Inelastic deformation ratios for nonstructural components subjected to floor accelerations

Abstract

This study reports the preliminary findings of a research effort aimed at investigating in detail the properties of the inelastic deformation ratio of SDOF systems subjected to floor accelerations. It was found that: (a) the spectral shape of floor accelerations is not made up of acceleration-, velocity- and displacement-sensitive spectral regions; (b) when the natural period of the SDOF system is long, the IDR is still essentially equal to unity (i.e., the “equal displacement rule” still applies); (c) when the natural period of the SDOF system is short, the IDR does not increase monotonically as the natural period of the SDOF decreases, but exhibits local minima at the modal periods of the building; and (d) the IDR remains constant when the damping ratio varies between 2% and 5%. Finally, an existing analytical expression of IDRs of ground accelerations was examined, and its application to floor accelerations was evaluated. An improved equation, valid only for accelerations at the roof level, is then proposed.