A.A Fallah - Ph.D. Candidate, Science and Research Branch Islamic Azad University, Tehran,
A Sarvghad Moghadam - Associate Professor, Civil Engng. Dept., International Institute of Earthquake Engineering and Seismology, Tehran,
A Massumi - Assistant Professor of Structural Engineering, Graduate School of Engineering, Tarbiat Moallem University of Tehran (Kharazmi), Tehran,

In almost all codes of practice for seismic resistant design of buildings, a behavior factor is used to reduce design base shear. The behavior factor is affected by several parameters such as ductility, overstrength and redundancy reduction factors. There are two common approaches to assess the effects of redundancy on the strength of a structural system, which are as follows: Static Pushover Analysis and Incremental Dynamic Analysis. The two indices: redundancy strength coefficient and redundancy variation coefficient have been introduced to measure these effects. Simplified methods are developed and presented to calculate these parameters. In this paper the redundancy strength and the redundancy variation parameters are evaluated for the reinforced concrete plane frames with different number of stories, bays and ductility capacities. The investigations indicate that these two parameters are mainly the results of redundancy reduction factors.

redundancy, behavior factor, ductility, concrete frames, redundancy strength index, redundancy variation index