Uniform hazard floor acceleration spectra for linear structures

This paper presents a practical method to compute uniform hazard floor acceleration spectra for linear oscillators attached to a linear structure. The method builds on a probabilistic seismic demand model that relates the acceleration response of the oscillator with that of the generic mode of vibration of the supporting structure. Interaction between oscillator and structure is ignored. Independency of the model on the specific characteristics of seismic hazard at the site is shown. By using the method floor spectra are determined through a closed-form expression, given the mean annual frequency of interest, the damping ratio of the oscillators, the modal properties of the structure, and three uniform hazard spectra representing seismic hazard at the site.