Revision of IS 1893: Proposal for an Alternative Soil Classification Scheme and Associated Intensity-Dependent Spectral Amplification Factors

Abstract

This paper provides an improved soil classification scheme and associated spectral acceleration response curves along with the site amplification factors for the ongoing revision of IS 1893 Part-1 [BIS (Bureau of Indian Standards). 2016. Criteria for earthquake resistant design of structures. IS 1893-1. New Delhi, India: BIS]. A ground response analysis of 124 sites across India is conducted using the nonlinear procedure of DEEPSOIL. In addition to the classical geotechnical parameters NSPT, Su, and plasticity index (PI), the improved soil classification scheme also uses the fundamental period of a site (T0) and the average shear wave velocity to the seismic bedrock, instead of only VS,30. New site amplification factors (i.e., Fa and Fv) are proposed for all site classes of the improved soil classification scheme and compared with the amplification factors of other national codes. Further, elastic design response spectra are proposed for the improved soil classification scheme by considering the proposed site amplification factors (i.e., Fa and Fv). The compatibility of the proposed elastic design response spectra with other national codes’ design spectra is further evaluated.