Abstract
Buckling strength was experimentally investigated for the two types of mortar filled steel tubular columns, called bonded type and unbonded type. The difference between both types is in the loading manner and in the bond condition between the steel tube and the encased concrete. The tests were done on short and long composite columns with various slenderness ratio to find out the relationship between compressive strength and confinement effect for both types of long composite columns. Moreover a proposal for the prediction of ultimate strength were tried on the both-type mortar filled steel tubular long columns under axial compression. The results shows that there exists a significant difference in the stresses in steel tube depending on the bond condition, though the strength of the unbonded type is slightly larger than that of the bonded type.
