Experimental research on the mechanical property of unbonded prestressed continuous beams reinforced with CFRP sheet

Ten unbonded prestressed concrete continuous beams, which reached the strength limit states, were reinforced with Carbon Fiber Reinforced Polymer (CFRP) sheet. An experiment on these 10 beams was done. The plane section assumption was testified, the stress of unbonded tendons increased, and the distribution and the development of the crack, the development of the deformation at the mid span during loading and the failure characteristics of beams were obtained. Based on test results, calculation methods of flexural carrying capacity were set up with the influence that the original beams had been subjected to load considered. The calculation formula of the coefficient of the moment modification was presented, in which the object of moment modification was the summation of elastic calculated moment of critical section at intermediate support under ultimate load M_Load and the secondary moment M_sec due to prestress (M_Load+M_sec), and the variable was the relative plastic rotation.