CN112162034B - A Damage Identification Method for Steel-Concrete Composite Beams Using Structural Noise - Google Patents

Abstract

The invention provides a steel-concrete composite beam damage identification method applying structural noise, which is characterized by comprising the following steps of: the steel-concrete combined beam is provided with a vibration response measuring point and a combined beam noise measuring point; knocking the combined beam by using a force hammer; the normal acceleration signal collected by the accelerometer and the noise signal collected by the microphone are connected to a receiver by a data line, and the receiver transmits the signals to a computer for processing. Establishing an accurate composite beam damage model by using ansys and taking the bolt nail connectivity of the composite beam, the steel beam crack height and the concrete slab crack width as variables, and introducing VAone to preliminarily analyze the noise change rule of the steel-concrete composite structure under different damage types and degrees; and judging the main damage type of the steel-concrete composite beam according to the change relation of the integral noise and the frequency of the composite beam. The invention provides a bridge safety evaluation technology which can continuously evaluate the health state of the whole structure in real time and determine the suspicious position of the damage.

Description

A Damage Identification Method for Steel-Concrete Composite Beams Using Structural Noise

technical field

The invention relates to the technical field of bridge model tests, in particular to a damage identification method for steel-concrete composite beams using structural noise.

Background technique

The steel-concrete composite beam connects the concrete slab and the steel beam as a whole by the shear connector, which can give full play to the good compressive performance of the concrete material and the good tensile performance of the steel. In practical engineering, steel-concrete composite girder bridges are affected by the dynamic and static loads of trains and the environment, and problems such as steel girder corrosion, fatigue cracks and stud fatigue damage will occur, resulting in the degradation of the overall and local stiffness of the composite girder. Seriously affect the safety of the bridge.

Scholars at home and abroad have done a lot of research and analysis on bridge structural damage identification methods, and have proposed many damage identification methods. Existing damage identification methods are mainly divided into two categories: global damage identification methods and local damage identification methods. The overall method mainly includes two types of structural damage identification methods based on dynamic characteristics and structural damage intelligent identification methods. Structural damage identification methods based on structural dynamic characteristics include damage identification based on natural frequency, mode shape change, mode shape curvature change, structural compliance matrix, unit modal strain energy change rate, etc.; structural damage intelligent identification methods include genetic algorithm, neural Network method, structural damage identification method based on piezoelectric impedance, etc. The local method relies on non-destructive testing technology to accurately detect, find, and describe the location of defects on specific components, including acoustic or ultrasonic methods, magnetic field methods, radar imaging, ray methods, eddy currents, and temperature field methods. But so far there has never been a precedent for the identification of structural damage through structural noise.

SUMMARY OF THE INVENTION

The invention provides a damage identification method for steel-concrete composite beams using structural noise, which aims to solve the shortcomings of the prior art, and provides a bridge that can continuously and real-time evaluate the health state of the overall structure and determine the suspicious locations where damage exists. security assessment techniques.

The technical scheme adopted by the present invention to solve its technical problems is:

A damage identification method for steel-concrete composite beams using structural noise, characterized in that:

There is a set of measurement points including three vibration response measurement points and four composite beam noise measurement points on the steel-concrete composite beam composed of supports, steel beams, and concrete slabs from bottom to top:

A vibration response measuring point is arranged on the upper surface of the concrete slab, and a composite beam noise measuring point is arranged at a distance of 10 cm from the normal position of the vibration response measuring point;

Vibration response measurement points are arranged on the side of the web of the steel beam, and composite beam noise measurement points are arranged at 10cm and 1m from the normal position of the vibration response measurement point;,

The vibration response measuring point is arranged on the upper surface of the lower flange plate of the steel beam, and the noise measuring point of the composite beam is arranged 10cm away from the normal position of the vibration response measuring point;

Place an accelerometer at each vibration response measurement point to measure the normal acceleration; place a microphone at each composite beam noise measurement point to measure the overall noise of the composite beam;

Use a force hammer as an excitation tool to strike each composite beam at intervals;

The normal acceleration signal collected by the accelerometer and the noise signal collected by the microphone are connected to the receiver with a data line, and the receiver transmits the signal to the computer for processing.

A set of measurement points including three vibration response measurement points and four noise measurement points of the composite beam are arranged on the 1/4, 1/2 and 3/4 sections of the composite beam respectively, and an accelerometer is placed at each vibration response measurement point to measure Normal acceleration; place a microphone at each composite beam noise measurement point to measure the overall noise of the composite beam.

Taking the bolt connection degree of composite beam, the crack height of steel beam, and the crack width of concrete slab as variables, an accurate composite beam damage model is established by ansys, and imported into VAone to preliminarily analyze the variation law of steel-concrete composite structure noise under different damage types and degrees; The main damage types of steel-concrete composite beams can be judged by the relationship between the overall noise and frequency of composite beams.

This patent makes the following assumptions about the medium and the sonic process:

(a) The sound wave has no energy loss during the propagation process, and the medium is an ideal fluid without viscosity.

(b) It is assumed that when the medium is not disturbed by the outside world, it is in a static state macroscopically, and the particle velocity v is 0. The uniformity of the medium can be represented by the static pressure P ₀ and the static density ρ ₀ .

(c) When the sound wave propagates, there is no heat exchange between the medium and the adjacent parts, that is, the medium is assumed to be adiabatic.

(d) The transmission process of sound waves can be regarded as small amplitude fluctuations, and each acoustic parameter can be replaced by a first-order trace amount. The static pressure P ₀ in the sound field is much larger than the sound pressure P, the sound speed c is much greater than the particle velocity v, and the wavelength of the sound wave is much larger than The particle displacement ξ is much larger than the wavelength λ of the sound wave.

According to the above-mentioned basic assumptions and three basic physical laws about the sum of the fluid medium and the sound wave, the equation of motion of the medium reflecting the relationship between the sound pressure p and the velocity v, the continuity equation of the relationship between the velocity v and the density increment ρ', and the sound The equation of state for the relationship between pressure p and density increment ρ'. The three equations are as follows:

为汉密尔顿算符号，

p代表瞬时声压，ρ₀代表静止密度，v代表质点速度，ρ代表媒质的密度增量，c代表声速，t代表时间。In the formula,

Calculate the symbol for Hamilton,

p represents the instantaneous sound pressure, ρ ₀ represents the static density, v represents the particle velocity, ρ represents the density increment of the medium, c represents the sound speed, and t represents the time.

其中P为流体内某一点的瞬时声压，P＝P(x,y,z)；c为声速，t为时间。

为三维拉普拉斯算子，其中拉普拉斯算子表达为

假设声压P随时间变化单频简谐变化，即：p(x,t)＝Re[p(x)e^iwt]。式中，Re为取实部；p(x)为声压的幅值；ω为圆频率，单位为rad/s；i为虚数单位，为书写方便省去Re。According to the above equation of motion, equation of state and continuity equation and basic assumptions, the three-dimensional wave equation of small-amplitude sound wave sound pressure of uniform ideal fluid medium, that is, the control equation of sound wave quantity, is derived.

where P is the instantaneous sound pressure at a certain point in the fluid, P=P(x, y, z); c is the speed of sound, and t is the time.

is the three-dimensional Laplacian operator, where the Laplacian operator is expressed as

It is assumed that the sound pressure P varies with time and a single-frequency simple harmonic variation, namely: p(x,t)=Re[p(x)e ^iwt ]. In the formula, Re is the real part; p(x) is the amplitude of the sound pressure; ω is the circular frequency in rad/s; i is the imaginary unit, and Re is omitted for the convenience of writing.

其中

k为波数。当结构发生损伤时，桥梁结构子系统的波数会因为损伤的类型和损伤程度的不同而发生变化，噪声也因波数的改变而产生响应的变化。By transforming the sound pressure P, the Helmholtz equation with sound pressure as a variable can be obtained as

in

k is the wave number. When the structure is damaged, the wave number of the bridge structural subsystem will change due to the different types and degrees of damage, and the noise will also change in response to the change of the wave number.

其中v_n为流体(声场)与结构交界面处结构的法向振速；j为单位虚数，

由此可知声场的边界条件由空气密度、结构圆频率和结构法向振动速度有关，当结构发生宿损伤时由于结构刚度、振动能量传递的变化导致结构频率和法向振动速度发生相应的改变。The solution of the Helmholtz equation is determined according to different boundary conditions. The boundary conditions of the sound field are generally considered to be the Neuman boundary conditions for the vibration and acoustic radiation of the bridge, that is, the fluid-solid interface:

where v _n is the normal vibration velocity of the structure at the interface between the fluid (sound field) and the structure; j is the unit imaginary number,

It can be known that the boundary conditions of the sound field are related to the air density, the circular frequency of the structure and the normal vibration velocity of the structure.

式中，p表示声压向量，r表示某一场点距声源的距离，S_Γ表示波振面的面积，Γ表示距离声源r处的波振面。When considering the solution of the sound radiation problem of the external sound field, it is necessary to assume that the noise does not have a reflected wave at infinity, and the sound wave satisfies the Sommerfield radiation conditions as follows:

In the formula, p represents the sound pressure vector, r represents the distance of a field point from the sound source, S _Γ represents the area of the wave vibration surface, and Γ represents the wave vibration surface at the distance r from the sound source.

The above content gives the basic governing equations of acoustic wave propagation in ideal fluids. The acoustic wave equation in the time domain and the Helmholtz equation in the frequency domain are both in the form of partial differential equations. The solution of the acoustic wave equation and the Helmholtz equation needs to determine the boundary conditions of the structure. and initial conditions, since the boundary conditions and initial conditions are difficult to obtain directly, consider using numerical methods to obtain their approximate solutions. The following lists the frequency domain sound field boundary integral equations and numerical discrete methods based on the Helmholtz equation.

(1) Basic solution

式中，x和y属于声场域Ω中的任意两点，分别为场点和源点；δ(x-y)为Dirac delta函数，G(x,y)为格林函数或者基本解，表示在y点处存在的单位强度的集中点源时，x点的响应。Converting the sound field Helmholtz equation into an equally small sound field boundary integral equation to solve requires the use of a basic solution. Mathematically, the basic solution of the sound field Helmholtz equation corresponds to the solution of the following equation, namely

In the formula, x and y belong to any two points in the sound field domain Ω, which are the field point and the source point respectively; δ(xy) is the Dirac delta function, G(x,y) is the Green function or the basic solution, which is expressed at the y point The response at point x when a concentrated point source of unit intensity exists at .

Integrate the basic solution, transform the coordinates, and according to the integral properties of the Dirac delta function, the Green's function in the three-dimensional space in the Cartesian coordinate system is obtained as G(x,y)=e ^-ikr /4πr

(2) Boundary integral equation

类似的Helmholtz方程对应的基本解的方程乘以p(y)沿Ω-积分有The integral equation of the sound field boundary has the difference between the inner sound field and the outer sound field. The figure below shows the solution domain of the inner sound field. y represents the field point, x represents the source point, Γ represents the sound field boundary, and Ω ^- represents the solution domain. According to the Helmholtz equation multiplied by the Green function G(x,y) along the integral, we have

The analogous Helmholtz equation corresponding to the fundamental solution equation multiplied by p(y) along Ω-integral has

Simultaneous two equations and transformed according to Green's second equation, we have

为内声场边界的法向向量，

为函数f的法向偏导数，

根据Dirac delta函数的积分性质，得

In the formula,

is the normal vector of the inner sound field boundary,

is the normal partial derivative of the function f,

According to the integral property of Dirac delta function, we get

式中,α^-(x)为与x位置有关的参量，定义为

且

If x is moved to the boundary Γ, all the unknowns in equation (2-46) are located on the boundary, then any point P in the region Ω can be obtained. Substitute the boundary conditions into the boundary integral equation to obtain the general relationship of the sound field boundary equation corresponding to the internal sound field problem, namely

In the formula, α ^- (x) is a parameter related to the position of x, which is defined as

and

式中

且

Similarly, the boundary integral equation of the external sound field can also be deduced to have

in the formula

and

The benefits of the present invention are:

The present invention belongs to an overall dynamic damage assessment method. Compared with the local method, the present invention can continuously evaluate the health state of the overall structure in real time, determine the suspicious position of damage, and has wide application prospects. In this patent, the measurement point position is selected on the surface of the composite beam and its vicinity, and the normal acceleration measurement device and the noise acquisition device are placed, so that the structure detection technology can be non-destructive and non-contact. This patent uses the characteristics of the noise in the frequency domain that can be reflected in the overall stiffness, local stiffness, and frequency mode shape caused by structural damage, and identifies the damage of steel-concrete composite beams through structural noise, providing a brand-new bridge safety assessment technology. research direction.

Description of drawings

The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

Figure 1 is a schematic diagram of the principle of the structural noise test device for steel-concrete composite beams;

Figure 2 is the front view of the arrangement of the measurement points of the steel-concrete composite beam structure noise test;

Figure 3 is the G-G section view of the structural noise test point layout of the steel-concrete composite beam.

Detailed ways

In order to illustrate the technical solutions of the present invention more clearly, the accompanying drawings required in the description will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention, which are not relevant to ordinary skills in the art. As far as personnel are concerned, other embodiments can also be obtained according to these drawings without any creative effort. In order to facilitate understanding of the present invention, the present invention will be described in more detail below with reference to the accompanying drawings and specific embodiments.

It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element, or one or more intervening elements may be present therebetween. When an element is referred to as being "connected" to another element, it can be directly connected to the other element or one or more intervening elements may be present therebetween. The terms "upper", "lower", "inner", "outer", "bottom" and other terms used in this specification indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention. The invention and simplified description do not indicate or imply that the device or element referred to must have a particular orientation, be constructed and operate in a particular orientation, and therefore should not be construed as limiting the invention. Furthermore, the terms "first," "second," "third," etc. are used for descriptive purposes only and should not be construed to indicate or imply relative importance.

As shown in Figure 1:

The steel-concrete composite beam consists of a support 300, a steel beam 200, and a concrete slab 100 from bottom to top.

The microphone adopts the MPA231 of Beijing Prestige, the dynamic range is 17-136dB, and the A frequency response range is 20-20kHz. The acceleration test uses the CA-YD-1181 piezoelectric acceleration sensor of Jiangsu Lianneng, with a range of 50g and a frequency response range of 0.5-10kHz. The main axis of the microphone must be consistent with the propagation direction of the sound wave, and the receiving end should be closer to the sound source. The data acquisition adopts the INV3060S acquisition instrument of Dongfang Institute.

To improve the frequency resolution, too high sampling frequency cannot be used. High-frequency sampling improves the accuracy of the time domain, while the accuracy of the frequency domain is the opposite. The frequency resolution can be expressed as

In the formula, N is the number of analysis points. The sampling frequency of the test is 10.24kHz. Both the microphone and the piezoelectric accelerometer were calibrated before testing.

The measured noise includes the influence of background noise, which needs to be filtered to remove the background noise. To remove background noise, press

In the formula, L _m - the sound pressure level of the measured noise, L _b - the sound pressure level of the background noise. The sound pressure time history measured on site is processed by a 10.24kHz high-pass filter.

The normal acceleration signal collected by the accelerometer 400 as the normal acceleration measuring device and the noise signal collected by the microphone 500 as the noise collecting device are connected to the DASP collecting instrument 700 as the receiver by the data line 600, and the DASP collecting instrument 700 will The signal is transmitted to the computer 800 for processing.

After the test instrument is connected, set the acquisition data path, acquisition instrument parameters, channel parameters, DASP V11 test parameters, etc. during the test according to the test test requirements and the use requirements of the test instrument, and check whether the settings are correct or not; Hammer to check the correctness of the connection of the test instrument and the working conditions of each test channel, so as to ensure that each channel can be collected normally during the test process, so as to avoid obtaining data or obtaining data with large errors during the test data collection process .

Using a force hammer as an excitation tool, each composite beam is struck. During the tapping process, try to keep the scene in an absolutely quiet state to ensure that the collected signals do not receive external interference. At the same time, the collected data needs to be filtered, signal amplification and other signal processing in the later stage. Every time there is a period of time between each tap, the next tap is performed immediately, and data is continuously collected by the DASP collector.

As shown in Figure 2 and Figure 3:

Select the position of the measuring point, and set three sets of measuring points:

The position of the 1/4 length section of the composite beam is the first group of measuring points:

The vibration response measuring point 11 of the steel beam 200 is arranged on the upper surface of the concrete slab 100 , the vibration response measuring point 12 is arranged on the side of the web 202 of the steel beam 200 , and the vibration response measuring point 13 is arranged on the lower flange plate of the steel beam 200 203 on the top surface. An accelerometer 400 is placed at the vibration response measuring point 11 , the vibration response measuring point 12 , and the vibration response measuring point 13 to measure the normal acceleration.

The composite beam noise measuring point 21 is arranged at 10 cm from the normal position of the vibration response measuring point 11, the composite beam noise measuring point 22 is arranged at 10 cm from the normal position of the vibration response measuring point 12, and the composite beam noise measuring point 23 is arranged at The distance from the vibration response measuring point 13 is 10 cm in the normal direction. In addition, the composite beam noise measuring point 24 is arranged at 1 m from the normal position of the vibration response measuring point 12 . A microphone 500 is placed at the composite beam noise measurement point 21 , the composite beam noise measurement point 22 , the composite beam noise measurement point 23 , and the composite beam noise measurement point 24 to measure the overall noise of the composite beam.

The position of the 1/2 length section of the composite beam is the second group of measuring points:

The vibration response measuring point 14 of the steel beam 200 is arranged on the upper surface of the concrete slab 100 , the vibration response measuring point 15 is arranged on the side of the web 202 of the steel beam 200 , and the vibration response measuring point 16 is arranged on the lower flange plate of the steel beam 200 203 on the top surface. Accelerometers 400 are placed at the vibration response measuring point 14 , the vibration response measuring point 15 , and the vibration response measuring point 16 to measure the normal acceleration.

The composite beam noise measuring point 25 is arranged at 10 cm from the normal position of the vibration response measuring point 14, the composite beam noise measuring point 26 is arranged at 10 cm from the normal position of the vibration response measuring point 15, and the composite beam noise measuring point 27 is arranged at The distance from the vibration response measuring point 16 is 10 cm in the normal direction. In addition, the composite beam noise measuring point 28 is arranged at 1 m from the normal position of the vibration response measuring point 15 . A microphone 500 is placed at the composite beam noise measurement point 25 , the composite beam noise measurement point 26 , the composite beam noise measurement point 27 , and the composite beam noise measurement point 28 to measure the overall noise of the composite beam.

The distribution of the first group of measuring points, the second group of measuring points, the accelerometers, and the microphones are all the same.

Since the vibration response measuring point 15 and the composite beam noise measuring point 26 are covered by the composite beam noise measuring point 28 in FIG. The position of the combined beam noise measuring point 24 and the vibration response measuring point 15 refers to the vibration response measuring point 12 in FIG. 3 , and the position of the combined beam noise measuring point 26 refers to the combined beam noise measuring point 22 in FIG. 3 .

The third group of measuring points is at the position of the 3/4 length section of the composite beam:

The vibration response measuring point 17 of the steel beam 200 is arranged on the upper surface of the concrete slab 100 , the vibration response measuring point 18 is arranged on the side of the web 202 of the steel beam 200 , and the vibration response measuring point 19 is arranged on the lower flange plate of the steel beam 200 203 on the top surface. Accelerometers 400 are placed at the vibration response measuring point 17 , the vibration response measuring point 18 , and the vibration response measuring point 19 to measure the normal acceleration.

The composite beam noise measuring point 29 is arranged at 10 cm from the normal position of the vibration response measuring point 17, the composite beam noise measuring point 30 is arranged at 10 cm from the normal position of the vibration response measuring point 18, and the composite beam noise measuring point 31 is arranged at The distance from the vibration response measuring point 19 is 10 cm in the normal direction. In addition, the composite beam noise measuring point 32 is arranged at 1 m from the normal position of the vibration response measuring point 18 . A microphone 500 is placed at the composite beam noise measurement point 29 , the composite beam noise measurement point 30 , the composite beam noise measurement point 31 , and the composite beam noise measurement point 32 to measure the overall noise of the composite beam.

The distribution of the first group of measuring points, the third group of measuring points, the accelerometers, and the microphones are all the same.

Since the vibration response measurement point 18 and the composite beam noise measurement point 30 are covered by the composite beam noise measurement point 32 in FIG. 2 , the three guiding lines point to the same point. Specifically, the position of the composite beam noise measurement point 32 is shown in FIG. 3 . The position of the composite beam noise measurement point 24, the vibration response measurement point 18 refers to the vibration response measurement point 12 in FIG. 3, and the position of the composite beam noise measurement point 30 refers to the composite beam noise measurement point 22 in FIG. 3.

Steel-concrete composite beam damage is identified by the following conclusions:

Through the 1/3 octave frequency domain analysis, the influence laws of the three single damage types on the composite beam noise are obviously different.

1: The two single working conditions of stud damage and concrete slab elastic modulus damage have no obvious influence on the overall vibration of the composite beam. In the 20-160Hz frequency band, the overall noise sound pressure value generated by the two working conditions is the largest compared to the no damage. not more than 15%; the crack damage of the steel beam contributes greatly to the overall vibration of the composite beam. In this frequency band, especially at 40 Hz, which is near the first-order vertical natural frequency of the composite beam, when the lower flange plate is cracked, the change The amplitude exceeds 15%, with the development of web cracks, the maximum can reach 30%.

The stud damage condition changes the constraint conditions of the composite beam and affects the local vibration of the composite beam. In the middle and high frequency band 160-2500Hz, the single stud damage condition produces a maximum change of about 50% in the overall noise sound pressure value compared with the non-damage condition; while the steel beam crack damage condition and the concrete slab elastic modulus damage combined The influence of the local vibration of the beam is small, and the maximum amplitude of the change in this frequency band does not exceed 15%.

2: When the coupled damage of the stud and the steel beam occurs, the overall stiffness of the composite beam is significantly reduced by the damage of the steel beam, and the change trend affected by the stud damage at medium and high frequencies is significantly different than that of the case without stud damage. The characteristics of two single damage cases are presented. When coupling damage occurs, in the 160-2500Hz frequency band, the overall noise sound pressure changes by about 50% compared with the non-damaged condition, and at 40Hz, that is, near the first-order vertical natural vibration frequency of the composite beam. , a decrease of about 23%.

3: Define the relative reduction value of noise and sound pressure of the composite beam at 40Hz, that is, near the first-order vertical natural frequency, as K;

In the formula, P ₀ is the noise sound pressure of the composite beam near the first-order vertical natural frequency of the non-destructive condition; P ₁ is the noise sound pressure of the composite beam near the first-order vertical natural frequency of the test condition.

When K>11%, the beam can be considered to be in an unsafe state. That is, when the noise sound pressure reduction degree of the composite beam near the first-order vertical natural vibration frequency is less than 11%, the composite beam is judged to be safe, and the noise sound pressure reduction degree of the composite beam near the first-order vertical natural vibration frequency is greater than At 11%, the composite beam is judged to be unsafe.

Therefore, the main damage types of steel-concrete composite beams can be judged by the relationship between the overall noise and frequency of composite beams, and the safety assessment of composite beams can be carried out.

The normal acceleration signal collected by the accelerometer 400 as the normal acceleration measurement device and the noise signal collected by the microphone 500 as the noise collection device are input into the computer, and the bolt connection degree of the composite beam, the steel beam crack height, and the concrete slab crack width are used as variable, use ansys to establish an accurate composite beam damage model, import it into VAone to preliminarily analyze the noise change law of steel-concrete composite structures under different damage types and degrees.

Combined with the investigation results of the existing actual steel-concrete composite beam structure on the damage type and damage degree of the composite beam, and considering the design parameters and construction status of the steel-concrete composite beam structure in the actual project, the noise of the steel-concrete composite beam structure is designed and implemented. Finally, the model is revised through the test data, and the damage of steel-concrete composite beams can be identified by using structural noise.

The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments, and the same and similar parts between the various embodiments can be referred to each other. The above description of the disclosed embodiments enables any person skilled in the art to make or use the present invention. Various modifications to these embodiments will be readily apparent to those skilled in the art, and the generic principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the invention. Thus, the present invention is not intended to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims (1)

1. a steel-concrete composite beam damage identification method using structural noise is characterized in that: There is a set of measurement points including three vibration response measurement points and four composite beam noise measurement points on the steel-concrete composite beam composed of supports, steel beams, and concrete slabs from bottom to top: A vibration response measuring point is arranged on the upper surface of the concrete slab, and a composite beam noise measuring point is arranged at a distance of 10 cm from the normal position of the vibration response measuring point; Vibration response measurement points are arranged on the side of the web of the steel beam, and composite beam noise measurement points are arranged at 10cm and 1m from the normal position of the vibration response measurement point; The vibration response measuring point is arranged on the upper surface of the lower flange plate of the steel beam, and the noise measuring point of the composite beam is arranged 10cm away from the normal position of the vibration response measuring point; Place an accelerometer at each vibration response measurement point to measure the normal acceleration; place a microphone at each composite beam noise measurement point to measure the overall noise of the composite beam; Use a force hammer as an excitation tool to strike each composite beam at intervals; Connect the normal acceleration signal collected by the accelerometer and the noise signal collected by the microphone to the receiver with a data cable, and the receiver transmits the signal to the computer for processing; Taking the bolt connection degree of composite beam, the crack height of steel beam, and the crack width of concrete slab as variables, an accurate composite beam damage model is established by ansys, and imported into VAone to preliminarily analyze the variation law of steel-concrete composite structure noise under different damage types and degrees; The main damage types of steel-concrete composite beams are judged by the relationship between the overall noise and frequency of composite beams; Steel-concrete composite beam damage is identified by the following conclusions: After 1/3 octave frequency domain analysis, In the 20-160Hz frequency band, the overall noise sound pressure value generated by the two working conditions of stud damage and concrete slab elastic modulus damage does not exceed 15% compared with the maximum amplitude without damage; at 40Hz, when the lower flange plate is cracked, The amplitude of change exceeds 15%, with the development of web cracks, the maximum is 30%; In the mid-to-high frequency band 160-2500Hz, the single stud damage condition produces a maximum 50% change in the overall noise sound pressure value compared with the non-damage condition; the steel beam crack damage condition and the concrete slab elastic modulus damage in the mid-to-high frequency band The maximum amplitude of the 160-2500Hz frequency band does not exceed 15%; When coupling damage occurs, in the 160-2500Hz frequency band, the overall noise sound pressure changes by 50% in the maximum amplitude compared with the non-damaged condition, and at 40Hz, it decreases by 23%; Define the relative reduction of noise and sound pressure of the composite beam at 40Hz as K;

In the formula, P ₀ is the noise sound pressure of the composite beam near the first-order vertical natural frequency of the nondestructive condition; P ₁ is the noise sound pressure of the composite beam near the first-order vertical natural frequency of the test condition; When K>11%, the beam is in an unsafe state; A set of measurement points including three vibration response measurement points and four noise measurement points of the composite beam are arranged on the 1/4, 1/2 and 3/4 sections of the composite beam respectively, and an accelerometer is placed at each vibration response measurement point to measure Normal acceleration; place a microphone at each composite beam noise measurement point to measure the overall noise of the composite beam.

Images