Shear Stress Transfer Across Concrete-to-Concrete Interfaces: Experimental Evidence and Available Strength Models

Abstract

■ The analysis results identified the best-performing models for different scenarios, critical knowledge gaps and future research needs, and recommendations for ways current models could be further improved to achieve higher performance. In structural concrete, shear force must sometimes be transferred across an interface between two materials. The interface may be between two faces of a crack in monolithic concrete, two concretes cast at different times, or steel and concrete. Such shear transfer is usually modeled as a shear friction phenomenon. This approach, initially proposed in the 1960s by Birkeland and Birkeland, states that the shear strength of a concrete-to-concrete interface comes from the contribution of several resisting mechanisms, namely the cohesion between particles, the friction between concrete parts, and the shear force resisted by the reinforcement crossing the interface. The empirical parameters involved have been calibrated against experimental evidence by numerous investigators. Today, the shear friction theory is widely accepted and has been adopted by most design codes, including the PCI Design Handbook: Precast and Prestressed Concrete, the American Association of State Highway and Transportation Officials’ AASHTO LRFD Bridge Design Specifications, and Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14).