In this study, experimental and analytical investigations were conducted regarding a flexural reinforcement design of reinforced concrete (RC) beams strengthened with continuous fiber sheets. This paper presented methods for analyzing the bond behavior at the interface of concrete and the sheet by means of a truss model, and for calculating the ultimate bond strength of strengthened beams based on the flexural analysis under Bemoulli-Euler's hypothesis and the concept of local bond stress. As a result, it was shown that the ultimate bond strength of the sheet can be calculated with reasonable accuracy by considering the scale effect of the member on the tensile strength of concrete.