Multistage friction damping to control the response of a base isolated structure

Base isolated structure systems can reduce seismic response acceleration. But over predicted response displacement may occur as a result of extreme earthquakes and ground motion, including long period components. To mitigate the damage caused by the excessive displacement beyond the usual design limit, the authors proposed and developed a displacement controlling system by the means of a friction damper with a coupling mechanism that is activated only after large displacements occur. In this paper, the multistage damping system, using different types of the friction damper with a coupling mechanism, is investigated. Friction dampers are coupled corresponding to the input ground motion level, and then, dampers provide suitable damping capacity. Design parameters of friction dampers are determined based on the properties of the suitable hysteretic damper for each input level. The results of the analytical study show that the proposed system is effective for suppressing the maximum response and keeping a suitable damping capacity for each input ground motion level.