Concrete filled double skin circular tubes : a review

A review of the research conducted on the compressive strength of concrete filled double skin circular tubes (CFDSCT) columns is conducted. Variables of the CFDSCT considered in this review include the concrete strength, steel strength, inner and outer tube diameter, steel thickness and length of the stub columns. Test results show that the composite columns had compressive strengths of up to 41% higher than the sum of the individual strengths of the section. All the outer tubes of these composite columns by failed local buckling. A review of the design equations proposed are presented and discussed. The paper also identifies gaps for further research for these types of columns