Multi-technical analysis of damage process in GFRP-bar reinforced concrete beam

Glass fibre-reinforced polymer (GFRP)-reinforced concrete can be defined as a next-generation structural material in which the reinforcing secondary phase consists in corrosion-resistant GFRP bars. This study investigates the damage process of GFRP-bar reinforced concrete beams through the acoustic emission (AE) and digital image correlation (DIC) techniques. Precursors to identify impending failure in GFRP-bar reinforced concrete beam are investigated by analysing the AE time series. This study verifies the efficiency of the so-called Method of Critical Fluctuations based (MCF-B) approach, alongside the Debski-Pradhan-Hansen (DPH) index, AE Entropy and Natural Time Analysis, as a failure precursor. The results show that: AE features can indicate the stick-slip behaviour between the GFRP bars and the concrete matrix, as evidenced by the tensile-to-shear crack transition obtained by the Rise Angle to Average Frequency ( RA - AF ) analysis; The MCF-B method effectively identifies the critical region, and its results align with the observations from Natural Time Analysis and AE Entropy Analysis; While b -value exhibits divergent trends beyond this critical region, MCF-B maintains its critical signature, demonstrating the method's robustness; Low entropy indicates a more ordered state in the system, suggesting that the structure is prepared for impending failure; In the experimental tests, the evolution of the DPH index is also calculated, and this parameter can be used to collect complementary information about the AE test. • Novel MCF-B method detects critical failure stages. • AE-DIC synergy reveals GFRP bar-concrete stick-slip phenomenon. • Low-entropy AE signals predict structural criticality. • DPH index identifies local/global instability precursors. • MCF-B, AE Entropy, and Natural Time identify the same critical region.