Theoretical-period characteristics of frame buildings designed under variable levels of seismicity and allowable-drift

Period equations provided by seismic codes are generally derived by calibration with recorded period data of buildings located in high seismicity regions. These period-equations do not account for either the design level of seismicity or the permissible limit of lateral drift. Buildings designed under high level of seismicity are expected to display higher stiffness and shorter periods than buildings designed under low-to-medium seismicity levels. In addition, buildings designed with high level of permissible lateral-drift are expected to display lower stiffness and longer periods than buildings designed with low level of permissible lateral-drift. In this study, the theoretical fundamental-periods of an ensemble of regular reinforced concrete(RC) and steel moment-resisting frame(MRF) buildings having 3-, 6-, 9-and 12-stories and designed with various levels of seismicity and permissible lateral-drift are evaluated. The obtained outcome indicates the sensitivity of the MRF theoretical-periods to the design seismicity and the permissible lateral-drift. The results also indicate the need for modifying the current period equations to realistically account for the variations in the design seismicity and allowable lateral-drift of MRF buildings.