Local Site Effects Using Elasto-Plastic Constitutive Model
M.Sc of Geotechnical Engineering, Mazandaran University, Babol, Iran
Assistant Professor, Department of Civil Engineering, Mazandaran University, Bobol, Iran
From engineering point of view the importance of an earthquake is its effect on constructions like dams, bridges and residential regions. In most cases these constructions are not built on the bed rock surfaces but they are on the soil deposits over the bed rocks. Quake waves falls a victim to change while passing through deposit layers which is known as "site effect ". Site effects are considerable in two pivots: topography and soil conditions of any region.
Babol city is the site that considered in this research. Babol is a small city in northern of Iran, Babol city is selected for investigation of layered soil deposits' effect on seismic response of the ground. Because of the variation of layering condition in Babolís soil and providing needed layering research (sovereignty of loose layers, sovereignty of dense layers and loose-dense intermittent layering) the soil of this site were taken under investigation as a real model. Because the earth was flat in Babol; topography did not considered importantly and geotechnical properties of Babolís soil layering understanding considered most determiner factor in Babolís site effect. Babol region geotechnical data is collected based on diggings which were done in Babol. These data are considered as two major branches of data. First one is one hundred bore holes in twenty points in Babol city to depth of sixty meter and second is seventy deep wells to depth of two hundred fifty meter in Babol region. Five zones are found to investigate the site effect of Babol city based on the obtained data from geotechnical parameters. In this research dynamic analysis are done in a time period by using elasto-plastic model, which models soils' behavior more realistic and the results are presented as normalized site response spectra. The obtained response spectra from fully nonlinear method for layered soil was compared with response spectra obtained from fully nonlinear method done for homogenous soil and response spectra of 2800 code and the effect of being layer analyzed in site effect analyzing too. Response spectra obtained from fully nonlinear method were also compared with site response spectra of Iranís' 2800 code.
Keywords: Babol City; fully nonlinear method; equivalent linear method; site effect; dynamic analysis; response spectra; Plaxis; Iran 2800 code.
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