Newly Developed MATLAB Based Code for Equivalent Linear Site Response Analysis

Abstract

Characteristics of ground motions generated during an earthquake (EQ) alter between bedrock and the surface depending upon subsoil properties. Such modifications in the ground motion characteristics are termed as local site effects. Building response as well as induced effects of EQs are thus controlled by these modified ground motions at the surface. Hence, addressing the local site effect known as site response analysis is of considerable importance for any region. Numerically, site response analysis can be performed using linear, equivalent linear and nonlinear methodologies. Amongst these three methodologies, equivalent linear method of site response analysis is widely followed because of its simplicity and reasonable accuracy. At present, there are numerous softwares and codes which can perform site response analysis following equivalent linear methodology. Some of these softwares are; SHAKE2000, EERA and DEEPSOIL. In this work, a new MATLAB code is developed which can perform equivalent linear site response analysis in the frequency domain. New code is developed in such a way that the response in user specified layers can be shown together for better comparison and understanding. All the response parameters (Fourier spectrum, strain time history, amplification spectra, acceleration time history etc.) are shown in a single window so that the user can compare amongst them. Further, the numerical values of these response parameters can be obtained easily. In addition, limitation of underestimating high frequency ground motion by available equivalent linear analysis tool is overcome in the newly developed code. In order to validate the newly developed code, site response analyses carried out for a typical borehole using SHAKE2000 and newly developed code are compared and found closely matching.