Investigation of punching performance in slab-column connection elements produced from self-compacting hybrid fiber reinforced concrete as experimental and statistical

Flat slab systems have important advantages such as efficient use of building areas, obtaining a flat ceiling as well as ease of formwork and concrete placement and thus resulting in reduction at construction costs. However, in this slab system, there may also be some problems, such as excessive slab thickness and the risk of sudden collapse of the structure throughout its service life. Therefore, in this thesis study, to increase the punching performance of slab-column connection elements a total of five self-compacting concrete (SCC) mixtures were designed, named control, single, binary and ternary fiber reinforced mixtures. Three types fibers having different types (steel and synthetic), aspect ratio and sizes (macro and micro) were used in SCC mixtures produced to examine the effect of fiber combination on punching performance. Moreover, the fresh and hardened properties of SCC mixtures were determined. Then, full-scale specimens were produced and tested to examine the punching performance of slab-column connection elements with only fiber (single and hybrid) or fiber and different punching reinforcement (closed stirrup and shear stud). Finally, it was determined that the addition of polypropylene (PP) fiber into hybrid fiber reinforced SCC negatively affected the workability compared to micro steel fiber reinforcement. However, hybrid fiber reinforcement positively affected the hardened properties of SCC while especially ternary hybrid fiber reinforcement had the best performance. Also, it was determined that hybrid fiber reinforcement is an effective punching measure to increase the punching performance of slab-column connection elements. In addition to all these, empirical equations have been developed to predict the punching strength of slab-column connection elements produced from hybrid fiber reinforced SCC, and suggestions have been made for the punching strength design expressions in different codes.