Punching Shear Response of RC Slab-Column Connections Strengthened with UHPFRC - Finite Element Investigation

Reinforced concrete (RC) flat slabs can be retrofitted with a top thin layer of ultra-high performance fiber reinforced concrete (UHPFRC) to enhance their structural performance and service life. UHPFRC can also protect the concrete slab from impact and percolation of chemicals that could otherwise cause deterioration and corrosion of reinforcement. This study examines the punching shear performance of RC flat slabs retrofitted by fully and partially covering with a thin layer of UHPFRC. 3D non-linear Finite Element Analysis (FEA) is used to determine the response of the composite slabs. Both the concrete and the UHPFRC are modelled using the concrete damage plasticity model in ABAQUS software. The maximum shear resistance, deformation and crack patterns of the slabs with different areas of the UHPFRC layer are examined. The UHPFRC layer significantly increases the punching shear capacity and delays the crack propagation in all analyzed slabs. Incorporating a 40 mm UHPFRC layer on a 120 mm thick RC slab-column connection results in a 39% increase in ultimate punching load capacity. The partial cover of UHPFRC is a good suggestion since it results in a more economical solution and to a more ductile connection.