The studies made and the findings from the National Cooperative Highway Research Program (NCHRP) project 12-61, “Simplified Shear Design of Structural Concrete Members,�? are discussed. The stated objective of this NCHRP project was to develop practical procedures for the design of shear reinforcement in reinforced and prestressed concrete bridge girders. The motivation was that many bridge designers perceive the general shear-design procedure of the sectional design model in the American Association of State Highway and Transportation Officials�? AASHTO LRFD Bridge Design Specifications to be unnecessarily complex and difficult to use. This general procedure unifies the shear design of both prestressed and nonprestressed members and allows the design for much higher shear stresses than is permitted by AASHTO’s Standard Specifications for Highway Bridges. Reviews and evaluations are made of the shear-design methods of several leading codes of practice and influential researchers. Based on this assessment, a review of field experience, and comparisons with a large experimental database, criteria are developed for the simplified provisions, and the two resulting changes to the AASHTO LRFD Bridge Design Specifications shear-design provisions are described. The simplified provisions are similar in concept to AASHTO’s Standard Specifications for Highway Bridges, contain a new expression for the web-shear cracking capacity, and use a variable-angle truss model to evaluate the contribution of shear reinforcement. An xample illustrates the use of the simplified procedure
