Method for calculating and correcting flow of cooling water pipe in mass concrete construction

Abstract

The invention provides a method for calculating and correcting the flow of a cooling water pipe in mass concrete construction, which comprises the following steps of: establishing a mass concrete structure finite element model, performing concrete hydration heat analysis, and determining the diameter, spacing and layer number of the cooling water pipe and the calculated water flow in a structure temperature rise stage; determining water flow and boundary conditions at different moments in the cooling stage; extracting a temperature result of a key measuring point in mass concrete finite element hydration heat analysis, and calculating a theoretical cooling rate of the structure; dividing the theoretical cooling rate curve into a plurality of stages, defining a theoretical calculation cooling flow coefficient, generating a theoretical cooling flow coefficient sequence, actually measuring the cooling flow coefficient, and generating an actual cooling flow coefficient sequence; based on the grey system theory, correcting the actual cooling flow coefficient of the next stage; and correcting the actual flow of the next stage. Based on the grey system theory, the calculated water flow is corrected, and the mass concrete hydration heat monitoring precision can be improved.

Description

Technical Field

[0001] The invention belongs to the technical field of concrete construction, and in particular relates to a method for calculating and correcting the flow rate of cooling water pipes in large-volume concrete construction. Background Art

[0002] Large-volume concrete structures have the characteristics of poor thermal conductivity and slow hydration heat dissipation, which are prone to large internal and external temperature differences and temperature stress, leading to cracks in the structure. In order to avoid temperature cracks caused by the hydration heat of large-volume concrete, water cooling is often used to cool down the concrete structure in actual projects. The traditional temperature control calculation method is to first establish a large-volume concrete hydration heat analysis model to obtain the temperature field distribution of the structure, and then determine the layout of the cold water pipe and the theoretical water flow design based on the "experience + trial calculation" method. The above method still has certain problems in the actual temperature control process: in the actual temperature control process, environmental factors such as cooling water temperature, internal temperature field of the pedestal, and external ambient temperature are inconsistent with the ideal state, resulting in inaccurate calculation of cold water flow, and large deviations in on-site manual control. Summary of the invention

[0003] In view of this, the present invention aims to overcome the defects in the prior art and proposes a method for calculating and correcting the flow rate of cooling water pipes in large-volume concrete construction.

[0004] To achieve the above object, the technical solution created by the present invention is implemented as follows:

[0005] A method for calculating and correcting the flow rate of cooling water pipes in mass concrete construction comprises the following steps:

[0006] S1. Establish a finite element model of a large concrete structure and conduct concrete hydration heat analysis;

[0007] S2. Based on the finite element model of step S1, determine the water flow rate Q at different times during the cooling stage d1 , Q d2 , Q d3 ...Q di , and boundary conditions;

[0008] S3. Calculate the theoretical cooling rate ΔT of the structure Cal (t); If the theoretical cooling rate meets the specification limit, proceed to the next step; if the theoretical cooling rate does not meet the specification limit, repeat step S2;

[0009] S4. According to the actual situation, adjust the calculated theoretical flow rate and set the theoretical cooling rate ΔT Cal The (t) curve is divided into several stages, and the theoretical cooling rate corresponding to each stage is ΔT Cal,i , Where T Cal (ti ), T Cal (t i-1 ) represent the temperature at the i-th moment and the i-1-th moment respectively;

[0010] S5. Define the theoretical calculation cooling flow coefficient: Generate theoretical cooling flow coefficient sequence: (a Cal，1 ,a Cal，2 ,…,α Cal，n ), measured cooling flow coefficient: Where ΔT Exp,i , Q Exp,i The actual cooling rate and actual water flow rate are measured respectively, and the actual cooling flow coefficient sequence is generated: (a Exp，1 ,α Exp，2 ,…,α Exp，n );

[0011] S6, correcting the actual cooling flow coefficient of the next stage;

[0012] S7. Correct the actual flow rate in the next stage.

[0013] Furthermore, in step S1, the maximum temperature of the concrete is focused on to ensure that the concrete temperature exceeds the specification limit.

[0014] Further, in step S1, the finite element model of the massive concrete structure includes determining the cold water pipe diameter, spacing, number of layers, and calculated water flow during the temperature rise stage of the structure.

[0015] Furthermore, in step S2, the key control index is the temperature stress of the concrete, so that it is always lower than the cracking strength of the material to avoid temperature cracks in the structure.

[0016] Furthermore, in step S2, the temperature stress of the structure is always lower than the crack resistance of the material.

[0017] Furthermore, in step S3, the theoretical cooling rate of the structure at any time should not exceed the specification limit.

[0018] Further, in step S3, the temperature results of key measuring points in the finite element hydration heat analysis of large-volume concrete are extracted, and the maximum temperature time history analysis result T of the concrete casting body is obtained. Cal (t), calculate the theoretical cooling rate ΔT of the structure Cal (t).

[0019] Furthermore, in step S4, the frequency of collecting data of concrete temperature and water flow measurement points is 30 minutes.

[0020] Further, in step S4, the theoretical cooling rate ΔT CalThe (t) curve is divided into several stages based on the actual temperature and flow measurement point monitoring frequency.

[0021] Further, in step S6, the measured data is selected to calculate the actual cooling flow coefficient sequence.

[0022] Furthermore, in step S6, calculation is performed based on the latest measured data.

[0023] Furthermore, in step S6, based on the grey system theory, the actual cooling flow coefficient of the next stage is corrected.

[0024] Further, in step S6, according to the theoretical cooling flow coefficient sequence and the measured cooling flow coefficient sequence in step S5, there is an n-dimensional non-negative error sequence, x (0) ={x (0) (1),x (0) (2),...,x (0) (n)};

[0025] Sequence x (1) Can be obtained by x (0) One-time cumulative generation Then there is x (1) ={x (1) (1),x (1) (2),...,x (1) (n)};

[0026] Sequence z (1) (k) is x (1) The average value is obtained, z (1) (k) = 0.5x (1) (k)+0.5x (1) (k-1), then z (1) ={z (1) (1),z (1) (2),…,z (1) (n)};

[0027] Due to x (1) , x (0) is the grey differential sequence, x (0) With x (1) The following relationship is satisfied, which is called the GM(1,1) model;

[0028]

[0029] Among them, y n is the data column, B is the data matrix, is a parameter vector. If and only if the residual sum of squares of GM(1,1) satisfies the minimum criterion, a and b can be calculated by combining the following formula:

[0030]

[0031] According to the GM(1,1) model, the grey differential equation is obtained: The solution of the grey differential equation is expressed as:

[0032]

[0033] Furthermore, in step S7, the equation of step S6 is restored to obtain a predicted value of the error of the cooling flow coefficient in the next test phase, and then a corrected value of the actual cooling flow is obtained.

[0034] Furthermore, in step S7, a computer algorithm is used to correct the water flow.

[0035] Compared with the prior art, the present invention has the following advantages:

[0036] The present invention is aimed at the calculation method and correction of the hydration heat control of large-volume concrete. Based on the evolution law of concrete hydration heat, a calculation method for temperature control of large-volume concrete is proposed. First, an accurate large-volume concrete structure model is established to determine the diameter, spacing, distribution of the structural cold water pipes and the calculated water flow rate in the temperature rise stage. In order to solve the problem that the actual temperature control environment is inconsistent with the ideal design state, the present invention corrects the calculated water flow rate based on the gray system theory, which can improve the monitoring accuracy of the hydration heat of large-volume concrete. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] The drawings constituting part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments and descriptions of the present invention are used to explain the present invention and do not constitute an improper limitation on the present invention. In the drawings:

[0038] Figure 1 The present invention is a flow chart of the method created by the present invention. DETAILED DESCRIPTION

[0039] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0040] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention. In addition, the terms "first", "second", etc. are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, features defined as "first", "second", etc. may explicitly or implicitly include one or more of the features. In the description of the present invention, unless otherwise specified, "multiple" means two or more.

[0041] In the description of the invention, it should be noted that, unless otherwise clearly specified and limited, the terms "installation", "connection" and "connection" should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be indirectly connected through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the invention can be understood according to specific circumstances.

[0042] The present invention will be described in detail below with reference to the accompanying drawings and in combination with embodiments.

[0043] A method for calculating and correcting the cooling water pipe flow rate in mass concrete construction, such as Figure 1 As shown, the following steps are included:

[0044] S1. According to the temperature control specification of large-volume concrete, the structure, volume and construction plan of large-volume concrete, preliminarily design the water cooling temperature control measures for large-volume concrete, establish the finite element model of large-volume concrete structure, and conduct concrete hydration heat analysis; perform parametric design of water cooling measures, and then determine the cold water pipe diameter d, spacing s, number of layers n and the calculated water flow Q in the temperature rise stage of the structure u ;

[0045] S2. Based on the finite element model of step S1, determine the water flow rate Q at different times during the cooling stage d1 , Q d2 , Q d3 ...Q di, and boundary conditions, control the cooling rate inside the structure, ensure that the temperature difference between the inside and outside of the concrete is within the allowable range, and the key control index is the temperature stress of the concrete, so that it is always lower than the cracking strength of the material to avoid temperature cracks in the structure; the present invention can determine the water flow rate and boundary conditions of the cold water pipe of the large volume concrete, that is, the insulation measures, by analyzing the hydration heat of the large volume concrete in the temperature drop stage;

[0046] S3. Extract the temperature results of key measuring points in the finite element hydration heat analysis of large-volume concrete, based on the time history analysis results of the maximum temperature inside the concrete casting body T Cal (t), calculate the theoretical cooling rate ΔT of the structure Cal (t); If the theoretical cooling rate meets the specification limit, proceed to the next step; if the theoretical cooling rate does not meet the specification limit, repeat step S2;

[0047] S4. Regulate the calculated theoretical flow rate according to the actual situation, and the theoretical cooling rate ΔT Cal (t) The curve is divided into several stages according to the actual temperature and the monitoring frequency of the flow measurement points. The theoretical cooling rate corresponding to each stage is ΔT Cal,i , Where T Cal (t i ), T Cal (t i-1 ) represent the temperature at the i-th moment and the i-1-th moment respectively;

[0048] Since there are certain differences between actual construction conditions and theoretical calculations, such as the cooling water temperature and external ambient temperature are constantly changing, the calculated theoretical flow rate must be adjusted according to actual conditions in order to achieve the theoretical cooling rate target.

[0049] S5. Under the conditions of certain cold water pipe diameter, spacing, layout and external boundary conditions, the cooling rate is mainly affected by the water flow rate, and within a certain range, the cooling rate is positively correlated with the water flow rate. Therefore, the theoretical calculation cooling flow coefficient is defined as: Generate theoretical cooling flow coefficient sequence: (a Cal，1 ,α Cal，2 ,…,α Cal，n ), measured cooling flow coefficient: Where ΔT Exp,i , Q Exp,i The actual cooling rate and actual water flow rate are measured respectively, and the actual cooling flow coefficient sequence is generated: (a Exp，1 ,α Exp，2 ,…,α Exp，n );

[0050] S6. Based on the grey system theory, the actual cooling flow coefficient of the next stage is corrected;

[0051] According to the theoretical cooling flow coefficient sequence and the measured cooling flow coefficient sequence in step S5, there is an n-element non-negative error sequence, x (0) ={x (0) (1),x (0) (2),...,x (0) (n)};

[0052] Sequence x (1) Can be obtained by x (0) One-time cumulative generation Then there is x (1) ={x (1) (1),x (1) (2),...,x (1) (n)};

[0053] Sequence z (1) (k) is x (1) The average value is obtained, z (1) (k) = 0.5x (1) (k)+0.5x (1) (k-1), then z (1) ={z (1) (1),z (1) (2),…,z (1) (n)};

[0054] Due to x (1) , x (0) is the grey differential sequence, x (0) With x (1) The model that satisfies the following relationship is called the GM(1,1) model.

[0055]

[0056] Among them, y n is the data column, B is the data matrix, is a parameter vector. If and only if the residual sum of squares of GM(1,1) satisfies the minimum criterion, a and b can be calculated by combining the following formula:

[0057]

[0058] According to the GM(1,1) model, the grey differential equation is obtained: The solution of the grey differential equation is expressed as:

[0059]

[0060] Preferably, measured data are selected to calculate the actual cooling flow coefficient sequence. The number of elements in the sequence should be appropriate and should be calculated from the latest measured data sets, which can further improve the prediction accuracy.

[0061] S7. Correct the actual flow rate in the next stage.

[0062] Since step S6 pre-processes the data, it needs to be restored. The final prediction value of the cooling flow coefficient error in the next test stage is The correction value of the actual cooling flow rate is Therefore, the actual water flow after correction is Preferably, a computer algorithm can be used to achieve intelligent correction of water flow.

[0063] In step S1, the maximum temperature of concrete is focused on to ensure that the concrete temperature exceeds the specification limit.

[0064] In step S2, the temperature stress of the structure is always lower than the crack resistance of the material.

[0065] In step S3, the theoretical cooling rate of the structure at any time should not exceed the specification limit, otherwise the flow rate and boundary conditions should be readjusted to make the structure meet the requirements.

[0066] In step S4, the frequency of collecting data of concrete temperature and water flow measurement points is 30 minutes.

[0067] In step S6, the measured data is selected to calculate the actual cooling flow coefficient sequence, and the calculation is performed based on the latest measured data.

[0068] The method of the present invention uses the defined cooling flow coefficient, the grey theory combined with the measured data to analyze, predict and correct the cooling flow coefficient, and calculates the cold water pipe flow with the corrected parameters to achieve the effect of accurate flow control in advance. The present invention proposes a correction method for calculating the cold water pipe flow of large-volume concrete temperature control. This method can improve the cold water control accuracy of concrete structures and has guiding significance for the temperature control of large-volume concrete. Taking the hydration heat control calculation of a bridge pier as an example, the specific implementation method of hydration heat design calculation and correction is described, and the specific implementation steps are as follows:

[0069] S1: Establish a finite element model for the hydration heat analysis of large-volume concrete, preliminarily design temperature control measures for large-volume concrete, determine the cold water pipe diameter d = 50mm, the spacing s is 1-1.5m, the number of layers n = 12, and the calculated water flow rate Qu = 7m3 / h in the structural temperature rise stage. At the age of 3d, the internal temperature of the concrete reaches the maximum, the internal temperature is lower than the specification limit of 65℃, and the maximum temperature rise is lower than 50℃.

[0070] S2: Based on the finite element model in step S1, adjust the water flow rate, boundary conditions, etc. during the temperature drop stage of the structure to determine Q d , the temperature stress of the structure is always lower than the crack resistance of the material.

[0071] S3: Extract the temperature results of the measuring points of the finite element hydration heat analysis of large-volume concrete, and based on the time history analysis results of the maximum temperature inside the concrete casting body T Cal (t), calculate the theoretical cooling rate ΔT of the structure Cal (t); The theoretical cooling rate of the structure meets the requirements of the specification.

[0072] S4: Determine the theoretical cooling rate ΔT from step S3 Cal (t), this monitoring uses a concrete intelligent temperature control integrated machine to monitor and process the temperature control process of large-volume concrete, which can realize real-time data processing. The collection frequency of concrete temperature and water flow measurement points is 30 minutes. The water tank temperature is adjusted in real time and can remain basically unchanged. The water flow is adjusted from the structural cooling stage.

[0073] S5: As an example, this embodiment only corrects the test data of the first 150 minutes. As a brief description, the theoretical cooling flow coefficient is calculated: Theoretical cooling flow coefficient sequence: (0.2789 0.3298 0.2989 0.29010.2820); the calculation formula of the measured cooling flow coefficient is: The actual cooling flow coefficient sequence is calculated to be: (0.26790.32680.29290.28210.2750).

[0074] S6: Based on the grey system theory, the actual cooling flow coefficient is corrected:

[0075] According to the theoretical cooling flow coefficient sequence and the measured cooling flow coefficient sequence in step S5, there is an n-dimensional error sequence, x (0) =(11,3,6,8,7), all are positive values ​​and do not need to be non-negative. (0) Generate x by one accumulation (1) =(11,14,20,28,35); sequence z (1) (k) is x (1) The average value is z (1) =(12.5,17,24,31.5); a, b can be calculated by combining the following formula:

[0076]

[0077] The solution of the grey differential equation is expressed as:

[0078]

[0079] S7: Restore the equation of step S6, and finally the error prediction value of the cooling flow coefficient in the next test stage is Then the correction value of the actual cooling flow rate is α Exp，n+1 =αCal，n+1 +0.0061. Therefore, the actual water flow after calculation and correction is:

[0080]

[0081] The present invention is aimed at the calculation method and correction of the hydration heat control of large-volume concrete. Based on the evolution law of concrete hydration heat, a calculation method for temperature control of large-volume concrete is proposed. First, an accurate large-volume concrete structure model is established to determine the diameter, spacing, distribution of the structural cold water pipes and the calculated water flow rate in the temperature rise stage. In order to solve the problem that the actual temperature control environment is inconsistent with the ideal design state, the present invention corrects the calculated water flow rate based on the gray system theory, which can improve the monitoring accuracy of the hydration heat of large-volume concrete.

[0082] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for calculating and correcting the flow rate of cooling water pipes in mass concrete construction, characterized in that: The steps include: S1. Establish a finite element model of a large concrete structure and conduct concrete hydration heat analysis; S2. Based on the finite element model of step S1, determine the water flow rate Q at different times during the cooling stage d1 , Q d2 , Q d3 ...Q di , and boundary conditions; S3. Calculate the theoretical cooling rate ΔT of the structure Cal (t); If the theoretical cooling rate meets the specification limit, proceed to the next step; if the theoretical cooling rate does not meet the specification limit, repeat step S2; S4. According to the actual situation, adjust the calculated theoretical flow rate and set the theoretical cooling rate ΔT Cal The (t) curve is divided into several stages, and the theoretical cooling rate corresponding to each stage is ΔT Cal，i , Where T Cal (t i ), T Cal (t i-1 ) represent the temperature at the i-th moment and the i-1-th moment respectively; S5. Define the theoretical calculation cooling flow coefficient: Generate theoretical cooling flow coefficient sequence: (α Cal,1 , α Cal,2 , …, α Cal，n ), measured cooling flow coefficient: Where ΔT Exp，i , Q Exp，i The actual cooling rate and actual water flow rate are measured respectively, and the actual cooling flow coefficient sequence is generated: (α Exp,1 , α Exp,2 , …, α Exp，n ); S6, correcting the actual cooling flow coefficient of the next stage; S7. Correct the actual flow rate in the next stage.

2. A method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1, characterized in that: In step S1, the maximum temperature of concrete is focused on to ensure that the concrete temperature exceeds the specification limit.

3. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1 is characterized by: In step S1, the finite element model of the massive concrete structure includes determining the cold water pipe diameter, spacing, number of layers, and calculated water flow during the temperature rise stage of the structure.

4. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1 is characterized by: In step S2, the key control index is the concrete temperature stress, which is always lower than the cracking strength of the material to avoid temperature cracks in the structure.

5. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1 is characterized by: In step S2, the temperature stress of the structure is always lower than the crack resistance of the material.

6. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1 is characterized by: In step S3, the theoretical cooling rate of the structure at any time should not exceed the specification limit.

7. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1, characterized in that: In step S3, the temperature results of key measuring points in the finite element hydration heat analysis of large-volume concrete are extracted, and the maximum temperature time history analysis result T Cal (t), calculate the theoretical cooling rate ΔT of the structure Cal (t).

8. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1 is characterized by: In step S4, the frequency of collecting data of concrete temperature and water flow measurement points is 30 minutes.

9. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1, characterized in that: In step S4, the theoretical cooling rate ΔT Cal The (t) curve is divided into several stages based on the actual temperature and flow measurement point monitoring frequency.

10. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1, characterized in that: In step S6, the measured data is selected to calculate the actual cooling flow coefficient sequence.

11. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1, characterized in that: In step S6, calculation is performed based on the latest measured data.

12. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1, characterized in that: In step S6, based on the grey system theory, the actual cooling flow coefficient of the next stage is corrected.

13. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1, characterized in that: In step S6, according to the theoretical cooling flow coefficient sequence and the measured cooling flow coefficient sequence in step S5, there is an n-dimensional non-negative error sequence, x (0) ={x (0) (1), x (0) (2), ..., x (0) (n)}; Sequence x (1) Can be obtained by x (0) One-time cumulative generation Then there is x (1) ={x (1) (1), x (1) (2), ..., x (1) (n)}; Sequence z (1) (k) is x (1) The average value is obtained, z (1) (k) = 0.5x (1) (k)+0.5x (1) (k-1), then z (1) ={z (1) (1), z (1) (2), ..., z (1) (n)}; Due to x (1) , x (0) is the grey differential sequence, x (0) With x (1) The following relationship is satisfied, which is called the GM(1,1) model; Among them, y n is the data column, B is the data matrix, is the parameter vector. If and only if the residual sum of squares of GM(1,1) satisfies the minimum criterion, a and b can be calculated by combining the following formula: According to the GM (1, 1) model, the grey differential equation is obtained: The solution of the grey differential equation is expressed as:

14. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1, characterized in that: In step S7, the equation of step S6 is restored to obtain the predicted value of the error of the cooling flow coefficient in the next test phase, and then the corrected value of the actual cooling flow is obtained.

15. The method for calculating and correcting the cooling water pipe flow rate in mass concrete construction according to claim 1, characterized in that: In step S7, the water flow is corrected using a computer algorithm.

Images