Monitoring structural behaviour of concrete beams reinforced with steel and GFRP bars using acoustic emission and digital image correlation techniques

Abstract

The paper investigates the flexure behaviour and cracking pattern of reinforced concrete beams utilizing steel and GFRP reinforcement using a judicious combination of non-destructive testing techniques of Acoustic Emission (AE) and Digital Image Correlation (DIC). AE parameters including amplitude, number of AE hits, average frequency (AF) and rise angle (RA) successfully correlate with cracking initiation and its progression in steel reinforced concrete (RC) and GFRP RC beams. The plot between AF-RA value effectively classifies the different failure modes in the two types of beams. Simultaneous drop in AF and a significant jump in AE duration at the same instant give a fair indication of critical failure points. AE-XY plots and longitudinal strain profiles obtained from DIC give a real-time representation of progressive AE activity and strains respectively. While AE is proposed to characterize the onset and propagation of the cracking pattern and mode of failure in the beams, DIC assists to visualize the displacement and strain fields while highlighting discontinuities in the displacement field. The work is aimed at developing a health monitoring strategy for RC beams with steel or GFRP bars which is in-situ, non-invasive and provides pre-emptive warning in real-time so that catastrophic failures can be completely avoided.