SEISMIC PERFORMANCE OF STEEL MOMENT FRAMES BASED ON THEIR IMPORTANCE ACCORDING TO THE IRANIAN SEISMIC CODE

The current Iranian Seismic Code, for seismic loading and analysis of structures, (Standard no. 2800) considers linear elastic analysis to be adequate for structural and seismic response prediction for a majority of structures. In this regulation, an importance factor, I, is considered to improve the performance of buildings based on their importance. Linear analysis is inadequate for observing structural performance during earthquakes, because proper seismic behavior and the stability of structures are not just governed by strength; structures need to resist determined amounts of force and should be able to displace determined amounts of displacements. On this basis, it is expected that by using importance factor, I, in linear analysis, the structures will behave properly, and after earthquakes, will present a desired level of performance. New seismic regulations, such as FEMA 356 and the Iranian Seismic Rehabilitation Guideline, use a performance-based design method; nonlinear analysis methods are the main tools of these codes. Also, the main objective of this research is to evaluate the seismic performance of buildings, with dierent importance levels, designed according to the Iranian Seismic Code, using the Iranian Seismic Rehabilitation Guideline. In this research, a set of structures, with dierent categories of occupancy and dierent numbers of stories, are designed according to the Iranian Seismic Code. The seismic performance levels of the mentioned structures are evaluated using nonlinear static analysis (pushover), based on the Iranian Seismic Rehabilitation Guideline. The results show that the low- and medium-rise buildings behave to a life safety (LS) performance level. In high-rise buildings, with medium importance, the required performance level (LS) is not achieved, and in very high importance (essential) buildings, the required performance level (IO) is not achieved. Therefore, increasing the importance factor, I, does not necessarily lead to improvement in performance levels, but leads to an increase in structural weight; this could be a noneconomic decision. By using non-linear analysis in parts of the structure, in which performance level is not met, the structure would be strengthened and achieve the required level of performance.