Nonlinear drift demands on moment-resisting stiff frames

Drift demands for stiff moment-resisting frames are investigated. A total of 8 regular frame models with 3- to 9-stories are subjected to 40 soil site records. The moment. magnitude and source-to-site distance of the ground motion data set varies between 5.7 <= M <= 7.6 and 2.5 km <= d <= 23 km, respectively. The ground motion data set is divided into 2 equal bins to represent different seismic hazard levels. The frames conforrn to the seismic code provisions for the median design spectra of the ground motion bins and they are classified as stiff frames according to their fundamental periods. Nonlinear response history analyses are conducted to present the height-wise variation of maximum lateral displacement profiles and story drift demands for the frame models considered. The accuracy in estimating the maximum roof and interstory drifts is investigated through simplified procedures that use the first-mode approach. The statistics presented show that the maximum interstory drift is strongly correlated with the building configuration and ground-motion features. Use of first-mode approach associated with building elastic dynamic properties generally yields conservative maximum roof drift estimations. A novel approach is also evaluated that can reveal preliminary information about the nonlinear maximum interstory drift if the concern is not the exact location of this deformation demand