Method for improving shock resistance of nuclear security level cabinet

Abstract

The invention is applicable to the field of nuclear power, and discloses a nuclear safety level cabinet shock resistance improving method, which comprises the following steps: modeling after a first cabinet, a second cabinet and two cabinets are connected in a combined cabinet mode, applying constraints to a model, calculating inherent frequencies of the first cabinet, the second cabinet and the first cabinet and the second cabinet after the combined cabinet is connected, and calculating the shock resistance of the first cabinet and the second cabinet after the first cabinet and the second cabinet are connected in a combined cabinet mode; through material physical performance data in the step S1, modeling in the step S2 and constraint and seismic load applying in the step S3, the overall primary film stress and local film bending stress of a first cabinet, a second cabinet and a plate-shell type supporting piece after cabinet combination, the tensile stress, shear stress and bending stress of a linear supporting piece and relative displacement between the cabinets are calculated, and the overall primary film stress and local film bending stress of the first cabinet, the second cabinet and the plate-shell type supporting piece after cabinet combination are calculated. And calculating the deformation of the first cabinet and the second cabinet which are influenced by the seismic load after the first cabinet and the second cabinet are independently placed and connected and the relative displacement after the cabinet combination connection, thereby judging whether the cabinet combination connection can avoid the cabinet collision or not and avoiding the influence on the realization of the safety function of the cabinet.

Description

Technical Field

[0001] This invention relates to the field of nuclear power, and more particularly to a method for improving the seismic resistance of nuclear safety grade cabinets. Background Technology

[0002] Nuclear power plant safety-critical electrical and instrumentation cabinets are generally designed to meet seismic resistance Class I standards. Class I seismic resistance cabinets should be able to maintain their safety functions after a safe shutdown earthquake. Currently, seismic assessment of safety-critical cabinets is typically conducted through single-cabinet assessment tests. During these tests, there are no obstructions around the cabinets. However, in actual nuclear power plant installations, space is limited, and some safety-critical cabinets are installed too close together or too close to walls. In an earthquake, the cabinets may deform and sway in different directions. Insufficient spacing can lead to collisions and impacts, damaging and rendering internal components unusable, thus affecting the cabinet's safety functions. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to provide a method for improving the seismic resistance of nuclear safety grade cabinets.

[0004] The technical solution adopted by this invention to solve its technical problem is: to construct a method for improving the seismic resistance of a nuclear safety grade cabinet, comprising the following steps: Step S1: Connect the first cabinet and the second cabinet together using a tooling, and collect data on the dimensional parameters and material physical properties of the first cabinet, the second cabinet, and the tooling. Step S2: Model the first cabinet, the second cabinet, and the cabinet after merging according to the cabinet size parameters in step S1; Step S3: Apply constraints to the models of the first cabinet and the second cabinet, as well as the cabinet after merging, in Step S2 using the finite element method, and calculate the natural frequencies of the first cabinet, the second cabinet, and the first cabinet and the second cabinet after merging. Step S4: Based on the material physical property data from Step S1, the modeling in Step S2, and the applied constraints and seismic loads in Step S3, calculate the overall primary membrane stress and local membrane-plus-bending stress of the plate-shell support components of the first and second cabinets, and the tensile stress, shear stress, and bending stress of the linear support components. If all are less than the allowable stress requirement, the structural strength of the plate-shell support components and the linear support components meets the requirements. If they are greater than the allowable stress requirement, the structural strength of the plate-shell support components and the linear support components does not meet the requirements, and the cabinet connection positions need to be redesigned. Step S5: Based on the material physical property data from Step S1, the modeling in Step S2, the applied constraints and seismic loads in Step S3, calculate the relative displacement between the first cabinet and the second cabinet. If the maximum relative displacement is less than the distance between the first cabinet and the second cabinet, then the distance between the first cabinet and the second cabinet meets the requirements. If the maximum relative displacement is greater than the distance between the first cabinet and the second cabinet, then the first cabinet and the second cabinet may collide with each other under seismic loads, affecting the realization of safety functions.

[0005] Furthermore, when the distance between the first cabinet and the second cabinet is less than 10cm, a tooling is added to the first cabinet and the second cabinet for connection. The tooling is fixed to the first cabinet and the second cabinet with bolts.

[0006] Further, in step S4, based on the selected bolt's dimensions and material physical properties, the modeling in step S2, the applied constraints in step S3, and the seismic load, the maximum tensile stress and maximum shear stress borne by the bolt are calculated. If the maximum tensile stress and maximum shear stress of the bolt are less than the bolt's allowable stress limit, and the combined stress is less than 1, then the bolt meets the requirements. If the maximum tensile stress and maximum shear stress of the bolt are greater than the bolt's allowable ultimate stress value, then the bolt does not meet the requirements, and a new bolt or connection position needs to be selected.

[0007] Furthermore, in step S3, the seismic load stress borne by the first cabinet and the second cabinet is calculated using the response spectrum method, and the specific parameters of the response spectrum are selected according to the structure of the corresponding nuclear island plant and the floor where it is located.

[0008] Furthermore, in accordance with the specific parameter requirements of the reaction spectrum of each floor of the nuclear island plant, the reaction spectrum of each floor of the nuclear island plant is calculated based on the reaction spectrum of the floor during a safe shutdown earthquake, with a damping ratio of 2%.

[0009] Furthermore, in step S4, it is necessary to obtain the allowable stress range of the plate-shell support member. The allowable stress range only involves the overall primary membrane stress σ. m And the sum of local membrane stress and primary bending stress σ m (σ l )+σ b According to the requirements and material selection of nuclear safety grade components, the overall primary membrane stress σ m ≤92.5MPa, the sum of local membrane stress and primary bending stress σ m (σ l )+σ b 1.5 times σ m That is, σ m (σ l )+σ b ≤138.75MPa.

[0010] Furthermore, in step S4, according to the requirements and material selection of nuclear safety grade components, the allowable stress range of the linear support includes the allowable tensile stress. F t Allowable shear stress F v Allowable bending stress F b The units are all in MPa, and the calculation formula is: ; ; ; In the formula, S y S is the allowable stress of the material. u Let be the allowable yield strength of the material, and in the formula, represents the minimum of the two values.

[0011] Furthermore, the long side of the first and second cabinets after being combined is the X direction, the short side is the Z direction, the height direction of the first and second cabinets is the Y direction, and the allowable composite stress ratio of the linear support component needs to be less than 1. The formula for calculating the allowable composite stress ratio is: ; In the formula, f by This represents the stress applied in the Y direction during actual bending. F by The allowable bending stress in the Y direction for a linear support member. f bz This represents the stress applied in the Z direction to the actual bending stress. F bz The allowable bending stress in the Z direction for a linear support member. f by 、F by 、f bz 、F bz All units are in MPa.

[0012] Furthermore, in step S2, the linear support model of the first and second cabinets, as well as the cabinets connected in parallel, is simulated using beam element Beam188, while the shell support model of the first and second cabinets, as well as the cabinets connected in parallel, is simulated using shell element Shell181. The model is appropriately simplified, and the mass of the electrical components inside the first and second cabinets is evenly distributed on the linear support model.

[0013] Furthermore, in step S2, the boundary conditions between the first cabinet and the second cabinet are six degrees of freedom at the connection bolts between the cabinet and the ground foundation.

[0014] The present invention provides a method for improving the seismic resistance of nuclear safety grade cabinets, which has the following beneficial effects: Modeling is performed on the first cabinet, the second cabinet, and the cabinet after merging them. Constraints are applied to the model, and the natural frequencies of the first cabinet, the second cabinet, and the cabinet after merging are calculated. Using the material physical property data from step S1, the modeling in step S2, the applied constraints in step S3, and the seismic load, the overall primary membrane stress and local membrane-plus-bending stress of the plate-shell support components of the first and second cabinets, the tensile stress, shear force, and bending stress of the linear support components, and the maximum displacement of the cabinets are calculated. The deformation and displacement of the first and second cabinets, as well as the cabinet after merging, are calculated after the first and second cabinets are affected by seismic loads, thereby determining whether the existing cabinet installation location will collide under earthquake conditions, and whether the cabinets after merging will no longer collide. Attached Figure Description

[0015] To more clearly illustrate the technical solution of the present invention, the present invention will be further described below in conjunction with the accompanying drawings and embodiments. It should be understood that the following drawings only show some embodiments of the present invention and therefore should not be considered as a limitation of the scope. For those skilled in the art, other related drawings can be obtained from these drawings without creative effort. In the drawings: Figure 1 This is a flowchart of a method for improving the seismic resistance of a nuclear safety grade cabinet according to one embodiment of the present invention; Figure 2 This is a modeling diagram of the plate-shell support component of the first cabinet in a method for improving the seismic resistance of a nuclear safety grade cabinet according to one embodiment of the present invention; Figure 3 This is a linear support modeling diagram of the first cabinet in a method for improving the seismic resistance of a nuclear safety grade cabinet according to one embodiment of the present invention; Figure 4 This is a modeling diagram of the plate-shell support component of the second cabinet in a method for improving the seismic resistance of a nuclear safety grade cabinet according to one embodiment of the present invention; Figure 5 This is a linear support modeling diagram of the second cabinet of a method for improving the seismic resistance of a nuclear safety grade cabinet according to one embodiment of the present invention; Figure 6 This is a mode shape diagram of a linear support component in a method for improving the seismic resistance of a nuclear safety grade cabinet according to one embodiment of the present invention; Figure 7 This is a vibration mode diagram of a plate-shell support component in a method for improving the seismic resistance of a nuclear safety-grade cabinet according to one embodiment of the present invention; Figure 8 This is a stress distribution cloud map of a linear support component in a method for improving the seismic resistance of a nuclear safety grade cabinet according to one embodiment of the present invention; Figure 9 This is an overall displacement cloud diagram of the first cabinet plate-shell support component in a method for improving the seismic resistance of a nuclear safety grade cabinet according to one embodiment of the present invention; Figure 10 This is an overall displacement cloud diagram of the first cabinet linear support component in a method for improving the seismic resistance of a nuclear safety grade cabinet according to one embodiment of the present invention; Figure 11 This is an overall displacement cloud diagram of the second cabinet plate shell support component in a method for improving the seismic resistance of a nuclear safety grade cabinet according to one embodiment of the present invention; Figure 12 This is an overall displacement cloud diagram of the linear support component of the second cabinet, which is a method for improving the seismic resistance of a nuclear safety-grade cabinet according to one embodiment of the present invention. Detailed Implementation

[0016] To provide a clearer understanding of the technical features, objectives, and effects of the present invention, specific embodiments of the present invention will now be described in detail with reference to the accompanying drawings. In the following description, it should be understood that the orientations or positional relationships indicated by terms such as "upper," "inner," and "outer" are based on the orientations or positional relationships shown in the accompanying drawings, and are constructed and operated in a specific orientation. They are only for the convenience of describing the technical solution and do not indicate that the device or element referred to must have a specific orientation; therefore, they should not be construed as limitations on the present invention.

[0017] It should also be noted that, unless otherwise explicitly specified and limited, terms such as "installation," "connection," "fixing," and "setting" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral part; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. When an component is referred to as being "on" or "below" another component, the component can be located "directly" or "indirectly" on the other component, or there may be one or more intermediary components. The terms "first," "second," "third," etc., are only for the convenience of describing this technical solution and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, features defined with "first," "second," "third," etc., may explicitly or implicitly include one or more of that feature. For those skilled in the art, the specific meaning of the above terms in this invention can be understood according to the specific circumstances.

[0018] Figures 1 to 12This invention illustrates a method for enhancing the seismic resistance of nuclear safety grade cabinets in one embodiment. This method can be used to improve the safety performance of cabinets inside nuclear power plants during earthquake accidents, and may include the following steps: Step S1: Connect the first cabinet and the second cabinet together using a tooling, and collect data on the dimensional parameters and material physical properties of the first cabinet, the second cabinet, and the tooling. Step S2: Perform finite element modeling on the first cabinet, the second cabinet, and the cabinet after merging according to the cabinet size parameters in step S1; Step S3: Apply constraints to the models of the first and second cabinets in step S2, and calculate the natural frequencies of the first cabinet, the second cabinet, and the first and second cabinets after being combined into one cabinet. Step S4: Based on the material physical property data from Step S1, the modeling in Step S2, and the applied constraints and seismic loads in Step S3, calculate the overall primary membrane stress and local membrane-plus-bending stress of the plate-shell support components of the first cabinet, the second cabinet, and the cabinet after merging, as well as the tensile stress, shear stress, and bending stress of the linear support components. If all are less than the allowable stress requirement, the structural strength of the plate-shell support components and the linear support components meets the requirements. If they are greater than the allowable stress requirement, the structural strength of the plate-shell support components and the linear support components does not meet the requirements, and the cabinet connection positions need to be redesigned. Step S5: Based on the material physical property data from Step S1, the modeling in Step S2, the constraint application in Step S3, and the seismic load, calculate the relative displacement between the first cabinet and the second cabinet. If the maximum relative displacement is less than the distance between the first cabinet and the second cabinet, then the distance between the first cabinet and the second cabinet meets the requirements. If the maximum relative displacement is greater than the distance between the first cabinet and the second cabinet, then the first cabinet and the second cabinet may collide with each other under the seismic load, and the cabinet connection position needs to be adjusted.

[0019] By modeling the first cabinet, the second cabinet, and the cabinet after merging, and applying constraints to the models, the natural frequencies of the first cabinet, the second cabinet, and the cabinet after merging the first and second cabinets are calculated. Using the material physical property data from step S1, the modeling in step S2, the constraints in step S3, and the seismic load, the overall primary membrane stress and local membrane plus bending stress of the plate-type support components of the first cabinet, the second cabinet, and the cabinet after merging, as well as the tensile stress, shear force, and bending stress of the linear support components, and the relative displacement between the first and second cabinets, the deformation and displacement of the first and second cabinets after being affected by the seismic load are calculated to determine whether the existing cabinet installation location will collide under an earthquake, and whether the cabinets after merging will no longer collide.

[0020] In one specific embodiment, referring to the data and dimensions in Tables 1 and 2, both the first and second cabinets are frame structures with steel plate skins. Before merging, the distance between the first and second cabinets is 30mm. During merging, two 50mm×50mm×4mm equilateral angle steels are used to create a fixture on top of the cabinets to connect them. The first cabinet has a total weight of 1600kg and is connected to the ground using four M20×60mm 8.8 grade bolts; the second cabinet has a total weight of 400kg and is connected to the ground using four M16×50mm 8.8 grade bolts.

[0021] Furthermore, the dimensions of the first cabinet are 780mm×600mm×2200mm, and the dimensions of the second cabinet are 1000mm×600mm×2200mm.

[0022] In one specific embodiment, the profiles and steel plates of the first cabinet, the second cabinet, and the tooling are all calculated according to Q235B.

[0023] Furthermore, the selection and performance of the steel profiles for the first and second cabinets are referenced in Tables 1, 2, and 3. Table 1. Material List for the First Cabinet Table 2. List of Materials for the Second Cabinet Table 3 Material Mechanical Properties In one specific embodiment, the finite element method is used to analyze the modes of the first cabinet, the second cabinet, and the cabinets after merging. Taking their own weight into account, the natural frequencies of the first cabinet and the second cabinet are calculated separately, and then the natural frequencies of the overall structure after merging the first cabinet and the second cabinet are calculated.

[0024] Furthermore, the modal analysis results using the finite element method show that the first 12 natural frequencies of the first cabinet are 21.045Hz, 22.469Hz, 29.952Hz, 30.16Hz, 30.702Hz, 33.074Hz, 33.652Hz, 34.923Hz, 36.05Hz, 36.738Hz, 38.381Hz, and 38.845Hz, respectively. Among them, the 16th natural frequency has the largest mass contribution in the X direction, corresponding to a frequency of 46.9266Hz; the 44th natural frequency has the largest mass contribution in the Y direction, corresponding to a frequency of 85.6111Hz; and the 13th natural frequency has the largest mass contribution in the Z direction, corresponding to a frequency of 43.0093Hz.

[0025] The first 12 natural frequencies of the second rack are 9.3033Hz, 9.587Hz, 11.774Hz, 13.31Hz, 15.39Hz, 18.268Hz, 18.642Hz, 20.322Hz, 21.041Hz, 23.802Hz, 25.719Hz, and 25.974Hz. Among them, the 6th order has the largest mass contribution in the X direction, corresponding to a frequency of 18.268Hz; the 18th order has the largest mass contribution in the Y direction, corresponding to a frequency of 34.014Hz; and the 34th order has the largest mass contribution in the Z direction, corresponding to a frequency of 51.844Hz.

[0026] After merging the first and second cabinets, the first 12 natural frequencies of the overall structure are 9.3077Hz, 9.5341Hz, 11.772Hz, 13.212Hz, 15.396Hz, 18.276Hz, 18.499Hz, 20.313Hz, 21.041Hz, 21.067Hz, 22.558Hz, and 23.767Hz. Among these, the 49th frequency, with the largest mass contribution in the X-direction, corresponds to 51.092Hz. (Example of modal characteristics follows.) Figure 6 and 7 As shown, the 116th order has the largest mass contribution in the Y direction, corresponding to a frequency of 87.517 Hz; the 41st order has the largest mass contribution in the Z direction, corresponding to a frequency of 44.621 Hz.

[0027] Since the first-order natural frequencies of both the cabinets before and after merging are below 33Hz, the response spectrum method is used to calculate the stress caused by seismic loads. Modal analysis extracted all modes in the cabinet frequency range of 0~150Hz, and the number of modes extracted by the response spectrum analysis is sufficient.

[0028] Figures 2 to 5 The illustration shows that in one embodiment, when the distance between the first cabinet and the second cabinet is less than 10cm, a tooling is added to the first cabinet and the second cabinet for connection. The tooling is fixed to the first cabinet and the second cabinet with bolts. The tooling fixes the first cabinet and the second cabinet respectively to prevent the top of the first cabinet and the second cabinet from colliding with each other.

[0029] Figures 2 to 5In one embodiment, step S4 shows that the maximum tensile stress and maximum shear stress of the bolt can be calculated based on the selected bolt's external dimensions and material physical properties, the modeling in step S2, the applied constraints and seismic loads in step S3. If the maximum tensile stress and maximum shear stress of the bolt are less than the bolt's allowable limit stress value and the combined stress is less than 1, then the bolt meets the requirements. If the maximum tensile stress and maximum shear stress of the bolt are greater than the bolt's allowable limit stress value, then the bolt does not meet the requirements and the bolt or connection position needs to be reselected, as shown in Table 4.

[0030] In one specific embodiment, calculated separately for the first cabinet, the second cabinet, and the combined cabinet configuration, the maximum tensile force of a single bolt in the first cabinet is 4223N, the maximum shear force is 1342N, and the effective area of ​​the bolt is 225mm². 2 The maximum tensile force of a single bolt in the second cabinet is 1510N, the maximum shear force is 453N, and the effective area of ​​the bolt is 114mm². 2 Therefore, the maximum tensile stress and maximum shear stress of the bolt can be calculated.

[0031] The maximum tensile stress is: The maximum shear stress is Based on the calculated bolt tensile and shear stresses and their corresponding limits, the combined stress of the bolt can be calculated. In summary, the tensile stress, shear stress, and combined stress of the bolt all meet the requirements of the specification.

[0032] Step S3 in one embodiment may include calculating the seismic load stress borne by the first cabinet and the second cabinet using the response spectrum method, with specific parameters selected according to the corresponding nuclear island building structure and the floor level.

[0033] In one embodiment, the reaction spectrum of the nuclear island plant floor may include the specific parameter requirements of the reaction spectrum of the nuclear island plant floor, calculated according to the reaction spectrum of the floor during a safe shutdown earthquake, with a damping ratio of 2.

[0034] Figure 1 Step S4, as shown in one embodiment, may include obtaining the allowable stress range for the plate-shell support, referring to Table 4, where the allowable stress range only relates to the overall primary membrane stress σ. mAnd the sum of local membrane stress and primary bending stress σ m (σ l )+σ b According to the requirements and material selection of nuclear safety grade components, the overall primary membrane stress σ m ≤92.5MPa, the sum of local membrane stress and primary bending stress σ m (σ l )+σ b 1.5 times σ m That is, σ m (σ l )+σ b ≤138.75MPa.

[0035] Table 4 Allowable Stress Limits for Plate and Shell Supports Step S4, in one embodiment, may include, referring to Table 5, specifying that, according to the requirements and material selection of nuclear safety grade components, the allowable stress range of the linear support includes the allowable tensile stress. F t Allowable shear stress F v Allowable bending stress F b The units are all in MPa, and the calculation formula is: ; ; ; In the formula, S y S is the allowable stress of the material. u Let be the allowable yield strength of the material, and in the formula, represents the minimum of the two values.

[0036] Table 5 Allowable stress limits for linear support components Figure 6 , Figure 7 and Figure 8 The diagram shows that in one embodiment, the first and second cabinets may be combined, with the long side direction (X-direction) and the short side direction (Z-direction) of the first and second cabinets, and the height direction (Y-direction) of the first and second cabinets. The allowable composite stress ratio of the linear support component needs to be less than 1, and the formula for calculating the allowable composite stress ratio is: ; In the formula, f by This represents the stress applied in the Y direction during actual bending. F byThe allowable bending stress in the Y direction for a linear support member. f bz This represents the stress applied in the Z direction to the actual bending stress. F bz The allowable bending stress in the Z direction for a linear support member. f by 、F by 、f bz 、F bz All units are in MPa.

[0037] In one specific embodiment, analysis based on the data in Tables 1 to 5 shows that the membrane stress is mainly generated by internal pressure. Since the cabinet does not bear pressure, the membrane stress generated under its own weight and seismic loads is very small and can be ignored. The local membrane stress plus bending stress of the first cabinet, the second cabinet, the combined structure of the first and second cabinets, and the connecting angle steel are 38.417 MPa, 36.06 MPa, 31.35 MPa, and 5.41 MPa, respectively, all far less than the allowable stress of 92.5 MPa. Therefore, the structural strength of the shell-type support components before and after cabinet consolidation meets the requirements of the standard specifications.

[0038] In one specific embodiment, the stress of the linear support is analyzed according to the data in Tables 1 to 3, and the stress calculation is shown in Tables 6, 7 and 8 below.

[0039] Table 6. Stress Assessment Results of Linear Support Components for the First Cabinet Table 7. Stress Assessment Results of Linear Support Components for the Second Cabinet Table 8. Stress Assessment Results of Linear Support Components After Cabinet Integration In one specific embodiment, the data from Tables 1 to 3 show that before merging the first and second cabinets, their maximum displacements in the X direction were 0.175mm and 1.156mm, respectively; after merging, their maximum displacements in the X direction were 0.163mm and 1.195mm, respectively. Conservatively assuming relative movement of the first and second cabinets under seismic loads, the maximum relative displacement before merging was calculated to be 1.331mm, and the maximum relative displacement after merging was calculated to be 1.358mm. Therefore, the relative gap between the first and second cabinets after merging is less than 30mm, and no collision will occur between them.

[0040] Figures 2 to 5 In one embodiment, step S2 may include simulating the linear support model of the first cabinet and the second cabinet using a beam element Beam188, and simulating the plate-shell support model and tooling model of the first cabinet and the second cabinet using a shell element Shell181. The mass of the electrical components in the first cabinet and the second cabinet is set to be evenly distributed on the linear support.

[0041] Figures 2 to 5 Step S2, as shown in one embodiment, may include the boundary conditions between the first cabinet and the second cabinet as constraining the six degrees of freedom at the connection bolts between the cabinet and the ground foundation.

[0042] The above analysis and evaluation show that, under the load combinations of various operating conditions specified in the standard, the stress before and after merging the first and second cabinets is less than the specified limit, meeting the requirements of the RCC-M standard. Furthermore, no collision will occur between the first and second cabinets after merging. Meanwhile, to meet the requirement that "two cabinets less than 10cm apart should be merged," connecting the cabinets with 50mm×50mm×4mm angle steel will suffice to meet the cabinet's seismic resistance requirements.

[0043] It is understood that the above embodiments only illustrate preferred embodiments of the present invention, and their descriptions are relatively specific and detailed, but they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can freely combine the above technical features without departing from the concept of the present invention, and can also make several modifications and improvements, all of which fall within the protection scope of the present invention. Therefore, all equivalent transformations and modifications made with respect to the scope of the claims of the present invention should fall within the scope of the claims of the present invention.

Claims

1. A method for improving the seismic resistance of a nuclear safety grade cabinet, characterized in that, Includes the following steps: Step S1: Connect the first cabinet and the second cabinet together using a tooling, and collect data on the dimensional parameters and material physical properties of the first cabinet, the second cabinet, and the tooling. Step S2: Model the first cabinet, the second cabinet, and the two cabinets connected together according to the cabinet size parameters in step S1. Step S3: Apply constraints to the models of the first cabinet and the second cabinet, and the combined cabinet model, in Step S2 using the finite element method, and calculate the natural frequencies of the first cabinet, the second cabinet, and the combined first cabinet and the second cabinet model. Step S4: Based on the material physical property data from Step S1, the modeling in Step S2, and the constraints and seismic loads in Step S3, calculate the overall primary membrane stress and local membrane plus bending stress of the first cabinet, the second cabinet, and the plate-type support after cabinet consolidation, as well as the tensile stress, shear stress, and bending stress of the linear support. If all are less than the allowable stress requirement, the structural strength of the plate-type support and the linear support meets the requirements. If they are greater than the allowable stress requirement, the structural strength of the plate-type support and the linear support does not meet the requirements, and the cabinet connection position needs to be redesigned. Step S5: Based on the material physical property data from Step S1, the modeling in Step S2, the constraints in Step S3, and the seismic load, calculate the relative displacement between the first cabinet and the second cabinet. If the maximum relative displacement is less than the original distance between the first cabinet and the second cabinet, then the distance between the first cabinet and the second cabinet meets the requirements. If the maximum relative displacement is greater than the distance between the first cabinet and the second cabinet, then the first cabinet and the second cabinet may collide with each other under seismic load.

2. The method for improving the seismic resistance of a nuclear safety grade cabinet according to claim 1, characterized in that, In step S1, when the distance between the first cabinet and the second cabinet is less than 10cm, the connection is made at the top of the first cabinet and the second cabinet, and the connecting fixture is fixed to the first cabinet and the second cabinet with bolts.

3. The method for improving the seismic resistance of a nuclear safety grade cabinet according to claim 2, characterized in that, In step S4, based on the selected bolt's dimensions and material physical properties, the modeling in step S2, the applied constraints and seismic loads in step S3, the maximum tensile stress and maximum shear stress borne by the bolt are calculated. If the maximum tensile stress and maximum shear stress of the bolt are less than the bolt's allowable limit stress value, the bolt meets the requirements. If the maximum tensile stress and maximum shear stress of the bolt are greater than the bolt's allowable limit stress value, the bolt does not meet the requirements, and a new bolt needs to be selected or the cabinet connection position needs to be adjusted.

4. The method for improving the seismic resistance of a nuclear safety grade cabinet according to claim 1, characterized in that, In step S3, the seismic load stress borne by the first cabinet and the second cabinet, as well as the cabinets connected together, is calculated using the response spectrum method. The response spectrum is selected according to the specific parameters of the corresponding nuclear island plant structure and the floor.

5. The method for improving the seismic resistance of a nuclear safety grade cabinet according to claim 4, characterized in that, According to the specific parameter requirements of the reaction spectrum of each floor of the nuclear island plant, the reaction spectrum of each floor of the nuclear island plant is calculated based on the reaction spectrum of the floor during a safe shutdown earthquake, with a damping ratio of 2%.

6. The method for improving the seismic resistance of a nuclear safety grade cabinet according to claim 1, characterized in that, In step S4, it is necessary to obtain the allowable stress range of the plate-shell support. The allowable stress range only involves the overall primary membrane stress σ. m And the sum of local membrane stress and primary bending stress σ m (σ l )+σ b According to the requirements and material selection of nuclear safety grade components, the overall primary membrane stress σ m ≤92.5MPa, the sum of local membrane stress and primary bending stress σ m (σ l )+σ b 1.5 times σ m That is, σ m (σ l )+σ b ≤138.75MPa.

7. The method for improving the seismic resistance of a nuclear safety grade cabinet according to claim 1, characterized in that, In step S4, according to the requirements and material selection of nuclear safety grade components, the allowable stress of the linear support includes the allowable tensile stress. F t Allowable shear stress F v Allowable bending stress F b The units are all in MPa, and the calculation formula is: ; ; ; In the formula, S y S is the allowable stress of the material. u Let be the allowable yield strength of the material, and in the formula, represents the minimum value of the two.

8. The method for improving the seismic resistance of a nuclear safety grade cabinet according to claim 7, characterized in that, The long side of the first and second cabinets after being combined is the X direction, the short side is the Z direction, and the height direction of the first and second cabinets is the Y direction. The allowable composite stress ratio of the linear support components needs to be less than 1. The formula for calculating the allowable composite stress ratio is: ; In the formula, f by This represents the stress applied in the Y direction during actual bending. F by The allowable bending stress in the Y direction for a linear support member. f bz This represents the stress applied in the Z direction to the actual bending stress. F bz The allowable bending stress in the Z direction for a linear support member. f by 、F by 、f bz 、F bz All units are in MPa.

9. The method for improving the seismic resistance of a nuclear safety grade cabinet according to claim 1, characterized in that, In step S2, the linear support model of the first cabinet, the second cabinet, and the cabinet after they are connected is simulated by the beam element Beam188, and the shell support model of the first cabinet, the second cabinet, and the cabinet after they are connected is simulated by the shell element Shell181. The model is simplified, and the mass of the electrical components in the first cabinet and the second cabinet is evenly distributed on the linear support.

10. A method for improving the seismic resistance of a nuclear safety grade cabinet according to claim 1, characterized in that, In step S2, the applied boundary conditions constrain the six degrees of freedom at all connection bolts between the cabinet and the ground foundation.

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