ANALYTICAL INVESTIGATION ON THE SMA-BASED RETROFITTING OF SUBSTANDARD RC FRAMES

Shape memory alloys (SMAs) have been getting attention in the last two decades as smart and innovative materials in many civil applications due to their extraordinary material characterizations. The main ability of these materials is to provide recovery process from inelastic deformations by returning to its undeformed position. A significant portion of the existing buildings is at risk because of improper design and construction practices contrary to the modern earthquake resistant design principles. In this study, analytical models were constructed for three 2/3-scaled one-bay and one-storey substandard RC frames tested under quasi-static displacement-controlled reversed-cyclic loading. Two of the RC frames were retrofitted with superelastic (SE) Cu-Al-Mn shape memory alloy (S-2-CuAlMn) and conventional steel bars (S-3-Steel) whereas one of the experiments was performed for as-built specimen (S-1-REF). On the one hand, the results showed that analytical models generally match well with the experimental ones in terms of global re-centering behavior, ultimate load, envelope curves and ductile behavior of RC frames. Also, essential reduction in the residual deformation of the RC frames was clearly observed following the self-centering behavior in the hysteretic curves. On the other hand, fracturing point of SE Cu-Al-Mn bars and the narrow band hysteretic behavior during unloading process cannot be fully represented due to an assumption of constant modulus of elasticity in both austenitic and martensitic phases of SMA material in the analytical model.