Strength gains of the axially and laterally loaded composite columns based on the concrete confinements provided by steel cores encased in structural concrete

Most of the design codes for the composite columns including American Concrete Institute do not account for the concrete confinements offered by the steel cores encased in the concrete section. However, the flexural capacities of the axially and laterally loaded composite columns were substantially underestimated as the axial load increases if the concrete confinement provided by a steel core is not considered. The aim of this study was to identify the structural gains of the composite columns with the cross-, H- and T-shaped steel cores encased in the concrete when the concrete confinement provided by the steel cores is taken into consideration. The formulation of the flexural strength considering the confining effects provided by the transverse reinforcements and cross-shaped steel cores for the maximum load limit state was presented with a 50% axial load of the nominal column capacity. The formulation for an ultimate load limit state with a 40% axial load of the nominal column capacity is listed in the Appendix. The design charts were presented for the strain ranges between 0.001 and 0.01, leading to gaining the strengths of the composite columns that have been lost when the confining effects provided by the steel cores were ignored