Acoustic Emission-Based Early Warning Method for Debonding of Concrete-Filled Steel Tubes during Construction

Abstract

The present invention provides a method for warning against the debonding of concrete-filled steel tubes during construction based on acoustic emission. According to the acoustic emission signal, the internal structure change of the steel tube during construction is monitored to warn against and locate the debonding of the concrete-filled steel tube. A pair of probes composed of a transmitting probe and a receiving probe is used to monitor the debonding state inside the concrete-filled steel tube in the form of active acoustic emission. The warning method includes: deploying acoustic emission probes, triggering monitoring, locating the debonding height, and determining the debonding. The beneficial effects of the present invention are: realizing low-cost monitoring, warning, and height prediction of the debonding of concrete-filled steel tubes during construction.

Description

Technical Field

[0001] The present invention belongs to the technical field of construction monitoring, and particularly relates to a method for warning of concrete-filled steel tube voids during the construction process based on acoustic emission. Background Art

[0002] During the construction process of concrete-filled steel tube structures, voids often occur due to improper compaction or poor bonding of concrete, seriously affecting the structural safety and durability. Existing detection techniques such as ultrasonic, impact echo, and radar detection have obvious limitations in the construction environment: Ultrasonic detection requires a couplant to ensure good contact between the probe and the steel tube surface, which is difficult to achieve in a dynamic construction environment and has high technical requirements for operators; The impact echo method relies on manual tapping to generate stress waves, and the signals are easily submerged by noise in a noisy construction environment, with low detection efficiency and difficulty in covering large areas; Radar detection is sensitive to changes in the dielectric constant of the concrete inside the steel tube, but has low signal resolution at the interface between the steel tube and the concrete and is greatly affected by the steel tube wall thickness and concrete moisture content, resulting in easy misjudgment of the detection results; Traditional acoustic emission technology is mostly used for damage monitoring of static structures, lacking a real-time monitoring and warning mechanism for dynamic construction environments and having insufficient positioning accuracy for void areas. These limitations make it difficult for existing technologies to meet the requirements of real-time and accurate monitoring of concrete-filled steel tube voids during the construction process. Summary of the Invention

[0003] In view of this, the present invention aims to propose a method for warning of concrete-filled steel tube voids during the construction process based on acoustic emission to achieve low-cost monitoring and warning of concrete-filled steel tube voids and high-precision prediction during the construction process.

[0004] To achieve the above object, the technical solution of the present invention is realized as follows:

[0005] A method for warning of concrete-filled steel tube voids during the construction process based on acoustic emission.

[0006] Furthermore, monitor the internal structure changes of the steel tube during the construction process according to the acoustic emission signals, and warn and locate the voids in the concrete-filled steel tube;

[0007] Use a pair of probes composed of a transmitting probe and a receiving probe to monitor the void state inside the concrete-filled steel tube in the form of active acoustic emission. The warning method includes:

[0008] T1. Deploy acoustic emission probes: Arrange several pairs of probes along the longitudinal axis of the outer wall of the concrete-filled steel tube column, and each pair of probes is located on the same plane;

[0009] T2. Trigger monitoring: The acoustic emission instrument performs regular inspections, or an active detection is performed when the acoustic emission energy generated by the construction environment exceeds the set threshold, and the monitored acoustic emission signals are transmitted to the computer for analysis;

[0010] T3. Debonding height positioning: The time difference of sound waves between each pair of probes is extracted using the double-threshold cross-correlation algorithm. The original signal of each pair of probes is decomposed by LVMD (Variational Mode Decomposition) to predict the debonding probability. The debonding height data located by each pair of probes is calculated based on the time difference of sound wave data.

[0011] T4. Debonding determination: Calculate the debonding probability of each pair of probes. Based on the time difference information of the sound waves of the redundant probes outside each pair of probes, eliminate the debonding probability of the abnormal probe pairs. Calculate the global debonding probability by synthesizing the debonding probabilities of the remaining probe pairs. When the global debonding probability exceeds the set threshold, an alarm for debonding is given.

[0012] Furthermore, in T1, the horizontal distance between the transmitting probe and the receiving probe in the same probe pair satisfies that the sound wave passes through the core concrete. The vertical spacing of each pair of probes is equal, and the probe pairs cover the entire height range of the steel pipe.

[0013] Furthermore, in T3, the computer analyzes the acoustic emission signal to extract the main features , including:

[0014] ;

[0015] ;

[0016] In the formula, is the energy of the first two modal components of the acoustic emission amplitude signal, is the time difference of sound waves of this pair of probes, is the frequency centroid of the acoustic emission signal, is the actually measured sound propagation time of this probe pair, is the sound propagation time when there is no debonding in the steel pipe concrete measured by this probe pair.

[0017] Furthermore, the calculation of the sound propagation time when there is no debonding includes:

[0018] ;

[0019] In the formula, is the vertical spacing between the probe pairs, is the sound velocity of the concrete, is the sound velocity of the steel, is the wall thickness of the steel pipe, is the diameter of the steel pipe;

[0020] ;

[0021] In the formula, is the spectrum of the acoustic emission amplitude signal, is the frequency point, and N and K are accumulation parameters.

[0022] Further, in the T3, when the void area is located between a certain pair of probes, the approximate calculation of the concrete void height includes:

[0023] ;

[0024] In the formula, is the approximate solution of the void height, is the reference height of the i-th pair of probes, is the acoustic wave incident angle of this pair of probes.

[0025] Further, in the T3, the computer extracts the acoustic time difference and the energy ratio from the received low signal-to-noise ratio signals. The double-threshold cross-correlation algorithm includes a first threshold: eliminating the signal segments with the acoustic emission signal amplitude lower than the set threshold, and a second threshold: retaining the signal interval with the acoustic emission signal energy integral higher than the set threshold. The approximate value of the acoustic time difference is:

[0026] ;

[0027] ;

[0028] In the formula, is the energy time-domain signal of the receiving probe, is the time-domain signal emitted by the transmitting probe; is the time-domain signal received by the receiving probe; , are the signal valid intervals, determined by the acoustic emission amplitude signal and the energy signal; is the time delay variable; represents traversing the time domain within the limited interval of the acoustic emission signal to find the time delay when the correlation between the transmitting probe and the receiving probe is the largest;

[0029] The LVMD variational mode decomposes the original signal of the receiving probe in each pair of probes into several modal components, including:

[0030] ;

[0031] In the formula, is the k-th modal component, is the energy of the k-th modal component.

[0032] Further, in the T4, the calculation of the void probability includes:

[0033] ;

[0034] In the formula, is the acoustic time difference of the i-th pair of probes, is the maximum acoustic time difference without debonding;

[0035] The calculation of the global debonding probability includes:

[0036] ;

[0037] ;

[0038] In the formula, is the average acoustic time difference of all detected probe pairs, is the debonding weight of the i-th pair of probes, is the standard deviation of the acoustic time difference;

[0039] When , it is determined that the concrete-filled steel tube is not debonded;

[0040] When , remind the worker to manually check and confirm the debonding condition of the concrete-filled steel tube;

[0041] When , send out an alarm message for the debonding of the concrete-filled steel tube.

[0042] Furthermore, the peripheral redundant probes are arranged on the upper and lower sides of the receiving probe of the adjacent probe pair. The peripheral redundant probes receive the acoustic wave signals of the transmitting probe of this probe pair. Only when the acoustic time difference of the upper-side peripheral redundant probe and the acoustic time difference of the lower-side peripheral redundant probe , it is determined that the acoustic emission monitoring value of this probe pair is normal and effective this time. Otherwise, eliminate the acoustic emission monitoring signal of this probe pair this time, , is the increment of this probe relative to the .

[0043] Furthermore, when the diameter of the steel tube is lower than the set value, the following formula is used to calculate the debonding probability:

[0044] .

[0045] Furthermore, update the concrete sound velocity at different construction stages:

[0046] ;

[0047] In the formula, t is the construction time, , are all concrete sound velocity age parameters, is the initial concrete sound velocity, is the real-time sound velocity of concrete.

[0048] Compared with the prior art, the method for warning of concrete-filled steel tube void during construction based on acoustic emission of the present invention has the following beneficial effects:

[0049] (1) For the warning method of the present invention, through acoustic emission probes and a computer analysis system, real-time monitoring and timely warning of the void of concrete-filled steel tube during construction are realized, significantly improving construction safety and quality control efficiency;

[0050] (2) For the warning method of the present invention, a double-threshold cross-correlation algorithm and LVMD decomposition technology are adopted to accurately predict the position and height of the void area, providing accurate data support for the repair work;

[0051] (3) For the warning method of the present invention, through peripheral redundant probes and a double-threshold cross-correlation algorithm, environmental noise and abnormal signals are effectively eliminated, improving the reliability and stability of the detection results and reducing the false alarm and missed alarm rates;

[0052] (4) For the warning method of the present invention, the probe arrangement and sound velocity parameters are dynamically adjusted according to the steel tube diameter and construction stage to ensure the applicability of the system in different construction environments, enhancing the universality and flexibility of the solution. Description of the Drawings

[0053] The drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The schematic embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation to the present invention. In the drawings:

[0054] Figure 1 is a schematic flow chart of the warning method described in the embodiment of the present invention;

[0055] Figure 2 is a schematic diagram of the deployment of probe pairs described in the embodiment of the present invention;

[0056] Figure 3 is a schematic diagram of the void monitoring principle described in the embodiment of the present invention. Detailed Embodiments

[0057] It should be noted that, without conflict, the embodiments in the present invention and the features in the embodiments may be combined with each other.

[0058] The present invention will be described in detail below with reference to the drawings and in combination with the embodiments.

[0059] Acoustic Emission-Based Early Warning Method for Debonding in Concrete-Filled Steel Tubes during Construction. It monitors the internal structure changes of the steel tube during construction according to acoustic emission signals, warns and locates the debonding of concrete-filled steel tubes. A pair of probes consisting of a transmitting probe and a receiving probe is used to monitor the debonding state inside the concrete-filled steel tube in the form of active acoustic emission. Through the longitudinal distributed probe pair arrangement, time difference estimation algorithm and lightweight signal processing framework, the decimeter-level positioning accuracy of the debonding height of concrete-filled steel tubes can be achieved without the need for complex mobile equipment.

[0060] Specifically, as Figure 1 shown, the early warning method includes:

[0061] T1. Deploy acoustic emission probes: Arrange several groups of probe pairs along the longitudinal axis of the outer wall of the concrete-filled steel tube column, and each group of probe pairs is located on the same plane;

[0062] T2. Trigger monitoring: The acoustic emission instrument performs regular inspections, or when the acoustic emission energy generated in the construction environment exceeds the set threshold, an active detection is performed once, and the monitored acoustic emission signals are transmitted to the computer for analysis;

[0063] T3. Debonding height positioning: The double-threshold cross-correlation algorithm is used to extract the acoustic time difference of each group of probe pairs, and the variational mode decomposition (VMD) is used to decompose the original signals of each group of probe pairs to predict the debonding probability. The debonding height data located by each group of probe pairs is calculated according to the acoustic time difference data;

[0064] T4. Debonding determination: Calculate the debonding probability of each group of probe pairs, eliminate the debonding probability of abnormal probe pairs based on the acoustic time difference information of the redundant probes outside each group of probe pairs, calculate the global debonding probability by synthesizing the debonding probabilities of the remaining probe pairs, and alarm for debonding when the global debonding probability exceeds the set threshold.

[0065] Furthermore, as Figure 2 shown, in T1, the horizontal distance between the transmitting probe and the receiving probe in the same probe pair satisfies that the sound wave passes through the core concrete, the vertical distance of each group of probe pairs is equal, and the probe pairs cover the entire height range of the steel tube. The monitoring path of the active acoustic emission signal is: The transducer in the transmitting probe emits acoustic energy, which passes through the steel tube and is captured by the corresponding receiving probe, is amplified and filtered by the preamplifier in the form of an acoustic emission signal, and then the acoustic emission instrument processes the acoustic emission signal to generate time-domain signals such as ring count, energy, and amplitude, and finally transmits them to the computer for numerical analysis.

[0066] Specifically, the purpose of using hybrid trigger monitoring in T2 is to capture effective acoustic emission events under low power consumption conditions and reduce the transmission of invalid data. Its monitoring mode is: Event trigger: When the environmental noise energy Eenv exceeds the threshold Eth = 50 eu, an active detection is started. Regular inspection: Force a full network scan every 2 hours to prevent missed detections.

[0067] Specific computer analyzes acoustic emission signals to extract main features , controls the size of data packets, improves the resource utilization rate of the computer, and the features include:

[0068] ;

[0069] ;

[0070] In the formula, is the energy of the first two modal components of the acoustic emission amplitude signal, is the acoustic time difference of this pair of probes, is the frequency centroid of the acoustic emission signal, is the actual measured sound propagation time of this pair of probes, is the sound propagation time when there is no debonding in the concrete-filled steel tube measured by this pair of probes.

[0071] The sound propagation time when there is no debonding The calculation includes:

[0072] ;

[0073] In the formula, is the vertical distance between the probe pairs, is the sound velocity of concrete, is the sound velocity of steel, is the wall thickness of the steel pipe, is the diameter of the steel pipe;

[0074] ;

[0075] In the formula, is the spectrum of the acoustic emission amplitude signal, is the frequency point, and N and K are accumulation parameters.

[0076] When the debonding area is located between a certain pair of probes, the approximate calculation of the debonding height of concrete includes:

[0077] ;

[0078] In the formula, is the approximate solution of the debonding height, is the reference height of the i-th pair of probes, is the acoustic wave incident angle of this pair of probes.

[0079] Specifically, as Figure 3 shown, in the T3, the computer extracts the acoustic time difference and the energy ratio , the double-threshold cross-correlation algorithm includes a first threshold: eliminating signal segments with the amplitude of the acoustic emission signal lower than the set threshold, and a second threshold: retaining the signal interval with the energy integral of the acoustic emission signal higher than the set threshold. By using double-threshold filtering, the time difference of arrival of sound waves can be accurately estimated from the noise , the cross-correlation function corresponds to the time difference of sound wave propagation at the peak position, and the time difference of sound approximate value calculation:

[0080] ;

[0081] ;

[0082] In the formula, is the energy time-domain signal of the receiving probe, is the time-domain signal emitted by the transmitting probe; is the time-domain signal received by the receiving probe; , are the signal effective intervals, determined by the acoustic emission amplitude signal and the energy signal; is the time delay variable; represents traversing the time domain within the limited interval of the acoustic emission signal to find the transmitting probe and the receiving probe the time delay with the maximum correlation between the two signals .

[0083] Furthermore, the LVMD variational mode decomposes the original signal of the receiving probe in each pair of probes into several mode components to extract the damage-sensitive features of the void signal, including:

[0084] ;

[0085] In the formula, is the k-th mode component, is the energy of the k-th mode component. If there is a void, it will cause the high-frequency energy to increase and the low-frequency energy to decrease, resulting in an increase in the energy ratio .

[0086] Specifically, in the T4, the calculation of the void probability includes:

[0087] ;

[0088] In the formula, the function is used to map the objective function to the interval [0, 1], is the time difference of sound of the i-th pair of probes, is the maximum time difference of sound without void; the coefficients 0.1, 0.4, and 0.5 are the optimal weight distributions obtained from experiments.

[0089] The global void probability calculation includes:

[0090] ;

[0091] ;

[0092] In the formula, is the average acoustic time difference of all detection probe pairs, is the void weight of the i-th group of probe pairs, is the standard deviation of the acoustic time difference;

[0093] When , it is determined that the concrete-filled steel tube is not void;

[0094] When , the worker is reminded to manually check and confirm the void condition of the concrete-filled steel tube;

[0095] When , an alarm message for the void of the concrete-filled steel tube is issued.

[0096] Optionally, the peripheral redundant probes are arranged on the upper and lower sides adjacent to the receiving probe of the probe pair. The peripheral redundant probes receive the acoustic wave signals of the transmitting probe of the probe pair. Only when the acoustic time difference of the upper-side peripheral redundant probe and when the acoustic time difference of the lower-side peripheral redundant probe , it is determined that the acoustic emission monitoring value of this probe pair is normal and valid. Otherwise, the acoustic emission monitoring signal of this probe pair is excluded, 、 is the increment of this probe relative to the .

[0097] Optionally, when the diameter of the steel tube is lower than the set value, the following formula is used to calculate the void probability:

[0098] ;

[0099] This formula is applicable to the case of a smaller diameter of the steel tube. Because at this time, the acoustic wave propagation path is shorter, and the modal component energy ratio can more accurately reflect the void characteristics. Calculating the void probability through the modal component energy ratio can avoid errors caused by insufficient acoustic time difference data and improve the accuracy of the detection results.

[0100] Optionally, at different construction stages, the concrete sound velocity changes with time, and the concrete sound velocity is updated at different construction stages:

[0101] ;

[0102] In the formula, t is the construction time, 、 They are all the age-related parameters of the concrete sound velocity, is the initial sound velocity of the concrete, is the real-time sound velocity of the concrete.

[0103] Those of ordinary skill in the art can realize that the units and method steps of each example described in combination with the embodiments disclosed herein can be implemented by electronic hardware, computer software, or a combination of the two. To clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described according to functions in the above description. Whether these functions are executed in a hardware or software manner depends on the specific application and design constraints of the technical solution. Professional technicians can use different methods to implement the described functions for each specific application, but such implementation should not be considered to exceed the scope of the present invention.

[0104] In several embodiments provided by the present application, it should be understood that the disclosed methods and systems can be implemented in other ways. For example, the above-mentioned division of units is only a logical function division, and there can be other division methods in actual implementation. For example, multiple units or components can be combined or integrated into another system, or some features can be ignored or not executed. The above-mentioned units may or may not be physically separated, and the components shown as units may or may not be physical units, that is, they can be located in one place or distributed to multiple network units. Some or all of the units can be selected according to actual needs to achieve the purpose of the solution of the embodiments of the present invention.

[0105] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

[0106] The above is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for early warning of de-airing of concrete-filled steel tubes during construction based on acoustic emission, characterized in that: Monitor the internal structure changes of steel pipes during construction based on acoustic emission signals, and warn and locate the voids in steel pipe concrete; Using a probe pair consisting of a transmitting probe and a receiving probe, the internal voiding state of the steel tube concrete is monitored in the form of active acoustic emission. The early warning methods include: T1. Deployment of acoustic emission probes: several sets of probe pairs are arranged along the longitudinal axis of the outer wall of the steel tube concrete column, and each set of probe pairs is located on the same plane; T2. Trigger monitoring: The acoustic emission instrument performs regular inspections, or when the acoustic emission energy generated by the construction environment exceeds the set threshold, an active detection is performed, and the monitored acoustic emission signal is transmitted to the computer for analysis; T3, air gap height positioning: the double threshold cross-correlation algorithm is used to extract the acoustic time difference of each probe pair, and the original signal of each probe pair is decomposed by LVMD variational mode to predict the air gap probability. The air gap height data of each probe pair is calculated based on the acoustic time difference data; T4, Empty Determination: Calculate the empty probability of each probe pair, remove the empty probability of abnormal probe pairs based on the acoustic time difference information of the redundant probes outside each probe pair, and calculate the global empty probability based on the empty probability of the remaining probe pairs. When the global empty probability exceeds the set threshold, an alarm is triggered. In the T3, the computer analyzes the acoustic emission signal to extract the main features ,include: ； ； In the formula, is the energy of the first two modal components of the acoustic emission amplitude signal, is the acoustic time difference of the probe pair, is the frequency center of gravity of the acoustic emission signal, is the sound propagation time actually measured by the probe, The sound propagation time of the probe when measuring the steel tube concrete without voids; In the T3, the computer extracts the acoustic time difference from the received low signal-to-noise ratio signal and energy ratio The double-threshold cross-correlation algorithm includes a first threshold: removing the signal segment whose acoustic emission signal amplitude is lower than the set threshold, and a second threshold: retaining the acoustic emission signal energy integral The signal interval above the set threshold, the sound time difference Approximate value of for: ； ； In the formula, To receive the energy time domain signal of the probe, is the time domain signal emitted by the transmitting probe; The time domain signal received by the receiving probe; , is the signal effective interval, which is determined by the acoustic emission amplitude signal and energy signal; is the time delay variable; Indicates that within the finite interval of the acoustic emission signal, traverse the time domain to find the transmitting probe With receiving probe The time delay when the correlation between the two signals is the largest ; The LVMD variational mode decomposes the original signal of the receiving probe in each probe pair into several modal components, including: ； In the formula, is the kth modal component, is the energy of the kth modal component.

2. The method for early warning of de-airing of concrete-filled steel tubes during construction based on acoustic emission according to claim 1 is characterized by: In T1, the horizontal indirection between the transmitting probe and the receiving probe in the same probe pair satisfies the sound wave to pass through the core concrete, the vertical spacing of each probe pair is equal, and the probe pair covers the full height range of the steel pipe.

3. The method for early warning of de-airing of concrete-filled steel tubes during construction based on acoustic emission according to claim 1, characterized in that: The sound propagation time when there is no air gap The calculations include: ； In the formula, is the vertical spacing between the probe pairs, is the speed of sound in concrete, is the speed of sound in steel, is the wall thickness of the steel pipe, is the diameter of the steel pipe; ； In the formula, is the spectrum of the acoustic emission amplitude signal, is the frequency point, N and K are the cumulative parameters.

4. The method for early warning of de-airing of concrete-filled steel tubes during construction based on acoustic emission according to claim 3 is characterized by: In T3, when the void area is located between a pair of probes, the approximate calculation of the concrete void height includes: ； In the formula, is the approximate solution of the void height, is the reference height of the i-th probe pair, is the incident angle of the sound wave for the probe pair.

5. The method for early warning of de-airing of concrete-filled steel tubes during construction based on acoustic emission according to claim 4 is characterized in that: In the step T4, the calculation of the probability of missing includes: ； In the formula, is the acoustic time difference of the i-th probe pair, It is the maximum sound time difference without being lost; The global escape probability calculation includes: ； ； In the formula, is the average acoustic time difference of all detection probe pairs, is the empty weight of the i-th probe pair, is the standard deviation of the acoustic time difference; when When the steel tube concrete is not empty, it is judged that the steel tube concrete is not empty; when When the steel tube concrete is empty, remind the workers to manually check and confirm the emptying status; when When the steel tube concrete is de-filled, an alarm message is issued.

6. The method for early warning of concrete-filled steel tube voids during construction based on acoustic emission according to claim 1, characterized in that: The peripheral redundant probe is arranged on the upper and lower sides of the receiving probe of the adjacent probe pair, and the peripheral redundant probe receives the acoustic wave signal of the transmitting probe of the probe pair. And the lower side peripheral redundant probe sound time difference The probe is considered to be normal and effective for this acoustic emission monitoring value, otherwise the probe's acoustic emission monitoring signal is rejected. , The probe is relative to the increment.

7. The method for early warning of de-airing of concrete-filled steel tubes during construction based on acoustic emission according to claim 3 is characterized by: When the steel pipe diameter is lower than the set value, the following formula is used to calculate the probability of emptying: 。 8. The method for early warning of de-airing of concrete-filled steel tubes during construction based on acoustic emission according to claim 3 is characterized by: Updates on concrete sound velocity at different stages of construction: ； Where t is the construction time, , All are concrete sound velocity age parameters, is the initial sound velocity of concrete, Real-time speed of sound in concrete.

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