Experimental and analytical investigation on continuous two-span RC beams flexural strengthened with aluminum alloy bars

Reinforced concrete continuous beams can develop inadequate load-bearing capacity as a result of altered usage demands or updated code requirements. The newly developed 7xxx series aluminum alloy (AA), which exhibits high strength-to-weight ratio, good ductility, and excellent corrosion resistance and thermostability, is a relatively new material for structural application. Applying near-surface mounted (NSM) aluminum alloy (AA) bars offers an effective strengthening approach, particularly suitable for corrosive environments. To investigate the flexural behavior of continuous two-span reinforced concrete beams strengthened with NSM AA bars, this study conducts tests on eight continuous beams reinforced with NSM AA bars in both hogging and sagging regions, as well as one control beam. The main test parameters were NSM reinforcement ratio, bond length, strengthening position, and end anchoring of U-CFRP. The test results were analyzed and discussed in terms of the load-deflection curves, failure modes, reinforcement strains, and moment redistribution. Results shows that all strengthened beams displayed a significant enhancement in load-bearing capacity ranging over the control beam. Extending NSM AA system over the theoretical inflection point could delay the final failure, CFRP U-jacket end anchorage could improve the overall capacity and changed the failure mode of the strengthened beams. In addition, analytical models considering mechanism of different failure modes were developed to predict the load-bearing capacities of the beams, good agreement between experimental and theoretical results was achieved. • NSM AA bars increase the bearing capacity but reduce the moment redistribution of continuous beams. • Extending NSM AA system over the inflection point could delay the final failure. • CFRP U-jacket end anchorage improves the overall capacity and changes the failure mode. • Analytical models considering different failure modes are proposed for the prediction of load-bearing capacities.