Shear strengthening of reinforced concrete beams with externally bonded FRP composites: finite element modeling and parametric study

Abstract

Shear failure in reinforced concrete (RC) beams has always been a major concern for engineers to deal with, particularly in deep beams such as RC girders. Nevertheless, with the use of fiberreinforced polymer (FRP) composites, this type of failure can be avoided. Using externally bonded (EB) FRP composites for shear strengthening of RC beams requires sufficient knowledge and experience given the premature bond failure, the complex behavior of interface layer between FRP composites and the concrete substrate, as well as fracture mechanics of non-homogeneous concrete. Many experimental conducts have been carried out to evaluate the shear contributions EB-FRP in shear strengthening even though laboratory tests are timeconsuming and expensive. However, by developing numerical models and obtaining highprecision results validated by experimental testing, finite element analysis softwares have become a valid alternative to experimental testing. On the other hand, the analytical models proposed in existing design guidelines are not consistent with the results obtained from experimental tests, as many parameters are not taken into account in these models. For example, the inverse interaction between EB-FRP and steel stirrups, the size effect, shear bond stresses at the interface between concrete and EB-FRP and between steel stirrups and concrete, shear crack angles varying with internal and external shear reinforcements, and the distribution of shear cracks leading to premature debonding. The aim of this research is to have an in-depth insight into the maximum load transferred through interface layer and consequently, the ultimate load carried by RC beams strengthened in shear with EB-FRP composites through analytical and finite element (FE) approaches. The results obtained from the aforementioned methods will be validated with previous experimental data. Finally, new mathematical relationships will be proposed considering all the parameters contributing to the shear strengthening of RC beams with EB-FRP and the behavior of the interface layer. For this reason, in the first phase of this research, the literaturereview is carried out on the previous numerical research to evaluate their deficiencies and merits in simulating the aforementioned beams. This will give us a better understanding of the assumptions implemented in these research studies, as well as the type of analysis (static or dynamic). A numerical simulation is carried out in the second phase of this study to incorporate the parameters with essential influences on shear contributions of EB-FRP to the ultimate shear strength of RC beams strengthened using EB-FRP. These parameters include the size effect and the inverse interaction between EB-FRP and steel stirrups. All the results obtained from the numerical tests are validated through the experimental conducts. Parametric studies are then carried out to obtain the appropriate effective strains closer to those obtained from laboratory tests than from analytical results. To obtain the appropriate effective strains, parametric results are evaluated by regression of previous experimental tests. Analytical models for the effective strains are then proposed to bridge the gap between the existing models in the design guidelines, taking into account the distribution of shear cracks and the distribution of stresses on the fibers intercepted by the main shear crack.

Date	25 Jan 2024
Original language	American English
Awarding Institution	École de technologie supérieure
Supervisor	Omar Chaallal (Supervisor) & Georges El-Saikaly (Co-supervisor)