Mahdy Khari - Assistant Professor, Department of Civil Engineering East Tehran Branch,Islamic Azad University, Tehran, Iran
Hossein Moayedi - Assistant Professor, Department of Civil Engineering, Kermanshah University of Technology, Kermanshah,Iran
Majid Khari - Master Student, Department of Civil Engineering Semnan Branch,Islamic Azad University, Semnan, Iran

Dynamic soil properties such as shear modulus and damping are the most prominent factors of amplificationphenomenon during earthquakes. The shear modulus degradation and damping ratio curves have beendeveloped based on the nonlinearity soil from hysteresis loops. Plasticity index and Effective confining pressureare governing factors that affect the nonlinearity soil behavior. In this paper, the shear modulus degradation anddamping ratio curves were derived from the two cases. The first of them was based on only effective confiningpressure, whereas the second case was based on plasticity index and effective confining pressure. The equivalentlinear method was implemented for the site response analyses of these two models. The results of this studyillustrated the influence of the plasticity index on the soil shear strength and the site response.

Plasticity Index, Effective Confining Pressure, Equivalent Linear Method, Shear wave velocity, Shear Modulus