Numerical Modelling and experimental investigation on enhancing punching shear capacity using carbon fiber reinforced polymer on flat slabs

Abstract

Flat slabs are much vulnerable to shear failures because stress transferring between the column and the slab happens within a considerable small region. This creates high stress at the slab-column connection area result in punching shear failure. Shear failures are a little different from other failure modes such as flexural failure and excessive deflections because it shows a sudden nature while failing the member. Therefore, giving adequate shear capacity for the flat slabs is crucial. Carbon Fiber Reinforced Polymers (CFRP) is a new material which can be used for structural strengthening. Use of CFRP is promoted by its competitive advantages such as high strength and stiffness to weight ratio, corrosion resistance, low thermal expansion, non-magnetic properties, good fatigue properties and ease of handling. The sudden punching shear failure tendency of flat slabs is a critical issue. Installation of CFRP flexural reinforcements and post installed CFRP shear reinforcements to enhance punching shear capacity are successful approaches. In this study, medium scale flat slab panels were prepared and strengthened with CFRP. Effects of seven alternative bonding arrangements of CFRP were studied. More than 120% punching shear gain was noted from the specimens strengthened with the combination of CFRP flexural and shear reinforcements. Further, the effects from end anchorage of external CFRP and the refilling material at drilled locations to install CFRP shear strengthening scheme were investigated in terms of the enhancement on punching shear performance. A numerical investigation was also conducted to analyze bond behavior and stress behavior. The model predicted performances are in good agreement with the test results. A parametric study was also performed. The use of double-layered CFRP as external reinforcement was found to be the most effective multi-layered system. Further, the identification of the critical locations for the application of the external CFRP strengthening scheme was determined and the practical importance of providing end anchorage was quantified.