Construction of concrete filled UHPFRC tubes (Ultra High Performance FiberReinforced Concrete) results in systems with ductile characteristics, high stiffness andstrength. It also makes optimum use of materials based on their mechanical propertiesand resistance to corrosive environments. One such application is demonstrated inconcrete filled hybrid UHPFRC tubes. It is named Hybrid Composite Column (HCC)for the fact that it contains an additional wire mesh layer into the tube. The hybridUHPFRC tube provides the necessary additional longitudinal and transversereinforcement, as well as a permanent formwork for the concrete core. The concretecore contributes to the overall stability and stiffness of the composite system. Comparedto a conventional RC column, construction time is reduced because there are noformworks in sites, and compared to a segmental PC column, lifting load is significantlyreduced because of a void section (or empty core). The present study is an experimentalinvestigation of HCC as structural column. The main focus of this research is on theuniaxial compression behavior of concrete confined with hybrid UHPFRC with1.5%and2%fiber volume (Vf) along with1.26%and2.52%transverse steel ratio (ρsv%)for core concrete. For the better confinement effect, the bond between the concrete coreand the tube is necessary throughout the length of the column. To achieve this, thethreaded bars were embeded through the columns as shear connectors.Size effect on strength of quasi brittle materials like concrete, ice and rock, in theliterature often referred as geo materials, has been an issue of discussion over the lastthree decades. Size effect investigations have been carried out either by experiments orthrough numerical simulations. Usually mechanical properties of specimens of differentsizes are investigated.The second part of this research has focused on the influences of specimen size ontensile behavior of an ultra high performance fiber reinforced concrete (UHPFRC). Inthis study, the Size Effect phenomenon was investigated under uniaxial tension for bothwire meshed and non wire meshed notched dog bone specimens. This study wasconducted by performing four uniaxial loading tests on four different specimens.It was found that under given experimental conditions, the nominal strengthstrongly depended on the specimen size. The test results indicate that, there is a stronginfluence in mechanical properties due to variation of the testing specimens. Forwire meshed dog bone, it was found that the mechanical behaviour of UHPFRC wasimproved by the presence of wire mesh. Tensile strength was improved by21.8%,cracking strength by18.3%and modulus of elasticity by77.1%