CN210037714U - Sleeve grouting compactness detection device based on stress wave method - Google Patents

Abstract

The utility model relates to a sleeve grouting compactness detection device based on a stress wave method. Two groups of piezoelectric ceramic sensors are pasted. The two groups 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 ceramic sensor is connected with the data acquisition instrument through shielded wires, and the data acquisition instrument and the computer are connected with the shielded wire. The utility model based on the stress wave method has the advantages of simple principle, low cost and convenient operation. The piezoelectric ceramic sensor used is less restricted by the site, has low requirements on the environment of the equipment, and is suitable for on-site construction. Operation requirements; not easily affected by on-site construction; high accuracy of test results.

Description

Sleeve grouting compactness detection device based on stress wave method

technical field

The utility model relates to a sleeve grouting compactness detection device 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 the grouting is completed may cause the grouting to be not full, 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. It can only be determined 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.

Utility model content

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

The utility model adopts the following scheme to realize: a sleeve grouting compactness detection device based on a stress wave method, comprising a grouting sleeve embedded in an upper prefabricated column for connecting the steel bars of the upper prefabricated column and the steel bars of the lower prefabricated column. Two sets of piezoelectric ceramic sensors are pasted on the outer wall of the grouting sleeve, and the two sets of piezoelectric ceramic sensors are respectively arranged at the end and the middle of the grouting sleeve. On the other hand, the piezoelectric ceramic sensor is connected with the data acquisition instrument through shielded wires, 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.

Compared with the prior art, the utility model has the following beneficial effects: the device for detecting the compactness of the sleeve grouting based on the stress wave method is simple in principle, low in cost and convenient in operation, and the piezoelectric ceramic sheets used are restricted by the site. Small, low environmental requirements for equipment, suitable for on-site construction work requirements; no misjudgment may be caused by 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 detection results are highly accurate.

In order to make the purpose, technical solutions and advantages of the present utility model more clearly understood, the present utility model 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 utility model;

2 is a schematic diagram of the installation of a packaged and molded piezoelectric ceramic sensor on a grouting sleeve in an 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;

4 is a schematic diagram of welding of piezoelectric ceramic sheets and shielded wires 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 utility model;

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

Fig. 8 is the original signal data of the middle part 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 part 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 grouting sleeve end 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;

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;

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

Description of the labels 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 sheet, 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 groups of piezoelectric ceramic sensors are pasted on the outer wall of the grouting sleeve 300, and each group of piezoelectric ceramic sensors is two in number and distributed on opposite sides of the outer wall of the grouting sleeve 300. The acquisition instrument is connected. The data acquisition instrument 500 and the computer 600 are connected by shielded wires, both of which are RVV type shielded wires, which can effectively reduce the influence of noise signals in the acquisition 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 controls the piezoelectric ceramic sensor to generate high-frequency stress wave through the LabView software on the computer, and collects the stress wave signal. The selected excitation signal adopts the sine frequency sweep signal. The voltage amplitude is 10V and the period is 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. Noise, denoising through the function that comes with the MATLAB program, and then perform time domain analysis and frequency domain analysis. In the time domain analysis, the wavelet packet energy method is used to establish the relationship between the energy signal and the grouting density, and the frequency domain analysis is the time domain analysis. The signal collected in the domain analysis is subjected to Fourier transform to obtain the spectrogram, and then the relationship between the signal spectrum 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）

(1)

（2）X _j can be expressed as:

(2)

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

（4）

(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, and the shielded wire connected to the piezoelectric ceramic sensor is a single two-core structure, and the two cores are respectively penetrated The epoxy resin 700 is welded to the two 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, so as to avoid the piezoelectric ceramic sheet losing its piezoelectricity due to the temperature exceeding the Curie temperature point of the piezoelectric ceramic sheet. performance; both sides of the piezoelectric ceramic sheet 400 are coated with wax layers 420 to prevent the epoxy resin from hardening and destroying the piezoelectric ceramic sheet; the piezoelectric ceramic sheet is specifically selected from lead zirconate titanate piezoelectric ceramics, and PZT is selected. -4 type piezoelectric ceramic sheet has both the functions of transmitting and receiving, 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 The part where the piezoelectric ceramic sheet 400 is attached is 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 demoulding easier; The inner wall of the mold is brushed with a layer of epoxy resin mold release agent, and then the shielded wire is inserted into the mold through the through hole. The wax layer 420 is coated on the side, and then epoxy resin is poured into the mold to bury the piezoelectric ceramic sheet in the poured epoxy resin. The epoxy resin adopts epoxy resin AB glue with a ratio of 1:1. After the resin has hardened, 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 data of the end and middle of the grouting sleeve specimens 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.

Using the sleeve grouting compactness detection device based on the stress wave method of the present utility model for compactness detection 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 used piezoelectric The ceramic sheet is less restricted by the site, and the use of the externally attached piezoelectric ceramic sheet as the 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 pre-embedded steel wire drawing method , the use of packaged piezoelectric sensors is not easily affected by on-site construction.

Compared with the existing method, the present utility model intends to use 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 accurate, and this method can achieve the following objectives: ( 1) The adopted damage index 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 above-mentioned utility model, if it discloses a numerical range, then the disclosed numerical range is the preferred numerical range, and any person skilled in the art should understand: the preferred numerical range is only It is a numerical value with obvious or representative technical effect among many practicable numerical values. 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 structural parts 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 connection (such as riveting, welding), of course, the mutual fixed connection can also be replaced by a one-piece structure (for example, using a casting process to integrally form) (except that it is obviously impossible to use an integral forming process).

In addition, the terms used to represent the positional relationship or shape used in any of the technical solutions disclosed in the present invention, unless otherwise stated, have their meanings including 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: still The specific embodiments of the present invention can be modified or some technical features can be 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 (2)

1. The utility model provides a closely knit degree detection device of sleeve grout based on stress wave method which characterized in that: including pre-burying in last prefabricated post in be used for connecting the grout sleeve of prefabricated post reinforcing bar and prefabricated post reinforcing bar down, grout sleeve outer wall pastes two sets of piezoceramics sensors, and two sets of piezoceramics sensors are laid respectively at grout sleeve end and middle part position, and every group piezoceramics sensor quantity is two and distributes in the relative both sides of grout sleeve outer wall, and piezoceramics sensor passes through the shielded wire and is connected with the data acquisition appearance, the data acquisition appearance passes through the shielded wire with the computer and is connected.

2. The stress wave method-based sleeve grouting compactness detection device according to claim 1, characterized in that: the piezoelectric ceramic sensor comprises a piezoelectric ceramic piece packaged in epoxy resin, a shielding wire connected with the piezoelectric ceramic sensor is of a single two-core structure, two wire cores penetrate into the epoxy resin and are respectively welded on two side faces of the piezoelectric ceramic piece, and two side faces of the piezoelectric ceramic piece are coated with a wax layer.

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