Experimental and numerical investigation on punching behavior of ultra-high performance concrete flat slabs

In this paper, punching shear behavior of Ultra-High Performance Concrete (UHPC) was investigated experimentally and numerically. In this study, six 1350 * 1350 * 80 mm flat slabs with extended 200 mm column stubs above the slabs were constructed to study the effect of the increased strength of UHPC and its ductility with different concrete mix ratios and different column aspect ratios. All specimens contained steel fibers which increased slabs ductile behavior and shared directly in increasing punching shear capacity of the examined specimens. Numerical investigation was performed as nonlinear finite element analysis adopting ABAQUS software using concrete damaged plasticity model (CDPM), ABAQUS/Explicit. Compression and tensile behaviors of concrete were modeled by Hognestad Parabola and Bilinear tensile stress versus crack width respectively. The average strength of test specimens ranged between 164 MPa and 193 MPa in compression and 9.6 MPa to 13.1 MPa in tension. In this study, analysis parameters were concrete strength, column aspect ratio, column shape, and flexural reinforcement ratio. The results showed an increase in punching shear capacity in the six specimens ranged between 32% and a 20.8% relative to ACI 318-19 punching strength formula and Euro code EN1990.2012 formula, respectively.