The present study investigates the behavior of steel fiber reinforced concrete filled steel box columns (SFRCFSBC) targeting to enhance their strength. A nonlinear finite element model using ANSYS program has been developed to investigate the structural behavior of the inspected columns. The results obtained from that model has been compared with those calculated using Euro code (EC4), AISC/LRFD (2005) and the Egyptian Code of Practice for Steel Construction (ECPSC/LRFD 2007). The comparison indicated that the results of the model have been evaluated to an acceptable limit of accuracy. A parametric study was carried out to investigate the effect of wall thickness, column slenderness and percentage of steel fiber in concrete on the ultimate strength of composite columns. Confinement of the concrete core provided by the steel case was also investigated. It can be concluded from the results that a considerable increase in compressive and flexural strength may be gained by increasing the steel fiber percentage up to 4%. The highest rate of increase in strength for long columns was about 20% by using steel fiber percentage between 0.5% and 1.0%, while for short and medium columns was about 10% by using steel fiber percentage between 1% and 2%.
