Development And Evaluation of Response Spectra for Gorkha Earthquake Ground Motion and Using It to Determine Seismic Response of Typical RC Building

Abstract

e response spectrum, a widely accepted concept used to estimate the lateral forces on the structure, is an envelope of the maximum response of a single degree of freedom (SDOF) system to a particular ground excitation. Since it is very much ground motion dependent and is irregular, it cannot be used directly and has to be smoothed out. It can be used readily to analyse new structures' seismic response and estimate existing structures' response. This study considers 19 ground motion records of 2015 Gorkha Earthquake sequence. These are categorized by magnitudes for rock sites in Kathmandu Valley using Newmark-Beta time stepping method implemented in Python, where elastic response spectra were computed and median and 84.1th percentile design spectra developed. Comparison with the design spectra of the Nepal Building Code (NBC 105:2020), Indian Standard (IS 1893:2016) showed that Gorkha Earthquake (GEQ) based spectra for larger magnitudes(Mw> 6) exceeded the code values in the displacement-dominated period range (T>2s). Practical implications were evaluated through the analysis of a typical RC building in ETABS. The seismic demand computed using the GEQ-based spectra, in terms of base shear, story displacement, and inter-story drift, is significantly lower compared to that of code based spectra.