CN101672751B - Nondestructive test method for testing tension of prestress anchorage system - Google Patents

Abstract

The invention relates to a nondestructive test method for testing tension of a prestress anchorage system, belonging to the technical field of engineering construction quality test. The method is operated as the following steps: mounting an acceleration sensor; testing the response property of the sensor by the excitation of an exciting hammer; demarcating parameters and measuring tension; and computing tension with reference to a formula. The method for testing tension of the prestress anchorage system solves the problem that the previous prestress anchorage system can not implement nondestructive test, and simultaneously, striking excitation and vibration response test are both performed on the anchor head of the prestress anchorage system, therefore, the test is convenient and fast, and the tension of the system can be calculated from the measured parameter conveniently.

Description

A kind of lossless detection method of testing tension of prestress anchorage system

Technical field

The invention belongs to engineering construction quality detection technique field, be specifically related to a kind of lossless detection method based on exciting response test tension of prestress anchorage system.

Background technology

Along with the fast development of China's foundation works construction project, prestress system more and more is applied in the engineering constructions such as agent structure, slope treatment, large underground hole and deep foundation pit support in all kinds of buildings, building, bridge, the hydraulic engineering.The tension force of prestress system directly affects its anchoring quality, is most important design and construction index.But, because a variety of causes, after the prestress system process certain hour, the phenomenon that can occur relaxing, promptly its tension force can reduce gradually, thereby influences anchoring and supporting effect, causes hidden dangers in project.In addition, in work progress, also exist the phenomenon of prestress deficiency.Therefore, how testing its prestress is very important.Equally, for the bolt of securing member such as the installation fastening bolt of various large-scale sign boards, the fastening bolt of large-scale steel structure etc., its range of application is very extensive, also is to be necessary very much to the test of its existing tension force.

Regrettably because the shaft of some prestress anchoraging system is imbedded in the works, for detection brings very big difficulty, also do not have both at home and abroad at present a kind of can be under harmless condition the method for its tension force of test fast.

Wait by testing its horizontal natural vibration characteristic (excellent frequency) for exposed string wire, cable wire (being used in the structures such as suspension bridge, cable-stayed bridge) outside, can measure its tension condition easily.Exist clear and definite theory relation between its excellent frequency and the tension force, so can accurately measure its tension force.

Yet, this method is applied to as in the prestress systems such as anchor pole, anchor cable, bolt, because their part of the force is hidden in the works, and be subjected under the situation of surrounding structure constraint, can't as string wire, cable wire, measure its excellent frequency with making, also just can't test out its tension force by the method for horizontal exciting.

For a long time, the researchist has attempted the tension force that the whole bag of tricks is tested such prestress system.For example, certain company of Japan has released a kind of detecting instrument that is used to test bolt tension recently.This detecting instrument is based on the frequency conversion supersonic wave test instrument, and the method by bringing out the vertical proper vibration of bolt to be obtaining vertical excellent frequency, thereby and then extrapolates its tension force by the correlationship between itself and the tension force.

But conventional art all is based on the frequency of the rod member of test, is subjected to the influence of prestress system head length and backing plate big, and particularly the measuring accuracy under condition of high ground stress is very undesirable.Therefore, still there is not prestressed mature technology in the effectively reliable test prestress system at present.

The present invention based on the theoretical background state as follows:

1, Ce Shi notion

Typical prestress system structure as shown in Figure 1, the key concept of its tension test is as shown in Figure 2.

By discovering, when prestress system was applied tension force, on surface of contact, its compression rigidity increased along with the increase of pressure, and simultaneously, the quality that participates in vibration also can correspondingly increase, as Fig. 3-A, shown in Fig. 3-B.

Fig. 3-A represents the vibration system under the low stress, and Fig. 3-B represents the vibration system under heavily stressed.

According to these two key concepts, can obtain the relation between the vibratory response of prestress system tension force and test, thus the method for testing of exploitation prestress system tension force.

2, the theory of testing

2-1) ultimate principle

Usually, we comprise anchor head, backing plate and the participation vibration system natural frequency of vibration of test can reflect the rigidity and the quality of system, that is:

$f=\frac{1}{2\mathrm{\π}}\sqrt{\frac{K}{M}}---(1-1)$

Wherein, f obtains the natural frequency of vibration for test, and unit is Hz;

K is the rigidity (spring constant) of vibrational system, and unit is N/m

M is the quality of vibrational system, and unit is kg.

Because the rigidity K of vibrational system can be reduced to the function relevant with tension force/prestress:

K＝k·A (1-2)

Wherein, k is backing plate and rock mass/concrete, the compression rigidity on the surface of contact of bolt and member;

A is the contact area of backing plate and component object (rock mass, concrete etc.).

The relation of compression rigidity k and pressure can be expressed as again:

$k={\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">k</figure-callout>}}_0+\mathrm{\&kappa;}\&CenterDot;{\left(\frac{p}{p_a}\right)}^m---(1-3)$

Wherein, k ₀Be initial rigidity, unit is N/m ³, think that it is a constant;

κ is the surface of contact stiffness coefficient, depends on the state (coarse/level and smooth etc.) of structure material (rock mass, concrete or steel) and surface of contact, thinks that it is a constant, and unit is N/m ³

P is the compressive stress on the surface of contact, and unit is N/m ², p=N/A, wherein, N is pressure (prestress or a tension force), the N of unit, A are contact area, the m of unit ²p _aBe atmospheric pressure, can be taken as 105kPa.M is a pressure index, thinks that in a definite system it is a constant, dimensionless.

So far, can obtain relation between the frequency values of prestress/tension force N and test:

$N=A\&CenterDot;{\left[\frac{1}{\mathrm{\&kappa;}}(\frac{{4\mathrm{\&pi;}}^2{f}^2{M}_H{a}_H}{a_S\&CenterDot;A}-k_0)\right]}^{1/m}\&CenterDot;p_a---(1-4)$

2-2) tension force calculates

Not under the situation with tension variation (less bolt, hovering pull bar etc. as anchor object), oscillating mass M then is a constant substantially in the following formula at vibration system.Yet we are by discovering, for prestress systems such as the anchor pole of most of flush types, anchor cables, M is not to be a constant, and changes along with the variation of tension force.To this, we have proposed the notion of " equivalent mass ", and test with following method:

$M=\frac{F}{a_S}=\frac{M_H{a}_H}{a_S}---(1-5)$

Wherein, M _H: the quality of peening hammer;

a _H: the peak acceleration of testing on the peening hammer;

a _S: in the peak acceleration of system testing;

Therefore, can by

$N=A\&CenterDot;{\left[\frac{1}{\mathrm{\&kappa;}}(\frac{{4\mathrm{\&pi;}}^2{f}^2{M}_H{a}_H}{a_S\&CenterDot;A}-k_0)\right]}^{1/m}\&CenterDot;p_a---(1-4)$

Measure.Certainly, constant and when both having known as M, can directly use formula (1-4) to calculate tension force N.

Wherein, k ₀Can obtain by the response when utmost point low stress (p ≈ 0):

${\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">k</figure-callout>}}_0=\frac{{4\mathrm{\&pi;}}^2{{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">f</figure-callout>}}_0}^{2}M}{A}$

$=\frac{{4\mathrm{\&pi;}}^2{{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">f</figure-callout>}}_0}^2{M}_H{a}_{H0}}{a_{\mathrm{<figure-callout\; id="0"\; label="S"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">S</figure-callout>}0}\&CenterDot;A}---(1-6)$

Required parameter m, κ then need to demarcate in advance, can take the logarithm to (1-4), try to achieve by the mode that returns.

$\ln \left(N\right)=\ln A+\ln p_a+\frac{1}{m}[\ln ({4\mathrm{\&pi;}}^2{f}^2\frac{M}{A}-k_0)-\ln \left(\mathrm{\&kappa;}\right)]$

$=\ln A+\ln p_a+\frac{1}{m}[\ln ({4\mathrm{\&pi;}}^2{f}^2\frac{M_H{\mathrm{\&alpha;}}_H}{a_{S}A}-k_0)-\ln \left(\mathrm{\&kappa;}\right)]---(1-7)$

Constant and when both having known, as prestress system oscillating mass M according to the data (f) of test and the prestress system parameter (k that demarcates ₀, m, κ) can calculate the tension force N of prestress system.

When prestress system oscillating mass M is variable or unknown, then according to the data (f, a that test _H, a _S), the prestress system parameter (k that demarcates ₀, m, κ) and the mass M of vibrator (hammer) _HJust can calculate the tension force of prestress system.

Summary of the invention

The technical issues that need to address of the present invention are, can't adopt harmless method to measure its tension force at the prestress system that is hidden in the works, in order to solve this difficult problem, just need invent a kind of detection method again hits exciting and brings out free vibration by the anchor head/bolt to prestress system, again by its response characteristic of test, thereby measure its tension force, develop a kind of lossless detection method of prestress system tension force.The purpose of this invention is to provide a kind of lossless detection method of testing tension of prestress anchorage system, can carry out Non-Destructive Testing the prestress system that is hidden in the works.Obtain the accurate detection of tension force.Realize that the technical scheme that the object of the invention adopted is as follows, a kind of lossless detection method of testing tension of prestress anchorage system, it is characterized in that, operate as follows: a. is installed in acceleration transducer on the anchor head anchor clamps and exciting hammer of prestress anchorage system end, is connected to tester with signal cable;

B. with exciting hammer or aut.eq. exciting on the anchor head anchor clamps of prestress anchorage system, collecting test data;

C. the Relation Parameters of the response～tension force of prestress system is demarcated;

D. utilize and demarcate the parameter of trying to achieve, similar prestress system is carried out tension detection;

Concrete testing procedure is as follows:

D-1 determines the basic parameter of prestress system and exciting hammer: M _H, A

D-2 is provided with test macro

D-3 determines k ₀: at the tension force N that approaches zero ₀Test out f respectively down, ₀, a _H0, a _S0Thereby, calculate k ₀:

${\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">k</figure-callout>}}_0=\frac{{4\mathrm{\&pi;}}^2{{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">f</figure-callout>}}_0}^2{M}_H{a}_{H0}}{a_{\mathrm{<figure-callout\; id="0"\; label="S"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">S</figure-callout>}0}\&CenterDot;A}---(1-6)$

D-4 determines m and κ: at several tension force N _iTest out f respectively down, _i, a _Hi, a _SiAnd p _i=N _i/ A, order

$y_i=\ln \left(\frac{p_i}{p_a}\right)$

B＝1/m

$x_i=\ln ({4\mathrm{\&pi;}}^2{f_i}^2\frac{M_H{\mathrm{\&alpha;}}_{\mathrm{Hi}}}{{\mathrm{\&alpha;}}_{\mathrm{Si}}A}-k_0)$

$C=-\frac{\ln \left(\mathrm{\&kappa;}\right)}{m}$

Then can obtain regression equation:

y _i＝Bx _i+C (2-1)

By straight-line regression, can obtain B and C, and then try to achieve m and κ:

m＝1/B (2-2)

κ＝e ^-C/B

The mensuration of d-5 tension force

Utilize and return m and κ that obtains and the k that demarcates ₀, bar and exciting hammer basic parameter M _H, backing plate area A can measure the tension force N of homotype prestress system

$N=\mathrm{pA}=A\&CenterDot;{\left[\frac{1}{\mathrm{\&kappa;}}(\frac{{4\mathrm{\&pi;}}^2{f}^2{M}_H{a}_H}{a_S\&CenterDot;A}-k_0)\right]}^{1/m}\&CenterDot;p_a---(1-4)$

The invention has the beneficial effects as follows, the method of this test tension of prestress anchorage system, solved the problem that the past tension of prestress anchorage system can't carry out Non-Destructive Testing, simultaneously because strike exciting and vibratory response test all are to carry out on the anchor head of prestress anchorage system, thereby test conveniently, can go out the tension force of system easily from the survey coaptation.

Description of drawings

Fig. 1 prestress system structural representation.

The basic principle schematic of Fig. 2 prestress system tension test.

Fig. 3-A represents the vibration system under the low stress.

Fig. 3-B represents the vibration system under heavily stressed.

The wiring schematic diagram of Fig. 4 prestress system tension test

Fig. 5 carries out the scheme of installation of timing signal to the Relation Parameters of the response～tension force of prestress system

The regression figure of Fig. 6 tension force～response relation

Embodiment

Referring to figs. 1 through Fig. 3 A, B, under the expression universal, the prestress anchorage system structural representation, simultaneously also in order to show the synoptic diagram of prestress system tension test ultimate principle, and vibration system signal situation under the high low stress, represent the connection diagram that tension of prestress anchorage system of the present invention is tested with reference to Fig. 4, in the present embodiment, connect according to the following steps.1 is the anchor pole tension tester in the drawings, 2 length of exposing for the anchor pole rope, and 3 for being connected to the acceleration transducer on the tension tester by signal cable, and 4 for being equipped with the ground tackle of intermediate plate, and 5 hammer into shape for exciting, and 6 is backing plate.

A. acceleration transducer is installed on the anchor head anchor clamps and exciting hammer of prestress system (as anchor pole, rope) end, is connected to tester with signal cable;

B. with exciting hammer (size, the variable iron hammer of material) or aut.eq. (electromagnet etc.) exciting on the anchor head anchor clamps of prestress system, collecting test data;

C. the Relation Parameters of the response～tension force of prestress system is demarcated;

D. utilize and demarcate the parameter of trying to achieve, similar prestress system is carried out tension detection;

When concrete mensuration, its testing procedure is as follows:

1) determines the basic parameter that prestress system and exciting are hammered into shape: M _H, A

2) test macro is set

3) determine K ₀: at the tension force N that approaches zero ₀Test out f respectively down, ₀, a _H0, a _S0Thereby, calculate k ₀:

${\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">k</figure-callout>}}_0=\frac{{4\mathrm{\&pi;}}^2{{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">f</figure-callout>}}_0}^2{M}_H{a}_{H0}}{a_{\mathrm{<figure-callout\; id="0"\; label="S"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">S</figure-callout>}0}\&CenterDot;A}---(1-6)$

4) determine m and κ: at several tension force N _iTest out f respectively down, _i, a _Hi, a _SiAnd p _i=N _i/ A, order

$y_i=\ln \left(\frac{p_i}{p_a}\right)$

B＝1/m

$x_i=\ln ({4\mathrm{\&pi;}}^2{f_i}^2\frac{M_H{\mathrm{\&alpha;}}_{\mathrm{Hi}}}{a_{\mathrm{Si}}A}-k_0)$

$C=-\frac{\ln \left(\mathrm{\&kappa;}\right)}{m}$

Then can obtain regression equation:

y _i＝Bx _i+C (2-1)

By straight-line regression, can obtain B and C, and then try to achieve m and κ:

m＝1/B

κ＝e ^-C/B (2-2)

5) mensuration of tension force

Utilize and return m and κ that obtains and the k that demarcates ₀, bar and exciting hammer basic parameter M _H, backing plate area A can measure the tension force N of homotype prestress system

$N=\mathrm{pA}=A\&CenterDot;{\left[\frac{1}{\mathrm{\&kappa;}}(\frac{{4\mathrm{\&pi;}}^2{f}^2{M}_H{a}_H}{a_S\&CenterDot;A}-k_0)\right]}^{1/m}\&CenterDot;p_a---(1-4)$

With reference to Fig. 5, the scheme of installation of timing signal is carried out in expression to the Relation Parameters of the response of prestress anchor-hold system and tension force.7 is anchor pole tension force generator among the figure, and 8 is the hydraulic pressure tautness meter.

Suitable equally in to the test of other forms of anchor cable, anchor pole and bolt tension.

In the present embodiment,

1) at first on experimental provision and 17mm ball-type exciting hammer, installs acceleration transducer, be connected on the prestress system tension tester with the noiselike signal cable by Fig. 5.The prestress system tension tester adopts dedicated tester, and above-mentioned required calculating is all carried out automatically by instrument software.

2) determine the basic parameter that prestress system and exciting are hammered into shape: M _H, A etc.

M _H: the quality of exciting hammer; (be the ball-type exciting hammer of 17mm with diameter in this example, its value is: 0.025kg);

A: be contact area, the m of unit ²Generally be the backing plate area, be 0.04m ²

3) system is applied less pressure,, use tester collecting test data: f, a with exciting hammer exciting on the anchor head anchor clamps _H, a _SAt the tension force N that approaches zero ₀Test out f respectively down, ₀, a _H0, a _S0Thereby, calculate k ₀(unit is N/m ³):

${\mathrm{<figure-callout\; id="0"\; label="k"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">k</figure-callout>}}_0=\frac{{4\mathrm{\&pi;}}^2{{\mathrm{<figure-callout\; id="0"\; label="f"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">f</figure-callout>}}_0}^2{M}_H{a}_{H0}}{a_{\mathrm{<figure-callout\; id="0"\; label="S"\; filenames="H2009101778565E00031.png"\; state="\{\{state\}\}">S</figure-callout>}0}\&CenterDot;A}---(1-6)$

Wherein, f: for test obtains the natural frequency of vibration, unit is Hz;

a _H: the exciting hammer is gone up the peak acceleration of test;

a _S: the peak acceleration of system testing;

4) follow according to needs, system applied different pressure, repeat 2) operation, measure at several different tension force N _iDown, f _i, a _Hi, a _SiAnd p _i=N _i/ A, and obtain

$y_i=\ln \left(\frac{p_i}{p_a}\right)$ (wherein, p _aBe atmospheric pressure, can be taken as 105kPa) (2-3)

$x_i=\ln ({4\mathrm{\&pi;}}^2{f_i}^2\frac{M_H{\mathrm{\&alpha;}}_{\mathrm{Hi}}}{a_{\mathrm{Si}}A}-k_0)---(2-4)$

5) according to the x that tries to achieve _i, y _iCan obtain the tension force～response relation curve of anchor cable as shown in Figure 6.Obtain regression equation by straight-line regression: y _i=Bx _i+ C.B and C be can try to achieve, and then m and κ tried to achieve.

In this example, can obtain B=1.1178, C=-3.0545.

(2-3) can try to achieve by formula: m=0.8946, κ=15.3728

Utilize to demarcate the parameter of trying to achieve, when similar prestress system is carried out tension detection, repeat 1) and 2) operation, try to achieve under the duty:

a _H: the exciting hammer is gone up the peak acceleration of test;

a _S: the peak acceleration of system testing;

F: the fundamental frequency of test or calculated rate;

Utilize and return m and κ that obtains and the k that demarcates ₀, bar and exciting hammer basic parameter M _H, A can measure the tension force N of prestress system

$N=\mathrm{pA}=A\&CenterDot;{\left[\frac{1}{\mathrm{\&kappa;}}(\frac{{4\mathrm{\&pi;}}^2{f}^2{M}_H{a}_H}{a_S\&CenterDot;A}-k_0)\right]}^{1/m}\&CenterDot;p_a---(1-4)$

Wherein, p: pressure is tension force (N)/lifting surface area A

A: lifting surface area is generally the area of backing plate.

p _a: atmospheric pressure can be taken as 105kPa.

Fig. 6 is the recurrence that the tension force～response relation to an anchor cable carries out.As can be seen, the coefficient R of its recurrence surpasses 0.99, illustrates that two straight line correlations between variable are very close, has fully proved the feasibility of this project theory/technology.

Claims (2)

1. a lossless detection method of testing tension of prestress anchorage system is characterized in that, operates as follows:

A. acceleration transducer is installed on the anchor head anchor clamps and exciting hammer of prestress anchorage system end, is connected to tester with signal cable;

B. with exciting hammer or aut.eq. exciting on the anchor head anchor clamps of prestress anchorage system, collecting test data;

C. the Relation Parameters of the response～tension force of prestress system is demarcated;

D. utilize and demarcate the parameter of trying to achieve, similar prestress system is carried out tension detection;

Concrete steps are:

D-1 determines the basic parameter of prestress system and exciting hammer: M _H, A;

M _H: the quality of exciting hammer;

A is the contact area of backing plate and component object, and unit is m ²

D-2 is provided with test macro

D-3 determines k ₀: at the tension force N that approaches zero ₀Test out f respectively down, ₀, a _H0, a _S0Thereby, calculate k ₀:

$k_0=\frac{4{\mathrm{\&pi;}}^2{f_0}^2{M}_H{a}_{H0}}{a_{S0}\&CenterDot;A};$

Wherein, f ₀: at the tension force N that approaches zero ₀Down, test obtains the prestress system natural frequency of vibration, and unit is Hz;

a _H0: at the tension force N that approaches zero ₀Down, the exciting hammer is gone up the peak acceleration of test;

a _S0: at the tension force N that approaches zero ₀Down, the peak acceleration of system testing;

k ₀: the initial rigidity of prestress system, unit is N/m ³

D-4 determines m and k: at several tension force N _iTest out f respectively down, _i, a _Hi, a _SiAnd p _i=N _i/ A, wherein, m is a pressure index, dimensionless; K is the surface of contact stiffness coefficient, and unit is N/m ³

f _i: at several tension force N _iDown, test obtains the prestress system natural frequency of vibration, and unit is Hz;

a _Hi: at several tension force N _iDown, the exciting hammer is gone up the peak acceleration of test;

a _Si: at several tension force N _iDown, the peak acceleration of system testing;

p _i=N _i/ A: at several tension force N _iDown, the compressive stress on the surface of contact, unit is N/m ²

Order $y_i=\ln \left(\frac{p_i}{p_a}\right)$

p _aBe atmospheric pressure, be taken as 105kPa,

$x_i=\ln (4{\mathrm{\&pi;}}^2{f}_i^2\frac{M_H{\mathrm{\&alpha;}}_{\mathrm{Hi}}}{a_{\mathrm{Si}}A}-k_0)$

Then can obtain regression equation:

y _i＝Bx _i+C

By straight-line regression, can obtain B and C,

B＝1/m

$C=-\frac{\ln \left(\mathrm{\&kappa;}\right)}{m}$

And then try to achieve m and k;

m＝1/B

k＝e ^-C/B；

The mensuration of d-5 tension force

Utilize and return m and k that obtains and the k that demarcates ₀, exciting hammer the basic parameter mass M _H, the area A that contacts with component object of backing plate can measure the tension force N of homotype prestress system

$N=\mathrm{pA}=A\&CenterDot;{\left[\frac{1}{\mathrm{\&kappa;}}(\frac{4{\mathrm{\&pi;}}^2{f}^2{M}_H{a}_H}{a_S\&CenterDot;A}-k_0)\right]}^{1/m}\&CenterDot;p_a,$

Wherein, P is a compressive stress on the surface of contact, and f is the natural frequency of vibration of prestress system, α _HBe the peak acceleration that records on the exciting hammer, α _sPeak acceleration for system testing.

2. according to the lossless detection method of the described test tension of prestress anchorage system of claim 1, it is characterized in that hitting exciting and vibratory response test all is to carry out on the anchor head of prestress system.

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