Experimental Investigation on Hexagonal Steel Tubular Columns Filled with Plain and Fiber Reinforced Concrete under Eccentric Compression Load

Due to the advantages of Concrete Filled Tube (CFT), attention to them is increasingly on the rise. In spite of the extensive research done in these sections, in some cases, as in the case of less frequent sections or using different types of concrete, the need for research to complete the design rules and guidelines seems necessary. The present study was conducted with an experimental approach to the study of CFT under Eccentric load. In this study, 8 CFT columns with a hexagonal cross section of 150 cm in length were tested. Concrete used as the core of the samples was plain and fiber concrete. The displacements in two directions been recorded and the force - displacement diagram for all samples has been drawn. Parameters such as bearing capacity, ductility index, energy dissipation and effective hardness have been analyzed and compared. Based on the comparison of the results, it was found that in columns that are only under axial load, the increase in concrete core strength significantly increases the bearing capacity of the specimens, so that an increase of about 50% of the concrete core strength causes an increase of about 20% of the loaded capacity of the specimen; However, by increasing the bending moment, the effect of concrete core resistance is greatly reduced. Also it was found that specimens filled with fiber concrete have greater ability to maintain effective hardness. It also seems that the presence of fibers in concrete affects the ductility and energy dissipation parameters