Crack type analysis and damage evaluation of BFRP-repaired pre-damaged concrete cylinders using acoustic emission technique

Abstract

Fiber-reinforced polymer (FRP) composites have been widely used in the retrofitting of concrete columns after earthquakes. However, FRP composites prevent traditional field inspection techniques from observing concrete cracks inside the FRP-retrofitted columns caused by external loading. In the present study, axial compressive loading tests were performed on basalt FRP (BFRP)-repaired pre-damaged cylindrical concrete accompanied by real-time acoustic emission (AE) monitoring. Three damage stages of BFRP-jacketed cylinders were defined based on the proposed strain energy-based damage index and predicted using fractal theory. The conventional RA value-average frequency (RA-AF) analysis and Gaussian mixture model (GMM) analysis effectively revealed the evolution of crack types of BFRP-repaired pre-damaged cylinders. GMM method verified the effectiveness of the RA-AF analysis and provided a better approximation for the classification of crack types. As the pre-damage degree increased, RA value increased and AF value decreased. The shear cracks developed significantly at the severe damage stage in two-layer BFRP-jacketed cylinders.