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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the self-centering capacity of the column. In the conventional RC column, the residual drift increased after an applied drift of 1.0%, which corresponded to the yield drift; thus, the residual drift of the RC-ref column was mainly caused by the yielding of the steel rebar. The residual drift from a 1.75% drift exhibited an almost linear relationship with the drift, with a slope of 0.876. In the RC column with SMA rods, the residual drift did not exceed 0.2%, with a maximum drift of 5.0 %. After a 5.25% drift, the residual drift increased with a relatively high slope and reached 0.92% at a maximum drift of 7.5%. The upper part of the plastic-hinge zone in the RC-SMA-N column was completely crushed at a drift of 5.25%. It was conjectured that concrete crushing could induce a greater residual drift.

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(b) Self-centering capacity

(a) Residual drift

5

RC-Ref RC-SMA-N

100

4

80

RC-Ref RC-SMA-N

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60 DRR (%)

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Residual drift (%)

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40

0

0 1 2 3 4 5 6 7 8

0 1 2 3 4 5 6 7 8

Drift ratio (%)

Drift ratio (%)

Figure 8. Residual deformation and displacement recovery ratio

Figure 9(a) shows dissipated energy estimated from the hysteretic curves. In general, energy dissipation capacity is inversely proportional to the self-centering capacity. Thus, the RC-Ref column exhibited a higher dissipated energy than the RC-SMA-N specimen. In the RC-Ref column, the dissipated energy increased abruptly after a drift of 1.0% and decreased after a failure drift of 4.25%. However, the RC-SMAA-N specimen exhibited an almost linear increase in energy dissipation until the end of the test. Figure 9(b) shows the equivalent damping ratios of the two columns, calculated using the following equation: = 41 (1) where E S and E D are the elastic and dissipated energies of each hysteretic curve, respectively. The RC-Ref column exhibited a damping ratio of 2.97% at a drift of 1.0%, which increased to 11.6% at the failure drift. The RC-SMA-N column initially exhibited a damping ratio and decreased to 3.02% with the drift of 1.75%. After that, its damping ratio became almost stable with approximately 3.0% until the end of the test.

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(a) Energy dissipation

(b) Damping ratio

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RC-Ref RC-SMA-N

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Damping ratio (%)

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Dissipated eneregy (kJ)

RC-Ref RC-SMA-N

0 1 2 3 4 5 6 7 8 0

0 1 2 3 4 5 6 7 8 0

Drift ratio (%)

Drift ratio (%)

Figure 9. Energy dissipation and damping ratio

5. Conclusions In this study, martensitic SMA bars were first applied in an RC column to improve its self-centering capacity. The SMA bars were mounted only in the plastic hinge region using specially designed couplers. Through lateral reversed