Experimental study on seismic performance of prefabricated UHPC-connected GFRP/steel hybrid reinforced columns

In this paper, a novel reinforcement method is suggested to enhance the durability and ductility of assembled prefabricated columns. The proposed approach substitutes the outer steel reinforcement with glass fiber reinforced polymer (GFRP) bars and uses an interior concrete core confined with helical steel hoop reinforcement. In addition, the potential plastic hinge region of the precast columns is reinforced with ultra-high-performance concrete (UHPC) poured in a mortise and tenon joint, which effectively reduces the length of the lap-spliced joint. The seismic performance of the precast columns using the new reinforcement approach was evaluated by testing three monolithic and three precast specimens under reciprocating cyclic loading. The findings indicate that optimizing the spiral concrete core diameter in the new reinforcement method enhances the load-bearing capacity (31.7 %), energy dissipation capacity (4.4 %), and ductility coefficient (41.7 %) of the specimen. The precast specimens with the UHPC connection effectively relocate the damage away from the post-cast connection area, resulting in improved post-peak load stability and ductility. Furthermore, prefabricated specimens had superior seismic performance over the monolithic specimens; the load-bearing capacity, ductility coefficient, initial stiffness, and energy dissipation capacity of the 200-mm core column specimens with UHPC connections were improved by 9.0 %, 40.7 %, 46.9 %, and 50.8 %, respectively. The plastic hinge length of the new prefabricated columns can be estimated using the corresponding monolithic concrete members. Finally, a load-bearing capacity equation and degenerated three-linear restoring force model are proposed and validated.