Background: This research aims to provide a comprehensive and comparative evaluation of the seismic performance of special steel moment frames designed using conventional S235 steel, and shape memory alloys (SMA). The necessity of this study lies in accurately identifying the influence of different mechanical properties of steels such as yield strength, stress–strain behavior, ductility, and energy absorption capacity on structural performance indicators under severe earthquakes.
Methods: In this study, numerical models of special steel moment frames were developed using nonlinear analysis software, and their behavior under seismic loading was investigated. To achieve a more accurate assessment, the seismic performance of the frames was evaluated using nonlinear analyses, including nonlinear static (pushover) analysis and nonlinear dynamic analysis. This analytical framework enabled a direct comparison of the structural behavior of the frames while accounting for differences in the mechanical properties of the steels used.
Results: The results indicate that the type of steel has a significant effect on the seismic response of special moment frames. Although the use of high-strength steels can increase the initial load-carrying capacity of the structure, this increase in strength does not necessarily lead to improved seismic performance. The findings reveal that shape memory alloys exhibit higher yield strength but lower ductility, despite having an initial elastic modulus similar to conventional steel. In contrast, S235 steel, due to its more favorable ductility and greater ability to dissipate seismic energy, demonstrates more stable and safer behavior in the inelastic range and can improve the overall seismic performance of the structure.
Conclusion: The results also show that shape memory alloys (SMA), owing to their deformation recovery capability and high energy absorption and dissipation capacity, have considerable potential to enhance the seismic performance of steel structures. The use of such materials can reduce residual deformations and improve the re-centering capability of structures after earthquakes, and thus can be proposed as a novel approach in the seismic design and retrofit of steel frames.