PSI - Issue 64

Austin Martins-Robalino et al. / Procedia Structural Integrity 64 (2024) 418–425 Martins-Robalino and Palermo / Structural Integrity Procedia 00 (2019) 000 – 000

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1. Introduction The seismic design of reinforced concrete structures with modern design codes are satisfied by approaches which dissipate energy through yielding and permanent deformation of structures. Although this method of design is sufficient to prevent collapse of the structure, the degree of permanent deformation can result in significant repairs if not a complete reconstruction of damaged structures. This has resulted in greater incorporation of residual drift in performance definitions as incorporated by FEMA P-58-1(2018) and ASCE/SEI 41-17(2017). The use of Super-elastic Shape Memory Alloys (SE-SMAs) and their self-centering capabilities have become a promising avenue for addressing these residual drift limits (Fang, 2022). Despite their improved mechanical properties, complications such as lower bond strength to the surrounding concrete material inherent with the smooth surface (Muntasir Billah & Alam, 2016), and increased cost compared to steel reinforcement result in additional work into more optimal utilization in practice. Experimental testing such as those conducted by Abdulridha & Palermo (2017), Almeida et al., (2020); Hoult & Almeida (2022), Tolou Kian & Cruz-Noguez (2018), and Yan et al. (2018) have provided reference experimental data but have been limited to single story scale specimens. The limited number of experimental tests requires that numerical modelling approaches be devised that can accurately capture the behavior and failure modes of these novel SMA-hybrid wall structures. Such numerical modelling would also allow researchers to plan future large-scale experimental studies to complement the current knowledge. 2. Experimental Program The numerical modelling covered herein is based on experimental test results of a hybrid SMA-steel slender shear wall (Wall SWN) and a steel RC companion wall (Wall SWS) tested by Morcos & Palermo (2019). Both walls maintained identical dimensions and an aspect ratio of 2.2 with the walls measuring 1000 mm long, 2200 mm high, and 150 mm thick. Each wall was cast into a foundation block measuring 1600 mm long, 500 mm high, and 1000 mm wide allowing attachment to the testing lab strong floor; while a cap beam measuring 1600 mm long, 400 mm high, and 400 mm wide enabled connection of an actuator which applied reverse cyclic lateral loads. Reinforcement of Wall SWS consisted of two longitudinal curtains with three 10M bars spaced 150 mm in the web region and two 10 M bars in each of the boundary regions. Horizontal reinforcement consisted of 10M bars spaced 150 mm through the entire height of the wall. Additional buckling prevention was provided by 10M ties in the boundary regions with 75 mm spacing from the base of the wall to a height of 1100 mm, after which the spacing was 150 mm. Wall SWN was designed following the same reinforcement layout but replaced the 10M bars in the boundary regions with 12.7 mm diameter Nitinol bars. This change ensured that the SE-SMA bars provided an equivalent tensile force at yielding as the 10M bars present in Wall SWS. These SE-SMA bars measured 1200 mm in length, starting from a depth of 300 mm in the foundation block and terminating 900 mm above the wall base. The ends of SE-SMA bars were coupled to #13 reinforcing steel using headed mechanical couplers. Wall SWN dimensions and reinforcement layout are illustrated in Fig. 1. Both walls were subjected to reverse cyclic lateral loading cycles based on FEMA 461(2007) and ATC-24(1992), further loading protocol and experimental program details can be found in Morcos and Palermo(2019).

Fig. 1. Wall SWN dimensions and reinforcement layout.