Ground Response Analysis and Seismic Behavior Assessment Using SPTN Values

Abstract

In the city of Islamabad, a thorough examination into one-dimensional equivalent linear ground response was methodically performed. This thorough investigation was carried out with special attention to the city's distinctive geological features using the DEEPSOIL software in a methodical manner. Notably, the analysis avoided the influence of the groundwater table in Favor of the more general seismic factors that control ground response dynamics. Subsoil data for input were acquired from a combination of laboratory and field research and were chosen based on site-specific conditions. The investigations were carried out at a bedrock site 13 meters below ground level. Following evaluations with the USCS, the soil at the location was classified as silty clay to lean clay. This classification is the result of extensive field and laboratory research. In the study, a set of eight unique accelerograms were carefully chosen and used at the bedrock layer, perfectly coinciding with the seismic characteristics unique to the target geographic location. Surprisingly the study of surface response spectra revealed a significant amplification phenomenon that was present across all seven possible accelerograms and deviated just slightly from the fundamental period inherent to the site. The study's conclusions indicated that the computed spectral acceleration values, which notably fell within the range of 0.16g to 0.24g, surpassed the requirements established by the Pakistan Building Code.