Composite Frame Systems
Portal frames composed of rectangular CFT columns and wide-flange steel beams have been tested at several locations (Matsui, 1986; Kawaguchi et al., 2002), and stable hysteresis loops have been obtained. The concrete infill increased the local buckling strength of the member, and the concrete core continued to resist loads even after local buckling of the steel. This fact improved the strength of the frames relative to frames having hollow tube beam-columns. Fracture at the connections or extensive local buckling at the column ends were among the typical failure modes.