Uniaxial behavior of pre-stressed iron-based shape memory alloy rebars under cyclic loading reversals

Abstract

Iron-based shape memory alloys (Fe-SMA) have recently emerged as a promising alternative for structural design and retrofitting due to their unique self-prestressing ability. The feasibility of using Fe-SMA rebars, strips, and stirrups for improving the flexural and shear behavior of reinforced concrete beams and slabs has been successfully demonstrated in many experimental investigations. However, existing studies have mostly focused on applications where structural elements are subjected to monotonic loading. On the other hand, tension-compression reversals are mostly experienced by the reinforcement under seismic actions, which makes it necessary to characterize the pre-stress behavior of Fe-SMA under cyclic loading reversals. More specifically, it is important to identify the limit associated with the complete loss of pre-stress of Fe-SMA under tension-compression reversals. Another important research gap is the lack of understanding of the inelastic buckling behavior of Fe-SMA rebars, which is also important for the application of Fe-SMAs in seismic design and retrofitting. Specifically, an understanding of the inelastic buckling behavior is needed for determining the spiral spacing and accurate moment-curvature analysis of cross-sections of concrete columns reinforced with Fe-SMA rebars. This study aims to address these important research gaps by experimentally evaluating the stress-strain behavior of pre-stressed Fe-SMA rebars under cyclic tension-compression reversals. The outcome of this study will facilitate in developing accurate analytical and numerical models for estimating the cyclic response of Fe-SMA rebars and will also assist in developing design guidelines for the use of Fe-SMA in seismic applications.