An investigation on the effect of the near-fault earthquakes on the seismic behavior of RC Moment Resisting Frames (MRFs) designed based on Iranian seismic code (standard no. 2800)

TL;DR

This study evaluates the seismic performance of Iranian-designed RC moment resisting frames under near-fault earthquakes, revealing that current code modifications may be insufficient to ensure safety during such impulsive events.

Contribution

It provides a nonlinear dynamic analysis of RC MRFs designed per Iranian code, highlighting potential inadequacies in current seismic provisions for near-fault earthquake effects.

Findings

Structures often fail to meet life safety criteria.

Some buildings do not achieve collapse prevention limits.

Current code modifications may be inadequate for near-fault seismic effects.

Abstract

Past severe earthquakes, such as Bam earthquake of 2003 and Tabas earthquake of 1978, have demonstrated that many cities in Iran are prone to be struck by near-fault earthquakes. Such earthquakes are impulsive in nature, and therefore, they are more destructive than the ordinary ground shaking. In the fourth edition of Iranian seismic code (Standard No. 2800), some changes, including a modification factor for the elastic acceleration response spectrum (EARS) have been recently recommended to reflect the effects of such probable near-fault earthquakes for the designing procedure. In this study, a numbers of 2D RC moment resisting frames (MRFs), from four to twelve story buildings, are designed linearly based on Iranian National Building Code (INBC) and Standard No. 2800 as well. Subsequently, their nonlinear models are reproduced for conducting nonlinear dynamic time history (NDTH) analysis. For this purpose, twenty impulsive ground motions are selected and scaled to be compatible with the design basis earthquake (DBE) spectrum of the abovementioned code. It is concluded that the seismic performance of the analyzed structures are not satisfactory at all; no buildings are successful to satisfy the life safety (LS) performance level posed by guidelines such as ASCE41-06 or ASCE41-13. Moreover, it is worth mentioning that even collapse prevention (CP) limit states are not also met in some cases. Therefore, the recently added modifications in the Standard No. 2800 may be inadequate to incorporate the near-fault earthquakes' effects.