Fe-SMA Damped High-Strength Steel Frame for Enhanced Life-Cycle Resilience
Post-earthquake functional recoverability in steel frames can be severely compromised due to low cycle fatigue (LCF) fracture and residual deformation. Both are related to the inherent ductile fracture mechanisms and loading–unloading path of structural steel, issues that are difficult to avoid. Iron-based shape memory alloys (Fe-SMAs), known for their exceptional LCF resistance, have attracted attention in seismic engineering. This study proposes a novel Fe-SMA damped high-strength steel frame (FeSMA-HSSF) system. The use of high-strength steel enables the frame to sustain higher deformations while remaining elastic, providing strong restoring force to control residual drifts. This allows for reduced column sections, resulting in a lighter, more flexible frame with lower seismic force demands. Additionally, Fe-SMA components are integrated to prevent LCF and further enhance self-centering through their high postyield stiffness and anelastic springback unloading path. A series of component tests previously conducted were used to validate the proposed modeling strategy. Following this, system-level analysis was conducted, in which six prototype frames were designed with similar peak drift targets, but differing in damper type (Fe-SMA or Q235 steel) and steel frame material (high-strength or conventional structural steels). Comparative nonlinear time-history analyses and incremental dynamic analyses, combined with Monte Carlo simulations, were conducted to assess key structural responses and expected expected annual loss (EALs). The results confirm the superior residual deformation control capacity of the FeSMA-HSSF system. Additionally, the superior LCF resistance of the Fe-SMA components significantly reduces the collapse probability of the structure. Notably, the FeSMA-HSSF system consistently exhibits lower EAL across all time periods compared with traditional steel systems, making it a more economical and sustainable choice for life-cycle structural design.