NEHRP Clearinghouse

Title
On Inelastic Response Spectra for Aseismic Design.
File
PB284507.pdf
Author(s)
Lai, S. S. P.; Biggs, J. M.; Vanmarcke, E. H.
Source
National Science Foundation, Washington, D.C. Div. of Advanced Environmental Research and Technology., July 1978, 155 p.
Identifying Number(s)
['R78-18', 'MIT-CE-R78-18']
Abstract
The sources of variability in inelastic response spectra, namely, strong ground motion duration, ductility level, and viscous damping ratio, are investigated. From time history analysis, it is concluded that the Newmark inelastic response spectrum for elasto-plastic systems are unconservative for 5% damping, and conservative for 2% damping. By comparing the 'inelastic response ratios,' new inelastic response spectra are proposed. Based upon simulation studies, semi-empirical modifications to an elasto-plastic random vibration model are suggested. The resulting probabilistic predictions of the inelastic response are quite compatible with those obtained by time history analysis. Three steel moment-resisting frames are analyzed to assess the validity of the modal analysis-based inelastic frame design procedure. The results indicate that this design procedure of using the proposed inelastic response spectra yields better frame designs than those based upon the Newmark spectra. However, the procedure results in conservative design for interior columns and girders, and unconservative design for upper story exterior columns.
Keywords
Dynamic response; Ground motion; Buildings; Earthquake engineering; Earthquake resistant structures; Seismic design; Earthquakes; Random vibrations; Earth movements; Elastic analysis; Soil mechanics; FRIEDA computer program; Framed structures; Seismic risk analysis; Computer aided design; Dynamic structural analysis