Confined concrete-filled tubular columns

This paper presents a study to introduce and experimentally validate an innovative concrete filled steel tubular (CFT) column system, named as confined CFT or CCFT, for improved seismic design of steel and concrete composite structures. Based on fundamental mechanics, the concept is aimed at controlling the focal buckling of the steel tube and confining the concrete in the potential plastic hinge regions of a CFT column. To achieve this, several efficient details of transverse confinement are proposed. In the first phase of the study, carbon-fiber-reinforced plastic as additional confinement of CCFT columns was examined through experimental testing. As demonstrated from the results of axial compression tests and seismic loading tests, the new type of CFT column system can provide excellent seismic performance. The complicated local buckling and confinement mechanisms were examined using a proposed simple analytical model.