Experimental and numerical investigation on optimized ultra-high performance concrete shear key with shear reinforcement bars

Over the last decade, ultra-high performance concrete (UHPC) has been used in highway bridge connections between deck panels and girders due to its superior compressive and tensile strengths, significant tensile toughness, and excellent long-term durability. However, there are limited studies and discussions on the UHPC shear key's design with or without shear reinforcement bars (SRBs) applied for adjacent girder bridges. This study aimed to numerically and experimentally investigate the effectiveness and functionality of SRBs used in an optimized UHPC shear key connection (abbreviated as OPT-SK) developed by the authors in a previous study. To this end, a finite element (FE) direct shear model for Federal Highway Administration (FHWA) shaped shear key (abbreviated as FHWA-SK) was developed and calibrated first. Then, the validated FE model was extended to investigate the OPT-SK's shear behavior with SRBs. To experimentally measure the ultimate load capacity of the OPT-SK, a push-off direct shear (P-ODS) test was carried out on the OPT-SK with SRBs in both pre-crack and post -crack status. The results showed that the OPT-SK with SRBs exhibited a higher carrying load capacity, a more evenly distributed stress, and a lower stress magnitude than the FHWA-SK with SRBs. The cracks or damage mainly initiated and developed in the high strength concrete (HSC) components and the interface between the UHPC and HSC components. The P-ODS test's load-displacements or strains were reported to highlight the SRBs' effectiveness and functionality in the OPT-SK.