Ahmad Nicknam - Faculty member of civil engineering, Iran University of Science and Technology (lUST
Mohammad Javad Asgari - M.Sc. students of civil engineering, Iran University of Science and Technology (IUST)
Ehsan Yousefi Dadras - M.Sc. students of civil engineering, Iran University of Science and Technology (IUST)

Selecting sufficient number of appropriate ground motions compatible with regional tectonic condition is a major step in Incremental Dynamic Analysis of structures (IDA). The article is intended to compare the nonlinear structural response of the selected four frames (two steel moment-resisting frames andtwo RC Special Moment Frames) through performing IDA using the traditional and Conditional Spectrum methods. First, the CMS and CS approaches are briefly explained and discussed. Theselected frames are dynamically nonlinearly analyzed using the traditional IDA and CS methods forfour hazard levels (50%, 10%, 2%, and 1 %). The plots of results obtained from the two approaches, in the form of mean curve, are compared and assessed. It is concluded that the CS method ends up with more reasonable results except in case where the frame shows structural instability as the result of using CS method. The necessity of performing more research work in this area is highlighted.

IDA, spectral shape, ground motion selection, Non-linear dynamic analysis, CS