Comparison of 1D linear, equivalent-linear, and nonlinear site response models at six KiK-net validation sites

• Published in: Soil dynamics and earthquake engineering (1984) 2015-02, Vol.69, p.207-219
• Main Authors: Kaklamanos, James, Baise, Laurie G., Thompson, Eric M., Dorfmann, Luis
• Format: Article
• Language: English
• Subjects: Arrays; Earthquake ground motion; Equivalence; Ground motion; Mathematical models; Nonlinear soil behavior; Nonlinearity; Numerical modeling; Seismic analysis; Seismic effects; Seismic phenomena; Soil (material); Strain
• ISSN: 0267-7261; 1879-341X
• DOI: 10.1016/j.soildyn.2014.10.016

Vertical seismometer arrays represent a unique interaction between observed and predicted ground motions, and they are especially helpful for validating and comparing site response models. In this study, we perform comprehensive linear, equivalent-linear, and nonlinear site response analyses of 191 ground motions recorded at six validation sites in the Kiban–Kyoshin network (KiK-net) of vertical seismometer arrays in Japan. These sites, which span a range of geologic conditions, are selected because they meet the basic assumptions of one-dimensional (1D) wave propagation, and are therefore ideal for validating and calibrating 1D nonlinear soil models. We employ the equivalent-linear site response program SHAKE, the nonlinear site response program DEEPSOIL, and a nonlinear site response overlay model within the general finite element program Abaqus/Explicit. Using the results from this broad range of ground motions, we quantify the uncertainties of the alternative site response models, measure the strain levels at which the models break down, and provide general recommendations for performing site response analyses. Specifically, we find that at peak shear strains from 0.01% to 0.1%, linear site response models fail to accurately predict short-period ground motions; equivalent-linear and nonlinear models offer a significant improvement at strains beyond this level, with nonlinear models exhibiting a slight improvement over equivalent-linear models at strains greater than approximately 0.05%. •We assess site response models using 191 records at six well-behaved KiK-net sites.•Equivalent-linear and nonlinear models offer large improvements over linear models.•Nonlinear models slightly outperform equivalent-linear models for strains>0.05%.•Most models are biased towards underprediction of short-period amplifications.•To fully capture site behavior, the 1D total stress assumption must be addressed.