Concrete filled steel box columns have been extensively used in modern structures and tall buildings due to the enhanced performance of these columns specially the strength and ductility enhancements. The present study will take a further step in that direction through adding additional enhancements and investigating the steel fiber reinforced concrete filled steel box columns. The study will prove that the behavior of these columns will result in enhanced performance comparable to the conventionally concrete filled steel box columns which may cause a reduction in the column size and can consequently contribute to significant economic benefits. A nonlinear finite element model using ANSYS program has been developed in order to investigate the structural behavior of the inspected columns. The results obtained from that model have 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, length of column 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 involved. Width-to-column wall thickness ratios between 20 B/t 40, the length-to-column width ratios of 8 L/B 30, and the internal concrete of nominal unconfined cylinder strength of 30 MPa with steel fiber percentage up to 4% were investigated. It can be concluded from the results that an increase in compressive strength and flexural strength up to 10 % may be gained. It can moreover, be easily demonstrated that the proposed method is the most effective in enhancing the ductility capacity and reducing the construction cost. |
