It is expected that Ultra high strength Fiber reinforced Concrete (UFC) is effective for seismic retrofit of medium-rise old buildings in the light of not only an improvement of strength but ductility. This paper presents the behavior of old RC column retrofitted by precast UFC wing wall and the observed failure mode by experimental tests. It is confirmed that the difference of connection detail between RC and UFC wing wall influences the effect of seismic retrofit in the test. The simple shear transfer mechanism is proposed and consists of the diagonal compressive strut in the wing walls and the tensile strut due to main bars in RC column for the specimen connected UFC wing wall using epoxy resin adhesive. Based on the proposed shear transfer mechanism, the evaluation method for ultimate strength for RC column with UFC wing wall is suggested.
