A method for analyzing the ground-parametric quality of large-scale power machine foundations

Abstract

The present invention discloses a method for analyzing the parametric vibration quality of a large-scale power machine foundation, which can accurately calculate the parametric vibration quality of the foundation and meet the needs of foundation design and analysis. The method steps include: establishing a finite element model of the foundation structure of a large-scale power machine; establishing a finite element model of a solid foundation; establishing a coupling relationship between the centrifuge foundation structure and the foundation soil; setting an artificial boundary outside the solid foundation soil; setting a mass foundation model and a massless foundation model respectively; constructing a white noise time-history load; based on the massless foundation model, carrying out a dynamic time-history calculation of white noise excitation; based on the mass foundation model, carrying out a dynamic time-history calculation of white noise excitation; performing spectrum analysis on the vibration displacement response obtained by white noise excitation of the massless foundation model respectively, and obtaining the peak frequency; calculating the parametric vibration quality of the foundation according to the peak frequencies obtained by the massless foundation model respectively.

Description

Technical Field

[0001] The invention relates to the technical field of vibration analysis of large-scale power machine foundations in civil engineering, and in particular to a foundation parametric vibration quality analysis method of a large-scale power machine foundation. Background Art

[0002] With the rapid development of industrial technology and social economy, more and more large-scale power machines are gradually put into use, such as ultra-large geotechnical centrifuges, high-speed steam turbines, ultra-high pressure compressors, etc. The operation of large-scale power machines requires a stable foundation support. Under the action of dynamic loads, the research on the vibration problem of the foundation cannot be ignored.

[0003] At present, there are mainly two traditional classical theoretical systems for the analysis and research of the vibration characteristics of large power machine foundations. The first is the "mass-spring-damper" theory proposed by scholars represented by DD Barkan. This theory assumes that the foundation is an inelastic rigid body with only mass, and the foundation is a massless spring and a damper that reflects the damping effect of the system. The lumped parameter model is used to analyze the vibration of the system. The second is the elastic half-space theory proposed by E. Reissner and others. This theory assumes that the foundation soil is a homogeneous, isotropic elastic half-space body, and the rigid foundation is placed on the surface of the elastic half-space body, and is analyzed using the elastic wave theory.

[0004] At present, the "Power Machinery Foundation Design Code" GB50040-2020 (hereinafter referred to as "Power Machinery Foundation Design Code") adopted in my country is mainly compiled based on the mass-elasticity-resistance theory. Conventional large-scale power machinery foundation design generally performs dynamic calculation and verification analysis based on this code, such as vibration tables, generators, crushers, and mills. With the development of finite element calculation technology, numerical simulation software is increasingly used in vibration analysis of power machinery foundations, greatly improving the calculation efficiency and accuracy of complex foundation structures.

[0005] However, as the research deepened, it was found that for large power machine foundations in complex foundations, there is still a problem of unclear values ​​of foundation parametric mass parameters. The explanation of Article 3.4.11 of the "Dynamic Code" points out: The parametric mass of soil varies greatly, about 0.43 to 2.9 times the mass of the foundation itself, and there is no obvious regularity in its relationship with the mass ratio or bottom area of ​​the foundation. Therefore, in actual analysis, the "Dynamic Code" does not give a clear foundation parametric mass, which leads to insufficient theoretical completeness in the analysis of vibration characteristics of power machine foundations. Especially for large buried power machine foundations in soft soil foundations, the foundation parametric mass has a significant impact on the vibration characteristics of the foundation, and the error in value will lead to a significant decrease in calculation accuracy. Summary of the invention

[0006] The present invention aims at the above-mentioned problems in the prior art and provides a method for analyzing the foundation parametric vibration quality of a large-scale power machine foundation. The method introduces a calculation method of white noise excitation and can accurately analyze the foundation parametric vibration quality of a large-scale power machine foundation while comprehensively reflecting the actual foundation soil effect. The method has strong practicality and scientificity.

[0007] To achieve the above objectives, the present invention adopts the following technical solutions.

[0008] A method for analyzing the ground vibration quality of a large-scale power machine foundation of the present invention comprises the following steps:

[0009] Step 1: Establish a finite element model of the large power machine infrastructure;

[0010] Step 2: Obtain detailed foundation survey data and establish a finite element model of the solid foundation soil;

[0011] Step 3: Establish the coupling relationship between the foundation structure of large power machinery and the foundation soil;

[0012] Step 4: Construct a viscoelastic artificial boundary outside the solid foundation soil model;

[0013] Step 5: Define the finite element model of the original foundation soil as the mass foundation model A, and construct the massless foundation model B based on the finite element model of the original foundation soil;

[0014] Step 6: Perform modal analysis based on the massless foundation model B to obtain the vibration mode and natural frequency of each mode of the large power machine foundation under the elastic effect of the actual foundation soil layer;

[0015] Step 7: Construct a white noise time-history load;

[0016] Step 8: Based on the massless foundation model B, carry out the dynamic time history calculation of white noise excitation;

[0017] Step 9: Perform spectrum analysis on the vibration displacement response obtained by white noise excitation to obtain the peak frequency, and compare it with the natural frequencies of each modal order obtained by the modal analysis in step 6 to check the relative deviation of the natural frequencies and verify the rationality of the model;

[0018] Step 10: Based on the massive foundation model A, carry out the dynamic time history calculation of white noise excitation;

[0019] Step 11: Perform spectrum analysis on the vibration displacement response obtained by white noise excitation of the massive foundation model A to obtain the peak frequency; calculate the foundation vibration mass according to the peak frequencies obtained from the massive foundation model A and the massless foundation model B respectively;

[0020] Step 12: Repeat steps 8-11 to calculate the foundation parametric mass of each mode.

[0021] Preferably, in step 2, the horizontal and vertical extension ranges of the solid foundation soil follow the following principles:

[0022] In the horizontal extension direction, the distance L from the outside of the large power machine foundation structure to the outside of the solid foundation shall not be less than the equivalent side length R of the foundation, that is, L ≥ R;

[0023] Among them, for the large-scale power machine foundation structure with a circular bottom area, R is the diameter; for the large-scale power machine foundation structure with a square bottom area, R is the side length; for the large-scale power machine foundation structure with a rectangular bottom area, Where A is the base area;

[0024] In the vertical extension direction, the distance from the bottom surface of the foundation to the bottom surface of the solid ground shall not be less than the buried depth H of the foundation.

[0025] Preferably, in step 2, the physical foundation is modeled in layers according to the actual soil layer distribution characteristics, taking into account the thickness and burial depth of each soil layer. The soil material parameters of the physical foundation include the dynamic elastic modulus E d , dynamic Poisson's ratio μ d The calculation method is based on the elastic wave equation and the formula is:

[0026]

[0027]

[0028] Where ρ is the mass density of the soil, which is obtained through indoor tests in the detailed survey data; v p is the compression wave velocity of each layer of soil, v s is the shear wave velocity of each soil layer, obtained through the on-site acoustic wave test in the detailed survey data.

[0029] Preferably, the coupling relationship between the large power machine foundation structure and the foundation soil is set as a non-slip constrained coupling relationship.

[0030] Preferably, in step 5, the density of the foundation soil material of the massless foundation model B is set to 0 or 0.1 kg / m 3 or less than 0.1kg / m 3 .

[0031] Preferably, in step 7, the frequency bandwidth of the white noise time-history load should be greater than the frequency range of the power machine load, the minimum time interval should be no greater than 0.01 s, and the total duration should be no less than 10 s.

[0032] Preferably, the step 12 further comprises:

[0033] Repeat steps 8-11 to calculate the foundation parametric mass of each order mode, wherein in steps 8 and 10, the direction of action of the white noise load should be consistent with the vibration deformation direction of the corresponding order mode shape obtained in step 6.

[0034] Preferably, in step 9, if the relative deviation of the checked natural frequency is equal to or less than 5%, it indicates that the natural frequencies obtained by the two methods of step 6 and step 9 are basically accurate; if the relative deviation of the checked natural frequency is greater than 5%, the model is checked and modified to recalculate.

[0035] Preferably, in step 11, the first-order foundation parametric mass m is calculated according to the following formula:

[0036]

[0037] In the formula, ω A is the mass foundation model A, ω B is the peak frequency obtained by white noise excitation of massless foundation model B, and M is the total mass of the foundation structure.

[0038] Preferably, the method is mainly applied to the buried foundation of large power machines; it can be applied to the foundation of a single main machine, and can also be applied to the combined foundation of multiple main machines.

[0039] The present invention has the following beneficial effects:

[0040] (1) Based on the structural characteristics of large and complex foundations, finite element modeling is used to improve analysis accuracy;

[0041] (2) To address the problem of ambiguity in the values ​​of foundation quality parameters in the specifications, physical foundation modeling is adopted, and a physical foundation model is constructed based on the measured foundation dynamic characteristic parameters, which is more accurate;

[0042] (3) Modal analysis and white noise excitation dynamic time history calculation are used to calculate the natural frequency and other characteristics of the foundation structure of large power machines, which are mutually verified and have higher accuracy;

[0043] (4) Based on the comparison of the calculation results with and without the foundation quality model, the accurate foundation parametric mass of each mode can be quantified, which is very scientific and practical. BRIEF DESCRIPTION OF THE DRAWINGS

[0044] Figure 1 It is a flow chart of the method steps of the present invention application.

[0045] Figure 2 It is a cross-sectional schematic diagram of a finite element model of an application example of the present invention.

[0046] Figure 3 It is a schematic diagram of the calculation results of the first-order modal analysis of the present application example.

[0047] Figure 4 It is a schematic diagram of the calculation results of the second-order modal analysis of the present application example.

[0048] Figure 5 It is a schematic diagram of the calculation results of the lateral excitation of the horizontal lateral white noise load in the example of this application.

[0049] Figure 6 It is a schematic diagram of the calculation results of the longitudinal excitation of the horizontal longitudinal white noise load in the example of this application.

[0050] Figure numerals: 1. Large power machine foundation structure; 2. Centrifuge main unit; 3. Layered foundation; 4. Binding constraints between foundations; 5. Viscoelastic artificial boundary. DETAILED DESCRIPTION

[0051] The present invention is further described below in conjunction with the accompanying drawings and specific embodiments.

[0052] like Figure 1 As shown, the present invention discloses a method for analyzing the quality of the foundation of a large-scale power machine. The method comprises the following steps:

[0053] Step 1, establish the basic structural model: establish the finite element model of the basic structure of the large power machine. Collect the drawings and materials of the basic structure to be analyzed, and use the 3D modeling software to establish the 3D geometric model of the basic structure to be analyzed; then import the 3D geometric model into the finite element calculation software, divide the grid, and assign the concrete structure material parameters.

[0054] Step 2, build a solid foundation model: build a finite element model of the solid foundation. Collect detailed survey data of the foundation where the large power machine foundation to be analyzed is located, obtain the soil layer distribution characteristics, and calculate the dynamic characteristic parameters. Build a three-dimensional geometric model of the foundation soil, import it into the finite element software and divide it into grids, and assign corresponding material parameters to each soil layer.

[0055] The horizontal and vertical extension ranges of the solid foundation soil in step 2 should be determined based on experience and trial calculations, and should follow the following principles:

[0056] (a) In the horizontal extension direction, the distance L from the outside of the foundation to the outside of the solid foundation should not be less than the equivalent side length R of the foundation, that is,

[0057] L≥R

[0058] Among them, for the base with a circular base, R is the diameter; for the base with a square base, R is the side length; for the base with a rectangular base, it is as follows

[0059]

[0060] Where A is the base area.

[0061] (b) In the vertical extension direction, the distance from the bottom surface of the foundation to the bottom surface of the solid ground should not be less than the burial depth H of the foundation.

[0062] The soil layer distribution characteristics of the physical foundation soil in step 2 mainly refer to the thickness and burial depth of each soil layer. The soil material parameters mainly include the dynamic elastic modulus E d , dynamic Poisson's ratio μ d The calculation method is based on the elastic wave equation and the formula is:

[0063]

[0064]

[0065] Where ρ is the mass density of the soil, which is obtained through indoor tests in the detailed survey data; v p is the compression wave velocity of each layer of soil, v s is the shear wave velocity of each soil layer, obtained through the on-site acoustic wave test in the detailed survey data.

[0066] Step 3, establish the structure-foundation coupling relationship: establish the coupling relationship between the foundation structure of the large power machine and the foundation soil. Use the finite element software to select the nodes on both sides of the contact surface between the foundation structure and the foundation soil, and set the non-slip constraint coupling relationship.

[0067] Step 4: Set up a viscoelastic artificial boundary: Select the outer nodes of the foundation soil through the finite element software, set the normal and horizontal spring and damping elements respectively, and construct a viscoelastic artificial boundary.

[0068] The parameters of the viscoelastic artificial boundary in step 4 include the normal and tangential stiffness K N and K T and damping C N and C T , the calculation formula is:

[0069]

[0070] C N =ρv s A B , C T =ρv s A B

[0071] In the formula, α N and α T are the stiffness coefficients in the normal and tangential directions, which can be 1.0 and 0.5 respectively; G d is the dynamic shear modulus, which can be obtained from the dynamic elastic modulus E d and dynamic Poisson's ratio μ d Calculated; S is the distance from the boundary node to the vibration source load; A B is the area represented by the nodes outside each body, which mainly depends on the size of the divided grid; v p is the compression wave velocity of each layer of soil, v s is the shear wave velocity, ρ is the mass density of the soil, and the calculation method refers to step 2.

[0072] Step 5: Define the mass foundation model A and the massless foundation model B: Modify the model, set the density ρ of the foundation soil to 0, record it as the massless foundation model B, and define the original mass foundation model A as the model mass foundation model A.

[0073] In step 5, in order to form a normal mass matrix during calculation and avoid calculation errors caused by mass being 0, the density ρ of the foundation soil material in the massless foundation model B can be set to a very small value (0.1 kg / m 3 And below), the same effect can be achieved.

[0074] Step 6: Perform modal analysis based on the massless foundation model B to obtain the vibration mode and natural frequency of each mode of the foundation considering the elastic effect of the actual foundation soil layer.

[0075] Step 7: Based on the programming software, construct a white noise time course load. The minimum time interval of the white noise time course is not greater than 0.01s, and the total duration is not less than 10s.

[0076] Step 8: Based on the massless foundation model B, apply the white noise time-history load described in step 7 to the typical base position of the foundation, carry out dynamic time-history analysis, and calculate the vibration displacement response of the typical base position.

[0077] In step 8, the load direction should be consistent with the vibration deformation direction of the first-order modal vibration type obtained in step 6.

[0078] Step 9: Perform spectrum analysis on the vibration displacement response obtained by white noise excitation to obtain the peak frequency ω B1 ; Set the peak frequency ω B1Compare with the first-order modal natural frequency ω1 obtained by the modal analysis in step 6 to check the relative deviation. If the deviation is above 5%, it indicates that the calculation error is large and the model needs to be checked and modified for recalculation. If the deviation is within 5%, it indicates that the natural frequencies obtained by the two methods are basically accurate and can be verified with each other.

[0079] Step 10: Based on the massive foundation model A, perform white noise excitation calculation in the same way as step 8.

[0080] Step 11: Perform spectrum analysis on the vibration displacement response obtained by white noise excitation of model A to obtain the peak frequency ω A1 According to ω A1 and ω B1 Calculate the foundation parametric mass m1 of the first-order mode using the following formula:

[0081]

[0082] In step 11, M is the total mass of the basic structure.

[0083] Step 12: Repeat steps 8-11, wherein the direction of the white noise load is set to be consistent with the vibration deformation direction of the second-order modal vibration mode obtained in step 6. The specific calculation order should be determined according to the characteristics of the foundation structure, and generally the first 2 to 3 orders can be calculated.

[0084] like Figures 2 to 6 As shown, it is a specific embodiment of the present application. This implementation case is an implementation plan for a large embedded centrifuge foundation. The specific implementation steps are as follows.

[0085] Step 101: Establish a basic structural model. Figure 2 As shown, three giant ultra-gravity centrifuges 2 are installed inside the large power machine foundation structure 1, and the frequency range of its dynamic load is 1Hz to 11.1Hz. The large power machine foundation structure 1 is 90m long, 30m wide, with a maximum burial depth of 20m. The foundation material is C40 concrete, and the total mass is 70323 tons.

[0086] Step 102: The outside of the large power machine foundation structure 1 is a solid foundation soil. In this embodiment, the solid foundation soil is a layered foundation 3, which has a total of four layers of typical soil, and its soil material parameters are calculated according to geological survey data; the foundation extends 60m in the horizontal direction and 30m downward.

[0087] Step 103: Setting a non-slip binding constraint 4 on the contact surface between the large power machine foundation structure 1 and the layered foundation 3.

[0088] Step 104: a viscoelastic artificial boundary 5 is set on the outside and bottom of the layered foundation, and the set spring and damping parameters are calculated according to the soil parameters.

[0089] Step 105: Define the mass foundation model A as Model A, then create a copy of the model and change the density of the four layers of soil in the foundation to 0.1 kg / m 3 , recorded as massless foundation model B.

[0090] Step 106: Perform modal analysis based on the massless foundation model B to obtain the vibration shapes of the first two modes as follows: Figure 3 , Figure 4 As shown in the figure, the first-order mode is based on horizontal transverse vibration, and the natural frequency is 6.01 Hz; the second-order mode is based on horizontal longitudinal vibration, and the natural frequency is 7.12 Hz.

[0091] Step 107: Based on MATALB software, by writing commands, a white noise time history load is constructed, whose frequency bandwidth is 0-50 Hz, total length is 10 s, and time interval is 0.01 s.

[0092] Step 108: Apply the horizontal lateral white noise load to the massless foundation model B and perform dynamic time history calculation; extract the vibration displacement response for spectrum analysis to obtain the peak frequency ω B1 =6.05Hz, such as Figure 5 shown.

[0093] Step 109: ω B1 =6.05Hz compared with the first-order modal natural frequency of 6.01Hz obtained by modal analysis, the relative deviation is 0.7%, indicating that the model setting is reasonable and the calculation results obtained by the two methods are basically consistent.

[0094] Step 110: Apply the horizontal white noise load to the mass foundation model A and perform dynamic time history calculation; extract the vibration displacement response for spectrum analysis to obtain the peak frequency ω A1 =4.10Hz, such as Figure 5 shown.

[0095] Step 111: According to the formula, the foundation parametric mass of the first-order horizontal lateral vibration mode is calculated to be 1.177 times the centrifuge foundation mass.

[0096] Step 112: Similarly, apply horizontal and longitudinal white noise loads to the massless foundation model B and the mass foundation model A, respectively, and perform spectrum analysis after obtaining the responses to obtain the peak frequency ω B2 =7.23Hz and ω A2 =5.27Hz, such as Figure 6As shown; it is calculated that the foundation parameter mass of the second-order horizontal longitudinal vibration mode is 0.779 times the centrifuge foundation mass.

[0097] The above embodiment is only a preferred technical solution of the present invention, indicating that the present invention is still applicable to a more complex multi-machine joint foundation. Those skilled in the art should understand that the technical solutions or parameters in the embodiment can be modified or replaced without departing from the principle and essence of the present invention, and all should be covered within the protection scope of the present invention.

Claims

1. A method for analyzing the ground parametric quality of a large power machine foundation, characterized in that: The method comprises the following steps: Step 1: Establish a finite element model of the large power machine infrastructure; Step 2: Obtain detailed foundation survey data and establish a finite element model of the solid foundation soil; Step 3: Establish the coupling relationship between the foundation structure of large power machinery and the foundation soil; Step 4: Construct a viscoelastic artificial boundary outside the solid foundation soil model; Step 5: Define the finite element model of the original foundation soil as the mass foundation model A, and construct the massless foundation model B based on the finite element model of the original foundation soil; Step 6: Perform modal analysis based on the massless foundation model B to obtain the vibration mode and natural frequency of each mode of the large power machine foundation under the elastic effect of the actual foundation soil layer; Step 7: Construct a white noise time-history load; Step 8: Based on the massless foundation model B, carry out the dynamic time history calculation of white noise excitation; Step 9: Perform spectrum analysis on the vibration displacement response obtained by white noise excitation to obtain the peak frequency, and compare it with the natural frequencies of each modal order obtained by the modal analysis in step 6 to check the relative deviation of the natural frequencies and verify the rationality of the model; Step 10: Based on the massive foundation model A, carry out the dynamic time history calculation of white noise excitation; Step 11: Perform spectrum analysis on the vibration displacement response obtained by white noise excitation of the massive foundation model A to obtain the peak frequency; calculate the foundation vibration mass according to the peak frequencies obtained from the massive foundation model A and the massless foundation model B respectively; Step 12: Repeat steps 8-11 to calculate the foundation parametric mass of each mode.

2. The method for analyzing the ground parametric quality of a large power machine foundation according to claim 1 is characterized in that: In step 2, the horizontal and vertical extension ranges of the solid foundation soil follow the following principles: In the horizontal extension direction, the distance L from the outside of the large power machine foundation structure to the outside of the solid foundation shall not be less than the equivalent side length R of the foundation, that is, L ≥ R; Among them, for the large-scale power machine foundation structure with a circular bottom area, R is the diameter; for the large-scale power machine foundation structure with a square bottom area, R is the side length; for the large-scale power machine foundation structure with a rectangular bottom area, Where A is the base area; In the vertical extension direction, the distance from the bottom surface of the foundation to the bottom surface of the solid ground shall not be less than the buried depth H of the foundation.

3. The ground parametric quality analysis method for a large power machine foundation according to claim 1 or 2, characterized in that: In step 2, the physical foundation is modeled in layers according to the actual soil layer distribution characteristics, taking into account the thickness and burial depth of each soil layer. The soil material parameters of the physical foundation include the dynamic elastic modulus E d , dynamic Poisson's ratio μ d The calculation method is based on the elastic wave equation and the formula is: Where ρ is the mass density of the soil, which is obtained through indoor tests in the detailed survey data; v p is the compression wave velocity of each layer of soil, v s is the shear wave velocity of each soil layer, obtained through the on-site acoustic wave test in the detailed survey data.

4. The ground parametric quality analysis method for a large power machine foundation according to claim 1 is characterized in that: The coupling relationship between the foundation structure of large power machinery and the foundation soil is set as a non-slip constraint coupling relationship.

5. The ground parametric quality analysis method for a large power machine foundation according to claim 1 is characterized in that: In step 5, the density of the foundation soil material of the massless foundation model B is set to 0 or 0.1 kg / m 3 or less than 0.1kg / m 3 .

6. The ground parametric quality analysis method for a large power machine foundation according to claim 1 is characterized in that: In step 7, the frequency bandwidth of the white noise time-history load should be greater than the frequency range of the power machine load, the minimum time interval should not be greater than 0.01 s, and the total duration should not be less than 10 s.

7. The ground parametric quality analysis method for a large power machine foundation according to claim 1 is characterized in that: The step 12 further comprises: Repeat steps 8-11 to calculate the foundation parametric mass of each order mode, wherein in steps 8 and 10, the direction of action of the white noise load should be consistent with the vibration deformation direction of the corresponding order mode shape obtained in step 6.

8. The ground parametric quality analysis method for a large power machine foundation according to claim 1 is characterized in that: In step 9, if the relative deviation of the checked natural frequency is equal to or less than 5%, it indicates that the natural frequencies obtained by the two methods of step 6 and step 9 are basically accurate; if the relative deviation of the checked natural frequency is greater than 5%, the model is checked and modified to recalculate.

9. The ground parametric quality analysis method for a large power machine foundation according to claim 1 is characterized in that: In step 11, the first-order foundation parametric mass m is calculated according to the following formula: In the formula, ω A is the mass foundation model A, ω B is the peak frequency obtained by white noise excitation of massless foundation model B, and M is the total mass of the foundation structure.

10. The ground parametric quality analysis method for a large power machine foundation according to claim 1 is characterized in that: The method is mainly applied to the buried foundation of large power machines; it can be applied to the foundation of a single main machine or to the combined foundation of multiple main machines.

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