A partial resonance region distributed dynamic vibration absorption design method for an offshore platform

Abstract

The application provides a design method for a distributed dynamic vibration absorber in a local resonance region of an offshore platform, which can control the vibration of the local resonance region of the offshore platform, take the excessive vibration line spectrum as a control target, equivalently take the local resonance region to be controlled as a complex boundary numerical model, quickly determine the parameters of the distributed dynamic vibration absorber, and quickly evaluate the vibration absorption effect of the distributed dynamic vibration absorber, so as to effectively control the multi-line spectrum vibration of the local resonance region of the offshore platform. The application constructs a numerical equivalent model of the local resonance region of the platform based on the energy method, effectively improves the solving efficiency of the equivalent mass of the local region to be controlled, combines with the optimal homodyne design principle, realizes the quick determination of the parameters of the dynamic vibration absorber, and finally verifies the dynamic vibration absorption effect by the finite element method, avoids the repeated iterative calculation based on the large finite element numerical model of the platform, and can greatly improve the control efficiency of the line spectrum vibration of the local resonance region of the offshore platform.

Description

Technical Field

[0001] This invention relates to the field of vibration reduction and noise reduction technology for marine platforms, specifically to a method for controlling excessive vibration and noise. Background Technology

[0002] With the ever-increasing demand for oil and gas resources, offshore oil and gas energy is playing an increasingly important role in energy development. Offshore platforms, as large structures providing facilities for offshore oil and gas extraction and production, as well as living quarters for personnel, have always been a major concern for structural safety and comfort. As platforms become larger and more complex, the power of platform equipment also increases. Low-frequency vibrations from large equipment are difficult to attenuate during transmission through the platform structure, potentially causing resonance in localized areas. This resonance can negatively impact the normal operation of high-precision instruments and the comfort of platform personnel's working and living environment. Calculations and actual ship testing data both indicate that excessive local vibrations on platforms are often caused by vibrations of multiple line spectra. Research on multi-line spectra vibration control for offshore platforms can effectively improve platform vibration control efficiency.

[0003] Currently, when conducting dynamic vibration absorption design for offshore platforms both domestically and internationally, most studies simplify the entire platform as a single-degree-of-freedom system and focus on overall modal vibration. Research on multi-line spectrum vibration control in areas where local vibration exceeds limits is relatively limited. Existing studies mostly employ the finite element method for related calculations; however, due to the size of the finite element model of the offshore platform, repeated calculations are required during the adjustment of dynamic vibration absorption parameters, resulting in low efficiency in dynamic vibration absorption design. Summary of the Invention

[0004] Purpose of the invention: To provide a distributed dynamic vibration absorption design method for the local resonance region of an offshore platform. Based on the vibration response of the local resonance region of the offshore platform, and taking the excessive vibration line spectrum of the local resonance region as the control target, the local resonance region to be controlled is equivalent to a complex boundary numerical model, the distributed dynamic vibration absorption parameters are quickly determined, and the vibration absorption effect of the distributed dynamic vibration absorption device is quickly evaluated, thereby achieving effective control of the multi-line spectrum vibration of the local resonance region of the offshore platform.

[0005] Technical solution: A distributed dynamic vibration absorption design method for local resonance regions of offshore platforms, comprising the following steps:

[0006] (1) Determine the local resonance region and the line spectrum to be controlled based on the finite element analysis results during the design phase or the results during the actual ship test phase;

[0007] (2) Construct a numerical model of the local resonance region of the platform, and establish a numerical equivalent model of the local resonance region by adjusting the boundary spring stiffness of the numerical model;

[0008] (3) Based on the numerical equivalent model of the local resonance region of the platform, the equivalent mass of the mode to be controlled is solved quickly. Based on the combination of the equivalent mass and the optimal coherence design principle, the dynamic vibration absorption parameters are determined quickly.

[0009] (4) Based on the numerical equivalent model of the local resonance region, the vibration response of the resonant structure of the marine platform after the deployment of distributed dynamic vibration absorption is solved, so as to realize the rapid evaluation of the distributed dynamic vibration absorption effect.

[0010] (5) Adjust the dynamic vibration absorption parameters according to the vibration absorption effect before and after the deployment of the distributed dynamic vibration absorption until the vibration absorption effect meets the design requirements, and form a distributed dynamic vibration absorption design scheme for the local resonance area of ​​the marine platform.

[0011] Furthermore, step (1) includes the following steps:

[0012] (1-1) If it is in the design stage, establish a finite element analysis model of the platform, carry out vibration response analysis of the platform, and determine the vibration exceeding the standard area of ​​the platform and the control line spectrum that causes the vibration to exceed the standard based on the response analysis results;

[0013] (1-2) If it is in the actual ship testing stage, determine the local vibration exceeding the standard area of ​​the platform and the control line spectrum that causes the vibration to exceed the standard based on the actual ship vibration test results of the offshore platform.

[0014] Furthermore, step (2) includes the following steps:

[0015] (2-1) A numerical model of the local resonance region of the platform is constructed based on the energy method. The energy functional of the numerical model includes the typical structural kinetic energy, strain energy and boundary virtual spring potential energy.

[0016] (2-2) Based on the principle of similar dynamic characteristics, by adjusting the boundary constraint spring stiffness of the numerical model in the local resonance region, when the natural frequency of the numerical truncated model coincides with the resonance peak frequency of the platform vibration response curve, the equivalent of the numerical truncated model in the local resonance region of the platform is achieved.

[0017] Furthermore, step (3) includes the following steps:

[0018] (3-1) Based on the numerical equivalent model of the local resonance region of the platform in step (2), the natural frequency of the local resonance region of the complex boundary can be calculated quickly: after adding the mass to the dynamic vibration absorption placement position of the local resonance region, the natural frequency of the structure is recalculated, and the equivalent mass of the dynamic vibration absorption placement position is calculated according to the change of the natural frequency and the added mass.

[0019] (3-2) Based on the numerical equivalent model of the local resonance region of the platform in step (2), perform iterative calculations to quickly solve the equivalent mass under different additional masses: with the additional mass as the horizontal axis and the equivalent mass as the vertical axis, fit a curve, and the intersection of the curve with the Y-axis is the high-precision equivalent mass of the dynamic vibration absorption placement position under this mode.

[0020] (3-3) Based on the equivalent mass calculated in the previous step, the equivalent mass of the dynamic vibration absorption placement position in the local resonance area of ​​the platform is compared with that of a single-degree-of-freedom vibration system, and the dynamic vibration absorption parameters are quickly determined by combining the optimal coherence design principle.

[0021] (3-4) For the modes corresponding to the controllable line spectra that cause vibration to exceed the standard in step 1, solve for the equivalent mass according to steps (3-1)-(3-3) and calculate the dynamic vibration absorption parameters.

[0022] Furthermore, step (3-3) treats the equivalent mass obtained in step (3-2) as a single-degree-of-freedom system and calculates the ratio between the dynamic vibration-absorbing mass and the equivalent mass. This ratio is the mass ratio:

[0023] μ=m / M n

[0024] In the formula, the dynamic vibration absorption mass is represented by m, and the mass ratio is represented by μ;

[0025] When vibration displacement is the control target, the optimal frequency ratio is determined according to the following formula:

[0026]

[0027] In the formula, ω i The frequency at which the vibration is absorbed by the engine;

[0028] The stiffness k of the dynamic vibration absorption spring can be determined based on the dynamic vibration absorption frequency.

[0029]

[0030] Similarly, the dynamic damping coefficient c is solved according to the following formula:

[0031]

[0032] When vibration acceleration is the control target, the optimal frequency ratio is determined according to the following formula.

[0033]

[0034] The stiffness k of the dynamic vibration absorption spring can be determined based on the dynamic vibration absorption frequency.

[0035]

[0036] The dynamic vibration absorption damping coefficient c can be solved using the following formula:

[0037]

[0038] Furthermore, step (4) includes the following steps:

[0039] (4-1) Based on the numerical model of the local resonance region of the platform constructed by the energy method in step (2), considering the relative displacement between dynamic vibration absorption and the main structure, the dynamic vibration absorption is simplified into three parts: spring, mass, and damping. The energy functional of the main structure-dynamic vibration absorption coupling model is reconstructed.

[0040] (4-2) Substitute the dynamic vibration absorption parameters determined in step (3) into the main structure-dynamic vibration absorption coupled vibration analysis model, solve the vibration response after considering dynamic vibration absorption and multi-mode coupling of the main structure, and evaluate the vibration control effect.

[0041] Furthermore, step (4-1) yields the energy functional of the main structure-dynamic vibration absorption coupling model;

[0042]

[0043] In the formula, L Y Let k represent the principal structure energy functional. r Let m be the spring stiffness for the r-th dynamic vibration absorption. r Let c be the mass of the r-th dynamic vibration-absorbing spring. r For the damping of the r-th dynamic vibration absorption, z r For dynamic vibration absorption along vertical displacement, w r This refers to the vertical displacement of the main structure at the location where the dynamic vibration damping system is installed.

[0044] Furthermore, in step (4-2), the dynamic vibration absorption parameters are substituted into the main structure-dynamic vibration absorption coupling model (4-1) to solve the vibration response at the test points of the main structure under external load. The test points should be uniformly selected on the main structure. The vibration response at different test points is averaged to characterize the overall vibration effect of the main structure. The energy averaging formula is as follows:

[0045]

[0046] By comparing the vibration response at the control line of the main structure before and after the deployment of the dynamic vibration absorption device, the vibration control effect of the dynamic vibration absorption device can be obtained.

[0047] Furthermore, step (5) includes the following steps:

[0048] (5-1) Based on the multi-line spectrum vibration control evaluation effect obtained in step (4), determine whether the control objective is met. If the control objective is met, if the control line spectrum drops to meet the specification requirements, and the peak values ​​of the newly generated line spectrum do not exceed the control line spectrum, then a distributed dynamic vibration absorption design scheme for the local resonance area of ​​the marine platform is formed.

[0049] (5-2) If the control objective is not met, the dynamic vibration absorption mass ratio is adjusted to increase the dynamic vibration absorption mass ratio. The dynamic vibration absorption frequency ratio and damping ratio are adjusted accordingly according to step (3). The distributed dynamic vibration absorption parameters that meet the multi-line spectrum control effect after adjustment and optimization are re-substituted into the main structure-dynamic vibration absorption coupled vibration analysis model to determine the vibration absorption effect and form a distributed dynamic vibration absorption design scheme for the local resonance area of ​​the marine platform.

[0050] Beneficial effects: This invention uses the main equipment excitation source as input based on numerical calculation methods to predict the platform's vibration exceeding the standard, overcoming the low calculation efficiency of traditional dynamic vibration absorption design methods. For the controllable line spectrum in the exceeding area, a numerical equivalent model of the platform's local resonance area is constructed based on the energy method, which effectively improves the efficiency of solving the equivalent mass of the local controllable area. Combined with the optimal coherence design principle, the dynamic vibration absorption parameters are quickly determined. Finally, the dynamic vibration absorption effect is verified by the finite element method, avoiding repeated iterative calculations based on the large-scale finite element numerical model of the platform, which can significantly improve the control efficiency of the line spectrum vibration in the local resonance area of ​​the marine platform. Attached Figure Description

[0051] Figure 1 This is a flowchart of the method of the present invention;

[0052] Figure 2 The spectrum diagram of the local resonance region to be controlled;

[0053] Figure 3 A schematic diagram illustrating the process of establishing a numerical equivalent model for the region to be controlled.

[0054] Figure 4 A schematic diagram of the equivalent process of the truncation model of the local resonance region of the platform;

[0055] Figure 5 This is a schematic diagram showing the location of antinodes in a certain order array.

[0056] Figure 6 Solve for the curve of equivalent quality;

[0057] Figure 7 This is a comparison chart showing the effect of the line spectrum control before and after control.

[0058] Figure 8 Design scheme for distributed dynamic vibration absorption in local resonance areas of offshore platforms;

[0059] Figure 9 Comparison of cloud maps of the controlled area of ​​the platform before and after the deployment of the dynamic vibration absorption system at the controlled frequency. Detailed Implementation

[0060] A distributed dynamic vibration absorption design method for local resonance regions of offshore platforms, such as Figure 1 As shown, the specific process is as follows:

[0061] Step 1

[0062] (1.1) If in the design phase, first, based on the basic structural diagram and general layout diagram of the offshore platform, analyze the structural thickness at different locations of the main structures and establish a geometric simulation model. Determine the mesh size based on the upper limit frequency of the assessment, and perform mesh generation to obtain the finite element model of the platform. Analyze the dimensions, power, and other parameters of the main equipment on the platform, and estimate the excitation loads on the equipment based on specifications, or determine the load values ​​based on the measured data of similar equipment according to the equipment parameters. Apply loads to the bases of the main equipment on the platform, and perform vibration response calculations within the assessment frequency band using the explicit dynamic solver in the finite element software. Based on the finite element vibration response cloud map, determine the local resonance region of the platform, analyze the vibration response at the local resonance region, and then determine the controllable spectrum. Figure 2 It can be seen that the vibration exceeding the standard area of ​​the offshore platform is located in the superstructure area, and the exceeding line spectrum is 12Hz and 19Hz respectively.

[0063] (1.2) If the test is in the actual ship testing phase, vibration tests shall be conducted strictly in accordance with the specifications by deploying vibration accelerometers at measuring points in typical test areas according to the established test plan, and the measurement time, measurement conditions and other parameters shall be recorded. After the test, the local resonance exceeding the standard area of ​​the platform shall be identified through post-processing of the actual ship test data, and the control line spectrum of the area shall be determined.

[0064] Step 2: Based on the analysis results of Step 1, establish a numerical model of the local resonance region of the platform:

[0065] (2.1) To improve the design efficiency of distributed dynamic vibration absorption in the local uncontrolled region, a numerical equivalent model of the uncontrolled region is established according to the geometric dimensions of the uncontrolled region and the energy method. The energy functional of the uncontrolled region includes structural strain energy, kinetic energy, work done by external forces, and potential energy of the boundary virtual spring. The numerical model establishment process refers to... Figure 3 .

[0066] By substituting the allowable displacement function into the energy functional and performing variational processing on the energy functional of the plate frame structure using the Ritz method, the coefficients of the allowable displacement function are obtained. Substituting these coefficients into the terms of the Fourier series yields the structural vibration response. When the work done by the external force is zero, substituting the obtained allowable displacement function into the terms of the Fourier series yields the structural mode shape.

[0067] (2.2) By adjusting the virtual spring stiffness of the numerical model, combinations of different boundary conditions in the local controllable region can be achieved. When the natural frequency corresponding to the mode shape of the local controllable region is consistent with the frequency of the controllable line spectrum of the vibration response at the local resonance region in the overall model finite element, it indicates that the numerical model under this boundary condition is equivalent to the truncated model of the local resonance region of the platform. The equivalence process is described in reference [reference needed]. Figure 4 .

[0068] Step 3: Based on Step 2, the equivalent mass of the controllable mode is quickly solved using the numerical model of the local resonance region of the platform, and the dynamic vibration absorption parameters are quickly determined.

[0069] (3.1) Based on the mode shape corresponding to the line spectrum to be controlled in the previous step, select the placement position of the dynamic vibration absorption device. The placement position should be as close as possible to the antinode of the corresponding mode shape. The positions of the antinodes of the 12Hz and 19Hz modes are referenced. Figure 5 After determining the placement location of the dynamic vibration absorption device, an additional mass Δm (kg) is added at the placement location. The natural frequency is calculated based on the numerical equivalent model of the platform's local resonance region. The nth natural frequency after adding the mass is represented as ω. n (rad / s), the nth natural frequency of the platform in the local resonance region without added mass is expressed as Ω. n (rad / s), the equivalent mass M at this location n Solve using the following formula:

[0070]

[0071] (3.2) To further improve the accuracy of the equivalent mass solution, based on the numerical equivalent model in step 2, the equivalent mass of the dynamic vibration absorption placement position is solved by iterative calculations to change the additional mass multiple times. A curve is fitted with the additional mass as the horizontal axis and the corresponding solved equivalent mass as the vertical axis. The intersection of this curve with the Y-axis represents the final equivalent mass of the dynamic vibration absorption placement position. The equivalent mass solution curve is shown below. Figure 6 As shown. Calculations show that the equivalent mass corresponding to the 12Hz line spectrum in the control region is 7348.5 kg, and the equivalent mass corresponding to the 19Hz line spectrum is 4026.7 kg.

[0072] (3.3) Treating the equivalent mass obtained in step (3.2) as a single-degree-of-freedom system, the ratio between the dynamic vibration-absorbing mass and the equivalent mass is obtained. This ratio is the mass ratio:

[0073] μ = m / M n

[0074] In the formula, the dynamic vibration absorption mass is represented by m, and the mass ratio is represented by μ;

[0075] When the dynamic vibration absorption mass ratio is 0.02, the masses of the dynamic vibration absorption devices corresponding to the 12Hz and 19Hz line spectra in the control region are determined to be 147kg and 80.5kg, respectively. Taking vibration acceleration as the control target, the optimal dynamic vibration absorption frequency ratio is obtained by substituting into the corresponding formula. Then, the stiffness and damping of the dynamic vibration absorption device corresponding to the 12Hz line spectra in the control region are 819126.1N / m and 1891N.s / m, respectively; and the stiffness and damping of the dynamic vibration absorption device corresponding to the 19Hz line spectra in the control region are 1125242.3N / m and 1640.6Ns / m, respectively.

[0076] Step 4

[0077] (4.1) The dynamic vibration absorption device is simplified to consist of three parts: spring, mass, and damping. The dynamic vibration absorption device only moves in the vertical direction. The shape function of the dynamic vibration absorption device is expressed as a form that changes with time. Considering the displacement difference between the dynamic vibration absorption device and the area to be controlled, the kinetic energy, strain energy, and damping energy consumption of the dynamic vibration absorption device are expressed separately. Based on the numerical equivalent model of the platform local resonance region truncated model in step 2, considering the energy of the dynamic vibration absorption device, the energy functional of the main structure-dynamic vibration absorption coupling model is obtained.

[0078]

[0079] In the formula, L Y Let k represent the principal structure energy functional. r Let m be the spring stiffness for the r-th dynamic vibration absorption. r Let c be the mass of the r-th dynamic vibration-absorbing spring. r For the damping of the r-th dynamic vibration absorption, z r For dynamic vibration absorption along vertical displacement, w r This refers to the vertical displacement of the main structure at the location where the dynamic vibration damping system is installed.

[0080] (4.2) Substitute the dynamic vibration absorption parameters obtained in step (3.3) into the main structure-dynamic vibration absorption coupling model in (4.1) to solve the vibration response at the test points of the main structure under external load. N test points should be uniformly selected on the main structure. The energy of the vibration response at the N test points is averaged to characterize the overall vibration effect of the main structure. The vibration response at the control line spectrum of the main structure before and after the deployment of the dynamic vibration absorption device is compared to obtain the vibration control effect of the dynamic vibration absorption device. The energy averaging formula is as follows:

[0081]

[0082] Step 5

[0083] The vibration control effect of the dynamic vibration absorption parameters obtained in step (3.3) is evaluated. The optimized dynamic vibration absorption parameters are then set in the finite element model of the offshore platform. Dynamic vibration absorption devices corresponding to the 12Hz and 19Hz line spectra in the control area are respectively deployed in... Figure 7 and Figure 8 Location, Finite Element Computation Cloud Figure 7 and Figure 8 This indicates that the vibration response at 12Hz and 19Hz was effectively controlled. Figure 9 The comparison of vibration response before and after the deployment of the medium-powered vibration-absorbing system shows that the 12Hz and 19Hz line spectra decreased by 16dB and 20.2dB respectively, and the vibration line spectra meet the platform assessment specifications.

Claims

1. A distributed dynamic vibration absorption design method for local resonance regions of an offshore platform, characterized in that: Includes the following steps: (1) Determine the local resonance region and the line spectrum to be controlled based on the finite element analysis results during the design phase or the results during the actual ship test phase; (2) Construct a numerical model of the local resonance region of the platform, and establish a numerical equivalent model of the local resonance region by adjusting the boundary spring stiffness of the numerical model; (3) Based on the numerical equivalent model of the local resonance region of the platform, the equivalent mass of the mode to be controlled is solved quickly. Based on the combination of the equivalent mass and the optimal coherence design principle, the dynamic vibration absorption parameters are determined quickly. (4) Based on the numerical equivalent model of the local resonance region, the vibration response of the resonant structure of the offshore platform after the deployment of distributed dynamic vibration absorption is solved, so as to realize the rapid evaluation of the effect of distributed dynamic vibration absorption; including the following steps: (4-1) Based on the numerical model of the local resonance region of the platform constructed by the energy method in step (2), considering the relative displacement between dynamic vibration absorption and the main structure, the dynamic vibration absorption is simplified to three parts: spring, mass, and damping. The energy functional of the main structure-dynamic vibration absorption coupling model is then reconstructed: In the formula, L Y Let k represent the principal structure energy functional. r Let m be the spring stiffness for the r-th dynamic vibration absorption. r Let c be the mass of the r-th dynamic vibration-absorbing spring. r For the damping of the r-th dynamic vibration absorption, z r For dynamic vibration absorption along vertical displacement, w r This refers to the vertical displacement of the main structure at the location of the dynamic vibration damping installation. (4-2) Substitute the dynamic vibration absorption parameters determined in step (3) into the main structure-dynamic vibration absorption coupled vibration analysis model, solve the vibration response after considering dynamic vibration absorption and multi-mode coupling of the main structure, and evaluate the vibration control effect. (5) Adjust the dynamic vibration absorption parameters according to the vibration absorption effect before and after the deployment of the distributed dynamic vibration absorption until the vibration absorption effect meets the design requirements, and form a distributed dynamic vibration absorption design scheme for the local resonance area of ​​the marine platform.

2. The distributed dynamic vibration absorption design method for local resonance regions of offshore platforms according to claim 1, characterized in that: Step (1) includes the following steps: (1-1) If it is in the design stage, establish a finite element analysis model of the platform, carry out vibration response analysis of the platform, and determine the vibration exceeding the standard area of ​​the platform and the control line spectrum that causes the vibration to exceed the standard based on the response analysis results; (1-2) If it is in the actual ship testing stage, determine the local vibration exceeding the standard area of ​​the platform and the control line spectrum that causes the vibration to exceed the standard based on the actual ship vibration test results of the offshore platform.

3. The distributed dynamic vibration absorption design method for local resonance regions of offshore platforms according to claim 1, characterized in that: Step (2) includes the following steps: (2-1) A numerical model of the local resonance region of the platform is constructed based on the energy method. The energy functional of the numerical model includes the typical structural kinetic energy, strain energy and boundary virtual spring potential energy. (2-2) Based on the principle of similar dynamic characteristics, by adjusting the boundary constraint spring stiffness of the numerical model in the local resonance region, when the natural frequency of the numerical truncated model coincides with the characteristic peak frequency of the platform vibration response curve, the equivalent of the numerical truncated model in the local resonance region of the platform is achieved.

4. The distributed dynamic vibration absorption design method for local resonance regions of offshore platforms according to claim 3, characterized in that: Step (3) includes the following steps: (3-1) Based on the numerical equivalent model of the local resonance region of the platform in step (2), the natural frequency of the local resonance region of the complex boundary can be calculated quickly: after adding the mass to the dynamic vibration absorption placement position of the local resonance region, the natural frequency of the structure is recalculated, and the equivalent mass of the dynamic vibration absorption placement position is calculated according to the change of the natural frequency and the added mass. (3-2) Based on the numerical equivalent model of the local resonance region of the platform in step (2), perform iterative calculations to quickly solve the equivalent mass under different additional masses: with the additional mass as the horizontal axis and the equivalent mass as the vertical axis, fit a curve, and the intersection of the curve with the Y-axis is the high-precision equivalent mass under the mode corresponding to the controllable line spectrum determined in step (1) for the dynamic vibration absorption placement position. (3-3) Based on the equivalent mass calculated in the previous step, the equivalent mass of the dynamic vibration absorption placement position in the local resonance area of ​​the platform is compared with that of a single-degree-of-freedom vibration system, and the dynamic vibration absorption parameters are quickly determined by combining the optimal coherence design principle. (3-4) For the modes corresponding to the controllable line spectra that cause vibration to exceed the standard in step (1), solve for the equivalent mass according to steps (3-1)-(3-3) and calculate the dynamic vibration absorption parameters.

5. The distributed dynamic vibration absorption design method for local resonance regions of offshore platforms according to claim 4, characterized in that: Step (3-3) treats the equivalent mass obtained in step (3-2) as a single-degree-of-freedom system and calculates the ratio between the dynamic vibration-absorbing mass and the equivalent mass. This ratio is the mass ratio: μ=m / M n In the formula, the dynamic vibration-absorbing mass is represented by m, the mass ratio by μ, and the equivalent mass by M. n ; (3-3-1) When vibration displacement is the control target, the optimal frequency ratio is determined according to the following formula: In the formula, ω i For the dynamic vibration absorption frequency, Ω n The nth natural frequency without added mass; Determine the stiffness k of the dynamic vibration absorption spring based on the dynamic vibration absorption frequency: The dynamic vibration absorption damping coefficient c is calculated using the following formula: (3-3-2) When vibration acceleration is the control target, the optimal frequency ratio is determined according to the following formula: Determine the stiffness k of the dynamic vibration absorption spring based on the dynamic vibration absorption frequency: The dynamic vibration absorption damping coefficient c is calculated using the following formula:

6. The distributed dynamic vibration absorption design method for local resonance regions of offshore platforms according to claim 1, characterized in that: Step (4-2) substitutes the dynamic vibration absorption parameters into the main structure-dynamic vibration absorption coupling model (4-1) to solve the vibration response at the test points of the main structure under external load. The test points should be uniformly selected on the main structure. The vibration response at different test points is averaged to characterize the overall vibration effect of the main structure. The energy averaging formula is as follows: By comparing the vibration response at the control line of the main structure before and after the deployment of the dynamic vibration absorption device, the vibration control effect of the dynamic vibration absorption device can be obtained.

7. The distributed dynamic vibration absorption design method for local resonance regions of offshore platforms according to claim 1, characterized in that: Step (5) includes the following steps: (5-1) Based on the evaluation effect of the multi-line spectrum vibration control obtained in step (4), determine whether the control objective is met. If the control objective is met, then a distributed dynamic vibration absorption design scheme for the local resonance area of ​​the marine platform is formed. (5-2) If the control objective is not met, the dynamic vibration absorption mass ratio is adjusted, the dynamic vibration absorption frequency ratio and the damping ratio are adjusted accordingly according to step 3, and the distributed dynamic vibration absorption parameters that meet the multi-line spectrum control effect after adjustment and optimization are re-substituted into the main structure-dynamic vibration absorption coupled vibration analysis model to determine the vibration absorption effect and form a distributed dynamic vibration absorption design scheme for the local resonance area of ​​the marine platform.

Images