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Experimental and numerical investigation on the effectiveness of novel truss-shaped punching shear reinforcement in reinforced concrete flat slab

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Date
2023-06-01
Authors
Shamshinar Binti Salehuddin
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The use of reinforced concrete flat slabs in building construction increases the floor-to-floor clearance, expedites construction work, and offers aesthetically rewarding features. However, a flat slab structure can be subjected to punching shear failure that is potentially catastrophic. Many studies have been conducted to enhance the punching shear capacity of flat slabs but some of these proposed punching shear reinforcements were complicated to be installed and costly. As such, this research is conducted with the aim to evaluate the effectiveness of a novel and simple truss-shaped punching shear reinforcement that is placed in a 1200 mm × 1200 mm × 175 mm thick flat slab specimen with concrete grade of 26 N/mm2. Three types of truss-shaped punching shear reinforcement were proposed namely plain 2-D box truss (Type 1), Howe/Pratt truss (Type 2) and multiple inclined members (Type 3). The experimental results showed that the average punching shear capacity were recorded to be 140.026 kN, 150.818 kN, 161.430 kN and 170.089 kN for Control, FS1, FS2 and FS3 specimens, respectively. As such, the use of truss-shaped punching shear reinforcement increased the punching shear capacity in the range of 7.71% to 21.47%. The highest punching shear capacity showed by FS3 can be associated to the presence of more inclined members that are capable to intercept more shear cracks and manifested via the highest energy absorption capacity compared to other specimens. In addition, the validation exercise using ANSYS software package and coupled with Hognested Concrete Model was able to predict the load-deflection curve with good agreement. The difference with the experimental data in terms of the punching shear capacity and the corresponding deflection was calculated to be less than 4% for all cases. The parametric study revealed that replacing the size of the flexural reinforcement, extending the truss-shaped punching shear reinforcement and adding more inclined members were able to further enhanced the ultimate load but were not compatible with the total use of the reinforcement. By combining the results from the parametric study with the experimental data, it can be concluded that punching shear reinforcement Type 3 was found to be most effective to be used compared to other types of punching shear reinforcement.
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