NEHRP Clearinghouse

Title
Elastic and Inelastic Response Analysis of Site-Influenced Ground Motion Records. Seismic Design Decision Analysis.
File
PB295050.pdf
Author(s)
Yegian, M. K.; Whitman, R. V.
Source
National Science Foundation, Washington, DC. Applied Science and Research Applications., April 1975, 35 p.
Identifying Number(s)
INTERNAL STUDY-55
Abstract
Results of elastic analyses clearly indicate that the characteristics of a site-influenced ground motion record very much depend upon the stiffness of the soil and the thickness of the deposit. The stiffer the soil, the greater the maximum ground acceleration. Also, for the same depth of profile, the stiffer the soil, the smaller the fundamental period of the profile. Due to non-linear effects, the stiffness of a soil deposit is a function of not only the material properties at low strains, but also the strength of the input motions. The influence of profile depth upon the computed responses is very apparent in all the analyses. In fact, the softer the soil is, the more pronounced is this influence. Increasing the depth of a soft deposit significantly increases the fundamental period and reduces the maximum ground and peak spectral accelerations. However, it appears that the profile depth and the soil stiffness do not have any significant influence upon the peak ratio of response spectra. Almost identical responses computed for three dense sand and gravel profiles warrant the definition of 'firm ground' as a dense sand and gravel deposit of up to 150 ft. thick. The results of the elasto-plastic analyses show that the higher the available ductility in a structure, the smaller the design yield acceleration.
Keywords
Massachusetts; Soil classification; Earth movements; Elastic analysis; Dynamic response; Buildings; Earthquake engineering; Ground motion; Soil surveys; Soil properties; Earthquakes; Dynamic structural analysis