Papers by Author: Young Oh Lee

Abstract: Acoustic emission (AE) is a powerful nondestructive test that can be used to characterize cracking, growth of cracks, and the degree of damage. This technique is clearly distinguished from other nondestructive techniques as it is a nondestructive test that estimates the degree of damage to concrete. In this study, the AE signals emitted during failure, according to the strength of recycled aggregate concrete specimens was examined, in order to characterize them using existing research results and evaluation theories. In addition, it is demonstrated that AE can be utilized to identify crack source and the mechanism of crack growth, which were monitored using a software program developed from the theory of the location of the source of a microcrack.

Abstract: This study was investigated the evolution of fracture damage of reinforced concrete (RC) beams strengthened in flexure with carbon fiber-reinforced polymer (CFRP) sheets or plates using acoustic emission (AE), and developed an AE monitoring strategy that can determine the structural integrity of RC beams strengthened by external bonding of CFRP sheets or plates. In this study, five beams were used, each with a cross sectional area of 200300 mm2 and length of 2,000 mm. Each specimen was simply supported and subjected to three-point loading. The AE signals were monitored during flexural testing of specimen using four sensors located on the side of each beam. The damage behavior and the microscopic fracture process of the RC beams strengthened with CFRP was evaluated using the AE parameters, such as AE duration time, event and amplitude. The two-dimensional AE source location was successful in measuring crack initiation and propagation in the RC beams strengthened with CFRP.