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The fabricated shear wall with a grouting sleeve is used widely in structural engineering. The damage characteristics of a fabricated shear wall reinforced with angle steel of inadequate grouted material strength were investigated using acoustic emission (AE) technology under a horizontal repeated load. The results showed that evaluation of the AE energy and Ib value exposed the crack expansion and damage evolution of the fabricated shear walls; the sudden rise in the energy level predicted the occurrence of micro-cracks in the shear wall. The trends of the AE accumulated energy and accumulated hysteretic energy of the specimens had a good correlation. The AE Ib value results illustrated that the destruction was most serious inside the shear wall with an inadequate grouted material strength at the failure stage. The trends of AE HI and Sr could better characterize the crack propagation of the shear walls. The AE damage model was proposed based on the Park–Ang damage model incorporating fractal energy density, which could effectively evaluate the damage degree of shear walls under repeated loading. [ABSTRACT FROM AUTHOR]

Brick masonry structures will suffer different degrees of damage in their long‐term service. The common damage modes involve compression and shear damage. The acoustic emission (AE) technology, including improved b‐value (Ib‐value), signal intensity analysis, and the k‐means clustering method, was carried out during uniaxial compression and shear experiments to qualitatively and quantitatively assess the damage state of the brick masonry. Results demonstrate that the shear damage exhibits a more obvious brittle failure characteristic compared with the uniaxial compression damage. The Ib‐value could reflect the damage evolution state of the brick masonry whether it is uniaxial or shear damage (i.e., every decrease in the Ib‐value is a manifestation of damage expansion). The boundary of HI‐Sr in the signal intensity analysis is proposed to differentiate the mild, moderate, and serious damage under uniaxial compressive, and the boundary is proposed to distinguish the mild and serious damage under shear. The appearance of the signal cluster with the highest ring count, energy, and duration implies the failure of the brick masonry under uniaxial compressive and shear. [ABSTRACT FROM AUTHOR]

Summary: As one of the most important load‐bearing components of cable‐stayed bridges, the integrity of cables is essential to bridge condition assessment. However, the traditional one‐dimensional damage location method has difficulty determining the spatial location of the damage source on parallel steel wire cables. Acoustic emission (AE) technology is a common means of structural health monitoring, and one of its most beneficial attributes is the ability to localize the damage. For this reason, a three‐dimensional (3D) location algorithm based on the AE signal propagation path is proposed for cable damage localization. First, the propagation path of simulated AE signals in a parallel steel wire bundle (PSWB) was visualized using COMSOL Multiphysics software platform. Then, a 3D localization algorithm suitable for PSWB damage is proposed based on the propagation path and dispersion characteristics of AE waves. After that, experimental verifications were performed, and it was found that the damage locations can be determined accurately using the proposed algorithm. This algorithm helps to localize the damage source with only a few sensors and is crucial for cable protection and replacement. [ABSTRACT FROM AUTHOR]

• Quantify the attenuation of the outer material of the prestressed steel strand on its damaged AE signals. • Analyze the parameters that can characterize the attenuation of the AE signals. • The location of the AE sensors is proposed to be beneficial to bridges health monitoring. The prestressed steel strand is the key stressed member of the concrete T-beam bridge. The acoustic emission (AE) signal generated by damaged or broken strands will undergo attenuation due to the outer wrapping material before reaching the sensor on the beam's surface. Additionally, the placement of the sensor significantly impacts the accuracy of monitoring prestressed steel strand damage. To determine the optimal position of the AE sensor for detecting prestressed steel strand damage on the concrete surface of the T-beam, this study investigated the attenuation of AE signals during the propagation process of wire breakages using concrete specimens of varying strengths and different materials for embedded bellows. Furthermore, lead-breaking tests were conducted on scaled T-beam models to clarify the sensor placement position for health monitoring of prestressed steel strands based on the attenuation of amplitude, energy, and duration of AE signals at different monitoring positions. The results indicate that for acoustic emission monitoring of T-beam bridges using metal bellows, sensors can be positioned where the concrete thickness around the bellows does not exceed 70 mm, satisfying monitoring requirements. Amplitude can serve as an optimal parameter for real bridge monitoring to enhance the accuracy of acoustic emission health monitoring for prestressed steel strand damage. The findings offer valuable insights for the placement of acoustic emission sensors in real bridges, thereby enhancing the precision of health monitoring for prestressed steel strand damage through acoustic emission. [ABSTRACT FROM AUTHOR]

Summary: The acoustic emission (AE) technique is a non‐destructive testing method widely used in various structural health monitoring fields, and it is highly sensitive to the emergence and development of material corrosion. This study developed a method of employing the AE technique to evaluate the corrosion degree of stay cable high‐strength steel wires under pre‐stress and impressed current cathodic protection (ICCP) in a simulated marine atmospheric rainwater environment. The variation characteristics of AE parameters under various pre‐stress levels and protection current densities were investigated. Results showed that the more negative the open circuit potentials (OCPs) and the greater the average corrosion rates, the higher the cumulative AE parameters. In the AE intensity analysis of corrosion damage for stay cable high‐strength steel wires, the constants J and the K were taken as 40 and 25 hits, respectively. The corrosion of steel wires was divided into no corrosion, slight corrosion, medium corrosion, and severe corrosion. The corrosion degree of specimens with ICCP was classified as no corrosion and slight corrosion, whereas that of unprotected specimens was classified as medium corrosion and severe corrosion. [ABSTRACT FROM AUTHOR]

Summary: The precise localization of cable damage is a major issue in bridge engineering. The acoustic emission (AE) method has been applied to detect defects for cable structures in bridges. In this paper, an AE localization method is proposed to localize both lateral and longitudinal positions of defects in a parallel steel wire bundle composed of seven steel wires. The proposed method is verified numerically and experimentally. Tension failure test of the parallel steel wire bundle composed of seven wires was carried out, and the precise localization of defects was realized by through modal AE techniques and the analysis of the characteristics of AE signal. A Multiphysics model based on COMSOL was established to facilitate the visualization of stimulated AE propagated in the parallel wire bundle. The propagation mechanism of AE signal was studied, and the feasibility of localization method was verified. [ABSTRACT FROM AUTHOR]

• Spatial propagation of AE signals in PSWC was studied. • Hexagonal AE signals propagation was observed in the transverse section. • AE signals propagate oscillationally in the longitudinal section. • Longitudinal velocity is 4.2 times faster than transverse velocity. • AE signals propagate longitudinally and then transversely. Accurate spatial propagation characteristics facilitate damage spatial localization, which is crucial for assessing the condition of parallel steel wire cables (PSWC). Existing studies have focused on the longitudinal propagation of acoustic emission (AE) signals, limiting accurate spatial damage assessment. This study comprehensively explored the spatial propagation characteristics of AE signals in PSWC using finite elements and attenuation tests. AE signals propagate hexagonally on the transverse section, with different amplitude attenuation rates at different angles—8% at 0° and 60°, 5 % at 30° and 45°. Additionally, AE signals exhibit oscillatory propagation between different wires in the longitudinal direction. The longitudinal speed (5706 m/s) is approximately 4.2 times faster than the transverse speed (1371 m/s), and the propagation path can be simplified as longitudinal and then transverse, offering valuable guidance for damage localization. The optimum frequency is 150 kHz in the transverse direction and 30 kHz in the longitudinal direction. [ABSTRACT FROM AUTHOR]

• The study was used to evaluate the sleeve grouting connection compactness. • A recognition system should be established in the subsequent research. • The identification software should be edited for sleeve grouting compactness. The sleeve grouting compactness of a fabricated structure directly affects its quality and safety, which are important. In this study, an acoustic emission system composed of an acoustic emission instrument and signal generator is used to test the preliminary detection of sleeve grouting connection compactness via a reasonable test method. The acoustic emission characteristics of prefabricated components under the excitation of signal generator are collected, and the characteristics of acoustic emission signals under different concrete strength, hollow sleeve positions, and compactness cases are analyzed. Results show that the amplitude of C30 concrete (66.63–66.86 dB) is higher than that of C40 concrete (56.96–57.54 dB). For the C40 specimen, the amplitude of the hollow sleeve is between 53.77 dB and 54.55 dB, which is lower than that of concrete. The amplitude of the compacting sleeve is between 67.61 dB and 67.86 dB, which is higher than that of the hollow sleeve. The amplitude of the compacting sleeve after adding reinforcement is between 59.98 dB and 60.37 dB, which are lower than that before adding reinforcement. The characteristic amplitude and energy of the acoustic emission signal are distributed obviously under the abovementioned working conditions. Wavelet analysis for the received acoustic waveforms was performed by the Continuous Wavelet Transform. The results show that there are some differences among the wavelet signals. Hence, the sleeve grouting connection compactness of fabricated structure can be detected on the basis of acoustic emission technology. [ABSTRACT FROM AUTHOR]

• Discussing the variation characteristics of AE parameters in the experiment. • Different b -value characteristics correspond to different damage stages. • Introducing AE probability density function into masonry materials. • Establishing a linear relationship between AE cumulative events and damage variable. Structural health monitoring of masonry structures is an ongoing engineering challenge. An innovative method for establishing a database corresponding to the parameter characteristics of acoustic emission (AE) signals and the damage information was proposed. Therefore, it is necessary and important to study the AE parameter characteristics of masonry structures. In this study, the in-situ uniaxial compression test with the AE monitoring for masonry specimen was performed. The damage evolution of masonry was analyzed qualitatively and quantitatively by the characteristics of several typical AE parameters. Results indicated that the variation characteristics of AE ringing counts and peak frequency were more consistent with the final brittle failure of masonry specimen. Furthermore, the relationship between AE cumulative events and stress level of masonry material was studied. A linear relationship between AE cumulative events and damage variable was established to assess damage degree of masonry quantitatively. [ABSTRACT FROM AUTHOR]

Highlights • The three time monitoring parameters PDT, HDT, HLT are determined. • The characteristics of several common AE parameters are discussed. • Low frequency components dominate at the failure stage. • AE signals with high amplitude and high energy in the low-frequency can predict the failure. Abstract Damage assessment of masonry buildings in service is the key to structural health monitoring. A uniaxial compression test of brick masonry specimens based on acoustic emission (AE) technology was conducted to monitor and assess the dynamic damage and failure mechanisms of masonry structures under load in real time. The variation characteristics of the ringing counts, energy, and peak frequency of the AE characteristic parameters of the masonry specimens during the entire uniaxial compression process were collected and recorded, and the reference values of the time parameters of AE monitoring were determined. Results showed that the number of AE ringing counts increased sharply and the slope of the cumulative energy curve increased remarkably at the final failure stage of the brick masonry specimens under compression. In addition, the component ratio of the peak frequency in the low-frequency band increased and that of the peak frequency in the high-frequency band decreased. The damage status of the masonry structures could be predicted qualitatively by the AE signals with high energy in the low-frequency band. The ringing counts of the AE sensors at different locations on the masonry specimens were compared, and the rationalities of the position and number of AE sensors fixed on the brick masonry specimens in the uniaxial compression test were discussed. [ABSTRACT FROM AUTHOR]

• AE monitoring can be an alternative to traditional methods. • AET can implement health monitoring of steel plate reinforced ECC-NC composite beams. • AE energy and Ib -value characteristics are more sensitive to early warning of steel plate reinforcement failure. • The AE sensors are recommended to be arranged directly on the steel plate used for reinforcement. The reinforcement effect evaluation of cement composite (ECC) normal concrete (NC) composite beams in steel plate reinforcement engineering has always been a difficulty in structural monitoring. As a kind of structural health monitoring (SHM) technology, acoustic emission technique (AET) can be used to analyze the structural failure mode, but it has not been carried out to select the optimal AE parameters and AE sensors arrangement to analyze the crack propagation of concrete structures and the early warning of reinforcement measures failure. And the traditional monitoring method also failed to realize the early warning of steel plate reinforcement failure. In this work, first, AET was used to monitor the four-point bending test of ECC-NC composite beams reinforced with steel plates. Then, the crack propagation process of the composite beam and the reinforcement effect of the steel plates are analyzed by using AE parameters. Finally, through the comparative analysis of AE parameters at different positions of the composite beam, the optimal AE parameters and the arrangement of AE sensors are selected. The results show that the AE ringing count fails to realize the early warning of steel plate reinforcement failure. The characteristics of AE energy, peak frequency, and Ib -value collected by the AE sensor arranged on the steel plate on the beam side can realize the analysis of the crack propagation process of the composite beam and the early warning of the failure of the steel plate reinforcement. The Ib -value and AE peak frequency change characteristics collected by the AE sensor directly arranged at the mid-span on the top of the composite beam cannot implement the crack propagation process of the composite beam and the early warning of steel plate reinforcement failure. It is not recommended to place the AE sensor at the top mid-span position of the composite beam. The RA-AF correlation distribution shows that the shear cracks are mainly generated during the bending process of ECC-NC composite beams reinforced with steel plates. The research on the optimal AE parameters and the arrangement of AE sensors has important academic significance and engineering application value for realizing AET monitoring of the crack propagation process of ECC-NC composite beams reinforced with steel plates and early warning of the steel plate reinforcement failure. [ABSTRACT FROM AUTHOR]

• The relationship between grouting material strength and bonding strength was revealed. • A design method is proposed to avoid bond failure of the grouted sleeves. • The rapid increase of the ringing count and energy could be a precursor of the bond failure. • The safety zone to avoid the bond failure of the grouted sleeves was established. The grouted sleeve connection is widely used in fabricated structures, and the bonding performance is a vital indicator to evaluate its property. Total of 24 grouted sleeves specimens were designed to study the effect of grouting material strength on bond strength of two forms of sleeves under monotonic tensile loading. The qualitative and quantitative evaluation of the bond failure damage process of the grouted sleeves was carried out relying on acoustic emission (AE) technology. Results demonstrated that the relative displacement between the rebar and grouting material was generated after the hardening stage of the tensile process. More importantly, the relationship between grouting material strength and bonding strength was revealed. Compared with Carbon steel sleeves, ductile iron sleeves exhibited better bonding properties in the tensile process. Moreover, a designing method was proposed to prevent bond failure of the ductile iron sleeves and carbon steel sleeves. The trends of AE ringing count and energy with the variation of load could better characterize the bonding failure damage process, which corresponded well to the five stages of the tensile process. The rapid increase of the ringing count and energy level could be a precursor to the occurrence of bond failure of the grouted sleeve. The safety zone to avoid the bond failure of the grouted sleeves was established based on the AE intensity analysis. The emergence of the AE signal corresponding to the bond failure should be vigilant in engineering practice. [ABSTRACT FROM AUTHOR]

• Masonry damage was analyzed deeply on both qualitative and quantitative levels. • PSO-SVM model was employed for automatic identification of damage phases of signals. • A mathematical expression between the AE parameter and the damage index was established. • A damage index-based early warning of masonry was proposed. Evaluation of masonry damage is considerably challenging because of the non-homogeneous nature of masonry materials and the rapid attenuation of signals. To this end, a methodology combining qualitative analysis employing support vector machine-based acoustic emission (AE) monitoring and quantitative analysis using AE rate process theory was proposed. In this work, firstly, the propagation attenuation characteristics of the AE amplitude and frequency were studied using pencil-lead break tests. The hybrid PSO-SVM model was employed to automatically identify the damage stages of the AE signals based on the field in-situ axial compression test data. Then, laboratory compression and shear tests on small-scale specimens were performed with AE monitoring. The Boltzmann sigmoidal modified function between relative stress and AE hits was established. Based on qualitative and quantitative analysis, a damage index-based early warning range was proposed, which can help to decide the damage level of masonry structures. The results of this paper can provide some new insight for the analysis of masonry damage. [ABSTRACT FROM AUTHOR]

• A new type of UHPC-NC beam is designed. • Several AE parameters are used for monitor the crack propagation. • The optimal AE monitoring parameters are selected. • AE monitoring can be an alternative to traditional methods. Ultra high performance concrete (UHPC) has more outstanding mechanical properties and durability than normal concrete (NC) materials. Currently, analysis methods for the mechanical properties of UHPC structures and UHPC composite structures, such as measuring structural deflection, strain, and observing crack propagation, are relatively single. Acoustic emission (AE) technique is a non-destructive testing method that evaluates the damage state of structures effectively. The variation characteristics of AE parameters can be used to analyze the damage process and the failure precursor information of the structures. On this basis, AE technique was used to monitor the crack propagation of the UHPC-NC composite beam under four-point bending test in this study. Results showed that the U-shape UHPC layer gave full play to its high strength and ductility characteristics under bending, which was mainly manifested in reducing the number and width of cracks of the UHPC-NC composite beam, reducing the mid-span deflection and increasing the cracking load (P cr) and ultimate load (P u). AE ringing counts, energy, and b-value showed different and easily distinguishable variation characteristics at each failure stage of UHPC-NC composite beam and can be considered the optimal AE monitoring parameters. RA-AF association analysis can be used to further analyze the failure mode of UHPC-NC composite beam. AE monitoring method can be considered an alternative to traditional monitoring methods for the real-time monitoring of crack propagation in UHPC-NC composite beams. [ABSTRACT FROM AUTHOR]

• Qualitative assessment using variation of the AE parameters. • Quantitative assessment of damage evolution with AE rate-process analysis. • Proposing the polynomial model between AE events and stress level. Shear is the dominant mode of masonry structural failure. A shear test of brick masonry specimen based on acoustic emission (AE) monitoring was performed in this study to assess the damage state of masonry structure reliably. AE parameters and rate-process analysis were used to analyze the damage evolution of brick masonry in shear failure from qualitative and quantitative perspectives. Results showed that variation characteristics of different AE parameters of multiple channels are basically the same throughout the test process. The specimen enters the rapid failure stage when the relative stress reaches 80%. The fourth-order polynomial fitting model between the number of AE events and their corresponding was proposed in this study for quantitative assessment. Analysis of the AE rate-process based on the fourth-order polynomial demonstrated that AE probability density f (V) and damage index D can quantitatively reflect the damage degree of brick masonry in real time. [ABSTRACT FROM AUTHOR]

• Apply impressed current cathodic protection to parallel wires. • The rainwater used as electrode. • Acoustic emission used to study the test method. The corrosion durability of bridge cables in operation is prominent. This study proposes an active protection method to apply impressed current cathodic protection (ICCP) to bridge cable parallel wires. The weight loss method, scanning electron microscopy, electrochemical test, and acoustic emission (AE) signal characteristic analysis were used to study the test method for electrochemical corrosion protection of cable parallel wires using rainwater conduction. Results show that cable wires are corroded on the surface and inside, whereas the cable wires with ICCP show different changes. The cable wires are effectively protected in the environment where a sodium chloride solution is used to simulate rainfall. In the AE test of the cable wires after corrosion using a signal generator, the main frequency of the AE signal gradually increases with the increase in corrosion degree. The high corrosion degree of the cable wires induces dispersion. The characteristics of AE signal can reflect the corrosion degree of the cable wires, and ICCP can decrease the corrosion rate of the cable wires. [ABSTRACT FROM AUTHOR]

Summary: The monitoring and localization of defects and wire breaking of bridge cable are vital to the safe operation of the whole bridge. In this work, an innovative monitoring method that uses waveguides to draw out the steel wires at the end of the cable is proposed. This monitoring method can effectively capture the acoustic emission (AE) signal produced by defects and wire breaking of the cable. The transverse position of the wire breaking can also be accurately located so as to provide basis for the decision making of maintenance department. The pencil‐lead breaks (PLB) test method is utilized to investigate the influence of the transition modes between the waveguide and the sensor and the connection modes between the waveguide and the cone on the AE signal. The PLB test and tensile test method are utilized to examine the AE signal characteristics of different sensors at the end of steel wires. Results showed that the cone transition between the waveguide and the sensor and the welding connection between waveguide and cone exhibit the minimum effect on AE waveform and parameters, such as amplitude, compared with that of the reference sensor without waveguide. In the tensile test, the transverse position of the wire breaking cannot be identified by analyzing the AE signals collected by each senor when the wire breaks, whereas it can be identified in the process of defects before the wire breaks. [ABSTRACT FROM AUTHOR]

• Visualization of AE waves propagation in prestressed steel strand by numerical simulation. • AE frequency, amplitude and energy attenuation laws in prestressed steel strand with prestress levels. • AE amplitude and energy attenuation laws in prestressed steel strand of full-size prestressed hollow slab girder. The study of acoustic emission waves propagation mechanism and attenuation laws for damage of prestressed steel strands is the theoretical basis for acoustic emission health monitoring of prestressed steel strands such as stay cables, slings, suspenders, and concrete structures. Firstly, the propagation mechanism of acoustic emission waves in prestressed steel strands is studied using numerical simulation methods. Secondly, the amplitude and energy attenuation laws of acoustic emission waves caused by damage of prestressed steel strands are analyzed by experimental research, and the amplitude and energy attenuation models of the influence of prestress level are constructed. Finally, the constructed acoustic emission attenuation models are analyzed in combination with practical engineering. The results show that numerical simulation visualizes the propagation path of acoustic emission waves in prestressed steel strands; With the increase of prestress levels, the acoustic emission frequency distribution of prestressed steel strands damage ranges from 100 to 200 kHz, with a dominant frequency of 160 kHz, the acoustic emission amplitude and energy attenuation coefficients decrease, and the amplitude attenuation is slower than the energy attenuation; The acoustic emission amplitude attenuation of prestressed steel strands damage in prestressed hollow slab beams is 5 times faster than that of steel strands without surrounding media. [ABSTRACT FROM AUTHOR]