Experimental Study of Punching Shear on Reinforced Concrete Waffle Slabs Strengthened by CFRP Sheets

Abstract

For the last five decades, researchers have been studying the punching shear of two-way reinforced slabs at column supports in structural testing laboratories. Limited tests are available on retrofitted waffle slab punching behavior. These are necessary since they establish a baseline against which punching shear design provisions can be created, calibrated, and evaluated. This work presents an experimental approach to investigate the punching shear of reinforced concrete waffle slabs strengthened with carbon fiber reinforced polymers (CFRP) sheets. Retrofitted waffle slabs were tested under concentric monotonic loading. A series of tests on construction materials were also conducted. The testing program was divided into two categories (IWS1 and IWS2), with a total of ten specimens: solid sections (275 × 275) and (515 × 515) mm, respectively. The IWS1 category consisted of eight slabs; one slab was without strengthening as a reference slab, and the remaining slabs were strengthened. While IWS2 consisted of only two slabs. However, the waffle slabs’ observed punching failure mechanism was like flat slabs. All waffle slabs were punctured in a sudden position. Research showed that the CFRP retrofitting process enhanced the ultimate punching shear performance by 47.1% and the initial cracking load by 67.02%, respectively. When the solid size regions were increased, the ultimate punching load increased by 41.5 %, and the initial cracking load increased by 40.8%, respectively. Significant enhancements were documented in the proposed retrofitting mechanism.

Keywords

• Waffle slab
• CFRP Sheets
• Reinforced concrete
• Punching shear
• Retrofitting