Force transfer mechanism and shear performance of perfobond strip connector encased in UHPC

This study aims to investigate the load-transfer mechanism of Perfobond Leiste (PBL) shear connectors between ultra-high performance concrete (UHPC) slabs and steel beams. Twelve standard push-out specimens were designed and tested to examine the effects of the number of holes, hole spacing, steel fiber content, and perforating rebar diameter on the shear performance of PBLs. The failure modes, load-slip curves, and shear performance of the specimens were analyzed via test results. Additionally, based on a validated finite element analysis model, the load-transfer mechanism of PBL shear connectors was further investigated, and the influences of hole diameter, UHPC strength, and perforating rebar yield strength were explored. The results indicated that steel fibers and perforating rebars significantly influenced the failure modes of the specimens. As the steel fiber content increased from 0 % to 3 %, the initial shear stiffness, shear capacity, and failure slip increased by 184.9 %, 253.4 %, and 66.7 %, respectively. When the number of holes increased from 1 to 3, the average shear stiffness and shear capacity per hole decreased by 15.4 % and 7.2 %, respectively. For double-hole PBL connectors, the initial load-sharing ratio between the two holes was approximately 0.7, increasing to 0.9 at peak load. The recommended hole spacing for PBLs in UHPC was 120 mm, as it provided the best shear performance. Given that the group effect had a more significant impact on shear stiffness than shear capacity, it is essential to account for reduction factors when calculating the shear stiffness of multi-row PBL configurations. Based on experimental results and finite element analysis, improved prediction equations for the shear stiffness and shear capacity of single-row and multi-row PBLs encased in UHPC were proposed, and their accuracy and applicability were validated using an experimental database.