Rare earthquakes cause heavy damages to building structures. Design of structures using yield mechanisms that provide extra resources to ensure structural stability for intensity higher than the design-based earthquake (DBE), can be considered as a reasonable technique to reduce the collapse probability. In this regard, the design of a mass-isolated structural system with a multi-phase seismic behavior as a reliable lateral load-bearing system has been investigated. In this type of configuration, by separating the mass from the stiffness of the system in the vertical direction, the structural system is transformed into two subsystems (a soft and a stiff), which can be utilized as an effective damping amplification technique by using an appropriate energy dissipation mechanism between these two parts. Furthermore, it can be used as an efficient seismic rehabilitation method for non-code-confirmed structures. In this study, in addition to performing parametric studies to determine the optimal damping coefficient, the impact and ultimate collapse mechanism of the system have been simulated and investigated numerically. The results of nonlinear time history analysis indicate that the mass-isolation technique can efficaciously improve the seismic performance of buildings compared to conventional structural systems due to the multi-phase seismic behavior.