Sluice temperature field and temperature stress field calculation and analysis method and system

Abstract

The invention further provides a sluice temperature field and temperature stress field calculation and analysis method and system. The method comprises the following steps of 1, obtaining basic data; 2, establishing a three-dimensional finite element model; 3, setting calculation conditions; 4, a three-dimensional transient finite element method is adopted, the construction pouring process, environmental climate changes, manual cooling and heat preservation measures and changes of thermal and mechanical properties of materials along with time are comprehensively considered, hydration heat is applied in the form of volume force, calculation is conducted according to the difference value of previous and later time steps, and water pipe cooling is conducted according to negative hydration heat equivalent treatment; 5, temperature field simulation calculation is conducted in the whole process from the construction period to the operation period; 6, calculating a result based on the temperature field; 7, analyzing the distribution state and the change rule of the temperature field and the temperature stress field, and judging whether the temperature control index and the anti-cracking safety requirement specified by the specification are met or not; according to the technical scheme, simulation of the whole process from the construction period to the operation period is achieved, and the calculation result better fits the actual working condition.

Description

Technical Field

[0001] This invention relates to the field of temperature control technology for concrete structures in hydraulic engineering, and in particular to a method and system for calculating and analyzing the temperature field and temperature stress field of a sluice gate. Background Technology

[0002] Large-volume concrete is highly susceptible to temperature cracks due to its concentrated heat release during hydration and constrained volume deformation. The presence of cracks not only weakens the load-bearing capacity of the components but also accelerates concrete carbonation, causes leakage, and even endangers foundation stability, seriously affecting the safe operation and service life of water conservancy projects.

[0003] As a key water conservancy structure, the sluice gate has a large volume of concrete in its base slab and other parts, and the construction environment is complex (such as temperature fluctuations and variable pouring conditions), which further exacerbates the difficulty of controlling temperature cracks. Traditional methods for calculating temperature fields and temperature stress have many limitations: some methods do not fully consider the dynamic effects of the entire construction process (such as layered pouring, inter-layer intervals, and changes in construction progress); some methods do not adequately simulate the time dependence of material properties (such as concrete creep and the evolution of elastic modulus with age); and some methods ignore the coupling effect of key temperature control measures such as heat of hydration, water pipe cooling, and surface insulation, resulting in large deviations between the calculation results and actual working conditions, making it difficult to effectively guide the formulation of temperature control schemes.

[0004] Therefore, there is an urgent need for a comprehensive calculation and analysis method that takes into account multiple influencing factors, has high simulation accuracy, and fits the actual engineering situation, so as to achieve accurate prediction of the temperature field and temperature stress field of large-volume concrete in sluice gates throughout the entire process, and provide technical support for crack prevention and safety. Summary of the Invention

[0005] In view of this, the purpose of this invention is to provide a method and system for calculating and analyzing the temperature field and temperature stress field of a sluice gate. By integrating basic engineering data, accurately constructing a finite element model, and dynamically simulating the coupling effect of multiple fields, the system can accurately simulate the temperature and stress distribution law from the construction period to the operation period. Based on this, scientific and reasonable temperature control standards and measures can be formulated to effectively control the generation of temperature cracks and ensure that the crack resistance safety of the concrete structure meets the specifications.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: a method for calculating and analyzing the temperature field and temperature stress field of a sluice gate, comprising the following steps:

[0007] Step 1: Obtain basic data, including the climate conditions of the project area, the mechanical and thermal parameters of concrete and bedrock, the thermal insulation temperature rise data of materials, the equivalent heat release coefficient of the concrete surface insulation material, and the construction schedule.

[0008] Step 2: Establish a three-dimensional finite element model. The three-dimensional finite element model simulates the actual shape and structure of the sluice gate. Define the coordinate system, select a typical gate pier as the simulation object, and determine the thickness below the foundation surface and the dimensions of the foundation range.

[0009] Step 3: Set the calculation conditions, including: use the steady-state temperature field calculation result as the initial temperature of the foundation, take the initial temperature of the newly poured concrete as the pouring temperature, and take the average value of the upper and lower layer nodes as the initial temperature of the interface; treat the boundary of the foundation part as an adiabatic boundary condition, take the third type of boundary condition for the boundary between the sluice gate and the air, and take the third type of boundary condition or the adiabatic boundary condition for the side boundary according to the pouring sequence.

[0010] Step 4: Using the three-dimensional transient finite element method, the construction pouring process, environmental climate change, artificial cooling and heat preservation measures, and the changes in the thermomechanical properties of materials over time are comprehensively considered. The heat of hydration is applied in the form of volume force and calculated according to the time step difference. Water pipe cooling is treated as equivalent to negative heat of hydration.

[0011] Step 5: Perform temperature field simulation calculations for the entire process from construction to operation. Based on the principle of heat balance, derive the basic equation of solid heat conduction and solve the temperature distribution using the finite element governing equation.

[0012] Step 6: Based on the temperature field calculation results, considering the creep characteristics of concrete, the equivalent elastic modulus is adopted, and the temperature stress field is simulated and calculated through stress increment calculation, equilibrium equation solution and element stress superposition.

[0013] Step 7: Analyze the distribution and variation of the temperature field and temperature stress field to determine whether they meet the temperature control indicators and crack resistance safety requirements specified in the standards.

[0014] In a preferred embodiment, the formula for calculating concrete creep is an 8-parameter exponential function:

[0015]

[0016] In the formula: Indicates time; Indicates the loading age; Indicates the loading age is , The degree of creep over time; This represents the creep parameter.

[0017] In a preferred embodiment, a hyperbolic fitting test data was used to obtain the formula for the adiabatic temperature rise of concrete.

[0018] The hyperbolic formula used:

[0019] .

[0020] In a preferred embodiment, the formula for calculating the equivalent heat release coefficient β of the concrete surface insulation material is as follows:

[0021]

[0022] Where: h i Indicates the thickness of the insulation material; Indicates the thermal conductivity of the insulation material; This indicates the heat dissipation coefficient of the concrete surface without insulation. This represents the wind speed correction factor; This indicates a correction factor for humidity levels.

[0023] In a preferred embodiment, the coordinate system of the three-dimensional finite element model is defined as follows: X-axis along the river, Y-axis vertical, and Z-axis transverse; to simulate the pouring process, the elements are activated in stages according to the order from the foundation to the top of the slab, and the self-weight load and temperature load are applied simultaneously.

[0024] In a preferred embodiment, the boundary conditions for calculating the temperature field include a first type of boundary condition. Second type of boundary conditions Third type of boundary conditions h is the surface convection coefficient, T0 is the ambient temperature, and the temperature at any point within the element is obtained by interpolation using the element shape function. The finite element governing equation is derived based on the variational principle. .

[0025] In a preferred embodiment, in step 4, the heat conduction equation is solved using the three-dimensional transient finite element method based on the principle of heat balance: In the formula , , ; , , Thermal conductivity , , Thermal conductivity, For the specific heat of the material, For the material's density, , Describe the time and temperature respectively.

[0026] In a preferred embodiment, in step (6), the concrete strain calculation formula is: ,exist The formula for calculating the internal stress increment is: The equivalent elastic modulus The element stress is the sum of the stress increments at each time interval.

[0027] In a preferred embodiment, in step 6, the temperature stress balance equation is: The increase in nodal loads caused by external loads is ignored in the calculation. Increase in nodal load caused by drying shrinkage .

[0028] The present invention also provides a system for calculating and analyzing the temperature field and temperature stress field of a sluice gate, including a processor, a memory and a bus, wherein the memory stores machine-readable instructions executed by the processor;

[0029] When the system is running, the processor and the memory communicate via a bus, and the machine-readable instructions are executed by the processor as described in the method for calculating and analyzing the temperature field and temperature stress field of a sluice gate.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. This invention comprehensively considers various influencing factors such as climate in the engineering area, material properties (thermal, mechanical, creep, adiabatic temperature rise), construction process (layered pouring, progress, pouring temperature), and temperature control measures (insulation, water pipe cooling), and realizes full-process simulation from the construction period to the operation period. The calculation results are more in line with the actual working conditions.

[0032] 2. By employing the three-dimensional transient finite element method combined with element birth and death technology, the dynamic process of concrete pouring and the changes in boundary conditions are accurately simulated, which greatly improves the calculation accuracy of temperature field and stress field;

[0033] 3. By systematically analyzing the temperature and stress distribution patterns, it can directly provide quantitative basis for the formulation of temperature control standards (such as the temperature at the warehouse entrance and the control value of the temperature difference between the inside and outside) and the selection of temperature control measures (such as the thickness of the insulation material and the parameters of the cooling water flow), effectively avoiding the generation of temperature cracks;

[0034] 4. The method is highly versatile and can be widely applied to temperature control simulation analysis of various large-volume concrete hydraulic engineering projects (such as dams, locks, etc.), combining scientific rigor with economic efficiency. Attached Figure Description

[0035] Figure 1 This is a flowchart of the temperature field and temperature stress simulation calculation of a preferred embodiment of the present invention;

[0036] Figure 2 This is a gate pier casting model according to a preferred embodiment of the present invention;

[0037] Figure 3 This is the overall finite element calculation model of a preferred embodiment of the present invention;

[0038] Figure 4 This is the envelope diagram of the overall maximum temperature field of the gate pier according to a preferred embodiment of the present invention;

[0039] Figure 5 This is the maximum temperature field envelope diagram of the gate pier section according to a preferred embodiment of the present invention;

[0040] Figure 6 This is the overall maximum first principal stress envelope diagram of a preferred embodiment of the present invention;

[0041] Figure 7 This is the envelope diagram of the maximum first principal stress of the cross section in a preferred embodiment of the present invention;

[0042] Figure 8 This is a schematic diagram of the feature point positions in a preferred embodiment of the present invention;

[0043] Figure 9 This is a schematic diagram of the feature point temperature history curve of a preferred embodiment of the present invention;

[0044] Figure 10 This is a schematic diagram of the stress history curve of a feature point in a preferred embodiment of the present invention. Detailed Implementation

[0045] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0046] It should be noted that the following detailed descriptions are illustrative and intended to provide further explanation of this application. Unless otherwise specified, all technical and scientific terms used in this application have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains.

[0047] It should be noted that the terminology used herein is for the purpose of describing particular implementations only and is not intended to limit the exemplary implementations according to this application; as used herein, the singular form is intended to include the plural form as well, unless the context clearly indicates otherwise; furthermore, it should be understood that when the terms “comprising” and / or “including” are used in this specification, they indicate the presence of features, steps, operations, devices, components and / or combinations thereof.

[0048] A method and system for calculating and analyzing the temperature field and temperature stress field of a sluice gate, referenced. Figure 1-10 The following detailed description of the specific implementation of the present invention is based on a sluice gate project example in a certain area:

[0049] 1. Project Overview

[0050] The sluice gate reconstruction project is located in Province A and is classified as a Class I (1) large-scale project. The main structure uses C35 concrete. The South Port Sluice Gate is about 200m long (15 gates, each with a net width of 10m) and the North Port Sluice Gate is about 293m long (25 gates, each with a net width of 10m). The bottom slab has a large volume of concrete and the construction environment is complex, so temperature control and crack prevention analysis are required.

[0051] 2. Basic Data

[0052] 2.1 Climate conditions in the project area

[0053] A sluice gate is located in City B, Province A, situated at the estuary of the C River. The project site is located in southeastern Province A, on the alluvial plain of the lower reaches of the D River, north of the Tropic of Cancer. Based on meteorological data collected from the project area, the multi-year monthly average temperature statistics are shown in Table 2.1-1 below:

[0054] Table 2.1-1 Statistical Table of Monthly Average Temperatures Over Many Years (Unit: °C)

[0055]

[0056] 2.2 Material mechanical and thermal parameters

[0057] 2.2.1 Thermal parameters of concrete

[0058] C35 concrete was used for the large-volume concrete, and its thermal parameters are shown in Table 2.2-1.

[0059] Table 2.2-1 Thermal Calculation Parameters for Concrete

[0060]

[0061] 2.2.2 Mechanical parameters of concrete

[0062] Concrete exhibits elastic creep, and creep should be considered when calculating temperature stress. The calculation should refer to "Temperature Stress and Temperature Control of Mass Concrete" compiled by Zhu Bofang. The formula for calculating concrete creep uses an 8-parameter exponential function:

[0063]

[0064] In the formula: —Time (days); — Loading age (days); — Loading age is , The degree of creep over time; — Creep parameters.

[0065] Based on previous engineering data and concrete creep test curves, concrete creep parameters were fitted, as shown in Table 2.2-2 below:

[0066] Table 2.2-2 Fitting results of concrete creep parameters

[0067]

[0068] The concrete mechanical parameters required for this calculation are shown in Table 2.2-3 below:

[0069] Table 2.2-3 Mechanical Parameters of Concrete

[0070]

[0071] 2.2.3 Foundation Parameters

[0072] According to the "Construction Scheme for Large-Volume Concrete Sluice Gates", the foundation parameters are selected as shown in Table 2.2-4 below:

[0073] Table 2.2-4 Basic Mechanical Parameters

[0074]

[0075] 2.2.4 Material Adiabatic Temperature Rise

[0076] Based on the given concrete adiabatic temperature rise test data, this application uses hyperbolic fitting of the test data to obtain the concrete adiabatic temperature rise formula.

[0077] Hyperbolic formula used (°C):

[0078]

[0079] Based on previous engineering data, curve fitting was performed, and the final adiabatic temperature rise parameters are shown in Table 2.2-5 below:

[0080] Table 2.2-5 Parameters of Temperature Rise in Concrete Adiabatic Thermal Structure

[0081]

[0082] 2.2.5 Other parameters

[0083] The formula for calculating the equivalent heat release coefficient of concrete surface insulation material is as follows. The heat release coefficient in this application is taken as 13.08 (kJ / (m·h·℃)):

[0084]

[0085] Where: hi — thickness of insulation material, m; — Thermal conductivity of insulation materials, ; —The heat dissipation coefficient of the concrete surface without insulation. ; —Wind speed correction factor, taken as 1.6; —Moisture level correction factor, set to 1;

[0086] 2.3 Construction schedule;

[0087] In this simulation calculation, the building (concrete) calculation model is divided into 4 pouring layers. The pouring start time is December 24, 2024.

[0088] 3. Basic Calculation Principles

[0089] 3.1 Basic Principles of Temperature Field Calculation

[0090] To comprehensively reflect the effect and influence of temperature on the structural properties of the base slab, it is necessary to study the temperature field during the construction period of the base slab, and the changing temperature field with variations in air and water temperatures. Based on the principle of heat balance, the fundamental equation for heat conduction in solids can be derived:

[0091] (3.1-1)

[0092] For the absence of internal heat release (ω=0) and at a certain specific moment, the above equation degenerates into:

[0093] (3.1-2)

[0094] In the formula , ,

[0095] , , Thermal conductivity , , Thermal conductivity, For the specific heat of the material, For the material's density, , Describe the time and temperature respectively.

[0096] The boundary conditions of a temperature field can be mainly divided into the following three cases:

[0097] First type of boundary condition: The temperature distribution on the boundary S is known.

[0098] (3.1-3)

[0099] Second type of boundary condition: The heat flux density on boundary S is known.

[0100] , (3.1-4)

[0101] n is the outward normal vector S.

[0102] Third type of boundary condition: Convection conditions on known boundary S:

[0103] (3.1-5)

[0104] In the formula , Let h be a known function, h be the surface convection coefficient, and T0 be the ambient temperature.

[0105] The solution domain R is divided into a finite number of elements Ωe, and an element shape function is introduced. Then the temperature at any point within the element can be interpolated from the temperatures of the m nodes constituting the element:

[0106] (3.1-6)

[0107] Based on the variational principle, the finite element governing equations that satisfy the fundamental equations of heat conduction and the boundary conditions can be derived.

[0108] (3.1-7)

[0109] In the formula:

[0110] and:

[0111] (3.1-8)

[0112] (3.1-9).

[0113] 3.2 Basic Principles of Temperature Stress Calculation

[0114] Concrete blocks expand in volume when heated and contract in volume when cooled. The magnitude of this expansion or contraction is positively correlated with the linear expansion coefficient of the concrete, the temperature rise or fall, and the size of the block. When concrete is externally constrained, the volume deformation (expansion or contraction) caused by temperature changes cannot occur freely, thus inducing temperature stress. Furthermore, if the temperature change distribution across the concrete cross-section is non-linear, resulting in inconsistent volume deformation of the internal particles, stress will also be induced within the concrete; this situation is known as internal constraint.

[0115] The concrete volume of the foundation slab is relatively small, and its temperature is significantly affected by air temperature fluctuations. It cannot reach a stable temperature, instead transitioning from the highest temperature at the beginning of construction to a quasi-stable temperature that fluctuates with air temperature after completion. This process involves temperature changes and differences throughout the pouring process, which can be obtained through temperature field analysis. Furthermore, the temperature difference between the inside and outside of the concrete in the early stages of pouring causes significant surface stress. At this time, the concrete strength is low, making it prone to cracking. By analyzing the temperature difference between the inside and outside of the concrete in the early stages, the finite element method can be used to calculate the temperature stress.

[0116] (1) Concrete creep

[0117] The strain calculation formula is:

[0118] (3.2-1)

[0119] exist Internal strain increment:

[0120]

[0121] After sorting, a calculation period is obtained. The internal stress increment is:

[0122]

[0123] in, , which is the equivalent elastic modulus of concrete.

[0124] (2) Stress balance equations for each time period

[0125] The equilibrium equation is:

[0126] (3.2-2)

[0127] In the formula: —Stiffness matrix;

[0128]

[0129] —When calculating temperature stress, the nodal load increment caused by external loads can be ignored by other loads;

[0130] —Increment in nodal loads caused by creep;

[0131]

[0132] —Increase in nodal load caused by temperature variation;

[0133]

[0134] —Incremental load at nodes caused by the self-generated volumetric deformation of concrete;

[0135]

[0136] —The increase in node load caused by concrete drying shrinkage can be temporarily disregarded.

[0137]

[0138] (3) Element stress

[0139] The element stress is equal to the sum of the stress increments at each time interval, that is:

[0140] (3.2-3)

[0141] (4) Stress increment

[0142] The stress increments for each time period are:

[0143] (3.2-4)

[0144] In the formula: —Element strain increment caused by nodal displacement;

[0145]

[0146] —The increase in strain caused by concrete creep;

[0147]

[0148]

[0149]

[0150]

[0151]

[0152]

[0153]

[0154]

[0155] —The increase in strain caused by temperature changes in concrete;

[0156] —The strain increment caused by the autogenous volume deformation of concrete;

[0157] —The increase in strain caused by concrete drying shrinkage.

[0158] Ignore during calculation ,but

[0159]

[0160] 3.3 Computational Simulation Technology Processing

[0161] 1) Foundation slab concrete pouring process

[0162] The shape of the foundation slab concrete changes continuously during the layered and segmented pouring process, which can be simulated using element birth and death calculations. First, a finite element model is established based on the planned pouring process of the foundation slab. Then, the newly poured concrete is activated sequentially according to the construction sequence. Considering the actual pouring process of the sluice gate, the foundation slab is divided into one pouring layer based on the pouring process. During the calculation, the foundation slab elements are divided into several load steps according to the pouring sequence from the foundation to the top of the slab, and activated sequentially, and so on, until the top layer of the foundation slab is completed. During the calculation, as the foundation slab elements are gradually activated, the corresponding self-weight load and the temperature load of adjacent time steps calculated from the temperature field are also applied simultaneously. This allows for the simulation calculation of the temperature and stress fields of the foundation slab throughout the entire process from construction to operation.

[0163] To prevent dead elements from affecting the calculation convergence and the calculation results of active elements, in the temperature field analysis, the specific heat matrix and heat conduction matrix are multiplied by a factor, and the element heat flux is set to 0.

[0164] 2) Initial temperature conditions

[0165] At the instant the calculation begins, the temperature distribution within the concrete and foundation is one of the important boundary value conditions. Before pouring the base slab, a steady-state temperature field calculation is performed based on the surface temperature and the boundary ground temperature of the foundation. This result is used as the initial temperature of the foundation before the base slab is poured. The initial temperature of the newly poured base slab concrete is taken as the pouring temperature. The initial temperature at the interface between the newly poured concrete and the old concrete is the average value of the upper and lower layer nodes.

[0166] 3) Boundary conditions

[0167] The boundary of the foundation section is treated as an adiabatic boundary condition.

[0168] The boundary where the base slab is in contact with air is a type III boundary condition. During the pouring of the base slab, there are adjacent buildings rising roughly synchronously on the left and right sides. When the concrete is poured first, the side is a type III boundary condition; when it is poured simultaneously or later, it is an adiabatic boundary condition.

[0169] 4) Heat of hydration

[0170] The heat of hydration is applied to the concrete element in the form of volume force. In actual calculations, the difference in heat of hydration between two consecutive time steps is taken: . Based on engineering experimental data, a hyperbola was fitted. .

[0171] 5) Water pipe cooling

[0172] Using the equivalent heat conduction equation proposed by Academician Zhu Bofang, the cooling effect of water pipe cooling is regarded as the heat absorption of concrete, and the cooling effect of water pipe is considered in an average sense, with negative heat of hydration treatment.

[0173] 6) Mechanical properties of materials

[0174] In temperature stress calculations, the elastic modulus is a function that changes with time, and is fitted to an exponential form based on experimental data from actual engineering projects. Creep is a function of load holding time and loading age, and experimental data are fitted to an exponential function form proposed by Academician Zhu Bofang.

[0175] 7) Initial ground stress of the foundation

[0176] For the foundation, initial ground stress already exists in the foundation before pouring, which mainly consists of the long-term self-weight stress of the foundation. The initial stress in the shallow foundation layer is mainly due to its own weight. Strictly speaking, the initial ground stress field should be solved by simulating the evolution process of the foundation being continuously excavated downwards. However, this would be too complex to connect with the grid considering the later construction of the base plate. Considering the initial ground stress state, for the sake of simplicity, the stress generated by the foundation under its own weight is directly used as the initial ground stress.

[0177] 8) Temperature and Temperature Stress Simulation Calculation Process

[0178] Based on the above simulation technology processing steps, the simulation calculation process for temperature and temperature stress is as follows: Figure 1 As shown.

[0179] 4. Simulation Study on Temperature Control of Beixi Sluice Gate

[0180] 4.1 Calculation Model and Calculation Scheme

[0181] 4.1.1 Finite Element Model

[0182] This simulation uses Gate Pier No. 8 as the simulation object, and the calculation process considers the integral design. C35 normal concrete was selected for the calculation parameters. The three-dimensional calculation network diagram of the temperature and stress fields of Gate Pier No. 8 is shown in the figure, where the thickness below the foundation surface is taken as 20m, and the foundation range in the X direction is taken as 100 meters.

[0183] Finite element method coordinate system definition: X-axis: along the river; Y-axis: vertical; Z-axis: across the river;

[0184] 4.1.2 Calculation Scheme

[0185] The main research focuses on the dynamic changes in temperature and stress under insulation measures and non-curing conditions. The simulation results are as follows:

[0186] Condition 1: Thermal insulation without curing. Pouring will begin in December, with surface insulation measures adopted, and no first or second phase water cooling will be implemented.

[0187] 4.2 Simulation Calculation Results

[0188] For large-volume concrete projects like sluice gates, stress control is particularly important. The purpose of this application is to study the stress and temperature variation patterns of sluice gates under thermal insulation curing measures, and to propose corresponding temperature control measures. The table below shows the proposed pouring information, using the monthly average air temperature as the concrete pouring temperature, with the pouring layers symmetrically distributed on the left and right abutments.

[0189] surface - Typical casting simulation calculation of casting information table for each section

[0190]

[0191] 4.2.1 Simulation Results of Temperature and Stress Fields

[0192] Through simulation calculations, the temperature field and temperature stress field envelope diagrams of the sluice gate under the design temperature control conditions of insulation and non-maintenance were obtained. This application selects typical cross-sections and the whole for analysis.

[0193] Overall maximum temperature distribution pattern: From Figure 4 It can be seen that under the condition of heat preservation and non-curing, the highest temperature of the sluice gate is between 29.22 and 38.59℃. The highest temperature occurs on the left side of the third top pouring layer. The concrete pouring temperature in this part is high, the hydration temperature rises faster, the pouring layer is thicker, and the cooling effect is weaker, so the highest temperature is higher. The outer surface in contact with the foundation has a lower temperature because the heat dissipation is faster.

[0194] Distribution pattern of maximum temperature in sluice gate cross section: Figure 5 It can be seen that under the condition of insulation without curing, the highest temperature of the cross-section is between 28.08 and 38.70℃. The temperature is higher on the right and left sides of the middle of the sluice gate because the concrete is thicker and the heat dissipation is slower. The overall temperature pattern is high inside and low outside, high in the center and low at the edge, which is consistent with the general law of concrete temperature field.

[0195] Based on the above analysis and calculation of the temperature field, the stress field under this working condition was further simulated and obtained.

[0196] It can be seen that under operating condition one, the entire system is located in the tensile stress zone, with tensile stress values ​​ranging from 0 to 1.25 MPa. The tensile stress value at the surface is lower, with the lowest value being 0 MPa.

[0197] Distribution law of the maximum first principal stress in the cross section: by Figure 6 It can be seen that under working condition one, the entire cross-section is located in the tensile stress zone, with tensile stress values ​​ranging from 0 to 1.25 MPa. Due to the large size of the base plate and the influence of the structure, the maximum tensile stress of 1.25 MPa occurs on the lower surface of the base plate near the beam on both sides.

[0198] 4.2.2 Study on the Simulation Laws of Temperature and Stress

[0199] Figure 8 These are the temperature stress curves of the feature calculation nodes, with node number 1 being the internal node and node number 2 being the surface node.

[0200] The characteristic point temperature curve shows that the concrete temperature rises rapidly after pouring, reaches the first peak, then drops, and then briefly rebounds before fluctuating with changes in air temperature.

[0201] Due to the excessively high early temperature and rapid temperature drop of the concrete, the stress at the characteristic points is relatively high, especially at the internal characteristic point 1, where the maximum stress is approximately 1.15 MPa. According to the "Code for Design of Hydraulic Concrete Structures - Explanatory Notes", the temperature stress should be less than [a certain value]. The safety factor Kf ranges from 1.5 to 2.0, but since ε and Ec are independent of time t, they cannot be compared with the values ​​in this clause. In comparison, according to the explanatory notes of this clause, the product of stress and elastic modulus at t=28d can be used instead. Refer to similar concrete projects using C35 concrete. With a safety factor of 2.0, the calculated temperature stress should be less than 1.66 MPa. However, the maximum tensile stress in the calculation results is 1.25 MPa, which meets the requirements of the specification.

[0202] 4.3 Summary

[0203] Based on the results of temperature control simulation calculations, no temperature control measures other than surface insulation were adopted. The calculated results of temperature and stress in the sluice gate concrete both met the temperature control requirements of the specifications. From the temperature calculation results, the overall maximum temperature reached 38.70℃, and the temperature difference between the inside and outside of the concrete did not exceed the allowable 25℃ specified in the specifications. Furthermore, due to the excessive heat of hydration generated by the concrete, the early temperature peak was relatively high, but the maximum cooling rate at the characteristic point after pouring did not exceed the specification requirement of 2℃ / d. From the stress calculation results, due to the rapid temperature drop, the early tensile stress at the characteristic point increased rapidly, with a maximum value of 1.25MPa, which did not exceed the allowable tensile strength specified in the specifications (1.66MPa, safety factor 2.0).

Claims

1. A method for calculating and analyzing the temperature field and temperature stress field of a sluice gate, characterized in that, Includes the following steps: Step 1: Obtain basic data, including the climate conditions of the project area, the mechanical and thermal parameters of concrete and bedrock, the thermal insulation temperature rise data of materials, the equivalent heat release coefficient of the concrete surface insulation material, and the construction schedule. Step 2: Establish a three-dimensional finite element model. The three-dimensional finite element model simulates the actual shape and structure of the sluice gate. Define the coordinate system, select a typical gate pier as the simulation object, and determine the thickness below the foundation surface and the dimensions of the foundation range. Step 3: Set the calculation conditions, including: use the steady-state temperature field calculation result as the initial temperature of the foundation, take the initial temperature of the newly poured concrete as the pouring temperature, and take the average value of the upper and lower layer nodes as the initial temperature of the interface; treat the boundary of the foundation part as an adiabatic boundary condition, take the third type of boundary condition for the boundary between the sluice gate and the air, and take the third type of boundary condition or the adiabatic boundary condition for the side boundary according to the pouring sequence. Step 4: Using the three-dimensional transient finite element method, the construction pouring process, environmental climate change, artificial cooling and heat preservation measures, and the changes in the thermomechanical properties of materials over time are comprehensively considered. The heat of hydration is applied in the form of volume force and calculated according to the time step difference. Water pipe cooling is treated as equivalent to negative heat of hydration. Step 5: Perform temperature field simulation calculations for the entire process from construction to operation. Based on the principle of heat balance, derive the basic equation of solid heat conduction and solve the temperature distribution using the finite element governing equation. Step 6: Based on the temperature field calculation results, considering the creep characteristics of concrete, the equivalent elastic modulus is adopted, and the temperature stress field is simulated and calculated through stress increment calculation, equilibrium equation solution and element stress superposition. Step 7: Analyze the distribution and variation of the temperature field and temperature stress field to determine whether they meet the temperature control indicators and crack resistance safety requirements specified in the standards.

2. The method for calculating and analyzing the temperature field and temperature stress field of a sluice gate according to claim 1, characterized in that, The formula for calculating concrete creep, using an 8-parameter exponential function, is as follows: In the formula: Indicates time; Indicates the loading age; Indicates the loading age is , The degree of creep over time; This represents the creep parameter.

3. The method for calculating and analyzing the temperature field and temperature stress field of a sluice gate according to claim 1, characterized in that, The formula for the adiabatic temperature rise of concrete was obtained by fitting the experimental data with a hyperbolic curve. The hyperbolic formula used: 。 4. The method for calculating and analyzing the temperature field and temperature stress field of a sluice gate according to claim 1, characterized in that, The formula for calculating the equivalent heat transfer coefficient β of concrete surface insulation materials is as follows: Where: h i Indicates the thickness of the insulation material; Indicates the thermal conductivity of the insulation material; This indicates the heat dissipation coefficient of the concrete surface without insulation. This represents the wind speed correction factor; This indicates a correction factor for humidity levels.

5. The method for calculating and analyzing the temperature field and temperature stress field of a sluice gate according to claim 1, characterized in that, The coordinate system of the three-dimensional finite element model is defined as follows: X-axis along the river, Y-axis vertical, and Z-axis transverse to the river. To simulate the pouring process, the elements are activated in stages according to the order from the foundation to the top of the slab, and the self-weight load and temperature load are applied simultaneously.

6. The method for calculating and analyzing the temperature field and temperature stress field of a sluice gate according to claim 1, characterized in that, Boundary conditions for temperature field calculations include first-type boundary conditions. Second type of boundary conditions Third type of boundary conditions h is the surface convection coefficient, T0 is the ambient temperature, and the temperature at any point within the element is obtained by interpolation using the element shape function. The finite element governing equation is derived based on the variational principle. .

7. The method for calculating and analyzing the temperature field and temperature stress field of a sluice gate according to claim 1, characterized in that, In step 4, based on the principle of heat balance, the three-dimensional transient finite element method is used to solve the heat conduction equation: In the formula , , ; , , Thermal conductivity , , Thermal conductivity, For the specific heat of the material, For the material's density, , Describe the time and temperature respectively.

8. The method for calculating and analyzing the temperature field and temperature stress field of a sluice gate according to claim 1, characterized in that, In step (6), the formula for calculating concrete strain is: ,exist The formula for calculating the internal stress increment is: The equivalent elastic modulus The element stress is the sum of the stress increments at each time period.

9. The method for calculating and analyzing the temperature field and temperature stress field of a sluice gate according to claim 1, characterized in that, In step (6), the temperature stress balance equation is: The increase in nodal loads caused by external loads is ignored in the calculation. Increase in nodal load caused by drying shrinkage .

10. A system for calculating and analyzing the temperature field and temperature stress field of a sluice gate, comprising a processor, a memory, and a bus, wherein the memory stores machine-readable instructions executed by the processor; characterized in that, When the system is running, the processor and the memory communicate via a bus, and the machine-readable instructions are executed by the processor as described in any one of claims 1 to 9.

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