PSI - Issue 64

E. Choi et al. / Procedia Structural Integrity 64 (2024) 2028–2035 Eunsoo Choi / Structural Integrity Procedia 00 (2019) 000 – 000

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cyclic tests, the performance of the RC column with the SMA bars was compared to that of a conventional RC column with only steel reinforcement. Several significant results were obtained in this study. ▪ The steel rebars in the conventional RC column yielded at the bottom of the column, and this zone, which was the plastic hinge zone, permitted large rotation. However, in the SMA-bar-reinforced RC column, the steel rebars in the coupler yielded and permitted a large rotation, but the SMA bars were in the elastic region; thus, a plastic hinge region developed at the coupling zone. ▪ The steel rebars in the conventional RC column buckled at the bottom of the column because the concrete cover spalled and did not provide lateral resistance, resulting in failure. Therefore, the column failed at a drift ratio of 4.29%. However, in the SMA-bar-reinforced column, the steel rebars did not buckle, even with yielding, and the SMA bars did not yield. Thus, the flexural strength was maintained at a drift ratio of 7.5%, and the column exhibited a more ductile behavior until failure. ▪ The SMA bar reinforced column had a relatively small residual drift of < 0.2% at an applied drift of 5.0%. However, subsequently, the residual drift increased abruptly to 0.92% at a drift of 7.5%. This residual drift significantly affected the self-centering capacity of the column. Thus, its self-centering capacity was 95% at a drift of 5.0% and 87.7% at a drift of 7.5%. ▪ In general, energy dissipation affects self-centering; thus, the energy dissipation of the SMA bar reinforced column was extremely small compared to that of the conventional RC column. The equivalent damping ratio of the conventional RC column was 3% around the yielding drift and increased continuously until failure. The value for the SMA bar-reinforced column decreased to approximately 3% at a drift of 1.75% and became stable at a damping ratio of approximately 3 %. This study investigated the effect of the recovery stress of martensitic SMA bars placed in the plastic hinge zone of an RC column with lateral force-displacement behavior. However, the heating method was inefficient and failed to induce a shape-memory effect. Thus, no meaningful outcome for the recovery stress of the SMA bar on the RC column was obtained. Thus, this should be attempted to obtain significant results. Moreover, this study proposed a smart plastic hinge device to replace the SMA bar-reinforced concrete region. The device can provide self-centering without damaging the device. Acknowledgements This work was supported by a grant of the National Research Foundation of Korea (NRF) funded by the Korean government (MSIP) (Project No. RS-2024-00341914). References Choi E, Nam TH, Cho SC, Chung YS and Park T., 2008. The behavior of concrete cylinders confined by shape memory alloy wires, Smart Materials and Structures, 17-065032. Choi E, Ostadrahimi A, Lee Y, Jeon JS and Kim I., 2022. Enabling shape memory effect wires for acting like superelastic wires in terms of showing recentering capacity in mortar beams, Construction and Building Materials, 319-136047. Narech C, Bose PSC and Rao CSP., 2016. Shape memory alloys: a state of art review, Materials Science and Engineering, 149-012054. Nemat-Nasser S and Guo WG., 2006. Superelastic and cyclic response of NiTi SMA at various strain rates and temperatures, Mechanics of Materials, 38(5-6), 463-474. Raza S, Shafei B, Saiidi MS, Motavalli M and Shaverdi M.,2022. Shape memory alloy reinforcement for strengthening and self-centering of concrete structures-State of the art, Construction and Building Materials, 324-126628. Yoo YI and Lee JJ.,2011. Two-way shape memory effect of NiTi under compressive loading cycles, Physics Procedia, 22,449-454.