CN105862866B - A kind of method for determining thermometer burial place in concrete pouring bin containing cooling water pipe - Google Patents

Abstract

A method for determining the embedding position of a thermometer in a concrete pouring silo containing a cooling water pipe, the method comprising the following steps: Step 1: Obtaining the temperature field of a concrete model containing a cooling water pipe; Step 2: Using a shape function to obtain the temperature at any point in the section; Step 3 : From the average temperature history of the concrete model with cooling water pipes obtained in step 1 and the temperature at any point obtained in step 2, the optimal model of the geometric position of the thermometer is established; step 4: using the optimization algorithm to solve the optimal model of the geometric position of the thermometer, and obtaining the optimal temperature for embedding the thermometer Geometric position coordinates. The method for determining the embedding position of the thermometer in the concrete pouring silo containing the cooling water pipe provided by the present invention can solve the problem of uncertain geometrical position of the thermometer embedding in the concrete pouring silo, realize accurate determination of the embedding position of the thermometer, and achieve reasonable temperature monitoring Purpose.

Description

A method for determining the embedding position of the thermometer in the concrete pouring silo with cooling water pipes

technical field

The invention relates to the field of concrete pouring, in particular to a method for determining the embedding position of a thermometer in a concrete pouring bin containing a cooling water pipe.

Background technique

Water pipe cooling is an important method to control temperature and prevent cracks in concrete dam construction, and it has been widely used all over the world since it was first used in the Hoover arch dam in the 1930s. However, because the temperature field generated by the water pipe cooling is very complicated, it is actually a double-edged sword, which can effectively reduce the temperature of the concrete, but if the cooling rate is too fast, it can cause serious cracks. In response to this problem, Zhu Bofang proposed the water cooling principle of "small temperature difference, early cooling, and slow cooling". At present, the principle of water cooling has gradually been widely used in high concrete dam engineering. For example, for the Xiluodu extra-high arch dam, the design unit divided the water pipe cooling into three phases (first, middle and second phases) and nine stages, and strictly controlled the target temperature and temperature change rate in each stage. The process line is cooled by water, and a good temperature control and crack prevention effect is obtained.

The analysis of the design temperature control process line of the design institute shows that the design temperature control process line is the average temperature history of the concrete pouring silo. Obviously, in order to monitor the temperature of the concrete pouring silo, it is necessary to embed a thermometer in the concrete pouring silo for temperature monitoring. Due to the large size of the concrete pouring silo, the thickness is generally 1-3m, the width across the river is about 20m, and the length along the river is 20m-60m. During actual construction, at most 1 to 2 thermometers should be buried in each concrete pouring bin. During the practice of temperature control, it was found that because the temperature field of the concrete pouring silo during the water cooling period is very complicated, the measured temperature is low when the thermometer is buried close to the water pipe, and the measured temperature is high when it is far away from the water pipe. How to embed a thermometer in the concrete pouring silo so that the measured temperature represents the average temperature of the concrete pouring silo is of concern to the engineering construction unit, but so far this problem has not been reported in the relevant literature. Due to the randomness and blindness of the position of the buried thermometer in the actual concrete pouring silo, the actual temperature measured by the thermometer cannot reflect the average temperature history of the concrete pouring silo well, and it is difficult to achieve the purpose of reasonable temperature monitoring.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for determining the embedding position of the thermometer in the concrete pouring silo containing the cooling water pipe, which can solve the problem of uncertain geometrical position of the thermometer in the concrete pouring silo, and realize the accurate determination of the embedding position of the thermometer.

In order to solve the above-mentioned technical problems, the technical solution adopted in the present invention is: a method for determining the embedding position of the thermometer in the concrete pouring silo containing the cooling water pipe, the method comprising the following steps:

Step 1: Establish a concrete model with cooling water pipes, use the water pipe cooling finite element method to simulate the temperature field, and obtain the temperature field of the concrete model with cooling water pipes,

The average temperature history of the concrete model with cooling water pipes is calculated by formula (1):

Assuming time t, the average temperature T _ave (t) of the concrete pouring silo during water cooling is

In the formula: T _g (t) is the temperature of the unit Gauss point at time t; V _g is the occupied volume of the unit Gauss point, which can be calculated by using the Jacobian determinant |J| of the Gauss point; Accumulated for the unit Gauss point; Accumulated for the pouring bin unit; The volume of the concrete pouring chamber to remove the volume occupied by the water pipes;

Step 2: Select a typical section of the concrete model with cooling water pipes, use the shape function to obtain the temperature at any point of the section from the node temperature of the section element

The temperature at any point in the concrete pouring silo is

In the formula, N _i (x, y, z) is the shape function, T _i (t) is the temperature of node i at time t;

Step 3: From the average temperature history T _ave (t) of the concrete model containing the cooling water pipe obtained in step 1 and the temperature T (x, y, z, t) at any point obtained in step 2, an optimal model for the geometric position of the thermometer is established;

Step 4: Use the optimization algorithm to solve the optimal model of the geometric position of the thermometer, and obtain the optimal geometric position coordinates of the buried thermometer.

In step 1, the cooling water pipes in the concrete pouring silo are arranged in a serpentine shape, and the concrete model containing the cooling water pipes is established as a concrete prism model containing the cooling water pipes.

In step 2, the typical section selected is the middle section of the concrete prism model.

The concrete prism adopts hexahedral 8-node elements, and the middle section is a quadrilateral 4-node element. A quadrilateral 12-node element is introduced, and the temperature calculation at any point in the section is simplified by replacing the quadrilateral 4-node isoparametric element with the quadrilateral 12-node isoparametric element.

The invention provides a method for determining the embedding position of the thermometer in the concrete pouring silo containing the cooling water pipe, which adopts the combination of the optimization algorithm and the water pipe cooling finite element method, and can solve the problem of the uncertain geometric position of the thermometer embedding in the concrete pouring silo, and realizes accurate Determine the embedding position of the thermometer; the method is simple, the result is accurate, and the application range is wide; in order to obtain the temperature of any point in the section from the nodal temperature, a quadrilateral 12-node element is introduced, and the quadrilateral 4-node isoparametric element is replaced by the quadrilateral 12-node isoparametric element To simplify the calculation of temperature at any point in the section, it greatly simplifies the calculation process.

Description of drawings

Below in conjunction with accompanying drawing and embodiment the present invention will be further described:

Fig. 1 adopts the cooling water pipe of serpentine arrangement in the concrete pouring silo of the present invention;

Fig. 2 is the concrete prism model containing the cooling water pipe that step 1 establishes in the embodiment of the present invention;

Fig. 3 is the finite element grid of the first kind of prism section in step 1 in the embodiment of the present invention;

Fig. 4 is the finite element grid of the second kind of prism section in step 1 in the embodiment of the present invention;

Fig. 5 is the finite element grid of the third kind of prism section in step 1 in the embodiment of the present invention;

Fig. 6 is the finite element grid of the fourth prism section in step 1 in the embodiment of the present invention;

Fig. 7 is the concrete prism average temperature process line drawn by formula (1) calculation result in step 1 in the embodiment of the present invention;

Fig. 8 is a quadrilateral 12-node diagram adopted in the first prism cross-section in step 2 in the embodiment of the present invention;

Fig. 9 is a quadrilateral 12-node diagram adopted in the second prism section in step 2 in the embodiment of the present invention;

Fig. 10 is a quadrilateral 12-node diagram adopted in the third prism section of step 2 in the embodiment of the present invention;

Fig. 11 is a quadrilateral 12-node diagram adopted in the fourth prism cross-section in step 2 in the embodiment of the present invention;

Fig. 12 is a comparison diagram of the interpolation temperature of the quadrilateral 12 nodes used in the first prism section in step 2 of the embodiment of the present invention and the simulation calculation node temperature difference;

Fig. 13 is a geometric position distribution diagram drawn by the geometric position of the first prism cooling water pipe in step 4 in the embodiment of the present invention;

Fig. 14 is a geometric position distribution diagram drawn by the geometric position of the second prism cooling water pipe in step 4 in the embodiment of the present invention;

Fig. 15 is a geometric position distribution diagram drawn by the geometric position of the third prism cooling water pipe in step 4 in the embodiment of the present invention;

Fig. 16 is a geometric position distribution drawing of the geometric position of the third type of prism cooling water pipe in step 4 in the embodiment of the present invention.

detailed description

The concrete pouring silo with cooling water pipes is as follows:

According to existing engineering experience, the distance between water pipes buried in concrete dams is usually 1.0-3.0m. The expression of concrete adiabatic temperature rise is θ(t)=25.3(1-e ^-0.315τ ), the thermal conductivity of concrete λ=8.49kJ/(m·h·℃), and the specific heat c=0.955kJ/(kg·℃) , density ρ = 2400kg/m ³ ; water flow q _w = 24m ³ /d, specific heat c _w = 4.187kJ/(kg°C), density ρ _w = 1000kg/m ³ .

A method for determining the embedding position of a thermometer in a concrete pouring silo containing a cooling water pipe, the method comprising the following steps:

Step 1: Establish a concrete model with cooling water pipes, use the water pipe cooling finite element method to simulate the temperature field, and obtain the temperature field of the concrete model with cooling water pipes,

In actual concrete dam engineering, the cooling water pipes in the concrete pouring silo are generally arranged in a serpentine shape, as shown in Figure 1, the planes AB and CD along the flow direction are approximately symmetrical planes, which can be considered as adiabatic boundary planes, as Therefore, a concrete prism model containing cooling water pipes is established, as shown in Figure 2.

Assuming that the length of the concrete prism is L=100m, four different cross-sectional dimensions of the prism are designed, which are

The first type: width × height = 1m × 1m

The second type: width × height = 1.5m × 1.5m

The third type: width × height = 1m × 1.5m

The fourth type: width × height = 2m × 1.5m, a cooling water pipe with an outer diameter of = 32mm is arranged in the direction of the center of the concrete prism cross section,

That is, the horizontal spacing of the first type of prism cooling water pipe is 1m, and the vertical spacing is 1m;

The horizontal spacing of the second prism cooling water pipe is 1.5m, and the vertical spacing is 1.5m;

The horizontal spacing of the third type of prism cooling water pipe is 1m, and the vertical spacing is 1.5m;

The horizontal spacing of the fourth prism cooling water pipe is 2m, and the vertical spacing is 1.5m.

The finite element mesh of the prism section is shown in Figure 3-6.

Assuming that the six surfaces of the concrete prism are all adiabatic boundaries, the initial temperature of the concrete is 10°C, and the inlet temperature of the cooling water is 10°C.

The water pipe cooling finite element method is used to simulate the temperature field during the water cooling period. The water flow start time is 1d, and the water flow is continued for 10d.

The average temperature history of the concrete model with cooling water pipes is calculated by formula (1):

Assuming time t, the average temperature T _ave (t) of the concrete pouring silo during water cooling is

In the formula: T _g (t) is the temperature of the unit Gauss point at time t; V _g is the occupied volume of the unit Gauss point, which can be calculated by using the Jacobian determinant |J| of the Gauss point; Accumulate for the unit Gauss point; Accumulated for the pouring bin unit; The volume of the concrete pouring chamber to remove the volume occupied by the water pipes;

The average temperature process line of the concrete prism drawn from the calculation results of formula (1) is shown in Figure 7.

Step 2: Select the 50m section in the middle of the concrete prism for analysis. Since the six surfaces of the prism are insulated, the temperature field of the section is symmetrically distributed. Therefore, the temperature field of the 1/4 section is analyzed.

From the node temperature of the section element, the shape function is used to obtain the temperature of any point of the section

The temperature at any point in the concrete pouring silo is

In the formula, N _i (x, y, z) is the shape function, T _i (t) is the temperature of node i at time t;

In the finite element calculation of water pipe cooling, the concrete prism adopts hexahedral 8-node elements, and the middle section is a quadrilateral 4-node element. It is inconvenient to calculate the temperature at any point of the section by formula (2). In order to obtain the temperature at any point in the section from the node temperature, a quadrilateral 12-node element is introduced, and the calculation of the temperature at any point in the section is simplified by replacing the quadrilateral 4-node isoparametric element with the quadrilateral 12-node isoparametric element. The results are shown in Figure 8-11 .

According to the simulation calculation results of the temperature field, the upper and lower limits of the quadrilateral 12-node unit are given, and the quadrilateral 12-node unit area contains 9 quadrilateral 4-node units.

Taking Figure 8 as an example, the temperature history of four points A, B, C, and D in the quadrilateral element is calculated by using the quadrilateral 12-node isoparametric element shape function, and it is compared with the node temperature history calculated by the temperature field simulation. As shown in Figure 12.

From the analysis in Figure 12, it can be seen that the temperature difference distribution of the four points A, B, C and D in the width × height = 1m × 1m section unit is within the range of [-0.01,0.06], and the calculation error is within 0.03%. Therefore, It is feasible to use quadrilateral 12-node isoparametric elements instead of quadrilateral 4-node isoparametric elements to simplify the calculation of temperature at any point in the section.

Therefore, formula (2) is extended into formulas (4) and (5)

The temperature at any point of the section obtained by introducing a quadrilateral 12-node isoparametric element is

where T _i (t) is the corresponding nodal temperature, N _i (ξ,η) is the shape function of the quadrilateral 12-node isoparametric element, which is

Step 3: From the average temperature history T _ave (t) of the concrete model containing the cooling water pipe obtained in step 1 and the temperature T(x, y, z, t) at any point obtained in step 2, an optimal model for the geometric position of the thermometer is established,

The optimal analysis of the geometric position of the thermometer shows that the temperature history of multiple geometric positions on the section is close to the average temperature history of the pouring chamber. For this reason, adopt the value of fixed n, specifically get n '=-1,-0.9,-0.8,-0.7,-0.6,-0.5,-0.4,-0.3,-0.2,-0.1, 0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, 0.8, 0.9, 1.0, and then use the one-dimensional optimization search method to optimize ξ. At this time, the preferred mathematical form of the geometric position of the thermometer is

Find ξ

Make

Satisfy the constraints: -1≤ξ≤1

Among them, Num is determined by the time step calculated by temperature field simulation. Since in the simulation analysis, the time step of the first 11d is 0.1d, and the time step of 11~41d is 0.5d, therefore, Num is taken as 170 in this analysis.

Since when η′ is fixed, there does not necessarily exist a corresponding ξ to ensure that f(ξ)→min in formula (6), therefore, this analysis adopts the dual optimization control standard of minimum error and maximum optimization times.

Step 4: Use the optimization algorithm to solve the optimal model of the geometric position of the thermometer, and obtain the optimal geometric position coordinates of the buried thermometer.

Use the one-dimensional optimization search method to optimally solve formula (6), obtain the geometric position ξ-η value of the thermometer, and then use the following formula to obtain the x-y coordinate value

In the formula, x _i and y _i are the coordinates of node i respectively.

The geometric position distribution diagram drawn by the geometric positions of the four prism cooling water pipes obtained by the above formula (7) is shown in Figure 13-16. It can be seen from Figure 13-14 that the first, second and fourth types The geometric position distribution of the prism cross-section thermometer is a parabolic distribution, and the geometric position distribution of the third prism cross-section thermometer is approximately a linear distribution.

In the actual concrete dam project, according to the water pipe spacing of the concrete pouring silo, a thermometer is buried at the above optimal geometric position, and the measured temperature history of the thermometer can better represent the average temperature history of the concrete pouring silo.

Claims (3)

1. a kind of method for determining thermometer burial place in concrete pouring bin containing cooling water pipe, it is characterised in that this method bag Include following steps：

Step 1：The concrete prism body Model containing cooling water pipe is set up, Temperature Field Simulation is carried out using water pipe cooling FInite Element Calculate, obtain the concrete prism model temperature containing cooling water pipe,

The mean temperature course for obtaining the concrete prism body Model containing cooling water pipe is calculated by formula (1)：

If t, mean temperature T of the concrete pouring bin when water flowing is cooled down_ave(t) it is

In formula：T_g(t) it is t unit Gauss point temperature；V_gFor unit Gauss point possessive volume, refined using the Gauss point can Than determinant | J | calculating is obtained；It is cumulative for unit Gauss point；It is cumulative to pour warehouse receipt member；For except outlet pipe institute Account for the concrete pouring bin volume of volume；

Step 2：The intermediate cross-section of the body Model of concrete prism containing cooling water pipe is chosen, by section units node temperature, using shape Function obtains section arbitrfary point temperature：

The temperature of arbitrfary point is in concrete pouring bin

In formula, N_i(x, y, z) is shape function, T_i(t) it is t node i temperature；

Step 3：The concrete prism body Model mean temperature course T containing cooling water pipe obtained by step 1_ave(t) with step 2 Obtained arbitrfary point temperature T (x, y, z, t), sets up thermometer geometric position optimization model, the number of thermometer geometric position preferably Form is

Seek ξ

Make

Meet constraints：-1≤ξ≤1；Wherein, Num is the time step that is calculated by Temperature Field Simulation to determine；

Step 4：Thermometer geometric position optimization model is solved using the optimized algorithm of belt restraining, acquisition thermometer is buried optimal Geometric position coordinate.

2. a kind of side for determining thermometer burial place in concrete pouring bin containing cooling water pipe according to claim 1 Method, it is characterised in that：In step 1, the cooling water pipe in concrete pouring bin uses snakelike arrangement, sets up mixed containing cooling water pipe Solidifying soil prism body Model is the concrete prism body Model containing cooling water pipe.

3. a kind of side for determining thermometer burial place in concrete pouring bin containing cooling water pipe according to claim 1 Method, it is characterised in that：Concrete prism uses the node unit of 6 face body 8, then intermediate cross-section is the node unit of quadrangle 4, is introduced The node unit of quadrangle 12, by simplifying section by the node isoparametric elements of the quadrangle 12 replacement node isoparametric elements of quadrangle 4 Interior arbitrfary point temperature computation.