Method for establishing temperature control standards for large-volume thin-walled concrete structures

Abstract

The present invention discloses a method for formulating temperature control standards for large-volume thin-walled concrete structures, the method comprising: obtaining thermal parameters, mechanical parameters and geometric features of the thin-walled concrete structure; constructing a numerical simulation model of the thin-walled concrete structure based on the geometric features; obtaining the temperature process line and stress process line of the thin-walled concrete structure in different seasons based on the numerical simulation model and based on the thermal parameters and mechanical parameters, and back-calculating to determine the foundation temperature difference value and the temperature difference between new and old concrete. The present invention can formulate a more reasonable foundation temperature difference, upper and lower layer temperature difference, and internal and external temperature difference, so as to formulate corresponding temperature control measures for the temperature control mark and prevent the generation of temperature cracks in large-volume thin-walled concrete structures.

Description

Technical Field

[0001] The invention relates to the technical field of crack prevention of thin-walled concrete structures, and in particular to a method for formulating temperature control standards for large-volume thin-walled concrete structures. Background Art

[0002] Large-volume concrete structures such as pump stations and ship locks are thin-walled concrete, which has the basic characteristics of large-volume concrete structures, namely, obvious brittle characteristics, and the temperature stress generated by the rapid internal temperature rise can easily cause cracks in the concrete structure. Therefore, it is necessary to formulate temperature control standards and temperature control measures during the pouring of large-volume thin-walled concrete to prevent the occurrence of temperature cracks in large-volume thin-walled concrete structures. However, since thin-walled structures usually have a large exposed surface and a small distance between the center and the surface in a certain direction, the internal temperature of the thin-walled structure will fluctuate with the changes in air temperature and water temperature throughout the year in a short period of time after pouring. It is difficult to form a stable temperature field after the thin-walled structure is poured, and it is difficult to formulate temperature control standards and evaluate temperature control elements. The above phenomenon has resulted in poor temperature control and crack prevention effects in thin-walled large-volume concrete structures, and temperature cracks are difficult to avoid.

[0003] Therefore, the present invention proposes a new method for formulating temperature control standards to solve the above problems. Summary of the invention

[0004] In order to solve the above problems of the prior art, that is, to solve the problem of how to formulate the foundation temperature difference, the upper and lower layer temperature difference and the foundation temperature difference to prevent temperature cracks. The present invention provides a method for formulating temperature control standards for large-volume thin-walled concrete structures, the method comprising:

[0005] Step S1: Obtain thermal parameters, mechanical parameters and geometric characteristics of the thin-walled concrete structure;

[0006] Step S2: constructing a numerical simulation model of the thin-walled concrete structure based on the geometric features;

[0007] Step S3: obtaining the temperature process line and stress process line of the thin-walled concrete structure in different seasons based on the numerical simulation model and the thermal parameters and mechanical parameters;

[0008] Step S4: Obtaining a stress threshold σ based on the stress process line t And the maximum stress σ in a certain year after the temperature stabilizes Max and the minimum stress σ min , and the maximum stress σ is obtained by the following method: Max and stress threshold σ t The demarcation coefficient η:

[0009] η=(σ max -σt ) / (σ max -σ min )

[0010] Step S5: Obtain the maximum temperature value of the thin-walled concrete structure and the maximum temperature T of a certain year after the temperature stabilizes according to the temperature process line. Max and minimum temperature T min ,

[0011] Step S6: According to the highest temperature value, the maximum temperature T Max and minimum temperature T min , get the maximum value of the basic temperature difference △T Max With the minimum value △T min ;

[0012] Step S7: Obtain the basic temperature difference value △T according to the following formula t :

[0013] △T t =△T max -η×(△T max -△T min )

[0014] In one embodiment, the method further comprises:

[0015] Step S8: The basic temperature difference ΔT t With minimum temperature T min Sum them and get the corrected maximum temperature value T;

[0016] Step S9: formulating temperature control measures according to the corrected maximum temperature value T to reduce the maximum temperature of the thin-walled concrete structure to the corrected maximum temperature value T;

[0017] Step S10: Calculate the maximum stress value at this time and determine whether the maximum stress value is less than the stress threshold σ t ;

[0018] Step S11: If not, repeat steps S4 to S10 until the maximum stress value is less than the stress threshold σ t , and the foundation temperature difference when this condition is met is taken as the foundation temperature difference of the thin-walled concrete structure;

[0019] In one embodiment, the thin-walled concrete structure includes an upper newly cast concrete layer and a lower old concrete layer; the method further includes:

[0020] Acquire the temperature process lines of the newly poured concrete layer and the old concrete layer based on the numerical simulation model;

[0021] When the temperature process line is in the descending period, the temperature difference between the new concrete layer and the old concrete layer is taken as the temperature difference between the new and old concrete;

[0022] When the temperature process line is in the rising stage, the difference between the highest average temperature of the newly poured concrete layer within a range of 0.25L above the old concrete layer and the average temperature of the old concrete is taken as the temperature difference between the new and old concrete.

[0023] In one embodiment, stabilization measures are formulated based on the foundation temperature difference and the temperature difference between new and old concrete for actual pouring of the thin-walled concrete structure.

[0024] In one embodiment, “according to the highest temperature value, the maximum temperature T Max and minimum temperature T min , get the maximum value of the basic temperature difference △T Max With the minimum value △T min The steps include:

[0025] The maximum temperature T is obtained by subtracting the base temperature difference from the maximum temperature Max , get the maximum value of the basic temperature difference △T Max ;

[0026] The minimum temperature value of the base temperature difference minus the maximum temperature value △T min , get the minimum value of the basic temperature difference △T min .

[0027] In one embodiment, the method further comprises: obtaining a central temperature process line and a surface temperature process line of the thin-walled concrete structure in different seasons based on the numerical simulation model;

[0028] The difference between the concrete center temperature and surface temperature in late summer and early autumn is used as the internal and external temperature difference; or,

[0029] The difference between the center temperature and surface temperature of the concrete in late winter and early spring is taken as the internal and external temperature difference.

[0030] In one embodiment, the thermal parameters include at least the adiabatic temperature rise, thermal conductivity, and surface heat dissipation coefficient of the concrete material.

[0031] In one embodiment, the mechanical parameters include at least the elastic modulus, hardening coefficient, and tensile strength of the concrete material.

[0032] The advantages of the present invention are:

[0033] The method for formulating temperature control standards for large-volume thin-walled concrete structures provided by the present invention can formulate more reasonable foundation temperature differences, upper and lower layer temperature differences, and internal and external temperature differences, so as to facilitate the formulation of corresponding temperature control measures based on the temperature control standards and prevent the occurrence of temperature cracks in large-volume thin-walled concrete structures. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 It is a schematic diagram of the main steps of the method for formulating the temperature control standard of a large-volume thin-walled concrete structure of the present invention;

[0035] Figure 2 The temperature process line of a thin-walled concrete structure of a certain project;

[0036] Figure 3 It is a schematic diagram of the temperature process line calculated based on the numerical simulation model of the present invention;

[0037] Figure 4 It is a schematic diagram of the stress process line calculated based on the numerical simulation model of the present invention;

[0038] Figure 5 This is the monthly minimum temperature and stable temperature chart of a certain project. DETAILED DESCRIPTION

[0039] The preferred embodiments of the present invention are described below with reference to the accompanying drawings. It should be understood by those skilled in the art that these embodiments are only used to explain the technical principles of the present invention and are not intended to limit the protection scope of the present invention.

[0040] Temperature control and crack prevention of large-volume thin-walled concrete structures requires accurate standards for the internal and external temperature difference, the temperature difference between the upper and lower layers, and the temperature difference of the foundation, so as to propose corresponding temperature control measures according to the temperature control standards. The purpose of the present invention is to provide a method for calculating the temperature difference between the upper and lower layers, the temperature difference between the foundation, and the internal and external temperature difference, so as to make corresponding temperature control measures according to the temperature standard to prevent the occurrence of temperature cracks. The temperature control standard formulation method for large-volume thin-walled concrete structures provided by the invention is described in detail below in conjunction with the accompanying drawings.

[0041] See attached Figure 1 , Figure 1 The main steps of the method for formulating the temperature control standard for a large-volume thin-walled concrete structure provided in this embodiment are exemplified. Figure 1As shown, the method for formulating temperature control standards for large-volume thin-walled concrete structures provided by the present invention mainly includes: establishing a numerical simulation model of the thin-walled concrete structure, obtaining a temperature process line and a stress process line based on the numerical simulation model, determining a boundary coefficient η, and then determining a maximum temperature value, formulating temperature control measures to reduce the maximum temperature value, and verifying whether the maximum temperature value meets the specification requirements through the newly generated temperature process line and stress process line, and if so, determining the foundation temperature difference and the temperature difference between the new and old concrete. The above process is described in detail below.

[0042] Step S1: Obtain thermal parameters, mechanical parameters and geometric features of the thin-walled concrete structure. Specifically, the large-volume thin-walled concrete structure can be a dam, a pump station, a lock chamber and other structures. The thermal parameters at least include the adiabatic temperature rise, thermal conductivity and surface heat dissipation coefficient of the concrete material. The mechanical parameters at least include the elastic modulus, hardening coefficient and tensile strength of the concrete material. The geometric features are the geometric size information of the thin-walled concrete structure to facilitate the construction of a numerical simulation model of the thin-walled concrete structure.

[0043] Step S2: constructing a numerical simulation model of the thin-walled concrete structure based on geometric features.

[0044] Step S3: Based on the numerical simulation model and based on the thermal parameters and mechanical parameters, the temperature process line and stress process line of the thin-walled concrete structure in different seasons are obtained.

[0045] See attached Figure 2 The temperature process line of a certain project, with the horizontal axis being the date (month and year) and the vertical axis being the temperature (degrees Celsius). It can be found that the temperature process line of the thin-walled concrete structure is highly consistent with the regularity of the ambient temperature. Therefore, when determining the basic temperature difference standard and the temperature difference standard between the new and old concrete, the appropriate low temperature value is selected based on the highest temperature. The first calculation of the temperature process line and the stress process line can be set as the pouring conditions of conventional concrete.

[0046] The present invention uses a numerical simulation model to calculate the pouring temperature process line and stress process line under different seasonal conditions based on the provided thermal parameters and mechanical parameters, and selects the stress safety factor of the structure according to the specification. The calculated temperature process line and stress process line are as follows: Figure 3 and Figure 4 shown. Figure 3 is the temperature process line of the key point, Figure 4 is the stress process line of the key point, wherein the key point is a position point selected on the numerical simulation model, preferably a position point with maximum stress determined by simulation analysis results.

[0047] The existing foundation temperature difference standard is mainly determined by the maximum and minimum temperatures of the concrete. The maximum temperature is determined by the temperature control measures in the early stage of pouring, while the minimum temperature of thin-walled concrete is mainly determined by the temperature change of the concrete. After taking a series of necessary temperature control measures, the foundation temperature difference is completely determined by the final stable temperature change. Please refer to the attached Figure 5 , is the temperature process line of the lowest temperature and stable temperature of a certain project. The stable temperature change curve of thin-walled concrete structure takes the highest value to calculate the basic temperature difference, which may cause the temperature control standard to be too strict, and the temperature control measures are difficult or impossible to implement. Taking the lowest value as the basic temperature difference, the temperature stress is too large and cannot meet the requirements. Therefore, the basic temperature difference in the present invention is obtained by back-calculation based on the temperature stress, and the specific process is as follows:

[0048] Step S4: Obtain stress threshold σ based on stress process line t And the maximum stress σ in a certain year after the temperature stabilizes Max and the minimum stress σ min , and obtain the maximum stress σ according to the formula Max and stress threshold σ t The demarcation coefficient η:

[0049] η=(σ max -σ t ) / (σ max -σ min ) (1)

[0050] Because the stress process line of the thin-walled concrete structure is highly consistent with the regularity of the ambient temperature, and the appearance of the maximum and minimum stress values ​​is also caused by the periodic change of the annual temperature, the corresponding maximum and minimum stress values ​​in a certain year after the temperature stabilizes are selected to complete the calculation of formula (1).

[0051] Step S5: Obtain the maximum temperature value of the thin-walled concrete structure and the maximum temperature T of a certain year after the temperature stabilizes according to the temperature process line Max and minimum temperature T min Specifically, the maximum temperature value T of the basic temperature difference is subtracted from the maximum temperature value Max , get the maximum value of the basic temperature difference △T Max ; Subtract the minimum temperature value of the basic temperature difference from the maximum temperature value △T min , get the minimum value of the basic temperature difference △T min .

[0052] Step S6: According to the highest temperature value and the maximum temperature T Max and minimum temperature T min , get the maximum value of the basic temperature difference △T Max With the minimum value △T min ;

[0053] Step S7: Obtain the basic temperature difference △T according to the method shown in formula (2) t :

[0054] △T t =△T max -η×(△T max -△T min ) (2)

[0055] Because △T in formula (2) t Very close to the basic temperature difference, this embodiment is to △T t As the basis for determining the basic temperature difference.

[0056] Step S8: Set the basic temperature difference △T t With minimum temperature T min Sum and get the corrected maximum temperature value T; that is, T = T min +△T t

[0057] Step S9: formulating temperature control measures according to the corrected maximum temperature value T to reduce the maximum temperature of the thin-walled concrete structure to the corrected maximum temperature value T;

[0058] Step S10: Calculate the maximum stress value at this time and determine whether the maximum stress value is less than the stress threshold σ t ;

[0059] Step S11: If not, repeat steps S4 to S10 until the maximum stress value is less than the stress threshold σ t , and the basic temperature difference when this condition is met is used as the basic temperature difference of the thin-walled concrete structure. If so, directly calculate △T in step S7 t Temperature differences as a basis for thin-walled concrete structures.

[0060] In addition, the thin-walled concrete structure includes a newly poured concrete layer on the upper layer and an old concrete layer on the lower layer. It is necessary to formulate the temperature difference between the new and old concrete so as to formulate temperature control measures based on the temperature difference between the new and old concrete to prevent the occurrence of temperature cracks. The temperature difference between the upper and lower layers in the prior art refers to the difference between the highest average temperature of the concrete within the range of 0.25L above the height of the old concrete and the average temperature of the lower layer of old concrete when the concrete pouring begins, that is, the temperature difference between the new and old concrete, where L is the length of the newly poured concrete block, and the age of the new and old concrete exceeds 28 days. However, the temperature fluctuation of the thin-walled structure concrete can be achieved in a very short time. Therefore, when formulating the upper and lower layer temperatures, pay attention to the concrete temperature process line of the season. When the temperature is in a falling period, the temperature difference between the new and old concrete at the moment of the highest temperature of the new concrete is the temperature difference between the new and old concrete. When the temperature is in an ascending period, the temperature difference between the new and old concrete is formulated according to the actual definition.

[0061] Specifically: Based on the numerical simulation model, the temperature process line of the newly poured concrete layer and the old concrete layer is obtained, and the temperature process line is the temperature process line for determining the basic temperature difference value. When the temperature process line is in the descending period, the temperature difference between the newly poured concrete layer and the old concrete layer is taken as the temperature difference between the new and old concrete layers; when the temperature process line is in the ascending period, the difference between the highest average temperature of the newly poured concrete layer within the range of 0.25L above the old concrete layer and the average temperature of the old concrete is taken as the temperature difference between the new and old concrete layers.

[0062] After obtaining the standards for foundation temperature difference and new-old concrete temperature difference, stabilization measures are formulated for the foundation temperature difference and new-old concrete temperature difference for the actual pouring of thin-walled concrete structures.

[0063] In addition, the temperature control standard formulation method of the large-volume thin-walled concrete structure provided by the present invention also includes: obtaining the central temperature process line and the surface temperature process line of the thin-walled concrete structure in different seasons based on the numerical simulation model; based on the central temperature process line and the surface temperature process line, the difference between the central temperature and the surface temperature of the concrete at the end of summer and the beginning of autumn is used as the internal and external temperature difference; or, based on the central temperature process line and the surface temperature process line, the difference between the central temperature and the surface temperature of the concrete at the end of winter and the beginning of spring is used as the internal and external temperature difference. Based on this, the internal and external temperature difference of the thin-walled concrete structure can be determined.

[0064] In summary, the temperature control standard formulation method for large-volume thin-walled concrete structures provided by the present invention can formulate more reasonable foundation temperature differences, upper and lower layer temperature differences, and internal and external temperature differences, so as to formulate corresponding temperature control measures based on the temperature control standards and prevent the occurrence of temperature cracks in large-volume thin-walled concrete structures.

[0065] So far, the technical solutions of the present invention have been described in conjunction with the preferred embodiments shown in the accompanying drawings. However, it is easy for those skilled in the art to understand that the protection scope of the present invention is obviously not limited to these specific embodiments. Without departing from the principle of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will fall within the protection scope of the present invention.

Claims

1. A method for formulating temperature control standards for large-volume thin-walled concrete structures, characterized in that: The method comprises: Step S1: Obtain thermal parameters, mechanical parameters and geometric characteristics of the thin-walled concrete structure; Step S2: constructing a numerical simulation model of the thin-walled concrete structure based on the geometric features; Step S3: obtaining the temperature process line and stress process line of the thin-walled concrete structure in different seasons based on the numerical simulation model and the thermal parameters and mechanical parameters; Step S4: Obtaining a stress threshold σ based on the stress process line t And the maximum stress σ in a certain year after the temperature stabilizes Max and the minimum stress σ min , and the maximum stress σ is obtained by the following method: Max and stress threshold σ t The demarcation coefficient η the=(s max -s t ) / (s max -s min ) Step S5: Obtain the maximum temperature value of the thin-walled concrete structure and the maximum temperature T of a certain year after the temperature stabilizes according to the temperature process line. Max and minimum temperature T min , Step S6: According to the highest temperature value, the maximum temperature T Max and minimum temperature T min , get the maximum value of the basic temperature difference △T Max With the minimum value △T min ; Step S7: Obtain the basic temperature difference value △T according to the following formula t : △T t =△T max -η×(△T max -△T min ) 。 2. The method for formulating temperature control standards for large-volume thin-walled concrete structures according to claim 1, characterized in that: The method further comprises: Step S8: The basic temperature difference ΔT t With minimum temperature T min Sum them and get the corrected maximum temperature value T; Step S9: formulating stabilization measures according to the corrected maximum temperature value T to reduce the maximum temperature of the thin-walled concrete structure to the corrected maximum temperature value T; Step S10: Calculate the maximum stress value at this time and determine whether the maximum stress value is less than the stress threshold σ t ; Step S11: If not, repeat steps S4 to S10 until the maximum stress value is less than the stress threshold σ t , and the foundation temperature difference when this condition is met is used as the foundation temperature difference of the thin-walled concrete structure.

3. The method for formulating temperature control standards for large-volume thin-walled concrete structures as claimed in claim 2, characterized in that: The thin-walled concrete structure comprises an upper newly poured concrete layer and a lower old concrete layer; The method further comprises: Acquire the temperature process lines of the newly poured concrete layer and the old concrete layer based on the numerical simulation model; When the temperature process line is in the descending period, the temperature difference between the new concrete layer and the old concrete layer is taken as the temperature difference between the new and old concrete; When the temperature process line is in the rising stage, the difference between the highest average temperature of the newly poured concrete layer within a range of 0.25L above the old concrete layer and the average temperature of the old concrete is taken as the temperature difference between the new and old concrete.

4. The method for formulating temperature control standards for large-volume thin-walled concrete structures as claimed in claim 3, characterized in that: Temperature control measures are formulated based on the foundation temperature difference and the temperature difference between new and old concrete for actual pouring of the thin-walled concrete structure.

5. The method for formulating temperature control standards for large-volume thin-walled concrete structures according to claim 1, characterized in that: "According to the maximum temperature value, the maximum temperature T Max and minimum temperature T min , get the maximum value of the basic temperature difference △T Max With the minimum value △T min The steps include: The maximum temperature T is obtained by subtracting the base temperature difference from the maximum temperature Max , get the maximum value of the basic temperature difference △T Max ; The minimum temperature value of the base temperature difference minus the maximum temperature value △T min , get the minimum value of the basic temperature difference △T min .

6. The method for formulating temperature control standards for large-volume thin-walled concrete structures according to claim 1, characterized in that: The method further comprises: Based on the numerical simulation model, obtain the central temperature process line and the surface temperature process line of the thin-walled concrete structure in different seasons; The difference between the concrete center temperature and surface temperature in late summer and early autumn is used as the internal and external temperature difference; or, The difference between the center temperature and surface temperature of the concrete in late winter and early spring is taken as the internal and external temperature difference.

7. The method for formulating temperature control standards for large-volume thin-walled concrete structures according to claim 1, characterized in that: The thermal parameters at least include the adiabatic temperature rise, thermal conductivity, and surface heat dissipation coefficient of the concrete material.

8. The method for formulating temperature control standards for a large-volume thin-walled concrete structure as claimed in claim 1, characterized in that: The mechanical parameters at least include elastic modulus, hardening coefficient and tensile strength of the concrete material.

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