Shear behavior of rib-treated interface between ultra-high performance concrete and normal concrete

The present study investigates the interfacial shear performance between ultra-high performance concrete (UHPC) and normal concrete (NC). To this end, 13 UHPC-NC direct shear specimens were designed and fabricated. Through push-out tests, the influence of UHPC rib width, height, and spacing on the interfacial failure mode and shear bearing capacity was discussed. Furthermore, a finite element model of the UHPC-NC specimens was established using the software ABAQUS, and a parameter analysis was conducted. The results indicate that the failure modes of the ribbed UHPC-NC interface mainly include: complete interface failure and UHPC ribs sheared off; partial interface failure and partial failure of NC embedded between UHPC ribs; and partial interface failure and complete failure of NC embedded between UHPC ribs. The specimens with rib widths of 10 mm primarily exhibit the first failure mode, while specimens with rib widths of 15 and 20 mm correspond to the latter two failure modes. It has been demonstrated that the shear capacity and slip of the interface increase with an increase in rib width and spacing, thereby demonstrating enhanced ductility. When the rib width is 10 mm, increasing the rib height has little effect on the shear bearing capacity, while when the rib width is 15 and 20 mm, increasing the rib height can improve the shear bearing capacity. In addition, increasing the number of ribs can improve the shear bearing capacity, but with the increase of the number of ribs, the effectiveness of bearing capacity enhancement significantly decreases.