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

4.5. Numerical results and experimental validationcantly affected by both fiber diameter which varies from d f = 0.8 to 2.0mm, and theembedded lengths, varying from l emb = 22.1 to 35.0mm. The proposed procedure isable to realistically capture the influences of both parameters.MPa3.02.52.01.51.035 648Pi N71400.591100.00 5 10 15 20120 7100 680 5 460 3 840 220 19 1000.0 0.1 0.2 0.3 0.4 0.5 0.6 0.7zmm(b)si mm(a)1.2strain 1.E31.0760.8540.60.43820.2 91100.00 5 10 15 20zmm(c)Figure 4.14: Pull-out simulation for a steel fiber diameter of 0.8mm and an embedded lengthof 22.1mm by Banholzer et al. [2006]: (a) load-slip curve P i − s i , (b) interface shear stressdistributions τ − z and (c) axial strain distributions ε s − z.Only the numerical results based on the fracture energy modeling are outlined and compared against the experimental evidence in this section. The bilinear bond-sliprelationship posses, as demonstrated in subsection 4.5.1, a limited prediction capabilityfor pull-out tests, compared to the fracture energy-based proposal. For this reason thebilinear bond-slip behavior is neglected in this section.Finally, the discussion focuses on the detailed simulation of the complete debondingprocesses developing in the three cases whose overall response is described in Figure4.11 to 4.13. To this end, fiber-to-concrete bond stresses and fiber strain distributionsthroughout the bond length are obtained by means of numerical simulations. Figure 4.14 to 4.16 show such results for different bond lengths and diameters. In particular,Figures 4.14b, 4.15b and 4.16b report the distribution of interface shear stresses89