Analytical and experimental evaluation of seismic performance of interior RC beam-column joints strengthened with FRP composites

The main focus of this research 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) Numerical simulation of the as-built and retrofitted joints using Finite Element (FE) modeling analysis; (iv) Comparison between experimental results and FE numerical analysis; and (v) Conclusions and recommendations for future research.;The experimental results confirmed the superiority and success of the proposed strengthening protocols not only in restoring the original 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 lay-up 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 highstrength carbon/epoxy FRP composite laminates and advanced composite connectors achieved significant results. The novel technique improved the shear strength of the joint 2.5 times the control deficient specimen. The use of composite connector has relocated 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. The FE model was successful in predicting the behavior of the experimental results. The tolerance in results was within 13% difference between the experimental and numerical analysis.;It is anticipated that the results of this pioneering study provide alternative innovative reinforcing and strengthening methodologies to enhance the construction and repair methods for reinforced concrete moment frame structures. These innovative techniques contribute to higher reliability and safety as well as lower construction and repair costs of RC moment frame structures. It is also anticipated that the proposed strengthening protocol can also be applied to cover similar details such as base-column, pile-cap as well as T- and knee bridge joints.