Cyclic load behavior of PC and CIP interior beam-column connections in moment resisting frames

The use of precast concrete (PC) in construction has many benefits, including improved product quality, shorter construction periods, and lower construction costs. However, to design middle-to high-rise PC structures, seismic safety must be ensured. In particular, the structural behavior of beam-column joints, which are typical moment-resisting frames, is determined by shear and bond mechanisms under seismic loads. However, shear elements and bonds are very vulnerable to cyclic loading, so the joint must always remain within the elastic zone. It is necessary to clearly evaluate whether PC beam-column joints have the performance and usability to be applied as a monolithic structural system (CIP). In this study, eight CIP and PC specimens were fabricated with different moment resisting frames (intermediate and special) and failure modes (B, BJ) as variables. The strength, ductility, strength degradation, and energy dissipation of the PC joints were evaluated and compared to those of CIP joints. Furthermore, the structural behavior of the joints after plastic hinging of the beams was evaluated. The experimental results showed that the PC specimens exhibited the same behavior as the CIP specimens in terms of crack pattern and story shear-drift ratio. However, in terms of ductility, the S-series showed about 10-20 % improvement in ductility for PC compared to CIP, and similar trends in energy dissipation capacity. The strain inside the joint increased at the story drift ratio of 2.0 % after the plastic hinging of the beam, and the bond stress in the center of the joint panel zone tended to be higher in the PC specimen than in the CIP specimen. In addition, the shear strain in the joint panel zone tended to be higher in the special moment resisting frame than in the intermediate moment resisting frame, and an inverse relationship with the displacement ductility index was confirmed.