Previous studies have suggested that rocking vibration accompanied with foundation uplift motion might reduce the seismic damage of buildings subjected to severe earthquake motions. In this paper, the seismic response of ten-story steel frames with columns allowed to uplift is evaluated and compared with that of fixed-base frames by numerical analyses. It is shown that the base shears in the frames with column uplift are significantly reduced as compared to the fixed-base frames, and that the

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... rtical component of earthquake motions does not much affect the horizontal responses of uplift frames but increases slightly the uplift response displacement of uplift frames.