Deformability for prestressed concrete members with unbonded frp tendons

Because of FRP materials' linear elastic behaviour up to rupture without yielding, structural ductility or deformability is of main concern in prestressed concrete beams with bonded and/or unbonded FRP tendons. In this paper an attempt is made to make a comparative study of existing five categories of deformability indices for unbonded partially prestressed concrete (UPPC) beams with FRP tendons. Results show that the deformability index defined as the ratio of the production of the moment and deflection at ultimate to the corresponding value at cracking is consistently decreasing with the increase of combined reinforcement ratio. In addition, this index is sensitive to the change of factors that may influence the deformability of UPPC beams with FRP tendons.