A method for detecting internal defects of concrete structures with through-steel bars

Abstract

The present invention discloses a method for detecting internal defects of a concrete structure with through-steel bars. The required detection equipment is only two ultrasonic transmitting probes, a receiving sensor array, a signal display and processing system, and an ultrasonic phased array control system. The entire detection equipment is simple to operate and easy to use. When performing detection, the present invention uses an acoustic phased array in combination with the characteristics of the concrete structure with through-steel bars to first determine the relative time delay between the receiving sensor array and the two ultrasonic transmitting probes, then generates an amplified ultrasonic signal through a special excitation method, and then calculates the distribution form of the difference energy. Finally, it is determined whether there are defects inside the structure based on the distribution form of the difference energy, and the distribution range of the defects is obtained by detecting the movement of the receiving sensor array on the surface of the structure to be tested. The entire process is non-destructive testing, so that internal defects of the concrete structure with through-steel bars can be quickly and accurately detected and located.

Description

Technical Field

[0001] The invention relates to a method for detecting internal defects of a concrete structure, in particular to a method for detecting internal defects of a concrete structure with through steel bars, and belongs to the field of non-destructive testing. Background Art

[0002] Currently, concepts such as smart construction and lifecycle management are hot topics in the new era of civil engineering. All structures within civil engineering require inspection to ensure structural safety. Inspection methods typically rely on acoustic, thermal, or X-ray technologies. However, in civil engineering, steel bars are often combined with concrete. During inspection, the steel and concrete can interfere with each other, making it difficult to achieve optimal results. Furthermore, some methods have drawbacks such as complex operation and bulky inspection equipment.

[0003] Among structures combining steel and concrete, some have steel bars that penetrate the entire structure, such as prestressed tendons and grouting sleeves in bridges. Cables, which use steel as their primary structure, also share this characteristic. Inspection focuses on the integrity of the surrounding structures, such as the grouting layer of the prestressed tendons and grouting sleeves, and the protective covering of the cables, as this is crucial for overall structural safety. Some structures are also prefabricated, requiring internal defect inspection to ensure they maintain the required support strength for subsequent use.

[0004] Based on the shortcomings of existing methods, how to provide a new method that can quickly and accurately detect and locate internal defects of concrete structures with through-steel bars, and the entire process is non-destructive testing. In addition, the detection process is simple to operate and easy to implement, which is one of the research directions of this industry. Summary of the Invention

[0005] In response to the problems existing in the above-mentioned prior art, the present invention provides a method for detecting internal defects of concrete structures with through-steel bars, which can quickly and accurately detect and locate internal defects of concrete structures with through-steel bars, and the entire process is non-destructive testing. In addition, the detection process is simple to operate and easy to implement.

[0006] In order to achieve the above-mentioned purpose, the technical solution adopted by the present invention is: a method for detecting internal defects of a concrete structure with through-steel bars, the specific steps of which are as follows:

[0007] A. Deployment of the detection device: First, select a structure to be tested, which is a concrete structure with through-steel bars. An ultrasonic transmitting probe is installed at each end of the through-steel bar, and the transmitting directions of the two ultrasonic transmitting probes are both toward the midpoint of the through-steel bar. An ultrasonic phased array control system is connected to the two ultrasonic transmitting probes respectively to control the two ultrasonic transmitting probes to excite ultrasonic waves. A receiving sensor array is placed on the upper surface of the structure to be tested, and a signal display and processing system is connected to the receiving sensor array to obtain ultrasonic signals fed back by the receiving sensor array and calculate the difference energy. The signal display and processing system is connected to the ultrasonic phased array control system to share the position and synchronization time of the receiving sensor array to facilitate modulation of the delay of the ultrasonic signal. Initially, the receiving sensor array is located near one end of the through-steel bar, completing the deployment of the detection device.

[0008] B. Determining the position of the receiving sensor array and the relative ultrasonic delay: The ultrasonic phased array control system controls the two ultrasonic transmitting probes to transmit an ultrasonic signal once each. The receiving sensor array receives the ultrasonic signals twice, thereby obtaining the relative delay between the two ultrasonic transmitting probes. The signal display and processing system then calculates and determines the position of the receiving sensor array and obtains the energy distribution of each of the two ultrasonic signals.

[0009] C. Obtain the ultrasonic interference signal at the current position and calculate the differential energy distribution: Determine the relative time delay of the two ultrasonic transmitting probes according to step B. The ultrasonic phased array control system adjusts the transmission time of the two ultrasonic transmitting probes so that the two ultrasonic signals reach the receiving sensor array at the same time. The two interfere with each other and amplify each other. The amplified signal is received by the receiving sensor array. The signal display and processing system calculates and determines the energy distribution of the amplified signal and subtracts the energy distribution of the two ultrasonic signals obtained in step B from it to obtain the differential energy distribution at the current position. The frequency and amplitude parameters of the ultrasonic signal need to be modulated according to the material properties of the structural component to be tested and the detection accuracy. The parameters of the ultrasonic signal used throughout the entire test process should be consistent.

[0010] D. Obtaining differential energy distribution at multiple locations: Move the receiving sensor array to the next detection location at a set distance along the direction through the steel bar. Repeat steps B and C to obtain the differential energy distribution at that detection location. Repeat this process to obtain the differential energy distribution at each detection location.

[0011] E. Determine the internal defects of the structure to be tested and their scope: Determine whether there are defects inside the structure to be tested at each detection position based on the energy distribution of each difference in step D, select each detection position where defects are determined to exist, and finally comprehensively determine the scope of the defects in the structure to be tested.

[0012] The principle of the present invention for judging the internal defects of the structure to be tested is as follows: The inventors have found that in concrete structures with through-steel bars, such as prestressed steel bundle grouting channels, grouting sleeves, cables, wire ropes and other structures, ultrasonic signals are excited on both sides. In the process of ultrasonic signals propagating from the through-steel bars to the surface of the structure, they can be regarded as horizontal propagation of ultrasonic signals within the far-field range of the through-steel bars. According to the law of refraction, the propagation direction of the ultrasonic signal (i.e., the excitation signal) within the structure surrounding the through-steel bars can be calculated; when the size, shape and characteristic parameters of the structure to be tested are determined, the distance and direction of the ultrasonic signal propagating from the through-steel surface to the concrete surface are fixed. If the structure is intact, the signal value y propagated on the surface of the structure is c The signal value y relative to the surface of the steel bar is only delayed by time t c and distance D c With a fixed attenuation β, that is That is, the signal energy value E after the two ultrasonic signals interfere with each other and amplify each other has a fixed difference ΔE from the energy values ​​E1 and E2 generated by a single excitation of the ultrasonic transmitting probes on both sides; ΔE presents a symmetrical shape about the midpoint of the length direction of the receiving sensor array and a normal distribution-like shape. Its specific shape is determined by the set excitation signal and propagation characteristics, and is hereinafter referred to as the predetermined shape. If there is a defect in the structure, when either of the ultrasonic signals passes through the defect, it will be reflected in large quantities due to the impedance difference between the defect and the structure itself. The signal value reaching the surface of the structure will decay to near zero, and then when the two are emitted together, if either one approaches zero, the difference energy ΔE will be increased. (x) Approaching zero (ie y c →0), causing the area that should have been amplified to fail to achieve the expected amplification, ultimately affecting the distribution of ΔE. This disrupts its normal distribution, which is symmetrical at the midpoint along the length of the receiving sensor array (i.e., there are areas of missing or significantly attenuated distribution). This discovery enables the location and range of internal defects in the structure under test to be detected.

[0013] Furthermore, the specific process of determining the position of the receiving sensor array and the relative ultrasonic delay in step B is as follows: the arrival times of the two ultrasonic signals are t1 and t2 respectively, and the relative time delay between the two signals is Δt=t2-t1. Then, the horizontal distance ΔL=vΔt / 2 between the center of the receiving sensor array and the center of the structure to be measured is calculated, where v is the wave velocity in the structure to be measured, thereby determining the position of the receiving sensor array.

[0014] Furthermore, the calculation of the differential energy distribution in step C is specifically as follows: first, a signal segment of a certain length in the signal after interference amplification is selected, where the length of the signal segment can be determined by the time difference between the longitudinal wave and the transverse wave propagating to the same position in the concrete after the ultrasonic wave is refracted; then, the energy distribution E of the selected signal segment is calculated, and the energy distributions E1 and E2 of the two ultrasonic signals in step B are superimposed, and E is subtracted from the superimposed E1 and E2 to obtain the differential energy ΔE.

[0015] Furthermore, the receiving sensor array is composed of a row of receiving sensors, the length of which is not shorter than the length L of the envelope curve of the excited ultrasonic signal. s The minimum value is set to ensure that the receiving sensor array can receive the complete energy distribution.

[0016] Furthermore, the specific process of the two ultrasonic signals simultaneously arriving at the receiving sensor array in step C is as follows: based on the relative time delay, the ultrasonic phased array control system adjusts the transmission time of the two ultrasonic transmitting probes to ensure that the intersection of the two ultrasonic signals interfering with each other and the midpoint of the receiving sensor array are on the same cross-section, so that the ultrasonic signal is amplified as a whole due to interference within the length range of the receiving sensor array.

[0017] Furthermore, the specific process of step E is as follows: if the difference energy distribution ΔE at the current detection position exhibits a predetermined pattern along the length of the receiving sensor array, it indicates that no defects have been detected within the structure under test at that detection position; if the difference energy distribution ΔE at the current detection position exhibits a missing or significantly attenuated region along the length of the receiving sensor array compared to the predetermined pattern, it indicates that a defect has been detected within the structure under test at that detection position. Subsequently, each detection position where a defect is determined is selected. According to the aforementioned principle, when the size, shape, and characteristic parameters of the structure under test are determined, the distance and direction of the ultrasonic signal propagating from the surface of the penetrating steel bar to the concrete surface are fixed. Therefore, the range of the defect within the structure under test is comprehensively determined based on each detection position and the propagation direction of the ultrasonic wave.

[0018] Furthermore, the distance set in step D is determined according to the accuracy required for detection, and its maximum value does not exceed the length of the receiving sensor array; the maximum value is set to ensure that the structure to be detected is not missed during detection.

[0019] Compared with the prior art, the detection equipment required by the present invention is only two ultrasonic transmitting probes, a group of receiving sensor arrays, and a signal display and processing system and an ultrasonic phased array control system. The entire detection equipment is simple to operate and easy to use. When performing detection, the present invention is based on the principle of discovery, and uses an acoustic phased array combined with the characteristics of concrete structures with through-steel bars to detect and locate internal defects in the structure. First, the relative time delay between the receiving sensor array and the two ultrasonic transmitting probes is determined, and then an amplified ultrasonic signal is generated through a special excitation method, and then the distribution form of the difference energy is calculated. Finally, whether there are defects inside the structure is determined based on the distribution form of the difference energy, and the distribution range of the defects is obtained by moving the receiving sensor array on the surface of the structure to be tested. The entire process is non-destructive testing, so that internal defects of concrete structures with through-steel bars can be detected and located quickly and accurately. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a schematic diagram of the layout of the present invention during detection;

[0021] Figure 2 is a schematic diagram of an ultrasonic signal in the present invention;

[0022] Figure 3 It is a schematic diagram of the motion detection process in the present invention.

[0023] In the figure: 1-ultrasonic transmitting probe, 2-ultrasonic phased array control system, 3-signal display and processing system, 4-receiving sensor array, 5-through steel bar, 6-structure to be tested, 7-defect. DETAILED DESCRIPTION

[0024] The present invention will be further described below.

[0025] like Figure 1 As shown, the specific steps of the present invention are:

[0026] A. Arrange the detection device: First, select the structure to be tested 6, which is a concrete structure with a through steel bar 5. An ultrasonic transmitting probe 1 is installed at each end of the through steel bar 5, and the transmitting direction of the two ultrasonic transmitting probes 1 is toward the midpoint of the through steel bar 5; the ultrasonic phased array control system 2 is connected to the two ultrasonic transmitting probes 1 respectively, and is used to control the two ultrasonic transmitting probes 1 to excite ultrasonic waves; Figure 2As shown, it is a sinusoidal ultrasonic signal modulated by Gaussian distribution, which attenuates with the propagation distance in the spatial domain. In order to achieve better detection results, different excitation waveforms and initial amplitudes need to be modulated according to the detection accuracy requirements in different structures to be tested; a receiving sensor array 4 is placed on the surface of the structure to be tested 6. The receiving sensor array 4 consists of a row of receiving sensors, and its length is not shorter than the length L of the envelope curve of the excited ultrasonic signal. s The minimum value is set to ensure that the receiving sensor array 4 can receive the complete energy distribution. The signal display and processing system 3 is connected to the receiving sensor array 4 to obtain the ultrasonic signal fed back by the receiving sensor array 4 and calculate the difference energy. The signal display and processing system 3 is connected to the ultrasonic phased array control system 2 to share the position and synchronization time of the receiving sensor array 4 to facilitate the modulation of the ultrasonic signal delay. Initially, the receiving sensor array 4 is located near one end of the through-steel bar 5, completing the layout of the detection device.

[0027] B. Determine the position of the receiving sensor array and the relative ultrasonic delay: The ultrasonic phased array control system 2 controls the two ultrasonic transmitting probes 1 to transmit an ultrasonic signal once respectively, and the receiving sensor array 4 receives the arrival time of the ultrasonic signals twice respectively, thereby obtaining the relative delay of the two ultrasonic transmitting probes 1. Then, the signal display and processing system 3 calculates and determines the position of the receiving sensor array 4 and obtains the energy distribution of each of the two ultrasonic signals. The specific process is: the arrival time of the two ultrasonic signals is t1 and t2 respectively, then the relative time delay between the two signals Δt = t2 - t1, and then the horizontal distance ΔL = vΔt / 2 between the center of the receiving sensor array 4 and the center of the structure to be measured 6 is calculated, where v is the wave velocity within the structure to be measured 6, thereby determining the position of the receiving sensor array 4.

[0028] C. Obtain the ultrasonic interference signal at the current position and calculate the difference energy distribution: Determine the relative time delay of the two ultrasonic transmitting probes 1 according to step B, and the ultrasonic phased array control system 2 adjusts the emission time of the two ultrasonic transmitting probes 1 so that the two ultrasonic signals arrive at the receiving sensor array 4 at the same time. The specific process is as follows: According to the relative time delay, the ultrasonic phased array control system 2 adjusts the emission time of the two ultrasonic transmitting probes 1 to ensure that the intersection of the two ultrasonic signals interfering with each other and the midpoint of the receiving sensor array 4 are on the same cross section, so that the ultrasonic signal is amplified as a whole due to interference within the length range of the receiving sensor array 4; the signal display and processing system 3 calculates and determines the energy distribution of the signal after interference amplification, and subtracts the energy distribution of the two ultrasonic signals obtained in step B, thereby obtaining the current The difference energy distribution at the previous position is as follows: first, a signal segment of a certain length in the signal after interference amplification is selected. The time length of the signal segment is determined by the time difference between the longitudinal wave and the transverse wave propagating to the same position when the ultrasonic wave is refracted into the concrete. When the through-steel bar 5 is far away from the surface of the structure to be tested 6, that is, the size of the structure to be tested is large and the influence of the guided wave is small, the full segment signal can also be taken for calculation; then, the energy distribution E of the selected signal segment is calculated, and the energy distributions E1 and E2 of the two ultrasonic signals in step B are superimposed, and E is subtracted from the superimposed E1 and E2 to obtain the difference energy ΔE; wherein the frequency and amplitude parameters of the ultrasonic signal need to be modulated according to the material properties of the structural component to be tested and the detection accuracy, and the parameters of the ultrasonic signal used in the entire test process should be consistent.

[0029] D. Obtaining multiple position difference energy distributions: Figure 3 As shown, the receiving sensor array 4 is moved to the next detection position at a set distance along the direction of the penetrating steel bar 5. After completion, steps B and C are repeated to obtain the differential energy distribution of the detection position. By repeating this process, the differential energy distribution of each detection position can be obtained. The set distance is determined according to the accuracy required for the detection, and its maximum value does not exceed the length of the receiving sensor array 4. This ensures that the structure 6 to be detected is not missed during detection.

[0030] E. Determine the internal defects 7 of the structure to be tested and their range: Determine whether there are defects inside the structure to be tested 6 at each detection position based on the differential energy distribution in step D. The specific process is as follows: if the differential energy distribution ΔE at the current detection position is symmetrical about the midpoint of the longitudinal direction of the receiving sensor array 4 and has a normal distribution-like shape, it means that no internal defects 7 of the structure to be tested 6 are found at this detection position; if the differential energy distribution ΔE at the current detection position has a missing or greatly attenuated area in the longitudinal direction of the receiving sensor array 4, it means that internal defects 7 of the structure to be tested 6 are found at this detection position. Then, each detection position where defects are determined to exist is selected. According to the above principle, when the size, morphology and characteristic parameters of the structure to be tested 6 are determined, the distance and direction of the ultrasonic signal propagating from the surface of the penetrating steel bar 5 to the concrete surface are fixed. Therefore, the range of the defect in the structure to be tested 6 is comprehensively determined based on each detection position and the propagation direction of the ultrasonic wave.

[0031] The ultrasonic transmitting probe 1, ultrasonic phased array control system 2, signal display and processing system 3 and receiving sensor array 4 are all existing equipment or devices and can be directly purchased on the market.

[0032] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for detecting internal defects of a concrete structure with through-steel bars, characterized in that: The specific steps are: A. Deployment of the detection device: First, select a structure to be tested, which is a concrete structure with through-steel bars. An ultrasonic transmitting probe is installed at each end of the through-steel bar, and the transmitting directions of the two ultrasonic transmitting probes are both toward the midpoint of the through-steel bar. An ultrasonic phased array control system is connected to the two ultrasonic transmitting probes respectively to control the two ultrasonic transmitting probes to excite ultrasonic waves. A receiving sensor array is placed on the upper surface of the structure to be tested, and a signal display and processing system is connected to the receiving sensor array to obtain ultrasonic signals fed back by the receiving sensor array and calculate the difference energy. The signal display and processing system is connected to the ultrasonic phased array control system to share the position and synchronization time of the receiving sensor array to facilitate modulation of the delay of the ultrasonic signal. Initially, the receiving sensor array is located near one end of the through-steel bar, completing the deployment of the detection device. B. Determining the position of the receiving sensor array and the relative ultrasonic delay: The ultrasonic phased array control system controls the two ultrasonic transmitting probes to transmit an ultrasonic signal once each. The receiving sensor array receives the ultrasonic signals twice, thereby obtaining the relative delay between the two ultrasonic transmitting probes. The signal display and processing system then calculates and determines the position of the receiving sensor array and obtains the energy distribution of each of the two ultrasonic signals. C. Obtaining the ultrasonic interference signal at the current position and calculating the differential energy distribution: Determine the relative time delay of the two ultrasonic transmitting probes according to step B. The ultrasonic phased array control system adjusts the transmission time of the two ultrasonic transmitting probes so that the two ultrasonic signals arrive at the receiving sensor array at the same time. The two ultrasonic signals interfere with each other and amplify each other. The amplified signal is received by the receiving sensor array. The signal display and processing system calculates and determines the energy distribution of the amplified signal, subtracts the energy distribution of the two ultrasonic signals obtained in step B from the energy distribution of the two ultrasonic signals, and thus obtains the differential energy distribution at the current position. D. Obtaining differential energy distribution at multiple locations: Move the receiving sensor array to the next detection location at a set distance along the direction through the steel bar. Repeat steps B and C to obtain the differential energy distribution at that detection location. Repeat this process to obtain the differential energy distribution at each detection location. E. Determine the internal defects of the structure to be tested and their scope: Determine whether there are defects inside the structure to be tested at each detection position based on the energy distribution of each difference in step D, select each detection position where defects are determined to exist, and finally comprehensively determine the scope of the defects in the structure to be tested.

2. The method for detecting internal defects of a concrete structure with through-steel bars according to claim 1, characterized in that: The specific process of determining the position of the receiving sensor array and the relative ultrasonic delay in step B is as follows: the arrival times of the two ultrasonic signals are t1 and t2 respectively, and the relative time delay between the two signals is Δt=t2-t1. Then, the horizontal distance ΔL=vΔt / 2 between the center of the receiving sensor array and the center of the structure to be measured is calculated, where v is the wave velocity in the structure to be measured, thereby determining the position of the receiving sensor array.

3. The method for detecting internal defects of a concrete structure with through-steel bars according to claim 1, characterized in that: The calculation of the differential energy distribution in step C is specifically as follows: first, a signal segment of a certain length in the signal after interference amplification is selected, where the length of the signal segment is determined by the time difference between the longitudinal wave and the transverse wave propagating to the same position in the concrete after the ultrasonic wave is refracted; then, the energy distribution E of the selected signal segment is calculated, and the energy distributions E1 and E2 of the two ultrasonic signals in step B are superimposed, and E is subtracted from the superimposed E1 and E2 to obtain the differential energy ΔE.

4. The method for detecting internal defects of a concrete structure with through-steel bars according to claim 1, characterized in that: The receiving sensor array is composed of a row of receiving sensors, the length of which is not shorter than the length L of the envelope curve of the excited ultrasonic signal. s .

5. The method for detecting internal defects of a concrete structure with through-steel bars according to claim 1, characterized in that: The specific process of the two ultrasonic signals simultaneously arriving at the receiving sensor array in step C is as follows: based on the relative time delay, the ultrasonic phased array control system adjusts the transmission time of the two ultrasonic transmitting probes to ensure that the intersection point where the two ultrasonic signals interfere with each other and the midpoint of the receiving sensor array are on the same cross-section, so that the ultrasonic signal is amplified as a whole within the length range of the receiving sensor array due to interference.

6. The method for detecting internal defects of a concrete structure with through-steel bars according to claim 1, characterized in that: The specific process of step E is as follows: if the difference energy distribution ΔE at the current detection position is symmetrical about the midpoint of the length direction of the receiving sensor array and is similar to a normal distribution in the length direction of the receiving sensor array, it means that the detection position has not found any defects inside the structure to be tested; if the difference energy distribution ΔE at the current detection position has a missing or greatly attenuated area in the length direction of the receiving sensor array, it means that the detection position has found any defects inside the structure to be tested.

7. The method for detecting internal defects of a concrete structure with through-steel bars according to claim 1, characterized in that: The distance set in step D is determined according to the required detection accuracy, and its maximum value does not exceed the length of the receiving sensor array.

Images