Repair and Strengthening of R.C Flat Slab Connection with Edge Columns against Punching Shear

Aims: Study the repair and strengthening of the flat slab-edge column connections against punching shear.

Study Design: Parametric study is carried out by varying the repair and strengthening number of stirrups rows and the stirrups materials.

Methodology: This paper study the effect of using of Fiber Reinforced Polymers (FRP) systems to strengthen and repair the flat slab-edge column connections subjected to punching shear. These systems is an exterior stirrups manufactured from glass, carbon fibers and steel links. Test results of thirteen half-scale specimens reinforced concrete flat slab-edge column connections were prepared to be tested under vertical punching shear load. The experimental plan for this study included one specimen not strengthened nor repaired which used as control specimen. Six specimens strengthened by exterior stirrups manufactured from Carbon Fiber Reinforced Polymer (CFRP), Glass Fiber Reinforced Polymer (GFRP) and steel links, respectively, three specimens strengthened by one row and the another three strengthened by two rows. Six specimens repaired by exterior stirrups manufactured from (CFRP), (GFRP) and steel links, respectively, three specimens repaired by one row and the another three strengthened by two rows. Also, the experimental ultimate loads were compared to the calculated values according to ACI 440.

Results: The test results were the ultimate load, load-deflection relationships, punching shear resistance, relative ductility, flexural stiffness & punching shear angle.

Conclusion: The test results illustrated punching shear strength increasing and an increasing in flexural stiffness for the strengthened and the repaired specimens compared to the control one. In addition, the strengthened and the repaired tested specimens illustrated enhancement in relative ductility and increase in angle of punching shear. The calculated ultimate loads based on ACI 440 procedures were below the experimental ones by 32 to 66%.