Impact of Duct Position on Behavior of High-Strength Reinforced Concrete Flat Slab

Abstract

Structural and architectural designers consider flat floors as preferable slab systems in medium-rise buildings. The ability of this slab system to incorporating ducts enhancing its functional efficiency. However, incorporated ducts impacting flow of the interior forces and reducing the slab stiffness, most notably when the ducts pass near columns. İn addition to brittle nature of high-strength concrete. Therefore, the shear resistance significantly reduced and the risk of brittle punching failure highly increased. Thus, the main goal was to evaluate the behavior of the punching shear for flat slabs composed of high-strength concrete that incorporates built-in ducts. For this purpose, six two-way slab specimens were fabricated with a duct, and one solid specimen served as a control specimen. Two main parameters were studied: the distance of the duct opening to the face of the column over horizontal distances of 0, 50, and 100 mm for two types of opening (30 × 100 mm) and (50 × 100 mm), and the duct height with two values of 30 and 50 mm. The outcomes indicate that shear behavior was negatively affected as the duct moved closer to the column face and as duct height increased. The ultimate load capacity decreased most at the column face, by up to 42.1%. Serviceability worsened in both parameters of the study, particularly as the duct was closer to the column face and the duct height increased. Additionally, duct deflection increased significantly, and specimens often failed to meet the service load requirements. The toughness generally declined with both closer proximity and greater duct height. The most severe reductions occurred at the 0 mm position, where toughness dropped by over 50% in both 30 mm and 50 mm duct height specimens. All slab specimens, including a solid control specimen, exhibited the exact failure mechanism, known as punching failure.