Flexural Behavior and Design Method of Deep-Notched Precast Concrete Slab Connections for Modular Construction

This study proposes a deep-notched precast concrete slab system with post-cast connections for modular construction, aiming to improve on-site assembly efficiency while maintaining flexural continuity. A total of 22 full-scale slab specimens, including monolithic cast-in-place slabs and precast slabs with different notch depths, anchorage lengths, reinforcement diameters, and notch geometries, were tested under positive and negative bending conditions. The experimental results showed that, for the investigated reinforcement layout and loading conditions, the connected slabs with adequate anchorage achieved approximately 85% and 95% of the flexural capacity of the corresponding cast-in-place slabs under positive and negative bending, respectively. Anchorage length was found to be a key factor governing failure mode and load-transfer efficiency, while reinforcement diameter had a significant influence on ultimate capacity. Within the tested range, notch depth and notch geometry showed comparatively limited effects on flexural capacity, although their influence should be interpreted in relation to the adopted reinforcement arrangement and anchorage conditions. Finite element models based on the concrete damage plasticity approach were developed to interpret the load-transfer mechanism and parameter sensitivity. The models predicted the ultimate load with acceptable accuracy, while larger discrepancies were observed in some displacement estimates because of the simplification of interface behavior, bond-slip response, and local cracking. The experimental and numerical results indicate that load transfer across the joint was mainly achieved through reinforcement bridging, whereas the contribution of concrete bonding at the joint was limited under the investigated conditions. Based on these findings, a modified analytical model was proposed to predict the ultimate flexural capacity of the connected slabs. The model showed reasonable agreement with the test results for specimens with adequate anchorage. The proposed connection provides a feasible detailing solution for precast concrete slab connections in modular construction, but its application should be limited to configurations with comparable reinforcement layout, anchorage conditions, material properties, and monotonic bending behavior.