KR101055314B1 - Structural damage detection method using acceleration and strain signals - Google Patents

Abstract

PURPOSE: A method for detecting damage to a structure by using acceleration signal and strain is provided to prevent errors due to the finite differences approximation of the displacement derivative. CONSTITUTION: A method for detecting damage to a structure by using acceleration signal and strain comprises follows. The time average vibration wave detects a measuring target of simple beam shape. The shear force Q and bending moment M are estimated at a specific evaluation location of the measurement object by using a strain gage.

Description

Structural damage detection method using acceleration and strain signals

The present invention relates to a method of detecting damage of a structure using vibration power, and in particular, the vibration power is estimated by using the force (shear force, bending moment) measured by the strain gauge and the acceleration measured by the acceleration sensor. It is about damage detection method that can detect damage of structure more precisely and easily by calculating damage index.

In general, various damage detection methods or structural health monitoring techniques have been developed to prevent collapse of structures. The method of structural damage detection differs depending on whether the damage location can be predicted in advance, and can be classified into local damage detection and global damage detection.

Local damage detection is a method of identifying damage from changes in local response in the vicinity of the major structural member that is expected to be damaged, and global damage detection identifies damage from changes in the global response of a structure regardless of the location of the damage. It is a way.

The nondestructive evaluation (NDE) method has been applied to the above-described local damage detection method including visual inspection. Recently, various techniques using smart sensors such as fiber optic sensors (FOS) and piezoelectric (PZT) sensors have been developed.

Recently, a damage detection method of a structure using vibration power has been proposed.

In the method, as illustrated in FIG. 1, a plurality of acceleration sensors # 1, # 2, # 3, and # 4 are disposed on the measurement object V, and vibration power is measured using signals measured by the acceleration sensor. Estimate

The estimated vibration power is calculated as the damage index to detect damage to the structure.

That is, the shear sensor Q, bending moment M and vibration power are evaluated by the acceleration sensor.

를 측정한다.At this time, the acceleration response by the acceleration sensor for this purpose

Measure

를 아래의 수학식1에 의해 추산한다.Time-averaged vibration power using this

Is estimated by Equation 1 below.

[Equation 1]

와,

사이의 상호 스펙트럼 밀도이고 Im은 허수부이다.Where ω is the excitation frequency, ㅿ is the acceleration sensor interval, and G _ij is the vertical acceleration response

Wow,

Is the spectral density between and Im is the imaginary part.

Using such time average vibration power, damage index DI is calculated by Equation 2 below.

[Equation 2]

Such damage detection method is described in detail in Patent Registration No. 997810, and thus redundant description thereof will be omitted.

However, in the conventional damage detection method as described above, since the shear force Q and the bending moment M are estimated only by the acceleration signal as shown in Equation 1, the higher-order component (secondary and third-order) errors due to the finite difference approximation of the displacement derivative are In addition, there is a problem in that it is difficult to measure the acceleration signal due to the inflow of electromagnetic fields.

The present invention is to solve the above-mentioned problems, and since strain gauges are used instead of acceleration sensors when estimating shear force Q and bending moment M, strain gauges such as optical fiber sensors are not generated without high order component errors due to finite difference approximation of displacement derivatives. The purpose of this study is to provide a damage detection method of structures using acceleration and strain measurement because it can calculate reliable damage detection results without electromagnetic interference.

)와 속도의 일차 도함수(

)는 가속도를 이용하여 추산하는 구조물의 손상 탐지 방법에 그 특징이 있다.In order to achieve the above object, the present invention provides a method for detecting a damage location using a damage index calculated by time average vibration power, wherein the time average vibration power is a simple beam shape as a measurement target, The shear force Q and the bending moment M at a specific evaluation position are estimated using a strain gauge, but by the following Equation 3, the velocity at the specific evaluation position (

) And the first derivative of speed (

) Is characterized by the damage detection method of the structure estimated using acceleration.

&Quot; (3) "

(1)

(2)

(3)

(One)

(2)

(3)

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delete

delete

사이의 상호 스펙트럼 밀도이고 Im은 허수부이고, w는 변위(특정 평가 위치 x0에서의 변위)이다.Where ω is the excitation frequency, ㅿ is the acceleration sensor interval, and S _ij is the strain ε _i and the vertical acceleration

Is the imaginary part and w is the displacement (displacement at a specific evaluation position x0).

,

이다.In addition, velocity and the first derivative of velocity are

,

to be.

)는 상기 측정 평가 위치(x₀)지점을 중심으로 상기 측정 대상물의 일 표면에 위치한 2개의 가속도 센서(110,120)에 의해 측정될 수 있다.In this case, the shear force Q is measured by the first and second strain gauges (130,140) arranged in a v-shape on the basis of the measurement evaluation position (x ₀ ) in the simple beam-shaped measurement object (B), the bending moment (M) is measured by the third strain gauge 150 disposed on the bottom surface of the measurement object corresponding to the measurement evaluation position (x ₀ ), the acceleration (

) May be measured by two acceleration sensors 110 and 120 positioned on one surface of the measurement object with respect to the measurement evaluation position (x ₀ ).

In addition, the shear force Q may be estimated by Equation 4 below using the dynamic strain measured from the first strain gauge 130 and the second strain gauge 140.

&Quot; (4) "

단 k는 전단계수, A는 단면적,
G : shear modulus (

로 정의),
E: 영률,

는 프와송 비

: 제2스트레인 게이지에 의해 측정된 동적 변형률

: 제1스트레인 게이지에 의해 측정된 동적 변형률이다.

Where k is the shear modulus, A is the cross-sectional area,
G: shear modulus (

As defined),
E: Young's modulus,

The Poisson Rain

: Dynamic strain measured by a second strain gauge

: Dynamic strain measured by the first strain gauge.

In addition, the bending moment M may be estimated by Equation 5 below using the dynamic strain measured from the third strain gauge 150.

[Equation 5]

단 E : 영률, I : 단면 1차 모멘트, h : 측정 대상물의 두께

: 제3스트레인 게이지에 의해 측정된 동적 변형률

Where E is the Young's modulus, I is the first moment in cross section, and h is the thickness of the measurement object.

: Dynamic strain measured by a third strain gauge

와 수학식8에 의한 손상 후 진동파워

로 아래의 수학식 6에 의해 손상 지수(DI)로 산정될 수 있다.
단, 단 E : 영률, I : 단면 2차 모멘트, h : 측정 대상물의 두께,

: 제3스트레인 게이지에 의해 측정된 동적 변형률이다.In addition, the time average vibration power is the vibration power before damage by the following equation (7)

And vibration power after damage by Equation 8

The damage index (DI) can be calculated by Equation 6 below.
Where E is the Young's modulus, I is the secondary moment in cross section, and h is the thickness of the measurement object.

: Dynamic strain measured by the third strain gauge.

: 추산된 손상전의 진동파워

손상 후 진동파워
&Quot; (6) "

: Estimated vibration power before damage

Vibration power after damage

delete

[Equation 7]

단,

: 손상 전 측정 대상물의 진동파워의 전단력 성분

: 손상 전 측정 대상물의 진동파워의 굽힘 모멘트 성분

: 손상 전 측정 대상물의 변형율 ε_i 와 가속도

사이의 상호 스펙트럼 밀도

only,

: Shear force component of the vibration power of the measurement target before damage

: Bending moment component of vibration power of the measurement target before damage

: Strain ε _i and acceleration of the object to be measured before damage

Cross Spectral Density Between

[Equation 8]

단,

: 손상 전 측정 대상물의 진동파워의 전단력 성분

: 손상 전 측정 대상물의 진동파워의 굽힘 모멘트 성분

: 손상 전 측정 대상물의 변형율 ε_i 와 가속도

사이의 상호 스펙트럼 밀도

only,

: Shear force component of the vibration power of the measurement target before damage

: Bending moment component of vibration power of the measurement target before damage

: Strain ε _i and acceleration of the object to be measured before damage

Cross Spectral Density Between

In addition, the first and second strain gauges 130 and 140 are arranged to be in contact with each other, the lower end is arranged so as to be spaced apart from each other toward the upper end, the lower end of the mutual contact may be disposed at the center point in the width direction of the measurement object (B) have.

According to the present invention as described above, there is an effect capable of detecting damages more simply and precisely than before.

1 is a conceptual diagram illustrating a conventional damage detection method,
2 is a conceptual diagram illustrating a damage detection method of the present invention.

Before describing the various embodiments of the present invention in detail, it will be appreciated that the application thereof is not limited to the details of construction and arrangement of components described in the following detailed description or illustrated in the drawings.

The invention can be implemented and carried out in other embodiments and can be carried out in various ways.

In addition, device or element orientation (e.g., "front", "back", "up", "down", "top", "bottom" The expressions and predicates used herein with respect to terms such as "," left "," right "," lateral ", etc. are used merely to simplify the description of the present invention, It will be appreciated that the element does not simply indicate or mean that it should have a particular direction.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention.

Therefore, the embodiments described in the specification and the drawings shown in the drawings are only the most preferred embodiment of the present invention and do not represent all of the technical idea of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

Hereinafter, the present invention will be described in detail with reference to FIGS.

Example

The present invention uses the strain signal and the acceleration signal at a specific evaluation position in estimating the time average vibration power as described above.

In the related art, the acceleration signals are used in estimating the time average vibration power.

In the damage detection method proposed in Patent Registration No. 997810, since the acceleration signal is used to estimate the shear force and bending moment, there is a high order component error due to the finite difference approximation of the displacement derivative, and also to measure the acceleration signal due to the inflow of electromagnetic fields. There was a problem of difficulty.

The present invention solves this problem, and the shear force and bending moment are estimated by the strain gauge at a specific evaluation position, so that the error of the higher order components does not occur than in the prior art, so that the measurement of the signal is easy, and when the optical fiber sensor is used as the strain gauge, the electromagnetic field There is no interference, so you can measure more precisely.

)와 속도의 일차 도함수

는 가속도 센서에 의해 측정된 가속도를 이용하여 추산하되, 아래의 수학식3에 의한다.
In this case, the time average vibration power is a simple beam shape as the measurement object, and the shear force Q and the bending moment M at the specific evaluation position of the measurement object are estimated by using a strain gauge and the speed (

) And the first derivative of speed

Equation is estimated using the acceleration measured by the acceleration sensor, according to Equation 3 below.

(1)

(2)

[Equation 3]

(One)

(2)

(3)
단, P(x;), <P(x;t)>T : 시간평균 진동파워, ω : 가진 주파수

(3)
Where P (x;), <P (x; t)> T: time-averaged vibration power, ω: excitation frequency

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delete

delete

delete

Q: shear force, M: bending moment, w: displacement (displacement at specific evaluation position x0)

로 정의),
E: 영률,

는 프와송 비Where k is the shear modulus, E is the Young's Modulus, A is the cross-sectional area, and ㅿ is the acceleration sensor spacing.
G: shear modulus (

As defined),
E: Young's modulus,

The Poisson Rain

delete

delete

는 변형율

와 가속도

사이의 상호 스펙트럼 밀도, Im은 허수부이다.

Is strain

And acceleration

Cross spectral density between, Im is the imaginary part.

In this case, the subscripts 1 and 2 refer to the acceleration sensors 110 and 120 to be described later, and the subscripts 3, 4 and 5 refer to the strain gauges 130, 140 and 150 which will be described later.

According to the present invention described above it is possible to reduce the error than the prior art.

That is, in the conventional case, as shown in Equation 1 (1), the second to third order displacement derivatives are used, and there is a problem in that the error of the higher order component occurs due to the finite difference approximation of the displacement derivatives.

However, according to the present invention, as shown in Equation 3, only the first-order displacement derivative can be used to significantly reduce the error caused by the finite-difference approximation of the displacement derivative.

After estimating the time-averaged vibration power using Equation 3 described above, damage detection can be performed by a conventional method.

Meanwhile, as shown in FIG. 2, the shear force Q is disposed in a v-shape based on a measurement evaluation position in a simple beam-shaped measurement object B, and is installed to abut on a widthwise center point of the measurement object. And second strain gauges 130 and 140.

That is, as shown in FIG. 2, the lower ends of the first strain gauge 130 and the second strain gauge 140 are disposed to be in contact with each other, but are arranged to be spaced apart from each other toward the upper end so as to have an overall V shape.

In particular, it is preferable that the lower end portions which are in contact with each other are arranged at a center point in the width direction (height direction, direction z) of the measurement object B.

In this case, the first strain gauge 130 and the second strain gauge 140 may be disposed to be inclined by 45 degrees from the z-axis, respectively, as shown.

Meanwhile, the shear force Q may be estimated by Equation 4 below using the dynamic strain measured from the first strain gauge 130 and the second strain gauge 140.

&Quot; (4) &quot;

로 정의), Where k is the shear modulus and A is the cross-sectional area.
G: shear modulus (

As defined),

delete

delete

는 프와송 비

: 제2스트레인 게이지에 의해 측정된 동적 변형률E: Young's modulus,

The Poisson Rain

: Dynamic strain measured by a second strain gauge

: 제1스트레인 게이지에 의해 측정된 동적 변형률

: Dynamic strain measured by the first strain gage

The bending moment M may be measured by a third strain gauge 150 disposed on the bottom surface of the measurement object corresponding to the measurement evaluation position x ₀ .

In this case, the bending moment M may be estimated by Equation 5 below using the dynamic strain measured from the third strain gauge 150.

[Equation 5]

Where E is the Young's modulus, I is the secondary moment in cross section, and h is the thickness of the measurement object.

: 제3스트레인 게이지에 의해 측정된 동적 변형률

: Dynamic strain measured by a third strain gauge

는 상기 측정 평가 위치(x₀)지점을 중심으로 상기 측정 대상물의 일 표면에 위치한 2개의 가속도 센서(110,120)에 의해 측정될 수 있다.Acceleration for estimating the cross spectral density (S _ij )

May be measured by two acceleration sensors 110 and 120 positioned on one surface of the measurement object with respect to the measurement evaluation position (x ₀ ).

In this case, the acceleration sensors 110 and 120 may be arranged to be spaced apart from each other by the distance between the upper end surface of the measurement object (B) as shown.

On the other hand, kAG and bending stiffness EI, which represent the shear stiffness after damage in Equation (3) of Equation 3 cannot be predicted in advance, so that the unit stiffness (unit kAG) and bending stiffness (unit EI) Vibration power should be used.

와 손상 후 진동파워

를아래의 수학식7 및 수학식8에 의해 추산할 수 있다.
That is, vibration power before damage

And vibration after damage

Can be estimated by the following equations (7) and (8).

[Equation 7]

(1)

(One)

(2)

(2)

: 손상 전 측정 대상물의 진동파워의 전단력 성분only

: Shear force component of the vibration power of the measurement target before damage

: 손상 전 측정 대상물의 진동파워의 굽힘 모멘트 성분

: Bending moment component of vibration power of the measurement target before damage

: 손상 전 측정 대상물의 변형율 ε_i 와 가속도

사이의 상호 스펙트럼 밀도
kAG : 보의 전단강성, EI : 보의 굽힘 강성,
ω:가진 주파수, △ 가속도계 간격,
c : h/2 (단 h는 측정 대상물(보)의 두께)

: Strain ε _i and acceleration of the object to be measured before damage

Cross Spectral Density Between
kAG: Shear stiffness of beam, EI: Bending stiffness of beam,
ω: frequency, Δ accelerometer spacing,
c: h / 2 (where h is the thickness of the measurement object (beam))

[Equation 8]

(1)

(One)

(2)

(2)

: 손상 후 측정 대상물의 진동파워의 전단력 성분only

: Shear Force Component of Vibration Power of Measurement Object after Damage

: 손상 후 측정 대상물의 진동파워의 굽힘 모멘트 성분

: Bending moment component of the vibration power of the measurement object after damage

: 손상 후 측정 대상물의 변형율 ε_i 와 가속도

사이의 상호 스펙트럼 밀도

: Strain ε _i and acceleration of the measured object after damage

Cross Spectral Density Between

와 손상 후 진동파워

를 이용하여 아래의 수학식6에 의해 손상 지수(DI)를 산정할 수 있다.The vibration power before the damage thus estimated

And vibration after damage

The damage index (DI) can be calculated by using Equation 6 below.

&Quot; (6) &quot;

As described above, according to the method of the present invention applying equations (4) and (5) in the estimation of the shear force Q and the bending moment M, there are no higher-order component (secondary and third-order) errors due to finite difference approximation of the displacement derivatives than in the prior art. Using a fiber optic sensor as a strain gage allows more accurate measurements without electromagnetic interference.

110: first acceleration sensor 120: second acceleration sensor
130: first strain gauge 140: second strain gauge
150: third strain gauge

Claims (6)

In the method for detecting the damage location using the damage index calculated by the time average vibration power,
The time average vibration power is a simple beam shape as the measurement object, the shear force Q and the bending moment M at a specific evaluation position of the measurement object are estimated by using a strain gauge, according to Equation 3 below,
Velocity at the particular evaluation position (

) And the first derivative of speed

The damage detection method of the structure using the strain and the acceleration signal, characterized in that estimated using the acceleration measured by the acceleration sensor.
[Equation 3]

Where P (x;), <P (x; t)> T: time-averaged vibration power, ω: excitation frequency
Q: shear force, M: bending moment, w: displacement (displacement at specific evaluation position x0)

Where k is the shear modulus, E is the Young's Modulus, A is the cross-sectional area, and ㅿ is the acceleration sensor spacing.
G: shear modulus (

As defined),
E: Young's modulus,

The Poisson Rain

Is strain

And acceleration

Cross spectral density between, Im is the imaginary part. The method of claim 1,
The shear force Q is measured by the first and second strain gauges 130 and 140 arranged in a v shape with respect to the measurement evaluation position (x ₀ ) in a simple beam-shaped measurement object (B),
The bending moment M is measured by the third strain gauge 150 disposed on the bottom surface of the measurement object corresponding to the measurement evaluation position x ₀ ,
The acceleration (

) Is measured by two acceleration sensors (110, 120) located on one surface of the measurement object with respect to the measurement evaluation position (x ₀ ) point. The method of claim 2,
The shear force Q is estimated by Equation 4 below using the dynamic strain measured from the first strain gauge 130 and the second strain gauge 140, damage to the structure using the strain and acceleration signal Detection method.
[Equation 4]

Where k is the shear modulus and A is the cross-sectional area.
G: shear modulus (

As defined),
E: Young's modulus,

The Poisson Rain

: Dynamic strain measured by a second strain gauge

: Dynamic strain measured by the first strain gage The method of claim 2,
The bending moment M is a damage detection method of the structure using the strain and acceleration signal, characterized in that estimated by the following equation 5 using the dynamic strain measured from the third strain gauge (150).
&Quot; (5) &quot;

Where E is the Young's modulus, I is the secondary moment in cross section, and h is the thickness of the measurement object.

: Dynamic strain measured by a third strain gauge The method of claim 1,
The time average vibration power is the vibration power before damage by the following equation (7)

And vibration power after damage by Equation 8

Estimated by
Damage detection method of the structure using the strain and acceleration signal, characterized in that calculated by the damage index (DI) by the following equation (6).

&Quot; (6) &quot;

&Quot; (7) &quot;

ω

only

: Shear force component of the vibration power of the measurement target before damage

: Bending moment component of vibration power of the measurement target before damage

: Strain ε _i and acceleration of the object to be measured before damage

Cross Spectral Density Between
kAG: Shear stiffness of beam, EI: Bending stiffness of beam,
ω: frequency, Δ accelerometer spacing,
c = h / 2 = (thickness of beam) / 2

&Quot; (8) &quot;

only

: Shear Force Component of Vibration Power of Measurement Object after Damage

: Bending moment component of the vibration power of the measurement object after damage

: Strain ε _i and acceleration of the measured object after damage

Cross Spectral Density Between
c: h / 2 (where h is the thickness of the measurement object) The method of claim 2,
The first and second strain gauges 130 and 140 are disposed to be in contact with each other at the lower end, but are spaced apart from each other toward the upper end.
The lower end portion which abuts each other is disposed at the center point in the width direction of the measurement object (B), the damage detection method of the structure using the strain signal and the acceleration signal.

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