Control performance of sloped rolling-type isolators designed with stepwise variable parameters

With the same horizontal acceleration control performance, the horizontal displacement control performances of sloped rolling-type seismic isolators passively provided with stepwise variable parameters, as well as constant ones, are numerically investigated in this study. The first design possesses a smaller sloping angle with larger damping force at smaller horizontal isolation displacement and a larger sloping angle with smaller damping force at larger horizontal isolation displacement. In other words, this design has stepwise increased sloping angles and stepwise decreased damping force with increasing horizontal isolation displacement. The second design has an opposite design philosophy to the first one, i.e., it has stepwise decreased sloping angles and stepwise increased damping force with increasing horizontal isolation displacement. A series of numerical results present that for sloped rolling-type seismic isolators designed with a constant sloping angle and damping force, in general, the larger the damping force (in other words, the smaller the sloping angle), the smaller and the larger the horizontal maximum and residual displacement responses presented, respectively. The first and second designs with stepwise variable parameters each have its advantage for suppressing horizontal isolation displacement under far-field and pulse-like near-fault ground motions because of their larger energy dissipation capabilities designed at different stages. When the horizontal isolation displacement responses at the end of ground motions are still within the first slope rolling range with a larger sloping angle of the second design, as expected, adopting the second design can exhibit a better re-centering performance than adopting the first design. To have acceptable displacement control performances and without scarifying acceleration control performances under diverse seismic demands, compared with adopting the designs with constant parameters and the first design, adopting the second design could be an alternative solution and better choice.