State-of-the-Art of Development of Floor Spectra

by M. P. Singh, Virginia Polytechnic Inst &, State Univ, Dep of Engineering, Science & Mechanics, Blacksburg,

Document Type: Proceeding Paper

Part of: Structural Engineering in Nuclear Facilities


Floor spectra are used as seismic inputs for the design and qualification of subsystems and equipment. Until very recently, the time history analyses with single acceleration time history as input were very commonly used. However, this approach has been observed to give nonunique floor spectrum curves. Thus, as alternatives several direct approaches have been developed. The approaches which are based on the random vibration principles but employ response spectra directly have more rational appeal. Several such approaches are available. Four different approaches, employing the mode displacement and mode acceleration formulations, covering the proportionally as well as nonproportionally damped structures, are presented. The mode displacement formulations are most commonly used, although the mode acceleration formulations seen to be the better alternatives, both for the proportionally and nonproportionally damped structures. The need for the development of other forms of floor response spectra such as the relative velocity and relative acceleration spectra is also identified.

Subject Headings: Floors | Seismic design | History | Seismic tests | Response spectra | Displacement (mechanics) | Vibration | Damping

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