A kind of active and passive integrated concrete structure monitoring system and detection method

Abstract

This invention belongs to the field of concrete structure health monitoring technology, and discloses an integrated active and passive concrete structure monitoring system and detection method. The system includes n externally mounted PZT sensors, an n-channel transceiver switching control box, a preamplifier, an acoustic emission acquisition instrument, a signal generator, a power amplifier, and a power supply module. The n-channel transceiver switching control box uses a two-position toggle switch structure to achieve hardware isolation and manual switching between high-voltage excitation and low-voltage reception paths, and uses the same set of sensor arrays to achieve dual-mode switching between active fluctuation scanning and passive acoustic emission monitoring. This invention can use the same set of externally mounted PZT sensor arrays for both active excitation and passive acoustic emission reception, eliminating the need for two independent sensor arrays. Active damage indicators and passive acoustic emission data can be directly compared and verified under the same sensor position and spatial coordinate system, eliminating the influence of sensitivity differences between different batches of sensors.

Description

Technical Field

[0001] This invention belongs to the field of concrete structure health monitoring technology, specifically relating to an integrated active and passive concrete structure monitoring system and detection method, applicable to damage detection and condition assessment of concrete components such as railway subgrade retaining structures and concrete beams. Background Technology

[0002] Under the long-term coupling effect of train dynamic loads and the surrounding environment, roadbed retaining structures and composite foundations will develop typical defects such as cracks, voids, and subsidence, seriously affecting the operational safety of the line. In the field of concrete structure health monitoring, detection methods based on piezoelectric ceramics are mainly divided into three categories: mechanical impedance method, which identifies damage by measuring the impedance spectrum changes of the PZT (lead zirconate titanate) structural coupling system, but the detection range is limited to about 10-15cm around the sensor, and large-scale monitoring requires dense distribution of points; active wave method, which assesses damage by emitting stress waves on one side and receiving them on the other side and comparing the signal changes before and after damage, but current research mainly uses built-in smart aggregates, which need to be pre-embedded during the pouring stage and cannot be used for existing structures; passive acoustic method, which uses PZT sensors to passively receive the elastic waves released when concrete cracks, and locates the crack source through multi-channel time difference. This method can only monitor new damage occurring during loading and cannot detect existing defects that existed before loading.

[0003] A few studies have attempted to combine the active wave method with the passive acoustic emission method, but these typically employ two independent sensor arrays to handle active excitation reception and passive AE (Acoustic Emission) monitoring, respectively. The two sets of sensors are installed in different locations, and the active damage indicators and passive AE data do not spatially overlap, making direct comparison and verification impossible. Furthermore, the active excitation end requires a high-voltage power amplifier, and the passive AE receiving end is connected to a high-gain preamplifier. If the two circuits share a sensor, there is a risk of crosstalk between the high-voltage side and the low-voltage side. Existing solutions mostly achieve transmit / receive switching through manual plugging and unplugging or discrete wiring. The modules are built in a dispersed manner, requiring rewiring, channel-by-channel troubleshooting, and gain calibration before each experiment or field test. This preparation time is long, and manual wiring carries the risk of mis-plugging, hindering rapid field deployment and repeated testing. Summary of the Invention

[0004] To address the problems existing in the background technology, this invention proposes an integrated active and passive concrete structure monitoring system and detection method. By integrating n-channel PZT sensor interfaces, high-voltage excitation interfaces, toggle switch switching control, signal conditioning, data acquisition and power supply into a portable industrial control chassis, a two-position toggle switch is used to achieve hardware isolation and manual switching between high-voltage excitation and low-voltage receiving paths, and the same set of sensor arrays is used to achieve dual-mode switching between active fluctuation scanning and passive acoustic emission monitoring.

[0005] To achieve the above objectives, the present invention provides the following technical solution: An integrated active-passive concrete structure monitoring system includes n externally mounted PZT sensors, an n-channel transceiver switching control box, a preamplifier, an acoustic emission acquisition instrument, a signal generator, a power amplifier, and a power supply module. The PZT sensors are fixed to the surface of the concrete structure to passively receive acoustic signals or actively emit excitation signals. The output of the signal generator is connected to the input of the power amplifier; the signal generator outputs an excitation signal, which is boosted by the power amplifier to drive the selected PZT sensor. The n-channel transceiver switching control box includes n independent two-position toggle switches, used to independently control the n PZT sensors to switch between receiving and excitation states. The common terminal of each two-position toggle switch is connected to the PZT sensor; the A-position terminal is connected to the input of the preamplifier to form a receiving path, and the B-position terminal is connected to the output of the power amplifier to form an excitation path. The output of the preamplifier is connected to the input of the acoustic emission acquisition instrument, which is used for multi-channel synchronous acquisition of time-domain signals for concrete structure monitoring. The power supply module is electrically connected to the preamplifier and the acoustic emission acquisition instrument.

[0006] Preferably, the n-channel transceiver switching control box, preamplifier, acoustic emission acquisition instrument, and power supply module are all integrated into the industrial control computer chassis. The connection between the A-position terminal of the n-channel transceiver switching control box and the input terminal of the preamplifier, and the connection between the output terminal of the preamplifier and the input terminal of the acoustic emission acquisition instrument, are all made within the industrial control computer chassis using short-distance shielded coaxial jumpers. The industrial control computer chassis panel is equipped with n PZT sensor interfaces, n channel indicator lights, a high-voltage excitation input interface for connecting the output terminal of the power amplifier, and n toggle switch handles for transceiver switching.

[0007] Preferably, the resonant frequency of the PZT sensor is 50-150kHz, and the excitation signal output by the signal generator is a tone burst signal modulated by a Hanning window with a center frequency matching the sensor frequency.

[0008] The present invention further provides a detection method based on the above-mentioned active-passive integrated concrete structure monitoring system, wherein the monitoring mode of the active-passive integrated concrete structure monitoring system includes passive acoustic emission monitoring and active wave scanning; The passive acoustic emission monitoring includes the following steps: switching all channels to the A position with the two-position toggle switch, so that all PZT sensors are connected to the receiving path. The PZT sensors sense the sound wave or vibration signal of the concrete structure, which is then introduced into the preamplifier through the n-channel transceiver switching control box to complete the signal amplification and conditioning. The acoustic emission acquisition instrument adopts a multi-channel independent threshold trigger mode to synchronously acquire acoustic emission events and records the arrival time, amplitude, ring count, duration, rise time and peak frequency characteristic parameters of each acoustic emission event in real time. The active wave scanning includes the following steps: Select one channel and switch the corresponding two-position toggle switch to position B, so that the PZT sensor of that channel is connected to the excitation path. The signal generator outputs an excitation signal, which is boosted by the power amplifier and drives the PZT sensor of that channel to generate a normal excitation stress wave on the surface of the concrete structure. The other PZT sensors remain in the receiving state. The received echo signal is conditioned by the preamplifier and then the time domain waveform is synchronously acquired by the acoustic emission acquisition instrument. The detection method includes the following steps: (1) Start the system and first perform an active wave scan. Extract the first wave amplitude, wavelet packet energy distribution, and first wave arrival time parameters from the active wave scan waveform data to establish the initial state baseline of the structure. (2) Perform passive acoustic emission monitoring, count the cumulative number of AE events from the passive acoustic emission monitoring data, fit the b-value based on the event amplitude distribution for damage warning, use the ratio of RA (Rise Amplitude, i.e. the ratio of the rise time to the amplitude of the acoustic emission event) to AF (Average Frequency, i.e. the ratio of the ringing count to the duration of the acoustic emission event) to classify tensile cracks and shear cracks, and use the time difference of arrival of multi-channel signals to solve the spatial coordinates of the crack source of the acoustic emission event; (3) Trigger active wave scanning. When the preset period arrives or when the AE signal is abnormal, trigger active wave scanning. Extract the first wave amplitude, wavelet packet energy distribution, and first wave arrival time parameters from the active wave scanning waveform data. Compare with the initial baseline and calculate the first wave amplitude attenuation rate, wavelet packet energy change rate, and wave velocity variation coefficient respectively. Use the above three indicators to jointly determine the location and degree of damage to the concrete structure. (4) The spatial matrix of the sensitive path of active damage index in active wave scanning is superimposed and compared with the location coordinates of passive acoustic emission events in passive acoustic emission monitoring in space to reduce misjudgment.

[0009] Preferably, the passive acoustic emission monitoring operates continuously for a long period of time, and the active fluctuation scan is triggered according to a preset cycle, or manually triggered after the passive acoustic emission monitoring detects an abnormal acoustic emission event.

[0010] Compared with the prior art, the present invention has the following advantages: (1) The present invention can use the same set of external PZT sensor arrays as both active excitation and passive acoustic emission reception, without the need for two independent sensor arrays. Active damage index and passive AE data can be directly compared and verified under the same sensor position and spatial coordinate system, eliminating the influence of sensitivity differences between different batches of sensors. (2) Hardware isolation between the receiving path and the excitation path is achieved through the two-position structure of the toggle switch. When the switch is in position A, the sensor is connected to the receiving path and the excitation path is physically disconnected. When it is in position B, the sensor is connected to the excitation path and the receiving path is physically disconnected. The high voltage side and the low voltage side do not rely on software protection, thus avoiding the hidden danger of high voltage crosstalk and low voltage preamplifier when sharing the sensor. (3) By integrating the sensor interface, transceiver switching, signal conditioning, data acquisition and power supply into one industrial control chassis, the field only needs to connect the sensor, excitation source and power supply to work. The preparation time is shortened from several hours in the traditional decentralized construction to several minutes, avoiding the risk of misplugging of manual wiring, and facilitating multiple deployments and rotation testing. (4) With an independent toggle switch set for each channel on the front panel, the operator can directly read whether each channel is in the receiving or excitation state. The switch position is indicated synchronously with the channel indicator light, without the need to confirm each channel through the host computer software or external instruments. (5) The system of the present invention is simple in principle and easy to operate. One system can cover both active inspection and passive monitoring needs. It is easy to carry and reuse, and has good versatility. Attached Figure Description

[0011] Figure 1 A schematic diagram of the overall structure of an integrated active and passive concrete structure monitoring system; Figure 2 A schematic diagram of the signal flow for a single channel in an n-channel transceiver switching control box; Figure 3 This is a flowchart of the detection method based on an integrated active and passive concrete structure monitoring system. Detailed Implementation

[0012] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0013] This invention provides an integrated active and passive concrete structure monitoring system and detection method.

[0014] 1. System Integration System structure composition reference Figure 1 and Figure 2The system consists of n external PZT sensors, a monitoring terminal, a signal generator, a power amplifier, and a host computer, where n is a positive integer not less than 2.

[0015] The monitoring terminal is housed in an industrial control chassis, which integrates an n-channel transceiver switching control box, an n-channel preamplifier, an acoustic emission acquisition instrument, and a 24V DC switching power supply. The front panel of the chassis exposes n PZT sensor interfaces and toggle switch handles for each channel, while the side panel features a high-voltage excitation input interface with a red-marked protective sleeve.

[0016] The externally mounted PZT sensor has a resonant frequency of 80kHz, a frequency range of 20-180kHz, a capacitance of approximately 120pF, a ceramic contact surface to ensure acoustic impedance matching with the concrete surface, a metal housing, and a 1.5m single-ended BNC connector with a side-outlet cable. The cable root is epoxy-encapsulated, and the protection rating is IP68. During use, the sensor is fixed to the concrete structure surface, and coupling agent is applied to the contact surface between the sensor and the concrete to eliminate air gaps at the interface.

[0017] The n-channel transceiver switching control box contains n independent two-position toggle switches. Each two-position toggle switch has a common terminal, an A-position terminal, and a B-position terminal. The common terminal is a moving contact, and the A-position and B-position terminals are two fixed stationary contacts, corresponding to two adjacent positions on the panel. When the toggle switch handle is turned to any position, the common terminal is only connected to the stationary contact corresponding to that position. Each PZT sensor is manually switched between receiving and excitation states via a two-position toggle switch: the common terminal of the switch connects to the PZT sensor interface; the A-position terminal connects to the preamplifier signal input, forming the receiving path; and the B-position terminal connects to the power amplifier output, forming the excitation path. At any given time, only one path can be connected by the two-position toggle switch. When in the A-position, the PZT sensor is connected to the receiving path, and the excitation path is physically disconnected; when in the B-position, the PZT sensor is connected to the excitation path, and the receiving path is physically disconnected. This achieves hardware-level isolation between the high-voltage excitation side and the low-voltage receiving side. The panels of the toggle switches for each channel are arranged in the same direction. Position A corresponds to the receiving position and position B corresponds to the excitation position. Operators can directly identify the current channel's access status by the position of the switch handle.

[0018] In receiving mode, signals from each channel are connected to the input of a preamplifier via a short-distance shielded coaxial jumper from the A position of a two-position toggle switch. After amplification and conditioning, the signals are connected to the corresponding input channel of the acoustic emission acquisition instrument. The entire receiving link is connected within the industrial control box. The acoustic emission acquisition instrument is configured with a multi-channel independent threshold trigger mode and a sampling rate of no less than 2MHz. The host computer communicates with the acoustic emission acquisition instrument for further processing and analysis of the acquired monitoring data.

[0019] In the excited state, the excitation signal generated by the signal generator enters the power amplifier for voltage boosting through the shielded coaxial cable. The boosted high-voltage excitation signal is then connected to the high-voltage excitation input interface on the side panel of the industrial control computer box through the shielded coaxial cable. Through the B position of the two-position toggle switch, the PZT sensor is driven to emit a normal excitation stress wave towards the surface of the concrete structure.

[0020] 2. Sensor Installation and Deployment The n-channel external PZT sensors are flexibly arranged on the surface of the concrete structure according to the geometric characteristics of the monitored object and the expected damage area. The BNC connectors of the sensors are connected to the PZT sensor interface of the industrial control computer box.

[0021] 3. Passive acoustic emission monitoring All channels are switched to the default A position using the two-position toggle switch, connecting the n PZT sensors to the receiving path. The data acquisition instrument operates continuously in a multi-channel independent threshold trigger mode. When microcracks develop in the concrete structure under the cyclic load of the operating railway, elastic waves are released. If any channel signal exceeds the preset threshold value, the full waveform and characteristic parameters of the acoustic emission event are automatically recorded, including arrival time, amplitude, ring count, duration, rise time, and peak frequency. The passive acoustic emission monitoring mode operates continuously around the clock, capturing acoustic emission signals generated by the structure under operating loads in real time.

[0022] 4. Active fluctuation scan Active fluctuation scanning is triggered at a preset cycle or manually after abnormal acoustic emission activity is detected by passive acoustic emission monitoring. The signal generator outputs a Hanning window modulated sine wave, which is boosted by a power amplifier to drive the selected sensor. Channels 1 to n are switched to the excitation position in sequence, and the time-domain waveforms of the other n-1 channels are received synchronously during each channel excitation. After n rounds of scanning are completed, all toggle switches are returned to the receive position, and the system automatically returns to passive monitoring mode.

[0023] 5. Testing methods like Figure 3 As shown, the detection method based on the above-mentioned integrated active and passive concrete structure monitoring system specifically includes the following steps: (1) Start the system and first perform an active wave scan. Extract the first wave amplitude, wavelet packet energy distribution, and first wave arrival time parameters from the active wave scan waveform data to establish the initial state baseline of the structure. (2) Perform passive acoustic emission monitoring, count the cumulative number of AE events from the passive acoustic emission monitoring data, perform damage early warning based on the b-value fitting of the event amplitude distribution, classify tensile cracks and shear cracks using the ratio of RA to AF, and solve the crack source spatial coordinates of acoustic emission events using the time difference of arrival of multi-channel signals. (3) Trigger active wave scanning. When the preset period arrives or when the AE signal is abnormal, trigger active wave scanning. Extract the first wave amplitude, wavelet packet energy distribution, and first wave arrival time parameters from the active wave scanning waveform data. Compare with the initial baseline and calculate the first wave amplitude attenuation rate, wavelet packet energy change rate, and wave velocity variation coefficient respectively. Use the above three indicators to jointly determine the location and degree of damage to the concrete structure. (4) The spatial matrix of the sensitive path of active damage index in active wave scanning is superimposed and compared with the location coordinates of passive acoustic emission events in passive acoustic emission monitoring in space to reduce misjudgment.

[0024] 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 and improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An integrated active and passive concrete structure monitoring system, characterized in that, The system includes n externally mounted PZT sensors, an n-channel transceiver switching control box, a preamplifier, an acoustic emission acquisition unit, a signal generator, a power amplifier, and a power supply module. The PZT sensors are fixed to the surface of a concrete structure to passively receive acoustic signals or actively emit excitation signals. The output of the signal generator is connected to the input of the power amplifier; the signal generator outputs an excitation signal, which is boosted by the power amplifier to drive the selected PZT sensor. The n-channel transceiver switching control box includes n independent two-position toggle switches, used to independently control the n PZT sensors to switch between receiving and excitation states. The common terminal of each two-position toggle switch is connected to the PZT sensor; the A-position terminal is connected to the input of the preamplifier to form a receiving path, and the B-position terminal is connected to the output of the power amplifier to form an excitation path. The output of the preamplifier is connected to the input of the acoustic emission acquisition instrument, which is used for multi-channel synchronous acquisition of time-domain signals for monitoring concrete structures; the power supply module is electrically connected to the preamplifier and the acoustic emission acquisition instrument.

2. The integrated active and passive concrete structure monitoring system according to claim 1, characterized in that, The n-channel transceiver switching control box, preamplifier, acoustic emission acquisition instrument, and power supply module are all integrated into the industrial control computer chassis. The A-position terminal of the n-channel transceiver switching control box to the input terminal of the preamplifier and the output terminal of the preamplifier to the input terminal of the acoustic emission acquisition instrument are all connected in the industrial control computer chassis using short-distance shielded coaxial jumpers. The industrial control computer chassis panel is equipped with n PZT sensor interfaces, n channel indicator lights, a high-voltage excitation input interface for connecting the output terminal of the power amplifier, and n toggle switch handles for transceiver switching.

3. The integrated active and passive concrete structure monitoring system according to claim 1, characterized in that, The resonant frequency of the PZT sensor is 50-150kHz, and the excitation signal output by the signal generator is a tone burst signal modulated by a Hanning window with a center frequency matching the sensor frequency.

4. A detection method based on the integrated active and passive concrete structure monitoring system according to any one of claims 1-3, characterized in that, The monitoring modes of the integrated active and passive concrete structure monitoring system include passive acoustic emission monitoring and active wave scanning. The passive acoustic emission monitoring includes the following steps: switching all channels to the A position with the two-position toggle switch, so that all PZT sensors are connected to the receiving path. The PZT sensors sense the sound wave or vibration signal of the concrete structure, which is then introduced into the preamplifier through the n-channel transceiver switching control box to complete the signal amplification and conditioning. The acoustic emission acquisition instrument adopts a multi-channel independent threshold trigger mode to synchronously acquire acoustic emission events and records the arrival time, amplitude, ring count, duration, rise time and peak frequency characteristic parameters of each acoustic emission event in real time. The active wave scanning includes the following steps: Select one channel and switch the corresponding two-position toggle switch to position B, so that the PZT sensor of that channel is connected to the excitation path. The signal generator outputs an excitation signal, which is boosted by the power amplifier and drives the PZT sensor of that channel to generate a normal excitation stress wave on the surface of the concrete structure. The other PZT sensors remain in the receiving state. The received echo signal is conditioned by the preamplifier and then the time domain waveform is synchronously acquired by the acoustic emission acquisition instrument. The detection method includes the following steps: (1) Start the system and first perform an active wave scan. Extract the first wave amplitude, wavelet packet energy distribution, and first wave arrival time parameters from the active wave scan waveform data to establish the initial state baseline of the structure. (2) Perform passive acoustic emission monitoring, count the cumulative number of AE events from the passive acoustic emission monitoring data, perform damage early warning based on the b-value fitting of the event amplitude distribution, classify tensile cracks and shear cracks using the ratio of RA to AF, and solve the crack source spatial coordinates of acoustic emission events using the time difference of arrival of multi-channel signals. (3) Trigger active wave scanning. When the preset period arrives or when the AE signal is abnormal, trigger active wave scanning. Extract the first wave amplitude, wavelet packet energy distribution, and first wave arrival time parameters from the active wave scanning waveform data. Compare with the initial baseline and calculate the first wave amplitude attenuation rate, wavelet packet energy change rate, and wave velocity variation coefficient respectively. Use the above three indicators to jointly determine the location and degree of damage to the concrete structure. (4) The spatial matrix of the sensitive path of active damage index in active wave scanning is superimposed and compared with the location coordinates of passive acoustic emission events in passive acoustic emission monitoring in space to reduce misjudgment.

5. The detection method of the integrated active and passive concrete structure monitoring system according to claim 4, characterized in that, The passive acoustic emission monitoring operates continuously over a long period of time, and the active fluctuation scan is triggered according to a preset cycle, or manually triggered after the passive acoustic emission monitoring captures an abnormal acoustic emission event.

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