Punching capacity is one of the main items in the design of both pre-stressed and non-pre-stressed flat slabs. All international design codes include provisions to prevent this type of failure. Unfortunately, there is no code provision for UHPC yet, and hence, the aim of this research is to experimentally investigate the impact of column dimensions and punching reinforcement on the punching capacity of post-tensioned slabs and compare the results with the international design codes’ provisions to evaluate its validity. The test program included five slabs with a compressive strength of 120 MPa: one as a control sample, two to study the effect of column size, and the last two to study the effect of punching reinforcement. Comparing the results with the design codes showed that ACI-318 is more accurate with an average deviation of about 5%, while EC2 is more conservative with an average deviation of about 20%. Besides that, punching reinforcement reduces the size of the punching wedge by increasing the crack angle to 28° instead of 22° for slabs without punching reinforcement. Also, the results assure that both ductility and stiffness are enhanced with the increased column dimensions and punching reinforcement ratio. Doi: 10.28991/CEJ-2023-09-03-06 Full Text: PDF
Fiber reinforced polymers (FRP) have been considered to be the alternative material to steel in reinforced concrete structures (RC) with the advantages of corrosion resistance, non-conductivity, and high strength-to-weight ratio. FRP-RC beam is featured with higher deformability and larger crack width. However, there is no recognizable ductility in FRP-RC members. Due to the lack of the ductility of FRP-RC beam, it was suggested using hybrid reinforcement of steel and FRP to achieve a preferable strength and ductility. The flexural behavior of the concrete beams reinforced with hybrid reinforcement was investigated through series of six continuous beams. The positive moment GFRP reinforcement ratios of 0.75% and 1.25% were used and the steel reinforcement ratios were ranged to determine the optimum percentage to work efficiently with GFRP. The experimental results showed that increasing GFRP positive moment reinforcement ratio to be more than 1.4 [Formula: see text] increased the flexural capacity of the section but with less ductile behavior. However, increasing the steel positive moment reinforcement ratio leaded to the increase of both the flexural capacity and the ductile behavior in a condition that the steel positive moment reinforcement ratio was [Formula: see text]. It was shown that the flexural capacity predication of the hybrid section using the semi brittle elastic material method to present the de-bonding of moment that occurred at the failure stage had a good accuracy with the experimental results.
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