Question:

A composite column is constructed by combining a concrete core with a steel outer shell. The

dimensions and material properties of the column are as follows:

Concrete core: Diameter $=200mm,$ Height $=3m$

Steel shell: Outer diameter $=300mm,$ Thickness $=5mm$

Young's modulus of concrete, $E_c=30$GPa

Young's modulus of steel, $E_s=210$GPa

Concrete core compressive strength $=25$MPa

Yield strength of steel $=250$MPa

Assume the column is pinned at both ends and the concrete core and steel shell are perfectly

bonded. Calculate the critical buckling load for the composite column using the following formula:

Calculate the effective moment of inertia for the composite column. This can be approximated

as:

$I_{\text{e}\text{f}\text{f}}=I_c+I_s$