Title: Influence of the positioning of CFRP laminates for improving punching shear capacity of column-to-slab connections
Author(s): Hikmatullah Akhundzada, Ted Donchev, Diana Petkova and Abdul Mahbob Samsoor
Publication: Symposium Paper
Appears on pages(s): 18.1-18.8
Keywords: Punching shear failure, RC flat slabs, column to slab connection, CFRP laminates, externally bonded, positioning
Structural retrofitting of flat slabs is often required mainly due to corrosion of reinforcement, change of use and design errors. Punching shear failure is a common type of failure in flat slabs in the area of connection with the column, which could lead to progressive collapse. The slab-column connection is critical as it exposes to bending moments and significant shear stresses in RC flat slabs. Utilization of FRP attachment as strengthening method for concrete structures is becoming the most popular approach for improving their characteristics. CFRP laminates are already well established structural strengthening material and the further optimisation of their application in case of punching shear strengthening will allow for developing of effective solution for this problem. The research comprises testing of seven small scale reinforced concrete slabs (550x550x75 mm) (21.7x21.7x3 inch) with a column stud (80x80x75 mm) (3.1x3.1x3 inch) at the centre to simulate the slab-column connection. One control sample and six CFRP strengthened samples were prepared and tested against punching shear failure. The primary variable of the experiment was the positioning, layout and configuration of the CFRP laminates. The total width and thickness of the CFRP laminates were kept constant and the objective was to determine the most efficient layout. It was found out that using CFRP laminates as externally bonded reinforcement significantly enhances the punching shear capacity and results in improved stiffness of the slabs. The result shows a significant increase in ultimate load and stiffness.