This project conducts studies in steel-concrete composite structural systems which are becoming more prevalent in building frame construction today. A common type of composite structure is a steel frame with composite primary columns. This combines the advantages of a light-weight, ductile steel frame with the added stiffness of steel-concrete composite columns to control lateral drift. The focus of this research is on the performance of connections to concrete-filled tube columns. An inelastic seismic analysis of building frames, an inelastic finite element analysis of the specific details and experimentation of critical connections are carried out. The current limited practices of these composite elements and provide guidelines for the safe and economical design of connection details are assessed. Connections with elements that penetrate the steel tube and steel-to-steel connections to the exterior of the tube wall are investigated. Several detailing issues are considered, including: embedment length of members without shear connectors, required thickness of the tube wall in the area of the beam-to-column joint, required vs. available bonding between the steel tube and concrete core, creep and shrinkage of the concrete core, and crushing of the concrete and buckling of the tube wall at the connection. It is expected that results from this research will stimulate wide-spread interest in the design community. Composite construction has many advantages over the more traditional structural systems, and this research will be the first step in making concrete-filled steel tube columns more feasible and practical for future use.
