NCHRP Project 12-56, Application of Load and Resistance Factor Design Specifications to High-Strength Structural Concrete: Shear Provisions

Abstract

The load and resistance factor design (LRFD) specifications in the current AASHTO LRFD Bridge Design Specifications limit the compressive cylinder strength to 10 ksi in relationships for calculating shear design strength, whereas concrete compressive strengths close to twice this level are commercially available in some parts of the United States. To overcome this limitation, allowing the same-size structural sections to span longer distances or carry higher loads, NCHRP has funded Project 12-56, Application of the LRFD Bridge Design Specifications to High-Strength Structural Concrete: Shear Provisions. In the experimental component of this project, 12 prestressed concrete bridge girders 52 ft long and 6 ft deep are being subjected to a uniformly distributed load until failure in shear. The primary variables in this study are concrete strength (ranging from 10 to 18 ksi), the maximum shear design stress (700 to 2,500 psi), strand anchorage details (straight, unbonded, and draped), and end reinforcement de...