From around 2010, the replacement of deteriorated RC slab in composite girders is began to be implemented largely. One of the main problems of replacement work is the lack of ultimate strength of compressive flanges when the deteriorated RC slabs are removed. Therefore, it is required to strengthening of the compressive flange before removing the slab. In this study, in order to improve the load-carrying capacity of the compressive flange, that is the outstanding plate which simply supported at three edges, the angle lumber strengthening of the free edge in the outstanding plate by using Thread Rolling Screws, TRS. The proposed method was verified by the compression tests of the cruciform-sectional column specimen strengthening by the angle lumber with TRS.
