On the finite element modelling of RC beams shear-strengthened with FRP

Abstract

Abstract:A significant number of studies have been conducted on the shear strengthening of reinforced concrete (RC) beams with externally bonded fibre reinforced polymer (FRP) reinforcement in the forms of strips, plates or sheets. However, most of these studies have been experimentally based and only a very limited amount of research is available on the numerical modelling of such beams using the finite element (FE) method. The lack of in-depth FE studies is chiefly due to the challenging nature of modelling shear cracking in RC beams and the interfaces between different materials. This paper presents the results of a recent study in which an advanced FE model was employed to investigate the effects of different modelling assumptions for the interfaces between concrete and steel stirrups, between concrete and steel tension bars, and between concrete and FRP on the predicted shear behaviour of RC beams shear-strengthened with FRP. It first outlines the FE model followed by a number of numerical examples to validate it. The effect of varying the bond-slip modelling approach for each interface is then investigated to illustrate its significance. The results presented in this paper show that proper modelling of the bond behaviour of all three types of interfaces is essential in order to accurately simulate the shear behaviour of RC beams shear-strengthened with FRP and that the effects of the assumed bond behaviour of steel stirrups or steel tension bars are very complex and need much further research.Key words: Reinforced concrete beams, shear, crack band model, FRP, strengthening, bond behaviour, bond modelling, debonding, finite element method. Research highlights:1) FE modelling of shear failure of FRP-strengthened RC beams is investigated. 2) Appropriate modelling of FRP-to-concrete bond behaviour is shown to be essential.3) The bond between steel tension bars and concrete has a significant effect. 4) The effect of bond between steel stirrups and concrete is very complex.

Behaviour of FRP-to-concrete interfaces between two adjacent cracks: A numerical investigation on the effect of bondline damage

“…This model is simple for implementation but captures the key unloading features experimentally observed as mentioned above, providing sufficient accuracy for the purpose of the present study. Similar models have also been adopted in several studies on the modelling of FRP-concrete interfaces [18,[31][32][33][34][35].…”

Modelling Static and Dynamic FRP-Concrete Bond Behaviour Using a Local Concrete Damage Model

“…where ∆σ y , ∆σ m and ∆σ r are functions of the mean pressure p = I 1 /3, in which I 1 is the first invariant of (Chen et al 2011(Chen et al , 2012Kim and Vecchio 2008;Lu et al 2004;Yang et al 2003;Teng et al 2002;Chen and Teng 2001). Because most debonding failures occur in the concrete adjacent to the FRP, rather than in the adhesive layer, or at the FRP-adhesive or adhesiveconcrete interfaces, the modelling of concrete damage and fracture is of crucial importance for any reasonable prediction of the bond behaviour.…”

Flexural and Shear strengthening of RC beams with NSM technique-manually made CFRP bars

“…The bond behavior of the concrete between both external FRP reinforcement and internal steel reinforcement may also play a signi cant role [22]. Chen proposed an advanced FE model for RC beams strengthened in shear with externally bonded FRP that takes into account an appropriate material model to de ne the post-cracking tensile behavior of concrete as well as the interfacial behavior of FRP and steel reinforcement [23]. Developing such advanced issues requires more e orts, and using simpli ed assumptions in FE analysis by commercial software is still popular [24][25][26][27].…”