When buildings are seismically retrofitted, new members are connected to existing members by roughened concrete surface. However, there are few studies on roughened concrete. To evaluate the shear strength of the roughened concrete, the shapes of roughened concrete were measured using 3D scanner, then we conducted the shear loading tests. As a result, failure modes were supported failure and shear failure when rcr were respectively 0.1 to 0.3 and 0.5 to 1.0. This paper focused on supported failure, a shear strength formula constructed considering the concrete compressive and the vertical projection area. The proposed formula could estimate the test results.
