Method of reinforcement for joints between steel roofs and RC columns in existing buildings

•Validation of reinforcement effect in the roof joint between RC frame and steel roof.•Reinforcement around the entire top of the RC column prevent concrete edge failure.•Detail of reinforcement to obtain reaction force from main frame is considered. The aim of this study was to validate the reinforcement method used for joints connecting a steel roof and a reinforced concrete (RC) frame in existing buildings based on a series of cyclic loading tests. Three reinforcement methods were investigated in the study: one using a steel jacket and high-strength steel rods (Type-1), another using a steel jacket and post-installed adhesive anchors (Type-2), and a third using a steel plate and post-installed adhesive anchors (Type-3). The results obtained show that the Type-1 method is most effective in increasing force, because shear force can be transferred from the RC frame to the steel roof; thus, a steel jacket can support the entire top of the RC column and integrate the roof joints into the RC frame. The Type-2 and Type-3 methods, however, are not effective in the reinforcement of RC columns because shear force cannot be transferred, and concrete failure occurred easily.