PSI - Issue 68

Aseel Salameh et al. / Procedia Structural Integrity 68 (2025) 166–172 A. Salameh et al. / Structural Integrity Procedia 00 (2025) 000–000

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3.1. Material properties and element types Concrete and CFRP material properties incorporated in the model are the same as those mentioned in the experimental testing. To model concrete, SOLID65 element is used. This element is an 8-noded 3-D element able to simulate cracking and crushing, thus capturing the nonlinear behavior of concrete. Hognestad et al. (1955) model was used to simulate the behavior of concrete in compression, while its behavior in tension is modelled using a bilinear relationship where the maximum concrete tensile strength and cracking strain are specified, followed by a linear softening behavior. CFRP sheet and epoxy were modelled using SOLID185 element, which is an 8-noded 3-D linear element. The orthotropic material properties of CFRP are assigned to the model. Since CFRP possess a linear elastic behavior until rupture, only the elastic modulus, shear modulus and Poisson’s ratio are assigned in each direction (X, Y, and Z, respectively). Steel supports are also modelled using SOLID185 element. 3.2. Geometrical configuration A quarter of the concrete prism shown in Fig. 4 is modelled to make use of the symmetrical conditions and save computational time. The 3-D model components along with the mesh configuration are shown in Fig. 4a. Restraints are applied in the direction of symmetry, as presented in Fig. 4b.

Steel plate

Concrete

Epoxy & CFRP

(a) (b) Fig. 4. Details of the FE model: (a) model components; (b) symmetrical conditions.

3.3. Modeling interface between concrete and CFRP The interface behavior between the CFRP laminate and the concrete substrate was simulated using cohesion elements (INTER205) and the cohesive zone material model (ANSYS, 2019). Debonding in the FE model occurs when the stress in the FRP reaches the ultimate shear stress specified in the model. The experimental bond-slip model calculated in Section 2.2 is incorporated in the FE model. To use the cohesive zone material model, three values are needed: the maximum shear stress, its corresponding slip, and the maximum slip. 3.4. FE model results After performing nonlinear mechanical analysis in ANSYS, the FE model results were validated with the experimental results in terms of ultimate load and failure modes. The failure of the concrete prism in the FE model was debonding of the CFRP laminate as shown in Fig. 5, similar to the failure in the experimental results. Moreover,