Punching shear is the most common failure mechanism of slabs that are supported directly on columns. The slab–column connection is always vulnerable to critical punching shear; thus, it is necessary to investigate the effect of various parameters on the punching shear behavior of the flat slabs. This work presents an experimental study to evaluate the effect of the level of prestressing force and layout of the strands on the punching shear behavior of the slab–column connection in terms of the maximum load, deflection, stiffness, ductility, and the absorbed energy. Five square post-tension flat slabs (2000 mm × 2000 mm) with 150 mm thickness were tested. Increasing the prestressing force increased the maximum load and the ductility with a delay in damage in the case of uniformly distributed strands. Additionally, the banded layout of the post-tensioning strands significantly increased the punching shear capacity of the post-tensioned flat slabs at all levels of prestressing. The influence of the layout of the strands on the flat slab ductility is clearly visible in cases of high prestressing force as the ductility decreases in cases with distributed strands when compared to the same flat slabs with banded strands. Finally, the predicted values of the ultimate load of the punching shear using different codes, including the Egyptian Code of Practice (ECP-203), the American Building code (ACI-318), the CEB-FIP Model code and the Euro code, are compared to the experimental values of the ultimate punching shear strength of the post-tensioned and non-post-tensioned flat slabs.

Self-compacting concrete (SCC) is one of the most recent high-performance concrete innovations. The behavior of self-compacted concrete deep beams reinforced with polypropylene fibers herein investigated. Within an experimental program comprising thirteen simply supported beams tested to failure. The parameters in perspective are polypropylene fiber ratios (0.0, 0.30, 0.60, and 0.90 %), vertical web reinforcement, and horizontal web reinforcement. Mid-span deflection, cracks, and strains are measured for each specimen. According to the test results, the polypropylene fibers improved the cracking load, ultimate capacity, displacement, and energy absorption of the tested SCC deep beams. A polypropylene fiber content of 0.90 % resulted in the most significant improvement as regards the performance of deep beams. The improvement in ultimate capacity reached a 30% magnitude compared to specimen B1. Test results showed that both vertical and horizontal web reinforcement are effective in enhancing the shear capacity of SCC deep beams. The test results were compared with the ACI design method to show the impact of web reinforcement ratio on deep beam load capacity.