This paper presented experimental results of 16 CFT specimens
tested under concentric loading. The test results showed that for
columns with concrete filling of high compressive strength, the
maximum load was reached with lower strain in comparison with
the columns filled with ordinary strength concrete.
(a) Considering the same values of concrete strength, the specimens
with L=D D 3 showed a higher increase of load capacity due
to the confinement effect, up to the crushing of the concrete core
and the local buckling of the tube. The specimens with L=D D 10
presented a lower strain, since the global buckling occurred before
the concrete core could develop its full capacity, reducing the radial
deformation of the concrete core and avoiding the mobilization of
the confinement effect of the tube.
(b) The comparative analysis of the standard codes presented
satisfactory results, mainly for the specimens with higher values
of L/D ratio. Both NBR and ANSI/AISC codes showed results 10.7%
and 10.4% below the obtained results, while the ultimate capacities
of the 16 specimens were higher than the ones predicted by the
ANSI/AISC Code.
(c) The results of EC4 and CAN/CSA were not conservative,
despite having lower differences between the predicted and the measured ultimate load results of 2.4% and 2.3% on average,
respectively.
(d) In general, all standard codes showed good agreement
results for columns with higher values of L=D, but for short columns
(L=D D 3) the codes overestimated the increase of load capacity of
CFT columns due to the confinement effect, especially the EC4 and
CAN/CSA codes