Research Projects

Concrete filled double-skin tubular columns (CFDST) are a new generation of optimized steel-concrete-steel composite columns with concrete sandwiched between inner and outer steel tubes. However, the low thermal conductivity of concrete can negatively affect the fire resistance of CFDST columns, as it decelerates heat transfer from outer tubes to inner tubes, leading to heat accumulation in the outer steel tube and rapid degradation of strength in the steel tubes. Traditional unstiffened DSTCs have shown local buckling deformations of inner steel tubes at elevated temperatures, negatively affecting their structural performance. This study builds on previous research by investigating the influence of stiffeners in DSTCs of multiple cross-sectional shapes subjected to non-uniform heating. Previous studies have not quantified the influence of stiffeners on confined concrete behavior of stiffened DSTCs under temperature variations. Additionally, axial load-bearing equations are not available in current design specifications or literature for estimating the axial load-carrying capacity of stiffened DSTCs. To address this, a modern variation of DSTCs with steel-rib stiffeners on the outer surface of the inner steel tube or interior surface of the outer steel tube will be developed, referred to as Stiffened DSTC. The research aims to investigate the confined concrete behavior of stiffened DSTCs of multiple cross-sectional shapes under varying temperatures.