Flexural Behavior of Hybrid-Reinforced Concrete Exterior Beam-Column Joints under Static and Cyclic Loads

This study presents an experimental investigation of the flexure behavior of exterior beam-column joints made from hybrid concrete (normal concrete (NC) and reactive powder concrete (RPC)) or hybrid reinforcement (steel and carbon fiber reinforced polymer (CFRP) bars internally or externally by near surface mounted (NSM) technique). Nine hybrid-reinforced concrete beam-column joint specimens under the effect of static or cyclic loading were studied and tested within three test groups. Several variables that affect the behavior of the beam-column joint region are investigated such as: type of loading (static or cyclic), type of hybridization (concrete hybridization or reinforcement hybridization), and area of concrete hybridization. The results showed that using RPC as a replacement concrete at different areas of beam-column joint under static loading improved the ultimate load capacity and first cracking load to about 8–32% and 20–60%, respectively, compared with the reference NC joint with increase in the ductility of about 6–14%. Moreover, using the same technique under cyclic loading condition showed an increase in the ultimate load of about 39%, with improvement in the cumulative ductility of about 12% compared with the reference NC joint. On the other hand, using CFRP bars as (internal or external) hybridization system (33% of main reinforcement) under static loading caused increments of ultimate and first cracking loads of about 11%, 8% and 0%, 30%, respectively compared with the reference steel reinforced joint; while the ductility ratio increased about 36%, 5%, respectively. Moreover, the internal hybrid reinforcement system exhibited a decrease in the ultimate load of about 15% and reduction in the cumulative ductility of about 40% under cyclic loading.