Gere & Goodno — Stresses in Beams (Advanced Topics): Problem 6.3-11

6.3-11 A beam is constructed of two angle sections, each L 120 × 80 × 12, that reinforce a 50 mm × 200 mm (actual dimensions) wood plank (see the cross section shown in the figure). The modulus of elasticity for the wood is \(E_w = 8 \text{ GPa}\) and for the steel is \(E_s = 200 \text{ GPa}\). Find the allowable bending moment \(M_{\text{allow}}\) for the beam if the allowable stress in the wood is \(\sigma_w = 10 \text{ MPa}\) and in the steel is \(\sigma_s = 110 \text{ MPa}\). Note: Disregard the weight of the beam, and see Table F-5 of Appendix F for the dimensions and properties of the angles.