A typical floor layout for a proposed building is provided. The bottom storey of the ten$-$storey building has a height of $4\mathrm{.}5$m$,$ while the remaining floors have heights of $3\mathrm{.}2$ m$.$ The typical column centre to$-$centre spacing is $5\mathrm{.}6$ m in the N$-$S direction, and $6\mathrm{.}8$ m in the E$-$W direction. A preliminary design has suggested that the square columns will have dimensions of $350$ mm x $350$ mm and will have the same width as the edge beams shown. All beams are assumed to be stiff and geotechnical reports have identified the building location as Site Class. Clearly state any assumptions. Do not redistribute bending moments. Use a design concrete strength f$$c of $30$ MPa. The slab should be designed for a uniform live load of $4\mathrm{.}8$kPa and a superimposed dead load of $1\mathrm{.}5$ kPa. The design snow load on the roof is $2\mathrm{.}4$ kPa.

Design column B$4$ to resist the combined effects of axial load and Jmomentsfor the bottom storey. Consider two possible load cases: $1)$ unbalanced moments about one axis only with maximum axial loading Mun $=58\mathrm{.}68$kn$*$m and $2)$ biaxial bending resulting from unbalanced moments about both axes and axial load reduced by $25\%.$Consider gravity loads only, and check whether slenderness effects should be taken into account. Assume that the base of the column is fixed $($stiff$)$ and the top is elastic.