Concrete filled double circular steel tube (CFDCST) stub columns

Concrete filled steel tube (CFST) columns are deployed as the main load carrying members in high performance structures as they integrate the beneficial properties of constituent materials. In recent years, there has been an increased interest in the literature to further improve the performance of the CFST columns. The work presented in this paper, for the first time, investigates through experimental and statistical analyses the potential of concrete filled double circular steel tube (CFDCST) columns to improve the efficiency of the composite members. Experimental results validated the capability of CFDCST columns in performing high strength, stiffness and ductility properties which can be utilized in challenging design scenarios. Employed statistical analysis characterized the impact of parameters on the collapse performance of the CFDCST column. To establish whether the configuration of CFDCST members could be used in repairing process of highly stressed and deformed CFST columns, a further set of experimental work was undertaken. Deformed CFST stub columns were centred in a larger diameter steel tube and the region between the existing CFST column and the larger diameter tube was filled with concrete. Repaired forms of the columns were tested and the performances were compared against the performances of the CFDCST counterparts. Results show that it is possible to employ such a repairing, since the repaired CFST columns exhibit performances very close to that of CFDCST counterparts. The findings are quite revealing for design purposes and have important implications for advancing the knowledge on composite compression members.