Experimental Investigation of Actively Confined RC Columns Using Iron-Based Shape Memory Alloy Spiral Stirrups

Abstract

Shape memory alloys (SMA) can be employed as prestressing components in the form of bars and strips in new reinforced concrete (RC) members or for reinforcing existing RC constructions because of their shape memory effect. Early research focused on retrofitting concrete components with external SMA spirals, but this technology has not been extensively used in new building. Civil engineering constructions can benefit from the development of a more affordable iron-based shape memory alloy (Fe-SMA). A good form recovery stress (prestress force) and high elastic stiffness describe this Fe-SMA. As an added benefit, it is less expensive in terms of raw materials and easier to manufacture than nickel-titanium alloys (NiTi). Industrial production of Fe-SMA strips has just recently begun. In this research under an axial compression force, three circular columns are tested experimentally. The confinement of reinforcement-type steel strips and (Fe-SMA) spiral stirrups, main reinforced steel bars, as well as numerical simulation using finite elements, are all researched. The (Fe-SMA) spiral stirrups are considered strengthening techniques, internal and external confinement. Axial compressive load, load-displacement curve, and strain-reinforcement bars are all terms used to define the cause of failure. Strengthening by Fe-SMA stirrups external reinforcement maximum gains in compressive strength of around 69.99% for stirrups steel reinforcement columns and 51.64% for Fe-SMA stirrups internal reinforcement.