Shear stress transfer across concrete-to-concrete interfaces: Experimental evidence and available strength models

This paper presents results of a database of interface shear experiments collected from the literature and analyzed to identify the main parameters affecting the strength of concrete-to-concrete interfaces subjected to shear loads and to gauge the reliability of major international codes and interface strength models. The database included 509 push-off and pull-off specimens, with steel reinforcement normal to the interface and subjected to monotonic pure shear loading. The experimental data were analyzed mainly in terms of interface type, clamping stress, concrete compressive strength, concrete unit weight, and steel strength. The analysis of the database revealed that clamping stress and interface type were the main parameters influencing the interface strength but that the concrete strength could play an important role as well. In contrast, it was found that the concrete unit weight appeared to have no effect on the interface strength. Of the code provisions considered, it was found that the American Association of State Highway and Transportation Officials' AASHTO LRFD Bridge Design Specifications shear friction equations were the most accurate at predicting the interface strength for all interface types and conditions, while the PCI Design Handbook: Precast and Prestressed Concrete and American Concrete Institute's Building Code Requirements for Structural Concrete (ACI 318-14) and Commentary (ACI 318R-14) equations tended to underestimate the strength, with the PCI Design Handbook being generally more accurate than ACI 318-14.