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.

The next generation of acoustic emission (AE) applications in concrete structural health monitoring (SHM) relies upon a reliable and quantitative relationship between AE measurements and corresponding AE sources. To achieve this, it is a prerequisite to accurately model the whole AE process that is a multiscale coupling process between local material fracturing and induced elastic wave propagation at structural level. Such a complex process, however, cannot be well addressed in currently available modelling methods. To fill this research gap, this study proposes a lattice modelling approach that achieves for the first time the explicit simulation of complete waveforms of transient AE signals induced by concrete fracture. The proposed approach incorporates an explicit time integration technique with a novel proportional-integral-derivative (PID) control algorithm for reducing spurious oscillations and a Rayleigh damping-based calculation and calibration method for the attenuation of AE waves. In this paper, the proposed lattice modelling approach is implemented to simulate the concrete Mode-I fracturing process in a three-point bending test. Besides the mechanical behaviors and AE hit number, a comparison was conducted between numerically and experimentally obtained AE waveforms. The AE waveforms and their attenuation characteristics simulated by the proposed lattice modelling method turn out to be comparable to experimental results. The proposed approach is of significance for a deep understanding of AE-related fracture mechanisms and a more reliable application of AE technique.

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.

To date, there is no comprehensive approach available that can explicitly model the complete transient waveforms of acoustic emissions (AE) induced by fracture processes in brittle and quasi-brittle materials like concrete. The complexity of AE modelling arises from the intricate coupling between the local discontinuity of material fracturing and the global continuity of elastic wave propagation in solids. Among others, the lattice type models are promising approaches, as they are known to be a matured modelling approach to simulate the fracturing process in concrete-like materials. Nevertheless, like other discrete element methods (DEM), they are currently limited to describing the number and rate of AE events (broken elements) in the fracture process and cannot explicitly model wave generation and propagation. In this study, we propose a lattice modeling framework to simulate the propagation of complete waveforms of fracture-induced AE signals in concrete. A proportional-integral-derivative (PID) control algorithm is incorporated in an explicit time integration procedure to reduce dynamic noise from spurious oscillations. Additionally, a Rayleigh damping-based calculation method and corresponding calibration procedure are proposed to model the attenuation of AE signals due to material damping. Using the developed approach, we systematically investigate the feasibility of lattice models for elastic wave propagation simulation, the dependence of lattice mesh sizes and the choice of numerical damping parameters. These results lead to a systematic framework which can be employed in simulating wave propagation with attenuation using DEM models in general including lattice models.

Assessment of existing reinforced concrete (RC) structures after an earthquake is a challenging task that must somehow relate qualitative and quantitative observations in the plastic hinge regions and the associated residual deformation capacity of damaged structures. Having an estimate available for the remaining drift capacity will result in more economical and informed decisions regarding demolition or strengthening options. This study aims to develop a practical methodology to estimate the maximum drift demand of an RC column based on the residual crack width. For this purpose, fiber-based frame elements are used to model the RC column considering appropriately concrete behavior in compression and tension stiffening effects. Afterwards, the accuracy and reliability of the proposed methodology are demonstrated by validating the computational approach with two cyclic experimental results from literature and new test data for a one-bay one-story RC frame conducted within the course of this study. A comprehensive parametric study is performed for RC columns with different axial loads, longitudinal and transverse reinforcement ratios, and ground motions to exhibit the stochastic behavior. The study identifies the axial load ratio as the predominant parameter. Key findings include strong correlations between maximum drift ratios and total residual crack widths, as well as maximum compressive strains, with regression analysis yielding equations for accurate drift ratio estimation. Simple predictive models are proposed to estimate the maximum deformation demands based on observed residual crack widths. Residual cracking exceeding 5 mm poses significant risk for the columns with axial load ratios above 0.4, with 90% probability of exceedance 2% drift ratio.

Significant infill wall damage in reinforced concrete frame buildings was observed in the past earthquakes. A vast number of numerical approaches have been proposed to estimate the non-linear behavior of infilled frames at different scales. Mesoscale lattice models were successfully used in the past to simulate the behavior of reinforced concrete member response. In this study, two-dimensional mesoscale lattice approach with an extended calibration technique was consistently applied to simulate the response of unreinforced Aerated Autoclaved Concrete (AAC) masonry infilled reinforced concrete frames. Two AAC infilled walls were tested for the purposes of this study. The objective of the tests were to investigate the effect of infilled wall-frame interaction with and without openings and validate the proposed numerical approach. In addition to the tests conducted, two tests were used from the literature for further validation. The maximum error of load capacity estimation from the simulations was less than 15% for all the examined tests. The proposed lattice model was capable of estimating crack propagation in the infill walls with reasonable accuracy. The frame-infill wall interaction was successfully simulated with providing a realistic representation of strut formation. Finally, a parametric study was conducted to examine contact length and strut width as a function of lateral deformation. The results show that the infill wall-frame contact length is significantly dependent on the lateral deformation demand levels and properties of interaction region.