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Column is a major Axial load transferring Member in most of the structures. According to the revised seismic codes columns should be have better flexural strength in addition to the Axial load carrying capacity. It is been a major concern in construction industry in previous few years to increase the column strength. Concrete-Filled Double Skin Tubes (CFDST) is one of the latest innovations in Structural engineeringThe CFDST members were first designed for vessels to resist extreme external pressure but due to its various advantages, it has got strong demand and strong potential for using it in bridges, flyovers and high rise buildings. In this study CFDST is analysed using ABAQUS/CAE 6.11-1 and experimentally tested for stress strain and axial shortening.

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Purpose Concrete-filled double skin tube (CFDST) columns are considered one of the most effective steel-concrete composite sections owing to the higher load carrying capacity as compared to its counterpart concrete-filled tube (CFT) columns. This paper aims to numerically investigate the performance of axially loaded, circular CFDST short columns, with the innovative strengthening technique of providing stiffeners in outer tubes. Circular steel hollow sections have been adopted for inner as well as outer tubes, while varying the length of rectangular steel stiffeners, fixed inside the outer tubes only, to check the effect of stiffeners in partially and full-length stiffened CFDST columns. Design/methodology/approach The behaviour of these CFDST columns is investigated numerically by using a verified finite element analysis (FEA) model from the ABAQUS. The behaviour of 20-unstiffened, 80-partially stiffened and 20-full-length stiffened CFDST columns is studied, while varying the strength of steel (fyo = 250–750 MPa) and concrete (30–90 MPa). Findings The FEA results are verified by comparing them with the previous test results. FEA study has exhibited that, there is a 7%–25% and 39%–49% increase in peak-loads in partially stiffened and full-length stiffened CFDST columns, respectively, compared to unstiffened CFDST columns. Originality/value Enhanced strength has been observed in partially stiffened and full-length stiffened CFDST columns as compared to unstiffened CFDST columns. Also, a significant effect of strength of concrete has not been observed as compared to the strength of steel.

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