Investigation of transverse reinforcement for R.C flat slabs against punching shear and comparison with innovative strengthening technique using FRP ropes

This research seeks to examine punching shear reinforcements using various materials and techniques, then evaluate their effectiveness in order to increase the punching strength of flat -slab-column connections (FSCC). Additionally, a novel strengthening method utilizing FRP ropes was suggested and investigated. In this study, sixteen FSCC with cross sections of (1600 x 1600 x 150) mm and stub columns with a cross section of 200 x 200 mm and a total height of 700 mm extended outside both sides of the slab were constructed and tested. The transverse reinforcements "stirrups" have been varied in [material types -spacing - width-shapes]. The variables were: the materials used (steel, CFRPs "carbon fiber reinforced polymers", GFRPs "glass fiber reinforced polymers"), spacing between stirrups (30, 50, 70 mm), the width of stirrups (140, 280 mm, and variable width stirrups as a novel scheme), and Case condition (internal rein-forcement or external strengthening). The experimental results indicated a significant increase in punching shear resistance for the FSCC reinforced with stirrups by 25-85 % when compared to the control specimen. The results demonstrated the superiority of the CFRP as a strengthening material over any other materials, also, the novel scheme proposed in this study (variable width stirrups) gave the highest punching capacity compared to the identical case slabs. To validate the experimental results, a finite element analysis using ABAQUS/CAE6.14 was performed, and the results were very close to the experimental one. Moreover, theoretical equations have been verified on the experimental specimens. Finally, experimental, theoretical, and analytical results were compared. The novel scheme and CFRP stirrups were recommended to use for enhancing the punching shear resistance.