Flexural Strength of Prestressed Concrete Sections by Programmable Calculator

' t has always been recognized that the approximate Eq. (18-3) in ACI 318-77' for the stress in bonded prestressing steel at flexural ultimate, f,,, was in general conservative. A more precise value for f, and hence for the flexural strength, can be obtained by solving the equations of equilibrium of forces and of compatibility of strains across the section, making use of the actual stress-strain relationship for the prestressing steel. Until the advent of the computer and the programmable calculator, this was a time-consuming process and hence was little used.