Improving Punching Shear in Flat Slab by Replacing Punching Shear Reinforcement by Ultrahigh Performance Concrete

Abstract

Extensive studies have focussed on the issue of the failure of punching shear in flat slabs and ways to strengthen it internally, externally and the importance of this structure (flat slab), and the danger of punching shear failure in the areas of connection of the column - slab. Therefore, this study was based on strengthening the bearing capacity of the flat slab to failure of punching shear with high-performance concrete (UHPC); because it is expensive, so it is not feasible to use it for the whole slab. Therefore, the aim of the study was to replace reinforcement punching shear with UHPC and to determine its optimal use in the shear area. Six samples of flat slabs reinforced with maximum flexural steel loaded with a column in the middle, four forms of UHPC casting instead of shear reinforcement and at two different depths were used. The results showed an improvement in the punching shear strength of the sample cast with UHPC instead of punching shear reinforcement (ACI 318-19) and with all thickness of the slab, it to arrived twice compared to reference sample (NSC) with reinfored flexural steel only. This is the perfect application for the UHPC. It was also noted that casting UHPC with half the thickness of the slab does not give good results compared to those casting with all thicknesses, despite doubling the distance of the UHPC from all faces of the column; but it changes the failure pattern and keeps it away from the danger areas near the unwanted columns.