Acoustic emission-based early warning method for void of concrete filled steel tube in construction process

Abstract

The invention provides a construction process concrete filled steel tube void early warning method based on acoustic emission, which comprises the following steps: monitoring the internal structure change of a steel tube in the construction process according to an acoustic emission signal, and early warning and positioning the void of the concrete filled steel tube; a probe pair composed of a transmitting probe and a receiving probe is used for monitoring the internal void state of the concrete filled steel tube in an active acoustic emission mode, and the early warning method comprises the steps of acoustic emission probe deployment, trigger monitoring, void height positioning and void judgment. The method has the beneficial effects that low-cost concrete filled steel tube void monitoring early warning and height prediction are realized in the construction process.

Description

Technical Field

[0001] The invention belongs to the technical field of construction monitoring, and in particular relates to an acoustic emission-based early warning method for hollowing out of steel tube concrete during a construction process. Background Art

[0002] During the construction process, steel tube concrete structures often become hollow due to loose concrete pouring or poor bonding, which seriously affects the safety and durability of the structure. Existing detection technologies such as ultrasonic, impact echo and radar detection have obvious limitations in the construction environment: Ultrasonic detection requires coupling agent to ensure good contact between the probe and the surface of the steel tube, which is difficult to achieve in a dynamic construction environment and has high technical requirements for operators; the impact echo method relies on manual knocking to generate stress waves, and the signal is 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 concrete inside the steel tube, but the signal resolution at the interface between the steel tube and concrete is low, and is greatly affected by the wall thickness of the steel tube and the moisture content of the concrete, so the detection results are prone to misjudgment; traditional acoustic emission technology is mostly used for damage monitoring of static structures, lacks real-time monitoring and early warning mechanisms for dynamic construction environments, and has insufficient positioning accuracy for hollow areas. These limitations make it difficult for existing technologies to meet the needs of real-time and accurate monitoring of steel tube concrete hollowing during construction. Summary of the invention

[0003] In view of this, the present invention aims to propose a steel tube concrete void early warning method during construction based on acoustic emission, so as to achieve low-cost steel tube concrete void monitoring, early warning and height prediction during construction.

[0004] To achieve the above object, the technical solution of the present invention is achieved as follows: Early warning method for voiding of concrete-filled steel tubes during construction based on acoustic emission.

[0005] Furthermore, the changes in the internal structure of the steel tube during the construction process are monitored based on the acoustic emission signals, and the steel tube concrete is de-hollowed out to warn and locate the location; 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 space judgment: Calculate the empty space probability of each probe pair, eliminate the empty space 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 space probability based on the empty space probability of the remaining probe pairs. When the global empty space probability exceeds the set threshold, an empty space alarm is triggered.

[0006] Furthermore, in T1, the horizontal indirection between the transmitting probe and the receiving probe in the same probe pair satisfies the sound wave passing 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.

[0007] Furthermore, in said 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, This probe is used to measure the sound propagation time when there is no void in the steel tube concrete.

[0008] Furthermore, the sound propagation time when there is no air leakage is 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.

[0009] Furthermore, 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.

[0010] Furthermore, in 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 approximation: ; ; 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.

[0011] Furthermore, in 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; 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.

[0012] Furthermore, 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.

[0013] Furthermore, when the steel pipe diameter is lower than the set value, the following formula is used to calculate the probability of emptying: .

[0014] Furthermore, the concrete sound velocity is updated 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.

[0015] Compared with the prior art, the method for early warning of steel tube concrete voiding during construction based on acoustic emission according to the present invention has the following beneficial effects: (1) The early warning method of the present invention realizes real-time monitoring and timely early warning of the degassing of steel tube concrete during construction through acoustic emission probes and a computer analysis system, thereby significantly improving construction safety and quality control efficiency; (2) The early warning method described in the present invention uses a double-threshold cross-correlation algorithm and LVMD decomposition technology to accurately predict the location and height of the empty area, providing accurate data support for repair work; (3) The early warning method described in the present invention effectively eliminates environmental noise and abnormal signals through peripheral redundant probes and a double-threshold cross-correlation algorithm, thereby improving the reliability and stability of the detection results and reducing the false alarm and missed alarm rates; (4) The early warning method described in the present invention dynamically adjusts the probe arrangement and sound velocity parameters according to the steel pipe diameter and the construction stage, ensuring the applicability of the system in different construction environments and enhancing the universality and flexibility of the solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] The accompanying drawings constituting a part of the present invention are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute an improper limitation of the present invention. In the accompanying drawings: Figure 1 This is a schematic diagram of the early warning method flow according to an embodiment of the present invention; Figure 2 A schematic diagram of the deployment of probe pairs according to an embodiment of the present invention; Figure 3 This is a schematic diagram of the degassing monitoring principle described in an embodiment of the present invention. DETAILED DESCRIPTION

[0017] It should be noted that, in the absence of conflict, the embodiments of the present invention and the features in the embodiments may be combined with each other.

[0018] The present invention will be described in detail below with reference to the accompanying drawings and in conjunction with embodiments.

[0019] The method for early warning of steel tube concrete voiding during construction based on acoustic emission monitors the internal structural changes of the steel tube during construction according to the acoustic emission signal, and warns and locates the steel tube concrete voiding; a probe pair consisting of a transmitting probe and a receiving probe is used to monitor the internal voiding state of the steel tube concrete in the form of active acoustic emission. Through the longitudinal distributed probe pair arrangement, time difference estimation method and lightweight signal processing framework, the decimeter-level positioning accuracy of the steel tube concrete voiding height can be achieved without the need for complex mobile equipment.

[0020] Specific as Figure 1 As shown, 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 space judgment: Calculate the empty space probability of each probe pair, eliminate the empty space 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 space probability based on the empty space probability of the remaining probe pairs. When the global empty space probability exceeds the set threshold, an empty space alarm is triggered.

[0021] Further Figure 2 As shown in Figure 1, in T1, the horizontal indirection between the transmitting probe and the receiving probe in the same probe pair satisfies the sound wave passing 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. The active acoustic emission signal monitoring path is: the acoustic energy emitted by the transducer in the transmitting probe passes through the steel pipe and is captured by the corresponding receiving probe, and is gain-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 ringing number, energy, amplitude, etc., and finally passes it to the computer for numerical analysis.

[0022] Specifically, T2 adopts hybrid trigger monitoring to capture effective acoustic emission events under low power consumption conditions and reduce invalid data transmission. Its monitoring mode is: Event trigger: When the environmental noise energy Eenv exceeds the threshold Eth=50eu, active detection is started. Scheduled inspection: Forced to start a full network scan every 2 hours to prevent missed detection.

[0023] Detailed computer analysis of acoustic emission signals to extract key features , control the size of data packets, improve computer resource utilization, 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, This probe is used to measure the sound propagation time when there is no void in the steel tube concrete.

[0024] 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.

[0025] 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.

[0026] Specific as Figure 3 As shown, in 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 In the signal interval above the set threshold, double threshold filtering can be used to accurately estimate the time difference of arrival of sound waves from noise. , the peak position of the cross-correlation function corresponds to the time difference of sound wave propagation, the sound time difference Approximate calculation: ; ; 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 .

[0027] Furthermore, the LVMD variational mode decomposes the original signal of the receiving probe in each probe pair into several modal components to extract the damage-sensitive features of the air gap signal, including: ; In the formula, is the kth modal component, is the kth modal component energy. If there is a gap, the high-frequency energy Increase, low frequency energy Reduced, resulting in capacity Increase.

[0028] Specifically, in T4, the calculation of the probability of missing includes: ; In the formula, The function is used to map the target function to the interval [0, 1]. is the acoustic time difference of the i-th probe pair, is the maximum sound time difference without air leakage; coefficients 0.1, 0.4, and 0.5 are the optimal weight distribution obtained from experiments.

[0029] 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.

[0030] Optionally, 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.

[0031] Optionally, when the steel pipe diameter is lower than the set value, the following formula is used to calculate the probability of voiding: ; This formula is applicable to the case where the steel pipe has a smaller diameter, because at this time the sound wave propagation path is shorter, and the modal component energy ratio can more accurately reflect the void characteristics. Calculating the void probability by the modal component energy ratio can avoid errors caused by insufficient acoustic time difference data and improve the accuracy of the detection results.

[0032] Optionally, the concrete sound velocity can change over time at different stages of construction, updating the 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.

[0033] Those of ordinary skill in the art will appreciate that the units and method steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in terms of function in the above description. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professional and technical personnel can use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0034] In the several embodiments provided in the present application, it should be understood that the disclosed methods and systems can be implemented in other ways. For example, the division of the units described above is only a logical function division, and there may be other division methods in actual implementation, such as 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 displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the units may be selected according to actual needs to achieve the purpose of the embodiments of the present invention.

[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein by equivalents. These modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention, and they should all be included in the scope of the claims and specification of the present invention.

[0036] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principle of the present invention should be included in 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 space judgment: Calculate the empty space probability of each probe pair, eliminate the empty space 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 space probability based on the empty space probability of the remaining probe pairs. When the global empty space probability exceeds the set threshold, an empty space alarm is triggered.

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: 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, This probe is used to measure the sound propagation time when there is no void in the steel tube concrete.

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: 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.

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 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.

6. 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 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 approximation: ； ； 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.

7. The method for early warning of de-airing of concrete-filled steel tubes during construction based on acoustic emission according to claim 6, 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; 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.

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: 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.

9. The method for early warning of concrete-filled steel tube voids during construction based on acoustic emission according to claim 4, characterized in that: When the steel pipe diameter is lower than the set value, the following formula is used to calculate the probability of emptying: 。 10. The method for early warning of concrete-filled steel tube voids during construction based on acoustic emission according to claim 4, characterized in that: 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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