Punching shear behavior of Slab–Column joints with partial UHPC enhancement: Experimental, numerical, and data-driven predictions

Reinforced concrete (RC) slab–column joints are prone to brittle punching shear failure. Enhancing their punching shear capacity is therefore critical for improving structural safety of flat slab structures. Ultra-high performance concrete (UHPC), characterized by high strength and ductility, provides a promising approach to enhancing the punching shear performance of slab–column joints. This study evaluates the effectiveness of partial UHPC application in enhancing punching shear performance. Four specimens with varying UHPC areas were tested to assess load–displacement behavior and failure modes. To extend the investigation, 216 validated finite element (FE) models were developed to examine the effects of UHPC area, material strengths, reinforcement ratio, and slab depth. A comprehensive dataset combining simulation and test results was used to train machine learning (ML) models. Among four algorithms, XGBoost achieved the best performance (RMSE = 21.87, R 2 = 0.98). SHAP and partial dependence plot analyses revealed UHPC area as the most influential factor, followed by UHPC strength and slab depth. In contrast, reinforcement ratio and column size showed limited influence, diverging from trends observed in conventional RC slab-column joints. These findings highlight the structural benefits of partial UHPC enhancement and offer new insight into optimizing slab–column joint design.