Question 18.P.9: The jib crane shown in Figure P18.9 has a lifting gear with ...
The jib crane shown in Figure P18.9 has a lifting gear with an electromagnet weighing 5 \mathrm{kN} attached to its tip at C. It is lifting iron scrap weighing another 5 \mathrm{kN}. Using three finite elements, \mathrm{AB}, \mathrm{BC}, and \mathrm{BD} obtain the deflection under the load and the maximum stress in the arm ABC. Given, area of the strut \mathrm{BD}, A_{s}=200 \mathrm{~mm}^{2}, cross-sectional area of arm \mathrm{ABC}, A_{b}=1,240 \mathrm{~mm}^{2}, cross-sectional moment of inertia of \mathrm{ABC}, I_{b}=7.5 \times 10^{6} \mathrm{~mm}^{4}, depth of section of \operatorname{arm} \mathrm{ABC}, d=200 \mathrm{~mm}, and E=200,000 \mathrm{~N} / \mathrm{mm}^{2}

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The tip deflection is -12.40 \mathrm{~mm}.
The largest stress in arm \mathrm{ABC} occurs in element \mathrm{AB} at \mathrm{B}. It is compressive stress at the bottom of the section and is 154.1 \mathrm{MPa}.