###### Abstract  
The mitigation of seismic-induced vibrations is essential for the effective protection of buildings and occupants during earthquakes. This especially applies to slender buildings with metallic frames; in this case, the structure's geometrical layout and relatively low damping properties favor an excessive and potentially catastrophic oscillatory response to a seismic event. Semiaactive systems for energy dissipation are among the most commonly used strategies to control this oscillatory response. They offer the right balance between the reliability of passive devices and the versatility and adaptability of fully active systems. In this work, a vibration-suppression system based on dissipative breachers that integrate commercial magnetorheological fluid dampers (MRDs) was designed and validated through experimental tests on a true-scale structural model that was representative of a five-story slender building with a metallic frame. A practical and robust approach was proposed for: (1) The definition of the MRD type in compliance with a predefined mitigation target for seismic-induced accelerations on each floor of the structure; (2) The modeling of the MRDs, contribute to the dynamic response of the structural system. The approach involves a linearized formulation of the characteristic damping curves of the MRDs at different values of the activating current. By relying upon this linearization, a rapidly converging iterative process was set up to simulate the seismic response of the structure in the case of activated or deactivated dampers. The reference structure and the vibration-suppression system were then manufactured and tested on a sliding table, which provided realistic seismic excitation. The good correlation levels between the numerical predictions and the experimental measurements proved the effectiveness of the conceived system and of the approaches that were used for its design and simulation. s 2022 202  
According to the definition that is provided by the applicable European standard [1], antiseismic devices are tools that are capable of modifying the structure's response to seismic action. Such modifications can generally be achieved in three different ways:  
1. By isolating the structure from the ground;
2. By creating permanent or temporary restraints to the motion via rigid connections;
3. By dissipating energy. Seismic isolation indeed represents the most effective solution to protect the structure, thanks to the relevant reduction in the acceleration, even at the highest floors [2]. Conversely, isolating devices must be designed together with the building that they are called upon to protect and installed during its construction. Moreover, the manufacturing and installation processes are much more expensive than those of the devices that are used to implement Seismic Mitigation Strategies b and c.  
Therefore, the latter two strategies become preferable from a cost-saving standpoint, and they are the only viable solutions when dealing with the seismic retrofit of already built constructions. Rigid connections that prevent the relative motion between different parts of the structure are convenient for their simplicity. However, since their working principle is based on adding extra stiffness to the structure, their effectiveness is limited to a specific seismic excitation of a given intensity-and-frequency content [3]. This drawback is not present in the broad set of devices that mitigate the dynamic response of the structure by properly dissipating the energy that is released by the earthquake. In such a case, additional damping is provided to the system, which thereby lowers its vibration levels more robustly against a variety of seismic excitation characteristics. Of these devices, magnetorheological dampers (MRDs) are among the most effective for vibration control since their properties can be adjusted in real time with relatively low power requirements, and, unlike active devices, they do not inject energy into the system that is being controlled [4].