CN115200817A - A modal perception analysis system and method for cement concrete pavement structure - Google Patents

Abstract

The invention relates to a cement concrete pavement structure modal perception analytic system and a method, the system comprises a pavement structure body, an optical fiber demodulator, a modal analysis device and a plurality of pavement vibration perception devices which are connected in sequence, the pavement vibration perception devices adopt distributed vibration optical fiber units, all the distributed vibration optical fiber units are buried in the pavement structure body, each distributed vibration optical fiber unit is provided with at least one measuring point, and each distributed vibration optical fiber unit is connected with the optical fiber demodulator and the modal analysis device in sequence.

Description

A modal perception analysis system and method for cement concrete pavement structure

technical field

The invention relates to the technical field of road engineering, in particular to a modal perception analysis system and method for a cement concrete pavement structure.

Background technique

Cement concrete pavement has the advantages of high bearing capacity and good durability, so it is widely used in heavy-duty transportation in my country. However, under the influence of high frequency and heavy load and complex environment, road surface diseases frequently occur and service performance decreases. Because the maintenance of cement concrete pavement is difficult, it is necessary to evaluate and analyze the structural damage of cement concrete pavement. In the current structural damage assessment, modal analysis methods are widely used. The modal characteristics can reflect the vibration characteristics of the structure itself, and are closely related to the damage of the structure. Typical modal characteristic parameters include modal natural frequency, modal mode shape, modal damping, etc. The identification of these parameters is an important task in modal analysis of civil structures.

The modal analysis of cement concrete pavement and even various concrete structures focuses on the measurement of structural vibration, and the key to structural vibration measurement lies in multi-point acquisition and reliability and durability. Currently, the most widely used are single-point accelerometers, displacement sensors, etc. Sensing technology has gradually developed from piezoelectric sensing to more stable and durable optical fiber sensing. However, traditional single-point sensors cannot fully meet the needs of multi-point acquisition and reliability and durability: First, traditional piezoelectric sensors are easily affected by complex environments such as noise and electromagnetic fields, and have insufficient long-term durability; second, single-point optical fiber sensing The high price of conventional sensors limits the number of deployments, and it is even more difficult to achieve large-scale multi-point acquisition for pavement structures with long mileage and a wide range. Moreover, the conventional surface-mounted accelerometer used in the prior art can only be used during detection, and the accelerometer needs to be removed when there is a natural vehicle running, and the installation before detection and removal after detection are very cumbersome. Therefore, there is an urgent need for a modal perception system and analytical method for cement concrete pavement structures that are inexpensive and suitable for large-area layout.

SUMMARY OF THE INVENTION

The purpose of the present invention is to provide a modal perception analysis system and method for cement concrete pavement structure in order to overcome the above-mentioned defects of the prior art. The invention can effectively expand the scope of modal analysis of pavement structures and greatly reduce the Cost of analytics and health monitoring with high accuracy and durability.

The object of the present invention can be realized through the following technical solutions:

According to one aspect of the present invention, the present invention provides a modal perception analysis system for a cement concrete pavement structure, including a pavement structure body, an optical fiber demodulator, a modal analysis device, and a plurality of pavement vibration sensing devices connected in sequence. The vibration sensing device adopts distributed vibration optical fiber units, all the distributed vibration optical fiber units are embedded in the pavement structure body, each distributed vibration optical fiber unit is provided with at least one measuring point, and each distributed vibration optical fiber unit is The units are connected to the optical fiber demodulator and the modal analysis device in sequence.

Preferably, the distributed vibration optical fiber unit is formed by a distributed vibration optical fiber wound in a ring shape, and two adjacent distributed vibration optical fiber units are connected by an optical fiber, and each distributed vibration optical fiber unit is connected to the optical fiber through an optical fiber. The optical fiber demodulator and the modal analysis device are connected in sequence.

Preferably, the number of winding turns of the distributed vibration optical fiber unit is related to the winding diameter and the pulse width of the optical fiber demodulator, and the winding diameter of the distributed vibration optical fiber unit is related to the two adjacent distributed vibration optical fibers. The spacing between elements is related to the desired modal spatial resolution;

The formula describing the relationship between the number of winding turns of the distributed vibrating optical fiber unit and the winding diameter and the pulse width of the optical fiber demodulator is:

nπd≥W

In the formula, n is the winding number of the distributed vibration optical fiber unit, d is the winding diameter of the distributed vibration optical fiber unit, and W is the pulse width of the fiber demodulator;

The formula describing the relationship between the winding diameter of the distributed vibration fiber unit, the spacing between two adjacent distributed vibration fiber units, and the desired modal spatial resolution is:

d+s=L

Among them, d is the winding diameter of the distributed vibration fiber unit, s is the distance between the outer diameters of two adjacent distributed vibration fiber units, and L is the desired modal spatial resolution.

Preferably, the set number of the distributed vibrating fiber units should satisfy:

N(nπd+l ₀ )+l ₁ ≤W _max

In the formula, N is the total number of distributed vibration optical fiber units for modal perception analysis of cement concrete pavement structure, _l0 is the total length of optical fibers connected between adjacent distributed vibration optical fiber units, _l1 is the connection fiber demodulator Compared with the length of the outgoing fiber of the distributed vibrating fiber unit, W _max is the maximum demodulation distance of the fiber demodulator.

According to another aspect of the present invention, the present invention provides a perceptual analysis method applying the modal perceptual analysis system of cement concrete pavement structure as described above, comprising the following steps:

S1: Obtain the vibration signals of all measuring points, and preprocess all the vibration signals;

S2: Perform a pairwise combination of all the vibration signals preprocessed by S1, and perform power spectral density analysis. The power spectral density analysis includes the self-power spectral density analysis of the same measuring point and the cross-power spectral density analysis between different measuring points;

S3: Calculate the normalized power spectral density of each measuring point at each frequency value according to the power spectral density obtained by S2, and combine the normalized power spectral density of each measuring point and each frequency to obtain the global power spectrum density;

S4: Analyze the natural frequency of the pavement structure mode according to the global power spectral density obtained in S3;

S5: According to the natural frequency obtained in S4, obtain the mode shape vector at the natural frequency, and then obtain the three-dimensional appearance field of the mode shape vector in the actual space;

S6: Perform modal analysis on the pavement structure according to the natural frequency obtained in S5 and the three-dimensional appearance field of the mode shape vector obtained in S6 in the actual space.

Preferably, the formula for describing the power spectral density analysis in S2 is:

In the formula, f is the sampling frequency, Δf is the unit bandwidth, T is the total duration of vibration acquisition, t is a certain moment during the acquisition period, x _i (t) is the vibration signal of measuring point i at time t, x _j (t ) represents the vibration signal of measuring point j at time t. When i=j, G _ij (f) is the self-power spectral density; when i≠j, G _ij (f) is the cross-power spectral density.

Preferably, the formula for describing the normalized power spectral density PSD _r (f _l ) of the measuring point r at the lth discrete frequency f _l in S3 is:

In the formula, n _s is the total number of measurement points contained in the modal perception analysis system, f _l is the l-th discrete frequency in the analysis frequency band, and the total number of discrete frequencies is related to the total sampling time T and sampling frequency f, G _ir (f _l ) is the value of the cross power spectral density of the measuring point i and the measuring point r at f _l , and G _ij (f _l ) is the value of the cross power spectral density of the measuring point i and the measuring point j at f _l .

Preferably, the formula for describing the global power spectral density in S3 is:

where PSD is the global power spectral density, f ₁ is the first discrete frequency, equal to 0Hz, and f _h is the last discrete frequency, equal to 0.5f, which is half the sampling frequency.

Preferably, the S4 includes the following steps:

S4.1: In the global power spectral density obtained in S3, for the global power spectral density of each measuring point, obtain the steady state diagram corresponding to the measuring point based on the curve fitting method;

S4.2: Superimpose the steady-state graphs of each measuring point to obtain the empty-frequency fields of different steady-state points in the steady-state graph;

S4.3: Project the result of the empty-frequency field of the steady-state point into the frequency domain, obtain the distribution of the steady-state point at different frequencies, and pick the peak value as the natural frequency.

Preferably, the S5 includes the following steps:

S5.1: Obtain the ratio of the power spectral density of each measuring point at the natural frequency obtained in S4, and then obtain the mode shape vector A at the natural frequency;

S5.2: Determine the correspondence between each measuring point and the actual spatial position of the distributed vibrating fiber unit;

S5.3: According to the number of measuring points in different rows and columns, map the mode shape vectors of all measuring points to their respective rows and columns;

S5.4: Combine the elements in the mode shape vector of different rows and columns to form a three-dimensional appearance field of the mode shape vector in the actual space, and the row and column correspond to the length and width of the real cement concrete panel respectively.

Compared with the prior art, the present invention has the following advantages:

1. A cement concrete pavement structure modal perception analysis system provided by the present invention adopts distributed vibration optical fiber units as pavement vibration sensing devices, and performs structural vibration measurement through distributed vibration optical fiber units. The distributed vibration optical fiber units are about 1 yuan/m , the monitoring unit corresponding to a single accelerometer is only 10 yuan/unit, while the price of a high-precision accelerometer for structural monitoring is about 2,500 yuan/unit, which greatly reduces the structural modal analysis and health monitoring in the prior art. the cost of.

2. The distributed vibration optical fiber unit adopted by the modal perception analysis system for cement concrete pavement structure provided by the present invention can cover a large number of areas of the pavement panel by wrapping circles. Traditional accelerometers effectively expand the scope of structural modal analysis, from point to surface.

3. A cement concrete pavement structure modal perception analysis system provided by the present invention is embedded in the pavement structure body, the structural modal perception and analysis process will not affect the traffic operation, and solves the problem of the conventional surface-mounted accelerometer in the prior art. Can only be used during detection, issues that need to be removed when there is a natural vehicle running.

4. The perceptual analysis method provided by the present invention is applied to a modal perception and analysis system for a cement concrete pavement structure proposed by the present invention, so that the system can realize the modal analysis of the pavement structure, and can effectively analyze the modal frequency and modal vibration. modal characteristics, etc.

Description of drawings

FIG. 1 is a schematic structural diagram of a modal perception analysis system for a cement concrete pavement structure provided in this embodiment.

FIG. 2 is a schematic flowchart of a method for modal perception analysis of a cement concrete pavement structure provided in this embodiment.

FIG. 3 is a schematic diagram of the layout of the embodiment shown in FIG. 1 .

FIG. 4 is a diagram of a vibration signal measured using the embodiment shown in FIG. 1 .

FIG. 5 is a normalized power spectral density obtained by using the embodiment shown in FIG. 2 .

FIG. 6 is a global power spectral density field obtained by using the embodiment shown in FIG. 2 .

FIG. 7 is a steady state diagram of a single measuring point obtained by using the embodiment shown in FIG. 2 .

FIG. 8 is the space-frequency field of all steady state points acquired using the embodiment shown in FIG. 2 .

FIG. 9 is a frequency domain distribution diagram of steady-state points obtained by using the embodiment shown in FIG. 2 .

FIG. 10 is a three-dimensional appearance field of the mode shape vector obtained by using the embodiment shown in FIG. 2 in real space.

Figure 11 is a graph of the power spectral density measured with a high-precision accelerometer.

FIG. 12 is a comparison diagram of the results of the mode shape vector measured by the distributed vibration optical fiber unit and the high-precision accelerometer in the embodiment shown in FIG. 1 .

Detailed ways

The present invention will be described in detail below with reference to the accompanying drawings and specific embodiments.

Example

Referring to Fig. 1, according to one aspect of the present invention, the present invention provides a modal perception analysis system for cement concrete pavement structure, including: a pavement structure body, an optical fiber demodulator, a modal analysis device and a plurality of sequentially connected pavements Vibration sensing device, road vibration sensing device adopts distributed vibration optical fiber unit, all distributed vibration optical fiber units are embedded in the pavement structure body, each distributed vibration optical fiber unit has at least one measuring point, and each distributed vibration optical fiber unit has at least one measuring point. All of them are connected to the fiber demodulator and the modal analysis device in turn through the lead-out fiber.

As an optional embodiment, the distributed vibration optical fiber unit is formed by winding the distributed vibration optical fiber in a ring shape, the diameter of the distributed vibration optical fiber unit is related to the desired modal spatial resolution, and the number of winding turns of the distributed vibration optical fiber unit And the winding diameter is limited by the pulse width of the fiber demodulator.

As an optional embodiment, all the distributed vibration optical fiber units and the connections between adjacent distributed vibration optical fiber units are made of one optical fiber.

The formula describing the relationship between the number of winding turns of the distributed vibrating fiber unit and the winding diameter and the pulse width of the fiber demodulator is:

nπd≥W

In the formula, n is the winding number of the distributed vibration fiber unit, d is the winding diameter of the distributed vibration fiber unit, and W is the pulse width of the fiber demodulator.

As an optional implementation manner, the winding diameter of the distributed vibration optical fiber unit, the spacing between two adjacent distributed vibration optical fiber units, and the desired modal spatial resolution satisfy the following relationship:

d+s=L

Among them, s is the distance between the outer diameters of two adjacent distributed vibration fiber units, and L is the desired modal spatial resolution.

As an optional implementation manner, the number of distributed vibrating fiber units should satisfy:

N(nπd+l ₀ )+l ₁ ≤W _max

In the formula, N is the total number of distributed vibration optical fiber units for modal perception analysis of cement concrete pavement structure, _l0 is the total length of optical fibers connected between adjacent distributed vibration optical fiber units, _l1 is the connection fiber demodulator Compared with the length of the outgoing fiber of the distributed vibration fiber unit in the board, W _max is the maximum demodulation distance of the fiber demodulator.

As an optional implementation manner, the layout results of the distributed vibrating optical fiber units will form a corresponding relationship with the plane coordinates of the pavement structure.

As an optional embodiment, the pavement structure body is one or more combinations of a cement concrete pavement structure and a cement overlaid asphalt concrete pavement structure.

The working principle of a cement concrete pavement structure modal perception analysis system provided by the present invention is as follows:

The distributed vibration optical fiber unit senses the vibration signal of the pavement structure body and transmits it to the optical fiber demodulator. The optical fiber demodulator receives the vibration signal and outputs it to the modal analysis device, and the modal analysis device analyzes and processes all the vibration signals. When the pavement structure body needs to be detected, the excitation load is used to tap the pavement structure body to be detected, and the vibration signal is sensed and analyzed by the cement concrete pavement structure modal perception analysis system of the present invention.

Referring to Figure 2, according to another aspect of the present invention, the present invention provides a modal perception analysis method for cement concrete pavement structure, comprising the following steps:

S1: Obtain the vibration signals x _i (t) of all measuring points through the distributed vibration optical fiber unit, where i is the number of the measuring points, and preprocess all the vibration signals;

Specifically, the preprocessing includes any one or a combination of band-pass filtering, high-pass filtering and low-pass filtering.

S2: Perform a pairwise combination of all the vibration signals preprocessed by S1, and perform power spectral density analysis. The power spectral density analysis includes the self-power spectral density analysis of the same measuring point and the cross-power spectral density analysis between different measuring points;

Specifically, the formula describing the power spectral density analysis is:

In the formula, f is the sampling frequency, Δf is the unit bandwidth, T is the total duration of vibration acquisition, t is a moment in the acquisition period, x _i (t) is the vibration signal of measuring point i at time t, x _j (t) Represents the vibration signal of measuring point j at time t. When i=j, G _ij (f) is the self-power spectral density; when i≠j, G _ij (f) is the cross-power spectral density.

S3: Calculate the normalized power spectral density of each measuring point at each frequency value according to the power spectral density obtained by S2, and combine the normalized power spectral density of each measuring point and each frequency to obtain the global power spectrum density;

Specifically, the formula describing the normalized power spectral density PSD _r (f _l ) of the measuring point r at the lth discrete frequency f _l is:

In the formula, n _s is the total number of measurement points contained in the modal perception analysis system, f _l is the l-th discrete frequency in the analysis frequency band, and the total number of discrete frequencies is related to the total sampling time T and sampling frequency f, G _ir (f _l ) is the value of the cross power spectral density of the measuring point i and the measuring point r at f _l , and G _ij (f _l ) is the value of the cross power spectral density of the measuring point i and the measuring point j at f _l .

Specifically, the formula describing the global power spectral density is:

where PSD is the global power spectral density, f ₁ is the first discrete frequency, equal to 0Hz, and f _h is the last discrete frequency, equal to 0.5f, which is half the sampling frequency.

As an optional implementation manner, the recording method of the global power spectral density includes a matrix and a two-dimensional picture, the matrix elements of each row or the pixels of the picture represent a certain measurement point, and the matrix elements of each column or the pixels of the picture represent a specific frequency value.

S4: analyze the natural frequency f _n of the pavement structural mode according to the global power spectral density obtained in S3;

Specifically, according to the global power spectral density, it is determined that the power spectral density is significantly higher than a certain frequency value in other frequency bands at all measuring points, and this frequency belongs to the global modal characteristic, that is, the natural frequency of the structure.

S4.1: In the global power spectral density PSD obtained in S3, for the global power spectral density of each measuring point, obtain the steady state diagram corresponding to the measuring point based on the curve fitting method;

S4.2: Superimpose the steady-state graphs of each measuring point to obtain the empty-frequency fields of different steady-state points in the steady-state graph;

S4.3: Project the result of the empty-frequency field of the steady-state point into the frequency domain, obtain the distribution of the steady-state point at different frequencies, and pick the peak value as the natural frequency.

S5: According to the natural frequency obtained in S4, obtain the mode shape vector at the natural frequency, and then obtain the three-dimensional appearance field of the mode shape vector in the actual space;

S5.1: Obtain the ratio of the power spectral density of each measuring point at the natural frequency f _n obtained in S4, and then obtain the mode shape vector A(f _n ) at the natural frequency f _n ;

The formula describing the mode shape vector A(f _n ) at the natural frequency f _n is:

In the formula, A _r (f _n ) is the mode shape vector of the measuring point r at the natural frequency f _n , and is also the rth component of A(f _n ).

S5.2: Determine the correspondence between each measuring point and the actual spatial position of the distributed vibrating fiber unit;

Specifically, for the distributed vibration fiber unit in the pth row and the qth column, the corresponding relationship between the actual space position of the distributed vibration fiber unit and the measuring point can be expressed as a 1× _ns matrix Π _pq , the matrix The kth element can be expressed as:

S5.3: According to the number of measuring points in different rows and columns, map the mode shape vectors of all measuring points to their respective rows and columns.

为实际空间第i行第j列位置上固有频率f_n对应的振型矢量，n_s为测点总个数，Π_ij为第i行第j列的单元与全体测点的位置对应关系矩阵。In the formula,

is the mode shape vector corresponding to the natural frequency f _n at the position of the i-th row and the j-th column in the actual space, n _s is the total number of measuring points, and Π _ij is the position correspondence matrix between the unit of the i-th row and the j-th column and all the measuring points .

行与列分别对应真实水泥混凝土面板的长与宽。S5.4: Combine the elements in the mode shape vectors of different rows and columns to form the three-dimensional appearance field of the mode shape vectors in the actual space

The rows and columns correspond to the length and width of the real cement concrete panel, respectively.

S6: Perform modal analysis on the pavement structure according to the natural frequency obtained in S5 and the three-dimensional appearance field of the mode shape vector obtained in S6 in the actual space.

The above-mentioned optional embodiments can be combined arbitrarily to obtain a better embodiment, and the best embodiment obtained by combining all the optional embodiments will be described in detail below:

A full-scale test was carried out outside the Earthquake Engineering Museum of Tongji University, and a cement concrete pavement structure of 5m×4m was poured, and a modal perception analysis system for the cement concrete pavement structure was installed. The measurement range of the perception analysis system covers the entire area to be measured as much as possible.

Among them, the pavement vibration sensing device adopts the distributed vibration optical fiber unit, and the optical fiber demodulator adopts the BOFDA demodulator. The minimum spatial resolution of the BOFDA demodulator, that is, the pulse width is 4m. Therefore, the winding number n and winding diameter d of the distributed vibration fiber unit should satisfy:

nπd≥W=4

Combined with the convenience of construction, the number of winding turns of each distributed vibration fiber unit is set to 4, the winding diameter is 0.4m, and the length of the fiber contained in each distributed vibration fiber unit is 5m.

In this modal analysis, the expected spatial resolution is 0.5m, so the distance between two adjacent distributed vibration fiber units is:

s=L-d=0.5m-0.4m=0.1m

The maximum demodulation distance of the fiber demodulator is 10km, the length of the connecting segment between adjacent fiber units is 0.5m, the length of the lead fiber connecting the fiber demodulator and the fiber unit in the board is 10m, and the distributed vibrating fiber unit The quantity should satisfy:

N(nπd+l ₀ )+l ₁ ≤W _max

Combined with the modal analysis requirements of this structure, a total of 45 distributed vibrating optical fiber units are arranged in 9 rows and 5 columns. The spacing between rows and columns is 0.1m.

At the same time, a commercial high-precision accelerometer is arranged at each of the four positions that coincide with the distributed vibration fiber unit, which can be used for the comparison and verification of the modal analysis results.

See Figure 3 for the layout of the vibration modal perception analysis system for cement concrete pavement.

A portable falling weight deflectometer (PFWD) was used as the excitation load to excite the road panel at 15 points.

The measured vibration signal is output by the optical fiber demodulator. In the process of sequentially exciting the vibration, the vibration response signals of the measuring points 151, 155 and 159 are shown in Figure 4. There are 250 measuring points in total, calculate the self/cross power spectral density G _ij between different measuring points, and then calculate the normalized power spectral density PSD _i (f) of each measuring point at each frequency value. The normalized power spectral densities of 151, 155, and 159 are shown in Figure 5. Finally, the normalized power spectral density at each measuring point and each frequency is combined to obtain the global power spectral density field PSD as shown in Figure 6. In this embodiment, the global power spectral density field is represented as a two-dimensional picture, and each row A pixel represents a measurement point, and each column of pixels represents a specific frequency value.

Referring to FIG. 6 , each row of pixel points represents the power spectral density of one measurement point, corresponding to the power spectrum curve in FIG. 7 . Using the curve fitting method, the steady state diagram of the measuring point is obtained as shown in Figure 7. By superimposing the steady-state graphs of each measuring point together, the distribution of all steady-state points in the space-frequency field can be observed, as shown in Figure 8. The distribution of all steady-state points in the frequency domain in Fig. 8 is counted, and the distribution diagram of Fig. 9 is obtained. According to the perceptual analysis method of the modal of the cement concrete pavement structure, each peak in FIG. 9 is the natural frequency of each order of the cement concrete pavement structure in this embodiment. The first peak is 43.44Hz, which corresponds to the first-order natural frequency.

Extract the power spectral density of each point at the natural frequency f _n at the natural frequency of 43.44 Hz, and perform curve fitting on the power spectral density to obtain the mode shape vector A (43.44 Hz) at the frequency of this order.

In this embodiment, the modal perception analysis system for cement concrete pavement structure includes 45 distributed vibration optical fiber units in 9 rows and 5 columns, corresponding to 50 measuring points in total, and the corresponding relationship between each measuring point and the actual spatial position can be expressed as A 1×250 matrix. For example, for the distributed vibrating optical fiber unit in the first row and the first column, including 5 measuring points, the corresponding relationship between the distributed vibrating optical fiber unit and the measuring points can be expressed as:

Π ₁₁ =(1 1 1 1 1 0 L 0) _1×250

如图10所示。The three-dimensional appearance field of the mode shape vector in the real space can be obtained by coordinate transformation

As shown in Figure 10.

The accuracy of the modal perception analysis system and method for a cement concrete pavement structure provided by the present embodiment is verified below:

The modal analysis results obtained by the modal perception analysis system and method for a cement concrete pavement structure provided in this embodiment are tested by using high-precision accelerometers arranged at the same plane position. The power spectral density measured by the high-precision accelerometer is shown in Figure 11, and the natural frequency of the structure obtained from the four measuring points can be obtained from Figure 11 is 64.38Hz. The result of the pavement vibration modal sensing system consisting of distributed vibrating fiber units is 64.70 Hz, with a relative error of <0.5% from the accelerometer.

The Modal Confidence Criterion (MAC) is used to quantify the proximity of the four distributed vibrating fiber elements to the mode shape vectors measured by the four high-precision accelerometers:

均为振型矢量，为列向量。MAC越大，表示

相关性越高。通常认为MAC>0.9为相关，MAC<0.05为不相关。如图12所示，光纤环与加速度计所测振型矢量的MAC为0.99，说明两个振型矢量极为接近。进一步证明了本实施例提供的水泥混凝土路面结构模态感知解析系统中分布式振动光纤单元的有效性和准确性。where:

Both are mode shape vectors and are column vectors. The larger the MAC, the more

higher correlation. It is generally considered that MAC>0.9 is relevant, and MAC<0.05 is not relevant. As shown in Figure 12, the MAC of the mode shape vector measured by the fiber loop and the accelerometer is 0.99, indicating that the two mode shape vectors are very close. This further proves the effectiveness and accuracy of the distributed vibration optical fiber unit in the modal perception analysis system for the cement concrete pavement structure provided in this embodiment.

The long-term validity of the modal perception analysis system and method for a cement concrete pavement structure provided by the present embodiment is verified below:

A full-scale cement concrete pavement structure was built in the Earthquake Engineering Museum of Tongji University. In June 2020 and December 2020, this embodiment was used to provide a modal perception analysis system and method for cement concrete pavement structures to conduct two batches of vibration tests and modalities. Characteristics. Based on the strain inversion of the pavement modulus, the results show that the modulus of the pavement panel in December increased by 18.7% compared with that in June, which may be mainly due to the decrease in ambient temperature. According to the results of the two tests of each plate, the table below summarizes the first 4 orders of frequencies in the two tests of each plate.

The first 4 order frequencies of the two tests of each plate

Remarks: The average power spectrum of the second test of No. B board is confused in the first two modes, and the second frequency is not identified.

From the results in the table, it can be found that the first 4-order frequencies of the six boards are 12.21Hz, 15.87Hz, 20.75-23.19Hz, 28.08Hz in the first test; the first 4-order frequencies in the second test are 12.21Hz. , 17.09Hz, 24.41～25.63Hz, 35.4～37.84Hz. The average increase in the first 4-order frequencies is 0, 7.69%, 16.46%, and 28.99%, respectively. The natural frequencies of the first 4 orders all increase, and the increase range increases with the increase of the order. This law is consistent with the law obtained from the mechanical theoretical analysis, which verifies that the modal perception analysis system for the cement concrete pavement structure provided in this embodiment is effective. long-term effectiveness of the method.

The preferred embodiments of the present invention have been described above in detail. It should be understood that those skilled in the art can make numerous modifications and changes according to the concept of the present invention without creative efforts. Therefore, all technical solutions that can be obtained by those skilled in the art through logical analysis, reasoning or limited experiments on the basis of the prior art according to the concept of the present invention shall fall within the protection scope determined by the claims.

Claims (10)

1. a cement concrete pavement structure modal perception analysis system, is characterized in that, comprises pavement structure body, optical fiber demodulator, modal analysis device and a plurality of pavement vibration perception devices connected successively, and described pavement vibration perception device adopts Distributed vibrating optical fiber units, all the distributed vibrating optical fiber units are embedded in the pavement structure body, each distributed vibrating optical fiber unit is provided with at least one measuring point, and each distributed vibrating optical fiber unit is connected with the The optical fiber demodulator and the modal analysis device are connected in sequence. 2. A cement concrete pavement structure modal perception analysis system according to claim 1, wherein the distributed vibration optical fiber unit is formed by a distributed vibration optical fiber wound in a ring, and two adjacent distributed vibration optical fiber units are formed. The vibrating optical fiber units are connected by optical fibers, and each of the distributed vibrating optical fiber units is sequentially connected to the optical fiber demodulator and the modal analysis device through optical fibers. 3. a kind of cement concrete pavement structure modal perception analysis system according to claim 2, it is characterised in that the number of winding turns of the distributed vibration optical fiber unit is related to the winding diameter and the pulse width of the optical fiber demodulator , the winding diameter of the distributed vibration optical fiber unit is related to the spacing between two adjacent distributed vibration optical fiber units and the desired modal spatial resolution; The formula describing the relationship between the number of winding turns of the distributed vibrating optical fiber unit and the winding diameter and the pulse width of the optical fiber demodulator is: nπd≥W In the formula, n is the winding number of the distributed vibration optical fiber unit, d is the winding diameter of the distributed vibration optical fiber unit, and W is the pulse width of the fiber demodulator; The formula describing the relationship between the winding diameter of the distributed vibration fiber unit, the spacing between two adjacent distributed vibration fiber units, and the desired modal spatial resolution is: d+s=L Among them, d is the winding diameter of the distributed vibration fiber unit, s is the distance between the outer diameters of two adjacent distributed vibration fiber units, and L is the desired modal spatial resolution. 4. a kind of cement concrete pavement structure modal perception analysis system according to claim 3, is characterized in that, the setting number of described distributed vibration optical fiber unit should satisfy: N(nπd+l ₀ )+l ₁ ≤W _max In the formula, N is the total number of distributed vibration optical fiber units for modal perception analysis of cement concrete pavement structure, _l0 is the total length of optical fibers connected between adjacent distributed vibration optical fiber units, _l1 is the connection fiber demodulator Compared with the length of the outgoing fiber of the distributed vibrating fiber unit, W _max is the maximum demodulation distance of the fiber demodulator. 5. A perceptual analysis method applying the cement concrete pavement structure modal perceptual analysis system according to any one of claims 1 to 4, characterized in that, comprising the following steps: S1: Obtain the vibration signals of all measuring points, and preprocess all the vibration signals; S2: Perform a pairwise combination of all the vibration signals preprocessed by S1, and perform power spectral density analysis. The power spectral density analysis includes the self-power spectral density analysis of the same measuring point and the cross-power spectral density analysis between different measuring points; S3: Calculate the normalized power spectral density of each measuring point at each frequency value according to the power spectral density obtained by S2, and combine the normalized power spectral density of each measuring point and each frequency to obtain the global power spectrum density; S4: Analyze the natural frequency of the pavement structure mode according to the global power spectral density obtained in S3; S5: According to the natural frequency obtained in S4, obtain the mode shape vector at the natural frequency, and then obtain the three-dimensional appearance field of the mode shape vector in the actual space; S6: Perform modal analysis on the pavement structure according to the natural frequency obtained in S5 and the three-dimensional appearance field of the mode shape vector obtained in S6 in the actual space. 6. The perceptual analysis method according to claim 5, wherein the formula describing the power spectral density analysis in S2 is:

In the formula, f is the sampling frequency, Δf is the unit bandwidth, T is the total duration of vibration acquisition, t is a certain moment during the acquisition period, x _i (t) is the vibration signal of measuring point i at time t, x _j (t ) represents the vibration signal of measuring point j at time t. When i=j, G _ij (f) is the self-power spectral density; when i≠j, G _ij (f) is the cross-power spectral density. 7. perceptual analysis method according to claim 6, is characterized in that, in S3, the formula describing the normalized power spectral density PSD _r (f _l ) of measuring point r at the lth discrete frequency f _l is:

In the formula, n _s is the total number of measurement points contained in the modal perception analysis system, f _l is the l-th discrete frequency in the analysis frequency band, and the total number of discrete frequencies is related to the total sampling time T and sampling frequency f, G _ir (f _l ) is the value of the cross power spectral density of the measuring point i and the measuring point r at f _l , and G _ij (f _l ) is the value of the cross power spectral density of the measuring point i and the measuring point j at f _l . 8. The perceptual analysis method according to claim 7, wherein the formula describing the global power spectral density in S3 is:

where PSD is the global power spectral density, f ₁ is the first discrete frequency, equal to 0Hz, and f _h is the last discrete frequency, equal to 0.5f, which is half the sampling frequency. 9. The perceptual analysis method according to claim 5, wherein the S4 comprises the following steps: S4.1: In the global power spectral density obtained in S3, for the global power spectral density of each measuring point, obtain the steady state diagram corresponding to the measuring point based on the curve fitting method; S4.2: Superimpose the steady-state graphs of each measuring point to obtain the empty-frequency fields of different steady-state points in the steady-state graph; S4.3: Project the result of the empty-frequency field of the steady-state point into the frequency domain, obtain the distribution of the steady-state point at different frequencies, and pick the peak value as the natural frequency. 10. The perceptual analysis method according to claim 5, wherein the S5 comprises the following steps: S5.1: Obtain the ratio of the power spectral density of each measuring point at the natural frequency obtained in S4, and then obtain the mode shape vector A at the natural frequency; S5.2: Determine the correspondence between each measuring point and the actual spatial position of the distributed vibrating fiber unit; S5.3: According to the number of measuring points in different rows and columns, map the mode shape vectors of all measuring points to their respective rows and columns; S5.4: Combine the elements in the mode shape vector of different rows and columns to form a three-dimensional appearance field of the mode shape vector in the actual space. The row and column correspond to the length and width of the real cement concrete panel respectively.

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