TY - JOUR

T1 - Iron-based shape memory alloy (Fe-SMA) for fatigue strengthening of cracked steel bridge connections

AU - Izadi, Mohammadreza

AU - Motavalli, Masoud

AU - Ghafoori, Elyas

N1 - Funding Information: The authors gratefully recognize Zurich University of Applied Sciences ( ZHAW ), Winterthur, Switzerland (commissioned by State Secretariat for Education, Research, and Innovation (SERI)) for providing the mobility grant for the bilateral research collaboration with South Asia and Iran 2017–2019. The authors also thank the technicians of the Structural Engineering Research Laboratory of Empa, Switzerland for their exceptional support in performing the experiments. Furthermore, the authors acknowledge the support of Von Roll Deutschland GmbH for providing the GFRP laminates. Funding Information: The authors gratefully recognize Zurich University of Applied Sciences (ZHAW), Winterthur, Switzerland (commissioned by State Secretariat for Education, Research, and Innovation (SERI)) for providing the mobility grant for the bilateral research collaboration with South Asia and Iran 2017?2019. The authors also thank the technicians of the Structural Engineering Research Laboratory of Empa, Switzerland for their exceptional support in performing the experiments. Furthermore, the authors acknowledge the support of Von Roll Deutschland GmbH for providing the GFRP laminates. Publisher Copyright: © 2019 Elsevier Ltd

PY - 2019/12/10

Y1 - 2019/12/10

N2 - Smart iron-based shape memory alloys (Fe-SMAs) are used in this study to retrofit fatigue-cracked riveted connections in steel bridges. The prestressed strengthening technique is found to be an effective approach to overcome fatigue-related damage in riveted connections. Because of the property of Fe-SMAs known as shape memory effect, these alloys can be prestressed without difficulty. The activated (i.e., prestressed) Fe-SMA strips (two 50-mm wide × 1.5-mm thick) are anchored to the flanges of a steel I-beam in either side of the connection. Thereafter, a test setup is specifically designed to examine the SMA-strengthened cracked double-angle connections. First, a static test is performed on the unstrengthened connection without any crack. Subsequently, two high-cycle fatigue (HCF) tests are conducted on a pre-cracked connection. The pre-cracked connection with no strengthening is subjected to fatigue loading with a load ratio of R = 0.1. After practically N=2×106 loading cycles, the crack propagates up to 50% of the connection depth, whereas the fatigue crack growth rate gradually decreases because of the reduction in connection rigidity. Finally, the SMA-strengthened connection is subjected to the HCF loading. It is observed that the fatigue life is substantially enhanced, and the fatigue crack is arrested by the activated Fe-SMA strips.

AB - Smart iron-based shape memory alloys (Fe-SMAs) are used in this study to retrofit fatigue-cracked riveted connections in steel bridges. The prestressed strengthening technique is found to be an effective approach to overcome fatigue-related damage in riveted connections. Because of the property of Fe-SMAs known as shape memory effect, these alloys can be prestressed without difficulty. The activated (i.e., prestressed) Fe-SMA strips (two 50-mm wide × 1.5-mm thick) are anchored to the flanges of a steel I-beam in either side of the connection. Thereafter, a test setup is specifically designed to examine the SMA-strengthened cracked double-angle connections. First, a static test is performed on the unstrengthened connection without any crack. Subsequently, two high-cycle fatigue (HCF) tests are conducted on a pre-cracked connection. The pre-cracked connection with no strengthening is subjected to fatigue loading with a load ratio of R = 0.1. After practically N=2×106 loading cycles, the crack propagates up to 50% of the connection depth, whereas the fatigue crack growth rate gradually decreases because of the reduction in connection rigidity. Finally, the SMA-strengthened connection is subjected to the HCF loading. It is observed that the fatigue life is substantially enhanced, and the fatigue crack is arrested by the activated Fe-SMA strips.

KW - Fatigue crack

KW - High-cycle fatigue (HCF)

KW - Iron-based shape memory alloy (Fe-SMA)

KW - Prestressed strengthening

KW - Steel bridge connection

UR - http://www.scopus.com/inward/record.url?scp=85071975947&partnerID=8YFLogxK

U2 - 10.1016/j.conbuildmat.2019.116800

DO - 10.1016/j.conbuildmat.2019.116800

M3 - Article

AN - SCOPUS:85071975947

VL - 227

JO - Construction and Building Materials

JF - Construction and Building Materials

SN - 0950-0618

M1 - 116800

ER -