Experimental testing on reinforced concrete beam-column connections with strand slippage for seismic design

Seismic analysis of concrete structures requires detailed information on how the members and their connections behave under large deformation cycles. Moment frames are commonly used in seismic regions, but achieving code compliance can be challenging when beams are reinforced with steel strands. This is due to the different elongation values at breaking for steel strands (e.g., ε _uk = 3.5% for Y1860 S7) compared to ordinary high-ductility steel reinforcement (e.g., ε _uk = 7.5% for B500 C). In such cases, the novel solution must be verified through calculations and, when possible, experimental testing. In the critical region of reinforced concrete structural members, both proper strength and ductility must be ensured, meaning there must be sufficient plastic rotation capacity. The results of a structural testing program on reinforced concrete beam-column connections for moment resisting frames in seismic regions are reported in this paper. Tests were carried out on scaled specimens at the Technical University of Cluj-Napoca. Five specimens were tested by a protocol consistent with the recommendations of ACI 374.2R-13, respectively ACI T.1.1R-01. Analysis of the recorded data showed that the hybrid specimens (a combination of steel rebars and bonded strands) have comparable hysteretic response and energy dissipation capacity as the reference one.