Enabling shape memory effect wires for acting like superelastic wires in terms of showing recentering capacity in mortar beams

Abstract

Superelastic shape memory alloy (SMA) wires embedded in mortar beams show a recentering capacity, however, shape memory effect wires can provide a prestressing effect after inducing phase transformation. In this study our goal is to empower shape memory effect wires to show recentering capacity by designing a new wire configuration. These wires will thus be able to achieve both a prestressing effect and a recentering capacity in mortar beams. To this end, various shapes of martensitic SMA wires, including as-received, crimped, dog bone, and anchoring reinforced crimped wires, were employed to examine the potential of displaying recentering capacity while preserving the prestressing force in mortar beams. Several monotonic and cyclic three-point bending tests were also conducted to investigate the crack-closing effect, as well as the load bearing of the specimens. To evaluate the effect of temperature and heating procedure, two different methods, namely, a hot air gun and electric current heating, were used to induce phase transformation in shape memory effect wires. The results generally show that for two types of as-received and dog bone wires, the displacement recovery ratio have been reduced about 65% and 74%, respectively, however, for the crimped wire and anchoring reinforced crimped wire, this ratio is almost the same. More importantly, when the results of displacement recovery ratio of crimped wires heated by electrical heating are compared with the available experimental data for superelastic SMA bars, proves the great ability of SME wires to fulfill recentering capacity.