CN102721480B - Method for calculating equivalent temperature field of large-size concrete based on cooling water monitoring - Google Patents

Abstract

The invention discloses a method for calculating an equivalent temperature field of large-size concrete based on cooling water monitoring, and relates to a method for monitoring cooling water and a method for calculating an equivalent field in the period of constructing large-size concrete. Based on the prior art, by laying related monitoring instruments and combining a database technology, the invention provides a method for calculating heat absorbed by a cooling water pipe and realizes the emulational simulated calculation of the equivalent temperature field of concrete in the construction period. The full-process monitoring, data management, calculation and simulation system of the cooling water of a concrete engineering is provided by the method, and the temperature developing state of the large-size concrete in the construction period can be deeply known under the direction of the method.

Description

The method of the calculating mass concrete equivalent temperature field based on cooling water flowing monitoring

Technical field

The present invention relates to the monitoring method to cooling water flowing and the calculating analogy method to equivalent temperature field during a kind of mass concrete construction.

Background technology

Lay cooling water pipe as important measures in mass concrete temperature control, can effectively limit the temperature peak of inside concrete, control the evolution of temperature, in modernization mass concrete construction, playing the part of indispensable role.A large amount of scholars had once carried out the correlative study to its computing method, wherein, in the world take united states bureau of reclamation as representative, a series of length of having derived in the process of construction on the early stage large-sized concrete dams such as Hu Buddhist gravity-arch dam is buried Theoretical Solution (the Bureau of Reclamation of water pipe problem, Cooling of concrete dams:final reports, Bureau of Reclamation, 1949), domestic take Zhu Baifang as representative, cooling equivalent heat conduction equation (the Zhu Baifang of water pipe has been proposed, consider the concrete equivalent heat conduction equation of water pipe cooling effect, Journal of Hydraulic Engineering, 1991) and Finite Element Method (ZHU Bofang, CAI Jianbo, Finite element analysis of effect of pipe cooling in concrete dams, Journal of Construction Engineering and Management, 1989) etc., in engineering field, be widely applied.On the basis of above-mentioned work, some scholars have also proposed a series of improvement to the Calculation Method of Temperature Field of the mass concrete of considering cooling water pipe.(Liu Ning, Liu Guangting etc., the finite element minor structure analogue technique of water pipe cooling effect, Journal of Hydraulic Engineering, 1997; Myers T, Fowkes N, Ballim Y.Modeling the Cooling of Concrete by Piped Water, Journal of Engineering Mechanics, 2009; Kim JK, Kim KH, Yang JK, Thermal analysis of hydration heat in concrete structures with pipe-cooling system, Computers & Structures, 2001; Jian Yang, Yu Hu, Zheng Zuo, Thermal analysis of mass concrete embedded with double-layer staggered heterogeneous cooling water pipes, Applied Thermal Engineering, 2012)

Traditionally, due to the restriction of construction cost, technical merit, monitoring project to construction time mass concrete is limited, and cooling message context is monitoring and the data application method of a cover system maturation not, and most of engineering was only controlled the temperature of cooling water source in the past roughly.The above-mentioned computing method of mentioning are also based on this, and these computing method are by setting up the thermally conductive relation of concrete temperature and inlet water temperature, theoretical derive or simplify solve to obtain the heat taken away of rising pipe.Owing in derivation, some conditions being supposed, the accuracy of calculating depends on choosing of calculating parameter to a great extent.

The temperature control that is accompanied by modern mass concrete engineering becomes more meticulous, the development trend of quality management process, also progressively abundant to the Contents for Monitoring of cooling water flowing information, realization hinders without technology to the omnidistance Simultaneous Monitoring of water inlet, leaving water temperature, but how correctly monitoring and these data of application, not yet have clear and definite standard and flow process to carry out systematic direction.

Summary of the invention

The object of this invention is to provide a kind of method of the calculating mass concrete equivalent temperature field based on cooling water flowing monitoring, thereby can realize the analog computation to construction time concrete temperature field.

The object of the invention is to be achieved through the following technical solutions, this scheme comprises the steps:

1) building database structure: database structure comprises concrete material information table, concreting information table, cooling water flowing record sheet and computing information table;

2) record by experiment at least one concrete material number, specific heat, density, coefficient of heat conductivity and the hydration heat parameter in engineering, used, and be input in concrete material information table;

3), in work progress, when building each concrete storehouse, record its concrete storehouse number, material number, build the time, build temperature and build volume, and be input in concreting information table;

4) setting data acquisition time step delta τ, monitors the cooling water flowing of concrete construction phase by following two kinds of technological means:

I) at the cooling water pipe in each concrete storehouse, import and export position and lay digital temperature sensor and digital flowmeter, digital flowmeter adopts the digital flowmeter with two-way measurement of discharge function, or adopt two not unidirectional digital flowmeters in the same way, and be connected on industrial computer by data line, according to Δ τ, gather and import and export water flowing temperature and water flowing flow q _w, water temperature is low is set as import water flowing temperature T _w-in, water temperature is high is set as exporting water flowing temperature T _w-out, and by concrete storehouse number, Measuring Time τ, import water flowing temperature T _w-in, outlet water flowing temperature T _w-outwith water flowing flow q _wbe input in cooling water flowing record sheet;

Ii) at the cooling water pipe in each concrete storehouse, import and export position and lay water swivel and water meter, according to the Δ τ manual read meter reading of fetching water, record τ _wthe water yield V that in time, water meter increases _w, calculate water flowing flow

manually open the water swivel of water inlet pipe and water outlet pipe, utilize thermometer measure to import and export water flowing temperature, water temperature is low is set as import water flowing temperature T _w-in, water temperature is high is set as exporting water flowing temperature T _w-out, and by concrete storehouse number, Measuring Time τ, import water flowing temperature T _w-in, outlet water flowing temperature T _w-outwith water flowing flow q _wbe input in cooling water flowing record sheet;

5) calculate the absorption heat speed on each Measuring Time τ

${\stackrel{\·}{Q}}^{-}\left(\mathrm{\τ}\right)={\mathrm{\ρ}}_w{c}_w[T_{w-\mathrm{in}}\left(\mathrm{\τ}\right)-T_{w-\mathrm{out}}\left(\mathrm{\τ}\right)]q_w\left(\mathrm{\τ}\right)---\left(a\right)$

Wherein, ρ _wrepresent the density of water, c _wrepresent specific heat of water, T _w-in(τ), T _w-out(τ) and q _w(τ) represent respectively import water flowing temperature, outlet water flowing temperature and the water flowing flow of Measuring Time τ, formula (a) is calculated

be input in computing information table with concrete storehouse number, Measuring Time τ;

6) based on absorbing heat speed utilize formula (b), by Finite Element Method or method of finite difference, the equivalent temperature field of mass concrete solved:

$\frac{\∂T}{\∂t}=\frac{{\mathrm{\λ}}_c}{{\mathrm{\ρ}}_c{c}_c}(\frac{{\∂}^{2}T}{{\∂x}^2}+\frac{{\∂}^{2}T}{{\∂y}^2}+\frac{{\∂}^{2}T}{{\∂z}^2})+\frac{\mathrm{d\θ}\left(t\right)}{\mathrm{dt}}+\frac{{\stackrel{\·}{Q}}^{-}\left(t\right)}{{\mathrm{\ρ}}_c{c}_c{V}_c}---\left(b\right)$

Wherein, the meaning of each symbol is: T is concrete temperature, and t is the time, and x, y, z is rectangular coordinate system, λ _cfor concrete coefficient of heat conductivity, ρ _cfor concrete density, c _cfor concrete specific heat, V _cfor the volume in concrete storehouse,

time absorption heat speed, θ (t) is hydration heat function.

The present invention, compared with conventional art, has the following advantages and high-lighting effect:

The present invention is on the basis of conventional art, to construction period, the cooling water flowing of mass concrete has realized omnidistance monitoring, the method of the calculating mass concrete equivalent temperature field based on cooling water flowing monitoring proposing in conjunction with database technology, can accurately obtain the absorption heat of water pipe, during without pre-treatment, set up complicated model, for the temperature state of development of understanding construction time mass concrete provides theoretical foundation.

Accompanying drawing explanation

Fig. 1 is cooling water-flowing data library structure composition schematic diagram.

Fig. 2 is the cooling water flowing monitoring system layout figure that adopts digital flowmeter.

Fig. 3 is the cooling water flowing monitoring system layout figure that adopts manual type.

Fig. 4 is the absorption heat rate calculations result figure in embodiment.

Fig. 5 is the finite element grid illustraton of model in embodiment, and in figure, dimensional units is m.

Fig. 6 is accounting temperature in embodiment and the comparison diagram of observed temperature.

Wherein: 1-concrete storehouse; 2-inside concrete cooling water pipe; 3-water inlet pipe; 4-rising pipe; 5-digital temperature sensor; 6-digital flowmeter; 7-water swivel; 8-water meter; 9-industrial computer (data acquisition unit); 10-data bus connection.

Embodiment

Below in conjunction with accompanying drawing, further illustrate embodiments of the present invention:

1) model database structure, database structure comprises concrete material information table, concreting information table, cooling water flowing record sheet and computing information table, as shown in Figure 1, what in figure, underscore represented is the major key in this table to Information Organization form in each tables of data.

2) record by experiment at least one concrete material number, specific heat, density, coefficient of heat conductivity and the hydration heat parameter in engineering, used, and be input to concrete material information table; Wherein, by relevant determining instrument, in shop experiment, can record specific heat, density, coefficient of heat conductivity, by adiabatic temperature rise, test and can record hydration heat curve, carry out obtaining relevant hydration heat parameter after certain matching, in common engineering, the hydration heat curve of exponential form is more,

θ(τ)=θ ₀(1-e ^-mτ) (a)

Wherein, θ (τ) is the τ hydration heat temperature rise value in the length of time, θ ₀for final thermal insulation temperature rise, m hydration heat rate constant; Obtain after above-mentioned information, be recorded in concrete material information table;

3) in work progress, when building each concrete storehouse, record its concrete storehouse number, material number, build the time, build temperature and build volume, and be input to and build information table;

4) the acquisition time step delta τ of setting Monitoring Data, is generally taken as 1d, or 6h, by following two kinds of technological means, the cooling water flowing of concrete construction phase is monitored:

I) the abundant words of economic condition, at the cooling water pipe in each concrete storehouse, import and export position and lay digital temperature sensor and digital flowmeter, as shown in Figure 2, and data line is connected on industrial computer, to realize remote automatic data acquisition, it should be noted that, because cooling water flowing needs timing reversing, flowmeter herein requires to have the function of two-way measurement of discharge, otherwise two not one-way flow meters in the same way or pipeline, flowmeter are carried out to other transformation can be set, so that it possesses the measurement capability to forward and reverse water flowing; By programming, make it according to the time step Δ τ setting, realize and automatically gather import and export water flowing temperature and water flowing flow q _w, owing to there being water flowing commutation, reading two water temperature value that obtain at every turn and should judge magnitude relationship, water temperature is low is set as import water flowing temperature T _w-in, water temperature is high is set as exporting water flowing temperature T _w-out, the value that deposits database in should meet T _w-in<T _w-out; And by concrete storehouse number, Measuring Time τ, import water flowing temperature T _w-in, outlet water flowing temperature T _w-outwith water flowing flow q _wautomatic input is to the cooling information recording table of the water flowing in database;

Ii) as economic condition is more nervous, at the cooling water pipe in each concrete storehouse, import and export position and lay water swivel and water meter, as shown in Figure 3, according to the time step Δ τ setting, manual read's meter reading of fetching water, records certain hour τ _wthe water yield V that interior water meter increases _w, calculated flow rate

manually open the water swivel of water inlet pipe and water outlet pipe, utilize mercury thermometer to measure and import and export water temperature, owing to there being water flowing commutation, should judge the magnitude relationship that reads two water temperature value that obtain, water temperature is low is set as import water flowing temperature T _w-in, water temperature is high is set as exporting water flowing temperature T _w-out, accurate recording is on record, and by concrete storehouse number, Measuring Time τ, import water flowing temperature T _w-in, outlet water flowing temperature T _w-outwith water flowing flow q _wbe input to the cooling information recording table of water flowing in database;

5) calculate the absorption heat speed on each Measuring Time τ

${\stackrel{\&CenterDot;}{Q}}^{-}\left(\mathrm{\&tau;}\right)={\mathrm{\&rho;}}_w{c}_w[T_{w-\mathrm{in}}\left(\mathrm{\&tau;}\right)-T_{w-\mathrm{out}}\left(\mathrm{\&tau;}\right)]q_w\left(\mathrm{\&tau;}\right)---\left(b\right)$

Wherein, ρ _wrepresent the density of water, generally get 1000kg/m ³, c _wrepresent specific heat of water, generally get 4.183kJ/kg ° of C, T _w-in(τ), T _w-out(τ) and q _w(τ) represent respectively import water flowing temperature, outlet water flowing temperature and the water flowing flow of Measuring Time τ,

Above formula is calculated

according to Measuring Time, deposit in computing information table, here

should be negative value, represent concrete within the unit interval, be cooled water pipe absorb heat;

6) based on absorbing heat speed

utilize following formula, by Finite Element Method or method of finite difference, the equivalent temperature field energy of mass concrete enough solved:

$\frac{\&PartialD;T}{\&PartialD;t}=\frac{{\mathrm{\&lambda;}}_c}{{\mathrm{\&rho;}}_c{c}_c}(\frac{{\&PartialD;}^{2}T}{{\&PartialD;x}^2}+\frac{{\&PartialD;}^{2}T}{{\&PartialD;y}^2}+\frac{{\&PartialD;}^{2}T}{{\&PartialD;z}^2})+\frac{\mathrm{d\&theta;}\left(t\right)}{\mathrm{dt}}+\frac{{\stackrel{\&CenterDot;}{Q}}^{-}\left(t\right)}{{\mathrm{\&rho;}}_c{c}_c{V}_c}---\left(c\right)$

Wherein, the meaning of each symbol is: T is concrete temperature, and t is the time, λ _cfor coefficient of heat conductivity, ρ _cfor concrete density, c _cfor concrete specific heat, V _cfor the volume in concrete storehouse,

absorption heat speed while representing τ=t, is obtained by the computing information table in database, θ (t) hydration heat function, concrete functional form is by step 2) middle decision, concrete parameter can be by obtaining in concrete material information table; Above-mentioned equivalent temperature field refers to consider the concrete temperature field of water pipe cooling effect in average meaning.

Utilize above-mentioned fundamental formular, can solve mass concrete equivalent temperature field, take finite element method as example, on the basis of conventional heat conduction problem of not considering cooling water pipe and aquation thermal source, each concrete unit is considered to a thermal source item can realize the calculating that solves to mass concrete equivalent temperature field.

Based on absorbing heat speed

can also calculate or thermal parameters is carried out to back analysis the medial temperature in concrete storehouse:

Ignore the impact of border radiating condition, utilize formula (d) can carry out approximate treatment to the medial temperature in concrete storehouse:

$T_m(t+\mathrm{\&Delta;t})=T_m\left(t\right)+{\mathrm{\&theta;}}^{\&prime;}\left(t\right)\mathrm{\&Delta;t}+{\stackrel{\&CenterDot;}{Q}}^{-}\left(t\right)\mathrm{\&Delta;t}/{\mathrm{\&rho;}}_c{c}_c{V}_c---\left(d\right)$

Wherein, Δ t represents step-length computing time, T _m(t), T _m(t+ Δ t) represents the concrete storehouse medial temperature of t, t+ Δ t time, and θ ' (t) represents the derivative of hydration heat function at time t; During calculating, from the time of building, start to calculate, initial temperature is decided to be builds temperature, builds the time, builds temperature by obtaining in concreting information table; In above formula, ignored the impact of border radiating condition, for the medial temperature of inside, concrete storehouse, affected less;

The project situation it be unclear that for some thermal parameters, or wish is further found out the concrete thermal parameters of engineering site, can be by bury concrete measuring temperature sensor underground in concrete storehouse, choose some groups of different thermal parameters groups, utilize formula (d), calculate respectively, relatively result of calculation and the observed temperature result of different parameters group, what approach the most is required thermal parameters group, as possess certain mathematical tool, also can adopt the methods such as neural network further to analyze the above results.

Embodiment

In concrete enforcement, for a concrete storehouse in certain construction time large-sized concrete dam engineering, launched correlation test, this storehouse concreting volume 4358m ³, in the import and export position of this storehouse cooling water pipe, laid water swivel and water meter, after build in this storehouse certainly, the water flowing temperature and the water flowing flow that within every 6 hours, arrange monitoring personnel manually to gather import and export, place on record, returns subsequently in office's input database.Test period, from building the date, is only built latter 237 days to this storehouse.

To the concrete shop experiment of this project, recording concrete specific heat is 0.985kJ/kg ° of C, and density is 2663kg/m ³, coefficient of heat conductivity is 7.70kJ/mh ° of C, due to the flyash that contains certain parameter in the match ratio adopting, test records hydration heat curve and adopts two exponential form fitting effect better,

wherein, θ ₁=24.0, m ₁=0.392, θ ₂=12.5, m ₂=0.105.

Utilize

can, by the cooling water flowing recorded information in database, automatically calculate the absorption heat speed of each Measuring Time point, and the computing information table in automatic updating data storehouse, duration of test

result of calculation as shown in Figure 4.

Adopt finite element software, to this Practical Project problem modeling and according to the method for the calculating mass concrete equivalent temperature field based on cooling water flowing monitoring, solve, the finite element software adopting is MSC.Marc, utilizes thermal source interface flux.f wherein, by thermogenetic the aquation of each incremental step heat with

as thermal source, add on each concrete unit.

As shown in Figure 5, Tu Zhong unit is m to finite element grid model in this example, divides altogether 756 of hexahedral elements, and 1064 of nodes are built latter 22 days internal upper part surface exposures, are made as the radiating condition to air, and temperature is taken from local field data.

For the correctness of the result, in this storehouse concrete, to have buried temperature sensor underground concrete internal temperature has been monitored, monitoring result is input in database.

Export the Time-temperature result of this storehouse inside concrete point, and contrast with the measured result that monitoring obtains, the two is basically identical, as shown in Figure 6, correctness and the feasibility of the method for the calculating mass concrete equivalent temperature field based on cooling water flowing monitoring has been described.

Claims (2)

1. a method for the calculating mass concrete equivalent temperature field based on cooling water flowing monitoring, is characterized in that the method comprises the steps:

1) building database structure: database structure comprises concrete material information table, concreting information table, cooling water flowing record sheet and computing information table;

2) record by experiment at least one concrete material number, specific heat, density, coefficient of heat conductivity and the hydration heat parameter in engineering, used, and be input in concrete material information table;

3), in work progress, when building each concrete storehouse, record its concrete storehouse number, material number, build the time, build temperature and build volume, and be input in concreting information table;

4) setting data acquisition time step delta τ, the cooling water flowing by any in following two kinds of technological means to the concrete construction phase is monitored:

I) at the cooling water pipe in each concrete storehouse, import and export position and lay digital temperature sensor and digital flowmeter, and be connected on industrial computer by data line, according to Δ τ, gather and import and export water flowing temperature and water flowing flow q _w, water temperature is low is set as import water flowing temperature T _w-in, water temperature is high is set as exporting water flowing temperature T _w-out, and by concrete storehouse number, Measuring Time τ, import water flowing temperature T _w-in, outlet water flowing temperature T _w-outwith water flowing flow q _wbe input in cooling water flowing record sheet;

Ii) at the cooling water pipe in each concrete storehouse, import and export position and lay water swivel and water meter, according to the Δ τ manual read meter reading of fetching water, record τ _wthe water yield V that in time, water meter increases _w, calculate water flowing flow manually open the water swivel of water inlet pipe and water outlet pipe, utilize thermometer measure to import and export water flowing temperature, water temperature is low is set as import water flowing temperature T _w-in, water temperature is high is set as exporting water flowing temperature T _w-out, and by concrete storehouse number, Measuring Time τ, import water flowing temperature T _w-in, outlet water flowing temperature T _w-outwith water flowing flow q _wbe input in cooling water flowing record sheet;

5) calculate the absorption heat speed on each Measuring Time τ

${\stackrel{.}{Q}}^{-}\left(\mathrm{\&tau;}\right)={\mathrm{\&rho;}}_w{c}_w[T_{w-\mathrm{in}}\left(\mathrm{\&tau;}\right)-T_{w-\mathrm{out}}\left(\mathrm{\&tau;}\right)]q_w\left(\mathrm{\&tau;}\right)---\left(a\right)$

Wherein, ρ _wrepresent the density of water, c _wrepresent specific heat of water, T _w-in(τ), T _w-out(τ) and q _w(τ) represent respectively import water flowing temperature, outlet water flowing temperature and the water flowing flow of Measuring Time τ, formula (a) is calculated

be input in computing information table with concrete storehouse number, Measuring Time τ;

6) based on absorbing heat speed

utilize formula (b), by Finite Element Method or method of finite difference, the equivalent temperature field of mass concrete solved:

$\frac{\&PartialD;T}{\&PartialD;t}=\frac{{\mathrm{\&lambda;}}_c}{{\mathrm{\&rho;}}_c{c}_c}(\frac{{\&PartialD;}^{2}T}{\&PartialD;x^2}+\frac{{\&PartialD;}^{2}T}{\&PartialD;y^2}+\frac{{\&PartialD;}^{2}T}{\&PartialD;z^2})+\frac{\mathrm{d\&theta;}\left(t\right)}{\mathrm{dt}}+\frac{{\stackrel{.}{Q}}^{-}\left(t\right)}{{\mathrm{\&rho;}}_c{c}_c{V}_c}---\left(b\right)$

Wherein, the meaning of each symbol is: T is concrete temperature, and t is the time, and x, y, z is rectangular coordinate system, λ _cfor concrete coefficient of heat conductivity, ρ _cfor concrete density, c _cfor concrete specific heat, V _cfor the volume in concrete storehouse, absorption heat speed during for τ=t, θ (t) is hydration heat function.

2. according to the method for the calculating mass concrete equivalent temperature field based on cooling water flowing monitoring claimed in claim 1, it is characterized in that: described digital flowmeter adopts the digital flowmeter with two-way measurement of discharge function, or adopt two not unidirectional digital flowmeters in the same way.

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