Finite element modelling of RC slabs strengthened against punching shear with L-CFRP laminates

ABSTRACT Punching shear strengthening of existing reinforced concrete (RC) flat slabs can be required due to increased loads or design/construction defect. One of the more effective punching shear strengthening solutions, which has shown promising results is the use of post-installed L-shaped carbon fibre-reinforced polymer (L-CFRP) laminates bonded into predrilled holes through the slab in specific shear perimeter arrangements around the column. This paper presents an extensive finite element analysis (FEA) into RC slabs strengthened in punching shear using L-CFRP laminates. FEA models were developed using an existing experimental study as the baseline. After successful model calibration, parametric studies were used to explore the influence of critical parameters such as the concrete strength (32, 40 and 60 MPa) and the number of shear perimeters on the resulting punching shear capacity. In total, four RC slabs were modelled including an unstrengthened control specimen and an additional three specimens with different strengthening arrangements. A bond-slip model was introduced between the CFRP and the concrete and its calibration was described in this paper. Simulation results are compared with the experimental results in terms of load–deflection behaviour, FRP strains and crack patterns. The predicted peak loads calculated from the design codes and critical shear crack theory (CSCT) are compared and discussed in conjunction with the experimental and FEA results. The failure mode for the slabs were also compared with design codes and CSCT theory predictions. The study demonstrated the FEA results to have a good agreement with the experimental results in terms of load deflection behaviour, failure mode and L-CFRP strains.