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The numerical simulations of the strengthened RC slabs with CFRPs using standard CDP material model of Abaqus code

In this research, the effect of the lateral and corner openings as well as the impact of using a kind of FRP sheets known as Carbon Fibre-Reinforced Polymer sheets (CFRPs) as a retrofitting approach on the RC two-way slabs' bearing capacity was investigated. To this end, at first, an enhanced finite-element (FE) model of an actual laboratory sample of a reinforced concrete slab with central opening was simulated using well-known Abaqus software and verified using available experimental results. For concrete behaviour simulation, concrete-damaged plasticity (CDP) material model of Abaqus standard code which can predict well the nonlinear behaviour of concrete from the initial steps of loading scenario up to the failure state was used and its parameters were identified for this particular application. For verifying the identification, two concrete beam test set-up were simulated and the obtained results were compared with the laboratory test results. The reason of implementing such a constitutive model is that when the concrete is retrofitted with CFRPs, its brittle fracture mode under bending actions transformed to a ductile–brittle fracture one. Therefore, a need for a model which can simulate the plastic deformations and ductile damages of concrete in compressive stress regions and brittle damages in tensile stress regions up to near failure state is generated. After that, two rectangular slabs with the lateral and corner openings were simulated and strengthened with some geometrical patterns of CFRPs. Obtained results indicated that CDP material model for concrete can perform well in the structural behaviour simulating of the slabs. Also, it has been distinguished that the CFRPs can recover the load-bearing capacity loss of such slabs due to mentioned openings considerably and even in some cases can improve it in comparison to the homogeneous slab (slab with no opening). It was revealed, moreover, that the effect of the lateral openings on reduction of load capacity of these slabs is greater than the central and corner openings. Furthermore, it was declared that the combined 45° and 90° arrangement of CFRPs can affect more efficiently in strengthening weakened slabs with openings than the other CFRPs arrangements.