On the effect of initial strain on resistance moment of RC beams flexural strengthened with FRP

The initial strain always occurs during strengthening RC beams. The purpose of this paper is to investigate the effect of initial strain on resistance moment of RC beams flexural strengthened with FRP. An equation to calculate the initial strain was developed. Then the effect of initial strain, the strain of FRP, the depth of neutral axis, resistance moment, at which the strengthening structures are failed, was discussed, and the different influence factors have been investigated, such as initial moment, ratio of steel reinforcement, ration of FRP reinforcement. Finally, based on these theoretical analysis, a modified computing method was developed, in which a revised FRP strain factor could be derived to be included in the current design equation.