PSI - Issue 39

Umberto De Maio et al. / Procedia Structural Integrity 39 (2022) 677–687 Author name / Structural Integrity Procedia 00 (2019) 000–000

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In addition, Figure 5b shows the deformed configurations obtained by the proposed model. The numerically predicted main crack path is globally consistent with the reference one, considering self-similar crack propagation. 3.2. Debonding analysis of an FRP-plate RC beam The proposed fracture model, described in Section 2 and validated in Section 3.1, has been here used to investigate the debonding mechanisms in the FRP-strengthened RC elements, involving the four-point bending test analyzed in Gao et al. (2004). The geometry and boundary conditions of the tested beam are depicted in Figure 6, whilst the mechanical properties of the material constituents are reported in Table 2.

Fig. 6. Geometric configuration and boundary conditions of the simulated four-point bending test.

Table 2. Elastic and strength parameters of the material constituents.

Young’s modulus [GPa]

Poisson’s ratio

Yield strength [MPa]

Tensile strength [MPa]

Compressive strength [MPa]

Materials

Concrete

31

0.2 0.3

-

2.1

35.7

Steel

200 235

460

- - -

- - -

CFRP plate Epoxy resin

0.35 0.35

- -

1

The adopted strengthened system consists of a carbon FRP (CFRP) plate with thickness of 0.22 mm, bonded on the tension face of the beam by using a 2 mm thick adhesive. Given the symmetry of geometry and boundary conditions, only a half beam is modeled, in order to reduce the numerical efforts. The beam under consideration is discretized by using a Delaunay tessellation made of three-node triangular elements with maximum size of 10 mm (and average size of about 7.26 mm) for the bulk phase and zero-thickness four-node elements for the interfaces. The cohesive interface elements are inserted only in the region dominated by the shear-bending stress state, and along the material interface between concrete and adhesive, as reported in Figure 7.

Fig. 7. Computational discretization adopted for the numerical analysis.

Table 3. Material parameters for the traction-separation law used in the four-point bending test. nc t [MPa] sc t [MPa] Ic G [N/m] IIc G [N/m] 0 n K [N/mm 3 ] 0 s K [N/mm 3 ]