CN107907412A - A kind of method for measuring concrete surface drying shrinkage stress - Google Patents

A kind of method for measuring concrete surface drying shrinkage stress Download PDF

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Publication number
CN107907412A
CN107907412A CN201711121439.XA CN201711121439A CN107907412A CN 107907412 A CN107907412 A CN 107907412A CN 201711121439 A CN201711121439 A CN 201711121439A CN 107907412 A CN107907412 A CN 107907412A
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mrow
concrete
msub
temperature
drying shrinkage
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刘毅
张国新
王振红
辛建达
朱振泱
刘有志
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China Institute of Water Resources and Hydropower Research
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China Institute of Water Resources and Hydropower Research
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    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/08—Investigating strength properties of solid materials by application of mechanical stress by applying steady tensile or compressive forces
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N17/00—Investigating resistance of materials to the weather, to corrosion, or to light
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N3/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N3/02—Details
    • G—PHYSICS
    • G01—MEASURING; TESTING
    • G01N—INVESTIGATING OR ANALYSING MATERIALS BY DETERMINING THEIR CHEMICAL OR PHYSICAL PROPERTIES
    • G01N2203/00—Investigating strength properties of solid materials by application of mechanical stress
    • G01N2203/02—Details not specific for a particular testing method
    • G01N2203/022—Environment of the test
    • G01N2203/0222—Temperature

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Abstract

A kind of method for measuring concrete surface drying shrinkage stress, concrete is stirred according to proportioning, pours into template, keeps test specimen upper surface exposed, the drying shrinkage produced with simulated environment factor on test specimen influences；Temperature sensor is inserted into respectively in the middle part of test specimen in trisection point, and environmental cabinet thermometer hole, humidity sensor is placed in environmental cabinet；Displacement sensor is installed in the middle part of test specimen, and is fixed with positioning tool, keeps its position constant；The test parameters such as corresponding environmental cabinet epidemic disaster and constrained parameters are set in software test interface, true environment is simulated；Positioning tool is removed after concrete final set, starts to test, measures the drying shrinkage stress data of concrete；Drying shrinkage or bulking factor are calculated according to formula, the drying shrinkage stress development course of concrete is calculated according to formula.The present invention can test surface drying shrinkage stress of the concrete under the conditions of actual environment condition Change and Development, produce to grasp mechanical performance of concrete and crack preventing and provide reliable basis.

Description

A kind of method for measuring concrete surface drying shrinkage stress
Technical field
The invention belongs to the technical field of hydraulic and hydroelectric engineering, particularly a kind of side for measuring concrete surface drying shrinkage stress Method.
Background technology
The crack problem of mass concrete always perplexs an important problem of domestic and international project circle, distress in concrete Appearance, not only affect the presentation quality of structure, also drastically influence the service life and safety of engineering, and then threaten people The lives and properties of the people.Therefore, the possibility for how avoiding the generation in crack or reducing crack generation just becomes engineering construction person institute Concern, particularly large volume concrete structural, thermal cracking is main crack form.Up to now, to large volume The thermal cracking of concrete prevents from mainly in terms of following three setting about：(1) optimised coagulation soil structure, improves mechanical characteristic；(2) material Improved in terms of material, optimised coagulation soil match ratio, improve the material property of concrete, it is true to grasp concrete heat mechanical characteristic；(3) Working measure is taken, reduces concrete temperature, prevents concrete from producing the excessive temperature difference.
For concrete for hydraulic structure, its surface inside 10-15cm thickness ranges concrete generally be referred to as surface coagulation Soil.Engineering experience shows that the drying shrinkage stress of concrete surface is the main reason for causing concrete surface crack, particularly to construct The drying shrinkage stress of phase concrete, it is easier to cause the generation of surface crack, threaten the appearance and construction quality of works.End mesh Before, the shrinkage performance of concrete is tested simply by drying shrinkage (bulking), measure concrete under no external load and constant temperature by Yu Gan, wet caused axial length deformation, with the drying shrinkage of more different concrete and bulking performance.But current device and Method cannot directly measure the drying shrinkage stress of concrete, can not consider influence of the engineering actual temperature change to drying shrinkage stress. Therefore, it is badly in need of a kind of new test method, directly measures concrete surface drying shrinkage stress.
The content of the invention
The object of the present invention is to provide a kind of method for measuring concrete surface drying shrinkage stress, it can improve existing water conservancy project The limitation and deficiency of concrete surface drying shrinkage stress test method, to surface drying shrinkage of the concrete under temperature change development condition Stress is tested, and is produced to grasp mechanical performance of concrete and crack preventing and is provided reliable basis.
To achieve the above object, the present invention takes following technical scheme：
A kind of method for measuring concrete surface drying shrinkage stress, it utilizes an experimental rig, which includes one Base, is provided with an environmental cabinet for being used to completely cut off external environment on the base, and dress is housed equipped with concrete sample in the environmental cabinet Put；
The concrete sample accommodating device includes fixed chuck, active chuck, two side templates, and split forms a upper end The open accommodating space of open or upper and lower side, the fixed chuck are fixed at the environmental cabinet one end, which can The environmental cabinet other end is movably arranged at along the axis of the length direction of the accommodating space, and two side templates are parallel, and to be placed in this solid Between clamp head and active chuck；The environmental cabinet or the environmental cabinet and the accommodating space set temperature sensor and humidity sensor Device；The environmental cabinet and concrete sample accommodating device are additionally provided with temperature-adjusting device and humidity control apparatus；
Further include a loading system；The loading system includes a reaction frame, a transmission device and one carries gear reducer Servomotor, the reaction frame are fixedly installed on the base, which are surrounded；The transmission device includes being arranged on the counter-force Active leading screw on frame, the active leading screw end connection constraints axis, the constraint axis are worn and the work through the environmental cabinet and end Dynamic collet connection, and the active chuck position is fixed or is moved in the axis direction；The servomotor and the active leading screw Connection；Measurement top is equipped with the top of the constraint axis, displacement sensor is equipped between the measurement top and the environmental cabinet；The transmission device is set There is strain gauge；
The temperature sensor, humidity sensor, displacement sensor, strain gauge are connected to the input of Measurement and Control System End, the temperature-adjusting device, humidity control apparatus and the servomotor are connected to the output terminal of Measurement and Control System；
Concrete raw material is stirred according to corresponding proportioning, pours into accommodating space, forms test specimen, keep test specimen upper surface Exposed, the drying shrinkage produced with simulated environment factor on test specimen influences；
Temperature sensor is inserted into respectively in the middle part of test specimen in trisection point, and environmental cabinet thermometer hole, by humidity sensor It is placed in environmental cabinet；
Displacement sensor is installed in the middle part of test specimen, and is fixed with positioning tool, keeps its position constant；
The test parameters such as corresponding environmental cabinet epidemic disaster and constrained parameters are set in software test interface, to true environment Simulated；Positioning tool is removed after concrete final set, starts to test, measures the drying shrinkage stress data of concrete；
Drying shrinkage (bulking) rate is calculated according to following equation：
εtFor t ages when drying shrinkage (bulking) rate；L0For the datum length of test specimen, mm；LtFor t ages when test specimen length, mm；Δ be metal gauge head length, mm；
The drying shrinkage stress development course of concrete is calculated according to following equation：
In formula, ti-1And tiThe respectively initial and terminal age of load time section inner concrete, h；ΔσiIt is loading specimen The stress increment obtained within the period by testing machine, MPa.
Based on above-mentioned steps, the development overall process of varying environment Under Concrete drying shrinkage stress can be obtained.
Further, it is additionally provided with the environmental cabinet in solar radiation sensor, rainfall sensor and air velocity transducer At least one, is respectively connected to the input terminal of the Measurement and Control System；Solar radiation tune is also correspondingly provided with the environmental cabinet At least one of regulating device, rainfall regulating device and wind-speed adjusting device, are respectively connected to the defeated of the Measurement and Control System Outlet；In measurement process, according to the actual change situation of construction ground illumination, rainfall and wind-force, pass through Measurement and Control System tune Save solar radiation, rainfall and the wind speed in environmental cabinet.
Further, before the test specimen is poured, " work " font is set between the fixed chuck and active chuck Locating piece, the both ends of the locating piece are fixedly connected with fixed chuck with active chuck by positioning pin respectively；And pouring examination The locating piece is removed when 3 is small after part.
Further, in the method, for the simulation of true environment, using at least one in following steps：
1. environment temperature
Depending on local situation, that is, the locality of true environment is simulated, above monthly mean temperature data is fitted to one Bar cosine curve, following formula (3) are the calculation formula after fitting：
In formula, TaFor temperature, TamFor average temperature of the whole year, AaFor temperature year luffing, τ is the time (moon), τ0For maximum temperature Time (moon).
Consider temperature diurnal variation, calculated using following formula (4)：
In formula,For daily temperature, TaFor monthly mean temperature, A is temperature diurnal variation amplitude, at the time of t is in 1 day (when) root Depending on the Various Seasonal of different regions；
2. solar radiant heat
For concrete structure often under solar radiation, it has a major impact concrete temperature.Unit The heat that solar radiation comes on unit area in time is S, wherein the part by concrete absorption is set as R, remainder quilt Reflect away, then：
R=αsS (5)
In formula, αsFor absorption coefficient, also referred to as coefficient of blackness, concrete surface generally takes 0.65.
S=S0(1kn) (6)
In formula, S0For fine day solar radiant heat, n is cloud amount, and k is coefficient, these three numerical value can be provided by local weather station.
The influence of sunshine increases Δ T equivalent to the temperature of surrounding aira,
ΔTa=R/ β (7)
In formula, β is concrete surface exothermic coefficient, can be calculated according to surface roughness and wind speed.
3. precipitation
The precipitation of engineering location meteorological department is inquired about, by precipitation apparatus and precipitation amount controller come simulated precipitation；
And precipitation is calculated by formula (8),
Ps=Pt{1-exp[-(Ta-Tr)/(Tr-Ts)]2}+, Tr≥Ts
Pr=Pt-Ps (8)
P in formulasFor snowfall, PrFor rainfall, PtFor gross precipitation, TaFor daily mean temperature, TrFor the critical temperature of rainfall, TsFor the critical temperature of snowfall.
4. wind speed
Inquire about the wind speed of the meteorological department in engineering location, threshold wind velocity simulator, to draw concrete according to wind speed Surface coefficient of heat transfer.
The beneficial effects of the invention are as follows：The method of present invention measurement concrete surface drying shrinkage stress, it can improve existing The limitation and deficiency of concrete for hydraulic structure surface drying shrinkage stress test method, to concrete in actual environment condition Change and Development condition Under surface drying shrinkage stress tested, for grasp mechanical performance of concrete and crack preventing produce provide reliably according to According to.
Brief description of the drawings
Fig. 1 is the structure diagram for the experimental provision that the method for present invention measurement concrete surface drying shrinkage stress uses.
Fig. 2 is the enlarged diagram at A in Fig. 1.
Fig. 3 is that the structure of the locating piece for the experimental provision that the method for present invention measurement concrete surface drying shrinkage stress uses is shown It is intended to.
Embodiment
Below only with the possible embodiment aspect of the embodiment explanation present invention, but and it is not used to limit the present invention and is intended to protect Category, first give chat it is bright.
As shown in Figure 1 and Figure 2, the present invention provides a kind of method for measuring concrete surface drying shrinkage stress, it utilizes an examination Experiment device, the experimental rig include a base 1, and an environmental cabinet 2 for being used to completely cut off external environment, the ring are provided with the base 1 Concrete sample accommodating device is equipped with border case 2.
The concrete sample accommodating device includes 4, two fixed chuck 3, active chuck side templates 5, and split forms one The accommodating space that upper end is open or upper and lower side is open, the fixed chuck 3 are fixed at 2 one end of environmental cabinet, the activity Collet 4 can be movably arranged at 2 other end of environmental cabinet along the axis of the length direction of the accommodating space, and two side templates 5 are flat Row is placed between the fixed chuck 3 and active chuck 4.The environmental cabinet 2 or the environmental cabinet 2 and the accommodating space set temperature pass Sensor and humidity sensor.The environmental cabinet 2 and concrete sample accommodating device are additionally provided with temperature-adjusting device and humidity regulation dress Put.
The experimental provision further includes a loading system.The loading system includes a reaction frame 6, a transmission device and a band There is the servomotor 7 of gear reducer, which is fixed on the base 1, which is surrounded.The transmission device Including the active leading screw on the reaction frame 6, the active leading screw end connection constraints axis 8, which passes through the environment Case 2 and end are worn to be connected with the active chuck 4, and causes 4 position of active chuck to fix or moved in the axis direction.This is watched Motor 7 is taken to be connected with the active leading screw.The top of constraint axis 8 is equipped with measurement top 9, is equipped between the measurement top 9 and the environmental cabinet Displacement sensor 10, the transmission device are equipped with strain gauge 11.
The temperature sensor, humidity sensor, displacement sensor 10, strain gauge 11 are connected to Measurement and Control System Input terminal, the temperature-adjusting device, humidity control apparatus and the servomotor 7 are connected to the output terminal of Measurement and Control System. In order to keep test specimen consistent, as shown in figure 3, before the test specimen is poured, set between the fixed chuck 3 and active chuck 4 The locating piece 12 of " work " font, the both ends of the locating piece are fixed with fixed chuck 3 and active chuck 4 by positioning pin respectively to be connected Connect.And the locating piece 12 is removed when after pouring test specimen 3 is small.
During measurement, concrete raw material is stirred according to corresponding proportioning, pours into accommodating space, forms test specimen, keep examination Part upper surface is exposed, and the drying shrinkage produced with simulated environment factor on test specimen influences；
Temperature sensor is inserted into respectively in the middle part of test specimen in trisection point, and environmental cabinet thermometer hole, by humidity sensor It is placed in environmental cabinet；
Displacement sensor is installed in the middle part of test specimen, and is fixed with positioning tool, keeps its position constant；
The test parameters such as corresponding environmental cabinet epidemic disaster and constrained parameters are set in software test interface, to true environment Simulated；Positioning tool is removed after concrete final set, starts to test, measures the drying shrinkage stress data of concrete；
Drying shrinkage (bulking) rate is calculated according to following equation：
εtFor t ages when drying shrinkage (bulking) rate；L0For the datum length of test specimen, mm；LtFor t ages when test specimen length, mm；Δ be metal gauge head length, mm；
The drying shrinkage stress development course of concrete is calculated according to following equation：
In formula, ti-1And tiThe respectively initial and terminal age of load time section inner concrete, h；ΔσiIt is loading specimen The stress increment obtained within the period by testing machine, MPa.
For more accurately construction simulation environment, solar radiation sensor, rainfall sensor are additionally provided with the environmental cabinet 2 At least one of with air velocity transducer, the input terminal of the Measurement and Control System is respectively connected to.Also correspondence is set in the environmental cabinet 2 There are at least one of solar radiation regulating device, rainfall regulating device and wind-speed adjusting device, be respectively connected to the measurement control The output terminal of system processed.In measurement process, according to the actual change situation of construction ground illumination, rainfall and wind-force, pass through measurement Solar radiation, rainfall and wind speed in control system adjusting ambient case 2.
In the method, for the simulation of true environment, using at least one in following steps：
1. environment temperature
Depending on local situation, that is, the locality of true environment is simulated, above monthly mean temperature data is fitted to one Bar cosine curve, following formula (3) are the calculation formula after fitting：
In formula, TaFor temperature, TamFor average temperature of the whole year, AaFor temperature year luffing, τ is the time (moon), τ0For maximum temperature Time (moon).
Consider temperature diurnal variation, calculated using following formula (4)：
In formula,For daily temperature, Ta is monthly mean temperature, and A is temperature diurnal variation amplitude, at the time of t is in 1 day (when) root Depending on the Various Seasonal of different regions；
2. solar radiant heat
For concrete structure often under solar radiation, it has a major impact concrete temperature.Unit The heat that solar radiation comes on unit area in time is S, wherein the part by concrete absorption is set as R, remainder quilt Reflect away, then：
R=αsS (5)
In formula, αsFor absorption coefficient, also referred to as coefficient of blackness, concrete surface generally takes 0.65.
S=S0(1kn) (6)
In formula, S0For fine day solar radiant heat, n is cloud amount, and k is coefficient, these three numerical value can be provided by local weather station.
The influence of sunshine increases Δ T equivalent to the temperature of surrounding aira,
ΔTa=R/ β (7)
In formula, β is concrete surface exothermic coefficient, can be calculated according to surface roughness and wind speed.
3. precipitation
The precipitation of engineering location meteorological department is inquired about, by precipitation apparatus and precipitation amount controller come simulated precipitation；
And precipitation is calculated by formula (8),
Ps=Pt{1-exp[-(Ta-Tr)/(Tr-Ts)]2}+, Tr≥Ts
Pr=Pt-Ps (8)
P in formulasFor snowfall, PrFor rainfall, PtFor gross precipitation, TaFor daily mean temperature, TrFor the critical temperature of rainfall, TsFor the critical temperature of snowfall.
4. wind speed
Inquire about the wind speed of the meteorological department in engineering location, threshold wind velocity simulator, to draw concrete according to wind speed Surface coefficient of heat transfer.
Compared with prior art, the present invention there are following advantages：
1st, under the conditions of experimental rig of the present invention can carry out a variety of temperature control measures, concrete from be poured into hardening overall process in The evolution of its own temperature stress, including drying shrinkage stress, adiabatic temperature rise, thermal coefficient of expansion, elasticity modulus and the ginseng such as creep The process that number develops with the time, can also simulate true weather environment, to the temperature stress under the influence of natural cause and cracking machine Reason is emulated.The present invention can be arranged as required to different temperature and constraint degree condition, including thermal insulation, constant temperature, setting temperature rise Temperature drop process etc., is tested by concrete cracking whole process simulation, tests the drying shrinkage stress of concrete.
2nd, experimental rig of the present invention and method, can simulate the natural environment temperature residing for concrete for hydraulic structure, and reflection is true Engineering actual environment, including day and night temperature, cold wave and solar radiation etc. draw the concrete dry under true environment temperature condition Stress under compression.
3rd, experimental rig of the present invention and method, can simulate the temperature control measures in water conservancy project concrete construction, and reflection is real The influence of artificial temperature control measures in the engineering of border, including manually the cooling of concrete, the surface heat preservation of concrete, concrete Watering cooling etc., draws the concrete dry stress under compression under the influence of temperature control measures.
4th, experimental rig of the present invention and method, can simulated environment temperature and artificial temperature control measures at the same time, reflect actual work Journey situation, draws the concrete dry stress under compression under the true condition of concrete for hydraulic structure.
5th, experimental rig of the present invention and method, can be with overall process long-time simulated environment temperature and artificial temperature control measures, instead Practical Project concrete development course is reflected, draws the drying shrinkage stress under concrete for hydraulic structure development course.
The present invention is limited with the claim.But this is based on, those of ordinary skill in the art can do Go out a variety of obvious changes or change, all should be within the main spirits and protection domain of the present invention.

Claims (4)

  1. A kind of 1. method for measuring concrete surface drying shrinkage stress, it is characterised in that it utilizes an experimental rig, experiment dress Put including a base, an environmental cabinet for being used to completely cut off external environment is provided with the base, being equipped with concrete in the environmental cabinet tries Part accommodating device；
    The concrete sample accommodating device includes fixed chuck, active chuck, two side templates, and split forms a upper end opening Or the accommodating space that upper and lower side is open, the fixed chuck are fixed at the environmental cabinet one end, which can be along this The axis of the length direction of accommodating space is movably arranged at the environmental cabinet other end, and two side templates are parallel to be placed in the geometrical clamp Between head and active chuck；The environmental cabinet or the environmental cabinet and the accommodating space set temperature sensor and humidity sensor； The environmental cabinet and concrete sample accommodating device are additionally provided with temperature-adjusting device and humidity control apparatus；
    Further include a loading system；The loading system includes a reaction frame, a transmission device and a servo with gear reducer Motor, the reaction frame are fixedly installed on the base, which are surrounded；The transmission device includes being arranged on the reaction frame On active leading screw, the active leading screw end connection constraints axis, which is worn through the environmental cabinet and end and activity folder Head connection, and the active chuck position is fixed or is moved in the axis direction；The servomotor is connected with the active leading screw； Measurement top is equipped with the top of the constraint axis, displacement sensor is equipped between the measurement top and the environmental cabinet；The transmission device is equipped with should Force snesor；
    The temperature sensor, humidity sensor, displacement sensor, strain gauge are connected to the input terminal of Measurement and Control System, The temperature-adjusting device, humidity control apparatus and the servomotor are connected to the output terminal of Measurement and Control System；
    Concrete raw material is stirred according to corresponding proportioning, pours into accommodating space, forms test specimen, keep test specimen upper surface naked Dew, the drying shrinkage produced with simulated environment factor on test specimen influence；
    Temperature sensor is inserted into respectively in the middle part of test specimen in trisection point, and environmental cabinet thermometer hole, humidity sensor is placed in In environmental cabinet；
    Displacement sensor is installed in the middle part of test specimen, and is fixed with positioning tool, keeps its position constant；
    The test parameters such as corresponding environmental cabinet epidemic disaster and constrained parameters are set in software test interface, true environment is carried out Simulation；Positioning tool is removed after concrete final set, starts to test, measures the drying shrinkage stress data of concrete；
    Drying shrinkage or bulking factor are calculated according to following equation：
    <mrow> <msub> <mi>&amp;epsiv;</mi> <mi>t</mi> </msub> <mo>=</mo> <mfrac> <mtable> <mtr> <mtd> <msub> <mi>L</mi> <mi>t</mi> </msub> </mtd> <mtd> <msub> <mi>L</mi> <mn>0</mn> </msub> </mtd> </mtr> </mtable> <mtable> <mtr> <mtd> <msub> <mi>L</mi> <mn>0</mn> </msub> </mtd> <mtd> <mrow> <mn>2</mn> <mi>&amp;Delta;</mi> </mrow> </mtd> </mtr> </mtable> </mfrac> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>1</mn> <mo>)</mo> </mrow> </mrow>
    εtFor t ages when drying shrinkage or bulking factor；L0For the datum length of test specimen；LtFor t ages when test specimen length；Δ is The length of metal gauge head；
    The drying shrinkage stress development course of concrete is calculated according to following equation：
    <mrow> <mi>&amp;sigma;</mi> <mrow> <mo>(</mo> <mi>t</mi> <mo>)</mo> </mrow> <mo>=</mo> <munderover> <mo>&amp;Sigma;</mo> <mrow> <mi>i</mi> <mo>=</mo> <mn>1</mn> </mrow> <mi>n</mi> </munderover> <msub> <mi>&amp;Delta;&amp;sigma;</mi> <mi>i</mi> </msub> <mrow> <mo>(</mo> <msub> <mi>t</mi> <mrow> <mi>i</mi> <mo>-</mo> <mn>1</mn> </mrow> </msub> <mo>,</mo> <msub> <mi>t</mi> <mi>i</mi> </msub> <mo>)</mo> </mrow> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>2</mn> <mo>)</mo> </mrow> </mrow>
    In formula, ti-1And tiThe respectively initial and terminal age of load time section inner concrete；ΔσiIt is loading specimen in the time The stress increment obtained in section by experimental rig.
  2. 2. the method for measurement concrete surface drying shrinkage stress according to claim 1, it is characterised in that in the environmental cabinet At least one of solar radiation sensor, rainfall sensor and air velocity transducer are additionally provided with, is respectively connected to the measurement control The input terminal of system processed；Solar radiation regulating device, rainfall regulating device and wind speed is also correspondingly provided with the environmental cabinet to adjust At least one of device, is respectively connected to the output terminal of the Measurement and Control System；In measurement process, according to construction ground light According to, rainfall and the actual change situation of wind-force, pass through solar radiation, rainfall and the wind in Measurement and Control System adjusting ambient case Speed.
  3. 3. the method for measurement concrete surface drying shrinkage stress according to claim 1, it is characterised in that pouring the examination Before part, the locating piece of " work " font is set between the fixed chuck and active chuck, the both ends of the locating piece respectively and Fixed chuck is fixedly connected with active chuck by positioning pin；And remove the locating piece when after pouring test specimen 3 is small.
  4. 4. the method for measurement concrete surface drying shrinkage stress according to claim 1, it is characterised in that in the method In, the simulation for true environment, using at least one in following steps：
    1. environment temperature
    Depending on local situation, that is, the locality of true environment is simulated, monthly mean temperature data is fitted to a cosine song Line, following formula (3) are the calculation formula after fitting：
    <mrow> <msub> <mi>T</mi> <mi>a</mi> </msub> <mo>=</mo> <msub> <mi>T</mi> <mrow> <mi>a</mi> <mi>m</mi> </mrow> </msub> <mo>+</mo> <msub> <mi>A</mi> <mi>a</mi> </msub> <mi>c</mi> <mi>o</mi> <mi>s</mi> <mfrac> <mi>&amp;pi;</mi> <mn>6</mn> </mfrac> <mfenced open = "(" close = ")"> <mtable> <mtr> <mtd> <mi>&amp;tau;</mi> </mtd> <mtd> <msub> <mi>&amp;tau;</mi> <mn>0</mn> </msub> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>3</mn> <mo>)</mo> </mrow> </mrow>
    In formula, TaFor temperature, TamFor average temperature of the whole year, AaFor temperature year luffing, τ is the time (moon), τ0For the time of maximum temperature (moon).
    Consider temperature diurnal variation, calculated using following formula (4)：
    <mrow> <msubsup> <mi>T</mi> <mi>a</mi> <mi>d</mi> </msubsup> <mo>=</mo> <msub> <mi>T</mi> <mi>a</mi> </msub> <mo>+</mo> <mi>A</mi> <mi> </mi> <mi>c</mi> <mi>o</mi> <mi>s</mi> <mfrac> <mi>&amp;pi;</mi> <mn>12</mn> </mfrac> <mfenced open = "(" close = ")"> <mtable> <mtr> <mtd> <mi>t</mi> </mtd> <mtd> <mn>14</mn> </mtd> </mtr> </mtable> </mfenced> <mo>-</mo> <mo>-</mo> <mo>-</mo> <mrow> <mo>(</mo> <mn>4</mn> <mo>)</mo> </mrow> </mrow>
    In formula,For daily temperature, TaFor monthly mean temperature, A is temperature diurnal variation amplitude, at the time of t is in 1 day (when) according to not Depending on Various Seasonal with area；
    2. solar radiant heat
    The heat that solar radiation comes on unit area in unit interval is S, wherein setting the part by concrete absorption as R, is remained Remaining part point is reflected, then：
    R=αs S (5)
    In formula, αsFor absorption coefficient, concrete surface takes 0.65.
    S=S0(1 kn) (6)
    In formula, S0For fine day solar radiant heat, n is cloud amount, and k is coefficient.
    The influence of sunshine increases Δ T equivalent to the temperature of surrounding aira,
    ΔTa=R/ β (7)
    In formula, β is concrete surface exothermic coefficient, is calculated according to surface roughness and wind speed.
    3. precipitation
    The precipitation of engineering location meteorological department is inquired about, by precipitation apparatus and precipitation amount controller come simulated precipitation；
    And precipitation is calculated by formula (8),
    Ps=Pt{1-exp[-(Ta-Tr)/(Tr-Ts)]2}+, Tr≥Ts
    Pr=Pt-Ps (8)
    P in formulasFor snowfall, PrFor rainfall, PtFor gross precipitation, TaFor daily mean temperature, TrFor the critical temperature of rainfall, TsFor The critical temperature of snowfall.
    4. wind speed
    Inquire about the wind speed of the meteorological department in engineering location, threshold wind velocity simulator, to draw concrete surface according to wind speed Coefficient of heat transfer.
CN201711121439.XA 2017-11-14 2017-11-14 A kind of method for measuring concrete surface drying shrinkage stress Pending CN107907412A (en)

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CN114323992A (en) * 2021-11-25 2022-04-12 中南大学 Device and method for testing concrete creep characteristic under positive and negative temperature alternating action
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CN111766146A (en) * 2020-07-03 2020-10-13 浙江大学 Testing and evaluating method and device for shrinkage cracking performance of solidified soil material
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