Experimental evaluation of seismic performance of interior RC beam-column joints strengthened with FRP composites

•Lack of joint confinement in the majority of per-1970 reinforced concrete (RC) frame construction has resulted in weakening the link between the column and the beam and collapse of the whole structure.•The main focus of this research study is based on five interrelated tasks: (i) design and development of innovative repair and retrofit techniques for reinforced concrete (RC) beam-column joints using advanced FRP composite laminates and pre-cured composite connectors; (ii) experimental evaluation of the different techniques using full-scale testing; (iii) comparison in behavior between as-built and different retrofit specimens; and (iv) conclusions and recommendations for future research.•In this study, a novel technique improved joint shear strength is proposed that resulted in upgrading the joint capacity up to 2.5 times the strength of the as built (unstrengthened) joints.•The use of the hybrid composite connector (HCC) that was developed in this study succeeded in relocating the hinging mechanism to form in the beam span away from the joint region. The ductility of the retrofitted specimen was 2.18 times the control (as-built) specimen. Lack of joint confinement for the majority of pre-1970 reinforced concrete (RC) frame construction has resulted in weakening the link between the column and the beam and collapse of the whole structure. The main focus of this research study is based on four interrelated tasks: (i) design and development of innovative repair and retrofit techniques for reinforced concrete (RC) beam-column joints using advanced FRP composite laminates and pre-cured composite connectors; (ii) experimental evaluation of the different techniques using full-scale testing; (iii) comparison in behavior between as-built and different retrofit specimens; and (iv) conclusions and recommendations for future research. Experimental results confirmed the superiority and success of the proposed strengthening protocols, not only in restoring the original strength capacity, but also in enhancing the overall seismic performance of the deficient joints evaluated in this study including strength and ductility. For example, the use of carbon/epoxy wet layup composite laminates resulted in an appreciable increase of both strength and ductility up to 1.34 and 3.04 times, as compared with as-built specimen, respectively. Also, the proposed technique for enhancing shear strength and rebar bond slippage of the joints using high-strength carbon/epoxy FRP composite