Experimental study of octagonal steel columns filled with plain and fiber concrete under the influence of compressive axial load with eccentricity

Abstract

In recent years, Concrete Filled Tube (CFT) columns have been very much taken into consideration due to the many advantages of the instrument. In experimental studies, the focus has been on compressive loading. Although in many cases the eccentric loading (the presence of a bending moment) has also been investigated, further research is needed in this regard. Therefore, in this study, the steel columns filled with concrete with a regular octagonal cross section were studied under the influence of pressure axial load with eccentricity. The parameters studied in this study include bearing capacity, coefficient of ductility and energy absorption. To test and compare the stated parameters, specimens of 150 cm height, which were filled with plain concrete and fiber reinforced concrete were tested. The compressive axial load has been applied to the specimens by the eccentricity of 50, 100 and 150 mm. The results show that at pure compressive loading, the increase in concrete core capacity increases the load bearing capacity of the specimens so that by increasing the concrete compressive strength by 50%, the bearing capacity of the cross section increases by about 15%. Also, based on the results, the average ductility coefficient for specimens was 7.4, and it seems that this value is independent of the type of loading. The use of concrete with intermediate grade resistance can increase the energy absorbed. However, according to the results, it seems that by increasing the bending moment the positive effects of the concrete core are greatly reduced.