Punching Shear Resistance of Flat Slabs Strengthened with Near Surface–Mounted CFRP Bars

Abstract

This paper presents the effectiveness of strengthening slab–column connections against punching shear failure with near surface–mounted (NSM) carbon fiber–reinforced polymer (CFRP) bars. The experimental program consists of preparing and testing eight samples, two control, and six strengthened samples. The main variables of the experiment are the strengthening layout and the cross-sectional area of CFRP bars. The results show that NSM strengthening increases the ultimate load by up to 44%. The strengthening delays the formation of the first crack in concrete, thus maintaining a linear behavior for load–displacement and load–strain curves for a higher level of load. The NSM strengthening increases the flexural stiffness by over 100% and maintains a strong bond with concrete throughout the loading. The flexural strength of the slab increases, which subsequently improves the punching shear capacity. The experimental results are compared with several design codes by modification and implementation of Chen and Li’s method. There is a good agreement between the calculated ultimate capacity of the strengthened samples and the obtained experimental results.