The behavior of concrete cylinders confined by shape memory alloy wires

Abstract

The purpose of this study was to propose a new method to confine concrete cylinders or reinforced concrete columns using martensitic or austenitic shape memory alloy (SMA) wires. The prestrained martensitic SMA wire was wrapped around a concrete cylinder then heated by a heating jacket. In the process, the confining stress around the cylinder was developed in the SMA wire due to the shape memory effect, which can increase the strength and ductility of the cylinder under axial compressive load. For austenitic shape memory wires, the wires were prestrained as they were wrapped around the concrete cylinders on which post-tensioning stress was generated. In this study, martensitic and austenitic SMA wires of 1.0 mm in diameter were used for the confinement. Recovery tests were conducted on the martensitic wire to assess the recovery stress. Also, a superelastic behavior test was performed for the austenitic wire. The confinement by martensitic SMA wires increased the strength slightly and greatly increased the ductility compared to the strength and ductility of plain concrete cylinders. The austenitic SMA wires showed a similar effect on concrete cylinders to that of the martensitic wires. This study showed the potential of the SMA wire jacketing method to retrofit reinforced concrete columns and protect them from seismic risks.

Seismic protection of lap-spliced RC columns using SMA wire jackets

“…In addition, the application of superelastic SMA bars relocated the plastic hinge from the face of column to a distance of a half of the beam depth, so that the columns were protected from seismic risks. The SME exhibited by SMA can provide external confinement to increase the ductile behaviour of concrete (Choi et al, 2008). The technique was illustrated for RC columns and estimated the effect of confinement analytically (Andrawes and Shin, 2008).…”

New SMA Short Fibers for Cement Composites Manufactured by Cold Drawing

“…The SME phenomenon is well explained in Figure 1(a) using a stress-strain-temperature diagram in three dimensions (Choi et al, 2008). An SMA is deformed under martensitic phase (I), and then unloaded (II) followed by heating them above the temperature A f (III), which is a temperature to complete austenite transformation.…”

“…Diagram for recovery and residual stress due to shape memory effect (Choi et al, 2008) An elongated SMA wire shows a reduction of diameter or thickness due to the Poisson effect. During the SME procedure, the reduced diameter or thickness of a wire is also recovered because of the Poisson effect.…”

Advanced fibre-reinforced polymer (FRP) composite materials in bridge engineering: materials, properties and applications in bridge enclosures, reinforced and prestressed concrete beams and columns

“…Three confinement techniques were considered: the use of (1) steel, (2) FRP composites, and (3) Shape Memory alloy (SMa) wire jackets. Choi et al (2008Choi et al ( , 2010 had investigated the possibility of using the SMA technique to confine concrete; it was shown to be effective. However, the three independent methods were not appropriate for plain concrete piers supporting OSPG bridges as the piers required reinforcement in the longitudinal direction as well as in the lateral one.…”