The thin-walled composite beam section of Example 26.15 carries a vertical shear load of 2kN applied in the plane of the web. Determine the shear flow distribution.
From Ex. 26.15 and Fig. S.26.19 the second moments of area are
\begin{array}{l c r}{{I_{X X}^{\prime}=2.63\times10^{10} \mathrm{Nmm^{2}}}}\\ {{I_{YY}^{\prime}=0.83\times10^{10} \mathrm{Nmm^{2}}}}\\ {{I_{X Y}^{\prime}=1.25\times10^{10} \mathrm{Nmm^{2}}}}\end{array}In this case S_{X}=0,S_{Y}=2\,\mathrm{kN} so that Eq. (26.69) becomes
On the top flange, X=50-s_{1},\,Y=50~\mathrm{mm},\,E_{Z,i}=50~000~\mathrm{N/mm}^{2}. Eq. (i) then becomes
q_{12}=+40.3\times10^{-3}\int_{0}^{s_{1}}\left(50-s_{1}\right)\!\mathrm{d}s_{1}-26.8\times10^{-3}\int_{0}^{s_{1}}\!\mathrm{d}s_{1}which gives
q_{12}=-0.02s_{1}^{2}-1.99s_{1}When s_{1}=50~\mathrm{mm},~q_{2}=-149.8~\mathrm{N/mm}
In the web, X=0,\,Y=50-s_{2},\,E_{Z,i}=\,15\,\,000\,\,\mathrm{N/mm^{2}}. Eq. (i) then becomes
q_{23}=-8.04\times10^{-3}\int_{0}^{s_{2}}(50-s_{2})\mathrm{d}s_{2}-149.8so that
q_{23}=0.40s_{2}+4.02\times10^{-3}s_{2}^{2}-149.8When s_{2}=50~\mathrm{mm},~q_{23}=-159.5~\mathrm{N/mm}