The ultimate strength of double short composite columns under concentric loads

Muthanna Journal of Engineering and Technology

Volume (3), Issue (1), Year (30 December 2014), Pages (11-24)


Research Article By:

Ragheed Fatehi Makki

Corresponding author E-mail:


No-Fine concrete filled double steel tube columns (CFDST) are being increasingly used for structural applications. It has been used for submerged tube tunnels, nuclear containment, liquid and gas retaining structures, vessels under external pressure in very deep water and for compression members in offshore construction, this is due to the aesthetic appearance, ease of maintenance and simple of construction. The (CFDST) columns also have excellent resistance to seismic loads and fire. This paper comprises of an experimental study on the structural behavior of double steel tubular columns filled with No-Fine concrete under axial load. Eight samples of double steel circular tubes with different diameters for the inner and outer tubes are used, with different slenderness ratios (L/r), different ultimate strengths of No-Fine concrete (fc′). Also two cases are study for (CFDST) samples first with hollow inner tube and second with completely filled inner and outer tubes with No-Fine concrete.
The experimental results show that the effect of height (the slenderness (L/r) ratio) on the ultimate strength of CFDST columns will have a reverse relation. While the effect of uniaxial compressive strength (fc′) and the effect of fully filling the core of internal tube on the ultimate strength of CFDST columns will have an increase relation.

Keywords: No-fine concrete, compression members, concrete filled double steel tubes (CFDST).

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