Semi-active control of civil structures has shown to be promising at mitigating vibrations. Those systems typically perform significantly better than passive systems, and only necessitate small power to operate. Nevertheless, semi-active control devices are not yet accepted by the construction and structural engineering communities. Among impeding factors, semi-active devices are not perceived as sufficiently reliable or robust. In this paper, a new semi-active damping device based on existing reliable technology is proposed. It is composed of a stiffness element, a viscous damper, and a braking mechanism in parallel. The device, termed the modified friction device (MFD), is essentially a variable friction damper based on vehicular braking technology, equipped with a fail-safe mechanism.

The MFD is investigated as a replacement to the actual viscous damping contained in an existing structure in Boston, MA, for mitigation of accelerations caused by wind excitations. Simulations have showed that the MFD of 200 kN is capable of wind mitigation when compared with the performance of a passive viscous strategy of much larger capacity. Also, an MFD of 1350 kN capacity can perform similarly by using only a third of the number of dampers currently contained in the existing structure. Finally, the proposed device shows to be promising at mitigating inter-story displacements in the occurrence of an earthquake.