Cable tower creeping formwork construction temperature field analog simulation method

Abstract

The invention relates to a cable bent tower creeping formwork construction temperature field simulation method, which comprises the following steps: S1, determining thermal parameters and a hydration adiabatic temperature rise curve of cable bent tower concrete, and establishing a concrete heat transfer and cement hydration heat release model; s2, determining a boundary condition of a convective heat transfer coefficient on the surface of the cable bent tower; s3, determining a solar radiation boundary condition; s4, carrying out multiple working condition division on the cable bent tower temperature field; and S5, using Abaqus software to carry out temperature field finite element analysis under complex temperature boundary conditions and concrete hydration effects on each working condition of cable tower creeping formwork construction. According to the method, concrete hydration heat release, convective heat transfer and solar radiation in the layered pouring process of the cable bent tower are considered, the influence of the actual construction process is considered by setting corresponding working conditions, and the problem that an accurate temperature field in the cable bent tower construction process cannot be obtained due to neglecting of the comprehensive influence of the construction process and environmental factors in an existing analysis method is solved; and the temperature field distribution of the cable bent tower structure in the construction process can be truly reflected.

Description

Technical Field

[0001] The invention belongs to the technical field of bridge simulation, and in particular relates to a temperature field simulation method for cable tower climbing formwork construction. Background Art

[0002] The cable tower of a cable-stayed bridge is an important component that provides elastic support to the main beam through cables. It is under a complex stress state due to its own gravity, cable force, and bending moment for a long time. In addition, due to exposure to the environment, it is often subjected to loads caused by temperature changes, wind speed changes, changes in sunlight conditions, etc. Due to the poor thermal conductivity of concrete structures, these changes in environmental factors often cause a large temperature gradient inside the concrete, which often produces large temperature stresses under the influence of constraints and deformations. In severe cases, cracks may even occur. Once cracks appear, the safety and durability of the bridge will be seriously affected.

[0003] The tower's pedestal, tower base and tower column are all large-volume concrete construction. As the fineness of contemporary cement is generally low, the hydration heat is high, and the hydration heat release rate is fast, the concrete releases a lot of hydration heat in a short period of time, and it is more difficult for large-volume concrete to dissipate heat. The heat accumulation is not easy to release, resulting in excessively high temperatures inside the large-volume concrete. The hydration heat accumulates inside the concrete, forming a large internal and external temperature rise and temperature difference, and the resulting temperature stress causes cracks in the large-volume concrete. The problem of tower column construction is more complicated, because the tower wall thickness is generally greater than 1.5m, which is also a large-volume concrete structure. Due to the dense arrangement of tower column steel bars, it is more difficult to vibrate during high-altitude operations, which requires the poured concrete to have better flow properties and self-compacting ability. Therefore, more gel materials are used in the tower column concrete, which further aggravates the release of concrete hydration heat, resulting in further increases in structural temperature rise and internal and external temperature differences, and more prominent risks of temperature cracking, resulting in cracking.

[0004] The temperature field change of the cable tower during the climbing formwork construction process mainly depends on two factors: the heat release of concrete hydration and the heat exchange with the external environment. In order to more accurately simulate the heat release of concrete hydration and the thermal boundary conditions of the cable tower, the actual concrete temperature rise curve is determined in combination with actual engineering data. The CFD method is used to calculate the actual wind speed distribution on the surface of the cable tower at different heights, and the wind speed and convection coefficient corresponding to the thickness of the thermal boundary layer are obtained. It is particularly necessary to adjust the solar radiation according to longitude and latitude, day number, etc.

[0005] At the same time, in order to consider that different climbing formwork construction sections will also affect each other's temperature field due to different temperature distributions, the actual construction conditions and construction process of the cable tower are combined with the concrete temperature field analysis. Most of the existing cable tower temperature field analysis methods are to conduct a coupling analysis of a static segment of concrete, or to calculate the stress distribution of the cable tower climbing formwork construction process under the action of gravity load without considering environmental factors. It is difficult to obtain the temperature field distribution of the cable tower during the actual construction pouring process.

[0006] In order to simulate the temperature field during the whole process of cable tower climbing formwork construction, it is very important to adopt a numerical simulation method of cable tower temperature field that comprehensively considers cement hydration, solar radiation, convective heat transfer and construction progress. Summary of the invention

[0007] The purpose of the present invention is to overcome the shortcomings of the prior art and provide a method for simulating the temperature field of a cable tower climbing formwork construction, which comprehensively considers the construction process, hydration heat release and complex thermal boundary conditions, and solves the problem that the existing analysis method cannot obtain the accurate temperature field during the cable tower construction process.

[0008] The present invention solves the technical problem by the following technical solutions:

[0009] A method for simulating temperature field of cable tower climbing formwork construction, the method comprising the following steps:

[0010] S1. Determine the thermal parameters of the cable tower concrete based on the concrete material properties and engineering data, determine the hydration adiabatic temperature rise curve of the cable tower concrete in combination with the specification "Standard for Construction of Mass Concrete", and establish the concrete heat transfer and cement hydration heat release model;

[0011] S2. According to the meteorological conditions of the construction site, including wind speed and ambient temperature distribution, the wind speed distribution on the tower surface is obtained, and the boundary conditions of the convective heat transfer coefficient on the tower surface are determined;

[0012] S3. Calculate the solar radiation intensity including direct solar radiation, scattered radiation and atmospheric back radiation according to the longitude and latitude of the construction area, the day number and temperature at the calculation time, and determine the solar radiation boundary conditions;

[0013] S4. According to the climbing formwork construction sections divided by the climbing formwork construction, the temperature field of the cable tower is divided into multiple working conditions;

[0014] S5. Use Abaqus software to perform finite element analysis on the complex temperature boundary conditions and temperature field under the action of concrete hydration for each working condition of the cable tower climbing formwork construction.

[0015] Moreover, the thermal parameters of the concrete in S1 include thermal conductivity k and specific heat c. The thermal parameters are input as material properties for finite element analysis. The hydration adiabatic temperature rise curve equation is:

[0016]

[0017] Where: T(t) is the adiabatic temperature rise of concrete at age t, W is the amount of cementitious material per cubic meter of concrete, C is the specific heat capacity of concrete, ρ is the mass density of concrete, t is the age of concrete, and m is the empirical coefficient.

[0018] Moreover, the temperature daily variation of S2 according to the construction location is:

[0019]

[0020] in: is the daily average temperature, is the daily temperature variation; T amax , T amin are the daily maximum temperature and the daily minimum temperature respectively; t0 is the time parameter used to indicate the occurrence of the maximum temperature and the minimum temperature;

[0021] For wind speeds at different heights, according to the Code for Loads on Building Structures, the relationship between the actual height and the standard height wind speed is:

[0022]

[0023] Where: z is the actual height, v is the wind speed at the actual height, v z is the wind speed at the standard height, a is the bottom surface roughness index;

[0024] In order to obtain accurate wind speed distribution on the tower surface, the surface wind field is calculated based on the CFD method, and a CFD numerical model is established to solve the mass, momentum and energy conservation equations of the heat exchange process between air and concrete wall:

[0025]

[0026] Where: ρ is the air density, u and v are the velocity vectors in the global coordinates, μ is the air viscosity coefficient, S x With S y is the external force applied to the fluid particles, T represents the temperature, k and c p is the thermal diffusivity and specific heat capacity of the material;

[0027] According to CFD simulation, the local wind field around the outer surface of the tower under uniform flow wind speed is obtained, the wind speed v on the tower surface is calculated, and then the convective heat transfer coefficient on the tower surface is obtained:

[0028]

[0029] Where: ΔT represents the temperature difference between the structure surface and the surrounding air, and v represents the wind speed on the tower surface.

[0030] Moreover, in S3, the solar constant is expressed as the solar radiation intensity at the upper boundary of the atmosphere perpendicular to the solar radiation surface, represented by I0, and is taken according to the following formula:

[0031]

[0032] Where: D is the date serial number of the day in the year, starting from the New Year's Day of the year, D = 81;

[0033] The angle between the sun's rays and the horizon is called the solar altitude angle, and the angle between the sun's rays' projection on the horizon and the local meridian is called the solar azimuth angle. The solar azimuth angle is zero in the south direction, negative from south to east and north, and positive from south to west and north.

[0034] To calculate the solar radiation, we must first determine the solar azimuth angle ψ of the region at different seasons and times. s and the altitude angle h s , calculated using the following formula:

[0035] sinhh s =sinφsinδ+cosδsinφcosω

[0036]

[0037] Among them: δ represents the solar declination, φ represents the latitude of the area, ω represents the hour angle, the hour angle is 0 at noon, negative before noon, positive after noon, and changes by 15° every hour, that is, ω = 15;

[0038] Solar declination is a parameter related to the seasons. If the cycle is one year, the solar declination on the summer solstice is +23.5°, and the solar declination on the vernal equinox and autumnal equinox is zero. The COOPER equation is used to approximate the solar declination δ that changes continuously throughout the year, that is,

[0039]

[0040] D is the date serial number of the day in the year, counting from New Year's Day of the year;

[0041] Solar radiation includes direct solar radiation and diffuse solar radiation. The solar radiation intensity I perpendicular to the sun's rays is calculated. m When , the direct solar radiation calculation formula is as follows:

[0042]

[0043] in: is the total transmission coefficient of direct sunlight; q a mis the absorption coefficient of direct sunlight in water vapor, oxygen, aerosol and ozone; q σ m is the scattering coefficient of direct sunlight in pure atmospheric molecules; q δ m is the scattering coefficient of direct sunlight in aerosol,

[0044] The direct solar radiation intensity I projected directly onto the inclined surface is calculated using the following formula a :

[0045] I a =I m cosi

[0046] Among them: α is the inclination angle of the inclined plane, m is the distance of the light, and i is the projection angle of the sun's light on the inclined plane, which is the angle between the sun's radiation and the outer normal of the inclined plane;

[0047]

[0048] in: is the geographical latitude of the location, ω is the hour angle, ω=15t, t is the local solar time, the time when the sun passes the meridian at noon is zero hour, the afternoon is positive, and the morning is negative; ψ n The azimuth of the slope normal is zero towards the south, positive towards the west, and negative towards the east; δ is the solar latitude, h s is the solar angular altitude;

[0049] The intensity of solar scattered radiation on a sunny horizontal surface can be calculated using the Berlage formula:

[0050]

[0051] The scattered radiation intensity on any wall of the structure is:

[0052]

[0053] A simplified formula can also be used:

[0054]

[0055] Where: I0 is the solar constant, h s is the solar angular height, P2 is the atmospheric transparency, and ln is the natural logarithm.

[0056] Moreover, the boundary heat transfer conditions include the convective heat transfer under the ambient wind speed and temperature and the solar radiation. There are three types of temperature boundary conditions: the first type of boundary condition is that the temperature function on the object boundary is known; the second type of boundary condition is that the heat flux density q (W / m 2) is known; the third type of boundary condition means that the temperature and heat transfer coefficient h of the fluid medium in contact with the object are known, and convection heat transfer and solar radiation are the third type of boundary conditions, which can be expressed by the formula:

[0057]

[0058] Where: h is the convective heat transfer coefficient; T is the solid temperature; T f is the temperature of the fluid surrounding the solid.

[0059] Furthermore, in S6, the birth and death unit of the finite element analysis software Abaqus is used to realize the sequential pouring of corresponding working conditions, and the concrete hydration heat release and thermal boundary conditions of the corresponding working condition time are applied to the tower column concrete poured in different time periods in combination with the subroutine.

[0060] The advantages and beneficial effects of the present invention are:

[0061] 1. The present invention takes into account the deficiencies of existing numerical simulation methods for the temperature field during cable tower construction, takes into account the heat release of concrete hydration during the layered pouring of the cable tower, the convective heat transfer and solar radiation caused by environmental factors during the construction of the cable tower, and establishes corresponding working conditions to consider the impact of the actual construction process. It provides a numerical simulation method for the temperature field during the cable tower construction process that comprehensively considers the construction process, hydration heat release and complex thermal boundary conditions, solves the problem that the existing analysis method cannot obtain an accurate temperature field during the cable tower construction process due to ignoring the comprehensive impact of the construction process and environmental factors, and can truly reflect the temperature field distribution of the cable tower structure during the construction process.

[0062] 2. The present invention can determine the complex boundary conditions in the cable tower construction process under the influence of various environmental factors including wind speed, solar radiation, ambient temperature, etc., calculate the temperature field of the cable tower under the action of construction process, complex temperature boundary and hydration heat, and analyze the temperature distribution law of the cable tower during the construction process, which has guiding significance for similar construction processes. BRIEF DESCRIPTION OF THE DRAWINGS

[0063] Figure 1 It is a flow chart of the present invention.

[0064] Figure 2 A schematic diagram of the thermal environment to which the structure of the present invention is subjected;

[0065] Figure 3 This is the CFD simulation wind field diagram of the present invention;

[0066] Figure 4 It is a section diagram of the cable tower construction stage of the present invention;

[0067] Figure 5 A grid diagram of a cable tower entity model of the present invention;

[0068] Figure 6 It is the temperature field diagram inside the tower column of the present invention;

[0069] Figure 7 It is a time history curve diagram of the central temperature of the hydration heat accumulation part of the present invention;

[0070] Figure 8 It is the surface temperature field diagram of the cable tower of the present invention;

[0071] Fig. 9 It is a temperature difference time course curve diagram of the present invention facing the sun and facing the shade;

[0072] Fig.10 It is a temperature time history curve diagram of different points under the influence of mutual shielding of the present invention. DETAILED DESCRIPTION

[0073] The present invention is further described in detail below through specific examples. The following examples are only illustrative and not restrictive, and the protection scope of the present invention cannot be limited thereto.

[0074] like Figure 1 As shown, a method for simulating the temperature field of a cable tower climbing formwork construction is innovative in that the method comprises the following steps:

[0075] S1. Determine the thermal parameters of the cable tower concrete based on the concrete material properties and engineering data, determine the hydration adiabatic temperature rise curve of the cable tower concrete in combination with the specification "Standard for Construction of Mass Concrete", and establish the concrete heat transfer and cement hydration heat release model;

[0076] S2. According to the meteorological conditions of the construction site, including wind speed and ambient temperature distribution, the wind speed distribution on the tower surface is obtained, and the boundary conditions of the convective heat transfer coefficient on the tower surface are determined;

[0077] S3. Calculate the solar radiation intensity including direct solar radiation, scattered radiation and atmospheric back radiation according to the longitude and latitude of the construction area, the day number and temperature at the calculation time, and determine the solar radiation boundary conditions;

[0078] S4. According to the climbing formwork construction sections divided by the climbing formwork construction, the temperature field of the cable tower is divided into multiple working conditions;

[0079] S5. Use Abaqus software to perform finite element analysis on the complex temperature boundary conditions and temperature field under the action of concrete hydration for each working condition of the cable tower climbing formwork construction.

[0080] Taking the expansion project of the Jinan Yellow River Highway Bridge on the G104 Beijing-Lanzhou Line as the background, this method is used to analyze the tower climbing formwork construction. The specific implementation example is as follows:

[0081] 1. Establish concrete hydration heat release model

[0082] According to the relevant material properties of concrete and engineering data, the thermal parameters of concrete are determined, including thermal conductivity k, specific heat c, etc. The thermal conductivity k is taken as 9180J / (m·h·℃) and the specific heat capacity is taken as 830J / (kg·℃). As the material property input for subsequent finite element analysis, the adiabatic temperature rise equation of concrete has many forms, including exponential, hyperbolic and composite exponential. According to the "Standards for Construction of Mass Concrete", the exponential adiabatic temperature rise curve is selected:

[0083] T(t)=WQ / Cρ(1-e -mt )

[0084] Where: T(t) is the adiabatic temperature rise of concrete at age t, W is the amount of cementitious material per cubic meter of concrete, C is the specific heat capacity of concrete, ρ is the mass density of concrete, t is the age of concrete, and m is the empirical coefficient.

[0085] The final temperature rise curve is:

[0086] T(t)=40.39(1-e -0.015t )

[0087] 2. Determine the thermal boundary conditions according to local climate conditions. The thermal environment to which the structure is subjected mainly includes environmental convection heat transfer and solar radiation, such as Figure 2 As shown:

[0088] (1) Determine the daily change of ambient temperature

[0089] T a (t) = T av +T am sin(t-t0)π / 12

[0090] in: is the daily average temperature, is the daily temperature variation; T amax , T amin are the daily maximum temperature and daily minimum temperature respectively; t0 is the time parameter used to indicate the occurrence of the maximum temperature and the minimum temperature.

[0091] (2) Determine the wind speed at different heights of the structure according to the Code for Loads on Building Structures:

[0092] v=v z (z / 10) a

[0093] Where: z is the actual height, v is the wind speed at the actual height, v z is the wind speed at the standard height, and a is the bottom surface roughness index.

[0094] (3) Calculate the surface wind field based on the CFD method, select the two-dimensional cross section at the representative position of the tower, and use Fluent software to establish a CFD numerical model, such as Figure 3 , solve the wind speed distribution of air on the concrete wall under the action of the wind field. According to the wind speed and temperature distribution, the convective heat transfer coefficient of the tower surface is obtained:

[0095]

[0096] Where: ΔT represents the temperature difference between the structure surface and the surrounding air, and v represents the surface wind speed.

[0097] (4) Determine the direct solar radiation intensity I on the structure surface a , first calculate the solar constant I0:

[0098] I0=1353+44sin(2π(89+D) / 365)W / m 2

[0099] Wherein: D is the date serial number of the day in the year, counting from the New Year's Day of the year, for example, the Spring Equinox (March 21), D=81.

[0100] Then calculate the angle between the projection of the sun's rays on the horizon and the local meridian, that is, the solar azimuth. First, it is necessary to determine the solar azimuth ψ in the area at different seasons and times. s and the altitude angle h s :

[0101] sinhh s =sinφsinδ+cosδsinφcosω

[0102] sinψ s =cosδsinω / cosh s

[0103] Among them: δ represents the solar declination, φ represents the latitude of the area, and ω represents the hour angle (the hour angle is 0 at noon, negative before noon, positive after noon, and changes by 15° every hour, that is, ω=15)

[0104] The solar declination is a parameter related to the seasons. If the cycle is one year, the solar declination on the summer solstice is +23.5°, and the solar declination on the spring and autumn equinoxes is zero. The COOPER equation can be used to approximate the solar declination δ that changes throughout the year, that is,

[0105] δ=23.45sin(2π(365+D) / 365.25)

[0106] D is the date serial number of the day in the year, counting from New Year's Day of that year.

[0107] Then calculate the direct solar radiation intensity I perpendicular to the sun's rays m :

[0108]

[0109] in: is the total transmission coefficient of direct sunlight; q a m is the absorption coefficient of direct sunlight in water vapor, oxygen, aerosol and ozone; q σ m is the scattering coefficient of direct sunlight in pure atmospheric molecules;

[0110] q δ m is the scattering coefficient of direct sunlight in aerosol.

[0111] Finally, the direct solar radiation intensity I projected directly onto the inclined surface is calculated a :

[0112] I α =I m cosi

[0113] Among them: α is the inclination angle of the inclined plane, m is the distance of the light, and i is the projection angle of the sun's light on the inclined plane, which is the angle between the sun's radiation and the outer normal of the inclined plane;

[0114]

[0115] in: is the geographical latitude of the location, ω is the hour angle, ω=15t, t is the local solar time, the time when the sun passes the meridian at noon is zero hour, the afternoon is positive, and the morning is negative; ψ n The azimuth of the slope normal is zero towards the south, positive towards the west, and negative towards the east; δ is the solar latitude, h s is the solar angular altitude, which can be calculated using the formula mentioned above.

[0116] (5) Use the Berlage formula to calculate the intensity of solar scattered radiation on a horizontal surface on a sunny day:

[0117]

[0118] The scattered radiation intensity on any wall of the structure is:

[0119]

[0120] A simplified formula can also be used:

[0121]

[0122] Where I0 is the solar constant, h s is the solar angular height, P2 is the atmospheric transparency, and ln is the natural

[0123] number

[0124] 3. According to steps S1, S2, and S3, set up the corresponding material properties and boundary conditions in Abaqus.

[0125] The thermal material properties of concrete are input through the column of material properties-user material (thermal) in the software, which is associated with the use of the subsequent UMATHT subroutine. The UMATHT subroutine is used to realize the concrete hydration temperature rise curve obtained in step S1, define the changing internal energy in each analysis step, and realize the heat release of concrete itself in the Abaqus software; the structural thermal boundary conditions are set in the software interaction. By setting the user-defined option in the surface heat exchange condition, the FILM subroutine is referenced, and the corresponding temperature daily change and convective heat transfer coefficient in step S2 are defined in the subroutine as functions related to temperature and wind speed, thereby realizing convective heat transfer under the influence of the environment; by setting the user-defined option of surface radiation in the interaction, the DFLUX subroutine is referenced, and the relationship between the day number and the solar azimuth angle equal to the software calculation time is defined in the subroutine, and the relationship between direct solar radiation, indirect solar radiation and solar scattering in step S3 is used to realize the addition of solar radiation. The above content is used as the analysis framework of the concrete temperature field in each step.

[0126] 4. According to the construction organization design of the cable tower cap and tower column, the cap will be poured twice, each pouring height is 3m, the tower column is divided into 32 sections including the tower crown, and the lower tower column is poured in 7 sections (including the beam). The first section is 3.5 meters in layer for the convenience of inner membrane construction, the second section is 5.025 meters in layer, the third section is 5.365 meters in layer for the bottom of the corbel, the fourth section is 4.268 meters in layer, the 5-6 sections are 4.8 meters in layer, the 7th section is divided into a layer for casting the beam separately, and the layer is 6.592 meters. The horizontal bridge is used for the straight template connection height; the 8th section of the middle tower column is considered to be an arc template. The slab layer is 4.666 meters. Considering that there will be non-standard layers in the 9th section when constructing the middle and upper tower columns, in order to reduce the difficulty of adjusting the embedded parts of the frame, the non-standard layers are placed at the lower mouth, and the layer is 1.98 meters. The standard vertical casting height of the 9th to 17th sections of the middle tower column is 5.8 meters, the 18th section is 4.96 meters, the 19th section is 3.512 meters, the 20th to 23rd sections are 5.8 meters, the 24th to 31st sections are 5.2 meters, and the 32nd section is 4.932 meters. The template of the curved section of the 19th to 26th sections of the upper tower column is constructed with a straight template, and a hydraulic climbing template is used for construction. Figure 3 A total of 34 working conditions were set up, including CT1 (first pouring of the foundation), CT2, PM1 (first pouring of the climbing formwork) - PM32.

[0127] 5. Establish the corresponding tower solid model in Abaqus and divide the corresponding climbing formwork sections into segments, such as Figure 5 . Based on the simulation of the layered construction process of the cable tower in the above step, the temperature field analysis of the concrete of different sections of the cable tower is carried out in turn. The total number of units is 7262, and the DC3D8 heat transfer analysis unit is used. Using the life and death unit function in Abaqus, the cable tower is "killed" as a whole at the beginning of the calculation, and the units are "activated" in turn in the subsequent analysis steps to achieve the simulation effect of layered pouring. Combined with the content of step S4, the temperature field analysis of each section of layered concrete pouring is carried out, so that while obtaining the changes in the temperature field of each section of concrete, the different effects of the different ages of concrete in different sections are considered to obtain the overall temperature field of the cable tower, reflecting the temperature distribution during the construction process of the cable tower.

[0128] The present invention analyzes the temperature field of the cable tower during the construction process, and the temperature field distribution inside the cable tower column under the influence of hydration heat is as follows: Figure 6 It can be seen that due to the large volume of concrete in the cable tower segment and the violent hydration reaction, the hydration heat inside the concrete cannot be transferred outward in time after pouring, resulting in a large amount of hydration heat accumulation in some construction sections of the cable tower, the internal temperature continues to rise, and the temperature difference between the inside and the outside increases. The temperature field at the center of the hydration heat accumulation part is analyzed, such as Figure 7 When the mold entry temperature is 10°C, the maximum temperature of the area where hydration heat accumulates is lower than 65°C, and the adiabatic temperature rise is less than 50°C, which meets the requirements of the Technical Specification for Temperature Measurement and Control of Mass Concrete (GBT51028-2015).

[0129] Under the analysis method of the present invention, the surface temperature field of the tower is non-uniform, such as Figure 8 Select Figure 8 Draw the temperature difference time curve for the two points P1 and P2 on the sunny side and shady side of the lower tower column, as shown in Fig. 9 The north shady side of the cable tower is in a self-shading state for a long time, and the temperature is lower than the south sunny side. During the construction of the cable tower, the solar azimuth changes, and the difference in solar radiation between the north and south sides also changes. The temperature difference can reach up to 9°C. The temperature difference between the sunny side and the shady side will cause the cable tower to move along the bridge during the construction process, affecting the construction line shape. Figure 8 The temperature-time curves of the three points P3, P4 and P5 are plotted as follows: Fig.10As shown. 240h after pouring, P3, P4 and P5 were shielded by the lower beam, and the temperature dropped at the same time. About 300h, 470h and 620h after pouring, P3, P4 and P5 were successively out of the shielding state, and the temperature rose. About 4070h, 4230h and 4500h after pouring, P5, P4 and P3 were shielded by the middle tower column, and the temperature dropped. The maximum temperature difference between the three points can reach 7°C. The temperatures of the three points are almost the same in the rest of the time period. It can be seen that with the progress of construction, the surface non-uniform temperature field caused by mutual shielding changes.

[0130] In summary, the present invention takes into account the deficiencies of existing numerical simulation methods for the temperature field during cable tower construction, considers the heat release of concrete hydration during the layered pouring of the cable tower, the convective heat transfer and solar radiation caused by environmental factors during the construction of the cable tower, and establishes corresponding working conditions to consider the impact of the actual construction process. A numerical simulation method for the temperature field during the cable tower construction process is provided, which comprehensively considers the construction process, hydration heat release and complex thermal boundary conditions. The method solves the problem that the existing analysis method cannot obtain the accurate temperature field during the cable tower construction process due to ignoring the comprehensive impact of the construction process and environmental factors, and can truly reflect the temperature field distribution of the cable tower structure during the construction process.

[0131] Although the embodiments and drawings of the present invention are disclosed for illustrative purposes, those skilled in the art will appreciate that various substitutions, changes and modifications are possible without departing from the spirit and scope of the present invention and the appended claims. Therefore, the scope of the present invention is not limited to the contents disclosed in the embodiments and drawings.

Claims

1. A method for simulating the temperature field of a cable tower climbing formwork construction, characterized in that: The steps of the method are: S1. Determine the thermal parameters of the cable tower concrete based on the concrete material properties and engineering data, determine the hydration adiabatic temperature rise curve of the cable tower concrete in combination with the specification "Standard for Construction of Mass Concrete", and establish the concrete heat transfer and cement hydration heat release model; S2. According to the meteorological conditions of the construction site, including wind speed and ambient temperature distribution, the wind speed distribution on the tower surface is obtained, and the boundary conditions of the convective heat transfer coefficient on the tower surface are determined; S3. Calculate the solar radiation intensity including direct solar radiation, scattered radiation and atmospheric back radiation according to the longitude and latitude of the construction area, the day number and temperature at the calculation time, and determine the solar radiation boundary conditions; S4. According to the climbing formwork construction sections divided by the climbing formwork construction, the temperature field of the cable tower is divided into multiple working conditions; S5. Use Abaqus software to perform finite element analysis on the complex temperature boundary conditions and temperature field under the action of concrete hydration for each working condition of the cable tower climbing formwork construction.

2. The method for simulating temperature field of cable tower climbing formwork construction according to claim 1 is characterized in that: The thermal parameters of the concrete in S1 include thermal conductivity k and specific heat c. The thermal parameters are input as material properties for finite element analysis. The hydration adiabatic temperature rise curve equation is: Where: T(t) is the adiabatic temperature rise of concrete at age t, W is the amount of cementitious material per cubic meter of concrete, C is the specific heat capacity of concrete, ρ is the mass density of concrete, t is the age of concrete, and m is the empirical coefficient.

3. The method for simulating temperature field of cable tower climbing formwork construction according to claim 1 is characterized in that: The temperature daily variation of S2 according to the construction location is: in: is the daily average temperature, is the daily temperature variation; T amax , T amin are the daily maximum temperature and the daily minimum temperature respectively; t0 is the time parameter used to indicate the occurrence of the maximum temperature and the minimum temperature; For wind speeds at different heights, according to the Code for Loads on Building Structures, the relationship between the actual height and the standard height wind speed is: Where: z is the actual height, v is the wind speed at the actual height, v z is the wind speed at the standard height, a is the bottom surface roughness index; In order to obtain accurate wind speed distribution on the tower surface, the surface wind field is calculated based on the CFD method, and a CFD numerical model is established to solve the mass, momentum and energy conservation equations of the heat exchange process between air and concrete wall: Where: ρ is the air density, u and v are the velocity vectors in the global coordinates, μ is the air viscosity coefficient, S x With S y is the external force applied to the fluid particles, T represents the temperature, k and c p is the thermal diffusivity and specific heat capacity of the material; According to CFD simulation, the local wind field around the outer surface of the tower under uniform flow wind speed is obtained, the wind speed v on the tower surface is calculated, and then the convective heat transfer coefficient on the tower surface is obtained: Where: ΔT represents the temperature difference between the structure surface and the surrounding air, and v represents the wind speed on the tower surface.

4. The method for simulating temperature field of cable tower climbing formwork construction according to claim 1 is characterized in that: In S3, the solar constant is expressed as the solar radiation intensity at the upper boundary of the atmosphere perpendicular to the solar radiation surface, represented by I0, and is taken according to the following formula: Where: D is the date serial number of the day in the year, starting from the New Year's Day of the year, D = 81; The angle between the sun's rays and the horizon is called the solar altitude angle, and the angle between the sun's rays' projection on the horizon and the local meridian is called the solar azimuth angle. The solar azimuth angle is zero in the south direction, negative from south to east and north, and positive from south to west and north. To calculate the solar radiation, we must first determine the solar azimuth angle ψ of the region at different seasons and times. s and the altitude angle h s , calculated using the following formula: sinhh s =sinφsinδ+cosδsinφcosω Among them: δ represents the solar declination, φ represents the latitude of the area, ω represents the hour angle, the hour angle is 0 at noon, negative before noon, positive after noon, and changes by 15° every hour, that is, ω = 15; Solar declination is a parameter related to the seasons. If the period is one year, the solar declination on the summer solstice is +23.5°, and the solar declination on the vernal equinox and autumnal equinox is zero. The COOPER equation is used to approximate the solar declination δ that changes continuously throughout the year, that is, D is the date serial number of the day in the year, counting from New Year's Day of the year; Solar radiation includes direct solar radiation and diffuse solar radiation. The solar radiation intensity I perpendicular to the sun's rays is calculated. m When , the direct solar radiation calculation formula is as follows: in: is the total transmission coefficient of direct sunlight; q a m is the absorption coefficient of direct sunlight in water vapor, oxygen, aerosol and ozone; q σ m is the scattering coefficient of direct sunlight in pure atmospheric molecules; q δ m is the scattering coefficient of direct sunlight in aerosol, The direct solar radiation intensity I projected directly onto the inclined surface is calculated using the following formula a : I=I cosi 2. Among them: α is the inclination angle of the inclined plane, m is the distance of the light, and i is the projection angle of the sun's light on the inclined plane, which is the angle between the sun's radiation and the outer normal of the inclined plane; in: is the geographical latitude of the location, ω is the hour angle, ω=15t, t is the local solar time, the time when the sun passes the meridian at noon is zero hour, the afternoon is positive, and the morning is negative; ψ n The azimuth of the slope normal is zero towards the south, positive towards the west, and negative towards the east; δ is the solar latitude, h s is the solar angular altitude; The intensity of solar scattered radiation on a sunny horizontal surface can be calculated using the Berlage formula: The scattered radiation intensity on any wall of the structure is: A simplified formula can also be used: Where: I0 is the solar constant, h s is the solar angular height, P2 is the atmospheric transparency, and ln is the natural logarithm.

5. The method for simulating temperature field of cable tower climbing formwork construction according to claim 1 is characterized in that: Boundary heat transfer conditions include convective heat transfer under ambient wind speed and temperature and solar radiation. There are three types of temperature boundary conditions: the first type of boundary condition is that the temperature function on the object boundary is known; the second type of boundary condition is that the heat flux density q on the object boundary is known; the third type of boundary condition refers to the temperature and heat transfer coefficient h of the fluid medium in contact with the object are known. Convective heat transfer and solar radiation are the third type of boundary conditions, which are expressed by the formula: Where: h is the convective heat transfer coefficient; T is the solid temperature; T f is the temperature of the fluid surrounding the solid.

6. The method for simulating temperature field of cable tower climbing formwork construction according to claim 1 is characterized in that: In the S6, the birth and death unit of the finite element analysis software Abaqus is used to realize the sequential pouring of the corresponding working conditions, and the concrete hydration heat release and thermal boundary conditions of the corresponding working condition time are applied to the tower column concrete poured in different time periods in combination with the subroutine.

Images