Abstract
Characterization of nonlinear hysteretic responses plays a significant role in predicting soil behaviors. They are mostly described with either simple empirical functions or complex constitutive models. However, the input parameters lack both a physical basis and robustness, and the use of these models is limited to some typical soils. Therefore, there is a need for a simple but robust model that uses only a small number of physically meaningful parameters. This study proposes explicit formulas to capture different nonlinear hysteretic soil responses, including a constitutive model, backbone curve, tangent shear modulus, secant shear modulus, and damping ratio. In particular, the Davidenkov model, with two physically meaningful parameters, is adopted to assess the constitutive relationships of soils under steady-state cyclic loading. The proposed models are validated with resonant column test (RCT) data (shear modulus and damping ratio). This paper finds that the use of the linear characteristic equation to calculate the shear modulus from the resonance frequency in the RCT, which is clearly irrelevant and approximate, produces data interpretation errors.
Highlights
After earthquakes, detailed studies of the seismic ground responses are typically conducted, showing that (1) soil deposits exhibit strong dynamic nonlinear responses, and (2) characterization of the soil dynamic properties plays a crucial role in accurately estimating the site amplification characteristics [1,2,3].Strong ground motion causes the accumulation of plastic deformation during earthquake cycles, and elastic theory cannot be applied to describe the deformational characteristics of the soil deposits.Site response analysis methods with nonlinear responses can be divided into the equivalent linear and nonlinear approaches
The proposed models are validated with resonant column test (RCT) data
This paper finds that the use of the linear characteristic equation to calculate the shear modulus from the resonance frequency in the RCT, which is clearly irrelevant and approximate, produces data interpretation errors
Summary
After earthquakes, detailed studies of the seismic ground responses are typically conducted, showing that (1) soil deposits exhibit strong dynamic nonlinear responses, and (2) characterization of the soil dynamic properties plays a crucial role in accurately estimating the site amplification characteristics [1,2,3]. More sophisticated models for cyclic loading use more fitting parameters so as to precisely reproduce closed hysteresis loops that are influenced by basic soil parameters (plasticity, void ratio, confinement stress) and the imposed shear strain amplitude [12,13,14,15,16,17,18,19,20,21] While those models are capable of expressing the nonlinear hysteretic response or degree of strain-dependency during steady-state cyclic loading, their input parameters lack both a physical basis and robustness, and the use of such models is quite limited to certain soils. This study proposes explicit formulas for capturing certain nonlinear hysteretic soil responses These include a constitutive model, as well as the backbone curve, tangent shear modulus, secant shear modulus, and damping ratio. The validity of the linear characteristic equation is addressed during the process of data interpretation
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