Beams prestressed with partially bonded fiber-reinforced plastic (FRP) tendons have high strength and rotation capacity but cannot be modeled by conventional techniques. Herein, it is assumed that all deformation takes place at cracks between rigid bodies. By setting up appropriate compatibility and equilibrium equations, the behavior at a single crack can be modeled, which then allows predictions to be made as to which of four possible events will occur next. These lead either to beam failure, or to changes in the geometry that can be analyzed using the same techniques. Comparisons are made with test results, and reasonable agreement is shown.