This paper investigated the effect of natural period ratio of RC frame to steel roof on seismic response of steel roof construction with brim-slab installed with friction dampers. A modeling of the school gymnasium was adequately carried out for a three-dimensional inelastic response analysis. The seismic responses of the gymnasia with different natural period ratios caused by the changes of steel roofs and brim-slabs were investigated. The damage to the frames of these models were analyzed and the dissipated energy ratio of the friction dampers to earthquake input energy were also shown in this paper. Finally, it was clarified that the natural period ratio was effective for the seismic design of such gymnasia.
