Monitoring Behaviour of GFRP Strengthened RC Beams Using Acoustic Emission and Digital Image Correlation

Abstract

Nowadays, the maintenance and repair of structural buildings and infrastructure have turned out to be progressively imperative, as these structures age and weaken. By and large, it is more practical to repair, as opposed to replacement of a whole structural segment. The repair work can be done by using Fibre Reinforced Polymers (FRPs) especially Glass Fibre Reinforced Polymer (GFRP) as these are cost-effective and highly ductile preventing sudden failure and improving the load bearing capacity of the structures. In this dissertation, a comprehensive study for the investigation of performance and mechanical behaviour of Reinforced Concrete (RC) beams repaired using GFRP for improving flexure and shear capacities has been attempted with the aid of advanced Non-Destructive Techniques (NDT) of Acoustic Emission (AE) and Digital Image Correlation (DIC). The initiation of cracking in control and precracked GFRP repaired beams in flexure and shear is well picked up as AE parameters of Cumulative AE hits. Sudden increase in the AE hits points towards initiation of microcracking in control concrete. The AE hits slowdown when GFRP wraps are applied both in flexure and shear repaired beams. Another AE parameter of Cumulative Signal Strength (CSS) shows ‘knees’ in the graphs related to sudden release of energy and macrocracking. The ‘knees’ reduce as a result of wrapping. Hence, AE can effectively monitor crack initiation and progression in GFRP repaired RC structures. DIC gives the surface strains and displacements and, is used to monitor the surface cracking in control as well as GFRP wrapped RC beams in flexure and shear. The two advanced NDT techniques in conjunction give both quantitative and qualitative measurement of the mechanical behaviour of precracked RC beams repaired using GFRP when tested in two point loading. To ensure the efficiency of techniques and the accuracy of results obtained from a technique, the results from either of the technique have then been tried to be compared and correlated to each other as well as the static load-deflection curves from linear variable differential transducer.