Question

During construction, field tests were conducted to assess the suitability of the column to
withstand a safe buckling load of 2.5 kN assuming a factor of safety 4 using two different hollow
columns made up of steel and concrete. Both columns have same cross section but varying length
and different support conditions. Steel column of length 3 m having external diameter 40 mm was
tested with one end fixed and the other end hinged, when subjected to a compressive stress of
0.0045 MN/cm2 shortens by 3.6 mm.
If the concrete column was tested under similar loading conditions with one end fixed and other
end free considering modulus of elasticity of concrete equal to 128 GPa, what will be the
corresponding length of the column required? As a design engineer how do you choose the values
for the thickness of both columns and the length of the concrete column? What will be your
interpretations regarding the relationship between the support conditions and the buckling load
based on the test results?

Answer 1