Using a Lumped Mass, Non-Uniform Stiffness Beam Model to Obtain the Inter-Story Drift Spectra

• Published in: Journal of structural engineering (New York, N.Y.) N.Y.), 2013-07
• Main Authors: Shodja, Amir H, Rofooei, Fayaz R
• Format: Article
• Language: English
• Subjects: Beams (radiation); Buildings; Construction; Demand; Drift; Estimating; Spectra; Stiffness
• ISSN: 0733-9445
• DOI: 10.1061/(ASCE)ST.1943-541X.0000916

The drift spectrum has recently been introduced as a new measure for estimating the inter-story drift demands in buildings under near field earthquakes. In this study, a method for estimating the drift demands in buildings with different structural systems is presented. Unlike previous studies that use a continuous beam, a stick model is employed to estimate the seismic-induced inter-story drift demands. The proposed method can overcome the deficiencies of the previously introduced models. It can consider the effect of height-wise stiffness reduction on drift demands which is shown to be very important, and makes it possible to construct the drift spectra for low and medium-rise as well as high-rise buildings. The suggested method is simple since it uses the well-established modal analysis technique of lumped mass beams. The drift spectra for shear building models are constructed using near-field strong ground motions. The effects of the ratio of the lateral stiffness of top story to that of first story, height-wise variation of structural stiffness, number of stories, damping ratios, and higher modes on drift demands are investigated. A method is presented for using these spectra in estimating the drift demands in moment resisting frame structures and the accuracy of the method is verified using a number of SAC building models.