Estimation of ultimate seismic capacity and column demand of multi-story steel moment resisting frames with new column support system to fishbone-shaped frame

For E-Defense project, it was shown that the soft story mechanism on 1st story occurred when the 4 story steel moment resisting frame with fixed base column was subjected to huge seismic force. To prevent the plastic collapse of the column on 1st story, our previous paper suggested the new column support system on 1st story, which consist of the reinforced concrete downside column and the steel topside column. In this paper, the fishbone-shaped frames are applied to estimate the damage distribution and the collapse deformation capacity of the steel moment resisting frames with these support systems, and the column and beam demands to keep the columns elastic are clarified.