Failure Behavior of CFRP-Strengthened Reinforced Concrete Beam-Column Joints under Reversed-Cyclic Lateral Loading: Mechanical and Acoustic Emission Observations

This paper investigates the failure behavior of reinforced concrete beam - column joints (BCJs) strengthened with different schemes of carbon fiber reinforced polymer (CFRP) and the factors causing fracture. In the study, five reinforced concrete BCJ specimens having 1/1 geometric scale were tested under reversed-cyclic lateral loading. While one of them was used as a reference, the others were strengthened with CFRP. Damage development of the specimens was simultaneously monitored by the acoustic emission (AE) technique. Both the structural and AE data were combined to reveal the effects of CFRP strengthening schemes on the fracture pattern ana damage progress. Quantities, scales, levels, and locations of the damage show that the scale of the damage decreased with all strengthening procedures and that the strength and other mechanical properties improved. In addition, extending the strengthening material to the columns and beams contributed more to the structural behavior in terms of strength, energy dissipation capacity and rigidity as well as crack development. Although strengthening by wrapping only the beam and column extensions of the joint can give the desired performance in terms of load bearing capacity, it is not recommended owing to an increased risk of major shear cracks.