Prestressing and self-centering capacity of crimped SMA fibers randomly distributed in mortar beams

초록

This study investigates the prestressing and self-centering behavior of mortar beams reinforced with crimped NiTi shape memory alloy (SMA) fibers, focusing on the influence of the fiber aspect ratios, volumetric ratios, and thermal activation. Rectangular mortar beams measuring 400 mm in length and 50 mm × 50 mm in cross-section (B × H) were fabricated, each containing one and two steel reinforcing bars at the top and bottom, respectively. SMA fibers (diameter = 0.8 mm) made from cold-drawn NiTi SMA wires were produced with three lengths: 20 mm, 30 mm, and 40 mm, corresponding to aspect ratios of 25, 37.5, and 50. Three volumetric fiber ratios were investigated: 0.75%, 1.0%, and 1.25%, resulting in nine different beam types. Each beam was first electrically heated via embedded electrical resistance wires to activate the prestressing effect and was subsequently subjected to cyclic three-point bending tests to evaluate the self-centering performance. Despite the discontinuous distribution of the SMA fibers, a significant prestressing-induced upward deflection was observed. This prestressing enhanced the cracking flexural resistance, but had a negligible influence on the yielding and ultimate flexural capacities. Additionally, the SMA fibers contributed to the self-centering behavior of the beams. Among the tested configurations, beams reinforced with 30 mm-long fibers at a 1.0% volumetric ratio demonstrated the most effective combination of prestressing and cracking delay. © 2026 The Author(s).

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