Flexural mechanism and design method of concrete composite slabs with joint

Abstract Composite slabs, which consist of a precast concrete bottom panel and a cast‐ in situ concrete topping, are widely used in modern precast concrete buildings. The conventional precast concrete bottom panels are more prone to damage during transportation and hoisting, which can seriously hinder construction efficiency due to extended lap‐splice rebars. This study introduces a new splicing slab design featuring L‐shaped grooves and lap‐splice rebars to improve construction efficiency. Full‐scale experimental testing was conducted to analyze load–deflection responses, crack patterns, failure modes, and strain distributions. A numerical model was developed to reproduce the testing, while a simplified theoretical model was used for design prediction. The results show that the new splicing slab exhibits ductile failure without interface cracks, demonstrating a three‐stage load–deflection response and effective force transmission through lap‐splice rebars. Finally, the design method of joints is proposed, laying a groundwork for the optimal design of precast concrete slabs with joints.