PSI - Issue 64

M. Saiid Saiidi et al. / Procedia Structural Integrity 64 (2024) 2021–2027 Author name / Structural Integrity Procedia 00 (2019) 000–000

2023

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screw connections, the plastic hinge for one of the columns, and the plastic hinge after the bridge was tested to failure upon removal of ECC. The connection was successful in fixing the column-footing joint and forming the column plastic hinge above the footing. A jack hammer had to be used to remove the ECC because of the presence of the fibers and its high ductility before the condition of the couplers could be examined.

Fig. 1. (left) threaded end and coupler; (middle) NiTi bars in plastic hinge; (right) column base under 10% drift ratios.

Fig. 2. (left) shear screw couplers; (middle) NiTi bars in plastic hinge; (right) column plastic hinge after concrete removal.

The issue of practical SMA bar diameters appropriate for field application was addressed by studies on No. 10 (diameter= 1.27 inch; 32 mm) NiTi bars that were connected to mild steel bars using headed reinforcing bar couplers (HRC) by Tazarv and Saiidi (2015) as shown in Fig. 3. HRC couplers allow for the full bar diameter utilization of SMA bars. No machining is necessary, but the ends need to be flattened by applying heat. The middle photo in Fig. 3 shows the column cage in the plastic hinge zone and the right figure shows the plastic hinge after the column had undergone a 10 percent drift ratio. ECC material was used in this column as well. Similar to the findings from studies of columns with smaller diameter bars, the bars and the couplers provided full integrity at the connections and reduced the residual drift by over 85 percent after a maximum drift ratio of 10 precent.

Fig. 3. (left) HRC couplers; (middle) NiTi bars in plastic hinge; (right) column plastic hinge.