This study experimented damaged wooden flexural member after strengthening of traditional wooden structure with steel plate, and the following structural behaviors and strengthening effects were examined. 1) As a result of wooden flexural member, the specimen that the damaged wood was reinforced with steel plate was expected to have strengthening effects with increase of load level, initial and post yield stiffness. Non-reinforced standard specimen had flexural crack at the upper part from initial period of loading and progressed to destruction, but specimen reinforced with steel plate deflected by bending from the left side of the specimen due to strengthening effect and bending failure with damage of reinforcing materials were found. Therefore, it was considered that strengthening effects were exerted from the initial load level after strengthening. 2) strengthened specimen showed 2~45% increase of yield load and 6~73% increase of ultimate load compared to standard specimen 3) The steel plate in strengthened specimen increased structural performances including yield and ultimate load by reinforcement using bolt and nail rather than using only bolt. 4) Ductility factor of the strengthened specimen was 7~13% reduced in type I and was similar to that of Type II. It was considered that the specimen reinforced with steel plate showed increase of load but no great increase of deflection after yield load. 5) The stiffness of the strengthened specimen showed 27~36% increase in Type III compared to standard specimen and Type I and Type IIshowed similar or a little reduced stiffness to the standard specimen. In addition, the stiffness of plastic region was increased as the protruded length ratio increased and the load tended to be increased compared to the increase of deflection after yield load.
As a result of experiment to wooden flexural member with the damage of wooden structure strengthened by steel plate, it was found that strengthening using steel plate was expected to increase of stiffness of initial and plastic region, ductility, yield load and ultimate load.
In addition, as the strengthening using steel plate could accomplish internal lift control effects of flexural, the strengthening by combining encased carbon bar, steel plate, bolt and nail on the properties of natural wood will be desirable.