Unified Bending Strength Design of Concrete Members: AASHTO LRFD Code

This paper summarizes the procedure for the computation of nominal bending resistance of reinforced, prestressed, and partially prestressed concrete members according to the 1994 “AASHTO LRFD Specifications for Highway Bridge Design.” The cases of rectangular or flanged sections, underreinforced or overreinforced, with a combination of reinforcing bars and prestressing tendons, whether bonded or unbonded, are covered. Provisions on limiting the flexural reinforcement adopted in the new specifications are summarized. They address minimum and maximum levels of reinforcement in flexural members, the percent of moment redistribution in continuous bending members, and the prediction of stress at ultimate in bonded and unbonded tendons. The provisions are nondimensional and can be applied to any code. Logical flowcharts showing the various computational steps are provided, and examples illustrating the procedure are developed.