Abstract-This study aims to determine the efficiency of using Fiber Reinforced Polymers (FRP) systems to strengthen the slab-column connections subjected to punching shear. The used strengthening systems consisted of external FRP stirrups made from glass and carbon fibers. The stirrups were installed around the column. Also, external steel links were used as a conventional strengthening method for comparison. Over the last few years, the use of FRP for strengthening of concrete structures has been investigated by many researchers, whichconcerning with the strengthening of reinforced concrete slabs, beams and columns. The use of FRP in strengthening concrete slabs in flexure is done by bonding it to the tension face of the slabs. The use of FRP for strengthening the flat slabs against punching shear can be considered as a new application. This research shows the results obtained from an experimental investigation of 4 half-scale two-way slab-column interior connections, which were constructed and tested under punching shear caused by centric vertical load. The research included one unstrengthened specimen, which considered as control specimen, one specimen strengthened with steel links, one specimen strengthened with external stirrups made from Glass Fiber Reinforced Polymer (GFRP), and one specimen strengthened with external stirrups made from Carbon Fiber Reinforced Polymer (CFRP). So, the type of strengthening material is the basic parameter in this study. The experimental results showed a noticeable increase in punching shear resistance and flexural stiffness for the strengthened specimens compared to control specimen. Also, the strengthened tested slabs showed a relative ductility enhancement.Finally, equations for punching shear strength prediction of slab-column connections strengthened using different materials (Steel, GFRP & CFRP) were applied and compared with the experimental results.Index Terms-Fiber reinforced polymer, punching shear, reinforced concrete slab-column connection, Strengthening and repair.

This paper presents experimental data and results on the effect of externally bonded fiberreinforced polymer (FRP) with studs from FRB on the punching shear behavior of interior slab-column connections. A total of sixteen square slabs with a concentric column were constructed and tested. One specimen act as a control, and the others specimens strengthened with three different strengthening techniques. The first technique consists of 6 slabs strengthened with external FRB strips with different configuration (skewed or orthogonal) and different location from column face (offset or adjacent) and the second technique consist of 4 slab strengthened with external FRB strips with studs from FRP located on both side of the strips with spacing 100 mm and cross at intersection of strips which act as shear reinforcement and wrapping FRP strips to delayed debonding of FRP and improve the structure behavior of strengthened connection. The third technique consists of 5 slabs strengthened with external FRB and steel plates with different size 350 x 350 mm and 450 x 450 mm at the center of the slab. The test variables were the location of FRP strips (adjacent or offset column face), the number of strips layer and the orientation angle of the strips (Orthogonal and Skewed), and the type of materials (GFRP, CFRP, Steel). Size of plate 350 x 350 mm or 450 x 450 mm and method of strengthening. The test results clearly showed that FRP with studs strengthening leads to significant improvements in the structural behavior of slabcolumn connections. The increase in punching capacity of strengthened slabs was up to 48%, while the increase in stiffness was up to 92% compared to the control slab.