Moment redistribution and ductility of RHSC continuous beams strengthened with CFRP
In continuous concrete beams, ductility allows redistribution of moment between the negative and positive moment zones. Although many in situ reinforced high strength concrete (RHSC) beams are of continuous construction, there has been very little research on such beams with external reinforcement. Due to premature debonding failures and the linear stress-strain characteristics of fiber reinforced polymer (FRP) up to failure, the ductility of plated members and their ability to redistribute moment is less than that of unplated RC beams. The present study examined the responses of RHSC continuous beams, in terms of enhancement of moment and load capacity, moment redistribution, and different types of ductility. Thickness of carbon FRP (CFRP) sheets, strengthening of both the hogging and sagging region, and end anchorage technique were the main parameters investigated. Various monitoring devices were used to monitor the loading history of the beams. Increasing the number of CFRP sheet layers increased ultimate strength, and decreased ductility, moment redistribution, and ultimate strain on CFRP sheets. Additionally, using end anchorage increased ultimate strength and moment redistribution. The moment enhancement ratio of the strengthened beams was significantly higher than the ultimate load enhancement ratio in the same beam. The proposed equation for converting the energy ductility index to the displacement ductility index provided accurate results.
RHSC continuous beam; CFRP; End anchorage; Moment redistribution; Ductility.