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The debonding of carbon fibre-reinforced polymer (CFRP) strips from the surface of concrete is one of the main premature failure modes for concrete beams that are externally strengthened with CFRP strips. Many anchorage systems are developed to prevent or delay the debonding process in these beams in order to improve the ultimate load capacities. In this study, nonlinear finite-element analyses (FEAs) are performed by employing ABAQUS software to describe the load-deflection behaviour and ultimate loading capacities of concrete beams whose flexure has been strengthened using externally bonded CFRP strips with mechanical anchorages. First, the nonlinear finite-element model results are validated using the results of an experimental study previously carried out by the authors. In the experimental study, the variables investigated are the CFRP strip width and the number and the arrangement of the mechanical anchorages. A good agreement is demonstrated between the numerical and the experimental results. Then, a parametric study is conducted to investigate the effects of the mechanical anchorages on the ultimate load capacities of concrete beams. Consequently, the variable, the CFRP bonding length, is included into the finite-element models that are corrected with the experimental results, and equations involving many variables concerned with the ultimate loading capacities are suggested. Finally, an ultimate load capacity multiplier is proposed enabling the calculation of the ultimate load capacities of beams mechanically anchored with CFRP strips, with regard to the CFRP strip width, the bonding length, the number of mechanical anchorages and the arrangement of the variables.

Tomography images and image processing methods are extensively employed by researchers to investigate the microdimensional air voids that are formed in the internal structure of concrete. Finite element method-based fracture analysis is required to investigate the effect of the mechanical behavior of concrete and micro-dimensional crack development; microdimensional voids cannot be experimentally observed because of their small scale. Although concrete that is exposed to uniaxial compression remains in the elastic region, realistic brittle failure can be achieved using the damage plasticity model, which considers the effect of tension cracks that form around micro air voids, which in turn enhance cracking development and the compressive strength of concrete. Within the scope of this study, concrete cubes with a side dimension of 15 cm were prepared. Three groups of these cubes are composed; each group contains three specimens. The first group contains additivefree control specimens and the remaining two groups contain specimens that are mixed with two different ratios of airentraining admixtures. After the concrete specimens were created, 1 cm 3 core samples were prepared and scanned with micro computed tomography. These 2D and high-resolution images are modeled using the image processing software Simpleware and exported to the finite element method (FEM) based analysis software Abaqus. The volume, void ratio and mass properties of fresh and hardened concrete, which are experimentally obtained, are compared with the physical properties of 3D-modeled specimens. Based on the mass and volume analyses, these 3D models, which have micro-dimensional air voids that are assigned with the parametrized concrete damage plasticity (CDP) material properties were simulated, and a uniaxial compression tests and fracture analysis were performed. According to the analysis results, the relations between crack development and quantity and the distribution of entrained air were discussed.