Monitoring Fracture Processes of CFRP-Strengthened RC Beam by Acoustic Emission

Abstract

Strengthening deficient structural reinforced concrete (RC) elements by using externally bonded carbon fiber-reinforced polymer (CFRP) has become a popular method because of CFRP’s superior mechanical properties. However, previous studies have shown that sudden failure due to debonding is the major problem for CFRP-strengthened RC members, especially for the deficient beams. Debonding of CFRP results in sudden fracture of the structural element, and most studies show that it is not easy to predict debonding of CFRP from strain values. In cases that whole surface of the RC member is covered with CFRP strips and U-jacketing is preferred, it is impossible to see the cracks on the surface that may lead to failure of the RC member. Acoustic emission (AE) is known to be a useful method for crack monitoring of an element under load. In this study, in order to understand the behavior of a CFRP U-plate-strengthened RC beam, a specimen strengthened with CFRP U-plate against shear was tested under cyclic loading. AE monitoring was used to obtain types and locations of cracks to correlate them with different load steps and failure mechanisms for the specimen covered with CFRP at its whole beam surface.