A detection system and method for the grouting density of prestressed ducts of bridges

Abstract

The present invention provides a detection system and a detection method for the grouting density of bridge prestressed ducts. The system includes two acquisition devices with the same configuration, and each acquisition device corresponds to an acceleration sensor; each acquisition device includes a time synchronization unit, a network communication unit, a signal input module, and a control unit. The time synchronization unit is used to provide timestamp information, and the network communication unit is used to provide wireless communication; the signal input module is used to obtain the signal of the acceleration sensor and preprocess it to obtain sampling data, and the control unit is used to store the sampling data and calculate the first-wave time difference of the test waveforms of the two acquisition devices according to the sampling data and timestamp information of the two acquisition devices. By separately collecting nearby and wirelessly communicating through two sets of acquisition devices, and combining with a high-precision timestamp module to ensure the signal pickup accuracy, the present invention avoids the deficiencies of conventional duct grouting density detection devices and improves the applicability and convenience of the duct grouting density detection device.

Description

Technical Field

[0001] The present invention belongs to the technical field of engineering construction quality inspection, and particularly relates to a detection system and a detection method for the grouting density of bridge prestressed ducts. Background Art

[0002] With the rapid development of China's road and bridge industry, prestressed concrete structures are widely used in engineering construction to make up for the deficiency of their tensile strength by means of the high compressive strength of concrete, so as to achieve the purpose of delaying the cracking of concrete in the tensile zone. If the grouting is not dense, the entry of water and air makes the prestressed tendons in a highly tensioned state prone to corrosion, resulting in the phenomenon of reduced effective prestress. Seriously, the prestressed tendons will break, thus greatly affecting the durability and safety of the bridge. In addition, the quality defects of grouting will also lead to the stress concentration of concrete, and then change the designed stress state of the beam body, thus affecting the bearing capacity and service life of prestressed concrete bridges. Therefore, the quality of duct grouting directly affects the safety and durability of prestressed concrete structures, and is of great significance to the overall safety and service life of prestressed bridges. In order to better control the quality of duct grouting, it is an indispensable link to have professional personnel test and detect it with scientific methods and means.

[0003] The duct grouting quality detector is based on the basic principle of elastic wave detection technology. The elastic wave generated by excitation forms an external disturbance to the anchor cable during the propagation along the anchor cable. Under the action of this disturbance, the anchor cable will generate corresponding vibrations. The frequency of its vibration depends on two aspects, namely the frequency of the disturbing force and the natural frequency of the anchor cable. Among them, the frequency of the disturbing force is related to the excitation signal and can be obtained from the signal picked up by the sensor near the excitation point. The natural frequency of the anchor cable depends on the tension, cross-sectional area, length and linear density of the anchor cable. When the duct grouting is not dense, there are cavities or the grouting material has not yet cured, it is equivalent to the anchor cable hanging in the air at both ends, and the anchor cable can be simplified into a string fixed at both ends. It is easy to imagine that the natural vibration frequency of the string at this time is generally high. On the other hand, when the grouting is dense and has cured, the outside of the anchor cable is wrapped with grouting material. This is equivalent to an increase in the cross-sectional area of the string, and then the natural vibration frequency of the anchor cable is reduced. Therefore, by analyzing the natural vibration frequency and excitation frequency of the anchor cable, the grouting density of this part of the anchor cable can be measured.

[0004] Basic Principle: The duct grouting quality detector has two functional modes: qualitative detection and positioning detection. Qualitative detection adopts a dual-channel test mode, and uses the full-length wave velocity method (FLPV), the full-length attenuation method (FLEA) and the transfer function method (FLTF) to quickly conduct qualitative detection and evaluation of the duct, and preliminarily determine the grouting density of the duct; positioning detection adopts the impact echo equivalent wave velocity method (IEEV) to conduct positioning analysis on the defect location.

[0005] Components: A duct grouting quality detector generally consists of an acceleration sensor, a magnetic holder, a sensor lead wire, an excitation device, and a main unit. There are two acceleration sensors. During testing, they are respectively fixed to both ends of the exposed anchor cable outside the duct to be measured with the help of magnetic holders. They are used to pick up the original excitation signal and the signal transmitted to the other end along the anchor cable when the original excitation signal reaches the other end. The magnetic holder is mainly used to fix the acceleration sensor to the anchor cable to be measured. The sensor lead wire is mainly used to connect the two acceleration sensors to the main unit in a wired manner, that is, the sensor transmits the collected signal to the main unit through a wired method for processing. The excitation device generally includes a hammer, an excitation cone or an automatic excitation device, which is used to excite the anchor cable in the duct to be measured and generate elastic waves. The two acceleration sensors respectively pick up the original excited elastic wave and the elastic wave transmitted to the other end of the anchor cable. The main unit is used to collect and display the signal output waveforms of the two acceleration sensors, and analyze the two waveforms in combination with relevant algorithms, and finally realize the non-destructive detection of the grouting density of the duct to be measured.

[0006] Connection method: During testing, the main unit is connected to the two acceleration sensors in a wired manner.

[0007] Implementation method: During qualitative testing, the two acceleration sensors are respectively fixed to the head and tail ends of the exposed anchor cable outside the duct to be measured with magnetic holders. The main unit collects and circularly stores the signals of the two acceleration sensors in real time. When knocking on any end of the exposed anchor cable, when the trigger condition is reached, the main unit respectively records the data of a fixed length for the two acceleration sensors starting from the trigger moment. By analyzing the changes in characteristics such as energy, frequency, and wave velocity when the signal collected by the sensor propagates in the detection object, a detection method for qualitatively determining the grouting density of the bridge prestressed duct is realized. The positioning detection is based on the impact echo method (IE method), and the position, scale, etc. of the grouting defect are tested by exciting through the side wall or the top (bottom) surface and receiving with a single acceleration sensor.

[0008] The existing methods have the following deficiencies during qualitative detection:

[0009] 1. The qualitative detection of duct grouting density generally uses a wired test method, which requires connecting two sensors to the data acquisition device in a wired manner. During testing, cables need to be laid on site. Since the length of the beam slab ranges from more than ten meters to dozens of meters or even more than one hundred meters, in order to be compatible with various different sites, generally longer cables are required, and for some cast-in-place beams, there may be situations where high-altitude operations are required. Using a wired method is not conducive to the carrying of the equipment, and at the same time increases the workload and complexity of cable laying on site;

[0010] 2. When testing using a wired method, because the cable is generally long, the actual test faces the problems of signal interference and signal loss caused by the cable. As the cable length increases, the signal will experience varying degrees of attenuation and electromagnetic interference during transmission. These problems will directly affect the final received signal quality and the overall performance of the system, thereby affecting the accuracy of the test;

[0011] 3. During testing, sensors must be installed at both ends of the same channel to be tested in the beam and slab. This is typically done by two staff members on-site. The test sequence must be agreed upon beforehand, and each channel of the beam and slab must be tested sequentially. When the current channel is tested and the next channel is switched, the sensor must be moved to the next channel. At this point, both sensors must be installed on the new channel. Because the two staff members are separated by a distance and cannot directly access each other's sensor installation status, on-site communication often requires telephones, intercoms, and other devices, which reduces testing efficiency. Summary of the Invention

[0012] In order to overcome the shortcomings of the above-mentioned prior art, the present invention provides a bridge prestressed duct grouting density detection system and detection method. Through two sets of acquisition equipment to collect data nearby and communicate wirelessly, combined with a high-precision timestamp module to ensure signal pickup accuracy, the shortcomings of conventional duct grouting density detection devices are avoided, and the applicability and convenience of the duct grouting density detection device are improved.

[0013] According to one aspect of the present invention, a bridge prestressed duct grouting density detection system is provided, comprising two acquisition devices with the same configuration, each of which corresponds to an acceleration sensor; each of the acquisition devices comprises a time synchronization unit, a network communication unit, a signal input module and a control unit, the time synchronization unit is used to provide timestamp information, and the network communication unit is used to provide wireless communication; the signal input module is used to acquire the signal of the acceleration sensor and preprocess it to obtain sampling data, the control unit is used to store the sampling data, and calculate the first wave time difference of the test waveforms of the two acquisition devices based on the sampling data and timestamp information of the two acquisition devices.

[0014] As a further technical solution, the signal input module includes a signal interface unit, a signal conditioning unit and a signal acquisition unit. The signal interface unit is used to connect to the acceleration sensor, the signal conditioning unit is used to preprocess the connected signal, and the signal acquisition unit is used to convert the preprocessed signal and output it to the control unit.

[0015] As a further technical solution, the control unit is further connected to a display unit for displaying sampling data and setting sampling parameters.

[0016] As a further technical solution, the control unit is further connected with a voice unit for voice prompt.

[0017] As a further technical solution, the control unit includes a storage sub-unit and an analysis sub-unit. The storage sub-unit is used to cyclically overwrite and store the sampling data according to a set length. The analysis sub-unit is used to control the time synchronization unit to record the acquisition time and the trigger time, control the network communication unit to send the acquisition instruction and the trigger instruction to the slave machine, and determine the first wave time coordinate positions of the master machine and the slave machine according to the sampling data of both the master machine and the slave machine in combination with the timestamp information.

[0018] As a further technical solution, the storage sub-units of the two acquisition devices sample in real time according to a set length and cyclically overwrite and store the sampling data, and the cyclically overwritten storage area is at least greater than twice the single data sampling length.

[0019] According to one aspect of the specification of the present invention, a method for detecting the grouting density of a bridge prestressed duct is provided. An acquisition device with the same configuration is respectively arranged at both ends of the beam body. The acquisition device close to the knocking end is used as the master machine, and the acquisition device at the other end is used as the slave machine. The method includes:

[0020] When the master machine starts to acquire, record the acquisition time of the master machine and send the acquisition time of the master machine to the slave machine, and simultaneously cyclically store the sampling values in real time;

[0021] When the slave machine receives the acquisition time of the master machine, record the acquisition time of the slave machine, and simultaneously cyclically store the sampling values in real time;

[0022] When the master machine reaches the trigger level and starts to trigger, record the trigger time of the master machine and send the trigger time of the master machine to the slave machine;

[0023] When the slave machine receives the trigger time of the master machine, record the trigger time of the slave machine;

[0024] Determine the time difference between the two test waveforms according to the acquisition time of the master machine, the acquisition time of the slave machine, the trigger time of the master machine and the trigger time of the slave machine;

[0025] When the current measurement point ends, intercept the waveforms from the stored data of the master machine and the slave machine respectively, display them on the same time coordinate axis, and perform translation in combination with the time difference to determine the first wave time coordinate positions of the knocking waveform reaching the master machine and the slave machine.

[0026] As a further technical solution, the method further includes:

[0027] According to the first wave time coordinate positions of the knocking waveform reaching the master machine and the slave machine, determine the measured wave velocity of the duct according to the full-length wave velocity method, and determine the grouting density of the duct according to the measured wave velocity.

[0028] As a further technical solution, the method further includes:

[0029] Determine the total number of measuring points to be tested based on the total number of exposed anchors from top to bottom of the beam to be tested;

[0030] All measurement points are numbered and displayed on the master and slave devices respectively;

[0031] All measuring points are tested one by one, and the test data of all measuring points are integrated to obtain the hole grouting density test results of the current beam to be tested.

[0032] As a further technical solution, the translation is performed in combination with the time difference, including:

[0033] According to the time difference and the sampling interval, the number of sampling points that the slave waveform needs to be shifted is obtained;

[0034] The waveform of the slave device is shifted according to the number of sampling points so that the waveforms of the master device and the slave device are recorded from the same starting time.

[0035] Compared with the prior art, the present invention has the following beneficial effects:

[0036] The present invention discloses a device for detecting the density of grouting of prestressed ducts of bridges. The device collects data from two acceleration sensors separately through two acquisition devices. By adopting a wireless acquisition mode, the sensors can be directly installed at the target location without the need for additional communication cables, eliminating the need for long-distance cables and reducing the workload and complexity of on-site deployment. This not only simplifies the carrying and installation process of the equipment, but also avoids safety risks in special scenarios. At the same time, the wireless synchronization solution effectively overcomes the problem of signal attenuation over long distances, ensuring that the effective signal can be accurately picked up by the detection device, while reducing noise crosstalk in long-distance transmission, improving the quality of collected data, and being able to provide stable and reliable measurement results in a wider range of environments, ensuring the accuracy and reliability of the test. In addition, it allows the display unit and voice prompt unit to confirm whether the two acceleration sensors are located at the same anchor position to be tested without manual intervention, thereby significantly improving the detection efficiency. The device for detecting the density of grouting of prestressed ducts of bridges of the present invention avoids the shortcomings of conventional duct grouting density detection devices and improves the applicability and convenience of duct grouting density detection devices.

[0037] The present invention discloses a method for detecting the grouting density of prestressed ducts of bridges. When the host starts to collect and trigger, it notifies the slave to start collecting and triggering in a wireless manner, achieving accurate marking of the collection time and triggering time of the slave, avoiding the problems of the slave being unable to trigger or mis-triggering, and through accurate time marking, when intercepting and translating data, it can accurately judge the time difference when the percussion waveform reaches the two acceleration sensors, thereby ensuring the accuracy of the qualitative analysis of the grouting density of the duct based on this time difference.

[0038] The present invention samples two acquisition devices in real time according to a set length and stores the sampled data in a cyclic covering manner. The cyclic covering storage area is at least greater than twice the single data sampling length, solving the problem of limited data storage space on the premise of ensuring that valid data will not be lost during subsequent data shifting and interception.

[0039] In summary, the grouting density detection device and method for prestressed ducts of bridges of the present invention comprehensively solve the deficiencies existing in traditional detection means by integrating multiple advanced technologies such as wireless communication, high-precision time synchronization, and intelligent data management, and greatly improve the applicability, convenience, and accuracy of the grouting density detection work of ducts. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings used in the description of the embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0041] Figure 1 It is a schematic diagram of a grouting density detection system for prestressed ducts of bridges provided by an embodiment of the present invention.

[0042] Figure 2 It is a schematic diagram of the principle of the acquisition device provided by an embodiment of the present invention.

[0043] Figure 3 It is a schematic diagram of the principle of the signal conditioning unit provided by an embodiment of the present invention.

[0044] Figure 4 It is a schematic diagram of the principle of the floating-point amplification module provided by an embodiment of the present invention.

[0045] Figure 5 It is a schematic diagram of the principle of the time synchronization unit provided by an embodiment of the present invention.

[0046] Figure 6 It is a schematic diagram of the principle of the network communication unit provided by an embodiment of the present invention.

[0047] Figure 7 Schematic diagram of the full-length wave velocity method provided by the embodiment of the present invention.

[0048] Figure 8 Schematic diagram of intercepting and translation provided by the embodiment of the present invention. Detailed implementation manners

[0049] It should be noted that:

[0050] In view of the current situation that a data acquisition device is configured in the prior art and both two-channel acceleration sensors need to be connected to the data acquisition device by wire, the present invention separately collects the two-channel acceleration sensors, that is, two sets of acquisition devices are respectively placed near the two-channel sensors at the head and tail of the to-be-tested beam body, and communicate through a wireless manner, avoiding the inconvenience caused by on-site pre-wiring and long-distance lead wires during field change.

[0051] In view of the current situation that the existing wired test method has poor signal pickup effect due to too long cables, the present invention configures two sets of acquisition devices to respectively collect the two-channel acceleration sensors. The distance from the acceleration sensors to the acquisition devices is short and close to the connection, and there is no problem of signal attenuation and inability to pick up effective signals or long-distance transmission noise crosstalk.

[0052] In view of the current situation that in the prior art, when changing the measurement points, the two-channel acceleration sensors are not on the same to-be-tested anchor, the present invention configures a screen display function in both two sets of acquisition devices. Before the test, only need to input the to-be-tested measurement point number in any one of the acquisition devices according to the number of exposed anchors of the to-be-tested beam body, and the two sets of acquisition devices synchronously generate a schematic diagram of the measurement points. When one acquisition device selects the current test measurement point, the measurement point on the screen of the other acquisition device is selected and a voice prompt is given, thus avoiding the problem that the two-channel acceleration sensors are not on the same to-be-tested anchor.

[0053] In view of the synchronous acquisition problem under the uncertain trigger time of the two sets of acquisition devices in the wireless solution, the present invention introduces a high-precision time stamp module and a long-distance wireless communication module. When the host starts to collect and trigger, it uses a wireless manner to inform the slave to start collecting and triggering, realizing the accurate marking of the slave's collection time and trigger time, realizing the ns-level time synchronous acquisition of the two sets of devices, and improving the difference precision of the signal pickup of the two-channel sensors.

[0054] In view of the problem of limited storage space in the wireless solution, the present invention samples the two sets of acquisition devices in real time according to the set length and stores the sampled data in a cyclic coverage manner. On the premise of ensuring that the subsequent data shift and interception will not lose effective data, the problem of limited data storage space is solved.

[0055] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are some, but not all, of the embodiments of the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention. In addition, the technical features in each embodiment or individual embodiment provided by the present invention can be arbitrarily combined with each other to form a new technical solution. Such combination is not restricted by the order of steps and / or the mode of structural composition, but must be based on what can be achieved by those of ordinary skill in the art. When the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the protection scope required by the present invention.

[0056] Please refer to Figure 1 , an embodiment of the present invention provides a detection system for the grouting density of bridge prestressed ducts, which includes two acquisition devices with the same parameters. The two acquisition devices are respectively arranged at both ends of the beam body and are wirelessly connected to each other. Each acquisition device is connected to an acceleration sensor. During detection, the acquisition device close to the knocking end is defined as the host, and the acquisition device far from the knocking end is defined as the slave. The slave is marked for the start time and trigger time of acquisition by sending an instruction from the host. When the data acquisition ends, according to the sampling data of the host and the slave and in combination with the timestamp information of both, the time difference between the two test waveforms of the host and the slave is obtained. According to the time difference, the measured wave velocity is obtained, and then the detection result of the grouting density of the duct is obtained based on the wave velocity.

[0057] Please refer to Figure 2 , each acquisition device respectively includes a signal interface unit IU, a signal conditioning unit CU, a signal acquisition unit SU, an ARM control unit MU, a time synchronization unit TU, a network communication unit NU, a display unit DU, and a voice unit VU. The signal interface unit IU is connected to the signal conditioning unit CU. The signal conditioning unit CU is further connected to the signal acquisition unit SU. The signal acquisition unit SU is further connected to the ARM control unit MU. The ARM control unit MU is respectively connected to the signal acquisition unit SU, the time synchronization unit TU, the network communication unit NU, the display unit DU, and the voice unit VU.

[0058] Specifically, the signal interface unit IU adopts a 4-core ODU connector, which can facilitate the quick access of the acceleration sensor AS, facilitate the acquisition of sensor signals by the detection system, and at the same time has the function of hot plug protection for the acceleration sensor.

[0059] Please refer to Figure 3, the signal conditioning unit CU includes a programmable band-pass filter module PM, a floating-point amplification module AM, and a single-ended to differential module CM. The programmable band-pass filter module PM is used to filter the input signal of the acceleration sensor AS. According to the center frequency point of the acceleration sensor AS and the bandwidth range of the effective signal, the band-pass filtering range is reasonably set to facilitate the pickup of the effective signal. The floating-point amplification module AM is used to reasonably amplify the effective signal output by the programmable band-pass filter module PM. While meeting the dynamic range requirements of this detection, the received signal is adjusted to the optimal input range of the subsequent signal acquisition unit SU, thereby improving the overall signal-to-noise ratio of the signal to be collected. The single-ended to differential module CM is used to convert the single-ended signal output by the floating-point amplification module AM into a differential signal, improving the anti-interference ability and stability of the signal to be collected.

[0060] Specifically, the programmable band-pass filter module PM selects the LTC1068 active filter of ADI Corporation, and adjusts the center frequency point and bandwidth of the band-pass filter by adjusting the values of the peripheral resistors and capacitors.

[0061] Please refer to Figure 4 , the floating-point amplification module AM consists of a window comparator WC, a reference voltage VF, and an instrumentation amplifier IA. The window comparator WC integrates multiple groups of input comparison ports. One group of input ports contains two input pins, forming one output signal. During actual testing, the reference voltage VF outputs several levels of reference voltage sources, which are respectively connected to the corresponding input pins of multiple groups of input ports of the window comparator WC according to the design requirements. The effective signal output by the programmable band-pass filter module PM is also connected to the corresponding input pins of multiple groups of input ports of the window comparator WC according to the design requirements, that is, the effective signal is simultaneously compared with voltage sources of different levels respectively. The multiple output pins of the window comparator WC will also output corresponding high and low level signals according to the comparison results. The output high and low level signals are connected to the instrumentation amplifier IA to achieve reasonable amplification of effective signals of different amplitudes, facilitating the effective acquisition of the signal acquisition unit SU.

[0062] Specifically, the window comparator WC selects the four-channel differential comparator LM339 of TI Corporation, which can compare four groups of input voltages in real time and output high and low level signals according to the comparison results, and connect them to the programmable amplification pins of the instrumentation amplifier IA. The reference voltage VF selects the four-channel operational amplifier LF347 of TI Corporation. By matching different resistor values, four reference sources can be provided to access the window comparator WC for comparison. The instrumentation amplifier IA selects the programmable instrumentation amplifier AD8253 of ADI Corporation, and reasonably amplifies the sensor signal according to the comparison results output by the window comparator WC.

[0063] The signal acquisition unit SU is used to acquire the signals processed by the programmable band-pass filter module PM, the floating-point amplification module AM, and the single-ended to differential module CM, and convert the analog signals into digital signals for the ARM control unit MU to perform digital signal processing.

[0064] Specifically, the signal acquisition unit SU selects the analog-to-digital converter LTC2389 of ADI Company, with a sampling rate of up to 2.5M, meeting the requirements of high-precision real-time sampling.

[0065] Based on the timestamp information output by the time synchronization unit TU and combining relevant algorithms, the ARM control unit MU processes the digital signals output by the signal acquisition unit SU, displays them on the display unit DU, communicates with another duct grouting acquisition device through the network communication unit NU, and uses the voice unit VU to guide the operator for corresponding prompts, finally completing the entire test process.

[0066] Specifically, the ARM control unit MU selects the high-performance ZYNQ-7000 processor of Xilinx Company, which combines an ARM processor and an FPGA processor internally. The ARM processor is used for information interaction, outputs a pulse signal to the time synchronization unit TU, and obtains the timestamp information at the trigger moment; it is connected to the display unit DU through a bus interface for users to set acquisition parameters and display sampling waveforms; it is connected to the network communication unit NU through an SPI interface for wireless communication. The FPGA processor is used to control the sampling timing of the signal acquisition unit SU, and at the same time reads the sampling data in real time and stores it cyclically in the internal SRAM.

[0067] Please refer to Figure 5 , the time synchronization unit TU has an event trigger function and can output high-precision timestamp information, facilitating the ARM control unit MU to process the acquired signals. The time synchronization unit TU includes a high-precision timestamp module TM and an antenna ANT1. The high-precision timestamp module TM has an event trigger function. The ARM control unit MU outputs a single pulse signal to the high-precision timestamp module TM, and the high-precision timestamp module TM can mark the rising edge moment of the trigger pulse and output high-precision timestamp information. The antenna ANT1 is used to receive satellite signals.

[0068] Specifically, the time synchronization unit TU selects a high-precision GPS module with an event trigger function from Xi'an Synchronization Electronics Technology Co., Ltd., which can output timestamp information at the ns level.

[0069] Please refer to Figure 6The network communication unit NU mainly realizes the information interaction between the two duct grouting collection devices in the wireless communication working mode. The network communication unit NU includes a wireless communication module WM and an antenna ANT2. The wireless communication module WM is a dual-frequency long-distance wireless communication module that can meet the large-span wireless communication requirements of the two duct grouting detection devices. The antenna ANT2 is used for sending and receiving wireless signals.

[0070] Specifically, the network communication unit NU uses a high-power wireless communication module in the 5.8G frequency band, supports AP mode, client mode, relay and routing mode, and can meet long-distance communication needs.

[0071] The display unit DU includes a human-computer interaction interface with integrated touch and display. The display unit DU can be used to set relevant parameters, switch collection status, link the current measurement points of the two channel grouting collection devices at both ends of the channel to be measured, and display real-time sampling data and analysis results.

[0072] Specifically, the display unit DU uses a 6-inch touch screen to display the sampling data, and the user can set the sampling parameters through the display unit DU.

[0073] The voice unit VU is mainly used to prompt various states during the acquisition process. At the same time, when retesting or changing the next test point, it guides the operators at both ends of the channel to perform the corresponding operations correctly to ensure the smooth progress of the detection process.

[0074] Specifically, the voice unit VU uses the SYN6658 Chinese speech synthesis chip from Beijing Yuyintianxia Technology Co., Ltd., which is connected to the ARM control unit MU through the serial port to convert the voice text to be broadcast into corresponding characters. In actual use, the ARM control unit MU writes the corresponding characters through the serial port to prompt the user.

[0075] The embodiment of the present invention provides a bridge prestressed duct grouting density detection system, which is implemented as follows:

[0076] During qualitative testing, two acquisition devices DT1 and DT2 are placed at both ends of the beam to be tested respectively. Based on the total number of exposed anchors from top to bottom of the beam to be tested, the total number of measuring points to be tested is input into any one of the acquisition devices. The two acquisition devices are linked to each other through the network communication unit NU, that is, a measuring point schematic diagram is formed on each display unit DU, and the measuring points are numbered in sequence from top to bottom.

[0077] Since either end can be used as the trigger end, during detection, the acquisition device closer to the end being struck is defined as the host, and the acquisition device farther from the end being struck is defined as the slave. On the host, the current test point number to be measured is selected through the display unit DU. The same test point will also be synchronously selected on the display unit DU of the slave, and a prompt will be given through the voice unit VU. The two acceleration sensors AS are respectively installed on the currently selected test point to be measured. After the test is completed by striking at one end, the other end of the current test point can be struck again for remeasurement and comparison to ensure the accuracy of the test data.

[0078] When starting the test, click the start sampling button on the host through the display unit DU, and link with the slave through the network communication unit NU. The slave also performs the sampling operation. The duration from the start of sampling to triggering is uncertain, and the device needs the data in the previous part of the triggering moment during subsequent data processing. Therefore, the acquisition device needs to store the sampling data from the start of acquisition. However, since the data storage space is limited, the two acquisition devices sample in real time according to the set length and circularly overwrite and store the sampling data. The circular overwrite storage area is at least greater than twice the single data sampling length to ensure that valid data will not be lost during subsequent data shifting and interception.

[0079] When the host starts to acquire, the host gives a pulse signal to the time synchronization unit TU to record the current moment, defined as T A0 , and notifies the slave to start acquisition in a wireless manner. When the slave receives the start acquisition instruction, it gives a trigger signal to the internal time synchronization unit TU to record the slave start acquisition moment T B0 , and circularly stores the sampling values in real time.

[0080] The test point to be measured is struck by the excitation hammer EH and the excitation cone EC. When the trigger level is reached, the host starts to trigger and gives a pulse signal to the internal time synchronization unit TU to record the current trigger moment, defined as T A1 , and notifies the slave to start triggering in a wireless manner. When the slave receives the start triggering instruction, it gives a trigger signal to the internal time synchronization unit TU to record the slave start triggering moment T B1 . In the same time coordinate axis, the time difference between the two test waveforms is |T B1 - T A1 | - |T B0 - T A0 |. Substantially, in two different storage areas, a section of waveform is respectively intercepted and displayed on the same time coordinate axis. The time synchronization unit TU provides the time base for data interception and translation.

[0081] After collecting the data of the set number of points, the slave machine uploads the sampled data to the host machine. Since the sampling intervals and the number of points sampled per time for the host machine and the slave machine are the same, the host machine multiplies the sampling interval by the number of sampling points and uses the method of data interception and translation to record the two sampling signals starting from the same time point. When on the host machine's acquisition interface, two waveforms can be displayed on the same time axis. By using the method of software first-wave judgment, the time coordinate positions of the first waves of the knocking waveforms reaching the host machine and the slave machine can be determined respectively, denoted as T ch1 and T ch2 , and through this time difference, qualitative analysis of the grouting density of the measured hole can be realized. For the translation schematic diagram, please refer to Figure 8 .

[0082] It should be noted that in the above text, when the host machine triggers, the slave machine is informed to start triggering via wireless means, that is, marking the position of the current data point. This is because if the slave machine relies on the trigger level to trigger, due to the differences in the length and density of the measured hole, the trigger level of the slave machine cannot be set correctly. If the trigger level is too high, the slave machine cannot trigger; if it is too low, there will be false triggering. However, when the host machine triggers and informs the slave machine to start triggering for marking, this problem can be avoided. Subsequently, through time difference translation, the time difference of the knocking waveform reaching the two acceleration sensors AS can be accurately judged, and qualitative analysis of the grouting density of the measured hole can be realized through this time difference.

[0083] The specific calculation method for qualitative analysis of the grouting density of the measured hole is as follows:

[0084] According to the propagation law of elastic waves in the medium, the wave velocity, energy attenuation rate, frequency change, etc. during propagation are closely related to the properties of the medium. Generally speaking, the stronger and denser the medium, the more conducive it is to the propagation of elastic waves, and the higher the wave velocity during the propagation process. When detecting the quality of hole grouting, whether the grouting is full has a relatively obvious impact on the wave velocity of elastic wave propagation. Generally, the propagation speed of elastic waves in the steel strand is about 5.01 km / s, and in concrete it is about 4.0 km / s. The actually measured wave velocity of the hole is between the two. Please refer to Figure 7 . When the hole grouting is full, the grouting density is high and the wave velocity is closer to the concrete wave velocity. When the hole grouting is not full, the grouting density is low and the wave velocity is closer to the wave velocity of the steel strand, approximately in direct proportion. According to this rule, the grouting density of the hole can be calculated through the wave velocity.

[0085] ( I PV ), that is, according to the actually measured wave velocity , the calibrated wave velocity of the measured anchor cable and the calibrated wave velocity of the concrete outside the measured anchor cable to calculate based on their mutual relationship. I PVWhen it is equal to 0, it means that the measured wave velocity is equal to the wave velocity of the anchor cable, which is equivalent to no grouting and the compactness is 0. I PV When it is equal to 1, it means that the measured wave velocity is equal to the wave velocity of the concrete, which is equivalent to full grouting and the compactness is 1.

[0086]

[0087] The measured wave velocity is obtained based on the analysis of the two measured waveforms, that is, based on the arrival time of the first wave of the two waveforms T ch1 and T ch2 , the length of the beam slab L , the distances between the two acceleration sensors AS and the beam slab are denoted as L 1 and L 2 , the elevation difference of the duct (the height difference between the lowest point of the duct and the two ends) is H . The corrected duct length is L 孔 , and the wave velocity is calculated as follows:

[0088]

[0089] Since there are multiple measurement points, after obtaining the wave velocities of each measurement point, the average wave velocity can be calculated through data fusion, such as the statistical average method, and then the detection result of the grouting compactness of the to-be-detected beam body can be determined.

[0090] Based on the same inventive concept as the foregoing system embodiment, the embodiment of the present invention further provides a method for detecting the grouting compactness of bridge prestressed ducts. A same-configured acquisition device is respectively arranged at both ends of the beam body. The acquisition device close to the knocking end is used as the host, and the acquisition device at the other end is used as the slave. The method includes:

[0091] S1. When the host starts to acquire, control its time synchronization unit TU to record the host acquisition time T A0 , and send the host acquisition time to the slave through the network communication unit NU, and simultaneously store the sampling values in real-time and circularly;

[0092] S2. When the slave receives the host acquisition time, control its time synchronization unit TU to record the slave acquisition time T B0 , and simultaneously store the sampling values in real-time and circularly;

[0093] S3. When the host reaches the trigger level and starts to trigger, control its time synchronization unit TU to record the host trigger time T A1 , and send the host trigger time to the slave through the network communication unit NU;

[0094] S4. When the slave device receives the triggering moment of the master device, it controls its time synchronization unit TU to record the triggering moment T of the slave device. B1 ;

[0095] S5. Determine the time difference |T B1 -T A1 |-|T B0 -T A0 | of the two test waveforms according to the acquisition moment of the master device, the acquisition moment of the slave device, the triggering moment of the master device, and the triggering moment of the slave device.

[0096] S6. At the end of the current measurement point, intercept a section of waveform from the storage areas of the master device and the slave device respectively, display them on the same time coordinate axis, and obtain the number of sampling points that the waveform of the slave device needs to be translated according to the time difference and in combination with the sampling interval. Then, translate the waveform of the slave device according to the number of sampling points so that the waveforms of the master device and the slave device start recording from the same time starting point, in order to determine the first-wave time coordinate positions of the knocking waveform reaching the master device and the slave device.

[0097] After determining the first-wave time coordinate positions of the knocking waveform reaching the master device and the slave device, determine the measured wave velocity of the duct according to the full-length wave velocity method, and determine the grouting density of the duct according to the measured wave velocity.

[0098] Before the test starts, it further includes: determining the total number of measurement points to be measured based on the total number of externally exposed anchors of the beam to be measured from top to bottom; numbering all measurement points and displaying them on the master device and the slave device respectively; testing all measurement points one by one, and fusing the test data of all measurement points to obtain the detection result of the grouting density of the duct of the current beam to be measured.

[0099] It should be noted that each step of the method embodiment described in the embodiment of the present invention can be implemented by referring to the system embodiment, and will not be elaborated here.

[0100] The terms "including" and "having" in the description, claims and above-mentioned drawings of the present invention, and any variations thereof, are intended to cover non-exclusive inclusion. For example, a process, method, system, product or device that includes a series of steps or units does not necessarily have to be limited to those steps or units clearly listed, but may include other steps or units not clearly listed or inherent to these processes, methods, products or devices.

[0101] The block diagrams shown in the drawings are only functional entities and do not necessarily correspond to physically independent entities. That is, these functional entities can be implemented in software form, or implemented in one or more hardware modules or integrated circuits, or implemented in different networks and / or processor devices and / or microcontroller devices. The flowcharts shown in the drawings are only illustrative and do not necessarily include all the content and operations / steps, nor do they necessarily have to be executed in the described order. For example, some operations / steps can be decomposed, while some operations / steps can be combined or partially combined, so the actual execution order may change according to the actual situation.

[0102] 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 technical solutions of the embodiments of the present invention.

Claims

1. A bridge prestressed duct grouting density detection system, characterized in that: It comprises two acquisition devices with the same configuration, each of which corresponds to an acceleration sensor; each of the acquisition devices comprises a time synchronization unit, a network communication unit, a signal input module and a control unit, the time synchronization unit is used to provide timestamp information, and the network communication unit is used to provide wireless communication; the signal input module is used to acquire the signal of the acceleration sensor and pre-process it to obtain sampling data, the control unit is used to store the sampling data, and calculate the first wave time difference of the test waveforms of the two acquisition devices based on the sampling data and timestamp information of the two acquisition devices; the control unit is also used to record the host acquisition time when the host starts acquisition and send the host acquisition time to the slave, and at the same time cyclically store the sampling value in real time; the slave receives the host acquisition time, records the slave acquisition time, and at the same time cyclically stores the sampling value; when the host reaches the trigger level and starts triggering, records the host trigger time and sends the host trigger time to the slave; the slave receives the host trigger time and records the slave trigger time; and determines the time difference of the two test waveforms based on the host acquisition time, the slave acquisition time, the host trigger time and the slave trigger time.

2. A bridge prestressed duct grouting density detection system according to claim 1, characterized in that: The signal input module includes a signal interface unit, a signal conditioning unit and a signal acquisition unit. The signal interface unit is used to access the acceleration sensor, the signal conditioning unit is used to preprocess the accessed signal, and the signal acquisition unit is used to convert the preprocessed signal and output it to the control unit.

3. A bridge prestressed duct grouting density detection system according to claim 1, characterized in that: The control unit is also connected to a display unit for displaying sampling data and setting sampling parameters.

4. A bridge prestressed duct grouting density detection system according to claim 1, characterized in that: The control unit is also connected to a voice unit for voice prompting.

5. A bridge prestressed duct grouting density detection system according to claim 1, characterized in that: The control unit includes a storage subunit and an analysis subunit. The storage subunit is used to cyclically overwrite and store sampling data according to a set length. The analysis subunit is used to control the time synchronization unit to record the acquisition time and trigger time, control the network communication unit to send acquisition instructions and trigger instructions to the slave, and determine the first wave time coordinate position of the master and slave based on the sampling data of both the master and slave and the timestamp information.

6. A bridge prestressed duct grouting density detection system according to claim 5, characterized in that: The storage subunits of the two acquisition devices sample in real time according to the set length and cyclically cover the stored sampled data, and the cyclically covered storage area is at least greater than 2 times the single data sampling length.

7. A method for detecting the density of grouting of prestressed ducts in bridges, characterized in that: A collection device with the same configuration is respectively provided at both ends of the beam body, each of the collection devices is connected to an acceleration sensor, the collection device close to the striking end is used as the master, and the collection device at the other end is used as the slave. The method includes: When the host starts collecting data, it records the host collection time and sends the host collection time to the slave, while storing the sampled values in a real-time loop; The slave receives the acquisition time from the host, records the acquisition time, and stores the sampled value in real time. When the host reaches the trigger level and starts triggering, the host triggering moment is recorded and sent to the slave; The slave receives the master triggering time and records the slave triggering time; Determine the time difference between the two test waveforms according to the host acquisition time, the slave acquisition time, the host trigger time and the slave trigger time; At the end of the current measurement point, waveforms are captured from the stored data of the host and slave respectively, displayed on the same time coordinate axis, and translated based on the time difference to determine the time coordinate position of the first wave of the knocking waveform reaching the host and slave.

8. A method for detecting the density of grouting of prestressed ducts in bridges according to claim 7, characterized in that: The method further comprises: According to the time coordinate position of the first wave of the knocking waveform reaching the master and slave machines, the measured wave velocity of the duct is determined according to the full-length wave velocity method, and the duct grouting density is determined based on the measured wave velocity.

9. A method for detecting the density of grouting of prestressed ducts in bridges according to claim 7, characterized in that: The method further comprises: Determine the total number of measuring points to be tested based on the total number of exposed anchors from top to bottom of the beam to be tested; All measurement points are numbered and displayed on the master and slave devices respectively; All measuring points are tested one by one, and the test data of all measuring points are integrated to obtain the hole grouting density test results of the current beam to be tested.

10. A bridge prestressed duct grouting density detection method according to claim 7, characterized in that: The translation is performed in combination with the time difference, including: According to the time difference and the sampling interval, the number of sampling points that the slave waveform needs to be shifted is obtained; The waveform of the slave device is shifted according to the number of sampling points so that the waveforms of the master device and the slave device are recorded from the same starting time.

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