tesi A. Caggiano.pdf - EleA@UniSA - Università degli Studi di Salerno

5.1. Numerical analysesσ MPa12108642ρ f 4.0full debonding strengthρ f 3.0ρ f 4.0ρ f 3.050 debonding strength00.0 0.1 0.2 0.3 0.4 0.5 0.6σ MPa1210full fractureenergy8650 fractureenergyPlainu mmu mm(a)(b)42ρ f 4.0ρ f 3.000.0 0.1 0.2 0.3 0.4 0.5 0.6Figure 5.12: Comparison between numerical predictions of the test by Li and Li [2001] onSFRC with “Dramix type II” fibers: (a) full debonding vs. 50% of the debonding strength and (b)full fracture energy, G I f , vs. 50% of G I f .Fracture energy releaseFigure 5.12b reports the stress-crack opening behavior observed in the same experimenton SFRC, but corresponding to the case of 50% of the concrete fracture energyrelease in mode I. As can be observed in Figure 5.12, the interface model is able to capturethe influence of fundamental properties of the constituents in the overall responsebehavior.Dowel strengthFinally, the stress history on concrete blocks by Hassanzadeh [1990] is evaluated as itactivates failure processes under both mode I and II types of fracture. These experimentaltests, already simulated in subsection 5.1.2, are performed on prismatic concretenotched specimens in which both normal and transverse relative displacements areco-imposed on the upper border of the notched specimen while the remaining bordersare fixed with the aim of reproducing cracking processes in concrete under mode I andII types of fracture. During the first part of these tests only normal tensile displacementsu are applied until the peak strength is reached. Then, tensile displacements arecombined with transverse ones v defining a prefixed load angle (tanθ = u/v).Figure 5.13a shows the model predictions in terms of σ − u and τ − v curves, analyzingthe case in which θ = π/6 on both plain and SFRC concrete panels. The proposed applicationconsider the model parameters previously calibrated and reported in subsection5.1.2. Numerical analyses demonstrate the very good agreement of the numerical103