Concrete filled steel tube columns (CFST) are a kind of composite columns according to advantages of CFST relative to reinforced concrete and steel columns. Use of these materials is common in recent years especially in high buildings, unnecessary of moulding, high ductility, proportionate resistance with low volume, economical, low deformation relative to steel columns are among advantages. In these columns, development of full load bearing capacity depends on bond strength between steel and concrete, local buckling of steel encasing, ratio of side dimension of the column to steel thickness, D/t, length to dimension ratio, L/D and finally the shape of column.
In this paper, effective parameters on CFST columns behavior are investigated experimentally by testing specimens in laboratory. For this experimental research, twelve specimens loaded axially with enhancing cyclic lateral load. The results of experimental investigation are compared with regulation relations and proposal analytical relation of some of the researchers.