Question $1$:

A square hollow structural section has been filled and encased in concrete as illustrated below. If an

axial compressive force of $900kN$ is applied on the composite column,

Assume

$25\%$ of load is carried by the steel

and $75\%$ carried by the concrete.

ESTEEL $=200000$MPa,

ECONC $=25000$MPa

Compute the following:

The minimum thickness of the

steel section $($t$)$ in mm

The normal stresses in the concrete

in Mpa

The normal stresses in the steel in

$$

The change in length in the column in mm