Strengthening of RC beams defected in shear using external bonded ribs made of aluminum tube sandwich filled with strain hardening cementitious composites

Installing Aluminum Tubes (ATs) filled with Strain Hardening Cementitious Composite (SHCC) on the sides of Reinforced Concrete (RC) beams for shear strengthening has not been studied before. These tests combine the advantages of aluminum material as a new construction material with the superiority of SHCC for shear treatment of RC beams. Additionally, this study is interesting because it provides a thorough assessment of the special composite system's ability to strengthen RC beams—a capability that hasn't been thoroughly investigated in the literature. With a particular emphasis on comprehending how various aluminum tube rib configurations—such as their orientation, length, and number—can affect the efficacy of the strengthening strategy, this investigation aims to evaluate the improvements in shear capacity, failure modes, and deformation behaviors. Conducted under a one-point loading scheme, the research analyzed eight strengthened RC beams alongside a reference beam to determine the impact of AT rib number and configuration on beam behavior under shear stress. Key findings indicate that diagonal AT ribs, optimally aligned with shear forces, significantly enhance shear strength by 19 %-48 %. This configuration effectively controls and limits the spread of shear cracks, with extended rib lengths halting crack propagation at varying extents—up to two-thirds of the shear span. Notably, vertical ribs demonstrated progressive increases in shear strength as the number of ribs increased, with enhancements of 18 %, 35 %, and 52 % for one, two, and three ribs, respectively. Furthermore, SHCC as a filler material played a pivotal role in these enhancements, leading to a 27 % increase in peak load capacity and a 54 % rise in deflection, compared to those without. One, two, and three vertical ribs showed increases in the ductility by 46 %, 143 %, and 222 %, respectively, while diagonal ribs exhibited the most substantial improvements, with one and two ribs increasing ductility by 158 % and 215 %, respectively. • Externally bonded aluminum tube (AT) ribs was conducted to strengthen RC beams. • Strengthening clearly enhanced shear strength and ductility of the beams. • Vertical ribs increased the shear strength by 18–52 %.