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.

The Utilization of Shape Memory Alloy as a Reinforcing Material in Building Structures: A Review

“…Yeon After investigation, few studies on SMA-reinforced slab members were found. Yeon et al [141] conducted a flexural test on unidirectional RC slabs with Fe-SMA reinforcement as the tensile steel bars and evaluated the influence of the recovery stress of Fe-SMA reinforcement on the flexural performance of the slabs. The results showed that the number and width of bending cracks decreased with Fe-SMA reinforcement, which was mainly due to the prestressing effect of the recovery stress generated by the Fe-SMA reinforcement.…”

Study on the Effect of Solid Solution Treatment on the Bending Fatigue Property of Fe-Mn-Si Shape Memory Alloys

“…Its application in the civil engineering and construction industries is to use shape memory effect to generate prestress inside the structure. The prestressing of Fe-Mn-Si shape memory alloys can enhance the flexural strength and cracking stress of concrete structures [16][17][18]. When Fe-Mn-Si shape memory alloys are applied to prestressed structures, researchers pay more attention to the magnitude of the prestress generated by the material.…”

Finite Element Analysis of Reinforced Concrete Beams Prestressed by Fe-Based Shape Memory Alloy Bars

“…In addition, in the method of introducing prestress using SMA, it is possible to simply introduce prestress to the concrete member only by heating SMA without an anchoring device and jacking device, unlike the conventional prestress method. Moreover, unlike conventional bonded prestressed concrete, concrete members to which prestress is introduced through SMA can recover the initial recovery stress through simple reactivation even if recovery stress is lost due to various causes such as drying shrinkage and creep of concrete, and SMA relaxation [23].…”