A tied-arch model is developed for the shear design of prestressed concrete members. The failure angle of the arch is calculated using conditions of equilibrium, and the angle of diagonal cracking failure
is predicted in terms of shear and longitudinal reinforcement. Comparisons with published test results indicate that the proposed tied-arch theory provides a more accurate prediction of shear strength when compared to the LRFD or AASHTO Specifications. The proposed model is useful in studying the interaction among the forces in the tie, shear reinforcement, and concrete strut of a member. While the tied-arch model can be used in both design and capacity rating of regular members, it is strongly recommended in the design and capacity rating of deep beams, and beam ends to include the contribution of shear reinforcement that is usually ignored in a typical strut-and-tie analysis. Examples for determining member capacity rating and shear design are provided.
