Use of DIC and AE for Monitoring Effective Strain and Debonding in FRP and FRCM-Retrofitted RC Beams

Effective strain in composites as well as potential rupture and debonding of composite materials play a crucial role in predicting the strength of retrofitted reinforced concrete (RC) beams. However, only limited experimental data on these phenomena is available, mainly due to the inadequacy of traditional monitoring systems. This paper presents a comparative analysis of different instrumentation for monitoring retrofitted RC elements. In particular, the paper addresses beams retrofitted with composite materials (FRP and FRCM) and considers strain gauges (SG), fibre-optic Bragg grating (FBG) sensors, linear variable differential transformer (LVDT), digital image correlation (DIC) and acoustic emission (AE) sensors for monitoring strain, displacement, cracking and debonding. Experiments on six beams were carried out and the measured data from the monitoring devices was compared. The accuracy of DIC for strain and displacement monitoring, as well as the ability of using AE for detecting cracks and debonding, were shown to match the performance of traditional methods, with the added benefit of providing full-field and depth monitoring. This is of particular interest for composite-strengthened concrete elements in which the accurate measurements of effective strain and debonding of the composite material can lead to developing more precise design formulae. © ASCE 2016. The published version is available in the ASCE Civil Engineering Database (http://cedb.asce.org)