Interface Shear of Ultra-High-Performance Concrete

Due to its distinct mechanical properties, ultra-high-performance concrete (UHPC) behaves differently than conventional concrete when subjected to interface shear demands. The use of UHPC in primary structural elements, for which interface shear resistance can be an important structural response, is growing as UHPC-class materials become more readily available. Structural design provisions for the interface shear capacity of UHPC are needed. This research conducted 11 interface shear tests of monolithically cast UHPC and combined those results with other tests from the literature to develop a predictive model for UHPC. The interface shear capacity was studied by conducting tests with steel reinforcement of varying yield stress and reinforcement ratios at the interface. A predictive model was developed indicating that the total tensile resistance across the shear interface is a critical parameter in determining the peak shear resistance. This includes the tensile resistance of both the reinforcing steel and UHPC. Design guidance for the interface shear resistance of UHPC is also proposed. Keywords: interface shear; structural design parameters; tensile behavior; ultra-high-performance concrete (UHPC).