Experimental cyclic response of heat-damaged RC beam-column joints strengthened with CFRP strings

Abstract

Reinforced concrete (RC) buildings may be subjected to high temperatures during their service life, which causes significant deterioration in the mechanical and physical characteristics of several structural members (i.e., joints), making it necessary to upgrade their overall performance to withstand the additional stresses. Therefore, the effectiveness of carbon fiber reinforced polymer (CFRP) strings used as near-surface mounted (NSM) reinforcement in restoring the structural performance and minimizing the failure mechanism of heat-damaged RC beam-column (B-C) joints is examined in this study through experimental work. The experimental research consists of twelve RC beam-column joint sub-assemblages divided into three groups: four joints were kept at room temperature, four were heated to 400 °C, and four were heated to 600 °C. Three joints from each batch were tested under a quasi-static cyclic load after adding one, two, or three strings of CFRP reinforcement. The cyclic response of joints was evaluated by determining the ultimate load capacity in pulling and pushing and its corresponding lateral displacement, energy dissipation, displacement ductility, and stiffness degradation. The experimental results showed that the upgraded joints with CFRP strings experienced a significant increase in energy dissipation, initial stiffness, displacement ductility, and ultimate load capacity in pulling and pushing over reference joints.