$$ \begin{array}{l}{\text { Data: } b=30 m m, t=15 m m, L=2.8 m, P=58 \mathrm{kN}, E=2.1 \times 10^{3} \mathrm{N} / \mathrm{mm}^{2},} \ {\mu=0.30} \ {\text { Find: } e_{v}, \delta v} \ {\sigma=\frac{P}{A}=\frac{58 \times 10^{3}}{30 \times 15}=128.88 \mathrm{N} / \mathrm{mm}^{2}}\end{array} $$ $$ \begin{array}{l}{\mathrm{e}_{\mathrm{v}}=\frac{\sigma}{\mathrm{E}}(1-2 \mu)} \ {\mathrm{e}_{\mathrm{v}}=\frac{128.88}{2.1 \times 10^{3}} \times(1-2 \times 0.30)} \ {\mathrm{e}_{\mathrm{v}}=24.54 \times 10^{-4}}\end{array} $$ $$ \begin{array}{l}{\text { To find } \delta_{v}} \ {\mathrm{e}_{v}=\frac{\delta_{v}}{V}} \ {\delta_{v}=e_{v} \times V} \ {\delta_{v}=2.454 \times 10^{4} \times 2800 \times 30 \times 15} \ {\delta_{v}=309.204 \mathrm{mm}^{3}}\end{array} $$