Experimental and Numerical Study of RC Beams Strengthened in Flexure with Bolted/Bonded AA Plates

Abstract

Reinforced Concrete (RC) members are susceptible to deterioration due to many factors. Externally bonded reinforcement (EBR) such as fiber-reinforced polymers (FRP), had emerged as one of the proven techniques for flexural strengthening and retrofitting of RC members. This is due to its practicality and structural effectiveness; however there are shortcomings that include premature de-bonding/de-lamination failure or brittle FRP rupture failures. The use of mechanically anchored Aluminum Alloy (AA) plates instead has the potential of overcoming these drawbacks by providing both strength and ductility while influencing the failure modes. In this project, 16 RC beams were prepared, one beam was left unstrengthened (CB), one was strengthened with AA plate using epoxy only (CBE), and 14 beams were strengthened with AA plates with different bolt sizes, spacing, bolt layout and epoxy. The specimens were tested to failure and all specimens with bolted AA plates exhibited approximately 30% increase in strength accompanied with drastic increase in ultimate ductility (56.5%) and failure ductility (84.1%) compared to the control beam with epoxy (CBE). It is concluded that the implementation of a hybrid anchorage system (i.e., bolts with epoxy) in retrofitting applications serves as a viable option for fixing AA plates to RC beams. Furthermore, nonlinear finite element (FE) models for all specimens were developed using validated constitutive laws for capturing the nonlinear properties of the materials. Contour plots and concrete cracking patterns were generated to monitor the stress and cracking propagation for each model. The FE predictions closely resemble that of the experimental results in terms of load-deflection, cracks patterns and failure modes. This validated the use of FE as a simulation tool for further investigating the behavior of RC beams strengthened with externally bonded and bolted AA plates.