Performance of passive energy dissipation systems during near-field ground motion type pulses

Near-field earthquakes are characterized by short duration pulses of long periods with large peak ground velocities and accelerations. Recent studies have shown that the performance of passive energy dissipation systems (PEDS) depends significantly on the characteristics of near-field ground motion pulses. In this paper, a detailed and systematic investigation on the performance of passive energy dissipation systems during near-field ground motions has been carried out by using an analytical ground velocity pulse model recently proposed by the authors. Displacement and acceleration pulse spectra have been developed for structures with/without linear and nonlinear viscous dampers and yielding dampers. The energy balance approach has been used to explain why PEDS perform differently, depending on structural and pulse periods. It is shown through response spectra that PEDS perform quite differently during pulse-type and sinusoidal excitations, although they are most efficient near resonance during both excitations. Both linear and nonlinear viscous dampers with 25% supplemental damping ratio are effective in achieving more than 40% displacement reduction when 3/545Tn, and they may achieve less displacement reduction when Tp<45Tn. Yielding dampers can simultaneously reduce displacement, acceleration and input energy for structures with Tn/Tp<1Tn/Tp<1, and they may amplify these quantities when Tn/Tp>1Tn/Tp>1. Energy balance analysis shows that structural response quantities can only be effectively reduced when the instantaneous damper dissipated energy is in phase with instantaneous input energy at all time instants.