A Kheyroddin - Associate professor, School of Civil Engg. Semnan University, Semnan
A kargaran - M.Sc. of Earthquake Engineering and Instructor of Islamic Azad University-Semnan Branch, Semnan

Civil engineering structures as well as office or apartment building are affected by earthquakes. A common cause of failure seems to be shear stress. The earthquake forces developed at different floor levels in a building need to be brought down along the height to the ground by the shortest path. Short column phenomenan is one of the effective causes of buildings failure in past earthquakes. This destructive phenomenon is due to column heighf difference in a story level that is predominantly because of localing building on sloppy ground. These buildings have unequal height columns along the slope, which causes ill effects like twisting and damage in shorter columns. In some buildings, few or no walls are provided at the first story (pilot). In the structures with difference in story level, major problems is due to discontinuity of floor diaphragm that causes significant changes in period, stiffness distribution of earthquake force and seismic loading of structures . In this research, at first, seismic behavior of short column phenomenon is determined, then, nonlinear behavior of reinforced concrete short columns in 4, 8 and 10 story structures with story level difference is investigated. Short columns and mentioned structures are analysed under the earthquake record of Elcentro with different peak ground acceleration with IDARC software which is nonlinear dynamic analysis program. In this investigation, the results of maximum response, base shear, global damage index and displacement time history and effect of short column in structural failure is evaluated.

building with different floor, reinforced concrete, short column, damage index, nonlinear dynamic analysis