Abstract
This paper aims to evaluate potential of an Fe-based shape memory alloy (Fe-SMA) for strengthening civil structures. Mechanical properties of the Fe-SMA were investigated with a direct tensile test, which showed the stress-induced transformation, stress at fracture of the Fe-SMA, and modulus of elasticity. Heating temperature ranging from 110 ℃ to 220 ℃ and pre-straining level ranging from 2% to 8% of the Fe-SMA were considered as variables to provoke a shape memory effect (SME), which generates a recovery stress. The recovery stresses ranged from 207.59 MPa to 438.61 MPa, which plays a role in introducing a pre-stressing force to concrete members. Bonding behavior of the Fe-SMA embedded into a groove with a cement-based mortar filler was investigated to determine the required bonding length to fully develop the pre-stressing force of the Fe-SMA with a near-surface mounted (NSM) strengthening technique. All the tested specimens showed slippage failure and suggested a minimum bonding length of 600 mm. The pre-stressing force applied on the concrete can be calculated with the recovery stress of the Fe-SMA. Based on those test results, the Fe-SMA shows sufficient potential to be used as strengthening material for civil structures.
Highlights
Shape memory alloys (SMAs) are unique and widely known materials that can return to a pre-defined shape when heated above a defined temperature
The aim of this paper is to evaluate the feasibility of the Fe-based shape memory alloy (Fe-SMA) as the strengthening material for civil structures based on thermal mechanical test results
This is because the Fe-SMA shows the plastic deformation and the phase transformation from austenite phase to martensite phase during the activation of the shape memory effect (SME) by resistive electronic heating [10]
Summary
Shape memory alloys (SMAs) are unique and widely known materials that can return to a pre-defined shape when heated above a defined temperature. The pre-defined shape is memorized by changes in temperature or action of stresses. The SMAs were developed from the discovery of Au-Cd alloys with a shape memory effect (SME) by Chang and Read in 1951 [1]. As well as Ti-Ni SMAs publicized by Buehler in 1962 [2], various SMAs such as Cu-Zn-Al alloys, Mn-Cu alloys, and Cu-Al-Ni alloys have been discovered with a SME [3,4,5]. The SME from those SMAs is generated by a thermoelastic phase transformation. The thermoelastic phase transformation known as transformation hysteresis is a transformation behavior of the crystal structure that depends on a change in temperature
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