Sustainable shear strengthening of defected RC beams using aluminum boxes and high-performance concretes

In the quest for sustainable and resilient structures, the enhancement of reinforced concrete (RC) beams has emerged as a critical area of research. Traditional strategies of shear strengthening often involve materials and techniques that are neither environmentally friendly nor cost-effective. This investigation aimed to improve shear resistance of RC beams exhibiting pre-existing shear deficiencies, strengthened using aluminum boxes containing high-performance concretes (HPCs). The experimental program involved testing eleven RC beams under three-point bending, with different parameters such as number of boxes, type of filling concrete, and existence of reinforcement within the aluminum boxes. The outcomes revealed that employing aluminum boxes considerably augmented the shear resistance of such beams, preventing brittle shear collapse and enhancing load-bearing capacity, stiffness, ductility, and energy absorption. Among tested HPCs, ultra-high-performance concrete (UHPC) demonstrated superior resistance compared to other types, especially when combined with steel or glass fiber reinforced polymer bars. Utilizing UHPC led to a significant improvement in the beam performance: stiffness and ultimate load increased by up to 99 % and 28 %, respectively, while achieving a more desired flexural failure mode. Also, the study proposed a formula to predict the shear capacity of beams enhanced with the proposed technique. The effectiveness of this formula as a useful tool for design and analysis was confirmed by its strong agreement with the experimental and finite element results.