Interface shear behaviour of ultra-high performance concrete under combined shear and lateral loads

The use of ultra-high performance concrete (UHPC) in construction has expanded in recent years due to its superior mechanical properties, including enhanced compressive strength and improved post-cracking tensile resistance and deformation capacity. Structural components constructed with UHPC have exhibited improved response attributes in applications where conventional concretes have demonstrated deficiencies, such as precast concrete component connections where interface shear plays a key role in transferring loads and maintaining structure integrity. This study investigates the interface shear resisting behaviour of monolithically-cast UHPC push-off specimens subjected to combined shear and lateral loading. A comparative evaluation of existing shear strength estimation models is presented and the applicability of classical concrete failure criteria for unreinforced UHPC interfaces is assessed. The findings presented offer insight into the shear transfer mechanisms of unreinforced UHPC interfaces under varied stress conditions, demonstrate the relationship between interface confining pressure and interface shear strength, and provide a foundation for advancing design models for UHPC structural connections. • Push-off tests on UHPC specimens subjected to combined shear and lateral loading. • Investigation of UHPC shear strength, failure mechanism, and load-shear displacement responses. • Influence of lateral stress conditions on interface shear resisting performance of UHPC. • Evaluation of shear strength prediction models using experimental results. • Application of classical concrete failure criteria to unreinforced UHPC interfaces.