Endurance time method is a new method of seismic analysis in which the structure is subjected to an increased dynamic excitation whose intensity gradually enhances over time. The response of structure is investigated over time and based on the response corresponding to different levels of excitation intensity, strengths, weaknesses, and performance of the structure were evaluated. In this research, according to the rules of regulations, two 5- and 8-storey buildings were linearly analyzed and designed applying ETABS software and with medium and special ductility. Then, a sample frame was separated from the structure and overall, four concrete frames of 5 and 8 floors with medium and special ductility were analyzed by endurance time method. The ETA20-KD durability stimulation function was applied to evaluate these frames. Nonlinear hinges of structural components were defined according to instruction for seismic rehabilitation of existing buildings No. 360. The results of this study presented that concrete frames with special ductility have less damage and longer endurance time than those with medium ductility. So that the failure of a 5-storey building with medium and special ductility occurred at 11.64 and 20 seconds, respectively, and the failure of an 8-storey building with medium and special ductility took place at 10.21 and 13.08 seconds, respectively
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