Modified strip model for punching-shear strength of FRP-reinforced concrete edge–column slab connections

Abstract

The use of fiber-reinforced polymer (FRP) bars as internal reinforcement for concrete structures in aggressive environments has emerged as an innovative solution to eliminate corrosion problems. Glass FRP (GFRP) reinforcing bars have recently gained wide acceptance as a viable construction material for sustainable new constructions due to their costing less than other FRP types. This paper reports the test results for full-sized edge–column slab connections (ECS –connections) reinforced with sand coated GFRP bars. These connections were cast using normal-strength concrete (NSC) and high strength concrete (HSC). The effect of concrete strength (NSC and HSC) and moment-to-shear force ratio (M/V) (300 mm, 600 mm) on the performance of the tested connections were examined. In addition, a new mechanical model, called Modified Strip Model, is presented for punching-shear strength predictions of FRP reinforced concrete (RC) ECS –connections. The test results reveal that the use of HSC directly augmented the punching-shear strength and improved the load–deflection response of the tested connections, However, Increasing the M/V ratio produced significant shear stresses, thus decreasing the punching-shear strength for the NSC and HSC connections, respectively. The mechanical model presented herein takes into account all possible mechanisms of loads transfer in FRP-RC ECS-connections. Hence, a complete shear–moment (V-M) interaction diagram can be plotted to predict the punching strength of such connections. Moreover, the model revealed higher accuracy and narrower scatter for punching-shear strength predictions compared to other available equations in FRP design codes and guides. The EN 1992–1-1–05 punching-shear equation was also examined for FRP-RC ECS–connections and adapted to consider the tensile properties of the FRP bars instead of steel.