Sažetak The assumption of seismic load by reinforced concrete frames, in cases when load can not be assumed by walls, is analyzed. The use of plastic theory in calculation is described and advantages of this theory are outlined. A special account is given of possible structural failure mechanisms. System modeling proposals aimed at obtaining the desired failure mechanism are presented. The author presents some recent theoretical studies, results of which have brought about changes in some standards, especially in the U.S.A.