Ehsan Danesh Dezfuli - Department of Civil engineering, Qazvin Branch, Islamic Azad universit, Barajin, Qazvin,Iran
Armin Aziminejad - Assistant Professor, Department of Civil engineering, Science and Research Branch, IslamicAzad university, Tehran, Iran

The Irregular buildings make up a large portion of the urban infrastructure. The presence of irregular ties can be due to architectural and user changes in the building stories. The main objective of this article is evaluate seismic performance of structures with vertical irregularities. The seismic responses are obtained by enveloping the peak inelastic responses resulting from the pushover analyses according to the provided pattern in ASCE/SEI 41-06 standard. To verify and appraise the procedure, it is applied to the 10, 15, and 20-storey models with irregular distribution of mass, stiffness and strength along the height. The results from the pushover procedure are compared with the resultsobtained by the nonlinear response history analysis (NL-RHA). The results of the research reveal that the seismic response of building structures is more sensitive to stiffness irregularities than to mass irregularities and strength irregularities. The Nonlinear static procedure that proposed in standard can predict to a reasonable accuracy the peak inelastic responses, such as plastic rotations of hinges, story drifts and shearstories in vertically irregular structures

Irregularity in elevation, Seismic performance, Pushover analysis, Nonlinear responsehistory analysis, ASCE ، SEI 41-06 standard