Disclosure of Invention
The technical problem to be solved by the invention is to overcome the defect of the prior art that a method for rapidly and accurately detecting the vertical prestress of the prestressed concrete structure is lacking, and the reliability of the prestressed concrete structure is limited, so that the device and the method for detecting the prestressed structure based on the piezoelectric fluctuation method are provided.
The prestress structure detection device based on the piezoelectric fluctuation method comprises a plurality of groups of stress wave drivers and stress wave sensors which are correspondingly arranged, prestress ribs are arranged in a component, the end parts of the prestress ribs extend out, polygonal nuts are arranged at the end parts of the prestress ribs in a threaded fit mode with the prestress ribs, a base plate is fixed on the surface of the component, one stress wave driver is fixedly arranged on each surface of the polygonal nuts, a plurality of stress wave sensors are fixedly arranged on the outer surface of the base plate in a one-to-one correspondence to the stress wave sensors, and the stress wave sensors are arranged in the direction facing the surface of the polygonal nut where the corresponding stress wave driver is located.
Further, the device also comprises a collector which is respectively connected with the stress wave driver and the stress wave sensor and is used for sending an excitation signal to the stress wave driver and acquiring a feedback signal from the stress wave sensor.
Further, the device also comprises a signal amplifier, wherein the signal amplifier is respectively connected with the acquisition instrument and the stress wave driver and is used for amplifying the excitation signal.
A prestress structure detection method based on a piezoelectric fluctuation method comprises the following steps:
step S1, the stress wave driver sends stress waves;
step S2, the stress wave sensor receives stress waves and outputs feedback signals;
and S3, analyzing the feedback signal to obtain the prestress loss degree of the prestress structure.
Further, the step S3 includes:
S3.1, carrying out wavelet packet energy analysis on the feedback signal to obtain an average wavelet packet energy value;
s3.2, calculating a damage index according to the average wavelet packet energy value;
And S3.3, substituting the damage index into a preset theoretical model to obtain the prestress loss rate.
Further, in the step S3.1, the average wavelet packet energy value is an average value of energy values obtained by performing wavelet packet energy analysis on feedback signals obtained by the stress wave driver and the stress wave sensor of each group.
Further, in the step S3.2, the method for calculating the damage index is as follows:
Wherein F DI is a damage index, the value range is (0-1), E l is the average wavelet packet energy value when the effective prestress is lost, and E f is the average wavelet packet energy value when the effective prestress is in a full load state.
Further, in the step S3.3, the theoretical model is:
wherein x is the damage index of wavelet packet energy collected by different prestressing force, y is the loss rate of prestressing force, a, b and c are undetermined coefficients, and the values of the coefficients are required to be determined according to historical experimental data;
The calculation formula of the prestress loss rate is as follows:
Wherein ρ is an effective prestress loss rate, the value range is (0-1), F max is an effective prestress (kN) at full load, and F i is an effective prestress (kN) after loss.
Further, the method also comprises the following steps:
s4, carrying out wavelet packet energy analysis according to feedback signals obtained by each group of stress wave drivers and stress wave sensors to obtain wavelet packet energy values of each group;
Setting a lower threshold and an upper threshold of the wavelet packet energy value according to the average wavelet packet energy value;
and judging the inclination condition of the nut according to the lower limit threshold value and the upper limit threshold value.
The prestress structure has the beneficial effects that the stress wave driver and the stress wave sensor are arranged on the polygonal nut and the backing plate of the prestress structure, the stress wave driver transmits stress waves, the stress waves are transmitted inside the prestress structure, and then feedback signals are received through the stress wave sensor, so that the prestress loss condition inside the prestress structure is calculated and analyzed. The detection structure and the method disclosed by the invention can rapidly and accurately obtain the prestress loss condition in the prestress structure, so that the internal prestress of the prestress structure can be kept in a reasonable range, and the prestress failure is avoided.
Detailed Description
In order that the above objects, features and advantages of the application will be readily understood, a more particular description of the application will be rendered by reference to the appended drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application. The present application may be embodied in many other forms than described herein and similarly modified by those skilled in the art without departing from the spirit of the application, whereby the application is not limited to the specific embodiments disclosed below.
Embodiment one:
Referring to fig. 1 and 2, the embodiment discloses a prestress structure detection device based on a piezoelectric fluctuation method, which comprises a plurality of groups of stress wave drivers 11 and stress wave sensors 12 which are correspondingly arranged, wherein a prestress rib 3 is arranged in a member 2, the end part of the prestress rib 3 extends out, a polygonal nut 4 is in threaded fit with the prestress rib 3 and is arranged at the end part of the prestress rib 3, a backing plate 5 is fixed on the surface of the member 2, each surface of the polygonal nut 4 is fixedly provided with one stress wave driver 11, the outer surface of the backing plate 5 is fixedly provided with a plurality of stress wave sensors 12 corresponding to the stress wave sensors 12 one by one, and the stress wave sensors 12 are arranged in the direction facing the surface of the polygonal nut 4 where the corresponding stress wave drivers 11 are arranged.
Referring to fig. 3, the device further comprises a collector 6, wherein the collector 6 is respectively connected with the stress wave driver 11 and the stress wave sensor 12, and is used for sending an excitation signal to the stress wave driver 11 and acquiring a feedback signal from the stress wave sensor 12. And the device also comprises a signal amplifier 7, wherein the signal amplifier 7 is respectively connected with the acquisition instrument 6 and the stress wave driver 11 and is used for amplifying the excitation signal.
Specifically, in this embodiment, the member 2 is concrete, the tendon 3 is a prestressed reinforcement, and the pad 5 is a metal pad. In this embodiment, the stress wave driver 11 is a piezoelectric ceramic driver, the stress wave sensor 12 is a piezoelectric ceramic sensor, and the piezoelectric ceramic driver and the piezoelectric ceramic sensor are made by welding shield wires on the positive and negative electrodes of a piezoelectric ceramic sheet, respectively. As a preferable mode of the embodiment, the piezoelectric ceramic piece is PZT-5, the positive electrode and the negative electrode are positioned on the same side, the size is 15 multiplied by 5 multiplied by 2mm, the width of the negative electrode is 5mm, the width of the positive electrode is 8mm, the interval between the positive electrode and the negative electrode is 2mm, and the insulating shells at two ends of the shielding wire are stripped by wire stripper to expose a wire with the length of 1 cm.
Before the stress wave driver 11 and the stress wave sensor 12 are fixed, the polygonal nut 4 and the backing plate 5 are subjected to rust removal treatment, wherein the rust removal treatment comprises spraying a special rust remover on the surfaces of the polygonal nut 4 and the backing plate 5, wiping, polishing the surface to be measured, keeping the surface to be measured as flat as possible, and then cleaning with medical alcohol. When the stress wave driver 11 and the stress wave sensor 12 are fixed, a layer of epoxy resin glue is smeared on the surface of a point to be measured, the surface is smeared with 502 strong glue for insulation treatment, finally, the manufactured piezoelectric ceramic plate is stuck on the surface and pressed for 3 minutes to be loosened after the glue is solidified, and after the stress wave driver 11 and the stress wave sensor 12 are stuck, a universal meter is used for checking whether the path is available or not, so that whether the sticking is successful or not is checked.
In this embodiment, the polygonal nut 4 is a hexagonal nut, the hexagonal nut has an equilateral hexagon shape, the stress wave drivers 11 are provided with six stress wave drivers 11, the six stress wave drivers 11 are respectively fixed at the centers of six sides of the hexagonal nut, and the six stress wave sensors 12 are fixed at the positions, close to the corresponding stress wave drivers 11, of the upper side of the backing plate 5.
Preferably, the collector 6 is preferably a NIUSB-6361, and the signal amplifier 7 is preferably a high-frequency power amplifier of model number of core-of-natural E2022. The NIUSB-6361 collector 6 is provided with 16 channel ports, the acquisition program is compiled by combining with LabView in the embodiment to realize the visualization of signal acquisition, the excitation signal is a pulse signal excited by the LabView program, the amplitude range is-10V-10V, the signal amplifier 7 amplifies the excitation signal by 30 times and then applies the excitation signal to the prestress driver, finally the prestress sensor receives the signal, the NIUSB-6361 collector 6 is used as the equipment for signal acquisition, the NIUSB-6361 collector 6 and the notebook computer are connected through a USB data line, the detected data is stored in the computer in real time, and the computer realizes calculation and analysis.
Embodiment two:
The embodiment discloses a method for detecting a prestress structure based on a piezoelectric fluctuation method, which is provided by the embodiment 1, and comprises the following steps:
Step S1, the stress wave driver 11 transmits stress waves;
step S2, the stress wave sensor receives stress waves and outputs feedback signals;
and S3, analyzing the feedback signal to obtain the prestress loss degree of the prestress structure.
The step S3 includes:
S3.1, carrying out wavelet packet energy analysis on the feedback signal to obtain an average wavelet packet energy value;
s3.2, calculating a damage index according to the average wavelet packet energy value;
And S3.3, substituting the damage index into a preset theoretical model to obtain the prestress loss rate.
In this embodiment, the calculation method of wavelet packet energy analysis includes that the collected feedback signals are subjected to wavelet packet decomposition to form sub-signals of different frequency bands, and energy of sub-frequency bands of each sub-signal is calculated and summed to be a wavelet packet energy value.
In the step S3.1, the average wavelet packet energy value is an average value of energy values obtained by performing wavelet packet energy analysis on the feedback signals obtained by the stress wave driver 11 and the stress wave sensor 12 of each group.
The method also comprises the following steps:
s4, carrying out wavelet packet energy analysis according to feedback signals obtained by each group of stress wave drivers 11 and stress wave sensors 12 to obtain wavelet packet energy values of each group;
Setting a lower threshold and an upper threshold of the wavelet packet energy value according to the average wavelet packet energy value;
and judging the inclination condition of the nut according to the lower limit threshold value and the upper limit threshold value.
In the step S3.2, the method for calculating the damage index includes:
Wherein F DI is a damage index, the value range is (0-1), E l is the average wavelet packet energy value when the effective prestress is lost, and E f is the average wavelet packet energy value when the effective prestress is in a full load state. The damage index F DI of the wavelet packet energy can effectively characterize the damage degree of the prestress, preliminarily judge the loss degree of the effective prestress, and the full-load state of the prestress is set according to different detection conditions.
In this embodiment, the average wavelet packet energy value when the effective prestressing force of E f is in the full load state is a predicted calculation value, six groups of stress wave drivers 11 and stress wave sensors 12 are installed in advance in a system without prestressing loss, and the average value of the corresponding wavelet packet energy values is measured and is the average wavelet packet energy value in the full load state.
In the step S3.3, the theoretical model is:
The values of the coefficients are determined according to historical experimental data, and in the embodiment, the values a= -92.41, b=0.07 and c= 93.93 of the coefficients are measured and calculated according to the historical experimental data;
the theoretical model can be effectively fit to the relation between the damage index of wavelet packet energy and the loss rate of prestress, and in other embodiments of the invention, the theoretical model can be formed by fitting other expressions.
The calculation formula of the prestress loss rate is as follows:
Wherein ρ is an effective prestress loss rate, the value range is (0-1), F max is an effective prestress (kN) at full load, and F i is an effective prestress (kN) after loss. In this embodiment Fmax is the effective pre-stress when it is set to full load according to the design value of the pre-stress.
In this embodiment, the method for constructing the theoretical model includes:
Taking 600kN as the full-load state of the prestress, regarding the prestress under the other working conditions as the effective prestress after prestress loss, dividing the prestress into 7 groups of working conditions which are respectively 0kN, 25kN, 50kN, 100kN, 200kN, 400kN and 600kN, carrying out repeated tests for three times, carrying out complete replacement of the prestress rib 3, the polygonal nut 4 and the backing plate 5 before each test, obtaining the damage index of the wavelet energy and the damage index of the average value of the wavelet energy through historical experiments, and calculating the effective prestress loss rate under different working conditions.
By nonlinear fitting analysis of the damage index F DI and the prestress damage rate rho, a fitting curve of three tests and an average of the three tests is obtained:
Wherein x is the damage index of wavelet packet energy collected by different prestressing force, y is the loss rate of the prestressing force;
substituting the loss index obtained by the signals acquired by the test into a fitting curve, wherein the relative error is within +/-15%, so that the accuracy of the fitting result is feasible, the requirements of actual engineering are met, and finally, the fitting curve with average three tests is selected as a theoretical model of the final damage index-prestress loss rate.
In this embodiment, the method further includes the steps of:
s4, carrying out wavelet packet energy analysis according to feedback signals obtained by each group of stress wave drivers 11 and stress wave sensors 12 to obtain wavelet packet energy values of each group;
Setting a lower threshold and an upper threshold of the wavelet packet energy value according to the average wavelet packet energy value;
And judging the inclination condition of the polygonal nut 4 according to the lower limit threshold value and the upper limit threshold value.
Specifically, the feedback signals obtained by the stress wave driver 11 and the stress wave sensor 12 in six groups are set for wavelet packet energy analysis to obtain wavelet packet energy values of each group as X1, X2, X3, X4, X5 and X6 respectively, wherein the average wavelet packet energy value isAnd the lower limit threshold of X is set to be 95%The upper threshold is 105%The method can obtain:
Xn (n=1, 2, 3, 4, 5, 6) is 95% When the polygonal nut 4 and the backing plate 5 are not inclined at the position;
xn (n=1, 2, 3, 4, 5, 6) > upper threshold 105% When the inclination angle of the polygonal nut 4 at the position is deviated to the direction of the backing plate 5;
xn (n=1, 2, 3,4, 5, 6) < lower threshold 95% When the inclination angle of the polygonal nut 4 at the position is deviated to the direction away from the backing plate 5;
Thus, the inclination condition between the polygonal nut 4 and the pad plate 5 can be obtained through step S4, and the leveling process can be performed according to the inclination condition.
In the embodiment, the stress wave driver 11 and the stress wave sensor 12 are arranged on the polygonal nut 4 and the backing plate 5 of the prestress structure, the stress wave driver 11 transmits stress waves, the stress waves are transmitted inside the prestress structure, and then feedback signals are received through the stress wave sensor 12, so that the prestress loss condition inside the prestress structure is calculated and analyzed. The detection structure and the method disclosed by the invention can rapidly and accurately obtain the prestress loss condition in the prestress structure, so that the internal prestress of the prestress structure can be kept in a reasonable range, and the prestress failure is avoided.
Referring to fig. 4, the tensile force in the prestress structure is transmitted to the nut by the engagement of the member 2 with the tendon 3, and the nut presses the pad 5 to transmit the pressing force generated by the pressing to the member 2. In the present embodiment, the change of the prestress directly affects the contact pressure between the polygonal nut 4 and the backing plate 5, so that the actual contact area of the polygonal nut 4 and the backing plate 5 is changed according to the change of the prestress. When the prestress increases, the actual contact area between the polygonal nut 4 and the backing plate 5 increases, so that when the high-frequency stress wave generated by the piezoceramic actuator is transmitted between the nut and the backing plate 5, the propagation of the stress wave is easier along with the increase of the actual contact area, and therefore, the energy received by the piezoelectric sensor gradually increases along with the increase of the actual contact area. Along with the increase of the prestress, the actual contact area between the polygonal nut 4 and the backing plate 5 is increased, the signal received by the piezoelectric sensor is also enhanced, and the prestress can be detected by analyzing the difference of the received signals under different working conditions.
The technical features of the above-described embodiments may be arbitrarily combined, and all possible combinations of the technical features in the above-described embodiments are not described for brevity of description, however, as long as there is no contradiction between the combinations of the technical features, they should be considered as the scope of the description.
The above examples illustrate only a few embodiments of the application, which are described in detail and are not to be construed as limiting the scope of the claims. It should be noted that it will be apparent to those skilled in the art that several variations and modifications can be made without departing from the spirit of the application, which are all within the scope of the application. Accordingly, the scope of protection of the present application is to be determined by the appended claims.