Effect of Tendon-Related Variables on the Behavior of Externally CFRP Prestressed Concrete Beams

This work assesses the flexural performance of prestressed concrete beams with external carbon fiber-reinforced polymer (CFRP) tendons, focusing on tendon-related variables. A finite element analysis (FEA) method is verified. A numerical parametric analysis of prestressed concrete beams with external CFRP tendons is carried out. Four tendon-related variables are considered, namely, the area, initial prestress, depth and elastic modulus of tendons. The analysis shows that flexural ductility decreases as the tendon area, initial prestress or elastic modulus increases but is insensitive to the tendon depth. The ultimate tendon stress increment (Δσ) is influenced by all of the four variables investigated. JGJ 92-2016 (Chinese technical specification for concrete structures prestressed with unbonded tendons) significantly underestimates Δσ and, hence, is over-conservative for the strength design of these beams. An equation is proposed for calculating Δσ, taking into account all four variables investigated. An analytical model is then developed to estimate the flexural strength (M) of prestressed concrete beams with external CFRP tendons. The proposed analytical model shows good agreement with FEA, i.e., the mean discrepancy for Δσ is 0.9% with a standard deviation of 11.1%; and the mean discrepancy for M is -1.6% with a standard deviation of 2.1%.