Description
Iron-based shape memory alloys (Fe-SMAs) have gradually become a research hotspot in the field of structural strengthening due to their convenient application of prestress. However, unlike traditional prestressing methods, it is challenging to intuitively determine the effective prestress of Fe-SMAs using instrumentation. This study conducted bending tests on eight concrete T-beams near-surface mounted (NSM) with Fe-SMA bars to elucidate the effects of Fe-SMA reinforcement ratios (0%, 1.6%, 2.5%) and activation temperatures (non-activated, 200 ℃, 300 ℃) on flexural performance. The effect of zero preload on the recovery stress was investigated, leading to the proposal of a formula for calculating effective prestress. The results indicate that increasing the Fe-SMA reinforcement ratio positively influences load at service limit state, ultimate load, and post-cracking stiffness. The enhancement in post-yield stiffness is particularly notable due to the stress-strain hardening effect of Fe-SMAs. The effective prestress of Fe-SMAs is influenced by both the preload of Fe-SMA and crack closure of specimens; as the preload increases, the recovery deformation capacity of the Fe-SMAs decreases. The theoretical values of anti-arch calculated using the proposed model closely match the measured values. Fe-SMA achieved rapid prestressed NSM strengthening and demonstrated favourable strengthening effects.
