고체역학 (Gere) — Stresses in Beams (Advanced Topics): Problem 6.3-3

6.3-3 A wood beam 200 mm wide and 300 mm deep (nominal dimensions) is reinforced on top and bottom by 12 mm-thick steel plates (see figure part a). (a) Find the allowable bending moment \(M_{\text{max}}\) about the \(z\) axis if the allowable stress in the wood is 7 MPa and in the steel is 120 MPa. (Assume that the ratio of the moduli of elasticity of steel and wood is 20.) (b) Compare the moment capacity of the beam in part a with that shown in the figure part b which has two 100 mm \(\times\) 300 mm joists (nominal dimensions) attached to a 6 mm \(\times\) 280 mm steel plate.