For PT bridges, the moment capacity by strain compatibility is based on the procedures outlined in the PCI Bridge Design Manual, Art. 8.2.2.5. In this case, all reinforcement (top and bottom) and all post-tensioning tendons are considered. By using an iterative approach the actual stress in each rebar row is calculated, and thus a much more accurate capacity is obtained. The calculations are based on the cylinder compressive strength of concrete, f'c, which is assumed to be equal to 0.8 times the cube compressive.