Giakoumelis and Lam 2004

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This paper presents the results of tests on circular CFT columns. The effect of bond between the steel tube and concrete core for a range of concrete strengths was examined. The experimental results were compared to European, American, and Australian design codes.

Experimental Study, Results, and Discussion

The main test parameters were concrete strength, steel tube thickness, and bond between the concrete core and steel tube (greased or non-greased). The diameter of the steel tube and length of the column remained constant for all tests, with an L/D ratio of 2.6. Three different concrete strengths were used (4.3 ksi, 8.6 ksi, and 14.3 ksi). The nominal yield strength of the steel was 50 ksi, the measured value was obtained from compressive tests on hollow tubes. The columns were capped on both ends to distribute the load uniformly over the steel and concrete.

It was observed that for high strength columns, the peak load was obtained with small displacement, whereas the for normal strength columns the peak load was obtained with large displacements. It was further observed that the difference between the greased and non-greased specimens varied with the compressive strength of the concrete. For normal strength concrete the load displacement curves for the two were nearly identical. For medium strength concrete, at ultimate load, the greased and non-greased achieved the same capacity, but the elastic capacity was higher for the non-greased specimen. For high-strength concrete a significant variation between greased and non-greased specimens was noted.

The experimental results were compared to Eurocode 4, ACI 318-95 and Australian Standards AS3600 & AS4100. While all methods provided conservative results, the Eurocode 4 method provided the most accurate results. The authors noted that neither the ACI nor the Australian Standards method take into consideration the concrete confinement. Thus a constant coefficient was proposed to account for the confining effects.

References

Giakoumelis, G. and Lam, D. (2003). “Axial Capacity of Circular Concrete-Filled Tube Columns,” Journal of Constructional Steel Research, Vol. 60, pp. 1049-1068.