CN1451955A - High-sensitivity carbon fibre cement based resistance strain sensing system comprising temp. compensation - Google Patents
High-sensitivity carbon fibre cement based resistance strain sensing system comprising temp. compensation Download PDFInfo
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- CN1451955A CN1451955A CN 03128010 CN03128010A CN1451955A CN 1451955 A CN1451955 A CN 1451955A CN 03128010 CN03128010 CN 03128010 CN 03128010 A CN03128010 A CN 03128010A CN 1451955 A CN1451955 A CN 1451955A
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- carbon fiber
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Abstract
A high-sensitivity carbon fibres reinforced cement-base resistance strain sensing system with temp compensation is characterized by that the carbon fibres reinforced cement is attached to top and bottom surfaces of an ordinary concrete beam, 4 electrodes are symmetrically stuck onto upper and lower cement layers, two external electrodes are connected to constant-current DC source, and two central electrodes are connected to an instrument for measuring voltage. Calculations can obtain the voltage difference and then the bend deformation of concrete beam.
Description
Technical field
The invention belongs to the building engineering structure field tests, a kind of specifically high sensitivity carbon-fiber cement base resistance-strain sensor-based system that contains temperature compensation.
Background technology
In the engineering structure test, the deflection of beam distortion is one of maximum performance index of test.Static state and the dynamic response of test beam under load and external environment condition effect is the prerequisite that guarantees the beam operate as normal.What use was maximum at present is adhering resistance strain sheets, and the resistance value of foil gauge changes with the distortion of beam, and is reliable and stable, technology maturation.But the sensitivity coefficient of resistance strain gage is too low, only is 2, and is not suitable for doing long term monitoring.Carbon fiber reinforced cement has very high resistance susceptibility to distortion, and during tension, resistance reversibly increases, and during pressurized, resistance reversibly reduces.Upper surface or lower surface at common beams of concrete apply one deck carbon fiber reinforced cement, when beams of concrete bears bending load, by detecting the resistance variations of carbon fiber reinforced cement, just can monitor in real time xoncrete structure.The resistance of carbon fiber reinforced cement not only is out of shape very responsive (pressure-sensitive) to it in addition, and to its temperature also very responsive (temperature sensitive property).When the temperature rising, resistance will reduce; Temperature reduces, and resistance will increase.Because pressure-sensitive and temperature sensitive two kinds of effects of carbon fiber reinforced cement mix, and will bring very big inconvenience to test, still there are not desirable and practical decoupling method at present.Like this, just cause because temperature effect causes the instability of pressure-sensitive self diagnosis.Therefore, the pressure-sensitive function-stable Journal of Sex Research of carbon fiber reinforced cement under complex environment becomes the self diagnosis sensitive concrete and carry out the key in application problem on its layer of structure.
Summary of the invention
The purpose of this invention is to provide a kind of sensitivity coefficient height, suitable long term monitoring, the stable high high sensitivity carbon-fiber cement base resistance-strain sensor-based system that contains temperature compensation done, to overcome above-mentioned deficiency.
To achieve these goals, characteristics of the present invention are: carbon fiber reinforced cement is applied upper and lower surface in normal concrete beams, form sandwich construction, it is firm to guarantee that the carbon fiber reinforced cement layer is connected with former beams of concrete, be stained with four electrodes symmetrically with conducting resinl respectively at carbon fiber reinforced cement layer up and down, two electrodes in the outside of carbon fiber reinforced cement layer insert dc constant flowing power respectively up and down, middle two electrodes are measuring voltage respectively, and its measuring voltage output is connected with the surveying instrument of outside;
The thickness that above-mentioned carbon fiber reinforced cement applies in the upper and lower surface of normal concrete beams is 3～20mm;
Resistance between middle two electrode of above-mentioned carbon fiber reinforced cement layer up and down about equally;
The two ends of an above-mentioned up and down same polarity of carbon fiber reinforced cement layer voltage output end couple together, and two homopolar ends are as output in addition, and form a differential circuit, and output is connected with the surveying instrument of outside;
The strength of current of above-mentioned dc constant flowing power is 10-100mA;
The manufacture craft of above-mentioned carbon fiber reinforced cement is:
The polyacrylonitrile-radical chopped carbon fiber that 4-7mm is long adds to be furnished with in the aqueous solution of spreading agent, earlier stir dispersion in about 2 minutes with hand, add cement, silicon ash, water reducer, defoamer then in proportion, stirred 3 minutes with clean slurry stirring machine, be mixed and made into carbon fiber reinforced cement in 1: 1 ratio and sand simultaneously;
Above-mentioned spreading agent is a sodium cellulose glycolate;
The addition of above-mentioned water reducer and defoamer is dripped for each 2-3;
Above-mentioned each proportion of raw materials is:
Cement: carbon fiber: silicon ash: water: spreading agent=100: 0.2-1: 15: 55: 0.4.
Because it is the sensitive concrete that main raw material(s) is made that the present invention adopts chopped carbon fiber, adjuvant, cement, sand, and the smart concret structure that adopts this material, adopt special process, carbon fiber is dispersed in the concrete, makes its sensitive concrete material have good strain-resistance sensitlzing effect.The present invention utilizes the strain sensitivity of carbon fiber reinforced cement, upper and lower surface in normal concrete beams is laid the carbon fiber reinforced cement layer, forms sandwich construction (sandwich), adopts four electrode method, and utilize the differential principle wiring, can obtain high strain-resistance susceptibility.Carbon fiber reinforced cement also has the temperature-resistance sensitlzing effect simultaneously, and this effect brings very big error can for the deformation measurement of beams of concrete.The xoncrete structure load bearing beam occurs bending and deformation, and beam is increase of resistance of carbon fiber reinforced cement layer up and down, and one reduces; And the variation of environment temperature make beam up and down the resistance of carbon fiber reinforced cement layer increase simultaneously or reduce.According to this principle, design circuit is realized temperature compensation.In civil engineering structure Gernral Check-up (SHM), the deflection of beam distortion is one of maximum performance index of monitoring.Adopt carbon fiber reinforced cement and sandwich construction thereof, can realize online deformation monitoring; Because carbon fiber reinforced cement and concrete material have good material compatibility, its measurement information can truly reflect the distortion of xoncrete structure; Because the intrinsic of carbon fiber reinforced cement, it is good to have persistence, and the induction volume is big, can be used for long term monitoring; In addition, the cost of carbon fiber reinforced cement is low, and good mechanical property is arranged.Adopt structure of the present invention except that high strain-resistance susceptibility is arranged, also can eliminate the influence of environment temperature, improved the stability of strain sensitive simultaneously.
Description of drawings
Accompanying drawing is a structural representation of the present invention.
Embodiment
The invention will be further described below in conjunction with drawings and Examples, but this embodiment should not be construed as limitation of the present invention.
The present invention applies upper and lower surface in normal concrete beams with carbon fiber reinforced cement, form sandwich construction, adopt four electrode measuring resistance methods, (as shown in drawings) carbon fiber reinforced cement (CFRC) layer is respectively pasted four electrodes about the normal concrete beams test block, according to four electrode method, two the electrifying electrodes streams in each layer outside, two electrodes in the inside are surveyed voltage.To go up CFRC layer and following CFRC layer by a direct current two-way constant current source power supply, with guarantee by about the electric current of CFRC layer be that equate, constant.
According to Ohm law:
U
AB＝I×R
AB U
CD＝I×R
CD (1)
P occurs bending and deformation when the beams of concrete bearing pressure, simultaneously the environment temperature Δ T that also changes.So, the beam resistance of CFRC layer can change (suppose that beams of concrete is to be bent downwardly, the environment temperature reduction) up and down:
Δ R
AB=-Δ R
AB b+ Δ R
AB TΔ R
CD=Δ R
CD b+ Δ R
CD T(2) in the formula: Δ R
AB bWith Δ R
CD bBe the beam absolute value that changes because of flexural deformation of the resistance of CFRC layer up and down; Δ R
AB TWith Δ R
CD TBe the beam absolute value that changes because of environment temperature of the resistance of CFRC layer up and down.
It should be noted that Δ R when the beams of concrete carrying occurs bending and deformation
AB bWith Δ R
CD bSymbol and Δ R
AB TWith Δ R
CD TAll identical (explanation: Δ R in formula (2) of symbol
AB bThe front negative sign is arranged).
The anode C that the anode A and the following CFRC layer of last CFRC layer survey voltage are surveyed voltage couples together, and the negative terminal B of levels survey voltage and D calculate as the differential surveying instrument of exporting to the outside and convert, promptly
U
BD=U
CD-U
AB=I * (R
CD-R
AB) (3) draw voltage difference and converse the beams of concrete carrying degree that occurs bending and deformation, and finishes test process.
When the beams of concrete carrying occurs bending and deformation
ΔU
BD＝ΔU
CD-ΔU
AB
＝I×ΔR
CD-I×ΔR
AB
＝I×(ΔR
CD b+ΔR
CD T)-I×(-ΔR
AB b+ΔR
AB T)
＝I×[(ΔR
CD b+ΔR
AB b)+(ΔR
CD T-ΔR
AB T)] (4)
Because the material component of CFRC layer is identical up and down, R
CDAnd R
ABSubstantially equal, even because technological reason, CFRC layer resistance difference also can make R by the position of adjusting electrode up and down
CDAnd R
ABNear equating.The temperature characterisitic of CFRC layer is also basic identical up and down, (Δ R
CD T-Δ R
AB T) and (Δ R
CD b+ Δ R
AB b) compare and can ignore.Promptly
Δ U
BD≈ I * (Δ R
CD b+ Δ R
AB b) (5) output only reflected and the distortion of beams of concrete realized temperature compensation.
The relative change rate of output voltage when the normal concrete beams test block is subjected to bend (formula (3) is removed by formula (5)) is
ΔU
BD/U
BD＝(ΔR
CD b+ΔR
AB b)/(R
CD-R
AB)
(ΔR
CD b+ΔR
AB b)/(R
CD-R
AB)＞＞ΔR
CD/R
CD (6)
(ΔR
CD b+ΔR
AB b)/(R
CD-R
AB)＞＞ΔR
AB/R
AB
This explanation: because beams of concrete distortion, adopt the structure of the present invention's design and the resistance change rate that causes will become the increase of the order of magnitude than any one deck (upper strata or lower floor) resistance change rate of carbon fiber reinforced cement.
The manufacture craft of carbon fibre reinforced concrete of the present invention (CFRC) is:
The polyacrylonitrile-radical chopped carbon fiber (its performance such as table 1) that 4-7mm is long adds in the aqueous solution of being furnished with spreading agent (sodium cellulose glycolate) (various proportionings see Table 2), earlier stir dispersion in about 2 minutes with hand, add cement (425#, 525#) silicon ash, water reducer (two, three), defoamer (two, three) by preset proportion then, stirred 3 minutes with clean slurry stirring machine, be mixed and made into carbon fibre reinforced concrete in 1: 1 ratio and sand again.
Table 1 carbon fiber performance
Diameter pulling strengrth stretch modulus resistivity density
/μm /GPa /GPa /Ω·m /g·
-3
7±0.2 ≥1.95 ≥175 25.0×10
-5 ≥1.75
Table 2 sample materials proportioning
Carbon fiber/cement silicon ash/cement water/cement dispersants/cement
(wt.％) (％) (％) (％)
0.5 15 55.0 0.4
Claims (9)
1, a kind of high sensitivity carbon-fiber cement base resistance-strain sensor-based system that contains temperature compensation, it is characterized in that: carbon fiber reinforced cement is applied upper and lower surface in normal concrete beams, form sandwich construction, it is firm to guarantee that the carbon fiber reinforced cement layer is connected with former beams of concrete, be stained with four electrodes symmetrically with conducting resinl respectively at carbon fiber reinforced cement layer up and down, two electrodes in the outside of carbon fiber reinforced cement layer insert dc constant flowing power respectively up and down, middle two electrodes are measuring voltage respectively, and its measuring voltage output is connected with the surveying instrument of outside.
2, the high sensitivity carbon-fiber cement base resistance-strain sensor-based system that contains temperature compensation as claimed in claim 1, it is characterized in that: the thickness that carbon fiber reinforced cement applies in the upper and lower surface of normal concrete beams is 3～20mm.
3, the high sensitivity carbon-fiber cement base resistance-strain sensor-based system that contains temperature compensation as claimed in claim 1 is characterized in that: the resistance between middle two electrode of carbon fiber reinforced cement layer about equally up and down.
4, the high sensitivity carbon-fiber cement base resistance-strain sensor-based system that contains temperature compensation as claimed in claim 1, it is characterized in that: the two ends of a same polarity of carbon fiber reinforced cement layer voltage output end couple together up and down, two homopolar ends are as output in addition, and form a differential circuit, output is connected with the surveying instrument of outside.
5, the high sensitivity carbon-fiber cement base resistance-strain sensor-based system that contains temperature compensation as claimed in claim 1, it is characterized in that: the strength of current of dc constant flowing power is 10-100mA.
6, the high sensitivity carbon-fiber cement base resistance-strain sensor-based system that contains temperature compensation as claimed in claim 1, it is characterized in that: the manufacture craft of carbon fiber reinforced cement is:
The polyacrylonitrile-radical chopped carbon fiber that 4-7mm is long adds to be furnished with in the aqueous solution of spreading agent, earlier stir dispersion in about 2 minutes with hand, add cement, silicon ash, water reducer, defoamer then in proportion, stirred 3 minutes with clean slurry stirring machine, be mixed and made into carbon fiber reinforced cement in 1: 1 ratio and sand simultaneously.
7, the high sensitivity carbon-fiber cement base resistance-strain sensor-based system that contains temperature compensation as claimed in claim 6, it is characterized in that: spreading agent is a sodium cellulose glycolate.
8, the high sensitivity carbon-fiber cement base resistance-strain sensor-based system that contains temperature compensation as claimed in claim 6, it is characterized in that: the addition of water reducer and defoamer is dripped for each 2-3.
9, the high sensitivity carbon-fiber cement base resistance-strain sensor-based system that contains temperature compensation as claimed in claim 6, it is characterized in that: each proportion of raw materials of carbon fiber reinforced cement is:
Cement: carbon fiber: silicon ash: water: spreading agent=100: 0.2-1: 15: 55: 0.4.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 03128010 CN1238707C (en) | 2003-05-22 | 2003-05-22 | High-sensitivity carbon fibre cement based resistance strain sensing system comprising temp. compensation |
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|---|---|---|---|
| CN 03128010 CN1238707C (en) | 2003-05-22 | 2003-05-22 | High-sensitivity carbon fibre cement based resistance strain sensing system comprising temp. compensation |
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| Publication Number | Publication Date |
|---|---|
| CN1451955A true CN1451955A (en) | 2003-10-29 |
| CN1238707C CN1238707C (en) | 2006-01-25 |
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|---|---|---|---|
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Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100367022C (en) * | 2005-03-09 | 2008-02-06 | 湖南科技大学 | Intelligent concrete test block and its producing and use |
| CN101806714A (en) * | 2010-04-20 | 2010-08-18 | 东南大学 | Beam tester of bonding strength of fibre reinforced composite sheet and concrete |
| CN101886954A (en) * | 2010-07-09 | 2010-11-17 | 济南大学 | Cement-based temperature sensing element for positive and negative temperature automatic measurement |
| CN102095362A (en) * | 2010-11-20 | 2011-06-15 | 武汉理工大学 | Grid-type carbon fiber strain transducer |
| CN102135457A (en) * | 2011-02-22 | 2011-07-27 | 哈尔滨工业大学 | Method for extracting sensing signal of smart cement-based material |
| CN102494603A (en) * | 2011-11-22 | 2012-06-13 | 东南大学 | Distributed high-precision long-gauge-length carbon fiber strain test device and method |
| CN103453833A (en) * | 2013-09-03 | 2013-12-18 | 东南大学 | Long-gauge length carbon fiber strain sensing device and method for testing same |
| CN104864995A (en) * | 2015-05-22 | 2015-08-26 | 西安近代化学研究所 | Carbon fiber concrete sensing element capable of perceiving impact load |
-
2003
- 2003-05-22 CN CN 03128010 patent/CN1238707C/en not_active Expired - Fee Related
Cited By (11)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN100367022C (en) * | 2005-03-09 | 2008-02-06 | 湖南科技大学 | Intelligent concrete test block and its producing and use |
| CN101806714A (en) * | 2010-04-20 | 2010-08-18 | 东南大学 | Beam tester of bonding strength of fibre reinforced composite sheet and concrete |
| CN101806714B (en) * | 2010-04-20 | 2011-08-10 | 东南大学 | Beam tester of bonding strength of fibre reinforced composite sheet and concrete |
| CN101886954A (en) * | 2010-07-09 | 2010-11-17 | 济南大学 | Cement-based temperature sensing element for positive and negative temperature automatic measurement |
| CN102095362A (en) * | 2010-11-20 | 2011-06-15 | 武汉理工大学 | Grid-type carbon fiber strain transducer |
| CN102135457A (en) * | 2011-02-22 | 2011-07-27 | 哈尔滨工业大学 | Method for extracting sensing signal of smart cement-based material |
| CN102135457B (en) * | 2011-02-22 | 2012-10-17 | 哈尔滨工业大学 | Method for extracting sensing signal of smart cement-based material |
| CN102494603A (en) * | 2011-11-22 | 2012-06-13 | 东南大学 | Distributed high-precision long-gauge-length carbon fiber strain test device and method |
| CN103453833A (en) * | 2013-09-03 | 2013-12-18 | 东南大学 | Long-gauge length carbon fiber strain sensing device and method for testing same |
| WO2015032364A1 (en) * | 2013-09-03 | 2015-03-12 | 东南大学 | Long gauge length carbon fiber strain sensing device and testing method therefor |
| CN104864995A (en) * | 2015-05-22 | 2015-08-26 | 西安近代化学研究所 | Carbon fiber concrete sensing element capable of perceiving impact load |
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| Publication number | Publication date |
|---|---|
| CN1238707C (en) | 2006-01-25 |
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