الفهرس 
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Abstract
In high rise buildings, a combination of reinforced concrete flat slabs and composite columns is becoming increasingly common and leads to very economic structures. where composite columns with small dimensions are used, often the resistance to punching shear is governed by the flat slab thickness. In order to avoid localized thickening, additional reinforcement systems with double headed studs are often used. Another possibility is the use of shear heads integrated in the flat slab.This study presented a proposal for a new reinforcing system to improve punching shear resistance of composite column-flat slab connections. Results on thirteen specimens tested under vertical static loading are presented. The influence of the slab thickness and the steel system characteristics was considered. In addition, a non-linear finite elements analysis was carried out using ANSYS code. The key parameters namely the concrete compressive strength, steel reinforcement yield strength, column rectangularity ratio, slab rectangularity ratio, reinforcement steel ratio, and steel system characteristics were investigated through a parametric study adopting NLFEA.Test results revealed enhancement in the failure load ranging between 2.53% and 33.5% for the specimens provided with the suggested reinforcing system. In general, the punching shear resistance increased by increasing the reinforcing angles length, while changing the steel section shape inside the composite column had no significant effect on the failure load.The following is a brief description of the contents of this thesis:Chapter 1 presents an introduction including main objectives and research significance.Chapter 2 provides a literature review of previous experimental and numerical works on punching shear of flat slabs supported on both composite and reinforced concrete columns.Chapter 3 describes in details the experimental work.Chapter 4 presents discussions on the results obtained from the experimental work.5 Chapter presents the elements adopted in the finite elements analysis. Chapter 6 develops the numerical models capable to represent the experimental results and presents comparisons between the experimental results with the predicted ones.Chapter 7 presents the numerical parametric study conducted to investigate different factors affecting the behavior of composite column- flat slab connections under static loading.Chapter 8 gives the main conclusions, as well as suggestions for further research work.