Siamak Sadeghi Arbatani - MSc Student, Marand Branch, Islamic Azad University
Mohammad Hossein Habashizadeh Asl - Assistant Professor, Marand Branch, Islamic Azad University

This paper investigates the effect of irregularity (mass eccentricity) on the general behavior of composite RCS special moment frames. composite RCS special moment frame system is composed of steel beams and concrete columns which is commonly resistant to the lateral load. The system is applied in low, medium and high seismic areas. Given that none of the previous works have studied seismic performance of these frames, it has been raised as a new research and the results will be innovative. For this, seismic performance of irregular RCS are examined by designing irregular composite RCS special moment frames in 3, 5, 10 and 15- story plans and three-dimensional modeling of RCS frames considering eccentricity of 5%, 10% and 15%. Results show that eccentricity reduces the frame lateral capacity and increases the plastic rotation. In addition, according to the examination of the stories relative displacements, the increase of eccentricity leads to the reduction of the stories relative displacement.

RCS moment frames, irregular, pushover analysis, plastic joints, dynamic analysis