9520280 Azizinamini Composite construction consisting of concrete filled tube (CFT) columns with relatively thin-walled steel tubes, has been used in building construction in U.S. and Far East. In general, in this type of construction, steel beams are framed to these columns at each floor level. Detail and design criteria for connecting steel beams to CFT columns are almost non existent. The overall objectives of this project are to develop an economical connection detail for connecting steel beams to CFT columns and provide accompanying design provisions. The focus of this investigation is to develop the Fully Restrained (FR) type steel connection detail for CFT columns for buildings ranging from 10 to 20 stories high and for seismic performance categories D and E defined per "NEHRP Recommended Provisions for the Development of Seismic Regulations for New Buildings". The connection detail to be selected and design provisions to be developed will give consideration to the following issues: a) level of ductility, b) economy and constructability, c) avoiding over stressing the steel shell portion of the CFI columns, d) preventing damage to the joint region of the column by moving the location of the plastic hinge to some safe distance away from the column face, e) taking advantage of composite action between the concrete slab and the steel beam. At least two structural configurations will be investigated. static and dynamic linear and inelastic analyses considering different ground motions will be conducted to establish a level of ductility required for the connection. Both finite element analysis and experimental study will be carried out to develop the connection detail and design provisions. Results of this research should fulfill this technology gap and expedite acceptance of composite structures in construction industry. This is a project supported under NSF 94- 154 a CIS Solicitation "Research on Composite and Hybrid Structu res".