A method for predicting and reducing vibration of nuclear items caused by cooling tower collapse

Abstract

The present invention relates to the field of collapse vibration reduction design technology, specifically a method for predicting and reducing vibration of nuclear items caused by the collapse of a cooling tower. The present invention provides a scientific basis for evaluating the impact of the collapse of a cooling tower on surrounding nuclear items by clearly setting the vibration area, obtaining key cooling tower and site parameters, and using the horizontal vibration acceleration response spectrum function and vertical vibration acceleration response spectrum function of nuclear items to calculate the corresponding vibration acceleration. Then, it is flexibly determined whether a shear thickening liquid needs to be set as a buffer layer according to actual conditions, which not only improves the pertinence and economy of the design, but also ensures the accuracy and effectiveness of the buffer layer setting through the fine simulation of the finite element model, and more accurately calculates the thickness of the buffer layer.

Description

Technical Field

[0001] The invention relates to the technical field of collapse damping design, and in particular to a method for predicting and damping vibration of nuclear items caused by the collapse of a cooling tower. Background Art

[0002] The cooling tower of a nuclear power plant is an important component of a nuclear power plant. Its main function is to dissipate the heat generated during the power generation process into the air through the circulation of water, thereby maintaining the normal operating temperature of the nuclear reactor.

[0003] The cooling towers commonly used in nuclear power plants currently have the following characteristics:

[0004] Cooling towers are large-scale thin-walled structures that may collapse under the influence of accidental factors such as earthquakes, causing ground vibrations. Such vibrations are characterized by large amplitude, wide range and long duration.

[0005] The height of newly built cooling towers is constantly increasing, and the current tallest natural ventilation cooling tower is over 200m high.

[0006] Due to site limitations, the cooling tower of a nuclear power plant is only about 300 meters away from the nuclear island containing the reactor. If the cooling tower collapses due to a strong earthquake or other factors, the vibration caused by it touching the ground may endanger the safe operation of the nuclear island.

[0007] From the above three characteristics, it can be seen that the ground vibration caused by the collapse of the cooling tower will affect the normal operation of the nuclear island. Therefore, in order to avoid this situation, a buffer layer is usually set in the area where the cooling tower collapses. The buffering and shock-absorbing effect of the buffer layer can reduce the vibration intensity caused by the collapse of the cooling tower. In the process of laying the buffer layer at this stage, in order to improve the vibration reduction performance as much as possible, the staff usually lays a thicker buffer layer at the bottom of the cooling tower to meet the vibration reduction requirements to the greatest extent. However, this method has a more obvious defect, that is, the waste of materials, which leads to excess vibration reduction performance, so it needs to be solved urgently. Summary of the invention

[0008] In order to avoid and overcome the technical problems existing in the prior art, the present invention provides a method for predicting and reducing vibration of nuclear items caused by the collapse of a cooling tower. The present invention can more accurately calculate the thickness of the cushion layer.

[0009] To achieve the above object, the present invention provides the following technical solutions:

[0010] A method for predicting and reducing vibration of nuclear items caused by cooling tower collapse includes the following design steps:

[0011] S1. Obtain and use building parameters to calculate the theoretical vibration acceleration of each building when the cooling tower collapses and causes vibrations in surrounding buildings;

[0012] S2. Compare the relationship between each theoretical vibration acceleration and the standard vibration acceleration range; if all theoretical vibration accelerations are within the standard vibration acceleration range, then there is no need to set a shear thickening liquid as a buffer layer in the collapsed area below the cooling tower; otherwise, set a shear thickening liquid as a buffer layer in the collapsed area below the cooling tower according to steps S3-S6;

[0013] S3. According to the structure of the cooling tower, a "cooling tower-foundation" finite element model is established, and the finite element model is used to calculate the peak value of the ground vibration acceleration caused in the vibration area when the cooling tower collapses, and the peak value of the ground vibration acceleration is recorded as a reference value;

[0014] S4. Select a corresponding type of shear thickening fluid as a cushion layer, and set multiple thicknesses from thin to thick; construct a "cooling tower-shear thickening fluid-foundation" finite element model based on the structural design of the cushion layer and the cooling tower; use the finite element model to calculate the peak value of ground vibration acceleration caused in the vibration area when the cooling tower collapses when using cushion layers of different thicknesses, and record the peak value of ground vibration acceleration as a predicted value;

[0015] S5. Compare the differences between the predicted values ​​and the reference values ​​in order from thin to thick. When the difference reaches the vibration reduction requirement, the thickness corresponding to the difference is recorded as the target thickness of the current cushion layer.

[0016] S6. A corresponding type of shear thickening fluid having a thickness not less than the target thickness is provided as a buffer layer within the collapse range below the cooling tower.

[0017] As a further solution of the present invention: the specific content of step S1 is as follows:

[0018] S11, taking the location of the cooling tower as the center and setting the distance as the radius to draw a circle, and setting the area within the circle as the set vibration area;

[0019] S12, obtaining the building parameters of each nuclear item in the vibration area, the building parameters including the building damping ratio and the building natural vibration period;

[0020] S13. Calculate the theoretical horizontal vibration acceleration of the nuclear item in the horizontal direction through the building horizontal vibration acceleration response spectrum function, and calculate the theoretical vertical vibration acceleration of the nuclear item in the vertical direction through the building vertical vibration acceleration response spectrum function;

[0021] As a further solution of the present invention: the building horizontal vibration acceleration response spectrum function is specifically expressed as follows:

[0022] ;

[0023] ;

[0024] ;

[0025] ;

[0026] ;

[0027] ;

[0028] ;

[0029] ;

[0030] ;

[0031] ;

[0032] In the formula, Indicates the theoretical horizontal vibration acceleration; It represents the maximum value of the building vibration influence coefficient in the horizontal direction, dimensionless;

[0033] It represents the correction factor of the maximum value of the vibration influence coefficient, dimensionless; It represents the natural vibration period of the building, in seconds;

[0034] It indicates the period value at the end of the rising section of the building horizontal vibration acceleration response spectrum function curve, in seconds; It indicates the period value at the end of the horizontal section of the building horizontal vibration acceleration response spectrum function curve, in seconds;

[0035] It represents the attenuation index of the descending section of the building horizontal vibration acceleration response spectrum function curve, dimensionless; represents the building damping ratio, dimensionless;

[0036] The building damping ratio correction coefficient representing the building horizontal vibration acceleration response spectrum function curve, dimensionless; Indicates the distance correction parameter in the horizontal direction when the cooling tower collapses;

[0037] It indicates the soil stiffness correction parameter in the horizontal direction when the cooling tower collapses; It represents the collapse correction parameter in the horizontal direction when the cooling tower collapses. It is dimensionless.

[0038] Indicates the tower type correction parameters in the horizontal direction when the cooling tower collapses; Indicates the balance parameters in the horizontal direction when the cooling tower collapses;

[0039] It represents the shear wave velocity of the soil in the vibration area, in m / s; Indicates the mass of the cooling tower in kg;

[0040] Indicates the height of the cooling tower in m; Indicates the distance from the cooling tower to the target building, that is, the vibration radius of the cooling tower, in meters;

[0041] The specific expression of the building vertical vibration acceleration response spectrum function is as follows:

[0042] ;

[0043] ;

[0044] ;

[0045] ;

[0046] ;

[0047] ;

[0048] ;

[0049] ;

[0050] ;

[0051] In the formula, Indicates the theoretical vertical vibration acceleration; It indicates the period value at the end of the rising section of the building vertical vibration acceleration response spectrum function curve, in seconds;

[0052] It indicates the period value at the end of the horizontal section of the vertical vibration acceleration response spectrum function curve of the building, in seconds; It represents the attenuation index of the descending section of the vertical vibration acceleration response spectrum function curve of the building, dimensionless;

[0053] The building damping ratio correction coefficient representing the building vertical vibration acceleration response spectrum function curve, dimensionless; It represents the maximum value of the building vibration influence coefficient in the vertical direction, dimensionless;

[0054] It represents the distance correction parameter in the vertical direction when the cooling tower collapses, dimensionless; It represents the soil stiffness correction parameter in the vertical direction when the cooling tower collapses, dimensionless;

[0055] It represents the collapse mode correction parameter in the vertical direction when the cooling tower collapses, dimensionless; It represents the tower type correction parameter in the vertical direction when the cooling tower collapses, dimensionless;

[0056] It represents the equilibrium parameter in the vertical direction when the cooling tower collapses. It is dimensionless.

[0057] As a further solution of the present invention: the cycle value calculation formula is as follows:

[0058] ;

[0059] ;

[0060] In the formula, Represents a natural constant, dimensionless.

[0061] As a further solution of the present invention: when comparing the theoretical vibration acceleration with the standard vibration acceleration range, the standard vibration acceleration range is divided into a standard horizontal vibration acceleration range and a standard vertical vibration acceleration range, and then the theoretical horizontal vibration acceleration is compared with the standard horizontal vibration acceleration range, and the theoretical vertical vibration acceleration is compared with the standard vertical vibration acceleration range at the same time; if both theoretical vibration accelerations fall within the corresponding standard vibration acceleration ranges, there is no need to set a shear thickening liquid as a buffer layer in the collapse area below the cooling tower; otherwise, it is necessary to set a shear thickening liquid as a buffer layer in the collapse area below the cooling tower.

[0062] As a further solution of the present invention: the specific content of step S3 is as follows:

[0063] S31, obtaining the design drawings of the cooling tower and inputting them into the corresponding finite element analysis software; restoring the cooling tower in the finite element analysis software on a one-to-one basis, thereby establishing a "cooling tower-foundation" finite element model;

[0064] S32. Set the collapse type of the cooling tower in the "cooling tower-foundation" finite element model, analyze the peak value of the ground vibration acceleration caused in the vibration area when the cooling tower collapses under each collapse type, and record the peak value of the ground vibration acceleration as a reference value.

[0065] As a further solution of the present invention: the specific content of step S4 is as follows:

[0066] S41, obtaining the design drawings of the cooling tower, selecting different types of shear thickening fluids, and then inputting them into the corresponding finite element analysis software; in the finite element analysis software, a circular foundation pit coaxially arranged with the cooling tower is dug on the foundation of the collapsed area below the cooling tower, and the shear thickening fluid is poured into the foundation pit to form a buffer layer, and the cooling tower and the buffer layer are restored in a one-to-one ratio, and a "cooling tower-shear thickening fluid-foundation" finite element model is established;

[0067] S42. In the "cooling tower-shear thickening fluid-foundation" finite element model, the type of shear thickening fluid is first set, and then the thickness of the buffer layer is set from thin to thick. Finally, the peak value of the ground vibration acceleration caused in the vibration area when the cooling tower collapses at each thickness is calculated, and the peak value of the ground vibration acceleration is recorded as a reference value.

[0068] As a further solution of the present invention: the specific content of step S5 is as follows:

[0069] S51, obtaining various reference values ​​and predicted values;

[0070] S52. Compare the differences between the predicted values ​​and reference values ​​of each thickness of the current type of shear thickening fluid under the same collapse type in order from thin to thick. When the difference reaches the vibration reduction requirement, the thickness corresponding to the difference is recorded as the target thickness of the current type of shear thickening fluid.

[0071] As a further solution of the present invention: the specific content of step S6 is as follows:

[0072] S61, selecting a type of shear thickening fluid and a target thickness of its corresponding buffer layer;

[0073] S62, a circular foundation pit coaxially arranged outside the actual cooling tower and having a depth of the target thickness;

[0074] S63. Fill the foundation pit with the selected shear thickening liquid, and the laying of the cooling tower collapse cushion layer is now completed.

[0075] As a further solution of the present invention: the finite element analysis software adopted is LS-DYNA.

[0076] Compared with the prior art, the present invention has the following beneficial effects:

[0077] 1. The present invention achieves effective reduction of the vibration caused by the collapse of the cooling tower and touching the ground through scientific calculation and precise simulation. First, the impact of the collapse of the cooling tower on the surrounding buildings is evaluated through theoretical calculation, and then it is flexibly decided whether to set up a shear thickening liquid as a buffer layer according to the actual situation. This not only improves the pertinence and economy of the design, but also ensures the accuracy and effectiveness of the buffer layer setting through the fine simulation of the finite element model, and more accurately calculates the thickness of the buffer layer.

[0078] 2. By clearly setting the vibration area, obtaining key building parameters, and using the building horizontal vibration acceleration response spectrum function and the building vertical vibration acceleration response spectrum function for accurate calculation, a scientific basis is provided for evaluating the impact of the cooling tower collapse on surrounding buildings. The accuracy and reliability of the theoretical vibration acceleration calculation are improved, providing a more accurate decision-making basis for whether to set up a shear thickening fluid as a buffer layer in the future.

[0079] 3. By providing specific calculation formulas for the period value, the scientificity and practicality of the design method are further enhanced. These formulas are based on natural constants and physical parameters such as soil shear wave velocity, and can accurately reflect the influence of soil characteristics in the vibration area on the vibration period. This helps to calculate the theoretical vibration acceleration more accurately, thereby improving the accuracy and reliability of the entire design method.

[0080] 4. By subdividing the standard vibration acceleration range into horizontal vibration and vertical vibration, and comparing them with the corresponding theoretical vibration acceleration, the accuracy and pertinence of the assessment are further improved. This method can more comprehensively consider the impact of the collapse of the cooling tower on the surrounding buildings in different directions, thereby ensuring the rationality and effectiveness of the buffer layer setting.

[0081] 5. Using finite element analysis software to restore the cooling tower on a one-to-one basis and establish a "cooling tower-foundation" finite element model can accurately simulate the actual structure and foundation conditions of the cooling tower, providing a reliable basis for subsequent calculation of the peak value of ground vibration acceleration. At the same time, by considering different types of collapse, the comprehensiveness and safety of the design are further improved.

[0082] 6. The effectiveness and reliability of the cushion layer in practical applications can be ensured by selecting the type of shear thickening fluid, opening the foundation pit, and pouring the shear thickening fluid. At the same time, by clarifying the depth and shape of the foundation pit, the accuracy and safety of the design are further improved.

[0083] 7. By specifying LS-DYNA as the finite element analysis software, the scientificity and advancement of the design method are further improved. As a powerful finite element analysis software, LS-DYNA can accurately simulate complex physical processes and provide strong support for the analysis of cooling tower collapse vibration and the design of buffer pads. This helps to ensure the accuracy and reliability of the design results and reduce risks in practical applications. BRIEF DESCRIPTION OF THE DRAWINGS

[0084] Figure 1 It is the overall design flow chart of the present invention.

[0085] Figure 2 It is a schematic diagram of the cooling tower arrangement structure in the present invention.

[0086] Figure 3 It is the ground horizontal vibration acceleration distribution diagram of each measuring point in the present invention.

[0087] Figure 4 It is the ground vertical vibration acceleration distribution diagram of each measuring point in the present invention.

[0088] Figure 5 It is a viscosity curve diagram of corn starch with a mass fraction of 55% in the present invention.

[0089] In the figure: 1. Cooling tower; 2. Buffer cushion; 3. Foundation; 4. Site where nuclear items are located. DETAILED DESCRIPTION

[0090] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0091] See also Figure 1 to Figure 4 In an embodiment of the present invention, a method for predicting and reducing vibration of nuclear items caused by cooling tower collapse includes the following design steps:

[0092] 1. Calculate the theoretical vibration acceleration.

[0093] Obtain and use building parameters to calculate the theoretical vibration acceleration of each building when the cooling tower collapses and causes vibrations in the surrounding buildings. The specific calculation process is as follows:

[0094] S11, such as Figure 2As shown, a cooling tower 1 is installed on a foundation 3, and a buffer layer 2 is provided below the cooling tower 1. A circle is drawn with the location of the cooling tower 1 as the center and the distance between the cooling tower and the site 4 where the nuclear item is located as the radius, and the area within the circle is set as the vibration area.

[0095] S12. Obtain the construction parameters of each nuclear item in the vibration area, including the building damping ratio and the building natural vibration period. In this embodiment, the distance between the nuclear item and the cooling tower 1 is 300m, the building damping ratio of the nuclear item is 5%, and the building natural vibration period of the nuclear island is 1.2s. The foundation in this embodiment is designed with reference to the "Engineering Rock Classification Standard", and the soil shear wave velocity of the foundation 3 is 1200m / s. The cushion layer 2 composed of shear thickening fluid is arranged in the vibration area and is coaxially arranged with the cooling tower 1. At the same time, there is a distance between the cooling tower 1 arranged on the foundation 3 and the nuclear island. The total height of the cooling tower 1 selected in this embodiment is 220m, and the total mass is 5.5309×10 7 kg, the tower type of cooling tower 1 contains 48 pairs of pillars, the pillar diameter is 1.4m, and it is 88m away from the central axis of cooling tower 1. The collapse form is fragmentary collapse.

[0096] S13. The theoretical horizontal vibration acceleration of the nuclear item in the horizontal direction is calculated by the building horizontal vibration acceleration response spectrum function. At the same time, the theoretical vertical vibration acceleration of the nuclear item in the vertical direction is calculated by the building vertical vibration acceleration response spectrum function.

[0097] The building horizontal vibration acceleration response spectrum function is specifically expressed as follows:

[0098] ;

[0099] ;

[0100] ;

[0101] ;

[0102] ;

[0103] ;

[0104] ;

[0105] ;

[0106] ;

[0107] ;

[0108] ;

[0109] ;

[0110] After sorting out the above data, the architectural parameters corresponding to the cooling tower are shown in Table 1.

[0111] Table 1 Building parameters corresponding to cooling tower

[0112] ;

[0113] Based on the data in Table 1, the theoretical horizontal vibration acceleration is calculated as shown in Table 2.

[0114] Table 2 Theoretical horizontal vibration acceleration

[0115] ;

[0116] Based on the calculation results in Table 2, it can be seen that the natural vibration period of the nuclear island building is satisfy: , so the theoretical horizontal vibration acceleration .

[0117] The building vertical vibration acceleration response spectrum function is specifically expressed as follows:

[0118] ;

[0119] ;

[0120] ;

[0121] ;

[0122] ;

[0123] ;

[0124] ;

[0125] ;

[0126] ;

[0127] Based on the data in Table 1, the theoretical vertical vibration acceleration is calculated as shown in Table 3.

[0128] Table 3 Theoretical vertical vibration acceleration

[0129] ;

[0130] Based on the calculation results in Table 2, it can be seen that the natural vibration period of the nuclear island is satisfy: , so the theoretical vertical vibration acceleration .

[0131] 2. Determine whether a buffer layer is needed.

[0132] In this embodiment, it is assumed that the nuclear item under consideration is a single degree of freedom system, and the operational safety ground vibration acceleration limit is 75gal, that is, the upper limits of the standard horizontal vibration acceleration range and the standard vertical vibration acceleration range divided into the standard vibration acceleration range are both 75gal.

[0133] Based on the analysis results in Tables 2 and 3, it can be seen that the collapse of the cooling tower in the current state will affect the safe operation of nuclear items, and a shear thickening liquid buffer layer needs to be set up.

[0134] 3. Obtain the reference value of ground vibration acceleration.

[0135] According to the frame structure of the cooling tower, a "cooling tower-foundation" finite element model is established, and the finite element model is used to calculate the peak value of the ground vibration acceleration caused in the vibration area when the cooling tower collapses, and the peak value of the ground vibration acceleration is recorded as a reference value. The specific process is as follows:

[0136] S31. Obtain the design drawings of the cooling tower and input them into the finite element analysis software LS-DYNA; restore the cooling tower in LS-DYNA on a one-to-one basis to establish a "cooling tower-foundation" finite element model.

[0137] S32. Set the collapse type of the cooling tower in the "cooling tower-foundation" finite element model, and analyze the ground vibration acceleration peak value caused in the vibration area when the cooling tower collapses under each collapse type, and record the ground vibration acceleration peak value as a reference value. Specifically:

[0138] In the "cooling tower-foundation" finite element model, the Kobe earthquake wave is applied to the bottom of the cooling tower, and the peak acceleration is scaled to 1.0g. At this time, the cooling tower collapses as a whole under the Kobe earthquake wave. Considering that the distance between the cooling tower and the nuclear island is 300m, the acceleration measurement points are evenly set on a circle 300m away from the center of the cooling tower in the "cooling tower-foundation" finite element model, and a total of 36 measurement points are set around the cooling tower at intervals of 10°. The distribution of ground horizontal vibration acceleration at each measurement point obtained through simulation is shown in the figure below. Figure 3 As shown in the figure, the distribution of ground vertical vibration acceleration at each measuring point is as follows: Figure 4 Based on Figure 3 and Figure 4By arranging the data in, we can get the maximum acceleration value and the average acceleration value of the measuring point as shown in Table 4.

[0139] Table 4 Vibration acceleration of measuring points

[0140] ;

[0141] At this time, according to the data in Table 4, the reference value of the horizontal vibration acceleration of the ground is 57.4 gal, and the reference value of the vertical vibration acceleration of the ground is 104 gal.

[0142] 4. Obtain the predicted value of ground vibration acceleration.

[0143] Select the corresponding type of shear thickening fluid as the cushion layer, and set multiple thicknesses from thin to thick; based on the structural design of the cushion layer and the cooling tower, construct a "cooling tower-shear thickening fluid-foundation" finite element model; use the finite element model to calculate the peak value of the ground vibration acceleration caused in the vibration area when the cooling tower collapses when using cushion layers of different thicknesses, and record the peak value of the ground vibration acceleration as the predicted value. The specific process is as follows:

[0144] S41. Obtain the design drawings of the cooling tower, select different types of shear thickening fluids, and then input them into the corresponding finite element analysis software; in the finite element analysis software, a circular foundation pit coaxially arranged with the cooling tower is dug on the foundation of the collapsed area below the cooling tower, and the shear thickening fluid is poured into the foundation pit to form a cushion layer, and the cooling tower and the cushion layer are restored in a one-to-one ratio, and a "cooling tower-shear thickening fluid-foundation" finite element model is established. In this embodiment, the preferred shear thickening fluid is corn starch with a mass fraction of 55%, and its viscosity curve is as follows Figure 5 As shown, candidate thicknesses are 1 m, 2 m, 3 m, ..., 20 m.

[0145] S42. In the "cooling tower-shear thickening fluid-foundation" finite element model, first set the type of shear thickening fluid, then set the thickness of the cushion layer from thin to thick, and finally calculate the peak value of the ground vibration acceleration caused in the vibration area when the cooling tower collapses at each thickness, and record the peak value of the ground vibration acceleration as the predicted value.

[0146] 5. Obtain target thickness.

[0147] In order from thin to thick, the differences between each predicted value and the reference value are compared in turn. When the difference reaches the vibration reduction requirement, the thickness corresponding to the difference is recorded as the target thickness of the current cushion layer. The specific process is as follows:

[0148] S51. Acquire various reference values ​​and predicted values ​​during the simulation process.

[0149] S52. Compare the differences between the predicted values ​​and reference values ​​of the thicknesses of the current type of shear thickening fluid under the same collapse type in order of the thickness of the cushion layer from thin to thick. When the difference reaches the vibration reduction requirement, the thickness corresponding to the difference is recorded as the target thickness of the current type of shear thickening fluid.

[0150] By comparison, the optimal depth is 4m, that is, the target thickness of the buffer layer with a mass fraction of 55% corn starch is 4m.

[0151] Based on the vibration acceleration data in Table 4 and the vibration acceleration data obtained by simulation, a data comparison is established as shown in Table 5.

[0152] Table 5 Comparison of vibration acceleration

[0153] ;

[0154] It can be seen from Table 5 that the provision of the buffer layer in this embodiment can effectively reduce the ground contact vibration caused by the collapse of the large cooling tower.

[0155] 6. Set up a buffer layer.

[0156] A corresponding type of shear thickening fluid with a thickness not less than the target thickness is set as a buffer layer within the collapse range below the cooling tower. The specific process is as follows:

[0157] S61. Select a type of shear thickening fluid and its corresponding target thickness of the buffer layer; for example, select corn starch with a mass fraction of 55% as the buffer layer, and set its target thickness to 4m.

[0158] S62. A circular foundation pit with a coaxial arrangement and a depth of 4m is opened below the actual cooling tower.

[0159] S63. Fill the foundation pit with corn starch with a mass fraction of 55%. At this time, the laying of the cooling tower collapse cushion layer is completed.

[0160] The present invention achieves effective reduction of the vibration caused by the collapse of the cooling tower and touching the ground through scientific calculation and precise simulation. First, the impact of the collapse of the cooling tower on the surrounding buildings is evaluated through theoretical calculation, and then it is flexibly decided whether to set up a shear thickening liquid as a cushion layer according to the actual situation. This not only improves the pertinence and economy of the design, but also ensures the accuracy and effectiveness of the cushion layer setting through the fine simulation of the finite element model, and more accurately calculates the thickness of the cushion layer.

[0161] The above description is only a preferred specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any technician familiar with the technical field can make equivalent replacements or changes according to the technical scheme and inventive concept of the present invention within the technical scope disclosed by the present invention, which should be covered by the protection scope of the present invention.

Claims

1. A method for predicting and reducing vibration of nuclear items caused by cooling tower collapse, characterized in that: The design steps include: S1. Calculate the theoretical vibration acceleration of each nuclear item around the cooling tower when it collapses; S2. According to the relationship between the theoretical vibration acceleration and the standard vibration acceleration range, a shear thickening liquid is set as a buffer layer under the cooling tower; the details are as follows: When comparing the theoretical vibration acceleration with the standard vibration acceleration range, the standard vibration acceleration range is divided into a standard horizontal vibration acceleration range and a standard vertical vibration acceleration range, and then the theoretical horizontal vibration acceleration is compared with the standard horizontal vibration acceleration range, and the theoretical vertical vibration acceleration is compared with the standard vertical vibration acceleration range; if both theoretical vibration accelerations fall within the corresponding standard vibration acceleration range, then there is no need to set a shear thickening fluid as a buffer layer in the collapse area below the cooling tower; Otherwise, it is necessary to set a shear thickening fluid as a cushion in the collapsed area below the cooling tower; S3. According to the structure of the cooling tower, a "cooling tower-foundation" finite element model is established, and the peak value of the ground vibration acceleration caused by the collapse of the cooling tower is calculated using the finite element model, and the peak value is marked as a reference value; S4. Determine the material type of the buffer layer and construct a "cooling tower-shear thickening fluid-foundation" finite element model; use the finite element model to calculate the peak value of the ground vibration acceleration caused by the collapse of the cooling tower when using buffer layers of different thicknesses, and mark it as a predicted value; S5, comparing the differences between the corresponding predicted values ​​and the reference values ​​in order of the thickness of the cushion layer from thin to thick; When the difference reaches the vibration reduction requirement, the cushion thickness corresponding to the difference is recorded as the target thickness of the current cushion; S6. A corresponding type of shear thickening fluid having a thickness not less than the target thickness is provided as a buffer layer within the collapse range below the cooling tower.

2. The method for predicting and reducing vibration of nuclear items caused by cooling tower collapse according to claim 1 is characterized in that: The specific content of step S1 is as follows: S11, taking the location of the cooling tower as the center and setting the distance as the radius to draw a circle, and setting the area within the circle as the vibration area; S12, obtaining the building damping ratio and building natural vibration period of each nuclear item in the vibration area; S13. The theoretical horizontal vibration acceleration of the nuclear item in the horizontal direction is calculated by the building horizontal vibration acceleration response spectrum function. At the same time, the theoretical vertical vibration acceleration of the nuclear item in the vertical direction is calculated by the building vertical vibration acceleration response spectrum function.

3. The method for predicting and reducing vibration of nuclear items caused by cooling tower collapse according to claim 2, characterized in that: The building horizontal vibration acceleration response spectrum function is specifically expressed as follows: ； ； ； ； ； ； ； ； ； ； In the formula, Indicates the theoretical horizontal vibration acceleration; Indicates the maximum value of the building vibration influence coefficient in the horizontal direction; Indicates the correction factor of the maximum value of the vibration influence coefficient; represents the natural vibration period of the building; It indicates the period value at the end of the rising section of the building horizontal vibration acceleration response spectrum function curve; It indicates the period value at the end of the horizontal section of the building horizontal vibration acceleration response spectrum function curve; It represents the attenuation index of the descending section of the building horizontal vibration acceleration response spectrum function curve; represents the building damping ratio; The building damping ratio correction coefficient representing the building horizontal vibration acceleration response spectrum function curve; Indicates the distance correction parameter in the horizontal direction when the cooling tower collapses; It indicates the soil stiffness correction parameter in the horizontal direction when the cooling tower collapses; It represents the collapse correction parameter in the horizontal direction when the cooling tower collapses. It is dimensionless. Indicates the tower type correction parameters in the horizontal direction when the cooling tower collapses; Indicates the balance parameters in the horizontal direction when the cooling tower collapses; represents the soil shear wave velocity in the vibration area; Indicates the quality of the cooling tower; Indicates the height of the cooling tower; Indicates the distance from the cooling tower to the target building, that is, the vibration radius of the cooling tower; The specific expression of the building vertical vibration acceleration response spectrum function is as follows: ； ； ； ； ； ； ； ； ； In the formula, Indicates the theoretical vertical vibration acceleration; It indicates the period value at the end of the rising section of the building vertical vibration acceleration response spectrum function curve; It indicates the period value at the end of the horizontal section of the vertical vibration acceleration response spectrum function curve of the building; It represents the attenuation index of the descending section of the vertical vibration acceleration response spectrum function curve of the building; The building damping ratio correction coefficient representing the building vertical vibration acceleration response spectrum function curve; Indicates the maximum value of the building vibration influence coefficient in the vertical direction; Indicates the distance correction parameter in the vertical direction when the cooling tower collapses; It indicates the soil stiffness correction parameter in the vertical direction when the cooling tower collapses; Indicates the collapse mode correction parameter in the vertical direction when the cooling tower collapses; Indicates the tower type correction parameters in the vertical direction when the cooling tower collapses; It indicates the balance parameters in the vertical direction when the cooling tower collapses.

4. The method for predicting and reducing vibration of nuclear items caused by cooling tower collapse according to claim 3 is characterized in that: The period value calculation formula is as follows: ； ； In the formula, Represents a natural constant.

5. A method for predicting and reducing vibration of nuclear items caused by cooling tower collapse according to any one of claims 1 to 4, characterized in that: The specific content of step S3 is as follows: S31, obtaining the design drawings of the cooling tower and inputting them into the corresponding finite element analysis software; restoring the cooling tower in the finite element analysis software on a one-to-one basis, thereby establishing a "cooling tower-foundation" finite element model; S32. Set the collapse type of the cooling tower in the "cooling tower-foundation" finite element model, analyze the peak value of the ground vibration acceleration caused in the vibration area when the cooling tower collapses under each collapse type, and record the peak value of the ground vibration acceleration as a reference value.

6. A method for predicting and reducing vibration of nuclear items caused by cooling tower collapse according to claim 5, characterized in that: The specific content of step S4 is as follows: S41. Based on the design drawings of the cooling tower, different types of shear thickening fluids are selected and then input into the corresponding finite element analysis software. In the finite element analysis software, a circular foundation pit coaxially arranged with the cooling tower is dug on the foundation of the collapsed area below the cooling tower, and the shear thickening fluid is poured into the foundation pit to form a cushion layer, and the cooling tower and the cushion layer are restored in a one-to-one ratio, thereby establishing a "cooling tower-shear thickening fluid-foundation" finite element model. S42. In the "cooling tower-shear thickening fluid-foundation" finite element model, first set the type of shear thickening fluid, then set the thickness of the cushion layer from thin to thick, and finally calculate the peak value of the ground vibration acceleration caused in the vibration area when the cooling tower collapses at each thickness, and record the peak value of the ground vibration acceleration as a reference value.

7. A method for predicting and reducing vibration of nuclear items caused by cooling tower collapse according to claim 6, characterized in that: The specific content of step S5 is as follows: S51, obtaining various reference values ​​and predicted values; S52. Compare the differences between the predicted values ​​and reference values ​​of the thicknesses of the current type of shear thickening fluid under the same collapse type in order of the thickness of the cushion layer from thin to thick. When the difference reaches the vibration reduction requirement, the thickness corresponding to the difference is recorded as the target thickness of the current type of shear thickening fluid.

8. The method for predicting and reducing vibration of nuclear items caused by cooling tower collapse according to claim 7, characterized in that: The specific content of step S6 is as follows: S61, selecting a type of shear thickening fluid and a target thickness of its corresponding buffer layer; S62, opening a coaxially arranged annular foundation pit with a depth of the target thickness below the actual cooling tower; S63. Fill the foundation pit with the selected shear thickening liquid, and the laying of the cooling tower collapse cushion layer is now completed.

9. A method for predicting and reducing vibration of nuclear items caused by cooling tower collapse according to claim 8, characterized in that: The finite element analysis software is LS-DYNA.

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