Estimation of shear and axial force for steel column joints and seismic strength of multi-story steel moment resisting frames with new column support system

In the steel frames, the column base is allowed to yield after beam yielding subjected to large earthquake in Japanese design codes such as "The Building Standard Low of Japan" by Building Center of Japan. If the frames have unexpected seismic horizontal force, the soft story mechanism may occur. To prevent the plastic collapse of the column on 1^st story, our previous paper suggested the new column support system on 1 ^st story, which consist of the reinforced concrete downside column and the steel topside column. In this paper, the virtual work method is applied to estimate the damage distribution and the collapse deformation capacity of the steel moment resisting frames with these support systems, and the shear and axial demands the column joints on 1^st story are clarified.