An in-house code for studying the response of soil deposits in Mumbai city using 2-D equivalent linear and 1-D nonlinear approach

For simulating any type of dynamic soil–structure interaction, a site response analysis is a necessary precursor. A 2-D equivalent linear model and a nonlinear model using hyperbolic tangent formulation are developed in-house for the purpose. Both the numerical models are validated by the experimental results on cohesionless soil conducted within a large-scale laminar box at Buffalo State University, New York and an open-source code DEEPSOIL. The non-linear soil behaviour of the laminar box is modelled by obtaining the normalised stiffness and damping ratio from torsional resonant column test. The validated program is used for prediction of the response behaviour at two sites in Mumbai. The ground response by equivalent linear and nonlinear method shows amplification factors of 2.95 for Site-1 and 3.55 for Site-2, 2.88 for Site-1 and 2.84 for Site-2, respectively. It is observed that the effects of the loading-unloading rules as well as the selection of the small strain damping values have a significant influence on the high-frequency content of the site-specific spectrum. The generated spectrum obtained from the nonlinear analysis may be used for any dynamic analysis at these locations with due regards to the values of small strain damping which is recommended to be around 1.0–1.5% for these sites.