Seismic flexural behavior of concrete connections reinforced with CFRP bars and grids

The corrosion of steel reinforcement in concrete and the resulting deterioration of structures prompted research on fiber reinforced polymers (FRP) as potential reinforcement for concrete members, for use in new construction. FRPs have more favorable advantages for new concrete buildings subjected to seismic loads particularly in corrosive environment. A comprehensive experimental research program was conducted at Ottawa University in Canada to investigate the behavior of FRP reinforced concrete joints to develop design and detailing requirements for FRP reinforced concrete joints under seismic loading. Three large-scale FRP reinforced concrete structural joints were designed, constructed, and tested under cyclic loading. The specimens were T-shape joints consisting of two columns and one beam representing half portion of the first and the second floor of one-bay reinforced concrete frame, or exterior joint of frames with more than one bay. The columns were subjected to the constant axial load and the beams were under reversed cyclic loading. The reinforcement cage was consisted of CFRP bars as longitudinal reinforcement and CFRP grids as transverse reinforcement. The paper presents the details and results of the experimental programs. The results indicate that FRP reinforcement can be used effectively in new concrete buildings. Photographs taken at the selected stages of loading illustrated the performance of each joint. The hysteretic behavior was presented in terms of force–displacement and moment–drift relationships and other hysteretic relationships. Spacing of CFRP grids and arrangement of longitudinal CFRP bars were the main test parameters.