Flexural Behavior and Continuity Assessment of Precast UHPC One-Way Slabs with Post-Cast Joints

This study isolates the flexural role of a 100 mm post-cast joint and a simple local crossing-bar detail in precast ultra-high-performance concrete (UHPC) one-way slabs. Twelve 1000 mm wide, 50 mm thick slabs were tested under four-point bending in six groups: monolithic, plain-jointed, and joints strengthened by nine short Φ12 crossing bars, each at two specimen lengths. Unlike reinforced bridge-deck joints and specialized steel-plate, dovetail, or lap-splice details, the tested slabs contained no longitudinal slab-body flexural reinforcement. This deliberate omission allowed the continuity loss caused by the joint and the recovery provided by the local bars to be evaluated separately. Because B1-1 developed a flexure–shear crack, B1-2 was used as the primary 1000 mm pure-flexure reference, and a mean-based sensitivity check was also performed. The plain joint reduced the peak moment by 84.3% and 76.7% relative to the corresponding monolithic references. Crossing bars increased the mean maximum recorded moment by about 360% and 157% relative to the plain joints, reaching 71.9% and 59.8% of monolithic resistance. Three-dimensional ABAQUS/Explicit models using a common UHPC damaged-plasticity law, cohesive interfaces, and connector-based bond-slip reproduced the resistance hierarchy. The resulting continuity indices quantify the tested details and provide a mechanism-based comparison rather than general code resistance factors.