Comparison of classical, double skin and double section CFST stub columns: Experiments and design formulations

Abstract

With the continuing developments in composite design technology, such as classical Concrete Filled Steel Tubes (CFST), concrete filled double skin tubes and concrete filled double section tubes, understanding the performances of such columns in a comparative way is timely. Although significant amount of literature has been gathered around the themes of concrete filled classical and double skin columns, the number of studies on double section columns is very limited. Nevertheless, in existing research, double section column concept has been proven to be very efficient in providing very high strength, ductility and stiffness. The challenge here is to find a route from concept to design which requires significant amount of comparative experiments on classical, double skin and double section columns. This paper, for the first time, examines the performances of concrete filled classical, double skin and double section stub columns which have practical range of material and geometrical properties. Experimental procedures were undertaken for composite columns with normal and high strength self-compacted concrete. To be able to address the effect of tube configurations, two types of outer and two types of inner steel tubes with different mechanical and geometrical properties were utilized. The experimental program revealed the robust characteristics of double section columns. Furthermore, the modified versions of EC4 and AISC 360–16 formulations were assessed against the test results for design purposes. It is shown here that the modified versions of the prediction methods have the potential to be utilized in field applications for double skin and double section columns.