Cyclic load behaviour of reinforced concrete columns with SMA and ECC in the critical regions

Design techniques that can reduce the residual deformation are necessary to ensure that reinforced concrete (RC) structures function properly after earthquakes. The use of superelastic materials in the plastic hinge region permits the structure to undergo large displacements with less residual displacement upon load removal. The present study deals with the incorporation of two innovative materials, super-elastic shape memory alloy (SMA) and engineered cementitious composites (ECC), in the critical region or plastic hinge zone of the column. This numerical study focused on the seismic performance evaluation of full-scale RC circular cantilever columns reinforced with two types of nickel-based and two iron-based SMA and ECC in the critical region. The specimens were subjected to a reverse cyclic lateral loading with a constant axial load at the top. The performance of these hybrid columns was compared with those of conventional steel-reinforced columns and steel-reinforced columns with ECC in the critical region. The results of the study revealed that the columns reinforced with SMA and ECC in the critical region showed negligible residual displacement compared to the normal and ECC columns. The column reinforced with the FeNCATB SMA and ECC in the critical region showed better behaviour in terms of a higher load-carrying capacity and ultimate displacement/rotation under a higher drift ratio. From the longitudinal rebar strain profile, it is evident that this hybrid column specimen did not reach the elastic strain limit at a higher drift ratio than the other specimens.