Comparison of the drift spectra generated using continuous and lumped-mass beam models

The drift spectrum, as a new measure of earthquake-induced demands instructures, was developed using a uniform-stiness continuous beam model. practicallimitations in the procedures based on such models have caused structural engineers topay little attention to drift spectra. in this paper, a method is proposed to estimate theseismic-induced inter-story drift demands, using the modal analysis technique of lumpedmass, non-uniform beam models. the proposed approach is simple and can overcome manydeciencies of the previous methods. it can take into account the very important eect ofheight-wise stiness reduction on drift demands, without the numerical diculties usuallyencountered in computing the drift spectra. the drift spectra for high-rise shear buildingsare computed using both continuous and lumped mass beam models. the comparisonsindicate that the results of the continuous uniform-stiness beam models in some cases arenot acceptable. the eects of various parameters such as the structural system, the heightwisevariation of structural stiness, the number of stories, higher modes and damping ratioson inter-story drift demands are investigated. also, the inuences of the structural systemand height-wise variation of structural stiness on the height-wise distribution of maximuminter-story drift demands are evaluated using a number of building models.