CN1063358A - Concrete absolute stress and elastic modulus detection method - Google Patents
Concrete absolute stress and elastic modulus detection method Download PDFInfo
- Publication number
- CN1063358A CN1063358A CN 91100397 CN91100397A CN1063358A CN 1063358 A CN1063358 A CN 1063358A CN 91100397 CN91100397 CN 91100397 CN 91100397 A CN91100397 A CN 91100397A CN 1063358 A CN1063358 A CN 1063358A
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- concrete
- pressurization
- blind hole
- hole
- strain
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Abstract
A kind of new concrete absolute stress and elastic modulus detection method " blind hole relaxes-pressurization ".Be applicable to can not pre-buried sensor the concrete member of having built.Use HJY-1 concrete absolute stress pick-up unit newly developed, can detect the absolute stress and the elastic modulus of all kinds of concrete members of having built reliably.
Description
This method belongs to force measurement.
Application number is a kind of piezomagnetic concrete absolute stress pick-up unit that can directly demonstrate stress value of 88108972.9, is a kind of its sensor to be embedded in pick-up unit in the concrete member in advance, and is for built structure that can't pre-buried sensor, then inapplicable.
On built structure, detect the concrete absolute stress, two kinds of methods were once arranged.One says the core method of getting, promptly on the concrete member, drill through the concrete core, elder generation is the good strain-gauge rosette of surface arrangement of core before drilling through, detect because concrete core when being separated from member with strainmeter, the lax strain that causes, extrapolate original stress of measuring point more according to this, required elastic mould value is done experiment with the concrete core and is obtained.The required concrete core that drills through of this method is very big, and drilling machine is heavy and damage member or the like shortcoming, fails to promote.Another says the slit stress restoration, promptly cut out a slit on the concrete surface, put into lifting jack in the groove, exert pressure with sidewall to groove, set strainometer and displacement meter on the concrete surface of the both sides of groove in advance, detect since the lax strain that causes of grooving, lax displacement and since pressurization cause add compressive strain and pressurization displacement, when lax strain, lax displacement and when adding compressive strain, pressurization displacement equal and opposite in direction, opposite in sign, this moment, lifting jack institute applied pressure value was the absolute stress value of the former existence of concrete.This method a groove can only draw the stress value of a direction, the grooving size is big, bigger to component damage, and can't draw the elastic mould value of concrete, and this value is a very important parameter, thus also fail to promote the use of, so, at present both at home and abroad, Shang Wuke is put to the apparatus and method that practical concrete absolute stress and elastic modulus to built structure detect.
Purpose of the present invention just is to propose new design, and proposes on this basis to detect principle, designs and manufactures pick-up unit and proposes detection method.
The main points of this method are at first to bore the system blind hole at concrete measuring point place, around blind hole point, arrange foil gauge or strain-gauge rosette earlier, the size of blind hole wants to satisfy the requirement of detected value precision, do not influence the normal use of member again, especially will be applicable to small-sized concrete member.With a cover pressue device, to the sidewall pressurization of blind hole, the use instrument detecting goes out the lax strain around the blind hole and adds compressive strain, and to blind pore wall applied pressure value.After instrument is handled signal, the major principal stress of promptly exportable measuring point concrete, least principal stress, principle stress angle and elastic modulus, we claim this method to be " blind hole relaxes-pressurization ".
The principle of this method is that as shown in the figure, the stress of member measuring point always can be regarded principle stress б as
1, б
2Two dimensional stress state.At distance initial point polar coordinates be for the stress that (r, θ) locates:
Tangential stress:
Radial stress:
Drill through the manhole that radius is a at 0.The stress that (r, θ) locates after the perforate according to Elasticity Kirsch formula is:
Stress value was changed to (2)-(1) before and after boring caused (r, θ) boring
Promptly
△б
θ＝б
θ′-б
θ（3）
△б
r＝б
r′-б
r
In (1), (2) formula substitution (3):
According to Hooke's law, locate at (r, θ), because the radial strain value △ ε that boring causes is:
△ε＝（△б
r-μ△б
θ）/E （5）
In fact, radial strain sheet as shown in the figure is not a bit, but L=r
2-r
1, the mean strain value that foil gauge reflected is:
In (4) substitution (6), integration gets:
△ε
m＝A（б
1+б
2）+B（б
1-б
2）cos2θ （7）
In the formula
A = - (a
2)/(2r
1r
2) × (1 + μ)/(E)
B = - (2a
2)/(r
1r
2) × 1/(E) ［1 - (a
2（1＋μ）（r
1 2＋r
1r
2＋r
2 2）)/(4r
1 2r
2 2) ］ (8)
If form strain-gauge rosette by arranging three sheet resistance foil gauges shown in the figure, counterclockwise compiling is 1,2, No. 3, with б
1The angle of direction is respectively θ, θ+π/4, θ+pi/2, and it is because the strain value that boring causes is respectively △ ε
1m, △ ε
2mWith △ ε
3mIn its substitution (7):
△ε
1m＝A（б
1+б
2）+B（б
1-б
2）cos2θ
△ε
2m＝A（б
1+б
2）-B（б
1-б
2）sin2θ
△ε
3m＝A（б
1+б
2）-B（б
1-б
2）cos2θ （9）
Separating (9) gets:
б
1= (△ε
fm+ △ε
3m)/(4A) + (△ε
1m+ △ε
3m)/(4Bcos2θ)
б
2= (△ε
1m+ △ε
3m)/(4A) - (△ε
1m- △ε
3m)/(4Bcos2θ) (10)
2θ= arctg (2△ε
2m- 4ε
1m- △ε
3m)/(△ε
1m- △ε
3m)
Learn by (10), wish to get б accurately
1, б
2With the θ value, △ ε accurately must be arranged
1m, △ ε
2m, △ ε
3mA and B value, △ ε
1m△ ε
2m△ ε
3mCan record by detecting instrument.From (3), learn, remove a, r
1, r
2, outside can obtaining after bore diameter and foil gauge arrangement are determined, the unknown with E is arranged still.The known numeric value fluctuation is little, but E has very big discreteness, and is also big to the influence of measurement result, so must reach out for elastic modulus E accurately.
If in the circular hole shown in the figure, apply uniform pressure q along hole wall, then (r, θ) locates and will cause stress:
б
r= - (a
2)/(r
2) × q
б
θ= - (a
2)/(r
2) × q (11)
(11) are made ess-strain by Hooke's law convert and carry out integration, can draw resistance strain gage radially owing to apply the mean strain value that uniform pressure q causes along hole wall and be:
△ε
j = -(a
2)/(r
1r
2) × (1 + μ)/(E) × q = 2Aq (12)
Then the elastic modulus of concrete is:
E = -
(a
2)/(r
1r
2) × (1 + μ)/(△ε
j) × q （13）
As seen, as long as detect q and △ ε
j, can obtain E.So far, in theory, the б of measuring point concrete
1, б
2, θ and E all can record exactly.
The root root is analyzed and test, and we get aperture a=3.5cm, foil gauge gauge length L=8cm, and its near-end is apart from center, hole r
1=4.5cm, its far-end is apart from center, hole r
2=12.5cm, μ=1/6, the relevant formula in difference substitution front can draw:
б
1= ((△ε
1m+ △ε
3m)q)/(2△ε
j) + ((△ε
1m+ △ε
3m)q)/(5.04△ε
jcos2θ)
б
2= ((△ε
1m+ △ε
3m)q)/(2△ε
j) - ((△ε
1m- △ε
3m)q)/(5.04△ε
jcos2θ) (14)
2θ= arctg (2△ε
2m- △ε
1m- △ε
3m)/(△ε
1m- △ε
3m)
And
E＝-0.25q/△ε
j（15）
When measuring point is a two-dimensional state of stress, but principal direction of stress is known, then only needs along two principal direction of stress б
1, б
2Arrange that two foil gauges get final product.Principle stress formula and (14) are together.
When measuring point is a uniaxial stressed state, and principal direction of stress is known, then only needs to arrange that along the б direction a slice foil gauge get final product.Its principle stress formula is:
б＝0.57×q×△ε
m/△ε
j（16）
Above-mentioned being " blind hole relaxes-pressurization " detected the ultimate principle of concrete absolute stress and elastic modulus, design in view of the above, succeeded in developing by sensor, drilling machine, added and present a theatrical performance as the last item on a programme and pick-up unit that concrete absolute stress detector is formed, named and be NJY-1 structure concrete absolute stress pick-up unit.This device proposes patented claim jointly by Chongqing Highway Science Inst. Ministry of Communications, tianjin building instrument plant.
Formula (14) (15) (16) is to derive out according to the theory of elasticity that drills through the hole on the infinite field elastic sheet.For blind hole, for satisfying (14) (15) (16) three formulas, still need and solve hole depth, aperture problem, solution is satisfied measuring point and is had enough lax and add compressive strain output and do not influence again under the normal operating position of member, this this great problem of gauge length much and foil gauge of blind hole solves measuring point place this great problem of member boundary dimensions.For this reason, we have carried out mechanical analysis.Result of calculation, blind hole aperture 70mm, hole depth 70～80mm, foil gauge gauge length are 80mm, and near-end is apart from center, hole 4.5cm, and far-end is apart from center, hole 12.5cm, and moulding pressure is 5MPa.In the case, drill through the strain output that blind hole causes, resolving accuracy for detector is enough big, the poroid stress that causes with circular port is concentrated minimum, and very limited in the scope that the blind hole ambient stress is concentrated, it is also fast to decay, and the 3.5cm place has only 22% influence from the limit, hole, from 7cm place, limit, hole, do not influenced substantially.That is to say, drill through such blind hole, do not influence the normal use of member.Result of calculation also shows, if the minimum border of member from the measuring point center greater than 17.5cm(2.5 times of aperture), can ignore by the test error that the border causes.This is enough to explanation, and " blind hole relaxes-pressurization " is applicable to the bridge member of all kinds and other engineering component, and this is that " slit stress restoration " is incomparable.
If measuring point is arranged in defective member position just, locate as crack, hole etc., or the sticking Quality of foil gauge is not good, the capital has influence on the reliability of testing result, and to this, determination methods is, under the pressure effect of 5MPa, pressurization strain value effective range gets-8 * 10
-6～-25 * 10
-6, every foil gauge pressurization strain value and on the same group between difference and the mean strain value of strain rosette pressurization strain mean the absolute value of ratio just prove that less than 20% testing result is reliable, effective.
" blind hole relaxes-pressurization " and supporting HJY-1 type concrete absolute stress pick-up unit thereof are the breakthroughs of concrete absolute stress detection technique, the real initiative that belongs to.
China's existing highway bridge 4,220,000 linear meter(lin.m.)s.Press the minimum flow measuring and calculating, also there is 4% substandard bridge to rebuild, investment at least also needs 2,000,000,000 yuan, if the method and the supporting pick-up unit thereof that propose with us detect and estimate, then needn't all rebuild, only need to drop into 20～30% of reconstruction expenses, suitably reinforce, can recover and improve the bearing capacity of old bridge, thereby be that country saves a large amount of valuable funds, also may be used in the concrete member of engineerings such as road, harbour, tunnel, dam, house.Promote generally and use, can obtain remarkable economic efficiency and social benefit.
Claims (6)
1, a kind of new concrete absolute stress and elastic modulus detection method " blind hole lax--pressurization ".Use pick-up unit, on the concrete member, hole; Around boring, concrete measuring point surface arranges resistance strain gage in advance.It is characterized in that, use be HJY-1 concrete absolute stress pick-up unit; The hole of being bored on the concrete member is a blind hole; Exert pressure to blind pore wall; Gather the lax strain around the blind hole step by step and add compressive strain with same a slice (group) foil gauge.
2, concrete absolute stress according to claim 1 and elastic modulus detect " blind hole relaxes-pressurization ", it is characterized in that blind hole is rounded, aperture 70mm, hole depth 70～80mm the best.
3, detect " blind hole lax-pressurization " as concrete absolute stress as described in the claim 1,2 and elastic modulus, it is characterized in that the foil gauge gauge length with 80mm, near-end is apart from hole heart 4.5cm, and far-end is apart from hole heart 12.5cm the best.
4, detect " blind hole lax-pressurization " as concrete absolute stress as described in the claim 1,2 and elastic modulus, it is characterized in that the minimum border of measuring point centre distance concrete member greater than 17.5cm for best.
5, the detection of concrete absolute stress according to claim 1 and elastic modulus " blind hole relaxes-pressurization " is characterized in that when the blind hole hole wall applies uniform pressure, and the pressurizer pressure value is got 5MPa for best.
6, the detection of concrete absolute stress according to claim 1 and elastic modulus " blind hole lax-pressurization " is characterized in that judging that the method for the validity of testing result is that under the effect of 5MPa pressure, pressurization strain value effective range gets-80 * 10
-6～-25 * 10
-6, the absolute value of ratio is less than 20% between the equal strain value of difference peace of every foil gauge pressurization strain value and strain rosette pressurization strain mean on the same group.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 91100397 CN1025240C (en) | 1991-01-18 | 1991-01-18 | Detecting method of concrete absolute stress and elastic modulus |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN 91100397 CN1025240C (en) | 1991-01-18 | 1991-01-18 | Detecting method of concrete absolute stress and elastic modulus |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN1063358A true CN1063358A (en) | 1992-08-05 |
| CN1025240C CN1025240C (en) | 1994-06-29 |
Family
ID=4904600
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN 91100397 Expired - Fee Related CN1025240C (en) | 1991-01-18 | 1991-01-18 | Detecting method of concrete absolute stress and elastic modulus |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN1025240C (en) |
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN102937492A (en) * | 2012-10-26 | 2013-02-20 | 北京工业大学 | Method for monitoring absolute stress of pre-stress concrete bridge |
| CN103076118A (en) * | 2011-10-26 | 2013-05-01 | 贵州中建建筑科研设计院有限公司 | Ring cutting detection method for working stress of concrete component |
| CN104330305A (en) * | 2014-09-10 | 2015-02-04 | 宁夏大学 | Method for measuring uniaxial tension and elastic modulus of concrete |
| CN104931364A (en) * | 2015-06-04 | 2015-09-23 | 浙江大学 | Reinforced concrete structure fatigue test method and device based on piezomagnetic effect |
| CN105651440A (en) * | 2015-12-30 | 2016-06-08 | 上海金发科技发展有限公司 | Method for quantitatively detecting residual stress of polymer material product |
| CN114383764A (en) * | 2021-12-03 | 2022-04-22 | 华电电力科学研究院有限公司 | Stress characteristic measuring method for hydropower station unit |
-
1991
- 1991-01-18 CN CN 91100397 patent/CN1025240C/en not_active Expired - Fee Related
Cited By (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103076118A (en) * | 2011-10-26 | 2013-05-01 | 贵州中建建筑科研设计院有限公司 | Ring cutting detection method for working stress of concrete component |
| CN103076118B (en) * | 2011-10-26 | 2016-04-13 | 贵州中建建筑科研设计院有限公司 | The ring cutting detection method of concrete component working stress |
| CN102937492A (en) * | 2012-10-26 | 2013-02-20 | 北京工业大学 | Method for monitoring absolute stress of pre-stress concrete bridge |
| CN102937492B (en) * | 2012-10-26 | 2014-11-26 | 北京工业大学 | Method for monitoring absolute stress of pre-stress concrete bridge |
| CN104330305A (en) * | 2014-09-10 | 2015-02-04 | 宁夏大学 | Method for measuring uniaxial tension and elastic modulus of concrete |
| CN104931364A (en) * | 2015-06-04 | 2015-09-23 | 浙江大学 | Reinforced concrete structure fatigue test method and device based on piezomagnetic effect |
| CN105651440A (en) * | 2015-12-30 | 2016-06-08 | 上海金发科技发展有限公司 | Method for quantitatively detecting residual stress of polymer material product |
| CN114383764A (en) * | 2021-12-03 | 2022-04-22 | 华电电力科学研究院有限公司 | Stress characteristic measuring method for hydropower station unit |
Also Published As
| Publication number | Publication date |
|---|---|
| CN1025240C (en) | 1994-06-29 |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| C15 | Extension of patent right duration from 15 to 20 years for appl. with date before 31.12.1992 and still valid on 11.12.2001 (patent law change 1993) | ||
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