Acoustic Emission (AE) based health monitoring of RC beams strengthened with mechanically anchored hybrid Fiber Reinforced Cementitious Matrix (FRCM) system

The debonding between fabric and matrix/substrate hampers the strength and durability of fiber- reinforced cementitious matrix (FRCM) strengthened elements. One of the ways to improve the performance is to use mechanical anchorages. However, damage mechanisms associated with such systems are complex, and structural health monitoring of such systems is quite challenging. While earlier studies have concentrated on monitoring the health of FRCM coupons using acoustic emission techniques, they did not account for the effect of impregnation or use of mechanical anchorages. Also, very few studies are available on the health monitoring of full-scale FRCMstrengthened specimens. The current investigation employs AE-based health monitoring to classify the damage characteristics of reinforced concrete (RC) beams strengthened with FRCM. Two strengthening strategies, with and without mechanical anchorages, are employed. The non- anchored system involves conventional strengthening using two layers of pre-impregnated fabric, while the mechanically anchored method utilizes pre-impregnated fabric and a distributed anchorage system. The AE data is then analyzed using several parameters correlated with the digital image correlation (DIC) technique. Trends of sentry function, historical index, and cumulative signal strength (CSS) CSS ) provide insights into major event occurrences and changes in the underlying damage modes. Three different b-values indicate a transition from micro to macro cracks during different loading stages. On the other hand, frequency content and RA-AF analysis are employed as qualitative tools to identify the source and type of damage. The strengthened RC beams with mechanical anchorages exhibited a 20.9 % increase in flexural capacity compared to those without, as evidenced by the AE parameters and DIC techniques. Overall, the study revealed that acoustic emission health monitoring could effectively evaluate the overall condition of the strengthened system, even with the complexity of a multi-part composite system.