Modifications to ACI 318 shear design method for prestressed concrete members: Detailed method

This paper proposes modifications to the methods for shear design of prestressed concrete one-way members specified in American Concrete Institute’s Building Code Requirements for Structural Concrete (ACI 318-19) and Commentary (ACI 318R-19) to increase applicability. The current ACI 318 shear design methods have been widely used and have a history of demonstrated safety and reliability. However, there are long-standing concerns re­garding the cumbersome computational procedures spec­ified in ACI 318, as well as the inability of the ACI 318 shear design methods to capture key influential factors. This paper provides a brief history of changes made over several decades within ACI 318 for prestressed concrete shear design and critical issues raised in previous studies. While maintaining the philosophy and safety priorities of the original pioneers in the development of shear design for prestressed concrete members, the proposed changes simplify the calculation process and provide analytical accuracies comparable to the current ACI 318 methods. These changes are affirmed by comparing the results of the modified methods with data from an extensive shear database of prestressed concrete component designs that vary in dimensional detail and material properties and shear strengths estimated using current ACI 318 methods.