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This paper presents an analytical model for predicting the short and long-term prestress losses in reinforced concrete (RC) beams strengthened with prestressed carbon fiber reinforced polymer (CFRP) sheets/plates. The long-term prestress loss model is developed by treating the strengthened beam as two sub-elements: an RC beam and a prestressed CFRP sheet/plate, connected through an adhesive bonding layer. Through force equilibrium and displacement compatibility of the two sub-elements, the influences of concrete shrinkage, concrete creep as well the interlayer slip between the RC beam and the CFRP sheet/plate on the prestress losses of CFRP are modeled using an incremental model. For a post-tensioned system with strong end anchorages, closed-form solutions for the prestress losses due to creep and shrinkage of concrete are obtained. The reliability of the proposed analytical model is validated through comparisons with previous test results reported by the authors and others research groups. The maximum difference between the experimentally observed values and the predicted values for the long-term prestress losses was found to be only 2.2% of the initial prestress of the CFRP. [ABSTRACT FROM PUBLISHER]

Intermediate crack-induced debonding is often a dominant failure mode in fiber-reinforced polymer (FRP)-strengthened reinforced concrete (RC) beams in flexure. It has been extensively studied for RC beams externally strengthened with unstressed FRP laminates. However, very little work has been done on FRP debonding for RC beams strengthened with prestressed FRP. This article presents a sectional analysis model for predicting the flexural capacity of RC beams strengthened with prestressed FRP laminates with due consideration of different failure modes. The focus is placed on the effective strain in the prestressed FRP at the ultimate states of intermediate crack-induced debonding or rupture of debonded FRP. Through back-calculation analysis of 51 RC beams strengthened with post-tensioned FRP laminates, a model for predicting the effective strain of prestressed FRP for ultimate strength prediction based upon sectional analyses was developed and validated through comparisons with test results. [ABSTRACT FROM AUTHOR]