stress range represented by the two-component probability density function with the material negative slope as the order, and a constraint equation group about the undetermined coefficients is established;

[0029] The calibration mapping function and the constraint equation group are solved together to determine all the undetermined coefficients in the two-component probability density function, and a dimensionless stress range distribution model is generated;

[0030] Determine the normalized stress range interval corresponding to each slope segment in the offshore structure material S-N curve, and substitute the dimensionless stress range distribution model into the damage integral expression of each slope segment to calculate the fatigue damage amount of each segment respectively;

[0031] According to the linear fatigue accumulation criterion, the fatigue damage amounts calculated by all the slope segments of the offshore structure material S-N curve are summed to obtain a total fatigue damage amount.

[0032] Optionally, the two-component probability density function is:

[0033]

[0034] The calculation formula of the fatigue damage amount in the multi-slope form is:

[0035]

[0036] wherein, is a probability density function of a dimensionless stress range z, D is a fatigue damage amount, and is used to represent the contribution of the low stress component to damage, and is used to represent the contribution of the high stress component to damage, n is the number of slope segments of the S-N curve of the offshore structure material, and are the inverse slope and the material constant of the i-th slope segment of the S-N curve of the offshore structure material, respectively, and are the lower limit and the upper limit of the stress range of the i-th slope segment, is a spectral moment parameter, and T is a time constant.

[0037] A device for evaluating fatigue damage of an offshore structure, comprising:

[0038] a power spectral density function module, configured to obtain a stress time history and a duration of the offshore structure under random load, and to obtain a power spectral density function through Fourier transform;

[0039] a characteristic spectral width parameter pair module, configured to extract spectral moment parameters representing energy distribution in a frequency domain according to the power spectral density function, and to construct a characteristic spectral width parameter pair;

[0040] a stress distribution moment parameter module, configured to establish a stress distribution moment parameter based on the characteristic spectral width parameter pair and an inverse slope of an S-N curve of the offshore structure material;

[0041] a single-slope fatigue damage module, configured to, in a case where the S-N curve of the offshore structure material is in a single-slope form, directly calculate a fatigue damage amount in a frequency domain based on the stress distribution moment parameter, the spectral moment parameters and a material constant;

[0042] a multi-slope fatigue damage module, configured to, in a case where the S-N curve of the offshore structure material is in a multi-slope form, obtain a dimensionless stress range distribution model through construction of a two-component probability density function based on the stress distribution moment parameter, the spectral moment parameters and the characteristic spectral width parameter pair, and to calculate a fatigue damage amount through segmented damage integration.

[0043] An offshore structure fatigue damage assessment device comprises a memory and a processor;

[0044] The memory is configured to store a program.

[0045] The processor is configured to execute the program to implement the steps of the offshore structure fatigue damage assessment method according to any one of the preceding embodiments.

[0046] A readable storage medium has a computer program stored thereon, and the computer program, when executed by a processor, implements the steps of the offshore structure fatigue damage assessment method according to any one of the preceding embodiments.

[0047] A computer program product comprises a computer program, and the computer program, when executed by a processor, implements the steps of the offshore structure fatigue damage assessment method according to any one of the preceding embodiments.

[0048] As can be seen from the technical solutions described above, the offshore structure fatigue damage assessment method and related device provided by the embodiments of the present application first acquire the stress time history and duration of an offshore structure under random load, and obtain a power spectral density function through Fourier transform; then extract spectral moment parameters representing frequency domain energy distribution according to the function, and construct a feature spectral width parameter pair; subsequently, combine the inverse slope of the S-N curve of the offshore structure material to establish a stress distribution moment parameter; finally, select a corresponding calculation method according to the type of the S-N curve of the material, directly use the stress distribution moment parameter, the spectral moment parameter and the material constant to calculate the fatigue damage amount in the case of single slope, and construct a two-component probability density function by combining the feature spectral width parameter pair in the case of multiple slopes, and obtain the result through piecewise damage integration.

[0049] The present application can fully meet the engineering requirements of real-time assessment, online monitoring and large-scale working condition combination analysis by analyzing based on frequency domain feature parameters without relying on complete long-term stress records, and greatly reducing the calculation and storage costs. By extracting spectral moment parameters and constructing a feature spectral width parameter pair, the multi-band energy distribution and multi-peak spectral shape characteristics of Gaussian wideband signals can be accurately captured, and the prediction accuracy under wideband, multi-peak or significantly changed spectral shape working conditions can be significantly improved. In view of the differences in material fatigue characteristics, a unified analysis framework is established by using the stress distribution moment parameter, the fatigue damage amount can be directly calculated in the case of single slope S-N curve, and in the case of multiple slopes, a dimensionless stress range distribution model is constructed through a two-component probability density function, piecewise accurate integration is realized, different types of material fatigue characteristic curves and fatigue limit effects are effectively compatible, and efficient, accurate and widely applicable offshore structure fatigue assessment is realized. BRIEF DESCRIPTION OF DRAWINGS

[0050] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the following will briefly introduce the drawings needed to be used in the embodiments or prior art description. Obviously, the drawings in the following description are only part of the embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of the provided drawings.

[0051] Figure 1 A flow chart of a method for evaluating fatigue damage of offshore structure according to an embodiment of the present application is shown in the figure.

[0052] Figure 2 A schematic diagram of a multi-slope S-N curve of offshore structure material according to an embodiment of the present application is shown in the figure.

[0053] Figure 3 A schematic diagram of a device for evaluating fatigue damage of offshore structure according to an embodiment of the present application is shown in the figure.

[0054] Figure 4 A hardware structure block diagram of a device for evaluating fatigue damage of offshore structure according to an embodiment of the present application is shown in the figure. DETAILED DESCRIPTION

[0055] The technical solutions in the embodiments of the present application will be described clearly and completely below with reference to the drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present application.

[0056] The present application can be used in many general or special-purpose computing device environments or configurations. For example: personal computers, server computers, handheld or laptop devices, tablet devices, multiprocessor devices, distributed computing environments that include any of the above devices or devices, and the like.

[0057] Next, the technical solutions of the present application will be introduced. The present application proposes the following technical solutions, which are described in detail below.

[0058] Figure 1 A flow chart of a method for evaluating fatigue damage of offshore structure according to an embodiment of the present application is shown in the figure.

[0059] As shown in the figure, the method can include: Figure 1

[0060] Step S1, obtaining the stress time history and duration of offshore structure under random load, and obtaining the power spectral density function by Fourier transform.

[0061] ​Specifically, to accurately obtain stress data, monitoring equipment needs to be arranged at the fatigue critical parts of offshore structures, which are usually areas with concentrated stress and prone to fatigue damage, such as the connection between the column and the deck of a floating platform, the flange interface of a wind tower, etc. When installing, the monitoring equipment needs to be firmly combined with the structure surface to prevent signal distortion due to loosening. The sampling frequency of the monitoring equipment needs to be set in combination with the random load characteristics of the structure to ensure that the frequency characteristics of the load can be completely captured, and the data collection time needs to be sufficient, at least containing multiple load cycle periods, to ensure the representativeness of the data. The starting and ending time is recorded synchronously during the collection process to determine the duration of the stress time history. The collected raw stress data is preprocessed to eliminate the drift interference caused by temperature changes and irrelevant high-frequency noise, and then the stress signal in the time domain is converted to the frequency domain signal through Fourier transform, and then the power spectral density function is obtained, which can clearly reflect the energy distribution of the stress signal at different frequency components, providing a basis for subsequent analysis.

[0062] Step S2, extracting spectral moment parameters representing the energy distribution of the frequency domain according to the power spectral density function, and constructing a pair of characteristic spectral width parameters.

[0063] Specifically, the power spectral density function fully presents the frequency domain characteristics of the stress signal, and based on this function, multiple spectral moment parameters of different orders can be extracted, which represent the energy distribution characteristics of the frequency domain from different dimensions. For example, some spectral moment parameters can reflect the total energy size of the signal, some can reflect the center of gravity frequency position of the energy concentration, and some can describe the dispersion degree of the frequency distribution and the steepness of the spectrum shape, etc. After extracting these spectral moment parameters, a pair of characteristic spectral width parameters composed of two characteristic parameters is constructed based on their respective physical meanings. One of the characteristic parameters is mainly used to describe the concentration degree of the frequency spectrum width, reflecting the aggregation or dispersion state of the energy on the frequency axis; the other characteristic parameter focuses on the steepness of the frequency spectrum shape, reflecting the degree of energy change of different frequency components. Through the combination of these two parameters, the frequency energy distribution characteristics of the stress signal can be fully and accurately described, providing key basis for subsequent model establishment and analysis.

[0064] Step S3, establishing a stress distribution moment parameter based on the pair of characteristic spectral width parameters and the inverse slope of the S-N curve of the offshore structure material.

[0065] Specifically, first, the S-N curve of the metal material used in the offshore structure is obtained through a standard material fatigue test, which reflects the fatigue life characteristics of the material under different stress cycles. The inverse slope of the curve is determined through fitting analysis of the test data, which is a key indicator of material fatigue sensitivity and is directly related to the damage accumulation law of the material under stress. Then, the characteristic spectral width parameter obtained in step S2 is used as an important correction factor, combined with the inverse slope of the material S-N curve determined, to construct the stress distribution moment parameter. In the construction process, a plurality of standard specimen data with known fatigue damage results are used for calibration to ensure that the parameter can accurately associate the frequency energy distribution characteristics with the fatigue characteristics of the material, making the stress distribution moment parameter a core bridge connecting signal analysis and material fatigue performance, and providing a reliable intermediate parameter for subsequent fatigue damage calculation.

[0066] Step S4, if the S-N curve of the offshore structure material is single slope, the fatigue damage amount is directly calculated in the frequency domain based on the stress distribution moment parameter, the spectral moment parameter and the material constant.

[0067] Specifically, when the S-N curve of the material presents a single change slope in the entire stress range, it indicates that the fatigue characteristics of the material are relatively stable, and the linear cumulative damage theory can be used as the calculation basis to directly construct the damage calculation model in the frequency domain. In the calculation, the characteristic frequency of the stress cycle is first determined in combination with the spectral moment parameter, and then the total number of stress cycles in the entire monitoring period is calculated according to the stress time history duration obtained in step S1. Subsequently, the stress distribution moment parameter, the material constant and the total number of cycles are combined to directly obtain the fatigue damage amount through frequency domain calculation. This calculation method does not need to convert the frequency domain signal back to the time domain for load cycle counting, greatly simplifying the calculation process, improving the analysis efficiency, and at the same time ensuring the accuracy of the calculation result. The value of the damage amount can be directly used to judge whether the structure has occurred fatigue failure or the current fatigue damage degree.

[0068] After determining that the S-N curve of the material used in the offshore structure presents a single slope, a plurality of key parameters need to be integrated when calculating the fatigue damage amount: the spectral moment parameter representing the frequency domain characteristics of the stress signal, the material constant reflecting the fatigue performance of the material itself, the stress distribution moment parameter connecting the frequency domain characteristics and the fatigue characteristics of the material, and the time constant corresponding to the stress time history, the inverse slope of the material S-N curve, etc. By combining these parameters for operation, the fatigue damage amount of the structure under the current random load can be obtained, and the value of the damage amount can directly reflect the accumulated fatigue damage degree of the structure, which can be used as a direct basis for judging whether the structure has reached the fatigue failure state, and provides key support for the safety and reliability evaluation of the offshore structure during service.

[0069] The calculation formula of the fatigue damage amount in the single-slope form is:

[0070]

[0071] wherein D is the fatigue damage amount, is the stress distribution moment parameter, C is a material constant, T is a time constant, is the inverse slope.

[0072] In step S5, if the S-N curve of the offshore structure material is in a multi-slope form, a dimensionless stress range distribution model is obtained by constructing a two-component probability density function based on the stress distribution moment parameter, the spectral moment parameter and the characteristic spectral width parameter pair, and a segmented damage integral calculation is performed to obtain the fatigue damage amount.

[0073] Specifically, the S-N curve of many engineering metal materials will present different change slopes before and after the fatigue limit, that is, the fatigue characteristics of the low stress section and the high stress section are different, at this time, a calculation method that is more suitable for the actual characteristics of the material needs to be used. First, the related parameters in the characteristic spectral width parameter pair are used as weight distribution basis to construct a probability density function composed of two components, one component is used to describe the stress distribution characteristics in the high stress range, and the other component corresponds to the distribution of the low stress range, and through this two-component model, the actual distribution law of the stress range can be accurately fitted. At the same time, the actual stress range is converted into a dimensionless form to form a standardized stress range distribution model. Then, the fatigue limit of the material is taken as the dividing point, and the fatigue damage integral calculation is performed on the low stress section and the high stress section respectively, and the damage results of the two sections are superimposed to obtain the total fatigue damage amount. This method can fully adapt to the multi-slope fatigue characteristics of the material and effectively improve the accuracy of damage assessment under complex fatigue working conditions.

[0074] As can be seen from the above technical solutions, the offshore structure fatigue damage assessment method and related equipment provided by the embodiments of the present application first acquire the stress time history and duration of the offshore structure under random load, and obtain the power spectral density function through Fourier transform; then the spectral moment parameter representing the frequency domain energy distribution is extracted according to the function, and the characteristic spectral width parameter pair is constructed; then the stress distribution moment parameter is established in combination with the inverse slope of the S-N curve of the offshore structure material; finally, according to the type of the material S-N curve, the corresponding calculation method is selected, when the S-N curve is in a single-slope form, the fatigue damage amount is directly calculated by using the stress distribution moment parameter, the spectral moment parameter and the material constant, and when the S-N curve is in a multi-slope form, a two-component probability density function is constructed in combination with the characteristic spectral width parameter pair, and the result is obtained through segmented damage integral.

[0075] The application can meet the engineering requirements of real-time evaluation, online monitoring and large-scale working condition combination analysis by analyzing the frequency domain characteristic parameters without relying on complete long-term stress records, greatly reducing the calculation and storage costs. By extracting the spectral moment parameters and constructing the characteristic spectral width parameter pair, the multi-band energy distribution and multi-peak spectral shape characteristics of the Gaussian wideband signal can be accurately captured, and the prediction accuracy in the wideband, multi-peak or significantly changed spectral shape working condition can be significantly improved. In view of the difference of material fatigue characteristics, a unified analysis framework is established by the stress distribution moment parameters, the fatigue damage amount can be directly calculated in the single slope S-N curve scene, and the dimensionless stress range distribution model is constructed by the double component probability density function in the multi-slope scene, the segmented accurate integration is realized, the fatigue characteristic curves and fatigue limit effect of different types of materials are effectively compatible, and efficient, accurate and widely applicable offshore structure fatigue evaluation is realized.

[0076] In some embodiments of the application, the process of step S2, extracting the spectral moment parameters representing the frequency energy distribution according to the power spectral density function, and constructing the characteristic spectral width parameter pair, can specifically include:

[0077] Step S21, according to the power spectral density function, the 0th, 1st, 2nd and 4th spectral moment parameters are extracted by integrating the power spectral density with different orders of frequency.

[0078] Step S22, based on the extracted spectral moment parameters, two characteristic spectral width parameters representing the bandwidth and spectral shape distribution of the signal are constructed by combination operation to form the characteristic spectral width parameter pair.

[0079] Specifically, the power spectral density function is the core basis for reflecting the frequency energy distribution of the stress signal. When extracting the spectral moment parameters, the different order powers of frequency are associated with the power spectral density function, and the spectral moment parameters of different orders are obtained by integral operation. The 0th spectral moment parameter can reflect the total energy level of the stress signal in the frequency domain, the 1st spectral moment parameter can be associated with the energy concentration corresponding to the center frequency position, and the 2nd and 4th spectral moment parameters can reflect the dispersion degree of frequency distribution and the steepness characteristics of spectral shape from different dimensions, respectively. These spectral moment parameters of different orders together constitute the basic feature set for describing the frequency energy distribution.

[0080] Based on the spectral moment parameters, two characteristic spectral width parameters are obtained by combination operation. One of the characteristic spectral width parameters is mainly used to represent the bandwidth of the stress signal spectrum, which can reflect the aggregation or dispersion degree of energy on the frequency axis; the other characteristic spectral width parameter focuses on the distribution characteristics of the spectral shape, which can reflect the energy variation law corresponding to different frequency components. The characteristic spectral width parameter pair can more accurately and comprehensively characterize the frequency domain distribution characteristics of the stress signal, and provide key frequency domain feature support for subsequent establishment of stress distribution moment parameters and calculation of fatigue damage amount.

[0081] Obtaining stress response time history of a structure under random load and its duration T, and determining the S-N curve material constant and the inverse slope corresponding to the position of the structure, when the S-N curve has multiple slope characteristics, obtaining the parameter pairs of each slope segment and the corresponding stress range segmentation interval .

[0082] Corresponding to the stress time history Fourier transform is performed to obtain the stress power spectral density function , and the spectral moment parameter representing the frequency domain energy distribution is calculated . The calculation formula of the spectral moment parameter is:

[0083]

[0084] The two characteristic spectral width parameters representing the signal bandwidth and spectral shape distribution are:

[0085]

[0086] wherein, is the order spectral moment parameter, is the power spectral density function, and is the characteristic spectral width parameter.

[0087] Under the condition of considering the inverse slope k of the material S-N curve, the stress distribution moment parameter is introduced, and the function mapping relationship between , and k is established:

[0088]

[0089] wherein, the function is calibrated through experimental data and / or numerical simulation results, and can be obtained by polynomial fitting, machine learning model, etc.

[0090] In some embodiments of the present application, the process of establishing the stress distribution moment parameter based on the characteristic spectral width parameter pair and the inverse slope of the offshore structure material S-N curve is introduced, which can specifically include:

[0091] Step S31, obtaining a calibration mapping function, the calibration mapping function is calibrated based on the Gaussian wideband stress signal sample and the corresponding accurate damage value, taking the characteristic spectral width parameter and the inverse slope as input, and taking the statistical moment reflecting the actual damage distribution as the fitting target to obtain;

[0092] Step S32: Input the characteristic spectral width parameter and the inverse slope of the SN curve of the marine structural material into the calibration mapping function, and obtain the stress distribution moment parameter through mapping calculation.

[0093] Specifically, the first step is to construct a Gaussian broadband stress signal sample library covering different frequency domain characteristics. The samples should include stress signal data of different bandwidths and spectral shapes commonly found in marine structures to ensure the applicability of the function. Simultaneously, for each sample, accurate fatigue damage values ​​are obtained through high-precision time-domain fatigue tests or field measurements, serving as a reference benchmark for fitting. Subsequently, using the obtained characteristic spectral width parameters and the inverse slope of the SN curve of the marine structure material as input variables, and the statistical moments reflecting the actual fatigue damage distribution as the fitting target, regression analysis and parameter calibration of multiple sets of sample data are used to determine the mapping relationship between the input and the target, ultimately obtaining the calibrated mapping function. The core function of this function is to establish a quantitative correlation between frequency domain characteristic parameters and material fatigue damage characteristics, ensuring the accuracy of subsequent parameter calculations.

[0094] The constructed characteristic spectral width parameter pair, along with the inverse slope of the SN curve determined through material fatigue testing, are simultaneously input into a calibrated mapping function. The mapping operation is then completed using the function's pre-defined correlation logic. This process fuses the signal characteristics (characteristic spectral width parameter) at the frequency domain with the material's inherent fatigue sensitivity characteristics (inverse slope). The resulting stress distribution moment parameter is a crucial intermediate parameter connecting frequency domain signal analysis and material fatigue damage calculation. Its value quantifies the influence of stress signal characteristics on material fatigue damage, providing a core quantitative basis for subsequent fatigue damage calculations.

[0095] Based on this, such as Figure 2 As shown, when the SN curve of the marine structural material is in a multi-slope form, step S5, based on the stress distribution moment parameter, the spectral moment parameter, and the characteristic spectral width parameter pair, constructs a dimensionless stress range distribution model by a two-component probability density function, and performs piecewise damage integral calculation to obtain the fatigue damage amount. Specifically, this process may include:

[0096] Step S51: Based on the characteristic spectral width parameter pair, construct a dimensionless stress range binary probability density function composed of the superposition of two exponential function components. The dimensionless stress range binary probability density function contains multiple undetermined coefficients.

[0097] Specifically, considering the fatigue characteristics of the material corresponding to the multi-slope S-N curve in different stress ranges, the stress distribution characteristics of the high and low stress intervals need to be fitted by the probability density function of two components, so two exponential function components are selected for superposition, each component corresponds to the distribution law of a type of stress range. At the same time, the actual stress range is converted into a dimensionless form to realize the standardized description of the stress distribution under different working conditions, and the multiple undetermined coefficients in the function need to be determined combined with subsequent parameters, leaving adjustment space for accurate fitting of the actual stress distribution.

[0098] Step S52, the stress distribution moment parameter is equivalent to the dimensionless stress range statistical moment represented by the double-component probability density function with the material inverse slope as the order, and a constraint equation set about the undetermined coefficient is established.

[0099] Specifically, the stress distribution moment parameter is the core parameter related to the frequency domain characteristics and the material fatigue characteristics, and the dimensionless stress range statistical moment of the double-component probability density function under the order of the material inverse slope can reflect the fatigue damage related statistical characteristics corresponding to the distribution. The equivalent matching of the two can make the distribution characteristics of the function consistent with the actual damage law. Based on this equivalent relationship, multiple equations about the undetermined coefficients of the function can be derived, and then a constraint equation set is formed to provide a basis for determining the undetermined coefficients.

[0100] Step S53, the calibration mapping function is combined with the constraint equation set to solve and determine all the undetermined coefficients in the double-component probability density function, and a dimensionless stress range distribution model is generated.

[0101] Specifically, the mapping function calibrated in the step is called, the correlation logic between the frequency domain parameters and the damage characteristics established by it is used, the constraint equation set is combined, and the specific values of all the undetermined coefficients in the double-component probability density function are determined by simultaneous solution. At this time, the form and parameters of the function have been determined, which can be used as a model that can accurately describe the dimensionless stress range distribution law of the current stress signal, and provides a basis for subsequent segmented damage calculation.

[0102] Step S54, determine the normalized stress range interval corresponding to each slope segment of the offshore structure material S-N curve, and substitute the dimensionless stress range distribution model into the damage integral expression of each slope segment to calculate the fatigue damage of each segment.

[0103] Specifically, based on the slope change nodes of the SN curve of marine structural materials, different stress range intervals are divided, and each interval is converted into a normalized interval corresponding to the dimensionless stress range. Since different slope segments correspond to different fatigue damage laws of materials, a damage integral expression needs to be constructed separately for each interval. Then, the generated dimensionless stress range distribution model is substituted into the corresponding expression to complete the integral calculation and obtain the fatigue damage amount corresponding to each slope segment.

[0104] Step S55: According to the linear fatigue accumulation criterion, sum the fatigue damage calculated from all the slope segments of the SN curve of the marine structural material to obtain the total fatigue damage.

[0105] Specifically, the core principle of the linear fatigue accumulation criterion is that the fatigue damage generated by a structure under different stress levels is independent and linearly superimposed. The amount of fatigue damage corresponding to each stress segment is equal to the ratio of the actual number of cycles under that stress segment to the fatigue life of the material under that stress level. When the sum of the damage corresponding to each stress segment reaches 1, the structure is judged to have suffered fatigue failure. Based on this criterion, the fatigue damage calculated from each slope segment of the SN curve for marine structural materials is superimposed and summed. The final total fatigue damage can comprehensively reflect the overall cumulative fatigue damage degree of the structure under the current random load. Its magnitude can be directly used as a key indicator to determine whether the structure is close to or has reached the fatigue failure state, providing a direct quantitative basis for the service safety and reliability assessment of marine structures.

[0106] The probability density function of the two components is:

[0107]

[0108] A two-component probability density function is used to describe the distribution of dimensionless stress range. It takes the form of a superposition of two exponential function components, where the parameters of the two components ( and These correspond to the distribution characteristics of low-to-medium stress and high-stress ranges, respectively. The dual-component structure is designed to adapt to the differences in fatigue characteristics of materials in different stress ranges under multi-slope SN curves, enabling a more accurate fit to the distribution of the actual stress range and providing a basic distribution model for subsequent segmented damage calculations.

[0109] The formula for calculating the fatigue damage amount in the multi-slope form is as follows:

[0110]

[0111] in, Let be the probability density function for the dimensionless stress range z, and D be the fatigue damage amount. and for characterizing the contribution of the low-to-moderate stress component to the damage, and for characterizing the contribution of the high stress component to the damage, n is the number of slope segments of the S-N curve of the offshore structure material, and are the inverse slope and the material constant of the i-th slope segment of the S-N curve of the offshore structure material, respectively, and are the lower and upper stress range limits of the i-th slope segment, is the order spectral moment parameter, and T is the time constant.

[0112] The calculation formula of the fatigue damage amount in the multi-slope form is the calculation core of the fatigue damage in the multi-slope scenario: based on the time constant and the spectral moment parameter, in combination with the double-component probability density function, the total damage is obtained by segmenting and integrating the stress range interval corresponding to each slope segment of the S-N curve, and then superimposing the damage amounts of each segment. In the formula, by distinguishing the inverse slope, the material constant and the upper and lower stress range limits of different slope segments, the fatigue characteristics of the multi-slope material are adapted, and the final calculation result directly reflects the total fatigue damage degree of the structure.

[0113] A kind of offshore structure fatigue damage assessment device provided by the embodiments of the present application is described below, and the offshore structure fatigue damage assessment device described below can be correspondingly referred to with the offshore structure fatigue damage assessment method described above.

[0114] Referring to Figure 3 , Figure 3 is a schematic diagram of a kind of offshore structure fatigue damage assessment device disclosed by the embodiments of the present application.

[0115] As Figure 3 indicated, the offshore structure fatigue damage assessment device can include:

[0116] The power spectral density function module 110 is configured to obtain the stress time history and the duration of the offshore structure under the action of random load, and obtain the power spectral density function by Fourier transform.

[0117] The characteristic spectral width parameter pair module 120 is configured to extract the spectral moment parameter representing the energy distribution of the frequency domain according to the power spectral density function, and construct a characteristic spectral width parameter pair.

[0118] The stress distribution moment parameter module 130 is configured to establish a stress distribution moment parameter based on the characteristic spectral width parameter pair and the inverse slope of the S-N curve of the offshore structure material.

[0119] A single-slope fatigue damage module 140 is configured to, in the case that the offshore structure material S-N curve is in a single-slope form, directly calculate a fatigue damage amount in a frequency domain based on the stress distribution moment parameter, the spectral moment parameter, and a material constant;

[0120] A multi-slope fatigue damage module 150 is configured to, in the case that the offshore structure material S-N curve is in a multi-slope form, obtain a dimensionless stress range distribution model by constructing a two-component probability density function based on the stress distribution moment parameter, the spectral moment parameter, and the characteristic spectral width parameter pair, and perform segmented damage integral calculation to obtain the fatigue damage amount.

[0121] As can be seen from the technical solutions described above, the offshore structure fatigue damage evaluation method and related device provided by the embodiments of the present application first obtain a stress time history and a duration of an offshore structure under random load, and obtain a power spectral density function through Fourier transform; then extract a spectral moment parameter representing frequency domain energy distribution and construct a characteristic spectral width parameter pair according to the function; subsequently, establish a stress distribution moment parameter in combination with an inverse slope of an offshore structure material S-N curve; finally, select a corresponding calculation method according to the type of the material S-N curve, directly calculate a fatigue damage amount by using the stress distribution moment parameter, the spectral moment parameter, and a material constant in the case of a single-slope form, and construct a two-component probability density function in combination with the characteristic spectral width parameter pair in the case of a multi-slope form, and obtain a result through segmented damage integral.

[0122] The present application can fully meet the engineering requirements of real-time evaluation, online monitoring, and large-scale working condition combination analysis by analyzing based on frequency domain characteristic parameters without relying on complete long-term stress records, and greatly reduces the calculation and storage costs. By extracting the spectral moment parameter and constructing the characteristic spectral width parameter pair, the multi-band energy distribution and multi-peak spectral shape characteristics of the Gaussian wideband signal can be accurately captured, and the prediction accuracy under wideband, multi-peak, or significantly changed spectral shape working conditions can be significantly improved. In view of the differences in material fatigue characteristics, a unified analysis framework is established through the stress distribution moment parameter, fatigue damage amount calculation can be directly completed in the case of a single-slope S-N curve, and in the case of a multi-slope, a dimensionless stress range distribution model is constructed through a two-component probability density function, segmented accurate integral is realized, different types of material fatigue characteristic curves and fatigue limit effects are effectively compatible, and efficient, accurate, and widely applicable offshore structure fatigue evaluation is realized.

[0123] Optionally, according to the power spectral density function, a spectral moment parameter representing frequency domain energy distribution is extracted, and a characteristic spectral width parameter pair is constructed, including:

[0124] According to the power spectral density function, 0-order, 1-order, 2-order, and 4-order spectral moment parameters are extracted by performing integral operation on each order power of frequency and power spectral density;

[0125] Based on the extracted spectrum moment parameters of each order, two characteristic spectrum width parameters representing signal bandwidth and spectrum shape distribution are constructed by combination operation to form a pair of characteristic spectrum width parameters.

[0126] Optionally, the calculation formula of the spectrum moment parameter is:

[0127]

[0128] The two characteristic spectrum width parameters representing signal bandwidth and spectrum shape distribution are respectively:

[0129]

[0130] wherein, is the spectrum moment parameter of the mth order, is the power spectral density function, and is the characteristic spectrum width parameter.

[0131] Optionally, based on the pair of characteristic spectrum width parameters and the inverse slope of the S-N curve of the offshore structure material, a stress distribution moment parameter is established, including:

[0132] An calibration mapping function is obtained, the calibration mapping function is based on Gaussian broadband stress signal samples and corresponding accurate damage values, and the calibration mapping function is calibrated to take the characteristic spectrum width parameter and the inverse slope as input and take the statistical moment reflecting the actual damage distribution as a fitting target;

[0133] The characteristic spectrum width parameter and the inverse slope of the S-N curve of the offshore structure material are input into the calibration mapping function, and the stress distribution moment parameter is calculated by mapping.

[0134] Optionally, the calculation formula of the fatigue damage amount in the single slope form is:

[0135]

[0136] wherein, D is the fatigue damage amount, is the spectrum moment parameter of the mth order, C is a material constant, is the stress distribution moment parameter, and T is a time constant, is the inverse slope.

[0137] Optionally, based on the stress distribution moment parameter, the spectrum moment parameter and the pair of characteristic spectrum width parameters, a dimensionless stress range distribution model is obtained by constructing a two-component probability density function, and a fatigue damage amount is calculated by segment damage integration, including:

[0138] ​Based on the characteristic spectrum width parameter pair, a dimensionless stress range two-component probability density function superimposed by two exponential function components is constructed, wherein the dimensionless stress range two-component probability density function contains a plurality of undetermined coefficients;

[0139] The stress distribution matrix parameter is equivalent to a dimensionless stress range statistical moment of order of the inverse slope of the material represented by the two-component probability density function, and a constraint equation group about the undetermined coefficients is established;

[0140] The calibration mapping function is combined with the constraint equation group to solve and determine all the undetermined coefficients in the two-component probability density function, and a dimensionless stress range distribution model is generated;

[0141] The normalized stress range interval corresponding to each slope segment of the offshore structure material S-N curve is determined, and the dimensionless stress range distribution model is substituted into the damage integral expression of each slope segment to calculate the fatigue damage amount of each segment, respectively;

[0142] According to the linear fatigue accumulation criterion, the fatigue damage amounts calculated by all the slope segments of the offshore structure material S-N curve are summed to obtain a total fatigue damage amount.

[0143] Optionally, the two-component probability density function is:

[0144]

[0145] The calculation formula of the fatigue damage amount in the multi-slope form is:

[0146]

[0147] wherein, is a probability density function of dimensionless stress range z, and D is a fatigue damage amount, and used to represent the contribution of the low stress component to damage, and used to represent the contribution of the high stress component to damage, and n is the number of slope segments of the offshore structure material S-N curve, and are the inverse slope and material constant of the i-th slope segment of the offshore structure material S-N curve, respectively, and are the lower limit and upper limit of the stress range of the i-th slope segment, is a spectrum moment parameter, and T is a time constant.

[0148] The offshore structure fatigue damage evaluation device provided by the embodiments of the present application can be applied to an offshore structure fatigue damage evaluation device.Figure 4 A hardware structure block diagram of the offshore structure fatigue damage assessment device is shown with reference to Figure 4 The hardware structure of the offshore structure fatigue damage assessment device can include at least one processor 1, at least one communication interface 2, at least one memory 3 and at least one communication bus 4.

[0149] In the embodiments of the present application, the number of the processor 1, the communication interface 2, the memory 3 and the communication bus 4 is at least one, and the processor 1, the communication interface 2 and the memory 3 complete the communication with each other through the communication bus 4.

[0150] The processor 1 can be a central processing unit CPU, or an application specific integrated circuit ASIC, or one or more integrated circuits configured to implement the embodiments of the present application, etc.

[0151] The memory 3 can include a high-speed RAM memory, and can also include a non-volatile memory, etc., such as at least one disk memory.

[0152] The memory stores a program, and the processor can call the program stored in the memory, and the program is used for:

[0153] Obtaining the stress time history and duration of the offshore structure under random load, and obtaining the power spectral density function through Fourier transform;

[0154] According to the power spectral density function, extracting spectral moment parameters representing the energy distribution of the frequency domain, and constructing a characteristic spectral width parameter pair;

[0155] Based on the characteristic spectral width parameter pair and the inverse slope of the S-N curve of the offshore structure material, a stress distribution moment parameter is established;

[0156] If the S-N curve of the offshore structure material is in a single slope form, then based on the stress distribution moment parameter, the spectral moment parameter and the material constant, the fatigue damage amount is directly calculated in the frequency domain;

[0157] If the S-N curve of the offshore structure material is in a multi-slope form, then based on the stress distribution moment parameter, the spectral moment parameter and the characteristic spectral width parameter pair, a dimensionless stress range distribution model is obtained through the construction of a two-component probability density function, and the fatigue damage amount is obtained by performing segmented damage integral calculation.

[0158] Optionally, the detailed functions and extended functions of the program can refer to the description above.

[0159] The embodiment of the present application also provides a readable storage medium, which can store a program suitable for processor execution, and the program is used for:

[0160] obtaining a stress time history and duration of the offshore structure under random load, and obtaining a power spectral density function through Fourier transform;

[0161] extracting a spectral moment parameter representing frequency domain energy distribution according to the power spectral density function, and constructing a characteristic spectral width parameter pair;

[0162] establishing a stress distribution moment parameter based on the characteristic spectral width parameter pair and a negative slope of an S-N curve of a material of the offshore structure;

[0163] if the S-N curve of the material of the offshore structure is in a single slope form, then directly calculating a fatigue damage amount in a frequency domain based on the stress distribution moment parameter, the spectral moment parameter and a material constant;

[0164] if the S-N curve of the material of the offshore structure is in a multi-slope form, then obtaining a dimensionless stress range distribution model through construction of a two-component probability density function based on the stress distribution moment parameter, the spectral moment parameter and the characteristic spectral width parameter pair, and performing segmented damage integral calculation to obtain the fatigue damage amount.

[0165] Optionally, the refinement function and the extension function of the program can refer to the description above.

[0166] The embodiment of the present application also provides a computer program product, which comprises a computer program, and the computer program is run by a processor to execute the method.

[0167] obtaining a stress time history and duration of the offshore structure under random load, and obtaining a power spectral density function through Fourier transform;

[0168] extracting a spectral moment parameter representing frequency domain energy distribution according to the power spectral density function, and constructing a characteristic spectral width parameter pair;

[0169] establishing a stress distribution moment parameter based on the characteristic spectral width parameter pair and a negative slope of an S-N curve of a material of the offshore structure;

[0170] if the S-N curve of the material of the offshore structure is in a single slope form, then directly calculating a fatigue damage amount in a frequency domain based on the stress distribution moment parameter, the spectral moment parameter and a material constant;

[0171] if the S-N curve of the material of the offshore structure is in a multi-slope form, then obtaining a dimensionless stress range distribution model through construction of a two-component probability density function based on the stress distribution moment parameter, the spectral moment parameter and the characteristic spectral width parameter pair, and performing segmented damage integral calculation to obtain the fatigue damage amount.

[0172] Optionally, the refinement and extension of the program can refer to the above description.

[0173] Finally, it is to be understood that the phraseology or terminology employed herein, such as "first" and "second", etc. for example, is for the purpose of differentiating one

[0174] The various embodiments in the specification are described with progressive manner, and each embodiment focuses on the difference from other embodiments, and the same or similar parts between the embodiments can be mutually referred to.

[0175] The above description of disclosed embodiments enables a person skilled in the art to implement or use the present application. Various modifications to these embodiments will be apparent to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present application. Therefore, the present application will not be limited to the embodiments shown herein, but will conform to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for assessing fatigue damage to marine structures, characterized in that, include: The stress time history and duration of the offshore structure under random loads are obtained, and the power spectral density function is obtained through Fourier transform. Based on the power spectral density function, extract the spectral moment parameters characterizing the frequency domain energy distribution, and construct characteristic spectral width parameter pairs; Based on the aforementioned characteristic spectral width parameter pair and the inverse slope of the SN curve of marine structural materials, stress distribution moment parameters are established. If the SN curve of the marine structural material is in the form of a single slope, then the fatigue damage can be directly calculated in the frequency domain based on the stress distribution moment parameter, the spectral moment parameter and the material constant. If the SN curve of the marine structural material is in the form of multiple slopes, then based on the stress distribution moment parameter, the spectral moment parameter and the characteristic spectral width parameter pair, a dimensionless stress range distribution model is obtained by constructing a two-component probability density function, and the fatigue damage is obtained by performing piecewise damage integral calculation.

2. The method according to claim 1, characterized in that, Based on the power spectral density function, spectral moment parameters characterizing the frequency domain energy distribution are extracted, and characteristic spectral width parameter pairs are constructed, including: Based on the power spectral density function, the 0th, 1st, 2nd and 4th order spectral moment parameters are extracted by integrating the power of each order of frequency with the power spectral density. Based on the extracted spectral moment parameters of each order, two characteristic spectral width parameters representing the signal bandwidth and spectral shape distribution are constructed through combination operations, forming a characteristic spectral width parameter pair.

3. The method according to claim 2, characterized in that, The formula for calculating the spectral moment parameter is: The two characteristic spectral width parameters representing the signal bandwidth and spectral shape distribution are as follows: in, for Spectral moment parameters, Let be the power spectral density function. and This is the characteristic spectral width parameter.

4. The method according to claim 1, characterized in that, Based on the aforementioned characteristic spectral width parameter pair and the inverse slope of the SN curve of marine structural materials, stress distribution moment parameters are established, including: A calibration mapping function is obtained, which is based on Gaussian broadband stress signal samples and corresponding accurate damage values, with characteristic spectral width parameters and antislope as inputs, and statistical moments reflecting the actual damage distribution as the fitting target. The characteristic spectral width parameter and the inverse slope of the SN curve of the marine structural material are input into the calibration mapping function, and the stress distribution moment parameter is obtained through mapping calculation.

5. The method according to claim 1, characterized in that, The formula for calculating fatigue damage in the form of a single slope is: Where D represents the fatigue damage amount. for Spectral moment parameter, where C is a material constant. Here, T is the stress distribution moment parameter, and T is the time constant. It is the inverse slope.

6. The method according to claim 4, characterized in that, Based on the stress distribution moment parameter, the spectral moment parameter, and the characteristic spectral width parameter pair, a dimensionless stress range distribution model is obtained by constructing a two-component probability density function, and the fatigue damage amount is obtained by performing piecewise damage integral calculation, including: Based on the aforementioned characteristic spectral width parameter pair, a dimensionless stress range binary probability density function is constructed, which is composed of the superposition of two exponential function components. The dimensionless stress range binary probability density function contains multiple undetermined coefficients. The stress distribution moment parameters are equivalent to the dimensionless stress range statistical moments characterized by the two-component probability density function with the antislope of the material as the order, and a set of constraint equations is established for the undetermined coefficients. By combining the calibration mapping function with the constraint equations, all undetermined coefficients in the binary probability density function are determined, and a dimensionless stress range distribution model is generated. Determine the normalized stress range corresponding to each slope segment in the SN curve of the marine structural material, and substitute the dimensionless stress range distribution model into the damage integral expression of each slope segment to calculate the fatigue damage of each segment. According to the linear fatigue accumulation criterion, the fatigue damage calculated from all slope segments of the SN curve of the marine structural material is summed to obtain the total fatigue damage.

7. The method according to claim 6, characterized in that, The probability density function of the two components is: The formula for calculating the fatigue damage amount in the multi-slope form is as follows: in, Let be the probability density function for the dimensionless stress range z, and D be the fatigue damage amount. and Used to characterize the contribution of low-to-medium stress components to damage. and Used to characterize the contribution of high-stress components to damage, where n is the number of slope segments in the SN curve of marine structural materials. and These represent the inverse slope and material constant of the i-th slope segment in the SN curve of marine structural materials, respectively. and Let i be the lower and upper limits of the stress range for the i-th slope segment. for The order spectral moment parameter, where T is the time constant.

8. A fatigue damage assessment device for marine structures, characterized in that, include: The power spectral density function module is used to obtain the stress time history and duration of offshore structures under random loads, and the power spectral density function is obtained through Fourier transform. The feature spectral width parameter pair module is used to extract spectral moment parameters characterizing the frequency domain energy distribution based on the power spectral density function, and to construct feature spectral width parameter pairs. The stress distribution moment parameter module is used to establish stress distribution moment parameters based on the characteristic spectral width parameter pair and the inverse slope of the SN curve of marine structural materials. The single-slope fatigue damage module is used to directly calculate the fatigue damage in the frequency domain based on the stress distribution moment parameter, the spectral moment parameter, and the material constant when the SN curve of the marine structural material is in the form of a single slope. The multi-slope fatigue damage module is used to obtain a dimensionless stress range distribution model by constructing a two-component probability density function based on the stress distribution moment parameter, the spectral moment parameter, and the characteristic spectral width parameter pair when the SN curve of the marine structural material is in the form of multiple slopes, and to calculate the fatigue damage amount by performing piecewise damage integral calculation.

9. A fatigue damage assessment device for marine structures, characterized in that, Including memory and processor; The memory is used to store programs; The processor is used to execute the program to implement the various steps of the marine structural fatigue damage assessment method as described in any one of claims 1-7.

10. A readable storage medium having a computer program stored thereon, characterized in that, When the computer program is executed by the processor, it implements each step of the marine structural fatigue damage assessment method as described in any one of claims 1-7.

11. A computer program product, comprising a computer program, characterized in that, The computer program is executed by the processor to perform the steps of the fatigue damage assessment method for marine structures as described in any one of claims 1-7.

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