Abstract
Tension stiffening is a characteristic behavior of reinforced concrete (RC) beams which is directly affected by the bond-slip property of steel bar and concrete interfaces. A beam strengthened with a near-surface mounted (NSM) technique would be even more affected by tension stiffening, as the NSM reinforcement also possess a bond-slip property. Yet assessing how much the tension stiffening of NSM contributes to the behavior of RC beams is difficult due to the fact that bond-slip effects cannot be directly incorporated into a strain-based moment-curvature analysis. As such, the tension stiffening is typically incorporated through various empirical formulations, which can require a great deal of testing and calibrations to be done. In this paper a relatively new method, which can be called the mechanics-based segmental approach, is used to directly simulate the tension stiffening effect of NSM reinforcements on RC beams, without the need for empirical formulations to indirectly simulate the tension stiffening. Analysis shows that the tension stiffening of NSM fiber reinforced polymer (FRP) contributes a significant portion to the stiffness and strength of the strengthened RC beam not only during serviceability, but at all load levels.
Highlights
In recent years, the focus of research on strengthening of reinforced concrete (RC) beams using fiber reinforced polymers (FRP) has changed slightly from externally bonded (EB) techniques [1,2,3] to near-surface mounted (NSM) technique [4,5,6]
The partial interaction theory has been used by several researchers to perform a numerical analysis using bond-slip properties [16,17,18,19], which removes the need for empirically derived formulations for simulating the tension stiffening effect
The strengthened beams were found to show higher stiffness compared to the control beam due to the carbon fiber reinforced polymer (CFRP) bars in this phase
Summary
The focus of research on strengthening of reinforced concrete (RC) beams using fiber reinforced polymers (FRP) has changed slightly from externally bonded (EB) techniques [1,2,3] to near-surface mounted (NSM) technique [4,5,6]. It should be noted that while no portion of the mechanics is based on empiricisms, empiricisms are still required in terms of material properties, such as stress-strain relationships and bond-slip relationships In this paper, it will be shown how the segmental moment-rotation approach can be used to simulate the behavior of NSM FRP reinforcements. It will be shown how the segmental moment-rotation approach can be used to simulate the behavior of NSM FRP reinforcements This is done by applying the partial interaction theory to create a numerical analysis that is used to simulate the tension stiffening load-slip relationship between. The contribution of tension stiffening of NSM FRP reinforcements on the behavior of RC beams at all levels of load up to failure is verified using a comparison study
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