Flexural Behavior of Self-Prestressed RC Slabs with Fe-Based Shape Memory Alloy Rebar

Abstract

A lot of studies have been conducted to introduce self-prestress to structures using Fe-based shape memory alloys (Fe-SMAs). Technology to introduce self-prestress using Fe-SMAs can resolve the disadvantages of conventional prestressed concrete. However, most of the research to introduce a self-prestress force to a structure using Fe-SMAs has been focused on using Fe-SMAs for the repair and strengthening of aging structures. Therefore, in this paper, a study was conducted to introduce self-prestress into a new structure. To this end, in this paper, an experimental study was conducted to evaluate the flexural behavior of self-prestressed concrete slabs with Fe-SMA rebar. Nine specimens were built with consideration of the amount and activation of Fe-SMA rebars as experimental variables. The Fe-SMA rebars used in the specimens exhibited recovery stress of about 335 MPa under the conditions of a pre-strain of 0.04 and a heating temperature of 160 °C. Activation of the Fe-SMA rebars by electrical resistance heating applied an eccentric compression force to the specimen to induce a camber of 0.208–0.496 mm. It was confirmed through a 4-point bending test that the initial crack loads of the activated specimens were 40~101% larger than that of the non-activated specimens. However, the ultimate loads of the activated specimens showed a difference within 3% from that of the non-activated specimens, confirming that the effect of activation on improving the ultimate strength was negligible. Finally, it was confirmed that repetitive activation of the Fe-SMA rebar could repeatedly apply compressive force to the slab.

Keywords

• shape memory alloy
• recovery stress
• initial crack
• self prestressing
• camber