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Eunsoo Choi

Hongik University, Korea

Title: Crack-closing of superelastic NiTi SMA short fibers in mortar beams

Biography

Biography: Eunsoo Choi

Abstract

This study was conducted to investigate the crack-closing capacity of super-elastic shape memory alloy (SE SMA) short fibers embedded in mortar beams. For this purpose, NiTi SMA fibers with a diameter of 0.995 mm and a length of 36-42mm were used. Four types of SMA fibers were prepared, namely, straight (RF, reference), L-shaped (LS), double L-shaped (DL) and spear-headshaped (SH). Before the crack-closing test, a pullout test of each type of fibers was conducted to check the interfacial bond strength between the fiber and mortar matrix. The dimensions of the cement mortar beam are 40 mmx40 mmx160 mm (BxHxL). Two SE SMA fibers were placed at the bottom center of the beams along with an artificial crack-guidance-film of 10 mm depth and 1mm thickness. From the hysteretic bending test, this paper evaluated the crack-closing capacity by comparing with the deflections upon loading and unloading. From the pullout test, it was covered that the only SH fiber could generate the super-elastic behavior due to the sufficient bond resistance although there was a small initial slip of fiber. However, the initial slip was critical cause of failure for the crack to be closed upon unloading condition. For the flexural crack control, only a perfect bond between SE SMA short fiber and mortar matrix can generate the super-elastic behavior of the beam.

Recent Publications

  1. Choi E, Kim DJ, Hwang JH, and Kim WJ (2016) Prestressing effect of cold-drawn short NiTi SMA fibres in steel reinforced mortar beams, Smart Materials, and Structures, 085041 (13pp).
  2. Choi E, Kim DJ, Chung YS, Kim HS, and Jung CS (2015) Crack-closing of cement mortar beams using NiTi cold-drawn SMA short fibers, Smart Materials, and Structures, 015018 (11pp).
  3. Choi E, Kim DJ, Youn HJ, and Nam TH (2015) Repairing crack developed in mortar beams reinforced by cold-drawn NiTi or NiTiNb SMA fibers, Smart Materials and Structure, 125010 (13pp).
  4. Choi E, Kim D, Lee JH and  Ryu GS (2017) Monotonic and hysteretic pullout behavior of superelastic SMA fibers with different anchorages, Composites Part B, 108:232-242.
  5. Choi ES, Youn HJ, and Cho BS (2016) Probabilistic seismic performance assessment of lap-spliced RC columns retrofitted by steel wrapping jackets, EARTHQUAKE ENGINEERING AND ENGINEERING VIBRATION, 15:1.