Flexural behavior of damaged RC beams strengthened with prestressed UHPC layer

Abstract

Based on ultra-high-performance concrete (UHPC) and prestressed technique, a new flexural strengthening technology using a prestressed UHPC (PUHPC) layer for the damaged reinforced concrete (RC) structure was proposed in this study. To investigate the flexural strengthening efficiency of PUHPC layer, the bending tests of six beams were carried out in this study, including four PUHPC strengthened RC beams with different pre-damaged degrees (PUB), one reinforced UHPC (RUHPC) strengthened control beam (RUB) and one unstrengthened RC control beam (CB). The experimental results showed that the PUB was typical bending failure. The cracking load and ultimate load of PUB increased by 145% to 190% and 90% to 94% compared with that of CB respectively. Similarly, 98% and 38% of improvement of the characteristic loads comparing with RUB were observed. Moreover, the post cracking stiffness of PUB were significantly improved compared with CB and RUB, while the ductility indexes were decreased. However, with the increase of the pre-damaged degree of RC beam, the cracking resistance, flexural stiffness and ductility of PUB decreased correspondingly. It is worth mentioning that the interface between PUHPC layer and RC beam has a high bond strength, and the slight slip at the interface did not lead to debonding failure during the bending test. Also, the calculation model for predicting the ultimate flexural capacity of PUB was developed, which yielded promising predictions with reasonable accuracy.