Document Type : Original Article

Author

• Yazdan Shams Maleki

Assistant Professor, Department of Civil Engineering, Kermanshah University of Technology, Kermanshah, Iran

Abstract

In this paper, the effect of the middle soft soil layer on the seismic response of a multi-layered site is investigated with the help of one-dimensional equivalent-linear and non-linear analysis methods. The constitutive model used for the multi-layer soil site is the viscoelastic model. Basically, in the discussions of soil dynamics, a soft soil layer with a low shear wave velocity is assumed, which is the basis of the analytical and numerical analyses of this research. In this study, the effect of the stiffness, geometric and spatial characteristics of the middle soft soil layer on the overall seismic response of the site in the field of spectral acceleration responses is investigated. The viscoelastic stress-strain relationship has been solved in the analysis of the equivalent-linear response using the analytical method and in the analysis of the non-linear response using the finite difference numerical method. Also, the effect of characteristics such as the depth of the soft soil layer, thickness, shear wave velocity, material damping, its density and other factors have been evaluated in the separate analyses. The results of this research show that the existence of the soft soil layer has a double effect on the seismic response of multi-layer sites. First, by increasing the thickness of the soft layer under the hard layer, this layer reduces the spectral response acceleration values like a damper. And on the other hand, by removing the upper hard layer and increasing the thickness of the soft layer up to the ground surface, the acceleration spectral amplification values, despite the decreasing trend, are several times the case when the hard layer is located on top of the soft layer. In both equivalent-linear and non-linear methods, with the increase in damping, the peaks of the acceleration response spectrum are smoothed, in addition to that, the spectral acceleration value also decreases. Besides, the non-linear method, in the conditions of the minimum damping ratio (i.e., critical damping ratio equal to zero), gives more response acceleration than the equivalent-linear method. Increasing the damping, as well as increasing the thickness of the soft layer, has caused a decrease in the response acceleration values of the multilayered site

Keywords

• One-dimensional site seismic response analysis
• Equivalent-linear response
• Non-linear response
• Soft soil layer
• Acceleration spectral response

Main Subjects

• Modeling in Civil Engineering