An efficient nonlinear-analysis-free modal solution procedure to estimate drift demands of code-compliant medium- and high-rise regular buildings

Significant advancement has been accomplished in recent years in developing simplified multimodal procedures for the seismic evaluation of buildings. However, many of these methods are complex and computationally intensive for practical applications. Moreover, the extension of some of these methods for structures with complicated geometries, like geometrically irregular buildings, is not practically feasible due to the exponential increase in the number of analyses required. This paper introduces an efficient nonlinear-analysis-free multi-mode procedure, referred to as AMPD, for the direct estimation of story drifts in buildings. Rooted in structural dynamics theory and leveraging the concept of modal combination, the AMPD procedure is user-friendly and straightforward and can be readily extended to buildings with various configurations since no nonlinear analysis is required in the process of its implementation. The proposed method computes nonlinear drift demands by enveloping the results obtained from a series of equations that rely solely on the modal properties of the structure deriving from an eigenvalue analysis of a linearly elastic system and the spectral parameters of earthquake ground motions. Therefore, this procedure eliminates the need for elaborate nonlinear numerical models, sophisticated software, and robust computer processors. The performance of the AMPD procedure is examined using an extensive database of code-compliant low-, mid-, and high-rise SMRFs representative of regular building configurations without extreme weak or soft stories. Comparison of the AMPD results with those from nonlinear time history analysis (NTHA), as the most accurate available method, at two seismic hazard levels reveals that the proposed approach can reliably estimate the story drift demands of buildings.