Abstract
A series of numerical calculations have been performed to investigate the effect of soil improvement on seismic site response. Seismic site response analyses were also performed using data collected from a study area in Babol city. The improved site is a composite ground and has more or less different mechanical properties than the natural ground. In this research, the influence of the elastic modulus of the pile, the pile distance ratio, ground motion input, distance to fault rupture, and PGA of the earthquakes on seismic response characteristics are especially investigated. The results reveal that the values of the PGA and amplification factor on the surface of the natural and improved grounds depend strongly on the fundamental period of the site, the predominant period, and the intensity of the ground motion input. The acceleration response spectra also are affected by the characteristics of ground motion input and soil layers. Changing the pile distance ratio doesn’t have a significant effect on the seismic response of the site.
Highlights
The influence of local site conditions on ground motions has been investigated since the early days of earthquake engineering
Under Loma Prieta earthquake, the acceleration response spectra have two peaks, but in contrast with Northridge earthquake, the acceleration response spectra of the natural ground are approximately smaller than the acceleration response spectra of the improved ground at the two peaks
Improvement makes the site stiffer, so strains become smaller and the improved ground shows elastic behavior. As it can be seen from this section, the seismic response of the natural ground in Babol city is different from the seismic response of a 30-m-thick clay layer
Summary
The influence of local site conditions on ground motions has been investigated since the early days of earthquake engineering. Due to the flexibility of finite element method to deal with complex issues, people began to use numerical simulation to study this issue; Siegel et al [5] investigated the site response of improved ground with stone column in the coastal eastern United States. They observed that the influence of vibrio-replacement was more dramatic in the characteristic clay profile as compared to the characteristic sand profile. The influence of the elastic modulus of the pile, the pile distance ratio, ground motion input, distance to fault rupture, and PGA of the earthquakes on seismic response characteristics are especially investigated
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