Studying near fault endurance time acceleration function

Abstract

The Endurance Time (ET) method is a time-history based dynamic pushover procedure. In this method, the structures are subjected to gradually intensifying acceleration called an acceleration function. Then, their performances are assessed from linear to collapse level based on the interval time through which they can satisfy the required objectives. ET Acceleration Functions (ETAFs) are calibrated upon actual earthquake spectra compatible with the Iranian National Building Code (standard no. 2800). In this code, there is no distinction between far and near fault regions. ETAFs scale based spectrum increases uniformly at all periods as the time passes which is why this uniform increment is not desirable in near fault earthquakes. As the rupture propagation is oriented towards a site, near fault earthquakes have further spectral acceleration in the period over 0.6 sec compared to far fault earthquakes. The shape of the spectrum becomes richer over long periods as its level increases. In this research, ETAFs are presented for near fault target spectra, provided by Abrahamson-Silva attenuation relations. These relations have been modi ed by Somerville near fault correction coe cients. According to the results obtained in this research, while the new acceleration function can model directivity eff ects at higher periods, it also satis es endurance time concepts.