A. A Golafshani - Associate Professor, Sharif University of Technology, Tehran, Iran
H Ebrahimian - PhD candidate, Sharif University of Technology, Tehran, Iran
S. A Tabandeh - M.Sc. student, Sharif University of Technology, Tehran, Iran

Selection of recorded ground motions is an important consideration. Most of the current building codes enforce the requirements to match the event characteristics, as well as ensuring that the median spectrum exceeds the target Uniform Hazard Spectrum (UHS) ranging from 0.2T1 to 1.5T1. Performing the analysis with respect to the same code’s criteria and with different sets of selected ground motions, will result in responses with considerable variability. These facts show the significance of considering a proxy for spectral shape. Indeed, there is no single earthquake that is likely to produce a spectrum as high as UHS over all periods. So, the Conditional Mean Spectrum (CMS) is proposed as a substitution which considers the spectral shape through an indicator named “epsilon”. In this paper, the advantages of CMS over UHS are investigated for a hypothetical site.

UHS, Spectral Shape, CMS, Epsilon