CN109991244A - Sleeve Grouted density detection device and method based on stress wave - Google Patents

Abstract

The present invention relates to a kind of sleeve Grouted density detection device and method based on stress wave, including the grout sleeve being embedded in upper prefabricated post to connect upper prefabricated post reinforcing bar and lower prefabricated post reinforcing bar in advance, the grout sleeve outer wall pastes two groups of piezoceramic transducers, two groups of piezoceramic transducers are laid in grout sleeve end and medium position respectively, every group of piezoceramic transducer quantity is two and is distributed in the opposite two sides of grout sleeve outer wall, piezoceramic transducer is connect by shielded wire with data collecting instrument, the data collecting instrument is connect with computer by shielded wire.It is at low cost the present invention is based on the sleeve Grouted density detection device principle of stress wave is simple, it is easy to operate, used piezoceramic transducer restricted by scene it is small, it is low to the environmental requirement of equipment, can be suitably used for the construction operation requirement at scene；It is not readily susceptible to the influence of site operation；Testing result accuracy is high.

Description

Device and method for measuring the compactness of sleeve grouting based on stress wave method

technical field

The invention relates to a device and method for detecting the compactness of sleeve grouting based on a stress wave method.

Background technique

The steel sleeve grouting connection technology is currently the most widely used in prefabricated buildings, and is mainly used in the connection of steel bars in component nodes. Rebar sleeve grouting connection joint is a combination of specially processed sleeve, matching grouting material and steel bar. When connecting steel bar, fast-hardening non-shrinking grouting material is injected, and the steel bar and sleeve are connected by the bonding and occlusal effect between materials. , Sleeve grouting joint has the advantages of reliable performance, wide applicability and easy installation. The connection strength of reinforced joints mainly depends on the fullness of the grouting material in the sleeve, but the blockage falls into the sleeve during the production or installation of the component, the holding time of the grouting machine during the grouting process is not sufficient, the plugging is not timely, and the bottom is level. The local grout leakage of the communicating cavity caused by the inaccurate joints and the backflow phenomenon of the grout in the sleeve after grouting may cause the grouting to be incomplete, thereby affecting the overall mechanical performance and seismic performance of the prefabricated building. At the same time, there is currently a lack of effective detection methods, and there is no sufficient basis for acceptance. We can only judge whether the grouting is full according to the smoothness of the grouting outlet hole of the grouting sleeve, thus laying a hidden danger for the safety of the structure. Therefore, a reasonable non-destructive testing method is urgently needed to determine the fullness of the sleeve grouting.

In recent years, structural health monitoring technology has been widely used in the construction industry. For the research on the fullness of sleeve grouting, X-ray industrial CT method, embedded wire drawing method and X-ray digital imaging method have been developed at home and abroad. . However, the X-ray industrial CT method is only suitable for pre-testing, and it has high requirements on the equipment environment and can only be carried out under shielded conditions in the laboratory; the embedded steel wire drawing method needs to be embedded in advance, and the embedded steel wire is easy to detect before testing Disturbed or damaged by the construction site; X-ray digital imaging method is only suitable for post-event detection, and only for sleeves in single-row arrangement and plum-shaped arrangement, and this method has radiation, and safety protection measures are required on site. Therefore, the existing detection methods have disadvantages such as high requirements on the equipment environment, high detection costs, and the detection results are easily disturbed by on-site construction.

SUMMARY OF THE INVENTION

In view of this, the purpose of the present invention is to provide a sleeve grouting compactness detection device based on the stress wave method with low cost, little interference from on-site construction, and high accuracy.

The present invention adopts the following scheme to realize: a sleeve grouting compactness detection device based on a stress wave method, comprising a grouting sleeve pre-buried in an upper prefabricated column to connect the upper prefabricated column steel bar and the lower prefabricated column steel bar, the grouting sleeve Two sets of piezoelectric ceramic sensors are attached to the outer wall of the sleeve. The two sets of piezoelectric ceramic sensors are respectively arranged at the end and the middle of the grouting sleeve. The number of each group of piezoelectric ceramic sensors is two and distributed on the opposite sides of the outer wall of the grouting sleeve. , the piezoelectric ceramic sensor is connected with the data acquisition instrument through a shielded wire, and the data acquisition instrument and the computer are connected with the shielded wire.

Further, the piezoelectric ceramic sensor includes a piezoelectric ceramic sheet encapsulated in epoxy resin, the shielded wire connected to the piezoelectric ceramic sensor is a single two-core structure, and the two cores penetrate the epoxy resin and are welded respectively. On both sides of the piezoelectric ceramic sheet, wax layers are coated on both sides of the piezoelectric ceramic sheet.

Another technical solution of the present invention: a method for detecting the compactness of sleeve grouting based on the stress wave method, using the above-mentioned device for detecting the compactness of sleeve grouting based on the stress wave method, and controlling the piezoelectric ceramics through the LabView software on the computer The sensor generates high-frequency stress waves, and collects stress wave signals. The collected signals are first denoised by the default threshold of wavelet packets, and then time domain analysis and frequency domain analysis are performed. In the time domain analysis, the energy signal is established by the wavelet packet energy method. The relationship with the grouting compactness, by comparing the difference in the energy value of the wavelet packet to determine whether the grouting sleeve is compact; the frequency domain analysis is to obtain the frequency domain signal by Fourier transform of the signal collected in the time domain analysis, and then The relationship between the frequency domain signal change and the grouting density was established, and the grouting density of the sleeve was evaluated by comparing the characteristic parameters on the frequency domain signal.

Compared with the prior art, the present invention has the following beneficial effects: the sleeve grouting compactness detection device based on the stress wave method of the present invention is simple in principle, low in cost, convenient in operation, and the piezoelectric ceramic sensor used is less restricted by the site, The environmental requirements for the equipment are low, and it can be applied to the on-site construction operation requirements; it will not cause misjudgment due to the hardening of the residual slurry on the core components of the sensor after the grouting material is returned to the grouting; it is not easily affected by on-site construction; the test results High accuracy.

In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below through specific embodiments and related drawings.

Description of drawings

Fig. 1 is the installation schematic diagram of the grouting sleeve in the embodiment of the present invention;

2 is a schematic diagram of the installation of the packaged piezoelectric ceramic sensor on the grouting sleeve according to the embodiment of the present invention;

3 is a schematic diagram of a package structure of a piezoelectric ceramic sheet in an embodiment of the present invention;

FIG. 4 is a schematic diagram of welding a piezoelectric ceramic sheet and a shielded wire in an embodiment of the present invention;

Fig. 5 is the working principle diagram of the embodiment of the present invention;

Fig. 6 is the detection flow chart of the embodiment of the present invention;

Fig. 7 is the original signal data of the end of the grouting sleeve with the compactness of 100% according to the embodiment of the present invention;

Fig. 8 is the original signal data of the middle of the grouting sleeve with the density of 100% according to the embodiment of the present invention;

Fig. 9 is the original signal data of the grouting sleeve end with the density of 50% according to the embodiment of the present invention;

Fig. 10 is the original signal data of the middle of the grouting sleeve with the density of 50% according to the embodiment of the present invention;

Fig. 11 is the frequency domain signal data of the end of the grouting sleeve with the density of 100% according to the embodiment of the present invention;

Fig. 12 is the frequency domain signal data of the middle part of the grouting sleeve with the density of 100% according to the embodiment of the present invention;

Fig. 13 is the frequency domain signal data of the end of the grouting sleeve with the density of 50% according to the embodiment of the present invention;

Fig. 14 is the frequency domain signal data of the middle part of the grouting sleeve with the density of 50% according to the embodiment of the present invention;

Description of the numbers in the figure: 100-upper prefabricated column, 110-upper prefabricated column reinforcement, 200-lower prefabricated column, 210-lower prefabricated column reinforcement, 300-grouting sleeve, 400-piezoelectric ceramic sensor, 410-shielded wire, 420 - Wax layer, 430- Piezoelectric ceramic sheet, 500- Data acquisition instrument, 600- Computer, 700- Epoxy resin.

Detailed ways

As shown in FIGS. 1-6 , a device for detecting the compactness of sleeve grouting based on the stress wave method includes a grouting sleeve embedded in the upper prefabricated column 100 to connect the upper prefabricated column steel bar 110 and the lower prefabricated column steel bar 210 300, two sets of piezoelectric ceramic sensors are pasted on the outer wall of the grouting sleeve 300, the two sets of piezoelectric ceramic sensors are respectively arranged at the end and the middle of the grouting sleeve, and the number of each set of piezoelectric ceramic sensors is two and distributed in the grouting sleeve. On the opposite sides of the outer wall of the cylinder 300, the piezoelectric ceramic sensor is connected to the data acquisition instrument through a shielded wire 410, the data acquisition instrument 500 and the computer 600 are connected through a shielded wire, and the two shielded wires are RVV type shielded wires, which can effectively reduce The effect of the noise signal in the acquired signal. One of the two piezoelectric ceramic sensors in the same group is used as a receiving end, and the other is used as a reflecting end to be connected to the data acquisition instrument 500 respectively. Staggered by 90°.

The detection principle of the sleeve grouting compactness detection device based on the stress wave method:

(1) Obtain the piezoelectric signal by pasting the piezoelectric ceramic sensor on the outer surface of the grouting sleeve and establish the relationship between the piezoelectric signal and the grouting density of the sleeve;

(2) The positions of the grouting material in the grouting sleeve at the end and the middle of the sleeve are often different, and piezoelectric ceramic sensors need to be placed at the end and the middle;

(3) Use the wavelet packet default threshold denoising method to denoise the signal collected by the data acquisition instrument, so as to extract the signal characteristic parameters with high sensitivity;

(4) Using time-domain analysis and frequency-domain analysis methods, an index for judging grouting compactness is proposed.

The data acquisition instrument 500 adopts the NI USB-6363 data acquisition instrument of NI Company, and writes the program through the LabView software on the computer to control and collect the signal. , in order to reduce the interference of the noise signal to the target signal, considering that the noise frequency is mainly concentrated in the low frequency range, the frequency of the sampling signal is 10kHz~200kHz; the collected signal is first de-noised by the default threshold of the wavelet packet, which is provided by the MATLAB program. The function of the grouting is denoised, and then the time domain analysis and frequency domain analysis are carried out. In the time domain analysis, the wavelet packet energy method is used to establish the relationship between the energy signal and the grouting density. The frequency domain analysis is to analyze the signal collected in the time domain analysis. After Fourier transform, the frequency domain signal map is obtained, and then the relationship between the frequency domain signal change and the grouting density is established.

The time domain analysis adopts the wavelet packet energy method, assuming that X is the structural dynamic response signal measured by the piezoelectric ceramic sheet as a sensor in the process of structural health monitoring. 2 ⁿ sub-signals of the frequency band, the original signal X can be expressed as the following relation:

(1)

X _j can be expressed as: (2)

In formula (2), j is the node number of the i-th layer in the wavelet packet decomposition tree structure, and m is the number of data points used. After X is decomposed by the i-layer wavelet packet, the corresponding sub-band signal energy of node [i,j] is (3)

From formula (3), the wavelet packet energy spectrum eigenvector E _i can be obtained when the original signal is decomposed at the i-th layer.

(4)

The total energy of each sub-signal is (6)

The energy value of the decomposed wavelet packet is equivalent to the energy value of the original signal. By comparing the difference of the energy value of the wavelet packet, it is judged whether the casing grouting is dense, so as to detect the damage of the casing.

For the time-domain signal collected by the data acquisition instrument 500, perform fast Fourier transform, convert it into a frequency-domain signal, and compare the characteristic parameter Y on the frequency-domain signal to evaluate the compactness of the sleeve grouting, so as to achieve the purpose of detection. The characteristic parameter Y can be expressed as the following relation: (6)

In this embodiment, the piezoelectric ceramic sensor includes a piezoelectric ceramic sheet 400 encapsulated in an epoxy resin 700, the shielded wire connected to the piezoelectric ceramic sensor is a single two-core structure, and the two cores are inserted into the ring Oxygen resin 700 is welded on both sides of the piezoelectric ceramic sheet 400 respectively. The welding time should not be too long, and the welding point should be small and flat to avoid the piezoelectric ceramic sheet losing piezoelectric performance due to the temperature exceeding the Curie temperature point of the piezoelectric ceramic sheet. The two sides of the piezoelectric ceramic sheet 400 are coated with a wax layer 420 to prevent the epoxy resin from being hardened and the piezoelectric ceramic sheet to be damaged; the piezoelectric ceramic sheet is specifically selected from lead zirconate titanate piezoelectric ceramics, and PZT- Type 4 piezoelectric ceramic sheet has both transmitting and receiving functions, and has a wide signal range and strong adaptability; the electric ceramic sensor is pasted on the grouting sleeve with epoxy resin AB glue, and the grouting sleeve is used for pasting The parts of the piezoelectric ceramic sheet 400 are polished with a sander until smooth, and then cleaned with alcohol.

The production process of the packaging structure is as follows: first, a frame-shaped mold is surrounded by cardboard, one of the side walls of the mold is provided with a through hole for the shielded wire to pass through, and the inner wall of the mold is pasted with transparent glue, which can make demolding easier; The inner wall is brushed with a layer of epoxy resin mold release agent; then the shielded wire is inserted into the mold through the through hole, and the two cores of the shielded wire are welded to the two sides of the piezoelectric ceramic sheet respectively, and then the two sides of the piezoelectric ceramic sheet are The wax layer 420 is coated, and then epoxy resin is poured into the mold to embed the piezoelectric ceramic sheet in the poured epoxy resin. The epoxy resin adopts epoxy resin AB glue with a ratio of 1:1. After hardening, the mold is removed and sanded.

Piezoelectric Ceramics (PZT for short): It is an information functional ceramic material that can convert mechanical energy and electrical energy to each other - piezoelectric effect. In addition to piezoelectricity, piezoelectric ceramics also have dielectric properties and elasticity. Piezoelectric ceramics are made by using the material under the action of mechanical stress to cause the relative displacement of the internal positive and negative charge centers to cause polarization, resulting in the appearance of bound charges with opposite signs on the surfaces of the two ends of the material, that is, the piezoelectric effect, and has sensitive characteristics.

Stress Waves: Stress waves are propagating forms of stress and strain disturbances. Mechanical disturbances in deformable solid media are manifested as changes in particle velocity and corresponding changes in stress and strain states. When the relationship between stress and strain is linear, elastic waves propagate in the medium; when there is a nonlinear relationship, there are plastic waves and shock waves.

In order to check the validity and accuracy of the grouting density detection by the sleeve grouting density detection device based on the stress wave method of the present invention, the actual measured data is now used for analysis. As shown in Figures 7-10, it is the raw signal data at the end and the middle of the grouting sleeve specimen with 100% and 50% grouting density.

The original signal is denoised and then analyzed in time domain.

Table 1 shows that the signal measured by the grouting sleeve specimen with 50% grouting density is about 2.24 times that of 100% density, indicating that this indicator is feasible.

The denoised signal is analyzed in the frequency domain and the fast Fourier transform is used, and the results are shown in Figures 11-14. The results obtained through relational formula (6) are shown in Table 2.

Table 2 shows that the signal measured by the grouting sleeve specimen with 50% grouting density is about 1.3 times that of 100% grouting, which also shows that this indicator can be applied to the requirements of sleeve grouting density detection.

A method for detecting the compactness of sleeve grouting based on the stress wave method, adopts the above-mentioned device for detecting the compactness of sleeve grouting based on the stress wave method, and controls a piezoelectric ceramic sensor to generate a high-frequency stress wave through LabView software on a computer, The stress wave signal is collected. The excitation signal adopts a sine frequency sweep signal with a voltage amplitude of 10V and a period of 1s. In order to reduce the interference of the noise signal to the target signal, considering that the noise frequency is mainly concentrated in the low frequency range, the frequency of the sampling signal is 10kHz. ~200kHz; first perform wavelet packet default threshold denoising on the collected signal, first perform wavelet packet default threshold denoising on the collected signal, and use the function that comes with the MATLAB program to denoise, and then perform time domain analysis and frequency domain analysis. Analysis, in the time domain analysis, the wavelet packet energy method is used to establish the relationship between the energy signal and the grouting compactness, and by comparing the difference in the wavelet packet energy value to determine whether the grouting sleeve is dense or not; the frequency domain analysis is the time domain analysis. The collected signal is subjected to Fourier transform to obtain the frequency domain signal, and then the relationship between the frequency domain signal change and the grouting density is established, and the grouting density of the sleeve is evaluated by comparing the characteristic parameters on the frequency domain signal.

The detection method of the invention has the following advantages: the detection principle is simple, the operation is convenient, and compared with the X-ray industrial CT method and the X-ray digital imaging method, the piezoelectric ceramic sheet used is less restricted by the site, and the externally attached piezoelectric ceramic is used. The chip as a sensor will not cause misjudgment due to the hardening of the residual slurry on the core element of the sensor after the grout is returned to the grout; compared with the embedded wire drawing method, the packaged piezoelectric sensor is not easily affected by on-site construction.

Compared with the existing method, the present invention intends to adopt the piezoelectric ceramic sheet technology, and the method for detecting the compactness of the grouting sleeve based on the principle of the stress wave method is simpler, more economical and more accurate, and this detection method can achieve the following objectives: (1 ) The damage index adopted has high sensitivity, which can provide more accurate data for the further study of the piezoelectric signal law of the grouting compactness of the grouting sleeve; (2) The environmental requirements of the equipment are low, and it can be applied to the construction work requirements on site; ( 3) The theory is simple and the algorithm is easy to implement.

Unless otherwise stated in any of the technical solutions disclosed in the present invention, if it discloses a numerical range, then the disclosed numerical range is a preferred numerical range, and any person skilled in the art should understand that: the preferred numerical range is only Among the many implementable numerical values, the technical effect is relatively obvious or representative. Since the numerical values are too numerous to be exhaustive, only some numerical values are disclosed in the present invention to illustrate the technical solutions of the present invention, and the above-mentioned numerical values shall not constitute a limitation on the protection scope of the present invention.

If the present invention discloses or involves parts or structures that are fixedly connected to each other, then, unless otherwise stated, fixed connection can be understood as: detachable fixed connection (for example, using bolts or screws), can also be understood as: Non-removable fixed connections (such as riveting, welding), of course, mutual fixed connections can also be replaced by a one-piece structure (for example, integrally formed using a casting process) (except that it is obviously impossible to use a one-piece forming process).

In addition, unless otherwise stated, the terms used in any of the technical solutions disclosed in the present disclosure used to represent positional relationships or shapes include states or shapes that are similar to, similar to, or close to.

Any component provided by the present invention may be assembled from a plurality of individual components, or may be a single component manufactured by an integral molding process.

Finally it should be noted that: the above embodiment is only used to illustrate the technical scheme of the present invention and not to limit it; Although the present invention has been described in detail with reference to the preferred embodiment, those of ordinary skill in the art should understand: The specific embodiments of the invention are modified or some technical features are equivalently replaced; without departing from the spirit of the technical solutions of the present invention, all of them should be included in the scope of the technical solutions claimed in the present invention.

Claims (3)

1. a sleeve grouting compactness detection device based on stress wave method is characterized in that: comprise the grouting sleeve embedded in the upper prefabricated column in order to connect the upper prefabricated column steel bar and the lower prefabricated column steel bar, the grouting sleeve Two sets of piezoelectric ceramic sensors are attached to the outer wall of the cylinder. The two sets of piezoelectric ceramic sensors are respectively arranged at the end and the middle of the grouting sleeve. The number of each group of piezoelectric ceramic sensors is two and distributed on the opposite sides of the outer wall of the grouting sleeve. The piezoelectric ceramic sensor is connected with the data acquisition instrument through a shielded wire, and the data acquisition instrument and the computer are connected with the shielded wire. 2. The device for detecting the compactness of sleeve grouting based on the stress wave method according to claim 1, wherein the piezoelectric ceramic sensor comprises a piezoelectric ceramic sheet encapsulated in epoxy resin, and the piezoelectric ceramic sensor The connected shielded wires are of a single two-core structure, and the two cores are inserted into epoxy resin and welded to both sides of the piezoelectric ceramic sheet, and the two sides of the piezoelectric ceramic sheet are coated with wax layers. 3. a sleeve grouting compactness detection method based on stress wave method, adopts the sleeve grouting compactness detection device based on stress wave method as claimed in claim 1, it is characterized in that: control the pressure by the LabView software on the computer. The electrical ceramic sensor generates high-frequency stress waves, and collects stress wave signals. The collected signals are first denoised by the default threshold of the wavelet packet, and then the time domain analysis and frequency domain analysis are carried out. In the time domain analysis, the wavelet packet energy method is used to establish The relationship between the energy signal and the grouting density is determined by comparing the difference in the energy value of the wavelet packet to determine whether the grouting sleeve is dense or not. , and then establish the relationship between the frequency domain signal change and the grouting compactness, and compare the characteristic parameters on the frequency domain signal to evaluate the compactness of the sleeve grouting.