The advantage of concrete-encased composite structural members is that the concrete used for covering a structural steel not only increases its strength, but also improves ductility. In this paper, experiments on shear strength of the concrete-encased composite column were performed to investigate the effect of confinement by transverse reinforcements, mechanical interlock by holes, and shear connectors. Confinement, mechanical interlock and stud connectors increased the shear strength effectively to secure a composite action of SRC columns. Seven concrete-encased composite specimens were fabricated. The cross-sections of these specimens are composed of concrete-encased H-shaped structural steel columns and a concrete-encased circular tube with partial in-filled concrete. Through the static test, it was evaluated the strength and ductility of SRC composite specimens. The specimens were comprised of structural steel ratio under 2%. The member strengths of the specimens are calculated based on the Eurocode-4, ACI318 code and AISC-LRFD specification. Test results are compared with the P-M interaction curves based on the Eurocode-4, ACI318 code and AISC-LRFD specification. The Eurocode-4 and ACI318 approach generally give closer predictions than AISC-LRFD does. It was concluded that structural capacities of concrete-encased composite columns were excellent in bending strength and ductility. Especially, the comparison results revealed that the concrete-encased circular steel tube column showed the best performance in the structural capacities.
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