고체역학 (Gere) — Stresses in Beams (Basic Topics): Problem 5.6-17

5.6-17 A beam having a cross section in the form of an unsymmetric wide-flange shape (see figure) is subjected to a negative bending moment acting about the $z$ axis. Determine the width $b$ of the top flange in order that the stresses at the top and bottom of the beam will be in the ratio 4:3, respectively. Given dimensions from the figure: Top flange: width $= b$, thickness $= 40\text{ mm}$ Web: thickness $= 30\text{ mm}$, height $= 300\text{ mm}$ Bottom flange: width $= 400\text{ mm}$, thickness $= 40\text{ mm}$ Total beam height $h = 40 + 300 + 40 = 380\text{ mm}$