NEHRP Clearinghouse

Title
Seismic Design Response by an Alternative SRSS (Square Root of the Sum of the Squares) Rule.
File
PB83216606.pdf
Author(s)
Singh, M. P.; Mehta, K. B.
Source
National Science Foundation, Washington, DC., March 1983, 48 p.
Identifying Number(s)
VPI-E-83-12
Abstract
The Square Root of the Sum of the Squares (SRSS) procedures are often used to obtain seismic design response. The design inputs for such procedures are usually defined in terms of psuedo velocity or acceleration response spectra. Erroneous results have been obtained with these existing SRSS procedures, especially in the calculation of response where high frequency effects dominate. Here an alternative SRSS procedure is developed using the so-called mode acceleration approach of structural dynamics. The design input in this procedure is defined in terms of, though, primarily relative acceleration spectra but also relative velocity spectra. The relative spectra can be related to psuedo spectra. For a given number of modes to be used in the analysis the new SRSS rule proposed here will predict a more accurate response value than the rules which use psuedo spectra as input, for systems with or without dominant high frequency mode effects.
Keywords
Dynamic response; Ground motion; Buildings; Earthquake engineering; Seismic design; Earthquakes; Structural design; Equations of motion; Excitation; Spectral density distribution; Bending moments