Behavior of high-strength concrete-filled circular steel tube beam-columns.

High strength concrete filled tube (HSCFT) columns have been used in several high-rise building projects around the world in the last decade. With very few reported experimental results on the performance of such members, this is clearly an aspect of structural engineering where practice is far ahead of the research. A limited study on circular HSCFT beam-columns, presented in this thesis, was conducted to obtain additional experimental data on the behavior of these structural elements and assess recent design code provisions with regard to circular concrete filled tube (CFT) columns. Three long beam-columns $(L/D=13.5)$ were tested under constant axial compression and incrementally increasing lateral displacement reversals. The level of the axial load was the main parameter investigated in this experiment. In addition, one short column was tested in concentric compression. All specimens had the same cross-sectional geometry to allow for direct comparison. Both strength and deformability issues were addressed. Various aspects of concrete confinement in circular CFTs were analyzed. A comparative study of North American and European design code provisions was carried out. The experimental results were compared with theoretical predictions of strength. (Abstract shortened by UMI.