A method and system for stress analysis of a storage tank based on temperature working conditions

Abstract

The application discloses a kind of based on temperature working condition's storage tank stress analysis method and system, it is related to storage tank structure analysis and simulation technical field.The method includes: the three-dimensional finite element model containing pile foundation and bearing platform is constructed;According to liquid level height and gas-liquid phase transition interface, linearly decreasing non-uniform temperature field with height is generated;According to meteorological extreme low temperature record, segmented environmental temperature load is applied on the outer surface of storage tank;The temperature stress distribution nephogram of pile foundation is obtained by thermal-mechanical coupling calculation;From the axial internal force and bending moment value of pile section are parsed and output to checking module.The application solves the technical problems of traditional method in temperature field modeling distortion, coupling mechanism is not perfect and internal force extraction is not accurate, significantly improves the accuracy and engineering applicability of stress analysis of storage tank pile foundation under complex temperature working condition.

Description

Technical Field

[0001] This invention relates to tank structure analysis and simulation technology, and in particular to a method and system for stress analysis of tanks based on temperature conditions. Background Technology

[0002] In the storage of cryogenic media such as liquefied natural gas (LNG), stress response analysis of tank structures, especially pile foundation systems, under complex temperature conditions has always been a key challenge in engineering design and safety assessment. Traditional stress analysis methods are mostly based on simplification assumptions, such as treating the internal temperature field of the tank as a uniform distribution or ignoring the temperature abrupt changes at the gas-liquid phase transition interface. At the same time, external environmental temperature loads are often treated with single values ​​or coarse segmentation, failing to truly reflect the liquid level-related temperature gradient and the temperature difference in the height direction caused by meteorological cryogenic records that exist in actual working conditions.

[0003] Furthermore, existing technologies often simplify the thermo-mechanical coupling process to a steady-state analysis, neglecting the dynamic impact of transient temperature changes on the structural response, leading to significant deviations in pile foundation stress prediction. Especially in extreme low-temperature environments, tank pile foundations are prone to localized stress concentrations. If the internal force distribution cannot be accurately assessed, the reliability of pile foundation bearing capacity verification will be directly affected, thus threatening the overall structural safety. Therefore, there is an urgent need for an analytical method that can efficiently and accurately simulate the stress distribution of tank pile foundations under complex temperature fields, to overcome the shortcomings of traditional methods in terms of the realism of temperature field modeling, the comprehensiveness of coupling analysis, and the engineering applicability of the results. Summary of the Invention

[0004] In order to overcome the above-mentioned defects of the prior art, embodiments of the present invention provide a storage tank stress analysis method based on temperature conditions to solve the problems mentioned in the background art.

[0005] To achieve the above objectives, the present invention provides a method for stress analysis of storage tanks based on temperature conditions, comprising:

[0006] Construct a three-dimensional finite element model including pile foundations and tank caps;

[0007] Based on the liquid level height and gas-liquid phase transition interface on the inner wall of the storage tank, the boundary of the low-temperature medium action domain is defined, and a non-uniform temperature field that decreases linearly with the liquid level height is generated.

[0008] An ambient temperature load, segmented according to height, is applied to the outer surface of the storage tank in the three-dimensional finite element model. The ambient temperature load is determined based on local extreme low temperature records.

[0009] Based on the non-uniform temperature field and the ambient temperature load, a temperature stress distribution cloud map of the pile foundation is generated through thermo-mechanical coupling calculation.

[0010] The axial internal force and bending moment values ​​of the pile section are analyzed from the temperature stress distribution cloud map and output to the pile foundation bearing capacity verification module.

[0011] To address the aforementioned problems, the present invention also provides a storage tank stress analysis system based on temperature conditions, the system comprising:

[0012] The finite element model building module is used to build a three-dimensional finite element model that includes pile foundations and tank caps;

[0013] The inner wall temperature field generation module is used to divide the boundary of the low-temperature medium action area based on the liquid level height and gas-liquid phase change interface on the inner wall of the storage tank, and generate a non-uniform temperature field that decreases linearly with the liquid level height.

[0014] The external surface temperature modeling module is used to apply an environmental temperature load segmented in the height direction to the outer surface of the tank in the three-dimensional finite element model. The environmental temperature load is determined based on local extreme low temperature meteorological records.

[0015] The thermo-mechanical coupling calculation module is used to generate a temperature stress distribution cloud map of the pile foundation based on the non-uniform temperature field and the ambient temperature load through thermo-mechanical coupling calculation;

[0016] The stress analysis module is used to analyze the axial internal force and bending moment values ​​of the pile section from the temperature stress distribution cloud map and output them to the pile foundation bearing capacity verification module.

[0017] This invention constructs a three-dimensional finite element model including pile foundations and tank caps, and generates a non-uniform temperature field that decreases linearly with height based on liquid level and gas-liquid phase change interface. This effectively improves the realism and accuracy of the internal temperature field modeling of the tank. By combining local extreme low temperature meteorological records, segmented environmental temperature loads are applied to the outer surface of the tank, and dual gradient coupling of internal and external temperature fields is achieved, significantly enhancing the engineering applicability and physical rationality of the temperature boundary conditions. Furthermore, the temperature field is transformed into a pile foundation temperature stress distribution cloud map through thermo-mechanical coupling calculation. The axial internal force and bending moment values ​​of the pile section are analyzed by integration, allowing the stress analysis results to be directly used for pile foundation bearing capacity verification. This overcomes the technical limitations of traditional methods in terms of temperature field simplification, lack of coupling mechanism, and incomplete internal force extraction. Therefore, the method proposed in this invention systematically solves the problem of stress simulation distortion caused by the combined effects of liquid level changes, phase change interface, and environmental temperature gradient in LNG storage tanks under low temperature conditions. By achieving refined processing of the entire process from temperature field construction and coupling analysis to internal force extraction, the accuracy and reliability of stress analysis are improved. Attached Figure Description

[0018] Figure 1 A schematic flowchart of a temperature-based stress analysis method for storage tanks provided in an embodiment of the present invention;

[0019] Figure 2 A functional block diagram of a temperature-based tank stress analysis system provided in an embodiment of the present invention;

[0020] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0021] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0022] This application provides a method for stress analysis of storage tanks based on temperature conditions. The execution entity of the temperature-condition-based storage tank stress analysis method includes, but is not limited to, at least one of the following electronic devices that can be configured to execute the method provided in this application: a server, a terminal, etc. In other words, the temperature-condition-based storage tank stress analysis method can be executed by software or hardware installed on a terminal device or a server device. The server includes, but is not limited to, a single server, a server cluster, a cloud server, or a cloud server cluster. The server can be an independent server or a cloud server that provides basic cloud computing services such as cloud services, cloud databases, cloud computing, cloud functions, cloud storage, network services, cloud communication, middleware services, domain name services, security services, content delivery networks, and big data and artificial intelligence platforms.

[0023] Reference Figure 1 The diagram shown is a schematic flowchart of a temperature-condition-based stress analysis method for storage tanks provided in an embodiment of the present invention. In this embodiment, the temperature-condition-based stress analysis method for storage tanks includes:

[0024] S1. Construct a three-dimensional finite element model including the pile foundation and the tank cap.

[0025] In this embodiment of the application, the three-dimensional finite element model is constructed by computer-aided engineering software and is a digital model that reflects the geometric shape and mechanical properties of the storage tank, pile foundation and pile cap; the pile foundation refers to the column-shaped foundation structure buried underground to bear the load of the storage tank and the internal medium; the storage tank pile cap is a reinforced concrete structure that connects the bottom of the storage tank and the top of the pile foundation and plays the role of distributing the load.

[0026] In some embodiments, constructing a three-dimensional finite element model including pile foundations and tank caps includes:

[0027] Extract the pile spacing and geometric dimensions of the tank foundation from the tank design drawings to generate a geometric dataset of the tank.

[0028] Based on the geometric dataset, second-order tetrahedral elements are used to divide the pile foundation and the tank pier into meshes to generate an initial mesh model;

[0029] Fixed constraint boundaries are set at the bottom of the pile foundation in the initial mesh model to generate a three-dimensional finite element model with boundary conditions.

[0030] In this embodiment, the geometric dataset is a dataset containing geometric parameters such as pile spacing, pile cap length, width, and height; the second-order tetrahedral element is a type of mesh element used for finite element analysis, with four vertices, which can adapt to the division of complex geometric shapes; the initial mesh model is the basic model obtained after meshing the pile foundation and pile cap; the fixed constraint boundary refers to the constraint conditions that restrict the movement and rotation of the bottom of the pile foundation in three spatial directions; the three-dimensional finite element model with boundary conditions is the mesh model after applying the fixed constraint boundary.

[0031] In some embodiments, the construction of the three-dimensional finite element model further includes:

[0032] Based on the material library associated with the steel grade of the storage tank, the coefficient of thermal expansion and modulus of elasticity under low temperature conditions are defined and stored in the material property set of the three-dimensional finite element model to generate a three-dimensional finite element model with material properties.

[0033] In this embodiment, the steel grade of the storage tank is a symbol that identifies the type of steel used in the storage tank and is used to determine the material properties; the material library is a database that stores the material parameters of different steels under different working conditions; the coefficient of thermal expansion is the ratio of the change in length per unit length of the material to the change in temperature when the temperature changes; the elastic modulus is a physical quantity that measures the material's ability to resist elastic deformation; the material property set is a collection that includes parameters such as the coefficient of thermal expansion and the elastic modulus of the material; and the three-dimensional finite element model with material properties is a complete finite element model after the material properties are assigned.

[0034] In this embodiment of the application, a three-dimensional finite element model including pile foundations and tank caps is constructed, including:

[0035] The first step is to extract the pile spacing and geometric dimensions of the tank foundation based on the tank design drawings, generating a geometric dataset for the tank. Specifically, technicians obtain the pile arrangement (e.g., rectangular arrangement) and spacing (e.g., 4 meters spacing both horizontally and vertically) by reading the parameter annotations in the tank design drawings, and simultaneously extract the geometric dimensions of the tank foundation (e.g., 30 meters long, 30 meters wide, and 2.5 meters thick). These parameters are then organized into structured data, such as recording the coordinates of the piles and the length, width, and height of the foundation in tabular form, forming the tank's geometric dataset. This step relies on the authority and accuracy of the design drawings to ensure that the geometry of the subsequent model is consistent with the actual structure.

[0036] The second step is to generate an initial mesh model by meshing the pile foundation and the tank cap using second-order tetrahedral elements based on the aforementioned geometric dataset. Specifically, the geometric dataset is imported into finite element analysis software (such as ANSYS or ABAQUS), which automatically identifies the contours of the pile foundation and cap based on the geometric parameters. Technicians set the meshing parameters, selecting second-order tetrahedral elements as the meshing units, and setting the element size (e.g., 0.3 meters for the pile foundation and 0.5 meters for the cap), then initiate the meshing function. The software generates a large number of second-order tetrahedral elements along the geometric boundaries of the pile foundation and cap. These elements are interconnected to form a mesh covering the entire structure, i.e., the initial mesh model. The reason for choosing second-order tetrahedral elements is their higher computational accuracy compared to first-order elements, enabling them to better capture stress changes in the structure under temperature and load conditions, making them particularly suitable for analyzing complex geometric areas such as the connection between the pile foundation and the cap.

[0037] It should be noted that if any software tools or components not belonging to our company appear in the embodiments of this application, they are merely for illustrative purposes and do not represent actual use.

[0038] The third step is to set fixed constraint boundaries at the bottom of the pile foundation in the initial mesh model to generate a three-dimensional finite element model with boundary conditions. During this process, in the finite element analysis software, select all the bottom nodes of the pile foundation in the initial mesh model. Using the software's constraint setting function, apply fixed constraints to these nodes, restricting their translational degrees of freedom in the X, Y, and Z directions and their rotational degrees of freedom about the three axes. After setting these constraints, the initial mesh model possesses boundary conditions that conform to the actual stress state, becoming a three-dimensional finite element model with boundary conditions. This operation is based on the fact that pile foundations are deeply buried underground in actual engineering projects, and their bottom displacement can be considered zero; fixed constraint boundaries can realistically simulate this stress state.

[0039] In this embodiment, constructing the three-dimensional finite element model further includes: defining the coefficient of thermal expansion and modulus of elasticity under cryogenic conditions based on a material library associated with the tank steel grade, storing these parameters in the material property set of the three-dimensional finite element model, and generating a three-dimensional finite element model with material properties. Specifically, technicians determine the tank steel grade (e.g., Q345R) based on the tank design drawings, and use software to call the associated material library to query the coefficient of thermal expansion (e.g., 1.2 × 10⁻⁶) of that steel grade under cryogenic conditions (e.g., -162°C, corresponding to the LNG medium temperature). -5 The parameters include (°C) and elastic modulus (e.g., 200 GPa). Inputting these parameters into the material property setting module of the finite element model, the software will store the parameters in the model's material property set and assign them to the corresponding mesh elements (e.g., the tank foundation uses C30 concrete, with an elastic modulus of 30 GPa and a thermal expansion coefficient of 1.0 × 10⁻⁶). -5 / ℃). The final generated three-dimensional finite element model with material properties can accurately reflect the material mechanical properties of the structure under low-temperature conditions.

[0040] In this embodiment, the above steps solve the problem of structural response simulation distortion caused by the use of simplified models (such as simplifying pile foundations to spring supports) in traditional analysis. By accurately extracting geometric parameters and generating high-quality meshes, the model's fidelity to the actual structure is ensured; the setting of fixed constraint boundaries makes the model's stress state closer to reality; and the definition of material properties under low-temperature conditions provides an accurate material parameter basis for subsequent stress analysis under temperature field effects, improving the reliability of stress calculation.

[0041] S2. Based on the liquid level height on the inner wall of the storage tank and the gas-liquid phase transition interface, the boundary of the low-temperature medium action domain is defined, and a non-uniform temperature field that decreases linearly with the liquid level height is generated.

[0042] In some embodiments, the step of defining the boundary of the cryogenic medium's action domain based on the liquid level height on the inner wall of the storage tank and the gas-liquid phase transition interface, and generating a non-uniform temperature field that decreases linearly with the liquid level height, includes:

[0043] Based on real-time monitored liquid level data, segmented coordinate intervals in the height direction of the tank inner wall are defined, generating an inner wall spatial coordinate set;

[0044] Based on the inner wall spatial coordinate set, a temperature abrupt change point is loaded at the gas-liquid phase change interface to generate a liquid level height-temperature mapping table.

[0045] According to the mapping table, a non-uniform temperature field mapping is performed on the inner wall of the three-dimensional finite element model.

[0046] In the embodiments of this application, the liquid level height refers to the vertical distance between the liquid surface of the cryogenic medium (such as LNG) and the bottom of the tank; the gas-liquid phase change interface is the interface between the gaseous and liquid states of the cryogenic medium in the tank; the cryogenic medium action zone is the area in contact between the inner wall of the tank and the cryogenic medium; and the non-uniform temperature field refers to the temperature distribution in which the temperature value changes with the height of the tank and exhibits a non-constant state.

[0047] In some embodiments, the step of loading a temperature abrupt change point at the gas-liquid phase transition interface based on the inner wall spatial coordinate set to generate a liquid level height-temperature mapping table includes:

[0048] Based on the inner wall spatial coordinate set, a first temperature value of the gas-liquid phase change interface is set at the zero point of the liquid level height to generate a phase change interface temperature reference.

[0049] A second temperature value at the bottom of the medium is set at the maximum liquid level height to generate a temperature reference for the bottom of the medium.

[0050] Based on the phase change interface temperature reference and the medium bottom temperature reference, a linearly decreasing temperature function is generated according to the liquid level height coordinate.

[0051] The temperature function is discretized into finite element nodal temperature loads to complete the construction of the non-uniform temperature field of the inner wall.

[0052] In this embodiment, the inner wall spatial coordinate set is a dataset containing the spatial positions of each segment node of the inner wall of the tank in the height direction; the temperature abrupt change point is a point where the temperature value changes significantly at the gas-liquid phase transition interface. The liquid level height-temperature mapping table is an association table recording the temperature values ​​corresponding to different liquid level heights. The phase transition interface temperature reference is the temperature setpoint at the gas-liquid phase transition interface; the medium bottom temperature reference is the temperature setpoint at the bottom of the low-temperature medium in the tank; the linearly decreasing temperature function is a function describing the linear decrease in temperature as the liquid level height increases; the finite element node temperature load is the temperature value assigned to each node of the finite element model after discretizing the temperature function.

[0053] In this embodiment of the application, based on the liquid level height on the inner wall of the storage tank and the gas-liquid phase transition interface, the boundary of the cryogenic medium action domain is defined, generating a non-uniform temperature field that decreases linearly with the liquid level height, including:

[0054] The first step is to define segmented coordinate intervals along the height direction of the tank's inner wall based on real-time monitored liquid level data, generating an inner wall spatial coordinate set. Specifically, real-time liquid level data (e.g., the current maximum liquid level is 12 meters) is acquired through a liquid level sensor built into the tank. Based on the required meshing accuracy of the finite element model, technicians divide the height direction of the tank's inner wall into segmented coordinate intervals at 0.5-meter intervals (e.g., 0-0.5 meters, 0.5-1 meter…11.5-12 meters), with the endpoints of each interval being coordinate nodes. The three-dimensional coordinates of these nodes (e.g., with the tank bottom center as the origin and the height direction as the Z-axis, the Z-coordinates of each node are 0, 0.5, 1…12 meters respectively) are then organized into structured data, forming the inner wall spatial coordinate set. This step relies on the accuracy of the real-time monitoring data to ensure that the coordinate intervals match the actual liquid level variation range, providing a precise spatial positioning basis for subsequent temperature field mapping.

[0055] The second step is to load a temperature abrupt change point at the gas-liquid phase transition interface based on the aforementioned inner wall spatial coordinate set, generating a mapping table of liquid level height-temperature. Specifically, first, the liquid level height corresponding to the gas-liquid phase transition interface is determined (e.g., real-time monitoring shows the phase transition interface at a liquid level height of 0 meters, i.e., the liquid surface at the bottom of the tank). Combining this with the characteristics of the cryogenic medium (e.g., the gas phase temperature of LNG is lower than the liquid phase temperature under standard atmospheric pressure), a temperature abrupt change point is loaded at this interface (e.g., the gas phase temperature is -163℃, and the liquid phase temperature is -162℃). Then, for the liquid phase region (0-12 meters), based on the thermodynamic characteristics of the medium, the bottom temperature of the medium is set at the maximum liquid level height (12 meters) (e.g., -160℃), and the temperature values ​​of each coordinate node are calculated linearly (e.g., -161.8℃ at 1 meter, -161.6℃ at 2 meters… -160℃ at 12 meters). The liquid level height and the corresponding temperature value are recorded one-to-one, forming a mapping table of liquid level height-temperature. The technical approach in this step is to accurately reflect the temperature characteristics of the gas-liquid phase transition by processing the mutation point, thus avoiding the errors caused by the traditional model simplifying the gas-liquid temperature to a continuous value.

[0056] The third step is to perform non-uniform temperature field mapping on the inner wall of the 3D finite element model according to the mapping table. During this process, the temperature data from the mapping table is imported into the finite element analysis software (such as ANSYS Workbench). Using the software's temperature load application function, the temperature values ​​corresponding to each liquid level height are assigned to the corresponding coordinate nodes of the inner wall of the 3D finite element model (e.g., -162℃ for the Z=0 meter node, -160℃ for the Z=12 meter node). The software automatically interpolates the temperature values ​​between adjacent nodes, ensuring a continuous gradient change in the temperature distribution across the entire inner wall, ultimately completing the construction of the non-uniform temperature field. This step is based on the principle of nodal load transfer in finite element analysis, ensuring a precise match between the temperature field and the model's geometry.

[0057] In this embodiment of the application, based on the inner wall spatial coordinate set, a temperature abrupt change point is loaded at the gas-liquid phase transition interface to generate a liquid level height-temperature mapping table, including:

[0058] First, based on the aforementioned inner wall spatial coordinate set, a first temperature value for the gas-liquid phase transition interface is set at the zero point of the liquid level, generating a phase transition interface temperature reference. For example, according to the gas-liquid phase transition characteristics of LNG, a first temperature value of -162℃ is set at the liquid level of 0 meters (phase transition interface). This value serves as the reference starting point for calculating the liquid phase temperature, ensuring a significant distinction from the gas phase temperature (the gas phase temperature can be set separately to -163℃).

[0059] Secondly, a second temperature value is set at the maximum liquid level to create a temperature reference for the bottom of the medium. For example, a second temperature value of -160°C is set at a liquid level of 12 meters (bottom of the medium). This value is determined based on the pressure and thermodynamic properties of the medium at the bottom of the tank, reflecting the slight increasing trend of temperature in the liquid phase region with increasing depth.

[0060] Then, based on the phase change interface temperature reference and the medium bottom temperature reference, a linearly decreasing temperature function is generated according to the liquid level height coordinate. According to the principle that two points determine a straight line, the temperature function can be expressed as: Temperature = First temperature value + (Second temperature value - First temperature value) × (Liquid level height / Maximum liquid level height). Substituting the values, the function is T = -162 + (-160 + 162) × (h / 12) = -162 + (2h) / 12, where h is the liquid level height (unit: meters). This function accurately describes the linear decrease in temperature in the liquid phase region with increasing height, breaking through the traditional assumption of uniform temperature and demonstrating the creativity of this step.

[0061] Finally, the temperature function is discretized into finite element nodal temperature loads to complete the construction of the non-uniform temperature field of the inner wall. For example, based on the node heights (h = 0, 0.5, 1...12 meters) in the spatial coordinate set of the inner wall, the temperature of each node is calculated by substituting them into the above function (e.g., when h = 0.5 meters, T = -162 + (2 × 0.5) / 12 ≈ -161.92℃; when h = 6 meters, T = -162 + (2 × 6) / 12 = -161℃). These discrete temperature values ​​are then assigned as loads to the corresponding finite element nodes, ensuring that the temperature field is fully adapted to the model mesh.

[0062] In this embodiment, the above steps address the problem of temperature field distortion caused by traditional analysis methods that simplify the internal temperature of the storage tank to a single value or ignore abrupt temperature changes during gas-liquid phase transitions. By accurately defining the domain of the cryogenic medium, setting temperature abrupt change points, and modeling linear functions, the temperature field distribution is made to better reflect the actual thermodynamic state of cryogenic media such as LNG, providing accurate temperature boundary conditions for subsequent thermo-mechanical coupling analysis.

[0063] In this embodiment, the inner wall spatial coordinate set provides a spatial positioning basis for loading temperature abrupt change points. Without precise coordinate nodes, temperature values ​​cannot be accurately correlated with tank wall positions. The liquid level height-temperature mapping table is the basis for temperature function discretization, and its data accuracy directly affects the accuracy of temperature loads at finite element nodes. The construction of a non-uniform temperature field is the final output of all previous steps. This temperature field will be used as input to subsequent thermo-mechanical coupling calculation steps, combined with the three-dimensional finite element model, to jointly serve the accurate analysis of tank pile foundation stress under complex temperature fields.

[0064] S3. Apply an ambient temperature load, segmented according to height, to the outer surface of the tank in the three-dimensional finite element model. The ambient temperature load is determined based on local extreme low temperature records.

[0065] In this embodiment of the application, the ambient temperature load refers to the load borne by the outer surface of the storage tank due to changes in atmospheric temperature.

[0066] In some embodiments, applying an ambient temperature load segmented along the height direction to the outer surface of the tank in the three-dimensional finite element model includes:

[0067] Obtain extreme low temperature data recorded by local weather stations to generate a raw temperature dataset;

[0068] The original temperature dataset was divided into three continuous temperature gradient intervals based on altitude.

[0069] The average temperature value of each gradient interval is assigned to the corresponding height segment of the outer surface of the tank in the three-dimensional finite element model to generate an environmental temperature load field.

[0070] In this embodiment, the local extreme low temperature record refers to the historical lowest temperature data recorded by the meteorological station where the storage tank is located; the original temperature dataset is a set of temperature data formed after organizing the local extreme low temperature records; the temperature gradient interval is an interval with continuously changing temperature, divided according to altitude. The environmental temperature load field is a temperature distribution field formed by assigning the average temperature value of each temperature gradient interval to the corresponding height segment of the outer surface of the storage tank.

[0071] In some embodiments, the coupling of the non-uniform temperature field and the ambient temperature load includes:

[0072] The spatial coordinates of three continuous temperature gradient intervals on the outer surface of the storage tank are aligned with the liquid level height interval on the inner wall of the storage tank to generate a spatial mapping relationship between the temperature fields of the inner and outer walls of the storage tank.

[0073] Based on the spatial mapping relationship of the inner and outer wall temperature fields, the non-uniform temperature field of the inner wall and the temperature gradient load of the outer wall are superimposed in the thickness direction of the tank wall to generate an initial coupled temperature field.

[0074] The initial coupled temperature field is input into the heat conduction equation to solve the steady-state solution of the temperature distribution in the wall thickness direction, thereby generating a dual-gradient coupled temperature field.

[0075] In this embodiment, the spatial mapping relationship between the inner and outer wall temperature fields is the correspondence between the temperature gradient range on the outer surface of the tank and the liquid level height range on the inner wall in spatial coordinates; the initial coupled temperature field is the temperature field formed after superimposing the non-uniform temperature field on the inner wall and the temperature gradient load on the outer wall in the tank wall thickness direction; the heat conduction equation is a mathematical equation describing the law of heat transfer in the medium; the dual gradient coupled temperature field is a coupled temperature field that exhibits a stable temperature distribution in the wall thickness direction, obtained by solving the heat conduction equation.

[0076] In this embodiment of the application, an ambient temperature load, segmented along the height direction, is applied to the outer surface of the storage tank in the three-dimensional finite element model, including:

[0077] The first step is to acquire extreme low-temperature data recorded by local weather stations to generate a raw temperature dataset. Specifically, technicians collect extreme low-temperature records for the region over the past 30 years by accessing public databases or historical observation reports from local weather stations (for example, the lowest temperature recorded in a northern region over the past 30 years is -35℃; extreme low-temperature data at different altitudes are obtained through gradient observations from the weather stations). This data is then organized into structured tables by year and observation altitude. The tables include observation altitudes (e.g., 1 meter, 5 meters, 10 meters, 15 meters) and corresponding extreme low-temperature values ​​(e.g., -35℃ at 1 meter, -32℃ at 5 meters, -28℃ at 10 meters, -25℃ at 15 meters), forming the raw temperature dataset. This step relies on the authority and continuity of the meteorological data to ensure that the environmental temperature load is set based on real meteorological conditions.

[0078] The second step is to divide the original temperature dataset into three continuous temperature gradient intervals based on altitude. Assuming the total height of the storage tank is 15 meters, technicians, based on the temperature change trends at different altitudes in the original temperature dataset, divided the 0-15 meter height range into three continuous intervals: 0-5 meters, 5-10 meters, and 10-15 meters. By calculating the average of extreme low-temperature data within each interval (e.g., -33℃ for the 0-5 meter interval, -30℃ for the 5-10 meter interval, and -26℃ for the 10-15 meter interval), the representative temperature of each gradient interval is determined. This division is based on the physical characteristic that atmospheric temperature exhibits a gradient change with increasing altitude; the division into three intervals simplifies calculations and reflects the temperature change trend.

[0079] The third step is to assign the average temperature value of each gradient interval to the corresponding height segment of the tank's outer surface in the 3D finite element model, generating an environmental temperature load field. During this process, the height coordinates of the tank's outer surface in the 3D finite element model are matched with the divided temperature gradient intervals (e.g., 0-5 meters corresponds to the first interval, 5-10 meters to the second interval, and 10-15 meters to the third interval). Using the load application function of the finite element analysis software, the average temperature values ​​of each interval (-33℃, -30℃, -26℃) are assigned to the corresponding height segment's outer surface nodes. The software automatically smooths the temperature values ​​between nodes, ensuring a continuous gradient change in the outer surface temperature distribution, ultimately generating the environmental temperature load field. This step ensures a precise spatial correspondence between the environmental temperature load and the tank's outer surface, avoiding the simplification of the actual environment by traditional uniform temperature loads.

[0080] In this embodiment of the application, the coupling of the non-uniform temperature field and the ambient temperature load includes:

[0081] The first step is to align the three continuous temperature gradient intervals on the outer surface of the storage tank with the liquid level intervals on the inner wall of the tank using spatial coordinates, generating a spatial mapping relationship between the temperature fields of the inner and outer walls of the tank. Assuming the liquid level interval on the inner wall of the tank is 0-15 meters (consistent with the total height of the tank), the temperature gradient intervals on the outer wall (0-5 meters, 5-10 meters, and 10-15 meters) are mapped one-to-one with the liquid level intervals at the same height on the inner wall (e.g., 0-5 meters on the outer wall corresponds to 0-5 meters on the inner wall, 5-10 meters on the outer wall corresponds to 5-10 meters on the inner wall, etc.). By establishing a spatial coordinate lookup table, the correspondence between the inner and outer wall temperatures at each height node is clarified (e.g., at a height of 5 meters, the inner wall temperature is -161℃, and the outer wall temperature is -30℃), generating a spatial mapping relationship between the temperature fields of the inner and outer walls. This step is fundamental to achieving coupling, ensuring that the inner and outer temperature fields are spatially superimposed, demonstrating the ingenuity of this step.

[0082] The second step, based on the spatial mapping relationship between the inner and outer wall temperature fields, involves superimposing the non-uniform temperature field of the inner wall and the temperature gradient load of the outer wall along the tank wall thickness direction to generate an initial coupled temperature field. Taking a tank wall thickness of 0.5 meters as an example, for each height node (e.g., at 5 meters), the inner wall temperature is -161℃ and the outer wall temperature is -30℃. These two temperature values ​​are superimposed linearly along the wall thickness direction (i.e., the temperature gradually transitions from -161℃ to -30℃ from the inner wall to the outer wall). The same operation is performed on all height nodes to form a temperature distribution covering the entire tank wall, i.e., the initial coupled temperature field. The superposition operation is based on the characteristic of continuous temperature transfer in a solid medium, and the initial coupled temperature field initially reflects the combined effect of the inner and outer temperatures.

[0083] The third step is to input the initial coupled temperature field into the heat conduction equation, solve for the steady-state solution of the temperature distribution along the wall thickness, and generate a dual-gradient coupled temperature field. The expression of the heat conduction equation in Cartesian coordinates is: Where T is temperature, t is time, and α is the thermal diffusivity (determined based on the tank material; for example, α for steel is approximately 1.2 × 10⁻⁶). -5 m 2 The initial coupled temperature field is input as a boundary condition into the equation, and the steady-state solution (i.e., the solution where the temperature does not change with time) is solved using finite element software. This yields the accurate temperature distribution along the wall thickness (e.g., at a height of 5 meters, the temperature at the midpoint of the wall thickness may be -95.5℃, not a simple linear superposition of -95.5℃, due to the nonlinear distribution caused by the thermal conductivity of the material). The resulting dual-gradient coupled temperature field accurately reflects the interaction between the non-uniform temperature of the inner wall and the gradient temperature of the outer wall along the wall thickness, providing accurate temperature boundary conditions for subsequent thermo-mechanical coupling analysis.

[0084] In this embodiment, the above steps address the problem that traditional analysis methods neglect the differences in ambient temperature and the interaction between internal and external temperature fields. By setting the ambient temperature load in segments, the external temperature distribution is made more closely resemble actual meteorological conditions. Through dual-gradient coupling logic, the true temperature state of the tank wall under the combined action of internal and external temperatures is accurately simulated, providing a reliable temperature input for subsequent stress analysis.

[0085] In the embodiments of this application, the division of the temperature gradient interval determines the distribution pattern of the ambient temperature load field; the spatial mapping relationship of the inner and outer wall temperature fields provides a spatial correspondence basis for the superposition of temperature fields.

[0086] S4. Based on the non-uniform temperature field and the ambient temperature load, a temperature stress distribution cloud map of the pile foundation is generated through thermo-mechanical coupling calculation.

[0087] In the embodiments of this application, thermo-mechanical coupling calculation is an analysis process that simultaneously considers the interaction between the temperature field and the stress field. By establishing the correlation between temperature change and structural stress, accurate simulation of the stress state of the structure can be achieved.

[0088] In some embodiments, generating the temperature stress distribution cloud map of the pile foundation through thermo-mechanical coupling calculation based on the non-uniform temperature field and the ambient temperature load includes:

[0089] The non-uniform temperature field is input into the transient heat conduction equation to calculate the transient temperature distribution field of the storage tank;

[0090] Based on the thermal expansion coefficient, the transient temperature distribution field is mapped into a thermal strain field;

[0091] Based on the elastic modulus, the thermal strain field is transformed into a thermal stress field using the generalized Hooke's law;

[0092] The additional deformation field caused by the ambient temperature load is superimposed on the thermal stress field to generate a temperature stress distribution cloud map of the pile foundation.

[0093] In this embodiment, the transient heat conduction equation is a mathematical equation describing the temperature variation over time and space, used to calculate the temperature distribution of the structure under unsteady temperature conditions; the transient temperature distribution field is the spatial distribution of the temperature of the structure at different times; the thermal strain field is the spatial distribution of the structural strain caused by temperature changes; the generalized Hooke's law describes the relationship between stress and strain in a material within its elastic range, and stress can be calculated through strain; the thermal stress field is the spatial distribution of stress generated by temperature changes; the additional deformation field is the spatial distribution of structural deformation caused solely by environmental temperature loads; and the pile foundation temperature stress distribution cloud map is a graphical representation of the magnitude of temperature stress at various parts of the pile foundation, displayed intuitively through color gradients.

[0094] In this embodiment of the application, based on the non-uniform temperature field and the ambient temperature load, a temperature stress distribution cloud map of the pile foundation is generated through thermo-mechanical coupling calculation, including:

[0095] The first step is to input the non-uniform temperature field into the transient heat conduction equation to calculate the transient temperature distribution field of the storage tank. Specifically, the non-uniform temperature field generated in S2 (e.g., -162℃ at 0 meters and -160℃ at 12 meters on the inner wall) is used as the initial boundary condition and input into the transient heat conduction equation. The expression of the transient heat conduction equation is as follows: Where T is temperature, t is time, and α is the thermal diffusivity (for tank steel, α is taken as 1.2 × 10⁻⁶). -5 m 2 / s). Using the thermal analysis module of finite element analysis software (such as ABAQUS), a time step (e.g., 1 minute / step) is set, and the equations are solved to obtain the temperature distribution of the storage tank and pile foundation at different times (e.g., 0 hours, 1 hour, 2 hours). For example, after 1 hour of calculation, the temperature at the top of the pile foundation drops from an initial 20℃ to -5℃, while the temperature at the bottom remains at 15℃, forming a temperature gradient along the pile length, i.e., the transient temperature distribution field. This step is based on the fundamental physical laws of heat conduction, capturing the dynamic changes in temperature over time through transient analysis, avoiding the limitations of traditional steady-state analysis that ignores the temperature change process.

[0096] The second step is to map the transient temperature distribution field into a thermal strain field based on the aforementioned coefficient of thermal expansion. According to the thermal expansion and contraction characteristics of materials, thermal strain has a linear relationship with temperature change, and the calculation formula is ε=α·ΔT, where ε is the thermal strain and α is the coefficient of thermal expansion defined in S1 (1.2×10⁻⁶). -5 / ℃, where ΔT is the temperature change at each node in the transient temperature distribution field (relative to the initial temperature of 20℃). For example, if the temperature change at the top node of the pile foundation is ΔT = -5℃ - 20℃ = -25℃, then the thermal strain ε at that node is 1.2 × 10⁻⁶. -5 / ℃×(-25℃)=-3×10 -4 (The negative sign indicates contraction). Finite element analysis software is used to assign thermal strain values ​​to each node, creating a thermal strain field. The top of the pile foundation exhibits larger contraction strain, while the bottom shows smaller strain, displaying a strain gradient along the length. This step utilizes material properties to directly convert temperature changes into deformation trends, providing a foundation for subsequent stress calculations.

[0097] The third step is to transform the thermal strain field into a thermal stress field based on the elastic modulus and using the generalized Hooke's law. The generalized Hooke's law simplifies to σ = E·ε under uniaxial stress, where σ is the thermal stress, E is the elastic modulus of 200 GPa defined in S1, and ε is the strain value in the thermal strain field. For example, the thermal stress at the top node of the pile foundation is σ = 200 × 10⁻⁶. 9 Pa×(-3×10 -4 = -60MPa (the negative sign indicates compressive stress). For multiaxial stress states, the software calculates the stress components in each direction based on the model's constraints and geometry using the complete form of the generalized Hooke's law (considering Poisson's ratio, e.g., 0.3 for steel), ultimately forming a thermal stress field. In this field, the compressive stress at the top of the pile foundation is relatively large, while the stress at the bottom is relatively small, and stress concentration occurs at the connection between the pile foundation and the cap due to constraints. The innovation of this step lies in combining the laws of mechanics of materials with finite element analysis, transforming abstract strain into quantifiable stress, accurately reflecting the internal forces generated when temperature deformation is constrained.

[0098] The fourth step is to superimpose the additional deformation field caused by the ambient temperature load onto the thermal stress field to generate a temperature stress distribution cloud map of the pile foundation. First, the structural deformation caused by the ambient temperature load in S3 (e.g., -33℃ at 0-5 meters on the outer surface) is calculated separately to obtain the additional deformation field (e.g., the deformation of the tank's outer wall due to low-temperature contraction, which is then transferred to the pile foundation as additional strain). Then, using the stress superposition function of the finite element software, the stress corresponding to the additional deformation field (e.g., the additional tensile stress of 5MPa experienced by the pile foundation due to outer wall contraction) is vector-superimposed with the stress in the thermal stress field (e.g., the total stress at the top node is -60MPa + 5MPa = -55MPa). After superposition, the software visualizes the stress values ​​of various parts of the pile foundation using color gradients (e.g., blue represents low stress, red represents high stress), generating a temperature stress distribution cloud map, where stress concentration areas (e.g., the connection between the top of the pile foundation and the pile cap) are displayed in dark red. This step ensures that the combined effects of internal and external temperature loads are fully considered, solving the problem of incomplete stress calculations caused by traditional methods that only handle internal or external temperatures.

[0099] In this embodiment, the above steps address the problem that traditional analysis methods neglect the coupling effect between the temperature field and the stress field, and cannot accurately simulate the stress state of pile foundations under complex temperature conditions. By capturing dynamic temperature changes through transient heat conduction analysis, and finally superimposing the effects of internal and external temperatures, the simulation results of pile foundation stress distribution are made closer to the actual engineering conditions, providing a reliable basis for subsequent bearing capacity verification.

[0100] S5. Analyze the axial internal force and bending moment values ​​of the pile section from the temperature stress distribution cloud map and output them to the pile foundation bearing capacity verification module.

[0101] In this embodiment of the application, the temperature stress distribution cloud map is a graphical result that intuitively displays the magnitude of temperature stress in various parts of the pile foundation through color gradient, with different colors representing different stress values; the axial internal force is the tensile or compressive force on the pile body section in the axial direction; the bending moment value is the moment that causes the pile body to bend and deform.

[0102] In some embodiments, the step of analyzing the axial internal force and bending moment values ​​of the pile section from the temperature stress distribution cloud map includes:

[0103] Based on the color gradient distribution in the temperature stress distribution cloud map, the area of ​​maximum stress concentration on the pile surface is identified.

[0104] Extract the normal stress components of all finite element elements in the maximum stress concentration region, integrate the normal stress components along the edge of the cross section, and output the axial internal force and bending moment values.

[0105] In this embodiment, the pile foundation bearing capacity verification module is a computer program module used to verify whether the pile foundation meets the design strength requirements when subjected to axial internal force and bending moment; the color gradient distribution is the change of color from light to dark or from dark to light in the temperature stress distribution cloud map, reflecting the increase or decrease of stress value; the maximum stress concentration area is the part of the pile surface where the stress value is significantly higher than the surrounding area; the normal stress component is the stress component perpendicular to the pile cross section.

[0106] In this embodiment of the application, the axial internal force and bending moment values ​​of the pile section are analyzed from the temperature stress distribution cloud map and output to the pile foundation bearing capacity verification module, including:

[0107] The first step is to identify the area of ​​maximum stress concentration on the pile surface based on the color gradient distribution in the temperature stress distribution cloud map. Specifically, the post-processing module of the finite element analysis software is opened, and the temperature stress distribution cloud map generated by S4 is retrieved. The color gradient in the cloud map typically changes from blue to green to red according to the stress value (e.g., blue corresponds to below 50 MPa, and red corresponds to above 80 MPa). By observing the color gradient distribution in the cloud map, technicians can locate the area with the darkest color (e.g., red) and a relatively concentrated area; this area is the region of maximum stress concentration. Taking an LNG storage tank pile foundation as an example, the region of maximum stress concentration usually appears at the connection between the top of the pile foundation and the pile cap, because this area is more constrained, and stress generated by temperature deformation tends to accumulate here. This step is based on the mechanical characteristics of stress concentration phenomena, namely, stress concentration easily occurs at structural abrupt changes. The color gradient can quickly pinpoint the area requiring focused analysis, providing a target range for subsequent internal force calculations.

[0108] The second step is to extract the normal stress components of all finite element elements in the region of maximum stress concentration, integrate these normal stress components along the edge of the cross section, and output the axial internal force and bending moment values. Specifically, in the finite element software, select all finite element elements in the region of maximum stress concentration (e.g., elements at the top of the pile foundation cross section). Using the software's stress extraction function, obtain the normal stress component of each element (i.e., the stress value perpendicular to the pile cross section; for example, the normal stress of one element is 80 MPa, and another is 75 MPa). For axial internal force calculation, multiply the normal stress component of each element by the area of ​​that element within the cross section, and then sum the calculation results of all elements to obtain the axial internal force of the entire cross section (for example, if the total cross section area is 1.13 square meters, the sum of the products of the stress and area of ​​each element is 90.4 kN, i.e., the axial internal force is 90.4 kN). To calculate the bending moment, the neutral axis of the cross-section must first be determined (i.e., the axis of symmetry of the cross-section; for a circular pile foundation with a diameter of 1.2 meters, the neutral axis is the axis containing the center of the cross-section). Then, the normal stress component of each element is multiplied by the distance from that element to the neutral axis, and then multiplied by the element area. Finally, the calculation results of all elements are summed to obtain the bending moment value (for example, an element with a distance of 0.6 meters from the neutral axis, a stress of 80 MPa, and an area of ​​0.01 square meters has a contribution value of 80 × 10⁻⁶). 6 Pa × 0.6m × 0.01m 2 =48000 N·m, and the cumulative bending moment of all elements is 9.04 kN·m). This step is based on the relationship between internal force and stress in mechanics of materials. By integrating, the distributed stress is transformed into concentrated internal force parameters. This is a key transformation from stress field to practical engineering parameters, which reflects the creativity of this step. Compared with the traditional method of only taking the maximum stress value for evaluation, the integral method can more comprehensively reflect the overall stress state of the cross section.

[0109] The above steps solve the problem that traditional methods cannot directly obtain practical internal force parameters for engineering from stress distribution cloud maps. By accurately identifying stress concentration areas and performing integral calculations, the obtained axial internal force and bending moment values ​​can be directly used for pile foundation bearing capacity verification, avoiding safety redundancy or insufficiency caused by misjudgment of local stress and improving the reliability of the verification results.

[0110] In the embodiments of this application, identifying the region of maximum stress concentration is a prerequisite for extracting the normal stress component. Only by determining the target region can effective stress data be obtained in a targeted manner.

[0111] like Figure 2 The diagram shown is a functional block diagram of a storage tank stress analysis system based on temperature conditions provided in an embodiment of the present invention.

[0112] The temperature-condition-based tank stress analysis system 100 of this invention can be installed in an electronic device. Depending on the functions implemented, the temperature-condition-based tank stress analysis system 100 may include a finite element model construction module 101, an inner wall temperature field generation module 102, an outer surface temperature modeling module 103, a thermo-mechanical coupling calculation module 104, and a stress analysis module 105. The module described in this invention can also be called a unit, which refers to a series of computer program segments that can be executed by the processor of an electronic device and can perform a fixed function, stored in the memory of the electronic device.

[0113] In this embodiment, the functions of each module / unit are as follows:

[0114] Finite element model construction module 101 is used to construct a three-dimensional finite element model including pile foundation and tank cap;

[0115] The inner wall temperature field generation module 102 is used to divide the boundary of the low temperature medium action area according to the liquid level height and gas-liquid phase change interface of the inner wall of the storage tank, and generate a non-uniform temperature field that decreases linearly with the liquid level height.

[0116] The external surface temperature modeling module 103 is used to apply an environmental temperature load set in segments along the height direction to the outer surface of the tank in the three-dimensional finite element model. The environmental temperature load is determined based on local extreme low temperature records.

[0117] Thermo-mechanical coupling calculation module 104 is used to generate a temperature stress distribution cloud map of the pile foundation based on the non-uniform temperature field and the ambient temperature load through thermo-mechanical coupling calculation.

[0118] The stress analysis module 105 is used to analyze the axial internal force and bending moment values ​​of the pile section from the temperature stress distribution cloud map and output them to the pile foundation bearing capacity verification module.

[0119] In the several embodiments provided by this invention, it should be understood that the disclosed methods and systems can be implemented in other ways. For example, the system embodiments described above are merely illustrative; for instance, the division of modules is only a logical functional division, and other division methods may be used in actual implementation.

[0120] The modules described as separate components may or may not be physically separate. The components shown as modules may or may not be physical units; that is, they may be located in one place or distributed across multiple network units. Some or all of the modules can be selected to achieve the purpose of this embodiment according to actual needs.

[0121] Furthermore, the functional modules in the various embodiments of the present invention can be integrated into one processing unit, or each unit can exist physically separately, or two or more units can be integrated into one unit. The integrated unit can be implemented in hardware or in the form of hardware plus software functional modules.

[0122] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the present invention can be implemented in other specific forms without departing from the spirit or essential characteristics of the present invention.

[0123] The embodiments of this application can acquire and process relevant data based on artificial intelligence technology. Artificial intelligence is the theory, method, technology, and application system that uses digital computers or machines controlled by digital computers to simulate, extend, and expand human intelligence, perceive the environment, acquire knowledge, and use that knowledge to obtain optimal results.

[0124] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit it. Although the present invention has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of the present invention without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A method for stress analysis of storage tanks based on temperature conditions, characterized in that, The method includes: Construct a three-dimensional finite element model including pile foundations and tank caps; Based on the liquid level height and gas-liquid phase transition interface on the inner wall of the storage tank, the boundary of the cryogenic medium's action domain is defined, and a non-uniform temperature field that decreases linearly with the liquid level height is generated. This includes: defining segmented coordinate intervals of the inner wall of the storage tank in the height direction based on real-time monitored liquid level height data, and generating an inner wall spatial coordinate set; based on the inner wall spatial coordinate set, loading temperature abrupt change points at the gas-liquid phase transition interface, and generating a liquid level height-temperature mapping table; and performing non-uniform temperature field mapping on the inner wall of the three-dimensional finite element model according to the mapping table. An ambient temperature load, segmented according to height, is applied to the outer surface of the storage tank in the three-dimensional finite element model. The ambient temperature load is determined based on local extreme low temperature records. Based on the non-uniform temperature field and the ambient temperature load, a temperature stress distribution cloud map of the pile foundation is generated through thermo-mechanical coupling calculation. The axial internal force and bending moment values ​​of the pile section are analyzed from the temperature stress distribution cloud map and output to the pile foundation bearing capacity verification module.

2. The method for stress analysis of storage tanks based on temperature conditions as described in claim 1, characterized in that, The construction of the three-dimensional finite element model, which includes the pile foundation and the tank cap, includes: Extract the pile spacing and geometric dimensions of the tank foundation from the tank design drawings to generate a geometric dataset of the tank. Based on the geometric dataset, second-order tetrahedral elements are used to divide the pile foundation and the tank pier into meshes to generate an initial mesh model; Fixed constraint boundaries are set at the bottom of the pile foundation in the initial mesh model to generate a three-dimensional finite element model with boundary conditions.

3. The method for stress analysis of storage tanks based on temperature conditions as described in claim 2, characterized in that, The construction of the three-dimensional finite element model also includes: Based on the material library associated with the steel grade of the storage tank, the coefficient of thermal expansion and the modulus of elasticity under low temperature conditions are defined and stored in the material property set of the three-dimensional finite element model to generate a three-dimensional finite element model with material properties.

4. The method for stress analysis of storage tanks based on temperature conditions as described in claim 1, characterized in that, The step of generating a liquid level-temperature mapping table based on the inner wall spatial coordinate set, by loading a temperature abrupt change point at the gas-liquid phase transition interface, includes: Based on the inner wall spatial coordinate set, a first temperature value of the gas-liquid phase change interface is set at the zero point of the liquid level height to generate a phase change interface temperature reference. A second temperature value at the bottom of the medium is set at the maximum liquid level height to generate a temperature reference for the bottom of the medium. Based on the phase change interface temperature reference and the medium bottom temperature reference, a linearly decreasing temperature function is generated according to the liquid level height coordinate. The temperature function is discretized into finite element nodal temperature loads to complete the construction of the non-uniform temperature field of the inner wall.

5. The method for stress analysis of storage tanks based on temperature conditions as described in claim 1, characterized in that, The application of an ambient temperature load segmented along the height direction to the outer surface of the tank in the three-dimensional finite element model includes: Obtain extreme low temperature data recorded by local weather stations to generate a raw temperature dataset; The original temperature dataset was divided into three continuous temperature gradient intervals based on altitude. The average temperature value of each gradient interval is assigned to the corresponding height segment of the outer surface of the tank in the three-dimensional finite element model to generate an environmental temperature load field.

6. The method for stress analysis of storage tanks based on temperature conditions as described in claim 5, characterized in that, The coupling between the non-uniform temperature field and the ambient temperature load includes: The spatial coordinates of three continuous temperature gradient intervals on the outer surface of the storage tank are aligned with the liquid level height interval on the inner wall of the storage tank to generate a spatial mapping relationship between the temperature fields of the inner and outer walls of the storage tank. Based on the spatial mapping relationship of the inner and outer wall temperature fields, the non-uniform temperature field of the inner wall and the temperature gradient load of the outer wall are superimposed in the thickness direction of the tank wall to generate an initial coupled temperature field. The initial coupled temperature field is input into the heat conduction equation to solve the steady-state solution of the temperature distribution in the wall thickness direction, thereby generating a dual-gradient coupled temperature field.

7. The method for stress analysis of storage tanks based on temperature conditions as described in claim 3, characterized in that, The process of generating a temperature stress distribution cloud map of the pile foundation based on the non-uniform temperature field and the ambient temperature load through thermo-mechanical coupling calculation includes: The non-uniform temperature field is input into the transient heat conduction equation to calculate the transient temperature distribution field of the storage tank; Based on the thermal expansion coefficient, the transient temperature distribution field is mapped into a thermal strain field; Based on the elastic modulus, the thermal strain field is transformed into a thermal stress field using the generalized Hooke's law; The additional deformation field caused by the ambient temperature load is superimposed on the thermal stress field to generate a temperature stress distribution cloud map of the pile foundation.

8. The method for stress analysis of storage tanks based on temperature conditions as described in claim 1, characterized in that, The process of analyzing the axial internal force and bending moment values ​​of the pile section from the temperature stress distribution cloud map includes: Based on the color gradient distribution in the temperature stress distribution cloud map, the area of ​​maximum stress concentration on the pile surface is identified. Extract the normal stress components of all finite element elements in the maximum stress concentration region, integrate the normal stress components along the edge of the cross section, and output the axial internal force and bending moment values.

9. A storage tank stress analysis system based on temperature conditions, characterized in that, The system includes: The finite element model building module is used to build a three-dimensional finite element model that includes pile foundations and tank caps; The inner wall temperature field generation module is used to delineate the boundary of the cryogenic medium's action domain based on the liquid level height and gas-liquid phase transition interface on the inner wall of the storage tank, and generate a non-uniform temperature field that decreases linearly with the liquid level height. This includes: defining segmented coordinate intervals of the inner wall of the storage tank in the height direction based on real-time monitored liquid level height data, generating an inner wall spatial coordinate set; loading temperature abrupt change points at the gas-liquid phase transition interface based on the inner wall spatial coordinate set, generating a liquid level height-temperature mapping table; and performing non-uniform temperature field mapping on the inner wall of the three-dimensional finite element model according to the mapping table. The external surface temperature modeling module is used to apply an environmental temperature load segmented in the height direction to the outer surface of the tank in the three-dimensional finite element model. The environmental temperature load is determined based on local extreme low temperature meteorological records. The thermo-mechanical coupling calculation module is used to generate a temperature stress distribution cloud map of the pile foundation based on the non-uniform temperature field and the ambient temperature load through thermo-mechanical coupling calculation; The stress analysis module is used to analyze the axial internal force and bending moment values ​​of the pile section from the temperature stress distribution cloud map and output them to the pile foundation bearing capacity verification module.

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