WITH STIFFENED SQUARE SECTIONS

A scheme called “tie-bar stiffening ” was proposed for improving the performance of square concrete-filled steel tubes (CFTs) with thin-walled tubes. Axial load test and combined axial-and-flexural load test have both been conducted to circular, unstiffened and tie-bar-stiffened square CFT beam-columns. It is observed that the axial load strength and ductility of square CFT columns can be enhanced by the proposed stiffening scheme, and the spacing instead of diameter of the tie bars is the dominant factor to the scheme’s effectiveness Stiffened square CFT beam-columns have a better flexural behavior, in terms of moment capacity and curvature ductility, than unstiffened ones. Such improvement in flexural behavior is more significant as the beam-column is subject to higher axial load