research behavior of concrete filled steel tube columns, cfst

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 building, unnecessary of molding, high ductility, proportionate resistance with low volume, economical, low deformation relative to steel columns are among advantages. in this research, effective parameters on cfst columns behavior are investigated experimentally and analytically. for these researches, six speciments of cfst columns with three to one scale are considered. in analytically investigation it is used finite elements method and ansys 10 soft ware, also steel tube and concrete, and stiffeners are modeled with finite elements. for consideration bond strength between steel and concrete it is used contact elements. investigated specimens (experimentally and analytically) are molded as a cantilever. specimens loaded axially with enhancing cyclic lateral load. the enhancing lateral load is using with cyclic lateral displacement in end column. (displacement control) in this research three sets of columns with shape, square, circle and octagonal sections took into account some of them are without stiffeners and some are with stiffeners at whole length or in 30 cm of lower part of the specimens are considered, that effects of column section shape and effects of stiffeners in column behavior are investigated.