Ahmed Hamoda, Mizan Ahmed, Aref A. Abadel, Ahmad Saad
Although the flat slab–column connection is widely used in reinforced concrete (RC) structures due to its simplicity, its high sensitivity to punching-shear cracking—leading to reduced effective thickness and potentially sudden collapse—remains a critical issue. Moreover, enhancing this performance requires sustainable and advanced materials that can be applied without enlarging its cross-section or partial reconstruction. Addressing such challenges, the present study experimentally, analytically and numerically investigates the efficacy of next-generation flowable high-performance concretes (HPCs), specifically engineered cementitious composite (ECC) and rubberized ECC (RECC) both reinforced with aluminum bars. Both ECC and RECC were introduced as implanted ribs at the compression side of the punching zone with different configurations and connected to the slab using deformable 3-mm aluminum bars. The ECC was proposed to utilize its superior strain-hardening behavior, while the RECC was intended to contribute to energy absorption provided by recycled rubber particles. C-shaped aluminum bar with 90° bent ends (CAB) served as simple, deformable, corrosion-resistant connectors across the NC–ECC/RECC interfaces, acting as shear connectors and resisting internal punching-shear cracks. The investigated variables were: HPC type (ECC/RECC), implanted-rib configuration (one-way/two-way), and aluminum-bars ratio (0.29%/0.59%). Six strengthened slabs and one baseline were experimented. The experimental findings revealed that these parameters significantly affected structural performance by controlling the failure mode, improving cracking performance, enhancing absorbed energy and stiffness. Results outlined that the ultimate capacity increased by 1.40–1.57 times, and energy absorption rose by 6–7 times. A Concrete Damaged Plasticity–based finite element model (FEM) was developed and validated with over 93% accuracy. A new equation has been proposed for predicting the punching capacity. The validated FEMs were then employed for equation calibration besides executing two parametric studies to evaluate the contribution of CAB system and implanted ribs.