Abstract
Recently, various studies for the use of Fe-based shape memory alloy (Fe-SMA) in the construction field have been widely conducted. However, most of the studies for using Fe-SMA are carried out for applying Fe-SMA for strengthening deteriorated structures. However, if Fe-SMA is used as a reinforcement for new structures, the disadvantages of conventional prestressed concrete can be effectively solved. Therefore, in this work, an experimental study was conducted to evaluate the flexural behavior of concrete beams in which Fe-SMA rebars were used as tensile reinforcement. For the study, ten specimens were constructed with the consideration of the cross-sectional area and activation of Fe-SMA rebars as experimental variable. Activation of the Fe-SMA rebars by electrical resistance heating applied an eccentric compressive force to the specimen to induce camber. The camber increased by an average of 0.093 mm as the cross-sectional area of the Fe-SMA rebar increased by 100 mm2. It was also confirmed through the four-point bending tests that the initial crack loads of the activated specimens were 47.6~112.8% greater than those of the nonactivated specimens. However, the ultimate strength of the activated specimens showed a slight difference of 3% to those of the nonactivated specimens. Therefore, it was confirmed that the effect of Fe-SMA activation on the ultimate strength of specimens was negligible.
Highlights
Reinforced concrete (RC) is one of the most important construction materials in practical infrastructure and residential buildings in modern society
Steel reinforcement is the passive reinforcing material because the reinforcement embedded in the concrete begins to limit the crack width and resist the tensile force after the concrete loses tensile strength [2]
When the prestrained shape-memory alloys (SMAs) is activated while restraining the recovery of its plastic deformation, a stress called recovery stress occurs. By using this special characteristic, if a prestrained SMA rebar embedded in concrete is activated, recovery stress occurs because the deformation of the SMA rebar is restrained by the bond force with the surrounding concrete
Summary
Reinforced concrete (RC) is one of the most important construction materials in practical infrastructure and residential buildings in modern society. Post-tensioning tendons permanently bonded to the surrounding concrete by in situ grouting cannot be retensioned even if some prestressing force is lost due to drying shrinkage, concrete creep, and tendon relaxation To compensate for these limitations, researchers have conducted studies to generate the prestressing force by using shape-memory alloys (SMAs) [7,8,9,10]. By using this special characteristic, if a prestrained SMA rebar embedded in concrete is activated, recovery stress occurs because the deformation of the SMA rebar is restrained by the bond force with the surrounding concrete This recovery stress can be applied as compressive force in the prestressed concrete [12]. Beam-type concrete specimens reinforced with Fe-SMA rebars were constructed, and four-point bending tests were performed to experimentally evaluate the flexural behavior of the specimens. The reactivation experiment of Fe-SMA was performed to examine the possibility of retension of the specimens reinforced with Fe-SMA rebars
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