This study explores the damage evolution and crack behavior exhibited by CFRP-strengthened corroded RC beams subjected to bending loads, with the application of AE monitoring. The results show that three primary failure modes were observed: concrete cover separation, debonding of the CFRP sheet with anchor pullout and matrix cracking and fiber tearing, with the middle mode exhibiting greater ductility. AE ringing counts analysis effectively divided the damage process into three stages: initial damage, damage development, and continuous damage. Signal intensity analyses provided insights into damage severity, revealing enhanced crack propagation in corroded beams, while severe corrosion reduced AE signal frequency and intensity in later stages, indicating initial crack activity inhibition and accelerated damage in mild to moderate corrosion. The Ib-value demonstrated trends in ductility and damage severity, with higher ductility in less corroded beams and restricted damage development in heavily corroded ones. RA-AF crack classification and Gaussian Mixture Clustering identified an increased proportion of shear cracks with higher corrosion levels, reducing shear load-carrying capacity. These findings highlight AE-based monitoring as an effective tool for real-time damage assessment in CFRP-strengthened RC beams.

Carbon fiber reinforced polymer (CFRP) has emerged as an effective material for strengthening reinforced concrete (RC) structures due to its high tensile strength, corrosion resistance, and ease of installation. However, in square or rectangular RC columns, stress concentrations at corners hinder the development of uniform confinement, thereby reducing strengthening efficiency. This study presents a comprehensive experimental and theoretical investigation into the performance of CFRP-confined RC square columns with varying anchor configurations. Six full-scale column specimens were tested under monotonic axial compression, each externally wrapped with one layer of CFRP sheet and installed with zero to four CFRP anchors. All columns were chamfered with a 30 mm radius to mitigate corner stress concentrations. The experimental results demonstrated that CFRP anchors significantly enhanced load-bearing capacity and ductility, improved lateral confinement, and modified the failure mechanisms. The specimen with three anchors exhibited optimal performance, with a 51.5 % increase in peak load (from 879.9 kN to 1333.2 kN) and a 29.9 % improvement in ductility index compared to the unconfined control. The failure mode transitioned from brittle global instability to ductile localized damage, accompanied by more uniform hoop strain distribution. However, excessive anchoring introduced stress interference and local cracking, leading to performance degradation. To characterize the mechanical response, a modified stress–strain model was developed, incorporating a reduction factor to account for confinement weakening caused by anchor installation. The model exhibited strong agreement with experimental data (R² > 87 %) in predicting both peak and ultimate stresses. This study provides valuable insights into the mechanical enhancement mechanisms of CFRP anchoring systems and offers a rational design basis for strengthening non-circular RC columns in structural rehabilitation.

This study introduces a novel approach that integrates Acoustic Emission monitoring with fractal analysis to assess and predict damage progression in FRP-strengthened reinforced concrete beams subjected to corrosion-induced deterioration. By combining AE signals with fractal measures, specifically the correlation dimension, the research provides an effective tool for tracking internal damage evolution and offering early-warning indicators for structural health. The developed damage model identifies three distinct stages of damage: initial damage, damage evolution, and sustained growth. The study reveals that corrosion accelerates both the accumulation and rate of damage, with AE ring counts significantly increasing in moderately to severely corroded beams, indicating heightened crack activity and reduced structural capacity. The correlation dimension shows a strong relationship with the degree of damage, with higher values corresponding to more disordered internal damage. The correlation dimension evolves from an initial increase to a decrease as damage progresses, marking the transition from early to advanced degradation. These findings highlight that corrosion not only accelerates damage but also lowers the detection threshold for significant structural damage.

Recycling waste tires for the production of concrete materials with good toughness is a green and economical solution, but the severe deterioration of rubber under high temperatures limits its application in engineering practice. Therefore, to examine the impact of elevated temperature on the fracture characteristics of rubber concrete (RC), three-point bending fracture tests were conducted on RC with five rubber replacement rates and five treatment temperatures. The purpose was to correlate the fracture parameters of RC with the rubber replacement rate and the temperature. Then, by employing the digital image correlation (DIC) technology and microscopic testing methods, the crack evolution trend and the potential mechanism were analyzed in detail. The results indicate that rubber particles can effectively improve the toughness, deformation capacity, and fracture energy of concrete, but have a significant weakening effect on the load and fracture performance. When the treatment temperature is below 400 ℃, rubber particles mainly affect the initiation and propagation of cracks by alleviating the stress concentration phenomenon at the crack tip and improving the crack propagation path. Rubber particles may initiate cracks earlier, but significantly delay their propagation process. When the treatment temperature is above 400 ℃, rubber particles tend to exert a weakening effect on the fracture performance. As the temperature rises, the microstructure of rubber particles gradually changes from a relatively uniform state in close contact with the cement matrix to a fragmented state filled with pores separated from the matrix. This process will lead to severe deterioration of concrete performance. It is anticipated that the findings of this study will provide a theoretical basis for predicting the performance of RC in high-temperature environments.

Damage localization in civil infrastructure, such as large-scale reinforced concrete (RC) pedestrian bridges, is essential for conducting precise maintenance and avoiding catastrophic failures. In this study, multiple one-dimensional convolutional neural networks (1-D CNNs) are developed for automatically extracting implicit damage-sensitive features from the structural raw dynamic responses to localize damage in the pile foundations of pedestrian bridges considering uncertainties such as environmental and operational variations (EOVs) inherent in dynamic responses. For this purpose, transient dynamics numerical computation models are established to simulate the multi-point dynamic response of the structure under different typical damage scenarios, forming the baseline dataset. Then, on-site vibration tests are conducted on the structural prototype. Ambient vibrations of the real intact bridge are considered EOVs and integrated into the baseline dataset, forming the test dataset. Additionally, the intact structural dynamic response with measured EOVs replaces the simulated intact structural dynamic response in the baseline dataset to form a reference dataset. The network architectures based on one-dimensional convolutional layers proposed in this paper are trained on the baseline dataset and reference datasets to obtain baseline and reference models. Subsequently, model performance evaluation is conducted on the test dataset, and the results indicate a significant decrease in the performance of damage models based on a single deep learning when EOVs are present. However, integrating the baseline and reference models achieves zero false negative/positive predictions which is safety-oriented and an exemplary classification accuracy of up to 97.2 %.

This study presents a damage pattern recognition approach for corroded steel beams strengthened by CFRP anchorage system based on acoustic emission clustering analysis. The proposed method includes four steps: acoustic emission signal acquisition, feature extraction, clustering analysis, and damage pattern recognition. Four corroded beams with different corrosion levels and strengthening schemes were tested under four-point bending loading. The acoustic emission signals were collected during the loading process and analyzed using Gaussian mixture model clustering method. The results showed that the collected AE data were analyzed using clustering analysis, successfully distinguishing the distinct damage patterns associated with each mode. The AE signals exhibited distinct characteristics for different damage modes: concrete matrix damage had high-frequency and low-energy characteristics, CFRP-matrix debonding showed intermediate values for all parameters, and CFRP tearing had longer durations, lower peak frequencies, and high-energy characteristics. Besides, the study identified three stages of the damage process: an initial stage with fewer low-intensity AE signals, a damage development stage characterized by an increase in concrete-matrix damage and CFRP – matrix debonding signals, and a continuous damage growth stage with significant AE signals associated with three damage modes. Furthermore, the degree of corrosion significantly influenced the cumulative AE energy of damage modes. Lower degrees of corrosion led to higher cumulative energy from concrete matrix damage and CFRP-matrix debonding. These findings provide valuable insights for understanding the damage evolution and failure mechanisms of CFRP-strengthened corroded beams. The use of AE techniques for damage pattern recognition can enhance the evaluation and design of CFRP anchorage systems, leading to more effective rehabilitation strategies for corroded structures.

This study investigated the relationship between the acoustic emission (AE) signals parameter sequence fractal characteristics and the damage evolution information of corroded reinforced concrete (RC) beams under four-point bending. Strength deterioration behavior and AE data can be obtained by coupling the four-point bending test and the AE monitoring. The results show that AE ringing counts of corroded and uncorroded beams had prominent fractal characteristics. The fractal dimension values of corroded RC beams all showed a fluctuating rise to a peak and then a sharp drop before the failure. The damage index corresponding to the peak point decreases with the increase of corrosion degree. Fractal dimension peak point could be used as an early warning point for corroded RC beams' failure. Moreover, the AE fractal dimension analysis can effectively reflect the pattern of crack development, which have an important value for evaluating the process of corroded RC beams rupture.

This paper presents the results of an experimental study on the flexural behavior of carbon fibre reinforced polymer (CFRP) anchorage system strengthened reinforced concrete (RC) beams under the coupled effects of corrosion damage and sustained loading. The test beams were subjected to combined accelerated corrosion in 5% NaCl solution and sustained loads for 25, 50 and 100 days at 0% and 50% load levels of the virgin beam ultimate load capacity. The failure modes, load carrying capacity, deflection, ductility and strain response of the beams were investigated in detail. The results indicated that CFRP anchorage systems enhanced the yield and ultimate load of the corrosion-damaged beams. The use of CFRP anchorage system restored the ultimate load of corroded beams between 87.6% and 104.8% and the yield load between 81.9% and 92.7% with respect to those of the virgin beam. In contrast, the ductility and energy absorption index suffered a decline. CFRP-strengthened beams showed a reduction of 4.5%–28.9% for the ductility index compared with their counterparts without CFRP anchorage system. Sustained loads resulted in more considerable reductions in load-bearing capacity, greater loss of rebars mass, wider width of corrosion cracks, indicating a significant coupling effect between sustained loading and corrosion damage. Three typical failure modes of the CFRP-strengthened beams were observed and explained in the paper, thus revealing the failure mechanism of CFRP-strengthened beams. In the engineering practice of CFRP anchorage system, the coupled effects of corrosion damage and sustained loading on the strengthened systems should be taken into accountant comprehensively.