EVALUATION OF CO LLAPSE MARGIN FOR RC FRAM ES DESIGNED BASE D ON IRANIAN SEISMIC CODE

One of the main goals of the seismic design philosophy is to design structur es so that the structural collapse to be prevented under intense ground motions. Therefore it is important t o quantify the margin of safety against structural collapse. Nonetheless due to high level of nonlinearity involved in vicinity of structural collapse the analytical m odeling and assessment is complex and demanding, and includes several sources of uncertainties. Although this issue has attracted considerable interest amon g seismic engineers and researchers during several past dec ades no standard method has been introduced. During the past few years FEMA has published a guideline for quantification of the building Seismic Pe rformance Factors, i.e. response modification factor, overstrength factor and displacement amplification fa ctor (FEMA, 2009). As part of the proposed methodology one can assess the structural collapse potential. The approach includes a combination of incremental nonlinear dynamic analysis (Vamvatsikos and Cornell, 2002) and suggested criteria based on semi-probabilistic method to evaluate Collapse Margin Ratio (CMR ).The main objective of this re search is to study the collapse margin ratio for re inforced concrete frame buildings designed according to Iranian seismic standard (Standard 2800). Incremmental dynamic analysis (IDA) is carried out using 22 scaled natural ground motion records. The study includ es RC moment resisting frames with 3, 6 and 10 stories c onsidering two types of soil classifications (Type II and III) and two alternatives of ductility levels (Inter mediate and high ductilties), according to standa rd 2800. It is concluded that the RC frame structures desig ned based on the Iranian Seismic code generallyy have sufficient margin against collapse based on the FE MA P695 approach. However the actual margin of collapse varies depending on the characteristics of the structures

Keywords:

Collapse Margin Ratio (CMR) , Incremental Dynamic Analyses (ID A) , RC Frames , Iranian Seismic Standard.