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 SMA bar specimens were connected to the steel rebars using specially devised mechanical couplers, as shown in Figure 2. The upper part of the coupler was connected to the deformed steel rebars, which were connected through one-touch push owing to the action of the spring and wedge inside the coupler. The lower part was for the SMA bar connection, and the SMA bar was driven into the inner threaded part. The upper and lower parts were connected mechanically. Moreover, all shear bolts must be screwed in the construction field, which may increase construction time and cost.

(a)

(b)

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Figure 2. Structure of the mechanical couplers and their photos: (a) schematic of the couplers , (b) coupler of D13 steel rebar, and (c) coupler of D25 steel rebar

3. RC column specimens and experimental program RC Columns

The three RC column models used in this study were identical, except for the longitudinal reinforcement in the plastic hinge zone. The first column incorporated conventional steel reinforcement and normal concrete, and this specimen was labeled as reference RC column (RC-Ref). In the second column, the steel reinforcing bars in the plastic hinge region were replaced with NiTi SMA bars. The third column was identical to the second column, except that the NiTi SMA bars were heated to induce recovery stress. Thus, the second and third columns were labeled as RC-SMA-N and RC-SMA- H, respectively, where ‘ - N’ means non - heating and ‘ - H’ indicates heating. This study prepared the same RC column as in previous studies because it was proven to be suitable for cyclic lateral load tests. The reference RC column (RC-Ref) had a diameter of 400 mm, height of 1400 mm, and aspect ratio of 3.5 (Figure 3(a)) to ensure flexure-dominated behavior. The column was reinforced with 16-D13 longitudinal rebars with a volumetric ratio of 1.61 %. The D10 bars had a spacing of 160 mm for transverse reinforcement (Figure 3(b)). The thickness of concrete cover is 40 mm, and the compressive strength of concrete is 49 MPa. 300 500 1400 2200 /DWHUDO IRUFH 35 35 # 125 60 100 # 125 7@160=1120 Sheath Unit: mm 320 40 40 400 16D13 D10 x 160

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(a) General view

(b) Cross-section

Figure 3. Details of the reference column specimen