Comparison of seismic performance of steel frames with regularity and irregularity in Elevation

Irregularities instruments,as a result of the limitations of architectural,performance and finance,are one of the issues considered unavoidable in many urban structures. this study examines the seismic behavior of steel structure with vertical irregularities,including mass,strength and stiffness irregularities. structural steel moment frames as 2d models were designed,and using nonlinear static and dynamic analyses,seismic demand frames are calculated. columns of the middle storey in a regular state have attracted less energy,while irregular structures columns of middle- storey absorb almost 2 times higher energy. if irregular floor is at a higher storey,acceleration in control point is higher. existence of soft and weak storey,increases the higher mode effect on mass participation ratio.