Elevated temperature behavior of an iron-based shape memory alloy used for prestressed strengthening of civil structures

• Published in: Construction & building materials Vol. 211; pp. 437 - 452
• Main Authors: Ghafoori, Elyas, Neuenschwander, Martin, Shahverdi, Moslem, Czaderski, Christoph, Fontana, Mario
• Format: Journal Article
• Language: English
• Published: Elsevier Ltd 30.06.2019; Reed Business Information, Inc. (US)
• Subjects: Alloys; Analysis; Bridges (Structures); Design and construction; Elevated and high temperatures; Fe-Mn-Si SMA; Fire exposure; Iron-based shape memory alloy (Fe-SMA); Mechanical properties; Prestressed strengthening; Shape memory alloys; Structural fire engineering; Temperature effects; Thermal properties; Belgium; Fire exposure; Fe-Mn-Si SMA; Iron-based shape memory alloy (Fe-SMA); Mechanical properties; Prestressed strengthening; Elevated and high temperatures; Structural fire engineering
• ISSN: 0950-0618; 1879-0526
• DOI: 10.1016/j.conbuildmat.2019.03.098

[Display omitted] •High-temperature behavior of prestressed iron-based shape memory alloy (Fe-SMA).•Transient total deformation tests simulate fire on Fe-SMA strengthened applications.•Determination of the creep-onset and failure temperatures of the Fe-SMA material.•A creep-onset temperature greater than 500 °C was found for all different cases.•Decrease of both creep-onset and failure temperatures with increasing service loads. Building, bridges and other civil structures usually require at some point in their service life a rehabilitation for reasons such as aging, increased load limits or fatigue. Application of iron-based shape memory alloy (Fe-SMA) members for prestress-strengthening of such structures has been recently introduced. Since civil structures are potentially subject to the fire hazard, the high-temperature mechanical behavior of retrofit materials is of great importance. Therefore, this work aims at providing the first systematic study on the structural fire behavior of Fe-SMA prestress-strengthened structural members. For this purpose, a series of transient total deformation tests was conducted on prestressed Fe-SMA strips of two different thicknesses of 1.5 and 0.5 mm. The transient lab-tests were performed to determine the creep-onset and failure temperatures of the Fe-SMA strips at different service load levels of 0, 80 and 240 N/mm2 and heating rates of 5, 15 and 50 °C/min. The results showed that (1) a creep-onset temperature greater than 500 °C was observed at all different service load levels and heating rates; and (2) both the creep-onset and failure temperatures decreased with increasing service load levels. Finally, a simple engineering model was developed to estimate the fire-induced prestress loss in Fe-SMA members of retrofitted civil structures.