Numerical investigation on the behavior of reinforced concrete slabs strengthened with carbon fiber textile reinforcement under impact loads

Abstract

In this study, impact load performance of reinforced concrete members strengthened with carbon fiber textile reinforcement (CFTR) was investigated through numerical simulations. In the first phase of the study, a finite element model was set up to model reinforced concrete slabs of 1500 × 1500 × 200 mm in dimensions, strengthened with CFTR and subjected to multiple impact loads, using software LS-DYNA. This model was validated against experimental data available in the literature and basic modeling parameters, such as material model selection, mesh size, and erosion parameters for better accuracy were determined. In the second phase of the study, a numerical parametric study was conducted using the validated model to reveal the effects of steel and textile reinforcement ratio, slab thickness, striker mass, size, and velocity on the behavior of steel-reinforced concrete slabs strengthened using CFTR. As a result of the study, it was found that CFTR was effective in limiting the peak and residual displacements in reinforced concrete slabs subjected to multiple impacts at the middle. Among 220 mm thick specimens, for the same steel reinforcement ratio, a higher CFTR ratio resulted in lower peak and residual displacement levels after the third impact. On the other hand, when 8 mm diameter steel reinforcement was varied from 100 mm to 200 mm spacing, it was found that steel reinforcement ratio was the dominant factor on the impact behavior over the CFTR ratio. CFTR strengthening was particularly more effective when the members displayed a global response instead of a local one, such as low-velocity high-mass impact loading or in the cases where the striker had a larger diameter. Similarly, thickness was also found to be a major factor on the effectiveness of CFTR. When thickness of the slab was varied from 50 mm to 300 mm, CFTR's effect was found to be more pronounced for thinner slabs in preventing perforation and limiting peak and residual displacements. However, for 200 and 300 mm thick slabs, CFTR did not have a significant effect since local punching behavior was dominant in these slabs and CFTR was not effective in this shear mechanism.