Flexural strengthening of RC beams using aluminum alloy plates with mechanically-fastened anchorage systems: An experimental investigation

Externally bonded reinforcement (EBR) has emerged as one of the promising techniques for flexural strengthening of reinforced concrete (RC) members due to its practicality and structural effectiveness. However, shortcomings like premature failure modes, cost, labor, and installation time limited its use. Mechanically fastened (MF) Aluminum Alloy (AA) plates instead have the potential to overcome some of these drawbacks by providing strength and ductility, while influencing the failure modes. In this investigation, 16 RC beams were prepared, one beam was left un-strengthened (CB), one was strengthened with an externally bonded (EB) AA plate (CBE), and the remaining 14 beams were strengthened with MF AA plates that varied based on expansion anchor bolts (EAB) sizes, spacing, layout, and the presence or absence of epoxy. The test results indicated that all the specimens with MF AA plates exhibited approximately 30% increase in strength accompanied with drastic increase in ductility up to about 84% compared to specimen CBE. Analytical predictions were made to numerically assess the advantages of using MF systems where ACI 318-19 outperformed ACI 440.2R-17 due to the sufficient composite behavior that allows the AA plates to behave similar to steel reinforcement such that the section has an additional lever arm. It is concluded that the implementation of epoxy and EAB as an alternative anchorage technique serves as a viable approach in enhancing the strength and ductility of RC beams strengthened with AA plates.