A method and device for evaluating the safety of storage tanks under foundation settlement conditions

Abstract

The present application discloses a method for evaluating the safety of a storage tank under foundation settlement conditions, including obtaining discrete settlement data of the storage tank; performing Fourier decomposition on the discrete settlement data, converting it into a Fourier series, and determining an approximate settlement curve according to the Fourier series; calculating the magnitude of the correlation coefficient of the approximate settlement curve; based on the correlation coefficient, selecting a safety evaluation criterion for a storage tank under foundation settlement conditions based on stress control or a safety evaluation criterion for a storage tank under foundation settlement conditions based on radial displacement of the tank top, and evaluating the safety of the storage tank; when the evaluation result is qualified, the storage tank is currently in a safe state, and when the evaluation result is unqualified, the storage tank is currently in an unsafe state. The method can comprehensively consider the stress control criterion and the displacement control criterion to make a more accurate evaluation of the safety of the storage tank. The present application also discloses a device for evaluating the safety of a storage tank under foundation settlement conditions.

Description

Technical Field

[0001] The invention belongs to the technical field of storage tank safety, and in particular relates to a storage tank safety evaluation method and device under the condition of foundation settlement. Background Art

[0002] Vertical cylindrical storage tanks are currently the most common form of storage tank structure. They are widely used in the storage of crude oil and other chemical liquids. Large national crude oil reserves are constantly being built, and crude oil storage tanks are becoming larger and larger. As the part that bears the tank structure and the gravity of the stored liquid, the tank foundation plays an important role in the safe operation of the tank. However, with the increase in the number of years of service, the tank foundation will undergo varying degrees of settlement due to the combined effects of factors such as uneven foundation soil texture and uneven load distribution. Foundation settlement can cause deformation of the tank wall of the upper tank, and in severe cases, cause the floating plate to become stuck, affecting the normal production and operation of the tank, and even causing damage to the tank structure, causing leakage accidents. Therefore, it is necessary to conduct regular safety evaluations on tank settlement to promptly discover and eliminate potential safety hazards in the tank and prevent safety accidents.

[0003] At present, several standards and specifications at home and abroad have proposed safety evaluation methods for large storage tanks under foundation settlement conditions, such as SH / T3123-2017 "Petrochemical Steel Storage Tank Foundation Water Preloading Monitoring Regulations", SY / T5921-2017 "Vertical Cylindrical Steel Welded Oil Tank Operation, Maintenance and Repair Specifications", API653-2014 "Storage Tank Inspection, Maintenance, Modification and Reconstruction", etc. These standards and specifications propose evaluation indicators for storage tank foundation settlement and give corresponding allowable values.

[0004] For large storage tanks in production and operation in my country, there will be certain problems when using the above-mentioned assessment standards for settlement safety assessment. SH / T3123-2017 directly divides the settlement forms of storage tanks into plane inclination and non-plane inclination and then gives different assessment standards, but this standard is mainly applicable to the safety assessment of tank foundation settlement during the water filling and preloading stage, and cannot make a reasonable safety assessment of the foundation settlement of tanks during the normal operation stage; API653-2014 is based on whether the data of the tank settlement measurement points can be well fitted by the cosine curve. It gives two assessment standards: the best cosine curve fitting method and the settlement arc length method. However, the best cosine curve fitting method is based on the tank safety assessment method under foundation settlement based on strain control proposed by Marr et al. This method only considers zero-order harmonics. Wave settlement and first-order harmonic settlement do not take into account higher-order harmonic settlement and its impact, which will result in large errors when evaluating storage tanks with higher-order harmonic settlement; Appendix C of SY / T5921-2017 on the assessment of bottom settlement of non-planar inclined storage tanks is a translated version of the best cosine curve fitting method in API653-2014, which also does not take into account higher-order harmonic settlement and does not mention the settlement arc length method. This will result in that if the best cosine curve method cannot be applied during the actual evaluation process, it will be difficult for on-site personnel to continue to find a new evaluation process from the specification for assessment, which will bring certain difficulties to on-site assessment. Summary of the invention

[0005] To solve the above problems, the present invention provides a method and device for evaluating the safety of a storage tank under foundation settlement conditions, which can comprehensively consider the stress control criterion and the displacement control criterion to make a more accurate evaluation of the safety of the storage tank.

[0006] The present invention provides a method for evaluating the safety of a storage tank under the condition of foundation settlement, comprising:

[0007] Obtain discrete settlement data of a storage tank;

[0008] Performing Fourier decomposition on the discrete sedimentation data to convert into Fourier series, and determining an approximate sedimentation curve according to the Fourier series;

[0009] Calculate the magnitude of the correlation coefficient of the approximate sedimentation curve;

[0010] Based on the correlation coefficient, selecting a safety evaluation criterion for a storage tank under a foundation settlement condition based on stress control or a safety evaluation criterion for a storage tank under a foundation settlement condition based on a tank top radial displacement, and performing a safety evaluation on the storage tank;

[0011] When the evaluation result is qualified, the storage tank is currently in a safe state, and when the evaluation result is unqualified, the storage tank is currently in an unsafe state.

[0012] Preferably, in the above-mentioned method for evaluating the safety of a storage tank under the condition of foundation settlement, the step of performing Fourier decomposition on the discrete settlement data and converting the data into Fourier series further comprises:

[0013] The order of the Fourier series is determined using the geometric dimensions of the storage tank and the number of settlement measurement points around the storage tank.

[0014] Preferably, in the above-mentioned method for evaluating the safety of a storage tank under the condition of foundation settlement, when the correlation coefficient is greater than 0.90, the safety evaluation criterion for the storage tank under the condition of foundation settlement based on stress control is selected to perform safety evaluation on the storage tank.

[0015] Preferably, in the above-mentioned method for evaluating the safety of a storage tank under foundation settlement conditions, the selecting the safety evaluation criteria for the storage tank under foundation settlement conditions based on stress control to perform safety evaluation on the storage tank comprises:

[0016] Obtain the ultimate settlement value U for harmonic number n = 2, 3, 4, 5, 6, 7, 8 n , unit is mm;

[0017] Calculate the allowable deviation from the plane settlement difference S;

[0018] Calculate the cumulative damage factor CDF,

[0019]

[0020] Among them, C n is the nth-order harmonic settlement amplitude obtained by Fourier decomposition based on the actual settlement data, in mm; E max is the maximum deviation between the actual settlement data of the tank and the fitting curve, in mm; S is the allowable deviation from the plane settlement difference, in mm;

[0021] The state of the storage tank is judged according to the value of the CDF. When the value of the CDF is less than 1.0, the storage tank is currently in a safe state. When the value of the CDF is greater than or equal to 1.0, the storage tank is currently in an unsafe state.

[0022] Preferably, in the above-mentioned method for evaluating the safety of a storage tank under the condition of foundation settlement, the limit settlement value U n Determine using the following formula:

[0023]

[0024]

[0025]

[0026]

[0027]

[0028]

[0029]

[0030] Among them, U n is the limit settlement value corresponding to the nth order harmonic, in mm; D is the diameter of the storage tank, in m; H is the height of the storage tank, in m;

[0031] The allowable deviation from the plane settlement difference is determined by the following formula:

[0032]

[0033] Wherein, L is the arc length between the measuring points, in m; Y is the yield strength of the tank wall material, in MPa; E is the Young's modulus, in MPa; H is the tank height, in m.

[0034] Preferably, in the above-mentioned method for evaluating the safety of a storage tank under foundation settlement conditions, when the correlation coefficient is less than or equal to 0.90, the tank safety evaluation criterion under foundation settlement conditions based on radial displacement of the tank top is selected to perform safety evaluation on the storage tank.

[0035] Preferably, in the above-mentioned method for evaluating the safety of a storage tank under foundation settlement conditions, the selecting of the storage tank safety evaluation criteria under foundation settlement conditions based on the radial displacement of the tank top to perform safety evaluation on the storage tank comprises:

[0036] Calculate the radial displacement w of the tank top under the action of each order of harmonic settlement n ;

[0037] The radial displacement w of the tank top under the action of each order harmonic settlement n Superposition is performed to obtain the predicted value w of the radial displacement of the tank top under the actual settlement;

[0038] When the predicted value w of the tank top radial displacement is less than 100 mm, the storage tank is currently in a safe state; otherwise, the storage tank is currently in an unsafe state.

[0039] Preferably, in the above-mentioned tank safety evaluation method under foundation settlement, based on the influence of the variable wall thickness of the tank and the angle steel reinforcement structure, the tank top radial displacement w under each order of harmonic settlement is calculated by using the height-to-diameter ratio, diameter-to-thickness ratio and relative stiffness of the wind-resistant ring beam. n .

[0040] Preferably, in the above-mentioned method for evaluating the safety of a storage tank under the condition of foundation settlement, the radial displacement w of the tank top under the action of each order harmonic settlement is calculated. n The predicted value w of the radial displacement of the tank top under the actual settlement is obtained by superposition, including:

[0041] The predicted value w of the radial displacement of the tank top under the actual settlement is determined by the following formula:

[0042]

[0043] Wherein, w is the predicted value of the radial displacement of the tank top under the actual settlement, in mm, and N is the number of foundation settlement monitoring points.

[0044] The present invention provides a storage tank safety evaluation device under the condition of foundation settlement, comprising:

[0045] An acquisition unit, used for acquiring discrete settlement data of a storage tank;

[0046] A conversion unit, used for performing Fourier decomposition on the discrete settlement data, converting the data into Fourier series, and determining an approximate settlement curve according to the Fourier series;

[0047] A calculation unit, used for calculating the magnitude of the correlation coefficient of the approximate sedimentation curve;

[0048] A selection unit, configured to select, based on the correlation coefficient, a safety evaluation criterion for a storage tank under a foundation settlement condition based on stress control or a safety evaluation criterion for a storage tank under a foundation settlement condition based on a radial displacement of a tank top, to perform safety evaluation on the storage tank;

[0049] The safety evaluation unit is used to determine that the storage tank is currently in a safe state when the evaluation result is qualified, and that the storage tank is currently in an unsafe state when the evaluation result is unqualified.

[0050] It can be seen from the above description that the method for evaluating the safety of a storage tank under the above-mentioned foundation settlement provided by the present invention includes obtaining discrete settlement data of the storage tank; performing Fourier decomposition on the discrete settlement data, converting it into Fourier series, and determining an approximate settlement curve according to the Fourier series; calculating the magnitude of the correlation coefficient of the approximate settlement curve; based on the correlation coefficient, selecting a safety evaluation criterion for the storage tank under the foundation settlement based on stress control or a safety evaluation criterion for the storage tank under the foundation settlement based on the radial displacement of the tank top, and evaluating the safety of the storage tank; when the evaluation result is qualified, the storage tank is currently in a safe state, and when the evaluation result is unqualified, the storage tank is currently in an unsafe state. It can be seen that this method can comprehensively consider the stress control criterion and the displacement control criterion, and adopt the corresponding criterion for evaluation under different circumstances, so as to make a more accurate evaluation of the safety of the storage tank. The device for evaluating the safety of a storage tank under the above-mentioned foundation settlement provided by the present invention has the same advantages as the above-mentioned method. BRIEF DESCRIPTION OF THE DRAWINGS

[0051] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0052] Figure 1 A schematic diagram of an embodiment of a method for evaluating the safety of a storage tank under the condition of foundation settlement provided by the present invention;

[0053] Figure 2 It is a schematic diagram of another specific embodiment of a method for evaluating the safety of a storage tank under the condition of foundation settlement;

[0054] Figure 3 A schematic diagram of an embodiment of a storage tank safety evaluation device under foundation settlement conditions provided by the present invention. DETAILED DESCRIPTION

[0055] The core of the present invention is to provide a method and device for evaluating the safety of a storage tank under the condition of foundation settlement, which can comprehensively consider the stress control criterion and the displacement control criterion to make a more accurate evaluation of the safety of the storage tank.

[0056] 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.

[0057] The implementation example of the method for evaluating the safety of a storage tank under the condition of foundation settlement provided by the present invention is as follows: Figure 1 As shown, Figure 1 A schematic diagram of an embodiment of a method for evaluating the safety of a storage tank under foundation settlement provided by the present invention, the method may include the following steps:

[0058] S1: Obtain discrete settlement data of the storage tank;

[0059] S2: Perform Fourier decomposition on the discrete settlement data, convert it into Fourier series, and determine the approximate settlement curve according to the Fourier series;

[0060] The parameters in the formula can be obtained using the settlement data. After obtaining the complete expression, its function curve is the approximate settlement curve. In this way, the discrete data can be functionalized, and the settlement can be decomposed into the form of series so that different orders of settlement can be considered separately, which is convenient for the analysis and superposition of different orders of settlement.

[0061] S3: Calculate the correlation coefficient R of the approximate sedimentation curve 2 size;

[0062] S4: Based on the correlation coefficient R 2 , select the tank safety evaluation criteria under the condition of foundation settlement based on stress control or the tank safety evaluation criteria under the condition of foundation settlement based on radial displacement of tank top to conduct safety evaluation on the tank;

[0063] S5: When the evaluation result is qualified, the tank is currently in a safe state, and the safety of the tank can be ensured through regular inspections. When the evaluation result is unqualified, the tank is currently in an unsafe state, and emergency repair measures are required immediately.

[0064] Specifically, the settlement of the tank can be decomposed into a multi-order harmonic superposition method by Fourier. When further studying the impact of settlement on the tank structure, each order of harmonic settlement can be applied to the tank model. First, the structural response of the tank under each order of harmonic settlement is summarized, and then linear superposition is performed to obtain the change values ​​of the displacement, performance and other structural properties of the tank under overall settlement. The Fourier series formula is:

[0065]

[0066] in, z is the overall vertical settlement of the tank, mm; z avg is the arithmetic mean of the settlement data, in mm; C n is the amplitude of each order of harmonic sedimentation, in mm; k is the upper limit of the order of applied harmonic sedimentation; θ is the angular coordinate; φ n is the phase angle of each order harmonic sink applied.

[0067] The selection method of the upper limit value k of the harmonic order is as follows: Taking the 100,000 cubic meter large storage tank commonly used in my country as an example, according to the provisions of SY / T6620-2014, at least 26 equally spaced measuring points should be arranged around it when evaluating its foundation settlement. The upper limit value k of the harmonic wave number obtained by Fourier decomposition of its actual settlement data is up to 8. For storage tanks of other capacities, the amplitude and corresponding phase angle of the 0-8 order harmonic settlement can be obtained by Fourier decomposition of its actual settlement data. The remaining parameters can be calculated by the following formulas:

[0068]

[0069]

[0070]

[0071]

[0072]

[0073] The above solution process can be compiled into a Matlab program. By inputting the settlement data of the observation point, the corresponding Fourier series coefficient value can be obtained quickly and effectively. The relevant code is as follows:

[0074]

[0075]

[0076] R 2 The calculation formula is as follows:

[0077]

[0078] Among them, S yy =∑(S o -S oa ) 2 ; S o is the settlement observation value, in mm; S oa is the mean of the settlement observations SSE = ∑(S o -S c ) 2 , unit is mm; S c is the cosine curve value, in mm.

[0079] It can be seen from the above description that in the embodiment of the method for evaluating the safety of a storage tank under the above-mentioned foundation settlement provided by the present invention, the method includes obtaining discrete settlement data of the storage tank; performing Fourier decomposition on the discrete settlement data, converting it into Fourier series, and determining an approximate settlement curve according to the Fourier series; calculating the size of the correlation coefficient of the approximate settlement curve; based on the correlation coefficient, selecting a safety evaluation criterion for the storage tank under the foundation settlement based on stress control or a safety evaluation criterion for the storage tank under the foundation settlement based on the radial displacement of the tank top, and performing a safety evaluation on the storage tank; when the evaluation result is qualified, the storage tank is currently in a safe state, and when the evaluation result is unqualified, the storage tank is currently in an unsafe state. It can be seen that the method can comprehensively consider the stress control criterion and the displacement control criterion, and adopt the corresponding criteria for evaluation under different circumstances, so as to make a more accurate evaluation of the safety of the storage tank.

[0080] In a specific embodiment of the above-mentioned method for evaluating the safety of a storage tank under the condition of foundation settlement, Fourier decomposition of discrete settlement data and conversion into Fourier series may also include:

[0081] The order of the Fourier series is determined by the geometric dimensions of the tank and the number of settlement measurement points around the tank. Specifically, the order can be set to N / 3, where N is the number of settlement measurement points. In other words, the order is determined by the number of settlement measurement points. Generally, the larger the geometric dimensions of the tank, the more settlement measurement points there are, and the order increases accordingly.

[0082] In another specific embodiment of the above-mentioned method for evaluating the safety of a storage tank under the condition of foundation settlement, refer to Figure 2 , Figure 2 The schematic diagram of another specific embodiment of the method for evaluating the safety of a storage tank under foundation settlement is shown in FIG. 1 . When the correlation coefficient is greater than 0.90, the safety evaluation criteria for the storage tank under foundation settlement based on stress control are selected to evaluate the safety of the storage tank. In this case, the safety evaluation criteria for the storage tank under foundation settlement based on stress control are selected to evaluate the safety of the storage tank, which may include:

[0083] Obtain the ultimate settlement value U for harmonic number n = 2, 3, 4, 5, 6, 7, 8 n , the unit is mm, the harmonic number here can be selected according to actual needs;

[0084] Use the formula to calculate the allowable deviation from the plane settlement difference S;

[0085] Calculate the cumulative damage factor CDF,

[0086]

[0087] Among them, C n is the nth-order harmonic settlement amplitude obtained by Fourier decomposition based on the actual settlement data, in mm; Emax is the maximum deviation between the actual settlement data of the tank and the fitting curve, in mm; S is the allowable deviation from the plane settlement difference, in mm;

[0088] The state of the tank is judged according to the CDF value. When the CDF value is less than 1.0, the tank is currently in a safe state. When the CDF value is greater than or equal to 1.0, the tank is currently in an unsafe state, indicating that the tank foundation should be re-leveled.

[0089] It should also be noted that the harmonic order and tank geometry (D2 2 / H) has an impact on the ultimate settlement value of the tank. As the harmonic order increases, the ultimate settlement value of the tank gradually decreases. The same tank has a stronger ability to resist buckling under low-order harmonic settlement, but a weaker ability to resist buckling under high-order harmonic settlement. As the harmonic order increases, the decreasing trend of the ultimate settlement value gradually becomes flat. Under the same order harmonic settlement, as the geometric size of the tank increases, the ultimate settlement value also gradually increases. The geometric size of the tank (D2 2 / H) is larger, the stronger its ability to resist buckling under harmonic settlement is, and the less likely it is to buckle. The relationship between the two is roughly a power function relationship. Therefore, in the above embodiment, the limit settlement value U n It can be determined using the following formula:

[0090]

[0091]

[0092]

[0093]

[0094]

[0095]

[0096]

[0097] Among them, U n is the limit settlement value corresponding to the nth order harmonic, in mm; D is the diameter of the tank, in m; H is the height of the tank, in m;

[0098] Moreover, the above-mentioned allowable deviation from the plane settlement difference S can be determined using the following formula:

[0099]

[0100] Wherein, L is the arc length between the measuring points, in m; Y is the yield strength of the tank wall material, in MPa; E is the Young's modulus, in MPa; H is the tank height, in m.

[0101] In another specific embodiment of the above-mentioned method for evaluating the safety of a storage tank under the condition of foundation settlement, continue to refer to Figure 2 ,When the correlation coefficient is less than or equal to 0.90, the tank safety evaluation criteria based on the foundation settlement under the radial displacement of the tank top is selected to evaluate the safety of the tank.

[0102] Furthermore, the safety evaluation criteria for storage tanks based on the foundation settlement under the radial displacement of the tank top may include:

[0103] Calculate the radial displacement w of the tank top under the action of each order of harmonic settlement n ;

[0104] The radial displacement w of the tank top under the action of each order harmonic settlement n Superposition is performed to obtain the predicted value w of the radial displacement of the tank top under the actual settlement;

[0105] When the predicted value w of the tank top radial displacement is less than 100 mm, the tank is currently in a safe state, otherwise the tank is currently in an unsafe state.

[0106] It should be noted that according to the provisions of API650, the radial displacement of the tank wall should be less than 100mm, and the maximum radial displacement of the tank wall occurs at the top of the tank. Therefore, the predicted radial displacement of the top of a large storage tank under foundation settlement conditions is less than 100mm to ensure the safety of the tank. In order to ensure the safety of tank operation, various countries have formulated control standards for tank settlement based on a large number of numerical simulations and field investigations, such as API653-2014 in the United States, SY / T6620-2014, SH / T3123-2017 and SY / T5921-2017 in my country, etc. For common 100,000 cubic large storage tanks, the control indicators specified by different standards are shown in Table 1.

[0107] Table 1 Control indicators of 100,000 cubic meters storage tanks in different domestic and foreign standards

[0108]

[0109] In a preferred embodiment of the above-mentioned tank safety evaluation method under foundation settlement, based on the influence of the variable wall thickness of the tank and the angle steel reinforcement structure, the tank's height-to-diameter ratio, diameter-to-thickness ratio and relative stiffness of the wind-resistant ring beam are used to calculate the radial displacement w of the tank top under the action of each order of harmonic settlement. n ,It can be seen that this takes more factors into consideration, so it is closer to actual engineering and has better accuracy.

[0110] It should be noted that many standards and specifications have proposed their own safety evaluation methods for foundation settlement storage tanks, but these methods are not unified and do not include parameters such as the height-to-diameter ratio, diameter-to-thickness ratio, and relative stiffness of the wind-resistant ring beam. Many studies have shown that parameters such as the height-to-diameter ratio, diameter-to-thickness ratio, and relative stiffness of the wind-resistant ring beam of the storage tank will have a significant impact on the structural response of the storage tank under foundation settlement conditions. Therefore, when conducting safety evaluations on large storage tanks under foundation settlement conditions, the height-to-diameter ratio, diameter-to-thickness ratio, and relative stiffness of the wind-resistant ring beam of the storage tank should be taken into account. After fully considering the above-mentioned influencing factors, the proposed maximum dimensionless radial displacement fitting formula for the tank top of a 10w cubic storage tank under foundation settlement conditions is as follows:

[0111]

[0112] Among them, w n is the radial displacement of the tank top under the action of each order of harmonic settlement, in mm; n is the harmonic order (the upper limit of the order depends on the number of foundation settlement monitoring points); H / R is the height-to-diameter ratio of the tank; R / t is the diameter-to-thickness ratio of the tank; I ratio is the relative stiffness of the wind-resistant ring beam of the storage tank; M is the number of layers of the variable wall thickness storage tank; △t max It is the difference between the maximum wall thickness and the minimum wall thickness, in mm; △t avemax is the maximum value of the difference between the wall thickness of each layer and the average wall thickness, in mm; C n is the amplitude of the nth-order harmonic sedimentation, in mm.

[0113] Among them, the calculation method of the relative stiffness of the wind-resistant ring beam is as follows: The top of the tank wall of a large external floating roof storage tank is usually provided with a cladding angle steel, which is connected to the tank wall by welding. In the membrane theory solution and the modified Donnell formula solution, the part of the tank top that extends radially outward along the tank is called the Primary Wind Girder, that is, the main wind-resistant ring beam. The relative stiffness of the wind-resistant ring beam involved in the calculation formula is the ratio of the bending stiffness of the main wind-resistant ring beam to the bending stiffness of the tank wall. Therefore, for large domestic storage tanks, the main wind-resistant ring beam corresponds to the part of the tank top cladding angle steel that extends radially outward along the tank. The relative stiffness of the wind-resistant ring beam is the ratio of the bending stiffness of the extended part of the tank top cladding angle steel to the bending stiffness of the tank wall. This should be distinguished from the wind-resistant ring set up for domestic storage tanks, because for domestic storage tanks, the first wind-resistant ring is set below 1m from the tank top, not on the tank top, so the relative stiffness of the wind-resistant ring beam used in the calculation does not involve the bending stiffness of the wind-resistant ring.

[0114] Next, the radial displacement w of the tank top under the action of each order of harmonic settlement is calculated. n By superimposing, the predicted value w of the tank top radial displacement under the actual settlement can be obtained, which can include:

[0115] The predicted value w of the tank top radial displacement under actual settlement is determined using the following formula:

[0116]

[0117] Wherein, w is the predicted value of the radial displacement of the tank top under the actual settlement, in mm, and N is the number of foundation settlement monitoring points.

[0118] In summary, the tank safety assessment method under the above-mentioned foundation settlement condition provided by the present invention has the following advantages:

[0119] First, the radial displacement of the tank is more closely related to the amplitude of the higher-order harmonics. When the amplitude of the higher-order harmonics is higher, the radial displacement of the tank under settlement will increase significantly. When the settlement of the tank can present an obvious rigid body inclined plane, its maximum radial displacement will be smaller, and at this time the stress change of the tank wall is more obvious. Therefore, the classification and judgment of the tank situation by selecting different safety evaluation criteria according to the approximate settlement curve proposed in the present invention is more accurate and reasonable than the existing specifications.

[0120] Second, this method fully considers the influence of higher-order harmonic settlement on the basis of zero-order harmonic settlement and first-order harmonic settlement. Taking into account the large difference between the common sizes of storage tanks abroad and the sizes of large storage tanks in my country, combined with the actual situation of storage tanks in my country, more stringent requirements are put forward for the deviation from the plane settlement limit, which makes the safety assessment of storage tanks under uneven foundation settlement more accurate.

[0121] Third, this method obtains the predicted value of the tank top radial displacement according to the prediction formula of the tank top radial displacement under the action of harmonic settlement, and compares it with the critical radial displacement for safety evaluation. On the basis of similar methods, the influence of the variable wall thickness of the tank and the strengthening structure such as the edge angle steel are considered, which is closer to the actual project.

[0122] An implementation example of a storage tank safety evaluation device under foundation settlement provided by the present invention is as follows: Figure 3 As shown, Figure 3 A schematic diagram of an embodiment of a storage tank safety evaluation device under foundation settlement provided by the present invention, the device may include:

[0123] An acquisition unit 201 is used to acquire discrete settlement data of a storage tank;

[0124] A conversion unit 202 is used to perform Fourier decomposition on the discrete settlement data, convert it into a Fourier series, and determine an approximate settlement curve according to the Fourier series;

[0125] A calculation unit 203 is used to calculate the magnitude of the correlation coefficient of the approximate sedimentation curve;

[0126] A selection unit 204 is used to select, based on the correlation coefficient, a safety evaluation criterion for a storage tank under a foundation settlement condition based on stress control or a safety evaluation criterion for a storage tank under a foundation settlement condition based on a radial displacement of a tank top, to perform safety evaluation on the storage tank;

[0127] The safety evaluation unit 205 is used to determine that the storage tank is currently in a safe state when the evaluation result is qualified, and that the storage tank is currently in an unsafe state when the evaluation result is unqualified.

[0128] The above-mentioned storage tank safety evaluation device under the condition of foundation settlement can comprehensively consider the stress control criterion and the displacement control criterion to make a more accurate evaluation of the storage tank safety.

[0129] The following example uses six 100,000-cubic-meter storage tanks in a certain storage tank area that have settled to illustrate the above scheme. The settlement data of the storage tanks are obtained through actual measurements. The six storage tanks have the same specifications, with a tank diameter of 80m and a tank height of 21.7m. The parameters of the plate steel used in each part of the tank are shown in Table 2. The elastic modulus of the plate steel used in the tank is 2.06×10 11 Pa, Poisson's ratio is 0.3. Angle steel with a size of 100*12mm is provided on the top of the tank wall. Each tank has different degrees of uneven settlement. The above method proposed by the present invention is used for safety evaluation and compared with the evaluation results of different domestic and foreign standards.

[0130] Table 2 Parameters of tank plate steel

[0131]

[0132] First example:

[0133] There are 26 measuring points at the bottom of the tank, and the settlement of each measuring point of the tank is [-87.9mm, -66.7mm, -73.6mm, -46.8mm, -53.8mm, -44.2mm, -30.1mm, -20.5mm, -0.1mm, -0.3mm, 5.1mm, 0.3mm, 0.5mm, 1.5mm, 0mm, 24.1mm, 11.5mm, 8.9mm, 19.3mm, 15.0mm, 18.6mm, 11.1mm, 0mm, -10.2mm, -45mm, -62.4mm]. The arc length between adjacent points is 9.66m, the maximum settlement difference between adjacent points is 34.8mm, and the maximum settlement difference between two points in the diameter direction is 99.7mm. Safety verification is carried out based on different standards and the safety evaluation method proposed in the present invention, and the results are shown in Table 3.

[0134] Table 3. Safety evaluation results of storage tank 1

[0135] Evaluation Method SH / T3123-2017 SY / T5921-2017 API653-2014 The present invention result Failure Failure Failure Failure

[0136] Second example

[0137] There are 26 measuring points at the bottom of tank 2, and the settlement of each measuring point of the tank is [-11.5mm, -15mm, -21mm, -20.3mm, -21.6mm, -22.5mm, -16.8mm, -15.3mm, -12.3mm, -11.3mm, -11.4mm, -12.5mm, -12.6mm, -13.1mm, -16mm, -12.6mm, -11.8mm, -13.3mm, -14.1mm, -11.2mm, -11.2mm, -9.5mm, -16mm, -10.2mm, -9.2mm, -8.3mm]. The arc length between adjacent points is 9.66m, the maximum settlement difference between adjacent points is 6.5mm, and the maximum settlement difference between two points in the diameter direction is 8.5mm. Safety verification is performed based on different standards and the safety evaluation method proposed in the present invention, and the results are shown in Table 4.

[0138] Table 4 Safety evaluation results of storage tank 2

[0139] Evaluation Method SH / T3123-2017 SY / T5921-2017 API653-2014 The present invention result qualified qualified qualified qualified

[0140] The third example

[0141] There are 26 measuring points at the bottom of the tank three, and the settlement of each measuring point of the tank is [-38.4mm, -30.5mm, -15.2mm, -1mm, 2.2mm, 7.9mm, 1.8mm, -3mm, -6.6mm, 4.3mm, 13.2mm, -15.6mm, -31.4mm, -10.1mm, -15.3mm, -20.3mm, -38mm, -30.1mm, -25.9mm, -24.5mm, -15mm, -21.7mm, -19mm, -32.2mm, -25.1mm, -30.2mm]. The arc length between adjacent points is 9.66m, the maximum settlement difference between adjacent points is 21.3mm, and the maximum settlement difference between two points in the diameter direction is 37mm. Safety verification is carried out based on different standards and the safety evaluation method proposed in the present invention, and the results are shown in Table 5.

[0142] Table 5. Results of the three safety evaluations of storage tanks

[0143] Evaluation Method SH / T3123-2017 SY / T5921-2017 API653-2014 The present invention result qualified Failure Failure Failure

[0144] Fourth example

[0145] There are 26 measuring points at the bottom of the tank, and the settlement of each measuring point of the tank is [-12.4mm, -13.4mm, -0.1mm, -5.3mm, -16.7mm, -16.1mm, -10.4mm, -10.7mm, -10mm, -9.5mm, -10.3mm, -6.5mm, -8mm, -11.3mm, -10.4mm, -12.1mm, -10.8mm, -11.9mm, -9.3mm, -12.2mm, -9mm, -6.3mm, -10.8mm, -14.2mm, -6.5mm, -0.3mm]. The arc length between adjacent points is 9.66m, the maximum settlement difference between adjacent points is 13.3mm, and the maximum settlement difference between two points in the diameter direction is 12mm. Safety verification is performed based on different standards and the safety evaluation method proposed in the present invention, and the results are shown in Table 6.

[0146] Table 6 Safety evaluation results of storage tank 4

[0147]

[0148]

[0149] The fifth example

[0150] There are 26 measuring points at the bottom of tank five, and the settlement of each measuring point of the tank is [-17.7mm, -10.2mm, -24.3mm, -26.5mm, -11.3mm, -14.6mm, -10.6mm, -10.5mm, -0.6mm, -4.9mm, -11.6mm, -5.7mm, -12.1mm, -7.5mm, -10.8mm, -32.2mm, -30.8mm, -10.4mm, -20.3mm, -13.4mm, -10.1mm, -20.1mm, -33.3mm, -24.2mm, -12.9mm, -2.1mm]. The arc length between adjacent points is 9.66m, the maximum settlement difference between adjacent points is 21.4mm, and the maximum settlement difference between two points in the diameter direction is 28.4mm. Safety verification is performed based on different standards and the safety evaluation method proposed in the present invention, and the results are shown in Table 7.

[0151] Table 7 Safety evaluation results of storage tank V

[0152] Evaluation Method SH / T3123-2017 SY / T5921-2017 API653-2014 The present invention result qualified qualified qualified qualified

[0153] The sixth example

[0154] There are 26 measuring points at the bottom of tank six, and the settlement of each measuring point of the tank is [-19.0mm, -25.2mm, -30.4mm, -20.5mm, -34.4mm, -4.6mm, -11.2mm, -22.9mm, -38.9mm, -1.9mm, -34.8mm, -7.3mm, 4.5mm, -4.6mm, -24.0mm, -17.0mm, -27.8mm, -28.2mm, -10.3mm, -15.0mm, -17.1mm, -14.7mm, -22.9mm, -1.8mm, -16.9mm, -32.7mm]. The arc length between adjacent points is 9.66m, the maximum settlement difference between adjacent points is 37mm, and the maximum settlement difference between two points in the diameter direction is 37.2mm. Safety verification is performed based on different standards and the safety evaluation method proposed in the present invention, and the results are shown in Table 8.

[0155] Table 8 Results of the six safety evaluations of storage tanks

[0156] Evaluation Method SH / T3123-2017 SY / T5921-2017 API653-2014 The present invention result Failure Failure Failure Failure

[0157] It can be seen from the above six examples that it is more accurate and reasonable to select different safety evaluation criteria according to the approximate settlement curve to judge the situation of the storage tank under foundation settlement. By reasonably selecting the stress control and displacement control criteria and considering the influence of the variable wall thickness of the storage tank and the strengthening structure such as the edging angle steel, it is closer to the actual project. The present invention solves the shortcomings of the current domestic safety evaluation method for storage tank foundation settlement, has good accuracy, and can provide a reference for the safety evaluation of large storage tanks under foundation settlement conditions.

[0158] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for evaluating the safety of storage tanks under foundation settlement conditions. It is characterized in that include: Obtain discrete settlement data of storage tanks; Performing Fourier decomposition on the discrete sedimentation data to convert into Fourier series, and determining an approximate sedimentation curve according to the Fourier series; Calculate the magnitude of the correlation coefficient of the approximate sedimentation curve; Based on the correlation coefficient, selecting a safety evaluation criterion for a storage tank under a foundation settlement condition based on stress control or a safety evaluation criterion for a storage tank under a foundation settlement condition based on a tank top radial displacement, and performing a safety evaluation on the storage tank; When the evaluation result is qualified, the storage tank is currently in a safe state; when the evaluation result is unqualified, the storage tank is currently in an unsafe state; When the correlation coefficient is greater than 0.90, the safety evaluation criteria for storage tanks under the condition of foundation settlement based on stress control are selected to conduct safety evaluation on the storage tanks; The selecting of the tank safety evaluation criteria under the foundation settlement condition based on stress control to perform safety evaluation on the tank comprises: Obtain the ultimate settlement value U for harmonic number n=2, 3, 4, 5, 6, 7, 8 n , unit is mm; Calculate the allowable deviation from the plane settlement difference S; Calculate the cumulative damage factor CDF, ， Among them, C n is the nth-order harmonic settlement amplitude obtained by Fourier decomposition based on the actual settlement data, in mm; E max is the maximum deviation between the actual settlement data of the tank and the fitting curve, in mm; S is the allowable deviation from the plane settlement difference, in mm; The state of the storage tank is judged according to the value of the CDF. When the value of the CDF is less than 1.0, the storage tank is currently in a safe state. When the value of the CDF is greater than or equal to 1.0, the storage tank is currently in an unsafe state. When the correlation coefficient is less than or equal to 0.90, the tank safety evaluation criterion based on the foundation settlement condition of the tank top radial displacement is selected to perform safety evaluation on the tank; The selecting of the tank safety evaluation criteria based on the foundation settlement under the tank top radial displacement to perform safety evaluation on the tank comprises: Calculate the radial displacement w of the tank top under the action of each order of harmonic settlement n ; The radial displacement w of the tank top under the action of each order harmonic settlement n Superposition is performed to obtain the predicted value w of the radial displacement of the tank top under the actual settlement; When the predicted value w of the tank top radial displacement is less than 100 mm, the storage tank is currently in a safe state; otherwise, the storage tank is currently in an unsafe state.

2. The method for evaluating the safety of a storage tank under ground settlement conditions according to claim 1, It is characterized in that The performing Fourier decomposition on the discrete sedimentation data and converting the data into Fourier series further comprises: The order of the Fourier series is determined using the geometric dimensions of the storage tank and the number of settlement measurement points around the storage tank.

3. The method for evaluating the safety of storage tanks under foundation settlement according to claim 1, It is characterized in that The limit settlement value U n Determine using the following formula: ， ， ， ， ， ， ， Among them, U n is the limit settlement value corresponding to the nth order harmonic, in mm; D is the diameter of the storage tank, in m; H is the height of the storage tank, in m; The allowable deviation from the plane settlement difference is determined by the following formula: ， Wherein, L is the arc length between the measuring points, in m; Y is the yield strength of the tank wall material, in MPa; E is the Young's modulus, in MPa; H is the tank height, in m.

4. The method for evaluating the safety of a storage tank under foundation settlement according to claim 1, It is characterized in that Based on the influence of the variable wall thickness and the angle steel reinforcement structure of the tank, the tank top radial displacement w under the action of each order of harmonic settlement is calculated by using the height-to-diameter ratio, diameter-to-thickness ratio and relative stiffness of the wind-resistant ring beam. n .

5. The method for evaluating the safety of storage tanks under foundation settlement according to claim 1, It is characterized in that The radial displacement w of the tank top under the action of each order harmonic sedimentation n The predicted value w of the radial displacement of the tank top under the actual settlement is obtained by superposition, including: The predicted value w of the radial displacement of the tank top under the actual settlement is determined by the following formula: ， in, w is the predicted value of radial displacement of the tank top under actual settlement, in mm. N is the number of foundation settlement monitoring points.

6. A tank safety assessment device under foundation settlement conditions, It is characterized in that include: An acquisition unit, used for acquiring discrete settlement data of a storage tank; A conversion unit, used for performing Fourier decomposition on the discrete settlement data, converting the data into Fourier series, and determining an approximate settlement curve according to the Fourier series; A calculation unit, used for calculating the magnitude of the correlation coefficient of the approximate sedimentation curve; A selection unit, configured to select, based on the correlation coefficient, a safety evaluation criterion for a storage tank under a foundation settlement condition based on stress control or a safety evaluation criterion for a storage tank under a foundation settlement condition based on a radial displacement of a tank top, and perform safety evaluation on the storage tank; A safety evaluation unit, used for determining that the storage tank is currently in a safe state when the evaluation result is qualified, and that the storage tank is currently in an unsafe state when the evaluation result is unqualified; The selection unit is used for selecting the tank safety evaluation criterion under the condition of foundation settlement based on stress control to perform safety evaluation on the tank when the correlation coefficient is greater than 0.90, wherein the selecting the tank safety evaluation criterion under the condition of foundation settlement based on stress control to perform safety evaluation on the tank comprises: Obtain the ultimate settlement value U for harmonic number n=2, 3, 4, 5, 6, 7, 8 n , unit is mm; Calculate the allowable deviation from the plane settlement difference S; Calculate the cumulative damage factor CDF, ， Among them, C n is the nth-order harmonic settlement amplitude obtained by Fourier decomposition based on the actual settlement data, in mm; E max is the maximum deviation between the actual settlement data of the tank and the fitting curve, in mm; S is the allowable deviation from the plane settlement difference, in mm; The state of the storage tank is judged according to the value of the CDF. When the value of the CDF is less than 1.0, the storage tank is currently in a safe state. When the value of the CDF is greater than or equal to 1.0, the storage tank is currently in an unsafe state. When the correlation coefficient is less than or equal to 0.90, the tank safety evaluation criterion based on the foundation settlement condition of the tank top radial displacement is selected to perform safety evaluation on the tank; The selecting of the tank safety evaluation criteria based on the foundation settlement under the tank top radial displacement to perform safety evaluation on the tank comprises: Calculate the radial displacement w of the tank top under the action of each order of harmonic settlement n ; The radial displacement w of the tank top under the action of each order harmonic settlement n Superposition is performed to obtain the predicted value w of the radial displacement of the tank top under the actual settlement; When the predicted value w of the tank top radial displacement is less than 100 mm, the storage tank is currently in a safe state; otherwise, the storage tank is currently in an unsafe state.

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