Analytical Model of Ground Motion Pulses for the Design and Assessment of Seismic Protective Systems

In this paper, an analytical pulse model for velocity pulses observed in near-field ground motions has been proposed for a systematic design and assessment of seismic protective systems. The proposed pulse model utilizes pulse period, decay factor, and shape parameters to model both buildup and decaying phases observed in recorded ground motions. It is demonstrated that the proposed model can successfully simulate observed ground motion pulses. Peak displacement, velocity, and acceleration of the analytical pulse model are directly correlated with peak ground motion parameters and the pulse period. The response spectra and displacement reduction factor using the pulse model correlate well with those using recorded ground motions for structural periods close to or longer than the pulse period, although there is lesser correlation for shorter structural periods because of exclusion of high frequency components in the pulse model. For a base-isolated building with 2.5 s natural period and equipped with supplemental viscous dampers, it is demonstrated that supplemental dampers are the most effective when the structural period is close to the pulse period. Displacement reduction using supplemental passive dampers is smaller when the pulse period is longer or shorter than the structural period, although the displacement demand is quite significant.