CN1866005A - Method for testing real stress of self-compensating concrete structure and concrete real stress gauge - Google Patents

Abstract

The related test method for true stress of concrete structure comprises: setting a equal-section insulator on test direction to isolate the concrete in and out of the device, using a force senor to test concrete column axial force in device to obtain the objective value. This invention eliminates non-spring strain effect, has reliable result and well practice.

Description

Self compensation xoncrete structure method for testing real stress and concrete real stress gauge

Technical field

The present invention relates to the xoncrete structure stress test method, specifically is a kind of self compensation xoncrete structure method for testing real stress, the invention still further relates to the concrete real stress gauge that described method adopts.

Background technology

Xoncrete structure is modal a kind of building structure in the civil engineering work, and people make full use of characteristics such as its compressive strength height, good endurance, build a large amount of cultures, has been promoted greatly since the concrete material invention.Along with science and technology development, the characteristics of concrete material are familiar with by the engineering staff gradually: concrete is not the ideal line resilient material, and it can produce contraction behind moulding by casting; Under load action, not only produce elastic strain, as time passes, also produce and creep; Under temperature action, can produce and expand or contraction.Because there are greatest differences in sensor and concrete in material behavior, when xoncrete structure produced temperature strain, contraction strain or creeps strain, sensor can produce extra-stress because it stops surrounding concrete structure Free Transform.Therefore, the engineering staff is running into a huge difficult problem aspect the true stress of test xoncrete structure.

Engineering circle has 2 kinds of methods usually in the xoncrete structure stress test at present.Method one: utilize the strain transducer of imbedding in the concrete, record the strain of xoncrete structure under various load actions.According to the concrete material characteristics, this strain comprises (hereinafter the abbreviating these three kinds of strains as inelastic strain) such as elastic strain (hereinafter elastic strain being called in letter), temperature strain, contraction strain and the strains of creeping that stress produces.The engineering staff must deduct inelastic strain exactly and obtain elastic strain from the test strain, multiply by the stress that modulus of elasticity of concrete converses xoncrete structure then.Because the discreteness of concrete material is very big, the material parameter time to time change, wants accurately to grasp it and shrink, creep and temperature all is unusual difficulty to the amount of influence of strain and modulus of elasticity of concrete.Therefore, even the strain testing result is accurate, this method gained stress varies with each individual, and its result's accuracy and reliability depend critically upon tester's theoretical level and engineering experience.This shows by said method can't guarantee that obtaining concrete gets true stress.Method two: pressure transducer is directly imbedded in the xoncrete structure, calculated xoncrete structure stress by the pressure on the testing sensor.Though this method does not need to calculate stress from strain, but directly record stress, but when xoncrete structure produces inelastic strain, because sensor and the difference of xoncrete structure on material behavior, to produce great extra-stress on the sensor, cause the concrete true stress of test result substantial deviation.Because this method is failed to solve the test of xoncrete structure inelastic strain counter stress in theory and is produced the problem that has a strong impact on, and therefore, fails to obtain practical application widely.

Summary of the invention

One of purpose of the present invention provides a kind of self compensation xoncrete structure method for testing real stress, it can really solve the difficult problem of concrete true stress test, by adopting spacer assembly to utilize the concrete self-characteristic that inelastic strain is compensated, reduce the influence of inelastic strain to greatest extent to test result, directly record xoncrete structure stress, and do not need from strain to calculate stress, thereby overcome the problem that present engineering circle concrete stress can't accurately be tested.

Two of purpose of the present invention provides a kind of concrete real stress gauge of realizing said method, and it not only can realize the test to the concrete true stress, and simple in structure, is convenient to use.

For realizing that the technical scheme that one of purpose of the present invention adopts is such: promptly a kind of self compensation xoncrete structure method for testing real stress, method comprises:

1) according to test request, the accuracy of deterministic force sensor and range are selected the static state or the dynamic force sensor of good stability for use;

2) make or be provided with suitable spacer assembly, spacer assembly length should be not less than 10 times of force transducer thickness;

3) force transducer is fixed in spacer assembly inside or end, constitutes the concrete real stress gauge, and the area of section of record spacer assembly inside;

4) before the concrete depositing, place the concrete real stress gauge along measurement direction, and data line or power lead are led to outside the template at the position that needs test stress;

5) deposit concrete, and near the concrete real stress gauge, vibrate, guarantee the inner concrete compaction of spacer assembly;

6) when needs carry out stress test, read or write down the force transducer reading by data line, and obtain concrete true stress value divided by the area of section of spacer assembly inside.This conversion relation also can embed in the reading device, directly reads or write down concrete true stress value.

The said method principle is as follows:

Utilize the inelastic strain of spacer assembly inner concrete cylinder to compensate the outer concrete inelastic strain of spacer assembly, the sensor extra-stress that inelastic strain is caused reduces.Spacer assembly inner concrete cylinder is to the stress σ that applies on the force transducer _gForm by two parts, the one, the σ that xoncrete structure stress produces _G1The 2nd, the extra-stress σ that inelastic strain (comprise the temperature free strain, shrink and creep) produces _G2The objective of the invention is to make σ _G1Approach σ _c, and make σ _G2Approach 0.

When 1, xoncrete structure bears the strain (elastic strain) that is produced by normal stress:

Concrete normal stress σ _cThe strain that produces is

${\mathrm{\ϵ}}_c=\frac{{\mathrm{\σ}}_c}{E_c}---\left(1\right)$

The deflection that the outer concrete of spacer assembly produces in the spacer assembly length range is

Δh＝h ₀*ε _c………………………………………………………………………………………(2)

Then the total deformation in the spacer assembly is made up of two parts: the one, and spacer assembly inner concrete cylinder deflection Δ h _c, the 2nd, the deflection Δ h of force transducer _gThe axial force that force transducer is subjected to is identical with the axial force of spacer assembly inner concrete cylinder, and sensor is identical with spacer assembly inner concrete cylinder cross-sectional area, and its stress is also identical.Therefore, the deflection of force transducer is

$\mathrm{\Δ}{h}_g=\frac{h_g*{\mathrm{\σ}}_{g1}}{E_g}---\left(3\right)$

The concrete column deflection is

$\mathrm{\Δ}{h}_c=\frac{(h_0-h_g)*{\mathrm{\σ}}_{g1}}{E_c}---\left(4\right)$

If the inside and outside deflection unanimity of concrete in spacer assembly length of spacer assembly, then

Δh＝Δh _c+Δh _g………………………………………………………………………………(5)

(1)～(4) formula is brought into following formula and got

${\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="1"\; label="g"\; filenames="A20061005428700101.png,A20061005428700111.png"\; state="\{\{state\}\}">g</figure-callout>}1}=\frac{{\mathrm{\&sigma;}}_c}{({\mathrm{\&lambda;}}_E-1){\mathrm{\&lambda;}}_h+1}---\left(6\right)$

In the following formula ${\mathrm{\&lambda;}}_E=\frac{E_c}{E_g};$ ${\mathrm{\&lambda;}}_h=\frac{h_g}{h_0}$

From following formula as can be known: when the elastic modulus of sensor consistent with concrete elastic modulus, i.e. λ _ELevel off to 1, perhaps sensor thickness h _gMuch smaller than spacer assembly height h ₀, i.e. λ _hLeveled off to 0 o'clock, the stress that records is concrete true stress.

When 2, concrete produces inelastic strain

When concrete produces inelastic strain ε _μThe time, because the inside and outside concrete stress state of spacer assembly is identical, the concrete homogeneity is identical with environmental baseline, therefore, can think the inside and outside concrete inelastic strain unanimity of spacer assembly.The deflection Δ h that the outer concrete of spacer assembly produces in the spacer assembly length range equals h ₀* ε _μ

The deflection that spacer assembly inner concrete cylinder produces is made up of two parts:

The one, the deflection that inelastic strain produces

Δh _c1＝(h ₀-h _g)*ε _u………………………………………………………………………………(7)

The 2nd, extra-stress σ _G2The deflection that produces

$\mathrm{\&Delta;}{\mathrm{<figure-callout\; id="2"\; label="h\; c"\; filenames="A20061005428700101.png,A20061005428700111.png"\; state="\{\{state\}\}">h</figure-callout>}}_c=(h_0-h_g)*\frac{{\mathrm{\&sigma;}}_{g2}}{E_c}---\left(8\right)$

So Δ h=Δ h _g+ Δ h _C1+ Δ h _C2... ... ... ... ... ... ... ... ... ... (9)

Consider that Δ h equals h ₀* ε _μ, and sensor deflection Δ h _gBe h _g* σ _G2/ E _g, and (7) and (8) formula brought in the following formula and obtain

${\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="A20061005428700101.png,A20061005428700111.png"\; state="\{\{state\}\}">g</figure-callout>}2}=\frac{{\mathrm{\&epsiv;}}_u*E_c}{({\mathrm{\&lambda;}}_E-1)+\frac{1}{{\mathrm{\&lambda;}}_h}}---\left(10\right)$

From following formula, as can be seen, need only λ _hLevel off to 0, then the stress that records of sensor is 0.Choose reasonable λ _hJust the extra-stress that inelastic strain produces can be controlled within the engine request.

3, concrete is done the time spent simultaneously in elastic strain and inelastic strain

The stress that force transducer records under concrete elastic strain and inelastic strain acting in conjunction is

${\mathrm{\&sigma;}}_g={\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="1"\; label="g"\; filenames="A20061005428700101.png,A20061005428700111.png"\; state="\{\{state\}\}">g</figure-callout>}1}+{\mathrm{\&sigma;}}_{\mathrm{<figure-callout\; id="2"\; label="g"\; filenames="A20061005428700101.png,A20061005428700111.png"\; state="\{\{state\}\}">g</figure-callout>}2}=\frac{{\mathrm{\&sigma;}}_c}{({\mathrm{\&lambda;}}_E-1){\mathrm{\&lambda;}}_h+1}+\frac{{\mathrm{\&epsiv;}}_u*E_c}{({\mathrm{\&lambda;}}_E-1)+\frac{1}{{\mathrm{\&lambda;}}_h}}---\left(11\right)$

Make the force transducer and the ratio of modulus of elasticity of concrete approach 1 by manufacture craft, then following formula becomes:

σ _g＝σ _c+ε _u*E _c*λ _h……………………………………………………………………………(12)

As can be seen from the above equation as long as choose reasonable λ _hThe approaching concrete true stress of the stress that size just can make sensor record, the extra-stress that inelastic strain produces is less, satisfies requirement of engineering.

It should be noted that, because the inner concrete column body stress of spacer assembly is a little more than the outside concrete stress of spacer assembly, and the concrete creep strain has the characteristic that is directly proportional with stress, the strain of creeping of spacer assembly inner concrete cylinder is slightly larger than the outside concrete of spacer assembly, this will make concrete stress obtain redistribution, make the inside and outside concrete stress of spacer assembly reach unanimity, therefore, utilize stress that the present invention records in fact more approaching and finally equal the true stress of xoncrete structure than (12) formula.

Symbol:

The sensor elastic modulus E _g

Modulus of elasticity of concrete E _c

The force transducer thickness h _g

Spacer assembly height h ₀

The stress σ that sensor records _g

The stress σ of xoncrete structure _c

For realizing two of the object of the invention, the technical solution used in the present invention is such, and promptly a kind of concrete real stress gauge comprises force transducer, it is characterized in that: described force transducer is arranged in the spacer assembly or the end, and described force sensor signals line is by drawing in the spacer assembly.

The present invention is owing to the short-term or the long-term stress test of xoncrete structure under said structure is applicable to various match ratios, various stress level, various section form and the various humiture environmental baseline.

Description of drawings

The present invention can further specify by the embodiment that accompanying drawing provides.

Accompanying drawing 1 is a structure cut-open view of the present invention;

Accompanying drawing 2 is a user mode synoptic diagram of the present invention.

Referring to accompanying drawing: among the figure: 1-spacer assembly, 2-pressure transducer, 3-spacer assembly inner concrete, the outer concrete of 4-spacer assembly.

Embodiment:

Embodiment 1 self compensation xoncrete structure method for testing real stress, method comprises:

1) according to test request, the accuracy of deterministic force sensor and range are selected the static state or the dynamic force sensor of good stability for use;

2) make or be provided with suitable spacer assembly, spacer assembly length should be not less than 10 times of force transducer thickness;

3) force transducer is fixed in spacer assembly inside or end, constitutes the concrete real stress gauge, and the area of section of record spacer assembly inside;

4) before the concrete depositing, place the concrete real stress gauge along measurement direction, and data line or power lead are led to outside the template at the position that needs test stress;

5) deposit concrete, and near the concrete real stress gauge, vibrate, guarantee that spacer assembly inside and outside concrete is evenly closely knit;

6) when needs carry out stress test, read or write down the force transducer reading by data line, and obtain concrete true stress value divided by the area of section of spacer assembly inside.This conversion relation also can embed in the reading device, directly reads or write down concrete true stress value.

Embodiment 2 concrete real stress gauges

Referring to Fig. 1, Fig. 1 is the structural representation of concrete real stress gauge embodiment of the present invention, and as seen from the figure, the concrete real stress gauge of making by the present invention comprises spacer assembly 1 and force transducer 2 compositions, and is simple in structure, is convenient to use.Force transducer 2 is placed on spacer assembly 1 internal fixation, and force transducer is a pie structure, and its xsect and spacer assembly xsect are complementary.When force transducer was positioned at a certain position, spacer assembly centre, the concrete in the spacer assembly was divided into 2 parts by force transducer; When force transducer was positioned at the spacer assembly end, then its inner concrete was an integral body.

Force transducer of the present invention can directly adopt commercially available vibrating wire cell, piezomagnetic force transducer, strain force sensor and optical fiber type force transducer or the like.

In the example, force transducer is placed the spacer assembly middle part, before concreting, the concrete real stress gauge is fixed along the test stress direction, and the force transducer lead is drawn outside the template.In the concreting engineering, to note protecting sensor, around sensor, fully vibrate simultaneously, evenly closely knit to guarantee spacer assembly inside and outside concrete.

In the test, under the composite condition of the non-resilient compressive strain that applies 10MPa compressive stress and generation 600 μ ε on the xoncrete structure, inelastic strain does not produce stress in theory, so xoncrete structure inside has only the compressive stress of 10MPa.Mechanical analysis shows: the concrete real stress gauge records the 10.7MPa compressive stress under this operating mode, and test error is 0.7MPa only.This example shows, not only theoretical tight, the simple structure, practical of the present invention, and test result is accurate, under non-resilient compressive strain (the conversion compressive stress the is 20.7MPa) effect of 600 μ ε, only produce the test error of 0.7MPa, satisfy the requirement of engineering test fully.Should be noted that the test error of this 0.7MPa is the concrete stress difference in spacer assembly inside and outside.Because concrete material has the characteristic of creeping, this will make the concrete stress difference in spacer assembly inside and outside reduce gradually, and finally level off to 0, show that test error also finally levels off to 0.The present invention has thoroughly solved the stress test error problem that the concrete material inelastic strain brings in long-term puzzlement engineering survey recent decades, both had originality, has great engineering practical value again, be the important breakthrough of xoncrete structure stress test technology, this also is one of the present invention's principal character of being different from other concrete stress method of testing.

Claims (3)

1, a kind of self compensation xoncrete structure method for testing real stress, method comprises:

1) according to test request, the accuracy of deterministic force sensor and range are selected the static state or the dynamic force sensor of good stability for use;

2) make or be provided with suitable spacer assembly, spacer assembly length should be not less than 10 times of force transducer thickness;

3) force transducer is fixed in spacer assembly inside or end, constitutes the concrete real stress gauge, and the area of section of record spacer assembly inside;

4) before the concrete depositing, place the concrete real stress gauge along measurement direction, and data line or power lead are led to outside the template at the position that needs test stress;

5) deposit concrete, and near the concrete real stress gauge, vibrate, guarantee that spacer assembly inside and outside concrete is evenly closely knit;

6) when needs carry out stress test, read or write down the force transducer reading by data line, and obtain concrete true stress value divided by the area of section of spacer assembly inside.

2, a kind of concrete real stress gauge comprises force transducer (1), it is characterized in that: described force transducer is arranged in the spacer assembly (2) or the end, and described force sensor signals line is by drawing in the spacer assembly.

3, concrete real stress gauge according to claim 2 is characterized in that: described spacer assembly is that uniform cross section does not have the top or/and there is not the barrel-like structure at the end.

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