Simplified Seismic Drift Analysis of High-Rise Steel Frames

After a simplified method for estimating motion amplitudes of high-rise steel frames under wind forces had been published in this periodical1 about two years ago, the question invited itself if the general approach used in that paper could also be employed to obtain drift statements for high-rise steel frames under the application of seismic loads as prescribed in the major building codes. This paper answers the question in the affirmative by demonstrating how the practicing engineer can estimate seismic drift amplitudes under code seismic forces very quickly and without the use of a computer by applying the following simplifying assumptions which have been demonstrated to be valid for use in preliminary design, yielding results of excellent accuracy.