INTERFACE SHEAR DEMAND AND DESIGN OF PARTIALLY CONCRETE-FILLED STEEL TUBULAR COLUMNS WITH TRANSVERSE DIAPHRAGMS

A partially concrete-filled steel tubular (CFST) column is formed by partially filling a steel hollow section (SHS) with concrete, its interface shear demand between the infilled concrete and steel tube is important in design but not usually considered. In this work, a refined finite element (FE) model of circular partially CFST columns with transverse diaphragms was established, followed by parameter analysis of the behavior under the combined axial compression and lateral loads. The main variables included the concrete filling ratio, axial compression ratio, diameter-to-thickness ratio of steel tubes, section size, aspect ratio, and material strength. The results indicate that the optimal filling ratio increases with the axial compression ratio, diameter-to-thickness ratio, and concrete strength, but decreases with the steel strength. Then, calculation methods for the optimal filling ratio, predicting the load capacity of transverse diaphragms, and the interface shear demand between the steel tube and infilled concrete were proposed. Finally, a design procedure for partially CFST columns with transverse diaphragms was proposed.