Concrete filled steel tubular (CFT) columns have become increasingly popular in structural applications. The increased popularity comes from their excellent structural properties such as high strength, high ductility, and large energy absorption capacity. However, a disadvantage feature of CFT-column is its time dependant characteristic by means of creep and shrinkage of inner concrete. The time dependent behavior of CFT-column can cause serious serviceability problems. Therefore, it is necessary to investigate the long-term behavior of CFT-column.
This thesis presents analytical and experimental studies on long-term behavior of CFT-column under a central axial loading. Two loading cases are considered in the research; (1) the load applied only at the inner core concrete of CFT-column and (2) the load applied simultaneously on both concrete and steel tube. Analysis method using the developed bond strength model is proposed and experiments are performed for the two loading cases. Conclusions on long-term properties of CFT-column can be derived from the results.
