An Innovative Multi-Level Energy Dissipative Device with a Combination of SMA Wire and Friction Damper

Structural Control is a new method to enhance the behavior of structures. The performance of these systems to reduce damage and improve the behavior of structures in earthquakes is based on reducing the structural demand and absorb the energy of earthquakes in an additive damping system. Poor performance in earthquakes with a seismic level below the design earthquake is a defect in conventional dampers. Since the dampers are considered for design earthquake, they have the best performance in design base earthquake (DBE) level. However, if the structure is designed for a seismic level below the DBE, the structure couldn't have proper behavior in DBE. This defect in passive dampers is one of the main reasons for using multi-stage dampers that making the structure able to have acceptable behavior in different seismic levels.In this study, friction damper and shape memory alloy were combined to behave in two phases. In the proposed damper (FD-SMA), the SMA wire works in the first phase, and it is combined parallel with the friction part. The two-stage behavior result from a displacement gap that works in series with the friction damper. An essential advantage of the proposed damper compared to other two-phase dampers is that the first fuse remains undamaged in moderate earthquakes because of shape memory alloy super-elasticity and leads to maintaining the structure's performance in future earthquakes without repairs. Also, it is expected that the residual displacement decrease in both stages. The small scale of the proposed FD-SMA damper was fabricated and evaluated in the structural laboratory of IIEES. Also, the behavior was modeled in the Open-sees program.The desired dual-stage performance is achieved in all experimental tests. And as expected, the re-centering property of SMA reduces the residual displacement and minimizes the damage in the first stage.The results obtained from the experiment were matched to the model created in the Opensees software, and a satisfactory adaptation was achieved. If unwanted friction is not considered, the first fuse has an acceptable elastic behavior and remains undamaged. Finally, with the parametric study and modeling of ۱۵ different models of FD-SMA damper, the optimal damper was identified.

Keywords:

Hybrid passive damper , Two level damper , Shape memory alloy , friction damper